Glossary

AAC

Augmentative and Alternative Communication, commonly referred to as AAC, is a term used to describe various methods of communication that can aid those who are unable to use verbal speech to express themselves. AAC is a broad term that encompasses a wide range of communication methods, from gestures and facial expressions to spoken words, typing, and picture-symbol based means of communication^[1].

AAC is not limited to any one tool or method, but rather refers to any tool or method that an individual uses to communicate. This can include paper-based tools, electronic devices, books, gestures, eye gaze, and vocalizations. In the context of AAC, the term “symbol-based tools” is often used to refer to tools such as boards, books, or electronic devices that use symbols to facilitate communication^[2].

AAC can be used to augment existing speech, meaning it can be used to supplement or add to verbal communication. It can also serve as an alternative form of communication for those who are unable to use verbal speech. This means that AAC can be used by individuals who have some speech abilities, as well as by those who have no speech abilities^[3].

AAC is often used to support individuals with communication difficulties, such as those with Angelman Syndrome. The goal of AAC is to help these individuals communicate their wants, needs, hopes, and thoughts about their world^[1].

AAC systems should be robust, including core words, fringe words that are meaningful, social words, and the alphabet. They should be organized and customizable, allowing for the creation of a mental cognitive schema for where things are and a motor plan for how to access them. They should also include messages for communication partners as well as for the AAC user, and provide communication repair strategies^[4].

It’s important to note that AAC is not a one-size-fits-all solution. The most effective AAC system for an individual will depend on their unique needs and abilities. Therefore, it’s crucial to work with a team of professionals to set up an AAC system that will be successful for the individual^[1].

AADC

Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare neurological disorder that arises from a mutation in the DDC gene. This gene is responsible for producing an enzyme that converts precursors for dopamine and serotonin into their active neurotransmitters. In individuals with AADC deficiency, this gene mutation results in extremely limited muscle strength, control, and movement^[1].

AADC deficiency is often identified in children who fail to hit developmental milestones. The symptoms can be severe, including difficulty swallowing, inability to hold the head up, and frequent hospitalizations due to complications such as aspiration and suffocation. The life expectancy of individuals with AADC deficiency is generally less than a decade^[2].

AADC deficiency is a monogenic disease, meaning it is caused by a single gene mutation. This makes it an attractive target for gene therapy, a treatment approach that involves replacing or modifying the faulty gene. In the case of AADC deficiency, gene therapy has shown promising results. For example, a study involving a two-year-old boy with AADC deficiency showed significant improvement in muscle control and movement one year after treatment. Two years post-treatment, the boy was able to stand, grasp objects, and respond to his caretaker^[1].

The success of gene therapy in treating AADC deficiency has implications for other monogenic diseases, such as Angelman syndrome. Like AADC deficiency, Angelman syndrome is caused by a single gene mutation (in the UBE3A gene). The lessons learned from gene therapy programs for AADC deficiency can be applied to the development of similar treatments for Angelman syndrome^[1].

AAV

Adeno-associated virus (AAV) is a type of virus that is often used in gene therapy due to its ability to deliver therapeutic genes to cells. AAVs are considered safe for use in gene therapy because they do not cause any human disease by themselves and they have a low immune response compared to other viruses^[1]. AAVs are engineered for gene therapy by replacing the viral genes with a therapeutic gene needed by a patient. They can target both dividing and non-dividing cells, which is important for diseases like Angelman Syndrome where the target is neurons, which are non-dividing cells^[2].

AAV9 is a specific serotype of AAV that is commonly used in gene therapy, especially for targeting the brain through the cerebral spinal fluid. A serotype refers to antigenically distinct strains of a virus determined by their surface proteins. Changing the surface proteins on the capsid (the protein shell that encloses the genetic material of the virus) changes the way the AAV behaves^[2]. AAV9 has been used in clinical trials for a variety of diseases, including spinal muscular atrophy and several storage diseases^[3].

The AAV9 capsid is used to deliver a therapeutic gene, which can be engineered to replace a mutated gene, enhance the expression of a silenced gene, or decrease the expression of a gene, depending on the underlying biology of the specific disease^[4]. AAV9 has the most clinical experience and there is a lot of clinical trial precedent with it. It is known to get into neurons and brain cells as needed^[5].

However, there are some challenges associated with the use of AAVs in gene therapy. They have a limited capacity for genetic material, which means that if a gene is very large, AAV may not be an option. Currently, patients are limited to a single dose of AAV, as the body will make neutralizing antibodies against the AAV after dosing, which prevents redosing. There are also challenges with pre-existing neutralizing antibodies and lower numbers of cells targeted in the brain^[2]. Despite these challenges, AAV9 remains a promising tool for gene therapy in conditions like Angelman Syndrome.

ABOM

The Angelman Syndrome Biomarker and Outcome Measure Consortium (ABOM) is a collaborative initiative that brings together a diverse group of stakeholders, including pharmaceutical companies, clinicians, translational research teams, patient advocacy groups, and parents of individuals with Angelman syndrome^[1]. The consortium is composed of over 300 members who are interested in advancing regulatory science to develop, test, and validate tools that can assess individuals living with Angelman syndrome^[1].

The primary goal of ABOM is to advance endpoints and biomarkers, which are required to accurately test drugs in clinical trials^[1]. The consortium has developed a list of priority symptoms experienced in Angelman syndrome that drug companies are focused on trying to improve. These include challenges faced by patients in areas of communication, gross motor and fine motor skills, behaviors, sleep, seizures, cognition, independence/activities of daily living, and patient and caregiver quality of life^[1].

In addition to identifying priority symptoms, the ABOM team is also working to develop the best biomarkers, which are objective measures like EEG, body fluid protein changes, etc., that can be utilized by multiple parties to accelerate clinical trial design and execution^[1].

The ABOM initiative also includes the development of tools like the ActiMyo, a wearable device for the ankle that is being used in two active ASO clinical trials, and the Quality of Life Scale for parents and caregivers^[1].

The ABOM is also involved in the assessment of measures like the Vineland (VABS-3) and Bayley Scale of Infant and Toddler Development (BSID-4), which have a large amount of data based on the Angelman syndrome natural history studies^[1].

The ABOM’s work is crucial for clinical trials as it helps identify what is meaningful and measurable in the lives of individuals with Angelman syndrome. If a drug provides a transformative benefit, the ABOM’s tools and measures help make it easily determinable, which in turn supports drug approvals^[1].

The ABOM’s efforts are creating a platform that all industry partners can leverage, and many other rare diseases are modeling^[1]. The consortium’s work is guided by what is meaningful and important to families living with Angelman syndrome^[2].

The ABOM’s work is also helping to fill gaps in the natural history study of Angelman syndrome, improving the way data is collected, published, and analyzed, which is incredibly important for clinical trials^[2].

In summary, the ABOM is a critical initiative that is advancing the understanding and treatment of Angelman syndrome by developing and validating tools and measures that are meaningful and measurable for individuals living with the condition.

Activation

Activation, in the context of Angelman Syndrome research, refers to the process of turning on or activating a specific gene, particularly the paternal allele of the UBE3A gene. Angelman Syndrome is a genetic disorder that primarily affects the nervous system. It is caused by a loss of function in the UBE3A gene inherited from the mother. However, everyone has a second copy of the UBE3A gene inherited from the father, which is typically silenced or “turned off” due to a natural process called genomic imprinting^[1].

The concept of activation in Angelman Syndrome research is centered around the idea of “turning on” this silenced paternal allele of the UBE3A gene. This process aims to compensate for the loss of function in the maternal allele, thereby potentially alleviating the symptoms of Angelman Syndrome^[1].

There are several approaches being explored to achieve this activation. One method involves the use of artificial transcription factors (ATFs) or antisense oligonucleotides (ASOs). ATFs are proteins that bind to specific DNA sequences and influence the transcription of genetic information from DNA to messenger RNA. ASOs, on the other hand, are short, synthetic pieces of DNA that can bind to specific messenger RNA molecules and influence the production of proteins^[1].

Another approach involves the use of CRISPR technology, a powerful tool for editing genomes, which has been shown to rescue phenotype in a mouse model of Angelman Syndrome when administered early in development^[2].

It’s important to note that while these approaches are promising, they are still in the experimental stages, and more research is needed to determine their safety and efficacy in treating Angelman Syndrome.

Adverse Event

An adverse event, in the context of clinical trials, refers to any medical occurrence associated with the use of a drug in humans. These events can be related or unrelated to the study drug. Regardless of their relation to the drug, it is the decision of the principal investigator, typically a doctor, to determine whether a particular medical occurrence should be reported as an adverse event^[1].

Adverse events can range in severity and frequency among participants. The frequency and severity of such events in all participants are used to determine whether the drug is safe and well tolerated^[1]. For example, in the TANGELO study, some participants experienced fever and vomiting a few days after receiving the drug through injection. These symptoms were manageable with over-the-counter medication and resolved in a few days without any sequelae^[1].

In some cases, adverse events can be serious, leading to significant health issues or even death. However, these are rare events. In most cases, clinical trials demonstrate extraordinary safety and good progress^[2].

Adverse events can also be unrelated to the drug being studied. For instance, in a study mentioned in the Pharma Industry Update session, some unrelated adverse events included chickenpox reactivation and nausea and vomiting after swallowing an ECG lead^[3].

In some trials, adverse events have led to temporary or permanent discontinuation of the drug. For example, in a trial involving GTX-102, an antisense oligonucleotide (ASO) as a potential therapeutic for Angelman Syndrome, some patients experienced serious adverse events such as lower extremity weakness, leading to the temporary halt of the trial^[4].

It’s important to note that all adverse events, whether related or unrelated to the drug, are continuously and rigorously reviewed to facilitate the detection of potential safety signals from the study treatment. This ongoing review process aids in risk assessment and determination of the benefit-risk relationship of the drug^[1].

In conclusion, adverse events are a critical aspect of clinical trials, providing valuable information about the safety and tolerability of a drug. They are carefully monitored and reported to ensure the protection of trial participants and the integrity of the study results.

Alogabat

Alogabat is a drug being investigated for its potential to treat Angelman Syndrome, specifically in individuals with the deletion genotype^[1]. Angelman Syndrome is a genetic disorder that occurs on chromosome 15q, and individuals with the deletion genotype have a longer missing gene sequence, which includes the GABA gene^[2]. This gene is responsible for creating GABA receptors, which are crucial for brain function and development^[1].

GABA receptors, particularly the GABA-R alpha-5 receptors, are important for brain function and development. Dysfunction of these receptors has been linked with many neurodevelopmental disorders and with epilepsy^[1]. In individuals with Angelman Syndrome deletion genotype, the GABA-R alpha-5 receptors are primarily affected^[1].

Alogabat is an oral tablet that is taken once a day and is designed to enhance the function of the GABA-R alpha-5 receptors^[1]. The drug has already been investigated in healthy volunteers and is also under investigation in a different trial for autism spectrum disorders in adolescents and adults^[1]. To date, Alogabat has shown an acceptable safety and tolerability profile^[1].

The drug is currently being tested in a phase 2a clinical trial named Aldebaran, which is an open-label study, meaning there is no placebo^[1]. The trial aims to enroll up to 56 individuals with the deletion genotype, both males and females^[1]. The study’s objectives include investigating the pharmacokinetics of Alogabat (understanding what the body does to the drug once it is administered), its safety and tolerability, and the mechanism of action of the drug^[1][2].

The Aldebaran study started in the first half of the year following the source’s publication in 2022, and the first patient was recruited in July of the following year^[2]. The study includes a screening period of up to six weeks, followed by 12 weeks of treatment, and ends with a six-week follow-up^[2].

In summary, Alogabat is a promising drug under investigation for its potential to treat individuals with Angelman Syndrome deletion genotype by enhancing the function of the GABA-R alpha-5 receptors.

Angelman Syndrome

Angelman Syndrome is a rare neurodevelopmental disorder characterized by severe intellectual and developmental disability, sleep disturbance, seizures, jerky movements (especially hand-flapping), frequent laughter or smiling, and usually a happy demeanor. It is caused by a genetic mutation on chromosome 15, which affects the UBE3A gene. This gene provides instructions for making a protein that is involved in targeting other proteins to be broken down (degraded) within cells. The degradation of proteins is a normal process that removes damaged proteins and regulates the level of certain proteins in cells.

There are different types of Angelman Syndrome, including deletion, uniparental disomy (UPD), and others, which are determined by the specific genetic cause of the disorder. The symptoms of Angelman Syndrome can vary widely among individuals, and they may include issues such as anxiety, sleep disturbances, and physical symptoms like drooling. A physician can provide a checklist of symptoms to help identify the specific characteristics of the syndrome in an individual patient^[1].

Research into Angelman Syndrome has provided insights into other neurodevelopmental disorders, such as autism^[2]. There are currently numerous therapeutic strategies being developed to treat Angelman Syndrome, including both preclinical and clinical developments. These strategies aim to target the genetic causes of the disorder and alleviate its symptoms^[3]. As of 2023, there are four cutting-edge therapies being tested in clinical trials, and twenty more research programs are underway that could yield treatments ready for human testing in the next several years^[4].

Despite the progress in understanding and developing treatments for Angelman Syndrome, there are still challenges in the field. One major obstacle is the lack of doctors who know how to administer the new therapies^[4]. Furthermore, while physicians can provide recommendations for managing the symptoms of Angelman Syndrome, they do not have control over the implementation of these recommendations in settings such as schools^[1].

In conclusion, Angelman Syndrome is a complex neurodevelopmental disorder with a genetic basis. While there are currently no cures, ongoing research is promising and is paving the way for potential treatments.

Animal Disease Model

An Animal Disease Model is a non-human animal that has been genetically engineered or naturally developed to exhibit symptoms and conditions similar to a human disease. These models are used extensively in biomedical research to study the pathophysiology of diseases, test potential treatments, and understand the genetic basis of certain conditions.

Animal disease models can be created in a variety of species, including mice, rats, and larger animals like pigs. The choice of animal often depends on the specific disease being studied, the type of research being conducted, and the resources available. For instance, mice models have been widely used due to the availability of technology that allows for their genetic engineering. However, with the advent of CRISPR-Cas9 technology, researchers now have the ability to genetically modify the genomes of virtually any animal, expanding the range of potential disease models^[1].

In the context of Angelman Syndrome, a genetic disorder, multiple animal models have been developed, including mouse, rat, and pig models. These models are used to understand the pathophysiology of the condition and to test potential treatments. For example, the pig model of Angelman Syndrome was developed to replace the mouse model, with the idea that compounds found through various assays could be validated in a large animal model before moving to human trials^[2][1].

Animal disease models play a crucial role in translational research, which aims to “translate” findings from basic science into medical practice and meaningful health outcomes. They allow researchers to conduct experiments that would be impossible in humans due to ethical considerations, and they provide valuable insights into disease mechanisms that can inform the development of new therapies^[1].

However, it’s important to note that while animal disease models can provide valuable insights, they are not perfect replicas of the human condition. Differences in physiology, metabolism, and disease progression between species mean that results obtained from animal models may not always directly translate to humans. Therefore, findings from animal models should be interpreted with caution and validated in human studies whenever possible.

Antisense RNA

Antisense RNA is a type of RNA molecule that binds to and inhibits the function of a corresponding messenger RNA (mRNA) molecule. It is a single-stranded RNA that is complementary to a protein-coding mRNA molecule, and it can prevent this mRNA from being translated into protein. Antisense RNA is a crucial tool in molecular genetics and is being explored as a therapeutic agent in the treatment of diseases such as Angelman Syndrome.

In the context of Angelman Syndrome, the disease is caused by a loss of function in the UBE3A gene that comes from the mother. However, there is a normally functioning copy of the UBE3A gene from the father, but it is silenced by an antisense RNA^[1]. This antisense RNA binds to the UBE3A mRNA, preventing it from being translated into the UBE3A protein, which is necessary for normal brain function.

Antisense oligonucleotides are small stretches of DNA that can bind to RNA, including antisense RNA, and modulate its expression or splicing pattern^[1]. These oligonucleotides can be designed to interact with the antisense RNA, causing its degradation and allowing the paternal UBE3A gene to be expressed^[2]. This results in the production of the UBE3A protein, which can potentially alleviate the symptoms of Angelman Syndrome.

Antisense RNA is also involved in a process known as transcriptional collision, where the transcription of the UBE3A gene and the antisense RNA collide, preventing the completion of either process^[2]. Antisense oligonucleotides can potentially disrupt this process, allowing the UBE3A gene to be fully transcribed and translated into protein.

In summary, antisense RNA is a molecule that can bind to and inhibit the function of a corresponding mRNA molecule. In the context of Angelman Syndrome, antisense RNA prevents the expression of the UBE3A gene from the father, contributing to the disease’s symptoms. Antisense oligonucleotides are being explored as a potential therapeutic agent to degrade the antisense RNA and allow the expression of the UBE3A gene, potentially providing a treatment for Angelman Syndrome.

ASO

Antisense oligonucleotides (ASOs) are a type of therapeutic agent used in the treatment of various diseases, including Angelman Syndrome (AS). ASOs are small strings of nucleotides that bind to RNA, the molecule that carries genetic information from DNA to the protein-making machinery of the cell. This binding can correct mistakes in the RNA, leading to the production of the correct amount of protein needed by the body^[1].

ASOs are considered disease-modifying drugs because they target the source of the disease, unlike other drugs that target the symptoms. They work by replacing the missing gene product in individuals with AS, making them an exciting therapeutic option^[2].

In the context of Angelman Syndrome, ASOs are used to unsilence the father’s copy of the UBE3A gene, which is normally silenced in neurons. This allows the production of the UBE3A protein in the brain, which is deficient in individuals with AS^[1].

The ASOs are delivered into the brain by injection into the cerebrospinal fluid (CSF) via a lumbar puncture into the intrathecal space near the lower back. This method is necessary because ASOs are too large to cross the blood-brain barrier easily^[1]. Once in the brain, the ASOs enter neurons and move to the cell nucleus to engage the chromatin, large structures composed of tightly wound and packaged DNA. The ASOs bind to the UBE3A antisense transcript, leading to its degradation and the activation of the paternal copy of the UBE3A gene^[3].

ASO treatment has shown promise in reversing some of the symptoms of AS in mice, including memory impairment. However, more extensive reversal of AS characteristics may require treatment at a younger age, a longer recovery time after treatment, or a higher dosage of ASO^[4].

Research is ongoing to optimize the therapeutic efficacy of ASOs in treating AS. Key questions being investigated include the amount of ASO and UBE3A protein needed to rescue behavioral phenotypes, whether ASO treatment is required throughout life, and when ASO treatment should start to fully rescue epilepsy in AS mice^[2].

In conclusion, ASOs represent a promising therapeutic strategy for diseases of the central nervous system, including Angelman Syndrome. They offer a targeted approach to treatment by addressing the genetic source of the disease^[4].

ATF

An artificial transcription factor (ATF) is a bioengineered protein designed to bind to a specific sequence in the genome and modulate gene expression^[1]. This technology is used to control which genes are turned on and off, and which genes are producing RNA^[1]. ATFs are also known as zinc fingers^[2].

In the context of Angelman Syndrome (AS), ATFs have been used to activate the normally silenced paternal copy of the UBE3A gene^[3]. AS is a genetic disorder where the maternal copy of the UBE3A gene is either missing, mutated, dysfunctional, or turned off, while the paternal copy is normal but silenced due to a phenomenon called “imprinting“^[3].

Research has shown that ATFs can unsilence the paternal copy of UBE3A, potentially offering a therapeutic approach for AS. For instance, a study conducted by UC Davis demonstrated that a single dose of an ATF, packaged in an AAV viral vector and administered to young adult mice, resulted in a reduction in the Ube3a-ATS and an increase in Ube3a protein expression throughout the mouse brain^[4]. This treatment was well tolerated without a significant immune response and led to improvements in the mice’s motor abilities, including overall activity, motor learning, balance/coordination, and gait metrics^[4].

However, creating these ATFs requires extensive purification efforts, and the protein is quickly degraded in the body^[4]. Therefore, the development of ATFs as a therapeutic strategy for AS is still in the preclinical phase^[5].

It’s important to note that while ATFs show promise, they are just one of several gene editing and gene therapy strategies being explored for the treatment of AS. Other strategies include antisense oligonucleotides (ASOs), CRISPR technology, and downstream therapeutics^[2][5].

Autologous

An autologous transplant is a medical procedure that involves the collection, modification, and reinfusion of a patient’s own stem cells. This process is commonly used in the treatment of diseases such as lymphoma and myeloma, and is considered a routine practice in these contexts^[1].

The process begins with the collection of stem cells from the patient. These stem cells are then stored and modified as needed before being returned to the patient^[1]. In the context of gene therapy, the stem cells are used as a vehicle to introduce new genes into the system^[1].

Autologous transplants differ significantly from allogeneic transplants, which involve the use of stem cells from a donor. Allogeneic transplants can lead to complications such as graft-versus-host disease, where the donor cells attack the recipient’s body, or graft rejection, where the recipient’s body rejects the donor cells. Patients who undergo allogeneic transplants often need to be on immunosuppression for the rest of their lives^[2].

In contrast, autologous transplants involve the patient’s own cells, reducing the risk of rejection or adverse immune reactions. However, some form of conditioning is usually required to create space in the bone marrow for the reintroduced cells to engraft. This conditioning often involves a controlled dose of chemotherapy, which is typically lower than the doses given to cancer patients^[2][2].

Autologous transplants are considered safer than allogeneic transplants. For instance, in a center where autologous transplants are performed for myeloma, the mortality rate is reported to be 0.5%, even though many of the patients are elderly and have multiple comorbidities^[2].

In the context of gene therapy for genetic disorders such as Angelman Syndrome, researchers are exploring the use of autologous transplants to introduce corrected genes into the patient’s system. This approach has the potential to provide a permanent cure for the disorder^[1].

Bayley

The Bayley Scales of Infant and Toddler Development, commonly known as the Bayley, is a standard series of measurements used to assess the motor (fine and gross), language (receptive and expressive), and cognitive development of infants and toddlers, typically up to age 3. The test is often used in clinical trials and research studies to measure developmental progress or delays in young children, including those with Angelman Syndrome (AS)^[1].

However, the Bayley has been recognized to have limitations, particularly when used with children with AS. For instance, it does not provide standardized scores for older children, and it may not accurately reflect day-to-day functioning. It also may not be granular enough to pick up small changes in communication that can be seen in AS^[1][2].

To address these limitations, researchers have been working on ways to improve the use of the Bayley in AS clinical trials. One initiative involves pooling together data from three sites (Boston Children’s Hospital, UNC, and Erasmus Medical Center in Netherlands) to identify patterns of responding in individuals with AS. This involves analyzing each individual’s response to each item on each scale of the Bayley, comparing it across scores, and identifying patterns based on subtype^[1].

Another initiative is to standardize the instructions and adaptations to administer the Bayley to children with AS^[1]. There is also an effort to pilot the Bayley Special Needs Edition with the AS population^[1].

Despite its limitations, the Bayley remains a valuable tool in AS research. For example, in the GTX-102 program for AS, patients’ Bayley 3 scores were converted to Bayley 4 scores for analysis. The results showed that by the one-year mark, patients in the Bayley 4 cognition domain assessment had exceeded the threshold of significance^[3]. Similarly, in the HALOS clinical trial, early signals showed some clinical changes observed a month after the last dose in the MAD portion of the trial, as measured by the Bayley^[4].

In conclusion, while the Bayley has its limitations, it continues to be used and improved upon as a tool for assessing developmental progress in children with AS.

BBB

The blood-brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from non-selectively crossing into the central nervous system’s extracellular fluid where neurons reside. This barrier is crucial for protecting the brain from harmful substances in the blood, while also allowing essential nutrients to reach the brain.

The BBB is formed by brain endothelial cells, which are connected by tight junctions. These tight junctions are different from those found in blood vessels outside the brain, as they prevent molecules from easily passing through^[1]. The BBB separates the cerebral spinal fluid (CSF) from peripheral tissues, such as the blood^[1].

The BBB is a significant challenge for drug delivery to the brain. The transfer of drugs across the BBB into the CSF is often prevented by factors such as the size of the drug or the charge or both^[1]. For instance, large drugs and certain therapeutic molecules find it difficult to penetrate the BBB^[2].

To bypass the BBB, one method is to inject a therapeutic molecule directly into the CSF, a technique known as intrathecal administration. This allows the drug to be introduced directly into the CSF without having to go through the BBB^[1].

Another method to bypass the BBB is to use a gene delivery vehicle, such as an adeno-associated virus (AAV), that has properties of being transported out of the blood into the brain. This has been achieved in mice using a modified version of a vector called AAV9^[3].

However, it’s important to note that disrupting the BBB may have potential risks. For instance, in certain neurological disorders where the BBB is already weakened, further disruption may be detrimental^[4].

In conclusion, the BBB plays a crucial role in maintaining the brain’s internal environment and protecting it from harmful substances. However, it also presents a significant challenge for drug delivery to the brain, necessitating the development of strategies to bypass or cross this barrier effectively and safely.

Biomarker

A biomarker, short for biological marker, is a measurable indicator of some biological state or condition. In the context of Angelman Syndrome, biomarkers are used in two primary ways. First, they are used to determine whether a therapeutic intervention is functioning as expected. For example, researchers might look for changes in targets of UBE3A, the gene that is typically inactive in individuals with Angelman Syndrome, when UBE3A is restored. This could involve taking blood or cerebrospinal fluid (CSF) samples, or other non-invasive measures, to see if the therapeutic intervention is functioning as expected^[1].

Second, biomarkers are used to determine whether the restoration of UBE3A is improving the condition of the individual with Angelman Syndrome. This involves looking for changes in the individual’s physiology that indicate that the restoration of UBE3A is having a beneficial effect^[1].

Biomarkers are important because they provide an objective measure of the effects of a drug. They can help to bolster results that are subjective on clinical measures, and when well-understood, they can revolutionize the development landscape^[2]. For example, in the field of multiple sclerosis, advances in MRI technology have allowed researchers to understand that activity on the MRI in the brain of patients with MS is a bad marker for what’s going to happen clinically^[2].

However, it’s important to note that the use of biomarkers as surrogate endpoints in clinical trials is not straightforward. It requires a deep understanding of what the biomarker means for the disease, how it changes over time, how it can be influenced by treatment, and how it predicts clinical outcomes^[2].

In the case of Angelman Syndrome, one biomarker that has gained visibility is delta power, an aspect of the EEG that is very characteristic in Angelman Syndrome. This biomarker is also present in the mouse model of Angelman Syndrome, which is beneficial for research purposes^[2].

Despite their potential, the use of biomarkers in proving that a drug works can be challenging. For example, in a five-year period, only 11 genetic disease approvals used biomarkers for approval, and all of these biomarkers had been used in the 1990s^[3]. However, biomarker studies can still be valuable in helping to determine how to dose a drug, which is particularly important for neurological diseases^[3].

In conclusion, biomarkers are a crucial tool in the development and testing of therapeutic interventions for Angelman Syndrome. They provide objective, measurable indicators of the effects of a drug and can help to predict clinical outcomes. However, their use requires a deep understanding of the disease and the biomarker itself.

Biotech

Biotechnology, often shortened to biotech, is a field of science that merges biology with technology. It involves the manipulation of living organisms or their components to produce useful, usually commercial, products. Biotech is used in various industries, including health care, crop production and agriculture, nonfood uses of crops and other products (e.g., biodegradable plastics, vegetable oil, biofuels), and environmental uses.

In the context of Angelman Syndrome research, biotech plays a crucial role in developing potential treatments. For instance, one approach involves using proteins as therapeutics, also known as biologics. This method takes advantage of the fact that our bodies naturally produce proteins, unlike drugs which have to be synthesized and introduced externally^[1].

Another key area of biotech in Angelman Syndrome research is gene therapy. This involves introducing, removing, or altering genetic material within a cell to treat or prevent disease. The challenge lies in delivering the normal version of the gene into the right cells of the patient in a way that is both efficient and safe^[2].

One of the most promising gene editing technologies is CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats). This technology, which has been widely adopted since its introduction in 2013, allows for precise modifications to the DNA of humans, plants, and other animals^[3].

Antisense technology is another innovative approach being explored. This involves using antisense oligonucleotides, which are short DNA or RNA molecules that can bind to specific messenger RNA molecules to control gene expression. This technology is seen as a form of precision medicine, targeting the specific genetic defects causing diseases like Angelman Syndrome^[4].

However, the application of biotech in treating Angelman Syndrome is not without challenges. For instance, the regulatory environment and the need for clinical and preclinical studies can slow down the process^[5]. Additionally, the manufacturing and quality infrastructure for biologics, such as gene therapies, is complex and requires careful oversight^[6]. Despite these challenges, the field of biotech continues to evolve and holds great promise for the future of Angelman Syndrome research and treatment.

Brain organoid

A brain organoid, also known as a cerebral organoid, is a three-dimensional (3D) microstructure grown in a laboratory, which resembles the human brain. It is derived from pluripotent stem cells, often taken from skin or blood cells, that have been coaxed to mature into a tissue-like state in a laboratory dish^[1]. These organoids are microtissues composed of anywhere from 100,000 to over a million cells^[2].

Brain organoids provide a model system that combines the complexity of tissues as they exist in a living organism (in vivo) with the simplicity and ease of cell culture in a lab (in vitro)^[1]. They display many of the properties of real tissues but are much easier to work with. They can be genetically manipulated quickly and grown by the hundreds^[1].

These organoids are especially suitable for work involving the human brain. They have been shown to form self-directed neural networks with electrophysiological properties reminiscent of those in the brain itself, similar to what we see on an EEG when evaluating brain waves^[1].

Brain organoids can create cell types from all parts of the human brain^[2]. They contain many diverse cell types of the human brain and so capture this aspect of diversity in an efficient way^[2]. They also exhibit a lot of structure, for example, cortical lamina that resemble the outer layers of the brain^[3].

However, it’s important to note that brain organoids do have their limitations. Currently, organoids generate cell types that do not seem to mature past prenatal stages. They also exhibit molecular signatures of stress from just being in a cell culture rather than being in a natural brain tissue environment. Improvements could be made in areas such as improving the tissue organization, the layering structures, different regions of the brain, and introducing blood vessels into these systems^[2].

Despite these limitations, brain organoids provide a valuable tool for studying complex neurological conditions like Angelman Syndrome. They allow researchers to test neuron function in a laboratory and screen many different drug or gene therapy candidates to understand quickly if they have promise to work in neurons of those living with Angelman syndrome^[1].

Cell

A cell is the basic structural, functional, and biological unit of all known living organisms. It is the smallest unit of life that can replicate independently, and cells are often called the “building blocks of life”. The study of cells is called cell biology.

Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids. Cells function as the fundamental units of biology, with each cell maintaining its own life processes while contributing to the function of an organism as a whole.

Cells are very small but alive, they breathe, eat, and produce energy, functioning like mini factories^[1]. They are made up of even smaller elements called organelles, which have specific functions within the cell. For example, the nucleus of a cell contains its genetic material, while mitochondria produce the energy that cells need to function.

Cells can differentiate into many different types, depending on the type of cell required by the organism. This process is known as cell differentiation and is crucial for the development of complex multicellular organisms. For instance, in humans, there are several different types of cells, including skin cells, muscle cells, and nerve cells, each with their own specific functions.

Cells also produce proteins, which are essential for the life of the whole body^[1]. Proteins are complex molecules that play many critical roles in the body. They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs.

In recent years, scientists have developed techniques to reprogram somatic cells (like skin or blood cells) into a special type of cell called induced pluripotent stem cells (iPSCs). These iPSCs can then be differentiated into many different types of cells^[2]. This technique has opened up new possibilities for understanding diseases and testing treatments.

In summary, cells are the fundamental units of life, with complex structures and functions that enable the existence and survival of all living organisms. They are capable of independent replication, differentiation into various types, and production of essential proteins.

Cell Line

A cell line refers to a population of cells derived from a single cell and grown in a lab. These cells are maintained under specific conditions and allowed to proliferate indefinitely. Cell lines are valuable tools in scientific research, allowing scientists to study the biology of cells, their genetic makeup, and their response to drugs or other stimuli. They can be derived from various sources, including human tissues, animal tissues, or cancer cells.

Cell lines are often genetically manipulated to serve specific research purposes. For instance, in the context of Angelman Syndrome (AS), researchers generate cell lines that carry the same genetic mutations found in individuals with AS. These cell lines are used to model the disease in the lab, providing insights into the molecular mechanisms underlying AS and facilitating the development of potential therapeutic strategies.

The generation of a cell line involves several steps. First, a single cell is isolated and cultured under conditions that allow it to proliferate. The resulting population of cells is then tested to ensure it carries the desired genetic mutation and does not contain any unwanted genetic changes that could confound research results. This process requires careful genetic workup and quality control to ensure the cell line accurately represents the disease it is intended to model.

In the context of AS research, cell lines are generated to reflect different genotypes of the disease. These include large deletions, UBE3A point mutations, Uniparental Disomy (UPD), imprinting defects, and UBE3A gain of function mutations. The goal is to create a minimum of three cell lines for each genotype, although more may be generated if necessary^[1][1].

These cell lines are designed to be isogenic, meaning they have the same genetic background except for the AS-related changes. This reduces variability in experiments and facilitates comparisons between different research groups and institutions. The cell lines are also engineered to be shareable, allowing them to be used by researchers worldwide^[2][3].

Once generated, these cell lines are distributed to investigators and industry partners for further research. They can be used to explore various therapeutic platforms, understand changes in phenotype or neuronal behavior associated with different AS genotypes, and study mosaic forms of AS^[4][5].

Cell Signalling

Cell signaling refers to the process by which cells communicate with each other to coordinate their functions and respond to their environment. This communication can occur within a single cell, between two neighboring cells, or between cells located in different parts of an organism. The signals can be physical (like touch) or chemical in nature. The process of cell signaling involves the transmission of a signal from a cell (the signaling cell), through a signaling molecule, to another cell (the target cell). This signal then triggers a specific response in the target cell^[1].

A pathway, in the context of cell signaling, refers to a series of actions among molecules in a cell that leads to a certain product or a change in the cell. These pathways can regulate a wide variety of cellular processes, including cell growth, cell death, cell differentiation, and more. Each pathway is characterized by a series of steps, each of which is mediated by a specific molecule. These molecules can be proteins, lipids, ions, or even small molecules like gases^[2].

In the context of Angelman Syndrome, a genetic disorder that primarily affects the nervous system, cell signaling and pathways play a crucial role. For instance, the UBE3A gene, which is absent or malfunctioning in individuals with Angelman Syndrome, is involved in a signaling pathway that regulates the levels of a protein called Arc. When UBE3A is absent, the levels of Arc increase, which can affect synaptic connections^[1].

Another example is the ubiquitin-proteasome pathway, which is involved in protein degradation. This pathway is also affected in Angelman Syndrome, leading to changes in the regulation of actin dynamics in dendritic spines^[2].

Furthermore, research has shown that the disruption of physiological processes, such as synaptic plasticity, can lead to the symptoms seen in Angelman Syndrome. Synaptic plasticity refers to the ability of synapses, the junctions between neurons, to strengthen or weaken over time in response to changes in their activity. This process is crucial for learning and memory^[3].

In summary, cell signaling and pathways are fundamental processes that regulate cellular functions. In the context of genetic disorders like Angelman Syndrome, understanding these processes can provide insights into the disease mechanisms and potential therapeutic targets.

Cell therapy

Cell therapy is a therapeutic approach that involves the introduction, removal, or manipulation of cells to treat or prevent diseases. It is a rapidly evolving field that holds significant promise for a variety of medical conditions, including genetic disorders such as Angelman syndrome^[1].

One form of cell therapy is autologous stem cell transplant, which involves using the patient’s own stem cells. In this process, stem cells are collected from the patient, modified in a laboratory setting, and then reintroduced back into the patient’s body^[1]. This approach is used in gene therapy, where the stem cells serve as a vehicle to deliver new genes into the patient’s system^[1].

In the context of Angelman syndrome, the therapeutic approach involves the use of hematopoietic stem cells (HSCs). These cells are collected from the patient, and the gene causing the disorder is inserted into them. The modified cells are then given back to the patient^[1]. This process is known as HSC gene replacement therapy.

The process begins with mobilizing the patient’s blood cells, where a drug is administered to help the stem cells move out of the bone marrow and circulate into the blood. These cells are then harvested through a process called apheresis, where the blood is separated and the stem cells are collected. The collected stem cells are then sent to a manufacturing facility where the gene therapy is inserted into them^[2].

Before the modified cells can be reintroduced into the patient’s body, the patient undergoes a process called conditioning. This involves administering chemotherapy to reduce the levels of blood cells in the body, making space for the new cells. The modified cells are then transfused back into the patient’s body^[2].

Cell therapy has shown promise in treating a variety of diseases. For instance, clinical trials have been conducted for diseases such as immune deficiencies and sickle cell anemia, where patients have responded well to the treatment^[1]. However, it is important to note that while cell therapy holds significant potential, it is still a developing field and further research is needed to fully understand its capabilities and limitations^[1].

Cell type

Cell types refer to a distinct morphological or functional form of cell. In the context of Angelman Syndrome research, various cell types are studied to understand the disease and develop potential treatments.

Neurons are one of the main cell types in the brain. They are responsible for connecting and sending signals between different cells in the brain to implement all functions. Neurons send these signals through their axons and receive signals on their dendrites, which are branching parts of the neuron^[1].

In addition to neurons, there are also neuroglial cells, which are supporting cells for the neurons. They help with the maintenance, growth, and management of the cells, as well as the connections between the neurons^[1]. One type of neuroglial cell is the microglia, which are important for supporting neurons and producing essential growth factors, such as insulin-like growth factor one (IGF-1)^[1].

Another cell type mentioned in the context of Angelman Syndrome research is the astrocyte. While the exact role of astrocytes in Angelman Syndrome is not fully detailed in the sources, they are mentioned as a cell type that researchers are studying^[2].

Stem cells are also a significant cell type in Angelman Syndrome research. There are two types of stem cells: pluripotent stem cells, which include embryonic or induced pluripotent stem cells, and somatic or tissue-specific stem cells^[3]. Pluripotent stem cells can generate all cell types of the adult body, making them a powerful tool for creating specific organoid models of Angelman Syndrome^[4]. Somatic stem cells, on the other hand, are more specialized. For example, hematopoietic stem cells are a type of somatic stem cell that forms blood^[3].

In addition to these, oligodendrocyte precursor cells (OPCs) are a type of cell with a set path to become a specific brain cell type, the oligodendrocyte^[5].

Overall, the study of these various cell types is crucial in understanding the pathophysiology of Angelman Syndrome and developing potential treatments.

Cerebellum

The cerebellum is a part of the brain located at the back of the skull. It plays a crucial role in regulating motor movements, balance, and coordination. Disorders of the cerebellum can lead to ataxia, which is characterized by stumbling and uncoordinated gait^[1].

In the context of Angelman Syndrome (AS), the cerebellum has been a focus of research due to its potential role in the motor impairments observed in individuals with AS. The original description of AS by Henry Angelman in 1965 emphasized the cerebellum, and while there is still some debate about the extent of cerebellar disturbance in AS, there is evidence of some pathophysiology^[1].

Research has shown that individuals with AS have movement problems and are unstable when walking, suggesting that the cerebellum plays a significant role in causing these issues^[2]. Studies using the Angelman mouse model have shown that cerebellar function can be studied through the use of certain coordinated repetitive behaviors such as feeding and licking behaviors^[2].

Further studies have shown that mice lacking UBE3A, the gene mutated in AS, perform reaching movements much slower than typical mice. The cerebellum, a brain region critical for processing sensory information during movement, has distinct dynamics during reaching movements in mice lacking UBE3A^[3].

In addition to motor impairments, individuals with AS may also experience issues with depth perception, the ability to isolate body parts, balance disorders, and tremors, all of which can impact their access to communication^[4]. These symptoms are thought to be related to a lack of tonic inhibition, a function regulated by the neurotransmitter GABA, leading to poor balance, poor motor coordination, a lack of speech, seizures, poor sleep, anxiety, dyspraxia, apraxia, poor attention spans, and a learning disability^[5].

In conclusion, the cerebellum plays a crucial role in the motor impairments observed in individuals with AS. While there is still much to learn about the exact mechanisms and extent of cerebellar involvement in AS, current research suggests that therapies targeting the cerebellum could potentially improve motor function in individuals with this condition.

CF

Cystic Fibrosis (CF) is a genetic disorder that primarily affects the lungs, but also the pancreas, liver, kidneys, and intestine. It is characterized by the production of thick, sticky mucus that can clog the lungs and obstruct the pancreas. This can lead to life-threatening lung infections and digestive problems. The condition is caused by mutations in the CFTR gene, which encodes a protein that regulates the movement of chloride ions across cell membranes. This ion movement is crucial for the production of mucus, sweat, saliva, tears, and digestive enzymes^[1].

In 1955, children with CF did not live long enough to go to elementary school, with the median survival being essentially five years of age. There were no CF doctors, clinics, science, or medicines, and there was no hope^[1]. However, the situation has dramatically improved over the years due to the efforts of organizations like the Cystic Fibrosis Foundation (CFF). Today, the median survival for people with CF is over 60 years of age, and there are 16 CF therapies available. These therapies address the basic defect of CF and have transformative benefits for 94% of people with the disease^[1][1].

The CFF has played a crucial role in this progress. They funded the seed research for CF drugs and maintained economic interest in those drugs to a certain point. They sold their royalties for $3.3 billion, both to avoid a conflict of interest and to make the process go faster. However, even with their initial investment in the research and strong advocacy for patient access, the CFF did not have a say in how any pharma company priced its drug^[2].

The CFF also developed a Therapeutics Development Program, which provided financing to industry so that their opportunity cost was non-existent. This program was aimed at enticing industry, including biotech and pharma, into the CF space, as they had the expertise and tools for drug discovery^[1]. Despite many failures, several programs did succeed, leading to the development of 16 approved therapies for CF^[1].

Despite these advances, the CF community is committed to reaching 100% of people with CF. Current programs are underway to ensure that no one is left behind^[1][1].

CGI-I

The Clinical Global Impressions of Improvement (CGI-I) is a tool used in clinical trials to assess changes in symptoms over time for each patient individually. It is a seven-point scale where a score of four indicates no change, scores of one, two, and three indicate improvement, and scores of five, six, and seven indicate worsening of symptoms^[1].

The CGI-I is used to monitor changes in symptoms from baseline, which is the patient’s condition at the start of the trial, over a specified period, such as six weeks or 12 weeks^[1]. The CGI-I score is determined based on inputs from various sources, including family members, caregivers, therapists, and feedback from school, among others^[1].

In the context of Angelman Syndrome, the CGI-I-AS is a refined version of the CGI-I, specifically designed to assess this condition. It provides strict guidance on how to assess different domains such as behavior, motor function (both fine motor, such as picking up a fork or a pencil, and gross motor, such as walking), sleep, and communication^[2].

The CGI-I-AS was developed to capture the totality of symptoms in Angelman Syndrome, which can present very differently in different individuals despite having the same genetic defect. For instance, the same defect may cause different manifestations in sleep, communication, motor function, behavior, seizures, or other symptoms^[1].

The CGI-I-AS is used as a primary endpoint measure in clinical trials for Angelman Syndrome, meaning it is a key outcome that the trial aims to investigate. It has been accepted by the FDA and the EMA as a primary endpoint measure^[2].

The CGI-I-AS tool could potentially be utilized in measurement with other studies^[2].

In conclusion, the CGI-I and CGI-I-AS are important tools for assessing changes in symptoms over time in clinical trials, particularly in the context of conditions like Angelman Syndrome where symptoms can vary widely between individuals.

cGP

Cyclic Glycine Proline (cGP) is a metabolite of Insulin-like Growth Factor 1 (IGF-1), a growth hormone produced throughout the body, including the brain^[1]. IGF-1 is responsible for the growth and development of neurons and the supporting cells that help maintain the neurons, such as microglia^[1]. When IGF-1 acts naturally in the body, it breaks up into smaller pieces, known as metabolites, one of which is cGP^[1].

cGP plays a crucial role in maintaining the balance of IGF-1 in the brain, ensuring there’s not too little or too much^[2]. It is responsible for homeostasis of IGF-1, which means it regulates the availability of IGF-1 to the IGF-1 receptor^[3]. This regulation is part of a complex auto-regulatory process that defines the IGF-1 system^[3].

cGP also has a unique feature in that it regulates the binding of IGF-1 to the IGF-1 receptor, thus controlling the availability of IGF-1 to perform its functions in the brain^[4]. This regulation is essential for the development, maintenance, repair, and maturation of synapses^[4].

In addition to its role in regulating IGF-1, cGP also has anti-inflammatory properties and can regulate the expression of inflammatory cytokines^[3]. It also addresses the problem of pathologically activated microglia, which are ineffective at dendritic pruning and maintaining the maturation of dendrites synapses^[3].

A synthetic analog of cGP, known as NNZ-2591, has been developed for use as a medication^[1]. This synthetic analog has the same molecular structure as cGP, but with one small modification that makes it more suitable for use as a medication^[1]. This means it can mimic the actions of the naturally occurring molecule, regulating IGF-1 levels, but also has properties that make it better for use as a medication, such as 100% bioavailability, the ability to cross the blood-brain barrier, and good pharmacokinetic properties^[1].

Chromosome

A chromosome is a long, string-like structure made up of DNA and proteins. It carries the genetic information that is necessary for the growth, development, and reproduction of an organism. In humans, each cell contains 23 pairs of chromosomes, for a total of 46. Each pair consists of one chromosome from the mother and one from the father^[1][2][3].

Chromosomes are located in the nucleus of a cell and are organized into structures called genes. Genes are segments of DNA that contain specific instructions for making proteins, which are crucial for the various functions of the body^[4]. The DNA in a gene is transcribed into RNA, which is then translated into a protein^[3].

The chromosome of interest in the context of Angelman Syndrome is chromosome 15. This chromosome is unique because the cells in our body can distinguish between the chromosome 15 inherited from the mother and the one inherited from the father. This is due to a process called genomic imprinting, which is a phenomenon where a gene is expressed exclusively from one parental allele^[5].

In the case of Angelman Syndrome, the gene of interest on chromosome 15 is UBE3A. This gene is typically only expressed from the mother’s copy of chromosome 15. Abnormalities in the UBE3A gene, such as a deficiency, can result in Angelman Syndrome^[2][6].

In summary, a chromosome is a structure that carries genetic information in the form of genes. These genes contain the instructions for making proteins, which are essential for the body’s functions. The understanding of chromosomes and their genes is crucial in the study of genetic disorders like Angelman Syndrome.

Cisterna magna

The cisterna magna, also known as the cerebellomedullary cistern, is a large space filled with cerebrospinal fluid (CSF) located between the cerebellum and the dorsal surface of the medulla oblongata in the brain. This space is part of the subarachnoid space, which is a compartment in the brain where CSF flows and is involved in cushioning the brain and spinal cord, supplying the brain with nutrients, and removing waste products.

In the context of gene therapy for neurologic diseases such as Angelman Syndrome, the cisterna magna has been identified as a key site for the delivery of therapeutic vectors. Injecting the vector into the cisterna magna has been found to be effective in achieving broad distribution in the region of the brain and down the spinal cord over time^[1]. This method of delivery has been shown to result in better distribution of the vector to the brain compared to injection into the lumbar space^[2].

The procedure involves pre-imaging and then under guidance, introduction of the needle into the cisterna magna. The device used is not complicated, consisting of a syringe, a needle, and small tubing^[3]. This technique, which is a standard practice in the veterinary world, has been adapted for use in human medicine and has been used in a number of clinical trials^[2].

The distribution of the vector along the brain, the spinal cord, and outside the central nervous system can be visually followed over time^[2]. The vector is able to penetrate into the brain through the perivascular spaces, which are spaces around the penetrating vessels where the CSF tracks^[4].

However, it’s important to note that not every cell in the brain expresses the gene after the vector is injected into the cisterna magna. The level of gene expression varies, but it’s estimated to be around 10 to 15 percent under the best circumstances^[5]. Despite this, the method has been found to be well-tolerated in monkeys and has been used in a number of clinical trials^[2].

Clinical Trial

A clinical trial is a research study that tests an intervention such as a drug, surgical device, or procedure in a disorder to determine its safety and efficacy (how well it works for the intended purpose) in humans^[1]. Clinical trials are a crucial part of medical research and are designed to test new treatments to see how well they work in helping people feel better or in helping a disease to improve or stop getting worse^[2].

Clinical trials typically consist of three parts:

1. Phase 1: This phase is designed to test the safety of the drug and is often the first time it has been tested in humans. A large component of studies in the early phase focuses on exploring dose ranges and safety of those doses^[3].
2. Phase 2: This phase is designed to evaluate both the safety and efficacy of the drug, essentially answering the question, “does the drug do what I want it to”^[3].
3. Phase 3: This phase is designed to confirm the safety and efficacy in a large group of people, usually a much larger number than what is done in a phase 1 or 2^[3].

Less commonly, there is a 4th part or “Phase 4” that happens after an intervention is approved for use by patients and involves potential follow-up studies to understand more about how the drug works in other groups not included in the initial studies or to answer other questions^[1].

Clinical trials can be either interventional or observational. Interventional clinical trials are studies that evaluate the safety and efficacy of a therapeutic for a disorder. Observational studies are research projects that evaluate characteristics and disorder progression over time but do not include the use of an intervention^[1].

Before participants can enroll in a clinical trial, they have to give their informed consent. Risks, benefits, and time alternatives are explained to the participant or the caregiver before they sign the informed consent^[2].

The decision to enroll in a clinical trial is a significant one that should be made in consultation with one’s family and doctor, taking into consideration all factors and preparing questions prior to enrollment^[3].

Clinical trials are initiated by a “Sponsor”, an organization/person who has authority and control over the study. Sponsors are generally the party who funds a study, although they might do this with the help of a “collaborator” (an organization in addition to the sponsor that provides support for a clinical study)^[4].

The Sponsor is responsible for ensuring the trial is conducted according to the study protocol and is responsible for seeking approvals to run the trial from regulatory agencies and ethics boards, as applicable^[4].

CNS

The central nervous system (CNS) is a crucial component of the body’s nervous system, which includes the brain and spinal cord. It is responsible for processing information received from all parts of the body and coordinating activity across the entire organism. The CNS is the primary control center for the body, capable of processing sensory information, regulating motor function, and controlling cognitive functions such as learning and memory.

The CNS is composed of neurons, or nerve cells, that transmit and process information. These neurons communicate with each other and with other cells through specialized connections called synapses, where electrical or chemical signals are transmitted from one cell to another. The CNS is also composed of glial cells, which provide support and protection for neurons. They play a crucial role in maintaining the balance, providing nutrients, and in some cases, even speeding up the transmission of signals^[1].

The CNS is protected by several barriers, including the skull, the vertebral column, and the blood-brain barrier. The blood-brain barrier is a highly selective semipermeable border that separates the circulating blood from the brain and extracellular fluid in the CNS. It prevents many substances, including many drugs, from entering the CNS, which can make treating diseases of the CNS challenging^[2].

In the context of diseases like Angelman Syndrome, the CNS is of particular interest because the pathology of these conditions often involves the nervous system. Angelman Syndrome, for example, is a genetic disorder that primarily affects the nervous system, leading to neurological and psychological issues, as well as orthopedic and ophthalmologic problems that trace back to the nervous system^[3].

Research into treatments for CNS diseases like Angelman Syndrome often involves strategies to deliver therapeutic agents to the CNS. One such strategy is the use of adeno-associated virus (AAV) vectors, which can be used to deliver genes to cells in the CNS. These vectors can be delivered through different methods, including intravenous infusion or injection into the cerebrospinal fluid (CSF), a clear body fluid that surrounds the brain and spinal cord^[4][2].

However, delivering therapeutic agents to the CNS is challenging due to the barriers that protect it. For example, intravenous delivery of gene therapy vectors is currently not achievable due to the size of the vectors and their inability to penetrate the blood-brain barrier^[5]. Therefore, research is ongoing to develop more efficient and effective methods of delivering therapeutic agents to the CNS.

Cohort study

A cohort study, in the context of clinical trials and research, refers to a type of observational study where a group of individuals, known as a cohort, is studied over a period of time. The individuals in a cohort share a common characteristic or experience within a defined period. This could be the diagnosis of a particular condition, such as Angelman Syndrome, or the administration of a specific treatment^[1].

In the context of Angelman Syndrome research, cohorts are often divided by age groups, as seen in the OV101 treatment study where the cohorts were divided into 4 to 12 years old and 9 to 12 years old^[2]. Similarly, in the TANGELO Phase 1 study, the cohorts were divided into 5 to 12 years old (cohort A) and 1 to 4 years old (cohort B)^[3].

Cohort studies are crucial in understanding the natural history of a condition, which refers to the progression of the disease without intervention. For instance, the Angelman Syndrome Natural History Study has been collecting longitudinal data over many years to understand the progression of the syndrome^[4].

In clinical trials, the cohorts can be further divided into treatment groups and control groups. The treatment group receives the therapeutic intervention being tested, while the control group may receive a placebo or standard treatment. These trials are often “blinded,” meaning the researchers and participants do not know which group the participants have been assigned to^[5].

Cohort studies are essential in clinical research as they provide valuable insights into the safety and efficacy of potential treatments, the progression of conditions over time, and the impact of various factors on the outcomes of the condition. They also help in identifying the highest safe dose of a drug that can be administered to patients^[3].

However, it’s important to note that cohort effects can influence the outcomes of these studies. For instance, individuals diagnosed earlier and now growing up may have different outcomes than those diagnosed later in life due to improvements in care and treatment strategies over time^[6].

CRISPR

CRISPR, an acronym for Clustered Regularly Interspaced Short Palindromic Repeats, is a gene-editing technology that has shown significant potential in the field of genetic research and therapy, including its application in Angelman syndrome^[1]. This technology was introduced to the gene-editing field in 2013 and has since been adopted by thousands of labs worldwide^[1].

CRISPR originated in bacteria as an immune system to fight off viral infections. The system works by creating a guide RNA (gRNA), which acts as an address label to the viral DNA. CRISPR uses this gRNA to target and cut the viral DNA into pieces, saving a piece of the viral DNA for future reference in case of reinfection^[1].

In scientific use, the term CRISPR is often followed by the name of a protein, with Cas9 being the most common. Cas9 uses a piece of gRNA to determine where to cut DNA. For instance, if a protein like UBE3A is incorrectly configured, a guide RNA matching the incorrect pattern is created. Cas9 then searches for this pattern and, upon finding a match, snips it out. However, the cut-out part needs to be replaced to prevent DNA damage. This is achieved through the cell’s natural repair process, which grabs for whatever sequence is immediately nearby that fits and inserts it^[1].

CRISPR technology is not limited to humans; it can also be used in plant and animal systems. For instance, it has been used to create animal models of Angelman syndrome for testing, by editing them to contain defective or missing copies of UBE3A^[1].

One of the significant advantages of CRISPR is its simplicity and flexibility. The Cas9 tool used for editing remains the same for each target gene, unlike other technologies such as zinc fingers, which need to be redesigned for every target gene. This makes it easier and faster for scientists to use. Additionally, the ability to target multiple gene targets simultaneously by providing multiple gRNA address labels is a revolutionary step forward for multigene diseases^[1].

However, there are challenges to overcome with CRISPR-based gene therapy options, including delivery, distribution throughout the neurons of the brain, potential off-target effects, and potential immune response^[2]. Despite these challenges, CRISPR offers one of the best possible avenues for a cure, and extensive programs are being spearheaded by organizations like the NIH to bring these potential gene-editing proteins to the clinic^[2].

CSF

Cerebrospinal fluid (CSF) is a clear body fluid that is produced in the brain and surrounds the brain and the spinal cord^[1]. It serves several crucial functions, including protecting the brain, regulating the chemical environment of the nervous system, providing the brain with nourishment, and assisting with waste product removal^[1].

The CSF is separated from the blood by the blood-brain barrier, which prevents the transfer of certain substances, such as drugs, from the blood into the CSF. This barrier is characterized by tight junctions in the blood vessels in the brain, which contrast with the more porous blood vessels outside the brain^[1].

The analysis of CSF is a common technique used for the diagnosis and prognostication of neurological diseases^[1]. In the context of Angelman Syndrome research, CSF is being studied to develop biomarkers for measuring substances like UBE3A^[2].

CSF can be accessed and analyzed through a procedure known as a lumbar puncture, which is often performed for diagnosis, anesthesia, and medical emergencies. During a lumbar puncture, a needle is inserted into one of the spaces between the bones in the lower back, and a sample of CSF is collected^[1]. This procedure allows for the direct introduction of a drug into the CSF, bypassing the blood-brain barrier^[1].

In the context of gene therapy, CSF delivery allows for the bypassing of the blood-brain barrier, enabling the direct introduction of a vector into the fluid-filled space around the spinal cord^[3]. This method is considered more efficient than blood delivery, as it allows the vector to travel around and up into the brain^[3].

In summary, CSF plays a crucial role in the functioning of the nervous system and is a valuable resource in the diagnosis and treatment of neurological conditions, including Angelman Syndrome. Its analysis can provide important information about the disease that may not be visible in blood, urine, or saliva samples^[4].

CVI

Cortical Vision Impairment (CVI) is a type of brain-based vision impairment where the eyes are physically healthy, but the brain has difficulty processing the visual information it receives. This condition is not related to any ocular issues, meaning that an ophthalmologist would not be able to detect any problems with the eyes themselves^[1].

CVI is characterized by 10 specific characteristics, and its assessment is known as the CVI range^[1]. Some children with Angelman Syndrome meet these characteristics, while others may not, but still exhibit atypical use of their vision^[1].

CVI can affect various aspects of a child’s life, including balance, walking, communication, and behavior^[2]. It can also impact how a child with Angelman Syndrome processes auditory and visual input simultaneously. For instance, some children may look at a person, but when that person starts talking, the child will turn away to listen. When the person stops talking, the child will turn back to look^[3].

In some cases, children with Angelman Syndrome and CVI may have strabismus, a condition where the eyes do not properly align with each other. Even if this condition is surgically corrected, the brain may continue to process visual information from only one eye, leading to unique ways of using vision^[1].

Despite the challenges CVI presents, it’s important to note that the brain is plastic and can learn. Therefore, interventions designed for CVI can help children learn to understand what they’re seeing better. These interventions won’t be fixed by glasses, but they can significantly improve a child’s ability to use their vision^[1].

Research is ongoing to estimate the prevalence of CVI in individuals with Angelman Syndrome, assess its severity, and determine its effect on communication^[2]. Understanding and identifying CVI in individuals with Angelman Syndrome can allow for early intervention, which may improve communication and behavior outcomes^[2].

Deletion

In the context of Angelman Syndrome, deletion refers to the loss of a large portion of genetic material, including the UBE3A gene and other genes. This deletion occurs on the maternal allele of the chromosome 15, which is responsible for the expression of the UBE3A gene. The paternal allele of the UBE3A gene is naturally silenced, and thus does not express the UBE3A protein. In individuals with Angelman Syndrome, the deletion of the maternal allele of the UBE3A gene results in the absence of functional UBE3A protein, leading to the symptoms of the syndrome^[1].

In addition to the UBE3A gene, the deletion also affects other genes, including the GABA receptor genes. These genes are crucial for brain development and neuronal function. The GABA receptor genes contain the information necessary to produce proteins that form the GABA alpha-5 receptor, a subtype of the GABA receptors. These receptors are located on the surface of neurons and are essential for neuronal communication, which is mediated by neurotransmitters such as GABA. In individuals with the deletion genotype of Angelman Syndrome, there is a reduced number of GABA alpha-5 receptors due to the deletion of the maternal allele of the GABA receptor genes^[1].

The deletion genotype of Angelman Syndrome is associated with a more severe clinical picture compared to other genotypes. Individuals with this genotype generally present with lower scores in cognition, communication, and motor skills domains, and have an earlier onset of seizures and diagnosis of epilepsy^[1]. They also exhibit higher frequencies of certain behaviors, such as mouthing behavior and sensory issues like tactile defensiveness and resistance to touching on the head^[2][3]. However, they tend to have less anxiety and lower percentages of explosive behavior compared to individuals with non-deletion genotypes^[2][3].

Despite the significant impact of the deletion on the UBE3A gene and other genes, it is important to note that this deletion represents a very small portion of the entire human genome. The human genome consists of approximately 20,000 genes, and the deletion in Angelman Syndrome affects only a small number of these genes^[4].

Disease concept model

A disease concept model is a comprehensive framework used in medical research and drug development to understand the full spectrum of a disease’s impact on patients and their caregivers. It is designed to identify the most significant aspects of a disease, including its symptoms, progression, and the burden it places on patients and their families. This model is particularly crucial in the development of therapies for conditions like Angelman Syndrome, where understanding the daily living needs of individuals and the impact on their families is as important as addressing clinical symptoms^[1].

The development of a disease concept model involves several steps. Initially, an in-depth literature review is conducted to understand what has been previously characterized about the disease. This is followed by interviews with expert clinicians and, most importantly, caregivers to get a broader scope of what it means to have the disease^[1]. The model is then refined through further insights and a more global quantitative assessment^[2].

The disease concept model is not only used to understand the disease but also to guide therapy development. It helps researchers identify the best outcome measures to use in a population that is both robust and relevant to the disease. It also aids in designing clinical trials in a patient- and caregiver-friendly way to reduce burden^[1].

In the case of Angelman Syndrome, a disease concept model was developed in collaboration with patients, caregivers, clinicians, and experts in the field. This model helped identify what a treatment would need to do for the patients and their families to be meaningful^[3]. A robust disease concept model was published in 2020, which identified communication and speech, seizures, motor function, and cognition as the most important symptoms to be impacted with a transformative treatment for Angelman Syndrome^[4].

In conclusion, a disease concept model is a critical tool in understanding the full impact of a disease and guiding the development of effective therapies. It ensures that the needs of patients and their families are at the center of clinical trial design and that the developed therapies are meaningful and impactful for them.

DNA

DNA, or deoxyribonucleic acid, is a molecule that contains the biological instructions that make each species unique. It is the hereditary material in humans and almost all other organisms. DNA is stored in the nucleus of cells and is made up of two strands that twist around each other in a double helix structure. Each strand is composed of four chemical units, or bases, represented by the letters A (adenine), C (cytosine), G (guanine), and T (thymine)^[1][2].

The sequence of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences. This information is encoded in segments of DNA called genes^[1]. Each gene has specific instructions for making a particular molecule, usually a protein^[2].

The process of using the information in DNA to make proteins involves two main steps: transcription and translation. In transcription, the DNA sequence of a gene is copied into a similar molecule called RNA (ribonucleic acid). This RNA molecule, also known as messenger RNA (mRNA), carries the genetic information from the DNA in the nucleus to the protein-making machinery in the cell’s cytoplasm^[1][3].

In translation, the cell’s machinery reads the sequence of the mRNA molecule and uses it as a code to assemble a chain of amino acids, creating a protein. Each three-letter sequence in the mRNA, known as a codon, corresponds to a specific amino acid^[1][2].

In the context of genetic disorders like Angelman Syndrome, understanding the role of DNA and its process of protein synthesis is crucial. For instance, the UBE3A gene, which is implicated in Angelman Syndrome, is located on chromosome 15. The DNA in this region encodes the UBE3A protein, which is essential for normal neurological development^[2]. Understanding these genetic processes can help in the development of potential therapies for such disorders^[3].

Dose

In the context of medical treatment and clinical trials, a dose refers to the specific quantity of a therapeutic agent, such as a drug or medicine, that is administered at one time or over a period of time. The dose is a critical aspect of treatment, as it can significantly impact the effectiveness and safety of the therapy.

However, it’s important to note that there isn’t a single “correct” dose for every patient. Instead, there is often a range of acceptable doses, with a starting dose and a range of doses that can be adjusted based on individual patient responses^[1]. This concept is particularly relevant in the treatment of heterogeneous populations, such as those with Angelman Syndrome, where each patient may respond differently to the same dose of a drug^[1].

In clinical trials, the process of determining the appropriate dose often involves a systematic approach where different dose levels are tested in small groups of individuals. This is typically done in a stepwise manner, starting with a low dose derived from animal studies and gradually escalating to higher doses. This process, known as an ascending dose trial, allows researchers to assess the safety and efficacy of each dose level^[2][3].

In some trials, the process of dose titration, or the adjustment of the dose based on individual patient responses, is built into the study design. This approach allows for the optimization of the dose for each patient, which can help maximize efficacy and minimize safety risks^[1]. For example, in a trial for Angelman Syndrome, patients starting in the lowest dose cohorts were individually titrated up to higher doses until a certain level of efficacy was achieved^[4].

It’s also worth noting that the dose of a drug can be administered in different ways, such as a single dose or multiple doses over a period of time. The choice between a single dose (SAD) or multiple ascending doses (MAD) depends on the nature of the drug and the specifics of the trial design^[3].

In conclusion, the dose is a crucial aspect of medical treatment and clinical trials, and it often requires careful adjustment and optimization based on individual patient responses. This is particularly true in the treatment of heterogeneous populations, where the optimal dose can vary significantly between patients.

Drug development

Drug development is a complex, multi-step process that involves the discovery, testing, and approval of new therapeutic substances. It begins with basic research, where potential targets for the drug are identified. In the case of Angelman Syndrome, the target is the UBE3A gene^[1]. The next step is to decide on the approach to take and the protein to focus on. For Angelman Syndrome, most researchers in the antisense oligonucleotide (ASO) world focus on the UBE3A antisense strand on the paternal gene^[1].

Once the lead candidates are optimized, the process moves into the preclinical research phase. Here, the drug is tested in different animal species to ensure safety and efficacy before it is administered to humans^[1]. This phase also involves pharmacodynamics (studying if the drug works as anticipated), biodistribution or pharmacokinetics (studying where the drug goes in the body), toxicology (testing if the dose levels are safe), and genotoxicity (studying if there are any toxicities to the genome)^[2].

The next phase is the clinical development phase, which involves several stages and can take a long time. The drug is tested in clinical trials, and data is collected to show that it is safe and effective in treating the disease^[1]. The clinical trials are usually divided into Phase 1, Phase 2, and Phase 3 trials, each with increasing numbers of participants and complexity^[3].

Once enough data is gathered, it is filed with the Food and Drug Administration (FDA) for review. If the FDA determines that the drug is safe and beneficial for patients, it is approved and made available to the broader population^[1]. However, it’s important to note that the process can be different for rare diseases. Often, drug approvals can be obtained with a smaller patient database if there are sensitive markers and good outcomes. In such cases, the FDA may grant a conditional approval^[4].

The drug development process is not only time-consuming but also expensive. For every 15,000 drugs in development, only about 5,000 may go through regulatory rigor to get to a clinical trial, and of those, only 10 may get into a clinical trial for one approval^[5]. The cost of research can range from half a million to $2 million^[5]. To encourage research in rare diseases, the FDA has implemented economic incentives like seven years of market exclusivity, tax incentives for R&D, and eligibility for fast-tracking FDA review^[6].

In summary, drug development is a rigorous and complex process that involves multiple stages of research, testing, and regulatory approval. It requires significant investment of time and resources, but it is crucial for the discovery and implementation of new treatments for diseases like Angelman Syndrome.

Drug discovery

Drug discovery is a complex, multi-step process that begins with basic research and ends with the approval of a drug for use in patients. The process starts with identifying a target for the drug, such as a specific gene or protein. In the case of Angelman Syndrome, the target is the UBE3A gene^[1][2].

The next step is early discovery, where researchers focus on optimizing lead candidates. This involves refining the drug to improve its efficacy and safety profile. The drug is then tested in different animal species during the preclinical research phase. This is a crucial step to ensure the drug’s safety and effectiveness before it is administered to humans^[1][2].

Once the drug has passed preclinical testing, an Investigational New Drug (IND) application is filed. If approved, the drug moves into the clinical development phase, which involves several stages of human clinical trials. These trials are designed to gather data on the drug’s safety and effectiveness in treating the disease^[1][2].

Clinical trials are divided into different phases. The initial phases focus on safety and exploratory efficacy, while later phases aim to determine if the drug is working sufficiently for approval^[3]. During these trials, researchers also study the pharmacodynamics (how the drug works), pharmacokinetics (where the drug goes in the body), and toxicology (safety of the drug at different dose levels)^[4].

After the clinical trials, the collected data is filed with the Food and Drug Administration (FDA) for review. If the FDA determines that the drug is safe and beneficial for patients, it is approved and made available to the broader population^[1][2].

It’s important to note that even after a drug is approved, additional studies may be conducted to collect more safety data and answer any additional questions the FDA may have^[2].

The drug discovery process is a lengthy and rigorous one, involving numerous stages of research and testing. It requires a significant investment of time and resources, with the ultimate goal of developing safe and effective treatments for diseases like Angelman Syndrome.

EEG

An electroencephalogram (EEG) is a non-invasive test that records electrical patterns in the brain, which are crucial in diagnosing conditions such as epilepsy and sleep disorders. In the context of Angelman Syndrome, EEGs have been used to identify characteristic brain activity patterns and evaluate the effects of therapeutic interventions^[1][2].

Brain waves, which are recorded by EEGs, are divided into five main bands: Delta (1-4Hz), Theta (4-10Hz), Alpha (8-12Hz), Beta (12-30Hz), and Gamma (>30Hz). Each of these bands is associated with different cognitive states and functions. For instance, Delta waves are the slowest and are mainly seen during sleep in neurotypical brains, while Gamma waves are associated with focused attention and motor task execution^[3].

In Angelman Syndrome patients, EEGs have revealed a distinctive increase in Delta rhythm, which is visible even to the untrained eye^[1]. This Delta rhythm is of particular interest in therapeutic development, as researchers are keen to understand whether interventions can cause a shift in this peak^[1].

Recent studies have shown promising results, with EEGs being used as a tool to measure changes in brain activity in response to therapeutic interventions. However, the interpretation of these changes is limited, and further research is needed to correlate EEG changes with functional outcomes such as motor function, sleep, seizures, cognition, or communication^[2].

In clinical trials, EEGs have been used to monitor changes in brain activity following therapeutic interventions. For instance, in the HALOS clinical trial, a majority of patients showed a reduction in slow wave Delta activity and an increase in Theta activity, suggesting an improvement in EEG and a correlation with functioning on clinical measures^[4][4].

Despite its usefulness, the process of getting an EEG, which involves the placement of 21 electrodes on the scalp, can be uncomfortable and is often met with complaints from patients^[5]. Nonetheless, EEGs continue to provide valuable insights into the brain activity of Angelman Syndrome patients and play a crucial role in the development and evaluation of therapeutic interventions.

Enzyme

An enzyme is a type of protein that acts as a catalyst in various biological functions, speeding up chemical reactions that take place in cells. Enzymes play a crucial role in processes such as digestion, DNA synthesis, and energy production. They work by reducing the amount of energy required for a reaction to occur, effectively enabling the reaction to proceed more quickly and efficiently.

Enzymes are highly specific, meaning each enzyme is designed to facilitate a particular reaction. They achieve this specificity through their unique three-dimensional structures, which create a specific active site. This active site is where the enzyme binds to the substrate (the molecule it acts upon) and carries out its catalytic function.

In the context of genetic disorders like Angelman Syndrome, the role of enzymes becomes particularly significant. Angelman Syndrome is caused by the loss or dysfunction of a specific enzyme called UBE3A. This enzyme is crucial for normal neural activity, and its loss interferes with the brain’s ability to use environmental experience ^[1].

Research into Angelman Syndrome has explored various therapeutic strategies that involve enzymes. For instance, enzyme replacement therapy is being investigated as a potential treatment. This approach involves delivering the missing or dysfunctional enzyme directly into the brain, with the hope that it could restore some level of normal function ^[2][3].

In summary, enzymes are crucial biological catalysts that play a key role in many cellular processes. Their importance is highlighted in conditions like Angelman Syndrome, where the loss or dysfunction of a specific enzyme leads to disease, and where therapeutic strategies often involve attempts to replace or reactivate the missing enzyme.

FDA

The Food and Drug Administration (FDA) is a federal agency in the United States that is responsible for protecting public health by ensuring the safety, efficacy, and security of human and veterinary drugs, biological products, and medical devices. The FDA also oversees the safety of the nation’s food supply, cosmetics, and products that emit radiation^[1].

The FDA was formed in 1906 following public outcry over unsanitary and unsafe food manufacturing practices highlighted in Upton Sinclair’s novel, “The Jungle”. Over time, the FDA’s authority has evolved in response to various public health crises and advocacy efforts. For instance, in 1938, the FDA was granted more powers over the safety of drugs following an incident where an improperly prepared elixir led to 100 deaths. In 1962, the FDA gained authority over drug safety and efficacy in response to the thalidomide crisis, where a drug given to mothers for morning sickness in Europe caused birth defects^[1].

The FDA’s role has further expanded to speed up the drug development process, particularly in response to the HIV/AIDS crisis. This led to the creation of the Prescription Drug User Fee Act (PDUFA), which allows drug manufacturers to pay fees to the FDA to expedite the drug development process. This act is renewed every five years, providing opportunities to make adjustments to the FDA’s processes^[1].

The FDA’s responsibilities also extend to the regulation of medical foods and dietary supplements. Medical foods, which are used under a physician’s supervision, are not drugs but specialized foods designed for specific disease populations. These products have some FDA oversight and require a higher level of proof for safety^[2].

The FDA’s decision-making process involves a comprehensive review of various factors, including drug quality, safety data from animal studies, and the clinical plan for patient studies. The FDA ensures that the patient population for the study is appropriate, safety measures are in place, and relevant aspects are being measured in the study^[3].

In recent years, the FDA has also launched the patient-focused drug development initiative, which allows for direct engagement with patients and families to understand their lived experiences and treatment preferences. This initiative helps inform both drug development and review processes^[1].

Fine motor skills

Fine motor skills refer to the coordination of small muscle movements which occur in body parts such as the fingers, usually in coordination with the eyes. These skills are essential for performing everyday tasks such as eating, writing, buttoning clothes, turning pages, and using computer keyboards or mobile devices. Fine motor skills also involve the strength, dexterity, and coordination of the small muscles in the hands and wrists.

In the context of Angelman Syndrome, fine motor skills can be significantly affected. Individuals with Angelman Syndrome may struggle with tasks that require fine motor control, such as uttering words smoothly or coordinating the movements of the mouth and vocal cords^[1]. This can make tasks like eating, dressing, or using a computer more challenging.

Motor planning, which involves the ability to conceive, plan, and carry out a motor action, is also a crucial aspect of fine motor skills. This concept is often used in therapeutic settings to help individuals with Angelman Syndrome improve their motor skills. For example, therapists may use task analysis, which breaks down activities into basic categories like gross motor, fine motor, visual motor, and social function, to help individuals improve their motor skills^[2].

Motor planning is also important in the use of augmentative and alternative communication (AAC) systems, which can help individuals with Angelman Syndrome communicate more effectively. Consistent vocabulary placement in AAC systems can support motor planning, as the body learns where things are because they don’t move around, change shape or size, and the button is always in the same place on every page^[3].

Research on Angelman Syndrome also involves the measurement of fine motor activity. For example, in clinical trials, questionnaires about movement are used to assess fine motor activities. These assessments rely heavily on observations and interpretations of caregivers, making them an integral part of the study^[4].

In conclusion, fine motor skills are crucial for performing everyday tasks and can be significantly affected in individuals with Angelman Syndrome. Therapies and interventions, such as task analysis and AAC systems, can help improve these skills and enhance the quality of life for individuals with this condition.

Fragile X

Fragile X syndrome is a genetic disorder that causes intellectual disability, behavioral and learning challenges, and various physical characteristics. It is the most common known single-gene cause of autism and inherited cause of intellectual disability among boys. The syndrome results from a mutation in the FMR1 gene on the X chromosome, which leads to a deficiency or absence of the FMRP protein that is necessary for neural development.

The severity of Fragile X syndrome symptoms can vary from mild to severe, and can include cognitive impairment, anxiety, hyperactivity, attention deficit disorder, mood swings, and autistic behaviors such as hand-flapping and not making eye contact. Physical features might include large ears, long face, soft skin, and large testicles (in post-puberty males).

Fragile X syndrome is a life-long condition, but it does not affect life expectancy. There is currently no cure for Fragile X syndrome, but there are various treatments available to help manage symptoms, including behavioral therapy, special education, and, in some cases, medication.

Research into Fragile X syndrome has provided valuable insights for other genetic disorders, including Angelman syndrome. For instance, studies on Fragile X have helped develop and validate certain tests like the NIH Toolbox Cognitive Battery and the KiTAP Executive Function Test, which have been adapted for use in Angelman syndrome research^[1]. However, it’s important to note that translating treatments from animal models to humans has been challenging, as animal models don’t always predict human responses^[2].

Moreover, the Fragile X community has experienced issues with clinical trials, such as bias and variability in reported measures, and the impact of social media on placebo responses^[2]. These lessons from the Fragile X field can be applied to Angelman syndrome research to avoid similar pitfalls.

GABA receptor

GABA receptors are a class of receptors that respond to the neurotransmitter gamma-aminobutyric acid (GABA), the chief inhibitory compound in the mature vertebrate central nervous system. They play a crucial role in reducing neuronal excitability throughout the nervous system. In humans, GABA receptors are categorized into two main classes: synaptic GABA receptors and extra-synaptic GABA receptors^[1].

Synaptic GABA receptors mediate phasic excitation. They are located at synapses, the junctions where neurons communicate with each other. When a neuron is activated, it releases GABA into the synapse. The GABA molecules then bind to the synaptic GABA receptors, activating them and causing a response in the receiving neuron^[2].

Extra-synaptic GABA receptors, on the other hand, mediate a different kind of neural activity known as tonic inhibition. These receptors are located outside of synapses and are continuously activated by low concentrations of ambient GABA. This continuous activation helps to regulate the overall excitability of neurons^[1].

In the context of Angelman Syndrome, a neurodevelopmental disorder, the function of GABA receptors is of particular interest. The loss of the UBE3A gene function in Angelman Syndrome leads to a buildup of GABA transporters, which may result in a relative deficiency of GABA in the extrasynaptic space. This could lead to a loss of activation of the extrasynaptic receptor and not enough tonic inhibition^[3]. This loss of tonic inhibition has been proposed to be a fundamental mechanism underlying many of the symptoms of Angelman Syndrome, such as seizures, decreased need for sleep, hyperactivity, and anxiety^[4].

Among the GABA receptors, GABAA α5 receptors are particularly important. These receptors are affected in Angelman Syndrome deletion genotype, and any dysfunction around this receptor has been linked with many neurodevelopmental disorders and with epilepsy^[5]. Therapies that selectively enhance the GABAA α5 receptor function, such as Alogabat, are being explored as potential treatments for Angelman Syndrome^[6].

Gaboxadol

Gaboxadol, also known as OV101, is a small molecule that was derived from Muscimol, a naturally occurring compound isolated from the mushroom, Amanita muscaria^[1]. It is an oral medication that selectively works on extrasynaptic GABA receptors, which are located outside the synapse, the very narrow space between two neurons where they communicate via neurotransmitters (chemical messengers)^[1].

Gaboxadol is believed to restore tonic inhibition, a balance between the GABA and glutamate systems in the brain^[2]. GABA is one such messenger that mediates inhibitory neurotransmission or tonic inhibition, i.e., it dampens down excessive activity^[1]. Gaboxadol is thought to be the only drug which selectively acts on the extrasynaptic receptor population, and hence is different from other GABAergic medicines that families may be familiar with such as benzodiazepines (valium, clobazam, clonazepam, etc.), zolpidem (Ambien), anesthetic agents, and several anti-epileptic agents^[1].

Gaboxadol was being developed as a potential treatment for Angelman Syndrome, a genetic disorder that causes developmental disabilities and neurological problems^[1]. The drug was thought to address one of the changes that happen when the UBE3A gene is lost in Angelman Syndrome patients. The loss of the UBE3A gene leads to a deficiency of one of the compounds in the brain that’s responsible for communication between neurons^[2].

In mouse models of Angelman syndrome, Gaboxadol showed measurable improvement, particularly in motor function and ataxia^[1]. However, in clinical trials, the development of Gaboxadol was ceased for Angelman syndrome because the compound failed to show efficacy^[3].

Despite this, Gaboxadol has been trialed in over 3000 adults, predominantly in patients with primary insomnia, showing that it was generally safe^[1]. It has also been noted to give all the positive effects of alcohol, but it actually reduces the negative feelings^[4].

In conclusion, Gaboxadol is a unique molecule that acts on extrasynaptic GABA receptors and was being developed as a potential treatment for Angelman Syndrome. Despite its failure in clinical trials for this specific syndrome, it has shown promise in other areas and its safety profile has been assessed in a large number of adults^[1].

Gait

Gait refers to the pattern or manner of walking. It involves the coordination of various body parts, including the legs, feet, arms, and trunk. The study of gait and its abnormalities is crucial in diagnosing and managing various neurological, orthopedic, and physical conditions. In the context of Angelman Syndrome (AS), gait analysis has been used to understand the unique walking patterns exhibited by individuals with this condition.

Angelman Syndrome is a genetic disorder that affects the nervous system, causing severe physical and learning disabilities. One of the common concerns in individuals with AS is movement disorders, including spasticity, ataxia, tremor, and muscle weakness. Over time, individuals may develop a crouched gait, which can cause a progressive decline in mobility^[1].

Gait analysis in AS has been conducted using various methods. In earlier studies, researchers used techniques such as painting the feet of mice and observing their walking patterns^[2]. However, with advancements in technology, more sophisticated systems like DigiGait have been employed. DigiGait is a computerized system that measures various aspects of gait, providing clear and concise data^[2].

In AS, gait analysis has revealed some unique characteristics. For instance, AS rats were observed to have a wider gait, with their paws turned in an unusual direction. They also tended to have three paws down at one time, which might be a way to help with balance^[2]. In human patients, gait analysis has shown a significant difference in the width of stance between AS patients and typical age-matched patients. Interestingly, when compared with children having other intellectual disorders associated with gait disorder, AS patients’ gait parameters were found to be more similar to those of individuals with ataxia^[3].

Gait analysis can also be used as an outcome measure in AS. For instance, a gait score has been developed to quantify the changes in gait and evaluate the effectiveness of therapeutics^[3]. This approach provides a more objective and quantifiable measure compared to subjective observations of whether a patient is walking or moving better.

In conclusion, gait analysis is a valuable tool in understanding the unique walking patterns in Angelman Syndrome and evaluating the effectiveness of therapeutic interventions. It provides objective, quantifiable data that can help in the management and treatment of this condition.

Gene

A gene is a fundamental unit of heredity and a specific segment of DNA that encodes a protein product. It is essentially an instruction manual for the cell, containing the information needed to build and maintain an organism’s cells and pass genetic traits to offspring^[1].

The DNA within a gene is transcribed into messenger RNA (mRNA), which is then translated to produce a protein. The protein is the functional component that carries out various tasks within the cell^[2].

Genes are composed of coding and non-coding parts, known as exons and introns, respectively. The exons are the coding parts that contribute to the final functional protein, while the introns are the non-coding parts that are removed during the process of gene modification^[3].

In the context of genetic disorders, a mutation or problem in a gene can lead to a problem with the corresponding protein, affecting the normal functioning of cells. For instance, in Angelman syndrome, there is a lack of the UBE3A gene, which affects the production of the UBE3A protein^[1].

Gene therapy techniques aim to correct these genetic problems by introducing a functioning gene into the cell. This can restore the cell’s ability to produce the necessary protein and return to normal functioning^[1]. Various methods are used to deliver the gene into the cell, including the use of adeno-associated viruses (AAVs), which are very good at recognizing specific cell types^[4].

Gene editing technologies, such as CRISPR, can also be used to modify the DNA of the desired organism. CRISPR, short for Clustered Regularly Interspaced Short Palindromic Repeats, is a gene editing technology that can target and cut specific sequences of DNA, allowing for precise modifications to the genome^[5].

In summary, a gene is a segment of DNA that encodes a protein and plays a crucial role in the functioning of cells and the inheritance of traits. Understanding genes and their functions is fundamental to the field of genetics and the development of gene therapies for various genetic disorders.

Gene expression

Gene expression is a complex process that involves the conversion of genetic information from a gene into a functional product, typically a protein. This process is regulated by the cell and can be influenced by various factors, both internal and external. The process of gene expression begins with the transcription of DNA into RNA, followed by the translation of RNA into a protein.

In the context of Angelman Syndrome, the UBE3A gene plays a crucial role. This gene, like all genes, is composed of coding and non-coding parts, known as exons and introns respectively. When a gene is expressed, it is modified and the non-coding parts are removed^[1].

The expression of genes can vary between different cell types. For instance, a nerve cell and a muscle cell express different proteins, which is what differentiates them. Some genes are expressed in certain cells and not in others. For example, a neuron does not need to express liver enzymes, so the cell turns off those liver enzyme genes^[2].

The regulation of gene expression is also influenced by epigenetics, which involves chemical modifications to proteins that are wrapped around the DNA. These modifications constitute an ‘epigenetic code’ that can determine whether a gene is active or silenced^[2].

In the case of Angelman Syndrome, research has been conducted to artificially activate the UBE3A gene. This involves using techniques such as gene therapy, where a virus is used to deliver a gene into the body. This gene can then be expressed in specific cells, such as neurons, through the use of promoters, which are DNA segments that regulate gene expression^[3].

Another approach involves the use of CRISPR activation (CRISPRa) to upregulate existing gene copies. This method takes advantage of the gene’s own regulatory machinery, making it a highly specific approach^[4].

Furthermore, research has also explored the concept of ‘cross-correction’, where a protein expressed by a vector-treated cell can be secreted and taken up by an adjacent cell that has not been vector-treated. This allows for a broader effect based on the amount of vector delivered^[5].

In summary, gene expression is a complex process that is crucial for the functioning of cells and the development of organisms. Understanding and manipulating this process is key to developing treatments for genetic disorders such as Angelman Syndrome.

Gene Therapy

Gene therapy is a promising approach to treating diseases by transferring corrective genetic material to a patient, particularly those with monogenic diseases where a single gene is defective^[1]. This therapeutic approach aims to correct disease-causing mutations by altering the genes involved, potentially alleviating the symptoms of the genetic disease and possibly offering a cure^[1].

The process of gene therapy involves delivering the therapeutic genetic material into the patient’s cells. This genetic material is typically delivered by modified viruses that cannot replicate or cause disease^[1]. These viruses act as a vehicle, delivering the genetic material that enables the cells to produce a functional protein^[1]. The gene needs to be translated into a protein, which is the functional unit, in order to alleviate the symptoms of the disease^[1].

There are different approaches to gene therapy, including the addition of a healthy gene to compensate for a mutated gene that causes loss of function^[1]. Another approach is gene editing, where the DNA in the living cell is changed. This can be achieved through advances like CRISPR, which can mutate or repair DNA in particular places^[2].

Gene therapy can be delivered through both viral and non-viral vectors. Non-viral methods include direct injection or transfection of DNA or delivery using a non-viral encapsulation, often using something called a liposome^[1]. Viral approaches use viruses that have had their viral DNA engineered or removed to prevent the virus from replicating and causing disease. The virus is then used as a carrier to deliver the therapeutic transgene into the cell^[1]. One such viral vector used in gene therapy is the adeno-associated virus (AAV), which is a small, single-stranded DNA, non-pathogenic virus^[1].

Gene therapy has seen significant progress over the past three decades, with over 2,500 clinical studies initiated since 1990^[1]. The progress has moved from initial trial failures to successes, particularly with monogenic diseases^[1]. As of 2020, there were about six diseases being treated with gene therapy, with many more in the pipeline^[2].

It’s important to note that gene therapy is a therapeutic category under which there are several different programs led by different institutions and companies. Each program may have different profiles of efficacy and safety, and may be suitable for different genotypes^[3].

Geneticist

A geneticist is a scientist who specializes in the study of genes, heredity, and variation in living organisms. This field of study, known as genetics, involves the examination of DNA (deoxyribonucleic acid), which contains all of the instructions for life^[1]. Geneticists can work in various areas, including research, clinical practice, and counseling.

In research, geneticists may study the genetic composition of species, the inheritance of traits, or the variation and distribution of genes in populations. They may also work on developing and applying genetic technologies, such as gene editing tools like CRISPR, to understand and potentially change our own genetics^[2].

In clinical practice, geneticists often work in healthcare settings, diagnosing and treating genetic disorders. For example, they may work with patients with Angelman Syndrome, a genetic disorder that affects the nervous system^[3]. They may also provide genetic counseling to individuals and families, helping them understand their risk for certain genetic conditions.

In the context of Angelman Syndrome, geneticists play a crucial role in understanding the unique characteristics of the UBE3A gene, which is implicated in the disorder. They study how this gene is regulated and how its unique properties can be leveraged to develop therapeutic approaches^[4].

Geneticists also play a role in the development of clinical trials and the creation of new therapeutics for genetic disorders. They help design and implement trials, monitor patient outcomes, and analyze data to assess the safety and efficacy of new treatments^[1].

In summary, a geneticist is a scientist who studies genes and their role in the inheritance of traits and diseases. They can work in various settings, from research laboratories to clinical practice, and their work is crucial in understanding and treating genetic disorders like Angelman Syndrome.

Genetics

Genetics is a branch of biology that studies genes, genetic variation, and heredity in organisms. It is fundamentally concerned with how traits and characteristics are transmitted from parents to offspring. The genetic information is stored in units of heredity known as genes, which are segments of DNA (deoxyribonucleic acid) located on chromosomes^[1].

Each human cell contains 23 pairs of chromosomes, with one set of 23 chromosomes inherited from the mother and the other set from the father^[2]. These chromosomes are essentially linear pieces of DNA^[3]. If you were to unravel the DNA from every chromosome in a single cell and lay it all out end to end, you’d have about two meters worth of genetic material^[1].

The DNA in our cells is organized into units of information called genes. These genes contain the instructions for making proteins, which are the functional components that carry out various tasks in the body^[2]. The process of converting the information in DNA into a functional protein involves two main steps: transcription and translation. During transcription, the DNA is copied into a molecule called messenger RNA (mRNA). This mRNA is then translated to produce a protein^[1].

In the context of genetic disorders like Angelman syndrome, understanding the genetics behind the condition is crucial for developing therapeutic approaches. For instance, the UBE3A gene, located on chromosome 15, is of particular interest in Angelman syndrome research^[2].

Advancements in genetics have also led to the development of gene editing technologies, such as CRISPR, which have the potential to correct genetic mutations and potentially cure genetic diseases^[4]. However, the application of these technologies, especially in humans, raises ethical and safety concerns that are currently the subject of ongoing discussions in the scientific community^[4].

In summary, genetics is a complex field that plays a crucial role in understanding the mechanisms of life, the causes of various diseases, and the development of potential treatments.

Genome

A genome is the complete set of genetic material present in an organism. It includes all the genes, which are segments of DNA that contain instructions for the production of proteins, the building blocks of the body’s structures and functions. Each cell in an organism contains a copy of the genome, which is stored in the nucleus of the cell^[1].

The genome is organized into structures called chromosomes. Humans have 23 pairs of chromosomes, with one set of 23 coming from the mother and the other set from the father. Each chromosome is a long, continuous strand of DNA. If the DNA from all the chromosomes in a single cell were unraveled and laid out end to end, it would measure about two meters^[1][2].

The DNA in the genome is composed of four types of molecules, or bases, represented by the letters A, C, G, and T. The sequence of these bases forms the genetic code, which is read by the cell to produce proteins. The process of reading the DNA and producing proteins involves transcribing the DNA into a molecule called messenger RNA, which is then translated into a protein^[1][2].

The genome is not only complex but also dynamic. It can change over time due to mutations, which can lead to diseases if they occur in genes that are crucial for normal body functions. For example, in Angelman Syndrome, a genetic disorder, there is a mutation in the UBE3A gene^[3].

However, the genome is not fully understood yet. There is still a lot to learn about how the DNA is packaged, how genes are expressed, and how the genome is organized. The study of the genome and its functions is a major focus of biological and medical research^[4].

In summary, the genome is a complex and dynamic system of genetic information that guides the development and functioning of an organism. It is stored in the form of DNA within the chromosomes in each cell’s nucleus. Understanding the genome is crucial for understanding life processes and for diagnosing and treating genetic diseases.

Genome editing

Genome editing, also known as gene editing, is a group of technologies that allow scientists to change an organism’s DNA. These technologies allow genetic material to be added, removed, or altered at particular locations in the genome. One of the most recent and widely used tools for genome editing is CRISPR-Cas9, which has revolutionized the field due to its precision and ease of use^[1].

CRISPR, short for Clustered Regularly Interspaced Short Palindromic Repeats, was first harnessed for gene editing in 2013 by scientists Dr. Jennifer Doudna and Dr. Emmanuelle Charpentier. The system originated in bacteria as an immune response to viral infections. When a virus infects a bacterium, the CRISPR system fights off the virus by creating a guide RNA (gRNA) that targets the viral DNA and cuts it into pieces. The system then saves a piece of the viral DNA for future reference, allowing it to fight off the same virus more effectively if it encounters it again. Scientists have modified this system to work in humans, plants, and other animals, enabling them to precisely target and modify specific sequences of DNA^[1].

In practice, the CRISPR-Cas9 system works by using a guide RNA to locate the specific sequence of DNA that needs to be edited. The Cas9 protein then cuts the DNA at the specified location. To repair the cut, the cell’s natural repair processes are used. Scientists can take advantage of this process by providing a desired sequence of DNA, which the cell will incorporate during the repair process, effectively editing the genome^[1].

The potential applications of CRISPR-Cas9 are vast, ranging from the creation of genetically modified organisms in research to the treatment of genetic diseases in humans. For example, in the context of Angelman syndrome, a genetic disorder, scientists are exploring the use of CRISPR-Cas9 to unsilence the normally silent copy of the UBE3A gene on the paternal allele of chromosome 15^[1].

However, the use of CRISPR-Cas9 in humans, particularly in embryos, has raised ethical and safety concerns. In 2015, the publication of a paper demonstrating the editing of the human genome sent shockwaves around the globe, leading to discussions about the ethics of germline gene editing and the passing of laws in some countries to regulate or ban the practice^[2]. Despite these concerns, there is significant pressure to advance the technology, particularly for the potential treatment of genetic diseases^[2].

It’s important to note that while CRISPR-Cas9 has been used successfully in many research settings, its use in clinical trials and treatments is still emerging. The first use of gene editing in a person occurred in 2017, and several clinical trials are currently underway^[3]. As the field continues to develop, it will be crucial to balance the potential benefits of genome editing with the ethical and safety considerations it raises.

Genotype

Angelman Syndrome is a genetic disorder that is primarily caused by abnormalities in the UBE3A gene located on chromosome 15^[1]. The term “genotype” refers to the specific genetic makeup of an individual, in this case, the specific genetic mutation or deletion that causes Angelman Syndrome. The genotype is responsible for the manifestation of the disorder, which is referred to as the phenotype^[1].

There are several genotypes associated with Angelman Syndrome. The most common is a large deletion, which accounts for approximately 70% of cases^[2]. This involves a significant portion of chromosome 15 being deleted, which includes the UBE3A gene. Other genotypes include a point mutation in the UBE3A gene, Uniparental Disomy (UPD) where an individual receives two copies of chromosome 15 from one parent and none from the other, and an imprinting defect where the UBE3A gene is present but not expressed. A newer genotype being studied is the UBE3A gain of function mutation^[2].

The genotype of Angelman Syndrome can influence the severity of the disorder. For instance, individuals with the deletion genotype generally present with more severe impairments than those with other genotypes^[3]. This is because the deletion genotype involves the loss of other genes beyond UBE3A that may contribute to the disorder’s pathophysiology^[3].

Understanding the genotype of Angelman Syndrome is crucial for developing therapeutics. Furthermore, understanding the genotype can also help in designing clinical trials and potentially tailoring treatments to specific genotypes^[4].

In conclusion, the genotype of Angelman Syndrome refers to the specific genetic abnormality causing the disorder. It plays a significant role in the manifestation of the disorder and the development of potential treatments.

GI

GI, or gastrointestinal, refers to the system of the body that includes the stomach and intestines. It is responsible for the digestion of food, absorption of nutrients, and expulsion of waste. In the context of Angelman Syndrome, GI issues are a common symptom and can significantly impact the quality of life of individuals with the condition.

Research has shown that a significant proportion of individuals with Angelman Syndrome experience some form of GI dysfunction. In a study involving over 160 patients, 86% had some form of GI dysfunction, with 72% experiencing constipation and 44% experiencing reflux^[1]. Another study involving 120 patients found similar results, with 86.5% experiencing GI symptoms, 72% having constipation, and 44% having reflux^[2].

The severity and type of GI issues can vary depending on the specific genetic subtype of Angelman Syndrome. For example, upper GI symptoms such as reflux and swallowing difficulties were found to be more common in individuals with deletions and uniparental disomy^[1]. Similarly, poor feeding as an infant was more common in children with deletions^[1].

The treatment of GI issues in Angelman Syndrome is largely symptomatic and can involve changes in diet. For example, increasing fluid intake and incorporating high fiber foods can help alleviate constipation^[1]. In some cases, certain foods may need to be avoided if they are found to cause sensitivity or allergic reactions^[1].

It’s also important to note that GI issues can have a broader impact on the health and development of individuals with Angelman Syndrome. For instance, GI problems can worsen brain-related symptoms, and addressing these issues can help improve neurological development^[1]. Furthermore, GI symptoms can also impact sleep, and treating these issues can help improve sleep and behaviors^[3].

In terms of research, the Clinical Global Impressions of Improvement (CGI-I) scale is often used to assess changes in symptoms, including GI issues, in individuals with Angelman Syndrome^[4]. This scale allows for individualized assessment, taking into account the unique presentation and symptom profile of each patient.

GPE

Glycine-Proline-Glutamate (GPE) is a tripeptide, which is a peptide consisting of three amino acids. It is derived from the N-terminal of Insulin-like Growth Factor 1 (IGF-1), a hormone that plays an important role in childhood growth and continues to have anabolic effects in adults^[1].

IGF-1 is an essential growth factor responsible for the development of synapses and cells. It is expressed early in development and peaks at around puberty. It is expressed by both neurons and glial cells. In the brain, IGF-1 is rapidly metabolized to a truncated form of IGF-1 called des(1-3)IGF-1, and GPE^[2].

GPE is biologically active and has several functions. It regulates microglia, which maintain and prune synapses as well as maintain signaling pathways. GPE is also potently anti-inflammatory. However, GPE is not particularly stable and is rapidly cleaved to cyclic Glycine-Proline (cyclic GP), which has some of the same functions of GPE in that it’s capable of regulating microglia and regulating inflammation at the cellular level^[2].

In the context of therapeutic development, GPE has been modified to create an analog called NNZ-2566, now known as Trofinetide. This modification involved adding a methyl group to make it less sensitive to degradation by proteolytic enzymes, which gives it oral bioavailability and a longer dwell time when administered^[1]. Trofinetide is currently in Phase 3 clinical trials for Rett syndrome and has completed Phase 2 trials for Fragile X syndrome^[1].

Another analog of GPE, known as NNZ-2591, is being developed as a potential therapeutic for Angelman syndrome, Phelan-McDermid syndrome, and Pitt-Hopkins syndrome. This compound is an analog of cyclic GP, a second-order metabolite from IGF-1^[1]. Phase 2 trials for this compound were expected to start in 2020^[1].

GTX-102

GTX-102 is an investigational antisense oligonucleotide (ASO) designed for the treatment of Angelman Syndrome^[1]. Antisense oligonucleotides are single-stranded synthetic molecules composed of DNA and RNA that target RNA to alter its expression and therefore protein production^[2].

In the context of Angelman Syndrome, GTX-102 is designed to target and inhibit the expression of UBE3A-AS^[1]. Angelman Syndrome is a genetic disorder characterized by developmental delay, balance issues, motor impairment, and debilitating seizures. It is caused by a missing or dysfunctional UBE3A maternal gene, and the paternal copy of this gene is typically silenced^[2].

GTX-102 works by activating the silenced paternal UBE3A gene, leading to the production of UBE3A protein^[2]. This reactivation of the paternal UBE3A gene has been associated with improvements in some of the neurological symptoms associated with Angelman Syndrome in animal models^[1].

The clinical trials for GTX-102, also known as the KIK-AS trials (Knockdown UBE3A Antisense In Kids with Angelman Syndrome), are designed as first-in-human studies involving four monthly doses of GTX-102^[3]. The trials involve dose escalation through multiple cohorts or groups, with each group starting at different doses and escalating within each group^[3]. The primary objective of these trials is to assess the safety of GTX-102, while the secondary objective is to understand how long GTX-102 lasts in the blood and cerebrospinal fluid^[4].

As of 2023, GTX-102 is still an investigational drug and is not approved by any regulatory authority. More work is required to definitively prove whether or not GTX-102 is safe and effective^[2]. However, it has been granted Orphan Drug Designation, Rare Pediatric Disease Designation, and Fast Track Designation from the U.S. Food and Drug Administration (FDA)^[1].

Hematopoietic stem cell transplant

A marrow transplant, also known as a hematopoietic stem cell transplant, is a medical procedure that involves the transplantation of hematopoietic stem cells, which are typically derived from bone marrow, peripheral blood, or umbilical cord blood. These cells are responsible for the production of all blood cells in the body, including the microglia that go to the brain, which can have an impact on disorders of the central nervous system^[1].

The process of a marrow transplant begins with the mobilization of the patient’s blood cells. A drug is administered to the patient to stimulate the stem cells to migrate out of the bone marrow and circulate into the blood. These cells can then be harvested through a process called apheresis, which involves connecting a vein to a machine that separates and collects the stem cells, specifically the CD34 stem cells^[2].

Once the stem cells have been collected, they are sent to a manufacturing facility where the gene therapy is inserted into them. This is done using a viral vector, which carries the correct gene that is to be made throughout the patient’s body^[1].

Before these gene-corrected cells can be reintroduced into the patient’s body, the patient must undergo a process called conditioning. This involves the administration of a chemotherapy drug, typically busulfan, for three days. The purpose of this is to reduce the number of blood cells in the bone marrow to make space for the new cells. It’s important to note that this process does not wipe out all of the blood cells or stem cells in the body, but merely reduces them to a level low enough to allow the new cells to engraft or grow and differentiate^[2].

After conditioning, the gene-corrected cells are transfused back into the body. These cells are capable of finding their way back to the bone marrow, where they will live for the rest of the patient’s life and continue to produce blood cells every day^[1].

It’s worth noting that there are two types of marrow transplants: allogeneic and autologous. Allogeneic transplants involve the transplantation of cells from a donor to a recipient, which can lead to complications such as graft-versus-host disease. Autologous transplants, on the other hand, involve the transplantation of the patient’s own cells, which have been corrected and given back to the patient. This type of transplant does not carry the risk of rejection or graft-versus-host disease^[3][1].

In the context of Angelman Syndrome, hematopoietic stem cell gene therapy is being developed as a potential treatment. This approach involves the use of the patient’s own bone marrow, which is corrected and given back to the patient, offering a potential cure for the condition^[1].

Hippocampus

The hippocampus is a crucial part of the brain that plays a significant role in the formation and storage of memories. It is a part of the medial temporal lobe, located behind our ears, and is involved in processing information about places, people, and things, as well as the time that binds together all these elements^[1]. This region of the brain is involved in what are known as declarative or episodic memories in humans. These are the memories that you can talk about, such as who you are, where you have been, who you met, what you did last week, what you did two years ago, and what is important in your life^[1].

The hippocampus is also involved in learning and memory processes. It is used to remember information and events, such as the details of a lecture or a meeting^[2]. The hippocampus communicates with many other regions in the brain to process this information and store longer memories^[1].

In terms of its structure, the hippocampus is lined with the cell bodies of neurons that form its structure. These neurons express the UBE3A protein, which is missing in the hippocampus of an Angelman Syndrome mouse model due to the maternal gene being turned off^[3].

The hippocampus is also involved in synaptic transmission, which is the communication between neurons. This communication can be studied through electrophysiology, a method that allows scientists to stimulate the presynaptic side of the neuron and observe how well the postsynaptic side understands that communication^[2]. This process is crucial for understanding the connectivity in the hippocampus and its role in learning and memory.

In the context of Angelman Syndrome research, the hippocampus has been a target for gene therapy. Researchers have used adeno-associated virus (AAV) to deliver the UBE3A gene to the hippocampus of an Angelman Syndrome mouse model, which resulted in the recovery of the UBE3A protein expression and improvement in learning and memory^[4][3].

HIV

HIV, or Human Immunodeficiency Virus, is a virus that attacks the body’s immune system, specifically the CD4 cells, often referred to as T cells. Over time, HIV can destroy so many of these cells that the body can’t fight off infections and disease, leading to the final stage of HIV infection, AIDS (Acquired Immunodeficiency Syndrome)^[1].

HIV is a blood-borne virus typically transmitted via sexual intercourse, shared intravenous drug paraphernalia, and mother-to-child during childbirth or breastfeeding. Once in the body, the virus targets the immune system and begins to replicate, damaging and killing the T cells in the process. This weakens the immune system, making the individual more susceptible to other infections and diseases^[1].

One of the key aspects of HIV infection is the virus’s reliance on a gene called CCR5 to infect T cells. Some individuals have natural mutations in the CCR5 gene that make their T cells resistant to HIV infection. In these cases, the virus is unable to enter the T cells and instead “bounces off” the cell surface^[1].

Research has been conducted to exploit this “Achilles heel” of HIV for therapeutic purposes. For example, a company called Sangamo Bioscience developed a method to artificially induce this mutation in T cells. This involved taking T cells from HIV patients, treating them in a dish to mutate the CCR5 gene, and then reintroducing them back into the patient. This approach, known as ex vivo gene editing, has shown promise in clinical trials and is considered one of the most promising approaches to treating HIV^[1].

It’s important to note that while this approach can make T cells resistant to HIV, it does not cure the disease. However, it can help to control the virus and prevent the progression to AIDS, improving the quality of life and lifespan for people living with HIV^[1].

HSC

Hematopoietic stem cells (HSCs) are a type of adult stem cell found in the bone marrow and blood. These cells are responsible for the formation of all types of blood cells, including red blood cells, white blood cells, and platelets^[1]. HSCs are unique in their ability to self-renew and differentiate into various blood cell lineages, making them a crucial component of the body’s immune system and overall health.

HSCs are typically collected from the bone marrow, cord blood collected after birth, or from the patient’s circulating blood using a mobilization agent^[1]. Once collected, these cells can be genetically modified ex vivo (outside the body) before being reintroduced into the patient’s body^[2]. This process is commonly used in bone marrow transplants and gene therapy procedures.

In the context of gene therapy, a working copy of a specific gene of interest is inserted into the HSCs using a viral vector. The genetically modified cells are then infused back into the patient’s body, where they home back to the bone marrow and continue to produce healthy blood cells for the rest of the patient’s life^[1]. This approach has been used successfully to treat certain genetic disorders, such as severe combined immunodeficiency (SCID)^[1].

In the case of Angelman syndrome, researchers are exploring the use of HSC gene therapy. The patient’s own HSCs are collected, genetically corrected, and then returned to the patient. This autologous hematopoietic stem cell therapy has the advantage of avoiding rejection, side effects, and graft versus host disease, which are common complications of allogeneic transplants (transplants using cells from a donor)^[1][3].

It’s important to note that while HSCs have the potential to differentiate into all lineages of blood cells, they do not become other types of cells, such as liver cells, vascular cells, or brain cells. However, they do produce microglia, a type of immune cell that resides in the brain, which is why HSC gene therapy has the potential to impact diseases that affect the brain^[1].

ICD

Imprinting center defects are a type of genetic mutation associated with Angelman Syndrome. This condition is characterized by the abnormal functioning of the imprinting center, a specific region of the genome that controls the expression of certain genes depending on whether they are inherited from the mother or the father^[1].

In normal circumstances, the UBE3A gene, which is critical for normal neurological development, is expressed from the maternal chromosome and silenced on the paternal chromosome. However, in cases of imprinting center defects, the cells fail to correctly read the genetic code on the chromosomes and do not recognize the maternal chromosome as such. As a result, the UBE3A gene is not activated on the maternal chromosome, leading to the symptoms of Angelman Syndrome^[1].

Imprinting center defects are one of several types of genetic mutations that can cause Angelman Syndrome. Others include uniparental disomy (UPD), where a child inherits two copies of chromosome 15 from the father instead of one from each parent, and deletions or mutations in the UBE3A gene itself^[2][3].

The impact of imprinting center defects on the behavior and development of individuals with Angelman Syndrome can vary. For instance, some research has found that individuals with UPD or imprinting center defects are more likely to exhibit certain behaviors, such as pinching, as they get older^[4]. However, more research is needed to fully understand the implications of these genetic differences.

It’s also important to note that the presence of an imprinting center defect can complicate the development of therapies for Angelman Syndrome. For example, strategies aimed at “stopping the stop” and reactivating the silenced UBE3A gene on the paternal chromosome could potentially result in an overexpression of UBE3A if both copies of the gene are present and silenced due to an imprinting center defect^[2].

In conclusion, an imprinting center defect is a type of genetic mutation that can cause Angelman Syndrome by preventing the proper expression of the UBE3A gene on the maternal chromosome. This defect, along with other types of genetic mutations, contributes to the complexity and diversity of Angelman Syndrome^[2].

IEP

In the US, an Individualized Education Plan (IEP) is a legal document that outlines the special education services a student with disabilities will receive. It is mandated by the Individuals with Disabilities Education Act (IDEA), a key legislation that governs all special education law in the United States^[1][2]. The IDEA was last reauthorized in 2004^[3].

The IEP is often referred to as the cornerstone of special education^[3][1]. It is a comprehensive document that details the who, what, where, when, why, and how of everything for a particular child^[3][1][2]. It provides the framework for what a Free Appropriate Public Education (FAPE) looks like in the Least Restrictive Environment (LRE) for that student^[1][2]. These terms, FAPE and LRE, are direct legal terminologies and are important to remember as they can look very different for each individual student^[2].

The IEP document typically includes identification and eligibility information, which usually appears on the first page. This section contains details such as the student’s address, phone numbers, relevant medical information, and the disability category under which the child has been evaluated for special education services^[3]. For children with Angelman Syndrome, there is usually no question about qualifying for special education services^[3].

Another important component of the IEP is the parent concerns section. This should be present in every IEP document and is a place where the parents’ concerns and ideas are documented^[3]. The law explicitly states that parents and family are equal members of the IEP process and decision-making team^[1].

The IEP is a living document and is not set in stone. It can be updated and revised as needed to best serve the student’s educational needs^[4]. The goal is to make the parents more comfortable advocating for their child and to be more active participants in the IEP meetings^[1].

IGF-1

Insulin-like Growth Factor 1 (IGF-1) is a growth hormone produced throughout the body, including the brain, and is responsible for the growth and development of neurons and supporting cells that help maintain neurons, such as microglia^[1]. IGF-1 is an essential growth factor responsible for the development of main synapses and cells^[2]. It is expressed early in development and peaks at around puberty^[2].

In the brain, IGF-1 is produced by the cells of the brain, particularly neurons and neuroglial cells, which are the resident immune cells within the brain^[3]. IGF-1 binds to the IGF-1 receptor on cells, triggering a range of activities related to metabolism and cellular signaling^[3].

IGF-1 is rapidly metabolized in the brain to a truncated form of IGF-1 called des(1-3)IGF-1, and GPE (glycine, proline, glutamate), which are the last three peptides on the molecule^[2]. Both IGF-1 itself and the truncated form are very active in the PI3K-Akt-mTOR, and RAS-MAPK-ERK signaling pathways in neurons^[2]. IGF-1 is one of the major regulators of synaptogenesis (the formation of synapses between neurons), as well as metabolism and protein synthesis^[2].

GPE, a metabolite of IGF-1, is also biologically active and regulates microglia, which maintain and prune synapses as well as maintain signaling pathways^[2]. GPE is also potently anti-inflammatory^[2]. However, GPE is not particularly stable and is rapidly cleaved to cyclic GP, which has some of the same functions of GPE in that it’s capable of regulating microglia and regulating inflammation at the cellular level^[2].

IGF-1 is also the effector molecule for growth hormone, making growth hormone work^[3]. When IGF-1, which is produced predominantly in the liver, in peripheral circulation, binds to the IGF-1 receptor on cells, it triggers a whole range of different activities related to metabolism and cellular signaling^[3].

In the context of therapeutic applications, synthetic analogs of IGF-1 metabolites have been developed. For instance, NNZ-2591 is a synthetic analog of the naturally occurring molecule, cyclic glycine proline (cGP), a metabolite of IGF-1^[1]. This synthetic analog has the same molecular structure as the naturally occurring molecule, with one small chemical change that makes the drug more amenable to be used as a medication^[1]. This means that the drug will act in the same way as the naturally occurring molecule, but can be used as a medication^[1].

IGF-2

Insulin-like growth factor 2 (IGF-2) is a protein that is part of a system known as the IGF insulin system. This system includes three proteins: insulin, insulin-like growth factor 1 (IGF-1), and insulin-like growth factor 2 (IGF-2). These proteins bind with different strengths to other proteins present on the surface of cells, known as receptors^[1].

IGF-2 is a growth factor that activates a number of changes in cells when it binds to another protein on the cells. The strength of this interaction is very important as it determines the type of changes that will occur in the cell^[1].

IGF-2, along with IGF-1 and insulin, can bind to other receptors in the system, although with less strength. This can activate other types of cellular responses. However, the strongest responses occur when these proteins bind to their own type of receptor^[1].

In the context of Angelman Syndrome, IGF-2 has been studied for its potential therapeutic effects. Research has shown that IGF-2 can reverse cognitive deficits, social interaction impairments, and repetitive behavior in models of autism spectrum disorder. It can also reverse cognitive deficits, repetitive behavior, and motor impairments in a mouse model of Angelman syndrome. These effects are achieved through the IGF-2 receptor^[1].

IGF-2 is also involved in long-term memory formation. If the cascades involving IGF-2 are manipulated, long-term memory formation does not occur. This gene expression happens in different cell types, including neurons and glial cells^[1].

In summary, IGF-2 is a protein that plays a crucial role in cellular changes, memory formation, and potentially in the treatment of conditions like Angelman Syndrome and autism spectrum disorder.

Imprinting

Genomic imprinting is a naturally occurring phenomenon in which one copy of a gene is turned off (silenced), and the other copy is active. This process is unique in that the parent of origin of the gene copy determines which one is on and which one is off. In other words, these chromosomes remember their sex and are expressed in a very specific way^[1].

This phenomenon is quite rare, with only about 100 genes in the genome subject to genomic imprinting^[1]. The exact reason for the existence of genomic imprinting is not fully understood. However, it is believed to be very important, as almost all imprinted genes are associated with a human disease^[2].

One of the genes subject to genomic imprinting is UBE3A, the gene that causes Angelman syndrome. In the case of UBE3A, the copy inherited from the father is typically turned off^[1]. This silencing of the paternal allele of UBE3A is found in all humans and is referred to as an imprinting effect^[3].

One theory suggests that genomic imprinting evolved to reduce the amount of protein made by the gene, referred to as the dosage model of genomic imprinting. The idea is that one allele will make about half as much protein as two alleles. This notion makes sense, especially since it’s known that too much UBE3A is associated with autism spectrum disorder^[2].

However, this theory was tested by the Dindot laboratory, which used various techniques to measure the levels of UBE3A in almost all organs of the human and mouse body. They found that imprinting does not reduce the dosage of UBE3A in neurons^[2].

In the context of Angelman syndrome, the loss of the maternal UBE3A protein is the predominant cause of the disease. Because of the imprinting effect, the paternal UBE3A gene is silenced. However, therapeutic approaches are being developed to reactivate the silenced paternal UBE3A gene to replace the lost maternal UBE3A protein^[3].

In summary, genomic imprinting is a complex and rare genetic phenomenon that plays a crucial role in certain diseases, including Angelman syndrome. Despite the lack of full understanding of why it exists, it provides unique opportunities for therapeutic interventions.

In vitro

“In vitro” is a term used in scientific research to describe experiments or procedures that are conducted outside of a living organism, typically in a controlled laboratory environment such as a test tube, petri dish, or cell culture. The term “in vitro” is Latin for “in glass,” reflecting the historical use of glass containers in laboratory experiments.

In the context of Angelman Syndrome research, in vitro methods are used in various ways. For instance, human neuronal cells can be grown in a lab, providing a valuable approach that has yielded significant data in the Angelman research space. These are known as 2-dimensional neuronal models. While much can be learned from cells growing in a dish, these cultured cells do not interact with each other to form the complex neuronal networks found in the actual human brain. Therefore, a way to understand and test this in a laboratory is needed – one that combines the complexity of tissues as they exist in a living organism (in vivo) with the simplicity and ease of cell culture in a lab (in vitro)^[1].

In vitro models can be used for high throughput screening, where many components can be tested simultaneously. This approach was used to identify potential therapeutic interventions for Angelman Syndrome, such as can and Topotecan, and to screen antisense oligonucleotides (ASOs) and CRISPR-Cas9 approaches^[2].

In the field of gene therapy, in vitro methods can be used in an ex vivo approach, where cells are taken from the patient and isolated. They are then treated with a vector in the lab, outside of the body. This allows for control over which cells come in contact with the vector. The treated cells are then put back into the body^[3][4].

However, in vitro methods have limitations. For instance, it can be challenging to ensure that once the treated cells are put back into the body, they get to the right place. Also, in vitro methods cannot fully replicate the complex interactions and environment within a living organism. Therefore, findings from in vitro studies often need to be validated through in vivo studies^[3][5].

In vivo

“In vivo” is a term used in scientific research to describe experiments or procedures that are conducted within a living organism, such as a human or an animal. This term is derived from Latin, where “in vivo” translates to “within the living”. In the context of medical and biological research, “in vivo” studies are crucial for understanding the effects of various treatments or interventions in a complex, living system, as opposed to isolated cells or tissues in a laboratory setting.

In the context of gene therapy for conditions like Angelman Syndrome, “in vivo” treatments involve the direct delivery of therapeutic genetic material into the person. This can be achieved through various methods such as injections into the muscle, bloodstream, or directly into the brain^[1]. For instance, in the case of neurodevelopmental disorders like Angelman Syndrome, there are several “in vivo” gene therapy options available, including global delivery through the bloodstream^[1].

In “in vivo” somatic cell editing, a gene editing tool like a nuclease is introduced into the person. This process is more complex as it involves dealing with the immune system and the fact that there are many cells in the body, some of which are packed into organs, while others are spread out, like in the blood^[2]. The first use of gene editing in a person was in 2017, and it is still in clinical trial^[2].

However, “in vivo” studies also present certain challenges. For instance, it is more difficult to control all variables as compared to in a culture dish. It is also not possible to select out the cells that got the right edit from the ones that got the wrong edit, and if something goes wrong, it is not possible to remove those cells^[3].

Despite these challenges, “in vivo” studies are essential for understanding the real-world effects of potential treatments and interventions, and they play a crucial role in the development of new therapies for conditions like Angelman Syndrome.

Inclusion and exclusion criteria

Inclusion and exclusion criteria are fundamental components of clinical trials, including those for Angelman Syndrome. They are the factors that determine who can or cannot participate in a specific study. These criteria are designed to ensure the safety of participants and the integrity of the data collected^[1].

Inclusion criteria are the factors that allow someone to participate in a clinical trial. These could include a range of factors such as age, genetic etiology, specific body weight, and seizure profile requirements^[2]. For instance, in the case of Angelman Syndrome, the inclusion criteria might specify that participants must be within a certain age range, have a specific genetic cause of the syndrome, or meet certain health conditions^[3].

Exclusion criteria, on the other hand, are the factors that prevent someone from participating in a trial. These could include health history, past treatments, and even geographical location^[3]. For example, in some Angelman Syndrome studies, individuals who are not ambulatory at all, have poorly controlled seizures, or have other illnesses that make it unsafe to participate in an investigational study, such as heart disease or lung disease, are excluded^[4].

It’s important to note that these criteria are not designed to exclude individuals unfairly, but rather to ensure the safety of the participants and the validity of the study results. For instance, if a study is investigating a drug’s effect on sleep, and a participant has no sleep problems, they would not contribute to the effect data, and thus might be excluded^[1].

The process of determining whether a potential participant meets the inclusion and exclusion criteria is called screening. Only after the informed consent has been signed can participants be recruited, screened, and if they are eligible, enrolled or take part in the study^[5][6]. It’s also important to note that a person can leave the study at any time during the trial^[5][6].

In conclusion, inclusion and exclusion criteria are essential for the safety of participants and the integrity of clinical trials. They help ensure that the right participants are selected for each study, which in turn helps produce reliable and valid results.

IND

An Investigational New Drug (IND) application is a critical step in the process of drug development and is necessary before a compound can be evaluated in human studies^[1]. The IND application is a comprehensive document that is submitted to the Food and Drug Administration (FDA) in the United States, or to the European Medicine Agency (EMA) in Europe, for review and approval^[2].

The IND application contains a wealth of information about the drug and the plan for its investigation. This includes details about the sponsor of the trial, the general plan or protocol for the study, an investigator brochure containing important information about the drug, information about the investigators running the study, and a summary of any existing data about the drug^[3].

In addition to this, the IND application also covers details about the manufacturing of the investigational drug, including its ingredients, how it is made, tested, and controlled, and information about its stability^[3].

Pharmacology and toxicology data from animal studies are also included in the IND application. These studies evaluate how the drug works, what it does to the body, how the body reacts to the drug, and its safety profile. The studies look at single doses and repeat doses of the drug, and aim to cover the duration of how long the drug will be administered in the early stage trial^[3].

The IND application is reviewed by the FDA or EMA, with the primary concern being whether it is safe to administer the drug to patients^[3].

IND-enabling studies, on the other hand, are preclinical studies that are necessary to allow a drug to enter the clinical research phase. These studies are designed to evaluate critical information related to toxicity, target engagement, off-target risks, and overall safety for human application^[4].

The IND-enabling studies are part of the translational research process, which involves taking a candidate drug from the animal model to human trials. These studies are often conducted in parallel to improve timelines, but this can also make them one of the most expensive parts of the drug development program prior to the clinical trial^[4].

Once the IND application is approved, the clinical trial can begin. The trial needs to start quickly after IND approval, with patient recruitment and dosing following soon after^[1].

In summary, the IND application and IND-enabling studies are crucial steps in the drug development process, providing the necessary safety and efficacy data to move a potential treatment from preclinical studies to human clinical trials.

iPSC

Induced Pluripotent Stem Cells (iPSCs) are a type of stem cell that can be generated directly from adult cells. They are created by reprogramming somatic cells, such as skin or blood cells, through the introduction of specific genes^[1]. This technique was developed about 10-15 years ago and was awarded a Nobel Prize in Medicine in 2012 due to its potential for future medical applications^[1].

iPSCs are pluripotent, meaning they have the ability to differentiate into many different types of cells. This is a key feature that makes them valuable for research and potential therapeutic applications. For instance, iPSCs can be converted into human neurons^[1]. They can also be used to create complex three-dimensional structures, such as brain organoids, sometimes referred to as “mini-brains”^[2].

In the context of Angelman Syndrome research, iPSCs have been used to create a biorepository of human neuronal cell lines^[3]. These cell lines are essential tools used to screen different therapeutic candidates for Angelman Syndrome. The biorepository contains all of the different genotypes of Angelman Syndrome, making it a collective location for researchers or industry partners to robustly and efficiently test different therapeutics^[3].

iPSCs are also used in the study of the role of glia cells in potential treatments for Angelman Syndrome. Researchers have developed an efficient way to create human oligodendrocytes from iPSCs, which can mimic natural development but much faster^[2]. This has led to the discovery that UBE3A, a gene that is often mutated in Angelman Syndrome, is active in the early stage of oligodendrocyte development and helps these cells grow and mature properly^[2].

In addition to their use in research, iPSCs also have potential therapeutic applications. For example, they are being used in clinical trials for diabetes, where the cells are made into pancreatic beta cells that produce insulin in response to the patient’s glucose load^[4].

In summary, iPSCs are a versatile tool in both research and potential therapeutic applications due to their ability to differentiate into many different types of cells and their potential for reprogramming. Their use in Angelman Syndrome research has provided valuable insights into the disease and potential treatments.

Isoform

A gene isoform refers to any of the different forms of a gene that can arise from alternative splicing of its pre-mRNA, or from the use of different promoter sites, or from different translation initiation sites. Each isoform codes for a different version of the protein known as a protein isoform. The existence of gene isoforms allows for a single gene to code for multiple proteins, thereby increasing the complexity and diversity of the proteome without increasing the number of genes.

In the context of Angelman Syndrome, the UBE3A gene, which is implicated in the disorder, is known to produce multiple isoforms. These isoforms are different versions of the UBE3A protein, and they may have different functions or be expressed in different cells or at different times^[1][2].

Research has been conducted to understand the role of these different UBE3A isoforms in the development of Angelman Syndrome. For instance, one study evaluated some of the shorter protein isoforms that have previously been less studied than the longer ones, with the hope that an analysis of these isoforms in the Angelman Syndrome mouse model will lead to additional understanding about the repertoire of cellular mechanisms that UBE3A can direct^[1].

Another study focused on how specific isoforms localize in the nucleus, cytoplasm, or in the synapse region. This research is important in understanding where UBE3A proteins operate in all compartments of the cell and it helps define areas for protein interactions which may lead to the development of new therapeutic strategies^[3].

In terms of therapeutic approaches, there has been consideration of using gene therapy to activate the paternal copy of the UBE3A gene rather than to put in a replacement gene. This is because the paternal copy of the gene is thought to behave much like the maternal copy, producing the right distributions of the right isoforms in the right times and places^[4].

In gene therapy experiments, different isoforms of UBE3A have been used, and the impact of these different isoforms on the symptoms of Angelman Syndrome in mouse models has been studied. These studies have shown improvements in some of the neurobehavioral abnormalities associated with Angelman Syndrome^[2][5].

In conclusion, understanding the role of different UBE3A isoforms in Angelman Syndrome is crucial for developing effective therapeutic strategies. The ability of a single gene to produce multiple isoforms adds a layer of complexity to the disorder but also opens up potential avenues for treatment.

Ketogenic diet

The ketogenic diet is a high-fat, low-carbohydrate diet that has been used for nearly a century to treat epilepsy, and more recently, has been explored as a potential treatment for other conditions, including Angelman Syndrome^[1]. The diet works by shifting the body’s metabolism from glycolysis, which uses glucose or sugar from carbohydrates, to ketosis, which uses fats and fat-based metabolites^[2].

In a typical diet, the majority of calories come from carbohydrates. However, in a ketogenic diet, the majority of calories come from fats. For example, in a very strict version of the ketogenic diet, the ratio of fats to other nutrients (proteins and carbohydrates) can be as high as four to one^[3]. This means that if you had five cups of food, four cups of it would be pure fat, and only one cup would contain some protein and a very small amount of carbohydrates^[1].

The ketogenic diet has been shown to have a significant impact on seizure control, even in cases where anti-epileptic medications have failed^[2]. It is believed that the diet may work by stabilizing the function of the mitochondria, the powerhouse of the cell, which may not function properly in conditions like Angelman Syndrome^[4].

However, the ketogenic diet is not without its challenges. It can be difficult to adhere to due to its restrictiveness and the significant dietary changes it requires. It also requires careful medical supervision and may necessitate the use of supplements to ensure nutritional needs are met^[5].

There are also variations of the ketogenic diet, such as the low glycemic index therapy and the modified Atkins diet, which also limit carbohydrates but are less restrictive than the classical ketogenic diet^[4]. These diets may be easier to follow and can serve as a transition to a more strict ketogenic diet if necessary^[6].

In the context of Angelman Syndrome, the ketogenic diet has shown promise in improving symptoms. For example, there have been documented cases of significant improvements in EEG readings of patients with Angelman Syndrome following the implementation of the diet^[2]. However, more research is needed to fully understand the potential benefits and challenges of the ketogenic diet in treating Angelman Syndrome.

Ketone

Ketones are natural compounds that are produced in our bodies during certain situations when our bodies are burning fat. This can occur during periods of calorie restriction, fasting, starvation, or when consuming a diet that is very high in fat^[1]. When the body does not have sugar/glucose/carbohydrates, it must find an alternative source of energy. When carbohydrate stores are used up, the body uses fat for energy. The byproduct of fat breakdown is ketone bodies, which include beta-hydroxybutyrate, acetoacetate, and acetone^[2].

Ketones are a very efficient energy substrate and can serve as an energy source for almost all the tissues in the body. Importantly, they can replace glucose as the brain’s primary fuel^[1]. This strategy is particularly effective in the brain, enhancing brain energy reserves when used as the primary source of fuel. Ketones can improve signaling throughout the brain and protect the brain as an anti-oxidant and anti-inflammatory^[2].

Ketones are also known to have anti-seizure and anti-convulsant effects, particularly acetoacetate and its derivative, acetone^[1]. This has led to research into the use of ketones, specifically ketone esters, for the treatment of conditions like Angelman Syndrome, which is characterized by seizures and cognitive deficits^[2].

Ketone supplementation can be achieved through diet or through the use of supplements like ketone esters. When taken as a supplement, ketones can cause a dose-dependent elevation in blood ketones, providing a sustained duration of elevated ketones^[1]. This has been shown to improve symptoms in conditions like Angelman Syndrome, including reducing seizure activity, improving motor function, balance, learning, and memory^[2].

In summary, ketones are energy-rich compounds produced by the body during fat metabolism. They can serve as an alternative energy source to glucose, particularly for the brain, and have potential therapeutic applications due to their anti-seizure and anti-convulsant properties.

Lentivirus

Lentiviruses are a class of viruses that belong to the retrovirus family, with HIV-1 being the most widely studied example^[1]. They are characterized by their RNA genome, which differentiates them from viruses like adeno-associated viruses (AAVs) that have a DNA genome^[1].

Lentiviruses are used in gene therapy, where they are engineered to replace the viral genes with a therapeutic gene needed by the patient^[1]. They have the ability to target both dividing and non-dividing cells, which is crucial for diseases like Angelman syndrome where the target is neurons, a type of non-dividing cell^[1].

One of the key features of lentiviruses is their moderate cassette size. Unlike AAVs, which are limited to about five kilobases of genetic material, lentiviruses can package up to eight kilobases^[1]. This larger packaging capacity allows for the delivery of larger genes, although there are still some genes that exceed this limit.

In the process of gene therapy, lentiviruses start with an RNA genome. To produce a functional gene product, the virus contains an enzyme called reverse transcriptase, which produces a copy of DNA (or cDNA) from the RNA template^[1]. This DNA then migrates into the nucleus of the cell, where it integrates into the host genome and provides long-term and stable gene expression^[1].

However, this process of integration can have unintended effects on the cell’s biology. The integration is random, meaning the DNA can insert anywhere in the host genome. While this allows for long-term stable expression and replication of the therapeutic genetic material as the cell divides, it also carries the risk of disrupting important genes and causing unintended consequences^[1].

In summary, lentiviruses are a type of retrovirus used in gene therapy for their ability to target both dividing and non-dividing cells and their larger packaging capacity compared to other viruses like AAVs. However, their method of integrating into the host genome can potentially lead to unintended effects on the cell’s biology.

LNA

Locked Nucleic Acid (LNA) is a type of RNA therapy that is being explored as a potential treatment for Angelman Syndrome. RNA therapies are molecules that bind to RNA, which is the substance that eventually makes protein, the building blocks of what happens in the cell. RNA therapies can reduce, modify, or increase gene expression^[1].

In the context of Angelman Syndrome, an LNA is a modified version of an antisense oligonucleotide (ASO) that modifies the expression of the UBE3A gene. The UBE3A gene is crucial in Angelman Syndrome as individuals with this condition have a genetic change on the maternal copy of this gene, which leads to a lack of UBE3A protein production. The LNA therapy works by activating the paternal copy of the UBE3A gene, which is present in the neurons but is kept silent. This activation leads to the production of the UBE3A protein in the brain^[1].

The LNA molecule is chemically modified with a locked nucleic acid, hence the name LNA. This modification enhances the properties of the molecule, making it a potent and safe candidate for clinical trials^[2].

In preclinical studies, the LNA molecule has shown promising results. In vitro experiments (experiments performed in cells) and in vivo experiments (experiments performed in non-diseased monkeys) demonstrated an increase in the UBE3A protein after the administration of the LNA molecule^[3]. However, it’s important to note that these results are preliminary, and the translation of these findings to clinical benefits for patients with Angelman Syndrome will need to be determined through future clinical trials^[1].

Roche was conducting the FREESIAS Study and the TANGELO study to further investigate the potential of the LNA molecule as a treatment for Angelman Syndrome^[2][4].

Lumbar puncture

A lumbar puncture, also known as a spinal tap, is a medical procedure frequently performed for diagnosis, anesthesia, and in medical emergencies^[1]. It involves the insertion of a needle into one of the spaces between the bones in the lower back^[1]. The needle is used to collect cerebrospinal fluid (CSF), a clear body fluid produced in the brain that surrounds the brain and spinal cord^[1]. The CSF serves to protect the brain, regulate the chemical environment of the nervous system, provide the brain with nourishment, and assist with waste product removal^[1].

In the context of Angelman Syndrome, lumbar punctures are used to administer drugs directly into the CSF, a method also known as intrathecal injection^[1]. This method bypasses the blood-brain barrier, a structure that often prevents the transfer of drugs from the blood into the CSF due to factors such as the size or charge of the drug^[1]. By injecting the drug directly into the CSF, it can travel up to the brain without having to pass through the blood-brain barrier^[1].

The procedure typically lasts about 30 minutes^[2]. To ensure the patient remains still during the procedure, the doctor may administer sedation or sleeping medication^[1]. The skin is carefully cleaned, and a numbing medication is given before the needle is inserted^[1]. After the drug is injected into the CSF, the needle is removed, and the skin is covered with a plaster^[1].

There are potential risks associated with a lumbar puncture. The most common side effects include headache, nausea, vomiting, dizziness, and ringing in the ears, which are typically caused by the leak of CSF after the procedure^[2]. Other possible side effects include low back discomfort or pain, infection, and bleeding at the site of the spinal tap^[2]. Some patients may also experience effects at the injection site, such as an infection where the needle was inserted, or tingling or pain down the legs^[3].

Despite these potential risks, lumbar punctures are generally considered safe and are a standard procedure in medical practice^[2]. The type of needle used for the procedure is an atraumatic needle, designed to gently separate the tissues rather than making a slice, which minimizes the risk of a leak at the site afterward^[4]. Lumbar punctures have been performed in over 11,000 patients, including adults, teenagers, children, and even newborn babies^[3].

Microglia

Microglia are a type of glial cell located throughout the brain and spinal cord. They are the primary immune cells of the central nervous system and play a crucial role in maintaining the health of the brain by removing damaged neurons and infections. Microglia are often referred to as the “constant gardeners” of the brain because they prune weak synapses and allow the strong synapses to grow, maintaining the balance and health of the brain’s connections^[1].

Microglia are also involved in the maintenance and management of neurons, the main cells that connect and send signals between different cells in the brain. They support the neurons by helping with the growth and management of the cells and the connections between them^[2].

In the context of Angelman Syndrome, microglia play a significant role. They are involved in the production of an essential growth factor called insulin-like growth factor one (IGF-1), which is important for creating new cells. When IGF-1 functions normally in the brain, it breaks up into smaller pieces, called metabolites^[2].

However, in neurodevelopmental disorders like Angelman Syndrome, there can be abnormal function of the microglia, leading to impaired signaling and an increase in inflammatory molecules. This can result in lower amounts or lower availability of IGF-1^[3].

One potential therapeutic approach for Angelman Syndrome involves the use of the compound NNZ-2591, which can normalize microglia and reduce the expression of inflammatory cytokines. This compound can also regulate the bioavailability of IGF-1, helping to correct both hyperconnectivity and hypoconnectivity in the brain^[1].

Another therapeutic approach involves gene modification of blood stem cells using a lentiviral vector that expresses UBE3A, the gene that is typically missing or non-functional in individuals with Angelman Syndrome. These modified cells can then be derived into immune system cells, including microglia, which can express UBE3A and deliver it to the affected neurons^[4].

In this approach, the microglia are not transferring the gene to neurons, but rather producing extra amounts of enzymes that work as a paracrine effect to correct the problems^[5]. This highlights the critical role of microglia in both the pathology and potential treatment strategies for Angelman Syndrome.

Molecular therapy

Molecular therapy is a type of treatment that targets diseases at the molecular level, specifically at the level of DNA and RNA. This approach is differentiated from drug therapy, which typically involves the administration of drugs over a lifetime to reduce the effects of a disease rather than curing it^[1]. Molecular therapy, on the other hand, aims to address the root cause of a disease, particularly genetic disorders, by targeting the genetic problem directly^[1].

In the context of Angelman Syndrome, a neurodevelopmental disorder caused by a deletion or mutation in the DNA, molecular therapy could involve techniques such as gene therapy, gene editing, and epigenetic editing^[1]. These techniques aim to fix or address the genetic problem causing the disease. For instance, gene therapy involves the addition of a functional gene to replace a non-functional or missing one, thereby restoring the production of the necessary protein^[2].

RNA therapies, a subset of molecular therapies, work by binding to the RNA, which is the molecule that eventually makes protein, the building blocks of what happens in the cell^[3]. Techniques such as short hairpin RNA (shRNA), microRNA, and antisense oligonucleotides (ASOs) work at the RNA level^[1]. These therapies aim to address the problem at the RNA level, which is one level up from the DNA^[1].

Molecular therapy has seen significant advancements in recent years. The first gene therapy was approved in the UK in 2012, and in the United States in 2017^[1]. Since then, there have been over 2,500 clinical studies using gene therapy initiated since 1990^[2]. These therapies have shown success particularly with monogenic diseases, where a single gene is responsible for the disease^[2].

In the case of Angelman Syndrome, molecular therapy approaches have shown promise. For instance, a study in 2011 successfully used adeno-associated virus in mice to replace the missing gene, rescuing various cognitive defects in adult mice with Angelman Syndrome^[4]. Another study demonstrated the potential of turning on the paternal copy of the gene or unsilencing it using a chemotherapeutic agent^[4].

In conclusion, molecular therapy represents a promising approach to treating genetic disorders like Angelman Syndrome by addressing the root cause of the disease at the DNA or RNA level. However, it’s important to note that while significant progress has been made, further research and clinical trials are needed to fully realize the potential of these therapies.

Molecule

A molecule is a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction. In the context of biological systems and Angelman Syndrome research, molecules play a crucial role in the functioning of cells and the expression of genes.

The central dogma of molecular biology, as explained by Dr. David Segal, involves the transformation of information from DNA to RNA to proteins^[1]. DNA, or deoxyribonucleic acid, is a long molecule that resides in the nucleus of the cell and is made up of four different kinds of subunits referred to as A, G, C, and T. These subunits interact with each other in a predictable way, forming a double-stranded molecule where one strand reinforces the sequence of these subunits on the other strand^[1].

RNA, or ribonucleic acid, is a molecule similar to DNA but slightly different. It carries the same sequence as the DNA and is responsible for making proteins. The process of making RNA from DNA is called transcription, and the process of making proteins from RNA is called translation^[1]. Proteins are the functional units of cells, acting as enzymes, structures, and signals. They are made up of amino acids and are responsible for various tasks within the cell, such as reading the RNA, signaling different parts of the immune system, and building structures like hair and nails^[2].

In the context of Angelman Syndrome, the UBE3A gene is of particular interest. The DNA in the chromosome contains the information to make UBE3A, which can be used to make an RNA that has the information to make the UBE3A protein^[2].

In drug development, small molecules are often used. These are compounds that have not been tested as drugs but are thought to represent all of the small molecular space that can be made up with certain combinations of atoms^[3].

In some cases, molecules can be chemically modified for delivery into cells, as in the case of the STE technology used for delivering Cas9-based machinery for gene disruption^[4].

In summary, molecules, whether they are DNA, RNA, proteins, or small molecules used in drug development, play a crucial role in the functioning of cells and the expression of genes, and are therefore central to the study and treatment of conditions like Angelman Syndrome.

Motor function

Motor function refers to the ability to move and control movements. In the context of Angelman Syndrome (AS), motor function is a critical aspect that significantly impacts not only the individuals living with AS but also their caregivers. Impaired motor function in AS can lead to safety concerns, such as falls and difficulty navigating various environments, which are common among individuals with this disorder^[1].

Motor function in AS encompasses several aspects, including gait, walking, climbing stairs, falls, running, and balance. These aspects have been identified as potential candidates to focus on as new clinical endpoints to assess for change in clinical trials in AS^[1].

Motor function also plays a significant role in communication systems for individuals with AS. For instance, motor planning, which is supported by consistent vocabulary placement, is a key aspect of both high-tech and non-electronic communication systems. This means that the body learns where things are because they don’t move around, they don’t change shape or size, the button is always in the same place on every page^[2].

Motor function is also crucial in academic learning for children with AS. It is a part of task analysis, which can be simplified into some basic categories such as gross motor, fine motor, visual motor, and relating or social function^[3].

In terms of treatment and therapies, motor function can be assessed and monitored using wearable technology. This technology can provide objective data on motor skills and help monitor the effectiveness of treatments and therapies. Caregivers generally view wearable devices positively^[1].

Moreover, motor function improvements have been observed in post hoc analyses of drug trials for AS. For instance, improvements in fine motor controls, such as being able to use a fork for the first time, have been reported^[4].

In conclusion, motor function is a critical aspect of Angelman Syndrome that significantly impacts the lives of individuals with this disorder and their caregivers. It plays a crucial role in various areas, including safety, communication, academic learning, and treatment monitoring. Therefore, it is essential to continue exploring and developing more objective measures that can assess important aspects of motor function in individuals living with AS.

MPS

Mucopolysaccharidosis (MPS) is a group of rare, genetic disorders characterized by the body’s inability to produce specific enzymes needed to break down and recycle complex sugar molecules called glycosaminoglycans (GAGs). These molecules are found throughout the body, often in mucus and fluid around the joints. Without the necessary enzymes, GAGs build up in cells, blood, and connective tissues, leading to a range of health problems^[1].

There are several types of MPS, each associated with a specific enzyme deficiency. For instance, MPS I, also known as Hurler syndrome, is caused by a deficiency in the enzyme alpha-L-iduronidase. MPS II, or Hunter syndrome, is another type of MPS mentioned in the sources^[2]. Each type of MPS has its own set of symptoms, which can vary widely in severity. Common symptoms across the MPS types can include skeletal abnormalities, vision and hearing problems, heart disease, respiratory issues, and in some cases, developmental delays or intellectual disability.

The development of treatments for MPS has been a significant focus in the field of rare disease research. For example, enzyme replacement therapy (ERT) has been developed for MPS I and MPS II, among others. ERT involves infusing the missing enzyme into the patient’s bloodstream, helping to break down GAGs and alleviate some of the symptoms of the disease^[2].

However, the development and approval of these therapies is a complex and lengthy process, often involving extensive clinical trials and regulatory documentation. For instance, the filing for approval of an enzyme therapy for MPS VII in the US was 76,000 pages long and involved almost 1,100 individual documents^[3].

Despite these challenges, the development of treatments for MPS has opened doors for the development of therapies for other genetic diseases, demonstrating the potential for transformative treatments in the field of rare diseases^[2].

Mutation

A mutation refers to a change in the genetic code, specifically in the DNA sequence that encodes a protein. This change can alter the meaning of the protein, impacting its function and potentially leading to various genetic disorders, including Angelman Syndrome^[1][1].

Mutations can occur in different ways. For instance, a missense mutation changes the meaning of some of the DNA, causing the cell to read it differently and insert a different amino acid into the protein. This can disrupt the protein’s function, as proteins are like machines that need to be in the right configuration to do their jobs. When the sequence of proteins changes, they often become non-functional, unable to recognize other proteins or carry out their necessary roles in the cell^[2].

However, not all changes in the genetic code lead to functional changes in the protein. A change that doesn’t alter the protein’s meaning is called a polymorphism. For example, a change from ACG to ACC in the DNA sequence doesn’t impact the protein because the cell reads these sequences as being the same. In this case, the same protein is produced, and the change doesn’t cause any problems^[1][2].

Mutations can also be classified based on their impact on the gene’s function. A loss-of-function mutation results in a protein that doesn’t perform its intended function. In contrast, a gain-of-function mutation can lead to a protein product that is overexpressed or behaves differently than it should, potentially causing toxicity to the cell^[3].

The timing and location of mutations can also vary. Some mutations occur during the formation of eggs, such as deletions on chromosome 15 associated with Angelman Syndrome^[4]. Other mutations, such as the insertion of extra DNA or mobile DNA elements, can occur in specific spots in the genome^[5].

In genetic testing, distinguishing between a mutation and a polymorphism can sometimes be challenging. The mutation spectrum, which shows the distribution and recurrence of specific variants, can provide insights into the mechanism of action of different genes and inform potential therapeutic approaches^[6][6].

Myoclonus

Myoclonus refers to sudden, brief, involuntary muscle jerks or twitches that can occur in various parts of the body. It is a symptom that can be seen in a variety of neurological disorders, including Angelman Syndrome. Myoclonus can be epileptic or non-epileptic, depending on whether it is associated with abnormal electrical activity in the brain, as detected by an electroencephalogram (EEG)^[1].

Non-epileptic myoclonus, as the name suggests, is a type of myoclonus that is not associated with epileptic seizures. It is characterized by twitching or jerking movements that are not accompanied by abnormal EEG activity, indicating that they are not caused by seizures^[2]. Non-epileptic myoclonus can be very subtle, often seen in the hands, and can continue on and off throughout a person’s life^[3].

In Angelman Syndrome, non-epileptic myoclonus is a common symptom that often begins in the teenage years and increases in frequency as individuals grow older. It can last from seconds to hours or even almost the whole day. The myoclonic events can be disruptive and uncomfortable, impacting activities such as swallowing and walking, and can cause emotional distress^[4].

Non-epileptic myoclonus in Angelman Syndrome can sometimes be mistaken for myoclonic seizures due to the similarity in their physical manifestations. However, myoclonic seizures are typically brief, lasting only seconds, and are accompanied by a burst of spike and wave activity on an EEG^[5]. In contrast, non-epileptic myoclonus does not show seizure activity on an EEG^[2].

Despite not being classified as seizures, non-epileptic myoclonus can significantly impact the quality of life of individuals with Angelman Syndrome. It can cause exhaustion, anxiety, and interfere with daily activities^[3]. Therefore, it is important to recognize and treat this symptom to improve the quality of life of individuals with Angelman Syndrome.

Natural History Study

A Natural History Study (NHS) is a type of observational study that is longitudinal in nature, meaning it follows the same participants over a long period of time, often many years^[1][2][3]. The primary goal of an NHS is to collect long-term data that can be used by pharmaceutical companies and other investigators for future therapeutic development^[1].

In an NHS, data is collected prospectively, meaning that new questions are asked at each visit about events that occurred either at that time or just in the past year^[2][3]. This approach is designed to reduce recall bias, which can occur when participants are asked to remember events from many years ago^[1][2].

Another unique feature of an NHS is that participants see the same investigator at each visit^[1][3]. This consistency helps to minimize variability in data collection, which can occur due to differences in how different investigators assess participants^[1].

An NHS complements other types of studies, such as patient registries. While both types of studies aim to answer the same questions, they collect different types of data and serve different purposes^[1][2][3]. For example, while a global AS registry is very good at collecting retrospective data, an NHS focuses on collecting data that can be collected in-person^[2].

NHSs are critical for the development of clinical trials and therapeutic products. They can help determine whether side effects observed in a therapeutic trial are due to the disease itself or due to the product^[2]. They also provide valuable insights into the disease that may not be available in textbooks or published literature^[2].

In addition to contributing to the development of treatments, NHSs also aim to understand the current needs of the community and contribute towards the founding of multidisciplinary clinics within the NHS in the future or reimbursement of drugs at the point when they are going to be approved^[4].

Participation in an NHS can also be beneficial for those who want to take part in clinical trials, as it can help ensure that they have the right paperwork in place and can easily get recruited in clinical trials as soon as a slot for which they are eligible opens^[4].

Neurodevelopmental

Neurodevelopmental disorders are a group of conditions that emerge in early childhood and are characterized by developmental deficits in personal, social, academic, or intellectual functioning. These disorders often involve complex behaviors and abilities such as learning, language, and motor skills. They are typically lifelong conditions that can impact an individual’s day-to-day functioning across various domains of life.

Angelman Syndrome (AS) is classified as a neurodevelopmental disorder. Unlike neurodegenerative diseases, which involve an ongoing progressive loss of neurons, neurodevelopmental disorders like AS are characterized by some level of dysfunction or disordered functioning within the brain, rather than a progressive loss of neuronal tissue^[1]. This dysfunction needs to be corrected to alleviate the signs and symptoms exhibited by the patient.

AS is associated with a range of clinical features, including behavioral and developmental features. These features can present significant challenges in terms of measuring therapeutic outcomes, particularly in individuals who might be minimally verbal or who might have significant motor challenges^[2].

In terms of neurological function, the focus is not only on epileptic seizures, which are common in AS, but also on other aspects of neurological function^[3].

Despite the challenges, there is optimism in the scientific community about the prospects of bridging the gap between diagnosis and practical, real-world treatments for neurodevelopmental disorders like AS^[4]. The hope is that overlaps in the high-level presentation of various genetically defined disorders can be used as entry points for different disorders, potentially simplifying the process of developing treatments^[5].

In conclusion, neurodevelopmental disorders like AS are complex conditions that require a multifaceted approach to treatment. While there are significant challenges in developing effective treatments, advances in our understanding of these disorders and the underlying biology offer hope for the future.

Neuron

Neurons, also known as nerve cells, are the primary cells of the nervous system. They are responsible for receiving sensory input from the external world, processing and interpreting it, and directing the body to respond appropriately. Neurons are the main cells that connect and send signals between different cells in the brain to implement all the functions that we do. They send these signals through their axons and receive signals on the dendrites, which are the branching parts of the neuron^[1].

Neuron morphology refers to the structure and form of neurons. This includes the number and arrangement of dendrites (branch-like structures that receive signals from other neurons), the size and shape of the cell body, and the length and direction of the axon (the long, tail-like structure that transmits signals to other neurons). The morphology of a neuron can greatly influence its function, as it determines the neuron’s connectivity and communication with other neurons^[2].

In the context of Angelman Syndrome research, understanding the morphologic behaviors of AS neurons compared to neurotypical neurons is important. This can help researchers understand how different genotypes, like deletion, mutation, UPD, ICD, are different from each other. Then, understanding what happens in those neurons if you activate the paternal copy of the gene can provide insights into potential therapeutic strategies^[3].

One of the ways to study neuron morphology is through a Sholl analysis. This is an analysis where researchers look at the number of branches that neurons have, how long they are, and whether they are close to the cell body or further away. This kind of analysis can help researchers see if there is a difference between neurotypical neurons and Angelman neurons when they are treated with certain drugs^[2].

In addition to neurons, the brain also contains other cells known as glial cells. These cells aren’t just passive supporters. They actively moderate the flow of signals in the brain, much like the components on a circuit board. They help maintain the balance, provide the nutrients, and in some cases, even speed up the transmission of signals^[4].

In the study of Angelman Syndrome, researchers are leveraging stem cell technology to dissect the disease mechanism in oligodendrocytes, a type of glial cell, aiming at uncovering new therapeutic targets^[4].

Neurotypical

The term “neurotypical” is used to describe individuals whose brain functions and develops in a way that is considered to be within the ‘normal’ or ‘typical’ range. This term is often used in contrast to neurodivergent, which refers to individuals whose brain functions and develops differently due to conditions such as autism, ADHD, dyslexia, and others.

In the context of the provided sources, neurotypical is used to describe the standard or baseline against which individuals with Angelman Syndrome (AS) are compared. For instance, one source discusses how neurotypical children at the age of 6-7 years usually show an EEG frequency range of 8-9Hz, and 9-11 year-old children that speak clear complex sentences are characterized by alpha rhythm expression in the EEG patterns^[1].

The term is also used to describe the typical development of brain functions and processes. For example, in neurotypical children, the process of synaptogenesis (the formation of synapses) and myelination (a neuronal cellular process that improves the transmission speed of neural information along neural fibers) takes years^[1].

It’s important to note that the term “neurotypical” does not imply superiority or inferiority. It is simply a descriptor used to denote a certain type of brain function and development. The concept of social humility, as mentioned in one of the sources, emphasizes the importance of not assuming that a neurotypical way of doing something is better than how someone who’s neurodivergent or someone with Angelman does something^[2].

In the context of research and treatment for conditions like Angelman Syndrome, understanding neurotypical brain function and development can provide valuable insights and benchmarks. However, it’s crucial to approach this understanding with respect for the diversity of human brain function and the unique experiences of individuals with neurodivergent conditions.

Newborn screening

Newborn screening is a public health service provided to all newborns, where each state screens for about 32 to 35 different conditions^[1]. The process of nominating new conditions to be included in the screening is done one by one^[2]. The goal of newborn screening is to identify conditions early, allowing for prompt treatment and management.

In the context of Angelman Syndrome (AS), there are ongoing efforts to include it in the newborn screening program. The Foundation for Angelman Syndrome Therapeutics (FAST), Angelman Syndrome Foundation (ASF), and others are funding a newborn screen pilot program in North Carolina with RTI, led by Anne Wheeler^[3]. The Wisconsin newborn screening lab, led by Dr. Mei Baker, is also working on perfecting the diagnostic test (Methylation test) from a spot of dried blood on a card^[3].

The goal is to have AS as one of the conditions tested for at birth, allowing for early intervention with approved therapeutics, potentially preventing the development of AS symptoms^[3]. This would also help determine the true incidence rate of AS, providing valuable data for healthcare payers^[3].

The Early Check program in North Carolina is designed to pilot these newborn screening efforts. It offers infant screening under a voluntary research protocol to parents in North Carolina, evaluates outcomes of infants identified as screen positives, studies the impact on families and parents, and publishes the data to inform public health policy and facilitate transition to standard newborn screening if it’s appropriate^[1].

The technology used for newborn screening for AS is the same as that used for other conditions already included in the screening program, such as SCID and spinal muscular atrophy^[4]. This technology, real-time PCR, is available in every state in the United States^[4].

However, adding a new condition to the newborn screening program is a significant effort. It requires a lot of data to show that the screening is feasible, appropriate, and beneficial to the population^[1]. The process cannot be mandated without the data, but screening has to be done in order to generate the data^[1].

In conclusion, newborn screening is a crucial public health service that allows for early detection and intervention of various conditions. The inclusion of Angelman Syndrome in the newborn screening program is a significant step towards early diagnosis and treatment, potentially preventing the development of symptoms.

NHP

A non-human primate (NHP) is a primate species that is not human. This group includes a variety of species, such as monkeys, apes, and prosimians (like lemurs and tarsiers). NHPs are often used in scientific research due to their close genetic and physiological similarities to humans. They serve as important models for studying human disease, behavior, and evolution.

In the context of Angelman Syndrome research, non-human primates are used to evaluate potential treatments before they are tested in humans. For instance, researchers have used non-human primates to evaluate the distribution of a vector carrying the UBE3A gene, which is implicated in Angelman Syndrome, to various cells in the body^[1]. This helps to determine whether the host will mount an adverse event or a reaction to the vector or the treatment, and best simulates the distribution of the vector to the cells that we needed to distribute to^[1].

However, the use of non-human primates in research is not without controversy. Ethical considerations, cost, and the time required to breed and raise these animals for study are significant factors that can limit their use^[2][2]. Despite these challenges, non-human primates remain a valuable tool in biomedical research, providing critical insights that can help advance our understanding of human health and disease.

NIH

The National Institutes of Health (NIH) is a part of the U.S. Department of Health and Human Services and is the nation’s medical research agency. It is primarily funded by tax dollars and is dedicated to making important discoveries that improve health and save lives. The NIH is made up of 27 different components called Institutes and Centers. Each has its own specific research agenda, often focusing on particular diseases or body systems.

The NIH provides significant funding for research related to various diseases and health conditions. This funding often supports scientific studies conducted at universities, medical schools, and other research institutions across the country and even abroad. The NIH conducts research in its own laboratories; supports the research of non-federal scientists in universities, medical schools, hospitals, and research institutions throughout the country and abroad; helps in the training of research investigators; and fosters communication of medical information.

In the context of Angelman Syndrome, the NIH has been instrumental in funding research and initiatives aimed at finding a cure for this genetic disorder. For instance, the NIH has funded initiatives to improve gene editing approaches, including those that are CRISPR-based, to reduce the burden of diseases caused by genetic changes^[1]. It has also provided a large portion of the cost for the transition of research from mouse to human studies^[2].

In one notable instance, the NIH awarded a $40 million grant to a team working on Angelman Syndrome, which was the largest NIH grant ever given to Angelman syndrome. This grant was aimed at advancing a CRISPR program and was a collaboration between Yale University, the Foundation for Angelman Syndrome Therapeutics (FAST), and Rush University^[3].

The NIH’s funding and support have been crucial in accelerating the path towards potential treatments and cures for Angelman Syndrome, thereby decreasing the burden on individual disease foundations and bringing together the best scientists to work on this cause.

Observational study

An observational study is a type of research method used in various fields, including medical and social sciences, where researchers observe subjects without intervening or manipulating the environment or subjects’ behavior. In the context of clinical research, observational studies are used to understand the natural progression of a disease or disorder over time without the use of an intervention, such as a drug or device^[1][2].

Observational studies can be longitudinal, meaning they follow the same participants over a long period, often many years^[3][4]. This allows researchers to collect long-term data that can be used for future therapeutic development. The data collected in these studies is often a mix of prospective and retrospective information. Prospective data involves asking participants about recent events or experiences, while retrospective data involves asking about past events or experiences^[3][4].

One of the key features of observational studies is that participants see the same investigator at each visit. This helps to minimize variability in data collection, as there can be differences in how different investigators assess the same parameters^[3][4].

In the context of Angelman Syndrome, observational studies have been used to inform clinical trial design and build a control cohort. The data collected in these studies can be used as a comparison for future studies where the effects of a therapy are evaluated. This could potentially reduce the number of individuals that need to be on placebo in future trials, reduce the length of the placebo period, or even replace the need for a placebo arm altogether^[5].

However, it’s important to note that individuals participating in an interventional study, where they are receiving a therapy, cannot participate in an observational study. This is because the therapy could potentially impact their development and progression, which would interfere with the data collected for the observational study^[5].

In summary, observational studies play a crucial role in understanding the natural progression of diseases and disorders, and the data collected from these studies can be invaluable in designing and conducting future clinical trials.

Open-label trial

An open-label trial is a type of clinical trial in which both the researchers and the participants are aware of the treatment or intervention being administered. This is in contrast to a double-blind study, where neither the researchers nor the participants know who is receiving the treatment or a placebo^[1].

In the context of Angelman Syndrome, open-label trials have been used in the development of therapeutics. For instance, the use of Gaboxadol (OV101) in the treatment of Angelman Syndrome was discussed in a 2015 FAST Science Summit, where it was mentioned that an open-label design was used initially for safety reasons. The FDA typically requires Phase 1 trials to be open-label when a drug has not been proven yet^[2].

However, it’s important to note that while open-label trials can provide valuable information, they also have potential drawbacks. For example, the knowledge of the treatment being received can introduce bias, as it can influence the participants’ perception of their symptoms and the effectiveness of the treatment. To mitigate this, some trials use a third-party neurologic scorer to evaluate the participants and score based on things the participants can do^[3].

In some cases, open-label trials have been retracted and replaced with randomized placebo-controlled phase 2 trials, as it was found that the open-label design didn’t work well^[3]. However, it’s also been argued that open-label trials can be a better approach to rare disease drug development, as they allow for more engagement with patients and families, who often have a deep understanding of their disease^[3].

In conclusion, open-label trials are a type of clinical trial where all parties are aware of the treatment being administered. They are often used in the early stages of drug development for safety reasons, but they also have potential drawbacks, such as the introduction of bias. Therefore, the choice of trial design depends on various factors, including the nature of the disease, the stage of drug development, and the need for patient engagement.

ORCA

The Observer-Reported Communication Ability (ORCA) measure is a tool designed to evaluate the baseline communication ability of individuals living with Angelman Syndrome (AS) and any changes in communication ability that might occur throughout a research study^[1]. It was developed with input from approximately 300 AS families and is inclusive of all modalities of communication, including words, gestures, and assistive technology^[2]. The ORCA is a caregiver-reported assessment and can be used for any individual living with AS, regardless of genotype^[2].

The ORCA measure is divided into three main concepts: expressive, receptive, and pragmatic communication^[3]. Expressive communication refers to interactions where the individual living with AS is communicating something to their communication partner. Receptive communication is the process of understanding a message expressed by a communication partner. Pragmatic communication refers to appropriate communication in social settings^[3].

The ORCA consists of 84 questions with 70 behavioral items within 22 concepts/functions that cover these areas of communication specific to AS^[1]. It also includes 14 descriptive items that capture essential information about the individual’s unique communication styles^[1]. The questionnaire is meant to be conducted by the primary caregiver who is most familiar with the individual and how they communicate^[1].

The ORCA measure was developed using rigorous quantitative methods and qualitative interviews with parents of individuals with Angelman syndrome and communication specialists who treated individuals with AS and other developmental communication disorders^[1]. The tool is now being developed for 15 other neurodevelopmental disorders through an FDA-sponsored grant^[2].

The ORCA measure is now being used by numerous pharmaceutical companies in their active clinical trials and is being progressed through regulatory agencies^[1]. This additional research focuses on analyzing data from longitudinal assessments in relationship with other communication measures so that it can be presented to the U.S. Food and Drug Administration (FDA)^[1].

The ORCA measure has shown strong evidence for validity and reliability in Angelman Syndrome^[4]. It has been found to have strong associations with the communication symbolic behavior scale and a moderate correlation with the PROMIS mobility score^[4]. The ORCA was able to distinguish among Angelman syndrome types, as well as distinguish children who either had or had not a seizure over the past year^[4]. The reliability was very good with the internal consistency of 0.89 and a test-retest reliability of 0.90^[4].

Outcome measure

Outcome measures are crucial tools used in clinical trials to determine the effectiveness of a treatment or therapeutic intervention. They are tests that accurately assess the function of an individual before the trial begins, providing a baseline, and then are used during and after treatment to see if any changes have occurred^[1][2].

In the context of Angelman Syndrome, outcome measures are used to evaluate various aspects of the disorder, such as communication, cognition, gross motor skills, fine motor skills, seizures, sleep, and activities of daily living^[3]. These measures are designed to be strong, reliable, and sensitive, as they need to accurately inform on the effect of the therapeutic treatment^[4].

There are several types of outcome measures used in trials. Performance-based outcome measures involve asking the individual to perform a task, such as putting pegs in a pegboard or walking up and down stairs. Patient-reported outcome measures involve asking the individual about their feelings or experiences, which may not be applicable to nonverbal individuals with Angelman Syndrome. Observer-reported outcome measures involve asking parents or caregivers about the individual’s behaviors or abilities^[5].

The Angelman Syndrome Biomarkers and Outcome Measures Alliance (ABOM) is an initiative focused on developing strong, objective outcome measures for Angelman Syndrome^[1]. One example of an outcome measure developed specifically for Angelman Syndrome is the Observer-Reported Communication Ability in AS (ORCA), which measures receptive, expressive, and pragmatic communication^[3].

It’s important to note that the selection of the right outcome measures is critical to the success of a clinical trial. If the wrong outcome measures are chosen, even a highly effective therapy may appear to have no benefit statistically^[3]. Therefore, the development and selection of outcome measures is a significant focus in the field of Angelman Syndrome research^[6].

In conclusion, outcome measures are essential tools in clinical trials, providing a means to assess the effectiveness of a treatment or intervention. In the context of Angelman Syndrome, these measures are used to evaluate various aspects of the disorder and inform the development of effective therapies.

Pharma

The pharmaceutical industry is a sector that develops, produces, and markets drugs or pharmaceuticals licensed for use as medications. It is driven by research and development (R&D) and focuses on the creation and production of medications to prevent, diagnose, alleviate, or cure diseases. The industry is regulated by various national and international laws and regulations, which ensure the safety and efficacy of the drugs produced.

The process of drug development in the pharmaceutical industry is complex and involves several stages. It begins with the identification of a potential therapeutic target, followed by the development of a drug candidate that can interact with this target. This is followed by preclinical testing in the laboratory and in animal models. If the drug candidate shows promise in these early stages, it moves on to clinical trials in humans. These trials are conducted in several phases to evaluate the safety, efficacy, and optimal dosage of the drug. If the drug proves to be safe and effective, it is submitted for approval to regulatory authorities like the Food and Drug Administration (FDA) in the United States^[1].

The pharmaceutical industry also faces challenges such as the need for significant investment, market conditions, and policy and coverage decisions that can affect drug development, especially for rare diseases^[2]. The industry often collaborates with patient groups and foundations to de-risk drug development options and make them more appealing for commercialization and potential approval^[3]. This collaboration can take various forms, including venture philanthropy, where patient groups provide financing to the industry to reduce their opportunity cost^[4].

However, the path to drug approval and patient access is not straightforward. Even after a drug is approved by regulatory authorities, it needs to be evaluated by payers who look at different outcomes such as value for money and disease burden. In some cases, a drug may be approved but not reimbursed, limiting patient access^[5].

In the context of rare diseases like Angelman Syndrome, patient groups play a crucial role in driving progress in their disease areas. They have to make strategic choices about the model and modality they pursue for drug development. These choices could range from spreading smaller amounts of money to different research institutions to see what sticks, investing in certain programs with the intention of a return on investment (venture philanthropy), repurposing older or abandoned drugs, or creating an independent entity to drive a therapy forward^[2].

The pharmaceutical industry’s role in the development and commercialization of drugs is crucial. However, it is also important to note the significant role played by patient groups and foundations in driving progress, especially in the field of rare diseases.

Phases of Clinical Research

Clinical trials are a crucial part of the drug development process, designed to test the safety and efficacy of potential treatments in humans. These trials typically consist of three main phases, each with its own specific goals and objectives^[1][2].

Phase 1 is the initial stage of clinical trials, primarily focused on assessing the safety of the drug. This phase often involves a small group of participants, typically 20 to 50 people, and is usually conducted with healthy volunteers^[2][3]. In rare diseases, Phase 1 trials may involve patients with the condition^[1]. The primary goal of Phase 1 is to provide safety information on the drug and determine how the drug distributes in the body^[1][2]. In rare diseases like Angelman Syndrome, Phase 1 trials may also involve initial collection of relevant outcome assessments and biomarkers^[3].

Phase 2 trials are slightly larger but still relatively small, typically involving 50 to 100 patients^[1][2]. These trials aim to determine that the drug continues to be safe in a larger population and to start understanding how the drug engages with the target^[1]. Phase 2 trials usually involve administering multiple doses of the drug over a period of time, typically three months to a year^[1]. In many rare disease programs, Phase 1 and 2 studies are often combined^[1].

Phase 3 trials are much larger studies designed to establish the safety of the drug in a large number of patients, often in the hundreds to thousands, and to show evidence of clinical benefit^[1][2]. These trials, also known as pivotal registration trials, provide the information that regulators need to see in order to approve the drug^[1].

Less commonly, there is a fourth part or “Phase 4” that happens after an intervention is approved for use by patients. This phase involves potential follow-up studies to understand more about how the drug works in other groups not included in the initial studies or to answer other questions^[4].

Clinical trials can be either “observational,” where individuals are observed without an intervention, or “interventional,” where individuals are assigned some sort of potential treatment like a drug or a device^[5][4]. In the context of rare disorders, there is often overlap between the three phases due to the small patient population^[5][4].

Phenotype

A phenotype refers to the observable physical properties of an organism, including its morphology, development, biochemical or physiological properties, behavior, and products of behavior. These properties are the result of the expression of an organism’s genes as well as the influence of environmental factors and the interactions between the two. In the context of genetic disorders like Angelman Syndrome, the phenotype refers to the set of observable characteristics or symptoms that result from the genetic mutation causing the disorder.

In the case of Angelman Syndrome, the phenotype includes features such as motor dysfunction, cognitive deficits, and in some cases, startle-induced seizures^[1]. The phenotype can vary depending on the specific genetic mutation or allele present in the individual. For instance, different alleles can result in different phenotypes, and there can be variability even within one genotype^[2].

Phenotypes are used in research to evaluate the impact of potential therapeutics. For example, in preclinical trials for Angelman Syndrome, researchers use neurobehavioral tests, body weight measurements, and ambulatory or rearing activity assessments to evaluate the impact of potential therapeutics on the phenotype of the disease^[3].

It’s important to note that the phenotype of Angelman Syndrome can also be influenced by factors such as the individual’s age and the care they receive. For example, individuals diagnosed earlier and receiving improved care and educational strategies may present different outcomes compared to those diagnosed later^[2].

In summary, the phenotype of Angelman Syndrome is a complex interplay of genetic and environmental factors, and understanding it is crucial for the development and evaluation of potential therapeutics.

Placebo

A placebo is a substance or treatment which does not have any active ingredients or therapeutic effect. It is often used in clinical trials as a control to compare the effects of the experimental treatment with those of an inactive substance. The placebo is designed to mimic the experimental treatment as closely as possible, so it may look, smell, and taste like the active drug, but it does not contain any active ingredients^[1].

Placebos are used in placebo-controlled trials, which are considered the gold standard in clinical research. These trials are designed to determine whether a drug is effective and if it’s better than not taking a drug^[1]. In these trials, neither the clinicians, the study team, the sponsor, nor the patient knows what treatment arm they’re in, whether they’re getting the active drug or the placebo drug. This is known as blinding, and it helps to minimize bias and reduce the placebo effect, allowing for a clearer evaluation of the treatment’s effect^[1].

The placebo effect is a phenomenon where a patient experiences a response to a treatment, even when they aren’t receiving the active drug. This can occur because of the patient’s expectation that the treatment will work. For example, if a person takes a pill believing it will relieve their headache, they may experience relief even if the pill was a placebo. This expectation can lead to actual physiological and biological changes^[1][1].

However, the placebo effect can make it more difficult to demonstrate the effect of an actual drug, as it raises the bar for showing a true drug effect. Despite this, the placebo effect is a common occurrence in research and is often planned for in the design of clinical trials^[1].

In some cases, even if placebo-controlled trials are conducted, there usually is a point later on in the trial where that’ll convert and everybody will get an active drug. This is done to allow everyone the prospective benefit^[1].

It’s important to note that the use of placebos is considered ethical in certain situations. For instance, when there are diseases where there’s no treatment, regulators may feel that it’s ethical to study an active drug versus a placebo, as the patient would otherwise not have access to a treatment for their disorder^[2].

In conclusion, placebos play a crucial role in clinical trials, helping to establish the efficacy and safety of new treatments by providing a control against which the active drug can be compared. Despite the challenges posed by the placebo effect, the use of placebos remains a cornerstone of rigorous, unbiased clinical research.

Plasticity

Brain plasticity, also known as neuroplasticity, refers to the ability of the brain to change its structure and function in response to changes in the environment or experiences. This concept is fundamental to understanding how learning and memory work, as it involves the strengthening or weakening of connections between neurons^[1].

In the context of Angelman Syndrome, a neurogenetic disorder, research has shown that brain plasticity is a key area of study. In particular, the forms of plasticity known as long-term potentiation and long-term depression have been extensively studied in Angelman Syndrome model mice. These forms of plasticity refer to the strengthening or weakening of connections between neurons in response to changes in the environment, which forms the basis for learning and memory^[1].

Research has also shown that synaptic plasticity, which is a part of brain plasticity, is involved in everything we do. It is characterized by cascades of gene expression that underlie brain plasticity. This synaptic plasticity is very much involved in memory formation and recall, and manipulating these cascades can affect long-term memory formation^[2].

In terms of therapeutic approaches for Angelman Syndrome, the concept of brain plasticity is also important. For instance, gene therapy, an upstream treatment, involves using viruses as vectors to deliver a normal copy of the UBE3A gene (the gene mutated in Angelman Syndrome) to the brain cells. This approach aims to restore normal brain function and potentially improve brain plasticity^[3].

Moreover, certain activities or habits can potentially help counteract some of the symptoms of Angelman Syndrome by leveraging brain plasticity. For example, assistive technology tools can be used to facilitate communication and learning in individuals with Angelman Syndrome^[4][4].

In conclusion, brain plasticity is a crucial concept in understanding and treating Angelman Syndrome. It underpins the mechanisms of learning and memory, and its manipulation through therapeutic interventions holds promise for improving the symptoms of this disorder.

Point mutation

A point mutation is a type of genetic mutation where a single nucleotide base is changed, inserted, or deleted from a sequence of DNA or RNA. Point mutations can have a variety of effects on the genetic code and can lead to changes in the proteins that are produced by the genes.

In the context of Angelman Syndrome, point mutations can occur in the UBE3A gene, which encodes a protein called a ubiquitin ligase^[1]. This protein is responsible for marking other proteins for degradation. When a point mutation occurs in the UBE3A gene, it can change the genetic code and potentially alter the function of the ubiquitin ligase protein.

Point mutations can be classified into different types based on their impact on the protein. For instance, a missense mutation is a type of point mutation that changes the meaning of the genetic code, leading to a different amino acid being incorporated into the protein^[1]. This can change the structure and function of the protein, potentially leading to disease.

In some cases, point mutations can result in a protein that is overexpressed or takes on a toxic gain of function, meaning it performs a different function than it should, which can be harmful to the cell^[2].

However, not all point mutations lead to changes in the protein. Some point mutations result in a change in the DNA sequence that does not alter the protein. These are known as polymorphisms. Polymorphisms are changes in the DNA that do not impact the protein and most of the time do not have any consequence^[3].

In the context of genetic testing, sometimes it can be challenging to determine whether a change in the genetic code is a harmful mutation or a harmless polymorphism^[1].

In the case of Angelman Syndrome, the mutation spectrum shows very specifically missense variants, with recurrent missense variants seen over and over again even though the individuals are unrelated^[4]. This suggests that these point mutations are not random but are telling us something about the biology of the disease.

In conclusion, point mutations are changes in the genetic code that can have a variety of effects on the proteins produced by genes. In the context of Angelman Syndrome, point mutations in the UBE3A gene can lead to changes in the ubiquitin ligase protein, potentially causing disease. However, not all point mutations are harmful, and some simply result in polymorphisms that do not impact the protein.

Preclinical research

Preclinical research is the first phase of drug development and treatment discovery, which occurs before clinical trials can begin. This phase is crucial for establishing the safety and efficacy of a potential treatment in non-human models, such as cells or animals, and for determining the range of minimal effective to maximal tolerated doses^[1].

Preclinical studies often take place in university laboratories and serve as a proof of concept, either in cells (in vitro) or in live animals (in vivo)^[1]. These studies utilize a variety of models, including cells, invertebrate species (flies, worms, yeast), and rodents (mice or rats)^[1]. In rodents, different dosages can be tested for drug tolerance, and behavioral studies can be conducted to test for drug effect in changing any of the behaviors characteristic of the disorder under study^[1].

The goal of preclinical research is to develop a comprehensive understanding of how a potential treatment might work and its safety profile before it is tested in humans. This includes developing animal models representative of the disease and its different genotypes, and testing compounds in these models^[2].

Once a potential treatment has shown promise in preclinical studies, the next step is to prepare for Investigational New Drug (IND)-enabling studies. These are the preclinical studies required to allow the potential treatment to enter clinical trials^[3].

Before a treatment can enter human trials, it must usually be tested in a higher vertebrate species, such as dogs, rabbits, pigs, sheep, or non-human primates^[1]. The data from these preclinical studies are used to determine the doses and frequencies that will be needed in the first-in-human trials, or Phase 1 safety studies^[1].

In summary, preclinical research is a critical phase in drug development that involves rigorous testing in non-human models to establish the safety and efficacy of potential treatments before they can be tested in humans. This phase is essential for minimizing patient risk and ensuring that only the most promising treatments proceed to clinical trials.

Promoter

A promoter is a crucial component in gene expression and gene therapy. It is a segment of DNA that initiates the transcription of a particular gene. Promoters are located near the transcription start sites of genes, on the same strand and upstream on the DNA (towards the 5’ region of the sense strand)^[1]. They function as an “on switch” for gene expression, telling the cell when to produce the gene, where and in which cell types to produce the gene, and how much of the gene to produce^[2].

Promoters can be thought of as simple on-off switches that turn on the gene, similar to a light bulb^[1]. However, they are not the only regulatory elements involved in gene expression. Enhancers, for instance, act as dimmer switches that tell the promoter when to turn on, at what levels to turn on, and at what timing to turn on^[1].

In the context of gene therapy, promoters play a significant role. For instance, in the process of delivering a therapeutic gene using a virus, the promoter helps to turn on the delivered gene so that it starts producing the protein of interest^[3]. The choice of promoter is critical as it can influence the effectiveness of the therapy. For example, a strong promoter might be used if a lot of protein needs to be produced in the cell. However, in neurons, a more moderate or weaker promoter might be preferred as neurons do not tend to like large amounts of protein being produced^[2].

Promoters can also be specific to certain cell types. For example, a neuron-specific promoter can be used to ensure that the delivered gene is only expressed in the neurons in the brain^[4]. However, the choice of promoter can also lead to complications. For instance, a viral promoter that is too active and integrates at unwanted sites in the genome can potentially activate neighboring oncogenes, leading to the development of cancers^[5].

In summary, promoters are essential regulatory elements in gene expression and gene therapy, acting as on-off switches for genes and playing a crucial role in determining when, where, and how much of a gene is produced. Their choice and use in gene therapy can significantly influence the effectiveness of the therapy and can also lead to potential complications.

Protein

Proteins are complex molecules that play a crucial role in the functioning of cells and organisms. They are often referred to as the “machines” of the cell, as they perform a wide range of tasks necessary for the cell’s survival and function^[1]. Proteins are made up of amino acids, which are strung together in a specific sequence determined by the information encoded in the DNA^[1].

The process of protein synthesis begins with the DNA, which contains the genetic information necessary to build proteins. This information is transcribed into messenger RNA (mRNA), a process often referred to as transcription^[2]. The mRNA then serves as a template for the assembly of amino acids into a protein, a process known as translation^[3].

Proteins can serve a variety of functions within the cell. Some proteins act as enzymes, facilitating chemical reactions within the cell. For example, the UBE3A protein, which is of particular interest in the study of Angelman Syndrome, is an enzyme that tags other proteins in the brain for degradation^[4]. This process helps to maintain a balance of proteins within the cell, preventing the accumulation of unnecessary or damaged proteins.

Proteins can also serve as signals, communicating information between different parts of the cell or between different cells. For instance, when an organism gets sick, proteins can signal different parts of the immune system to respond^[1].

In addition to their roles as machines and signals, proteins can also serve as structural components of cells and tissues. For example, the protein keratin is a key component of structures such as hair and nails^[1].

In some cases, proteins can be produced in situ, or where they are used. This is a concept being explored in the development of therapeutics for conditions like Angelman Syndrome^[5].

In summary, proteins are essential components of cells, playing a variety of roles from facilitating chemical reactions to providing structure and signaling information. Their production is a complex process that begins with the information encoded in the DNA and involves the transcription of this information into mRNA and the translation of the mRNA into a chain of amino acids that forms the protein.

PWS

Prader-Willi syndrome (PWS) is a rare, complex genetic disorder that affects approximately 1 in 15,000 people^[1]. It impacts nearly every system in the body, with the most notable symptom being hyperphagia, an unrelenting appetite and extreme hunger. Individuals with PWS never feel full, which can lead to life-threatening overeating and obesity if not managed in a highly restricted environment^[1].

PWS is associated with a range of other health problems, including growth hormone deficiency, behavioral challenges, intellectual disability, anxiety, sleep disturbances, and scoliosis^[1]. The syndrome is also linked to developmental delays, psychiatric disorders, and autism spectrum disorders^[1].

The genetic mechanisms that lead to PWS involve errors in the paternal chromosome 15^[2]. These can include a deletion in the paternal chromosome or uniparental disomy, where there are two copies of the maternal chromosome 15^[2]. These different genetic mechanisms can result in different constellations of medical problems or severities in individuals with PWS^[2]. For example, individuals with uniparental disomy for PWS are at higher risk for certain psychiatric symptoms like psychosis or autistic traits compared to people with a deletion^[2].

Currently, there are no effective treatments to regulate appetite in PWS, and the elimination of hyperphagia would represent a critical advance, bringing new possibilities for an independent life^[1]. However, early intervention therapies and growth hormones, if diagnosed early, have been known to have significant benefits^[3].

It’s important to note that PWS shares some similarities with Angelman Syndrome (AS), another genetic disorder. Both disorders involve errors in chromosome 15, but in the case of AS, the error is in the maternal chromosome 15^[2]. Some children with AS also exhibit similar food-related anxieties as seen in PWS^[4]. However, the two disorders are distinct and have different symptoms and challenges.

Rare disease

A rare disease, also known as an orphan disease, is a health condition that affects a small percentage of the population. The specific definition of what constitutes a “rare disease” can vary, but in the United States, a disease is considered rare if it affects fewer than 200,000 people at any given time^[1].

There are more than 10,000 known rare diseases, affecting an estimated 30 million Americans^[2]. Despite their individual rarity, collectively, rare diseases are a significant public health concern. They affect as many people as COVID-19 and other large chronic conditions, but because they are spread across such a large number of conditions, they often compete for a finite set of resources^[1].

The development of treatments for rare diseases has seen a significant uptick since the early 2000s^[3]. However, less than 5% of rare diseases have an approved therapy, and the real number is probably closer to 2 or 3% when considering the increasing number of rare diseases^[1].

Angelman Syndrome is one such rare disease. It falls in the lower middle part of disease prevalence across rare diseases^[1]. Despite its rarity, the level of activity in drug development for Angelman Syndrome is outsized for its position on the prevalence curve^[1].

However, the journey to develop treatments for rare diseases like Angelman Syndrome is fraught with challenges. Clinical trials often fail, and the barrier to FDA approval can seem insurmountably high^[4]. Despite these setbacks, the rare disease community continues to push for advancements in research and treatment options.

Efforts are being made to incentivize research into rare diseases and to centralize expertise at the FDA^[2]. Advocacy groups are also working to raise awareness and funding for rare diseases, emphasizing the importance of collaboration in rare disease advocacy^[2].

In conclusion, while rare diseases may individually affect small populations, collectively they represent a significant area of unmet need. Continued research, advocacy, and collaboration are crucial in the ongoing effort to develop effective treatments for these conditions.

Receptor

A receptor is a protein molecule that receives chemical signals from outside a cell. When such chemical signals bind to a receptor, they cause some form of cellular/tissue response, such as a change in the electrical activity of a cell. There are three main types of receptors: ion channel-linked receptors, G-protein-linked hormone receptors, and enzyme-linked hormone receptors.

In the context of Angelman Syndrome, GABA (gamma-aminobutyric acid) receptors are of particular interest. GABA is a neurotransmitter that inhibits or reduces the activity of nerve cells within the nervous system. GABA receptors are proteins located on the surface of neurons and are essential for brain development and neuronal function^[1].

There are two functionally distinct classes of GABA receptors: synaptic GABA receptors and extra-synaptic GABA receptors. Synaptic GABA receptors mediate phasic excitation, while extra-synaptic GABA receptors mediate a different kind of neural activity known as tonic inhibition^[2].

Tonic inhibition is a concept that refers to the brain’s ability to filter out “noise” or irrelevant sensory input, allowing us to focus on what’s important. This process is mediated by GABA receptors, which allow chloride ions (negatively charged) to enter the cell, effectively quieting it down^[3].

In Angelman Syndrome, there is a reduced number of a subtype of GABA receptors known as GABA alpha-5 receptors due to a deletion in the maternal allele of certain genes^[1]. This reduction is believed to contribute to the clinical severity of Angelman Syndrome^[4].

Research is being conducted to develop drugs that can enhance the function of these GABA alpha-5 receptors. For example, Alogabat is an oral tablet that has the potential to selectively enhance the function of GABA alpha-5 receptors^[4]. Another drug, OV101, was being developed to act on a specific GABA receptor to make GABA more effective^[3].

It’s important to note that while these treatments target the GABA receptors, they do not directly address the underlying genetic cause of Angelman Syndrome, which is a loss of function in the UBE3A gene. However, they may help to alleviate some of the symptoms associated with the disorder.

Reflux

Reflux, also known as gastroesophageal reflux, is a condition where stomach acid frequently flows back into the tube connecting your mouth and stomach (esophagus). This backwash (acid reflux) can irritate the lining of your esophagus, causing symptoms such as heartburn, regurgitation, and discomfort.

In individuals with Angelman Syndrome, reflux is a common issue that can present at various ages. It can be identified through signs such as decreased appetite, gagging in the morning, waking up in the middle of the night either unhappy or coughing, and signs of regurgitation on the pillow^[1][2]. In some cases, reflux can be severe enough to cause damage to the esophagus^[3].

Reflux in Angelman Syndrome patients can be influenced by various factors, including diet and constipation. Certain foods can worsen reflux, and diets high in fat, such as the ketogenic diet, can exacerbate the condition^[4]. Constipation can also contribute to reflux, especially in older children. If a child is significantly backed up, it can trigger reflux, even if it wasn’t a problem when they were younger^[3].

Treatment for reflux in Angelman Syndrome patients is typically symptomatic and can involve medication, dietary changes, and in some cases, endoscopy. Medications for reflux are generally considered safe for Angelman patients, but it’s important to consult with a healthcare provider before starting any new treatment^[3]. Dietary changes can also be beneficial, such as adding oils to the diet or adjusting the intake of certain foods^[4]. In some cases, endoscopy may be necessary to identify the cause of refractory reflux, such as eosinophilic esophagitis, which can be treated with an elimination diet and certain anti-allergy medications^[4].

It’s important to note that while reflux medications can provide relief, they can also affect the digestion and absorption of food, potentially leading to other GI issues^[5]. Therefore, it’s crucial to address the root cause of the issue and not just the symptoms. In some cases, treating underlying constipation can help alleviate reflux^[1].

In conclusion, reflux is a common issue in Angelman Syndrome patients that can be managed with a combination of medication, dietary changes, and in some cases, endoscopy. It’s important to consult with a healthcare provider to determine the best course of treatment.

Rett Syndrome

Rett Syndrome is a rare genetic neurological disorder that primarily affects females and leads to severe cognitive and physical impairments. It is often misdiagnosed as autism, cerebral palsy, or non-specific developmental delay. Rett Syndrome is caused by mutations on the X chromosome on a gene called MECP2.

The disorder is characterized by normal early growth and development followed by a slowing of development, loss of purposeful use of the hands, distinctive hand movements, slowed brain and head growth, problems with walking, seizures, and intellectual disability. There is currently no cure for Rett Syndrome, but potential treatments are being studied, and symptomatic treatments can help manage the disorder.

Rett Syndrome has been used as a genetic model for studying Autism Spectrum Disorders (ASD). In a study conducted by Julie Davidson at Vanderbilt University in 2011, Rett Syndrome, along with Angelman Syndrome and MeCP2 duplications, were used as genetic models for ASD. The study aimed to understand the genetic contributions to ASD symptoms and the possible contributions of gene dosage to ASD features and developmental course^[1].

Interestingly, Rett Syndrome and Angelman Syndrome have similar prevalence rates. Rett Syndrome affects about 1 in 10,000 to 15,000 girls, or 1 in 20,000 to 30,000 overall, whereas Angelman Syndrome affects about 1 in 12,000 to 20,000 for both sexes^[2].

In 2023, a significant breakthrough occurred in the treatment of Rett Syndrome with the approval of Trofinetide, a first-ever approved treatment for individuals living with the disorder. Trofinetide is taken orally and acts to increase insulin-like growth factor 1 (IGF-1), a protein that is detected at low levels in an individual with Rett Syndrome and necessary for brain development and plasticity^[3]. This development has been encouraging for the Angelman Syndrome community, as it helps to define what success could look like in terms of clinical trial endpoints^[3].

RNA

RNA, or ribonucleic acid, is a molecule that plays a crucial role in the process of gene expression, which is how our bodies use the information stored in our DNA to produce proteins. This process is often referred to as the “central dogma” of molecular biology: DNA is transcribed into RNA, and RNA is then translated into proteins^[1].

DNA, or deoxyribonucleic acid, is the molecule that stores our genetic information. It is composed of four different types of nucleotides, represented by the letters A, C, G, and T. These nucleotides are arranged in specific sequences, or “codes,” that provide the instructions for making proteins^[1].

RNA is produced during a process called transcription, where proteins in the cell “read” the DNA and create a complementary RNA strand. This RNA strand, also known as messenger RNA (mRNA), carries the same information as the DNA but in a form that can be used by the cell^[1].

The process of translating RNA into proteins involves reading the RNA sequence in groups of three nucleotides, known as codons. Each codon corresponds to a specific amino acid, the building blocks of proteins. The cell’s machinery reads these codons and adds the corresponding amino acids to a growing protein chain^[1].

Proteins are essential for the functioning of our cells and our bodies as a whole. They can act as enzymes, facilitating chemical reactions; as signals, communicating information between cells; or as structural components, providing support and shape to cells and tissues^[2].

In the context of Angelman Syndrome, RNA therapies are being developed to target the RNA molecules and modify gene expression. For example, antisense oligonucleotides (ASOs) and locked nucleic acids (LNAs) are designed to bind to RNA and modulate its function. These therapies aim to activate the paternal copy of the UBE3A gene, which is typically silenced in Angelman Syndrome, to produce the UBE3A protein and alleviate the symptoms of the disease^[3][4].

Rugonersen

Rugonersen is a drug developed by Roche for the treatment of Angelman Syndrome, a genetic disorder that affects the nervous system and causes severe physical and intellectual disability^[1]. The drug is an RNA therapy and an antisense oligonucleotide (ASO), also referred to as an LNA (locus nucleic acid)^[2]. These terms can be used interchangeably and both are correct.

The drug works by potentially unsilencing the paternal copy of the UBE3A gene, which is typically silent in individuals with Angelman Syndrome. By unsilencing this gene, Rugonersen can induce the expression of the UBE3A protein in the brain^[2]. This protein is crucial for normal neurological function and its absence or malfunction is the primary cause of Angelman Syndrome.

In preclinical studies, Rugonersen was shown to increase the expression of the UBE3A protein in cells and in monkeys^[1]. The drug was administered via a lumbar puncture, and the results showed a long-lasting effect, with the UBE3A protein levels continuing to rise even after the study was stopped^[1].

However, despite the promising preclinical results, Roche decided not to initiate any new trials of Rugonersen in Angelman Syndrome after analyzing the results from the Phase 1 study^[3]. The decision was not based on any safety concerns, but rather on the fact that the effects observed in treated patients did not meet the company’s internal criteria for continuing the Rugonersen program^[3].

Despite this setback, Roche offered to allow an open-label extension for patients wanting to continue on the drug, with an estimated end date of February 2024^[3]. The company also expressed hope that it would find a partner to take up the investigational therapy and move it forward^[3].

As of July 2023, Ultragenyx, another pharmaceutical company, expressed interest in gathering information about patients who have been treated with Rugonersen to see if they could potentially be eligible for their trials^[4]. However, they did not have enough information to make a decision at that time^[4].

In summary, Rugonersen is a promising drug for the treatment of Angelman Syndrome that has shown potential in preclinical studies. However, its future development and clinical application are currently uncertain and depend on the interest and investment of pharmaceutical companies.

Seizure

A seizure is a sudden, uncontrolled electrical disturbance in the brain. It can cause changes in behavior, movements or feelings, and levels of consciousness. Seizures are a key symptom of epilepsy, but not all people who appear to have seizures have epilepsy^[1][2][3].

Epilepsy is defined as two or more unprovoked seizures, meaning seizures that were not caused by a specific trigger such as meningitis or a head injury. This definition has been recently modified to include cases where a person has had one seizure but also has an abnormal EEG (electroencephalogram), a test that detects electrical activity in the brain^[1][2][3].

Seizures can be categorized into two main types: focal and generalized. Focal seizures start in one part of the brain. The symptoms of a focal seizure depend on the specific brain area where the seizure starts. For example, if the seizure starts in the part of the brain that controls vision, the person might experience visual disturbances. If it starts in the part of the brain that controls movement of the arm and leg, it could cause shaking^[1][3].

Generalized seizures, on the other hand, involve the whole brain. There are several types of generalized seizures, including generalized tonic-clonic, myoclonic, absence, atonic, and spasms. Generalized tonic-clonic seizures, also known as grand mal seizures, involve a loss of consciousness and violent muscle contractions. Myoclonic seizures are characterized by quick, jerking movements of the arms and legs. Absence seizures, often occurring in children, involve brief, sudden lapses of consciousness. Atonic seizures cause a loss of muscle control, which might cause the person to suddenly collapse or fall down. Spasms involve sudden, involuntary muscle contractions^[1][2][4].

In addition to seizure types, there are also epilepsy syndromes, which are a cluster of features, signs, and symptoms that define a specific condition. An epilepsy syndrome is defined by a specific set of seizure types, EEG findings, and often the level of cognitive functioning. This can sometimes cause confusion as people may mistake the epilepsy syndrome for the seizure type^[1][3].

shRNA

Short hairpin RNA (shRNA) is a sequence of RNA that makes a tight hairpin turn that can be used to silence target gene expression via RNA interference (RNAi). RNAi is a biological process where RNA molecules inhibit gene expression by neutralizing targeted mRNA molecules. In the context of Angelman Syndrome, shRNA is being explored as a potential therapeutic approach.

In the research, shRNA is used to target specific sequences in the UBE3A antisense transcript, which is involved in Angelman Syndrome. The shRNA acts like a set of scissors, cutting the antisense transcript at a precise location. This cutting action can activate the paternal copy of the UBE3A gene, which is typically silenced in individuals with Angelman Syndrome. This activation could potentially alleviate the symptoms of the syndrome^[1][2].

The use of shRNA in research has been significantly optimized over time. For instance, the process of creating neurons in a dish for testing therapeutics has been reduced from 10 weeks to just one week, allowing for more rapid testing of potential treatments^[1].

However, the use of shRNA is not without challenges. One of the primary concerns is off-target effects, where the shRNA binds to unintended targets. This is a significant concern because even a small number of base pair complementarities could lead to off-target binding^[3]. Another concern is the potential for cardiotoxicity when shRNA is vectorized, as it can interfere with the processing of endogenous microRNA. However, subsequent studies have shown that this risk can be mitigated by creating a microRNA scaffold around the shRNA^[3].

In terms of delivery, both shRNA and CRISPR-based technologies can be delivered as a gene therapy using viral vectors, specifically adeno-associated viruses (AAV). AAVs are particularly useful because they do not cause any human disease by themselves^[4][3].

In conclusion, shRNA is a promising tool in the development of therapeutics for Angelman Syndrome. However, further research is needed to fully understand its potential benefits and risks.

Single gene disorder

A single gene disorder, also known as a monogenic disorder, is a type of genetic disease that is caused by mutations or alterations in a single gene. These disorders are hereditary and can be passed down from parents to their offspring. The mutation can occur in the DNA sequence of any one of the estimated 26,000 genes in the human genome^[1].

In the context of Angelman Syndrome, it is considered a single gene disorder because it is primarily caused by a mutation or deletion in the UBE3A gene^[2]. This gene is located on the 15th chromosome, specifically on the mother’s copy. In individuals with Angelman Syndrome, the UBE3A gene either doesn’t work well or is missing entirely^[1].

However, it’s important to note that while the UBE3A gene is the major player in Angelman Syndrome, there are other genes involved, especially in cases where the syndrome is caused by a deletion. In such cases, many genes are deleted, but the UBE3A gene is the key player in the region^[3].

There are different types of mutations that can occur in the UBE3A gene. For instance, in some cases, the gene is present but not functioning properly due to a mutation in the gene’s sequence. This results in a protein that is made but may not function properly^[1]. In other cases, the syndrome is caused by uniparental disomy (UPD), where two copies of the paternal gene are present, both of which are silenced, meaning that no functional copy of the UBE3A gene is present^[1].

The concept of haploinsufficiency is also relevant to single gene disorders like Angelman Syndrome. Haploinsufficiency is a mechanism where a person has only a single functional copy of a gene, with the other copy inactivated by mutation. In the case of Angelman Syndrome, the mechanism is haploinsufficiency, although it is a specific use case as an imprinted locus^[4].

In terms of treatment, gene therapy is a promising approach for single gene disorders. The idea is to introduce a functional copy of the gene to compensate for the non-functional or missing gene. While this could potentially be curative, there are still many challenges to overcome, especially for neurodevelopmental disorders like Angelman Syndrome^[5].

SMA

Spinal Muscular Atrophy (SMA) is a genetic disorder characterized by weakness and wasting (atrophy) in muscles used for movement (skeletal muscles). It is caused by a deficiency in a motor neuron protein called survival motor neuron (SMN), which is critical for the maintenance and function of motor neurons. This deficiency is due to mutations in the SMN1 gene, which encodes the SMN protein. The severity and onset of SMA symptoms can vary widely, with some forms of the disease manifesting at birth or in infancy, while others may not appear until adulthood.

SMA is often used as a reference point in discussions about Angelman Syndrome, another genetic disorder, due to similarities in their genetic origins and the strategies used for their treatment. For instance, both disorders are caused by genetic abnormalities and have been the focus of gene therapy research. In the case of SMA, significant progress has been made with the development of treatments such as Spinraza, an antisense oligonucleotide (ASO) that modifies the splicing of the SMN2 gene to increase production of functional SMN protein^[1].

The success of Spinraza has provided a precedent for the use of ASOs in treating other genetic disorders, including Angelman Syndrome. ASOs are small molecules that can alter the processing of genetic information, allowing them to potentially correct the genetic abnormalities underlying these disorders. In the case of Angelman Syndrome, research is being conducted to develop ASOs that can reactivate the normally silent paternal UBE3A gene, which is intact but not expressed in individuals with the disorder^[2].

However, it’s important to note that while SMA and Angelman Syndrome share some similarities, they are distinct disorders with different symptoms and disease progressions. For instance, SMA is a degenerative condition that can lead to early mortality, while individuals with Angelman Syndrome can live many years^[3]. Therefore, while the treatment strategies developed for SMA provide valuable insights for Angelman Syndrome research, they may not be directly applicable and must be adapted to the specific characteristics of each disorder.

Small molecule

A small molecule refers to a low molecular weight organic compound that may regulate a biological process, with a size on the order of 1 nm. Most drugs are small molecules. These molecules have the ability to diffuse across cell membranes, which allows them to engage intracellularly located protein targets, leading to a biological effect.

In the context of Angelman Syndrome (AS) research, small molecules are being explored for their potential therapeutic effects. For instance, one study identified several hits in a Presto chemical library and a Maybridge library, which are collections of small molecules. These hits are compounds that have not yet been tested as drugs but are thought to represent all of the small molecular space that can be made up with certain combinations of atoms ^[1].

Another study discussed the use of a chemical engineering technology called STE, which can chemically modify payloads like protein-based payloads or nucleic acids. This technology allows the modified payloads to penetrate cell membranes and get into cells. After penetrating cells, all chemical modifications fail, and the machinery returns to its native form without losing any activity. This approach has been found to be highly efficient and is particularly promising for the treatment of neuro-based diseases like AS ^[2].

Furthermore, small molecules can be used to target the intermediary between the gene and its product (the protein), which is the RNA. This approach allows for the development of drugs that can target, in a very specific and precise way, the RNA ^[3].

In summary, small molecules are compounds that can interact with various biological processes. In the context of AS research, these molecules are being explored for their potential to modify proteins or nucleic acids, penetrate cell membranes, and target RNA, offering promising avenues for the development of new therapeutic strategies.

Speech therapist

A speech therapist, also known as a speech-language pathologist, is a professional who assesses, diagnoses, and treats communication and swallowing disorders in individuals across the lifespan, from infants to the elderly. These disorders can be related to speech, language, cognitive-communication, voice, swallowing, and fluency. In the context of Angelman Syndrome, speech therapists play a crucial role in addressing communication challenges faced by individuals with this condition.

Angelman Syndrome is a genetic disorder that primarily affects the nervous system and is characterized by delayed development, intellectual disability, severe speech impairment, and problems with movement and balance (ataxia). Individuals with Angelman Syndrome often have difficulty with speech and communication, and many are unable to speak^[1]. The primary issue in Angelman Syndrome is apraxia, a motor planning concern, which makes it difficult for individuals to form specific sounds^[1].

Speech therapists working with individuals with Angelman Syndrome may use a variety of techniques and tools to facilitate communication. One such tool is Augmentative and Alternative Communication (AAC), which includes all forms of communication (other than oral speech) that are used to express thoughts, needs, wants, and ideas^[2]. AAC can involve everything from facial expressions and gestures to electronic devices that produce speech. Speech therapists may also use techniques such as aided language stimulation, which involves speaking in symbols to the child^[2].

In addition to AAC, speech therapists may also use therapies that appeal to multiple modalities, such as touch related to sound and manipulation of the mouth to help with sound, as well as pictures^[1]. This multi-modal approach can be particularly helpful in addressing the motor planning issues associated with apraxia.

However, it’s important to note that not all speech therapists are experts in AAC^[3]. Therefore, parents and caregivers may need to seek out professionals who specialize in this area or request to speak with an assistive technology person if their current speech therapist does not feel confident in this area^[3].

In conclusion, speech therapists play a critical role in supporting individuals with Angelman Syndrome to overcome their communication challenges. They use a variety of techniques and tools, including AAC and multi-modal therapies, to help these individuals express their thoughts, needs, wants, and ideas.

Spinal cord

The spinal cord is a crucial part of the central nervous system, which also includes the brain. It is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. The spinal cord is responsible for transmitting nerve signals from the motor cortex in the brain to the body, and sensory information from the body back to the brain.

The spinal cord is composed of neurons, or nerve cells, that transmit signals to and from the brain. These neurons are organized into various pathways, or tracts, that carry different types of information. For example, motor neurons carry signals from the brain to the muscles, controlling everything from voluntary movements like walking and grabbing, to involuntary ones like heart rate and digestion.

In certain diseases, such as Spinal Muscular Atrophy (SMA) and Amyotrophic Lateral Sclerosis (ALS), these motor neurons degenerate, leading to muscle weakness and loss of function. In SMA, babies are born normally but are diagnosed before six months of age because they never reach a motor milestone, such as lifting their head, rolling over, or crawling. Most die by the time they’re 12 to 18 months of age due to progressive loss of their motor neurons because of a genetic defect^[1].

In the context of gene therapy, the spinal cord is of particular interest because it is one of the areas of the central nervous system that can be more easily addressed. Gene therapy for diseases like SMA has shown promising results, with genes being successfully introduced into greater than 90% of the cells of the spinal cord, both the motor neurons and the sensory neurons^[2]. However, for conditions like Angelman syndrome, gene therapy needs to be distributed not only to the spinal cord but also into the brain, which presents a greater challenge^[3].

Spinraza

Spinraza, also known as Nusinersen, is a drug developed by Ionis Pharmaceuticals and marketed in partnership with Biogen. It is an antisense oligonucleotide (ASO) therapy that has been approved for use in patients, particularly for the treatment of a neurological disease called Spinal Muscular Atrophy (SMA)^[1][2][3].

SMA, like Angelman syndrome, is a rare monogenetic disease, meaning it’s caused by a mutation in a single gene. The symptoms, however, are not the same in each person^[2]. Spinraza has been described as a life-changing medicine for kids and families with SMA^[3].

The drug is delivered by an intrathecal injection, a procedure similar to an epidural. This involves inserting a needle into the base of the back below where the spinal cord is, and injecting the drug^[1]. The procedure takes about 10 to 15 minutes and has been well tolerated^[1].

The development of Spinraza has provided valuable lessons that are being applied to the development of treatments for other diseases, including Angelman syndrome^[2]. The drug works by targeting the RNA in our systems, a therapeutic modality that Ionis Pharmaceuticals has been focused on advancing^[3].

As of the sources’ publication dates, over 8,500 patients worldwide have received Spinraza^[1]. The drug’s success has led to more companies adopting similar technology for the treatment of various diseases^[4].

It’s important to note that while Spinraza has been successful in treating SMA, its application and effectiveness may vary when used to treat other diseases. For instance, in the case of Angelman syndrome, the drug would need to be administered intermittently through a lumbar puncture into the cerebrospinal fluid (CSF). While it’s not a one-time treatment like CRISPR, it can be administered to a patient long-term^[5].

In conclusion, Spinraza represents a significant advancement in the treatment of neurological diseases and serves as a model for the development of similar therapies for other conditions.

Stem Cell

Stem cells are fundamental cells that have the potential to develop into many different cell types in the body during early life and growth. They serve as a sort of internal repair system, dividing essentially without limit to replenish other cells as long as the person or animal is still alive. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell^[1].

There are several types of stem cells, including pluripotent stem cells, induced pluripotent stem cells (iPSCs), and multipotent stem cells. Pluripotent stem cells are the first cells from fertilized eggs and can create a whole baby in the lab support system like the placenta. They can make any part of the baby, but not the support system^[1]. Induced pluripotent stem cells (iPSCs) are a type of pluripotent stem cell that can be generated directly from adult cells. The iPSC technology was pioneered by Shinya Yamanaka’s lab in Kyoto, Japan, who showed in 2006 that the introduction of four specific genes encoding transcription factors could convert adult cells into pluripotent stem cells^[1].

Multipotent stem cells are like the final kits. They can only make certain parts, like cells of the heart, brain, or blood^[1]. Hematopoietic stem cells (HSCs) are an example of multipotent stem cells that are used in gene therapy. They are blood-forming stem cells that can be collected from the bone marrow, cord blood collected after birth, or from the patient’s circulation using a mobilization agent^[2].

Stem cells are being used in various ways for the treatment of diseases. For instance, in gene therapy for immune deficiencies, stem cells are collected from the patient, modified to correct the genes causing the problem, and then returned to the patient^[3]. In the context of Angelman Syndrome, stem cells are being used to create humanized models in the lab to study the disease more closely and discover new drugs^[1].

Stem cell research and therapy are still very much in the scientific phase, with many teams involved in conducting complex trials to explore their potential^[2].

Synapse

A synapse is the junction or space between two neurons that allows for communication between them. This communication is facilitated by neurotransmitters, which are chemicals that transmit signals from one neuron to another^[1]. The presynaptic neuron, or the neuron that sends the signal, releases neurotransmitters into the synapse. These neurotransmitters then bind to receptors on the postsynaptic neuron, or the neuron that receives the signal, triggering a response^[2].

In the context of Angelman Syndrome, the synapse plays a crucial role. Angelman Syndrome is associated with a deficiency in the UBE3A protein, which is necessary for maintaining the balance or homeostasis of the environment around neurons. This protein is localized to the presynaptic area of the neurons and regulates the space between the presynaptic and postsynaptic compartments^[2].

A deficiency in the UBE3A protein can lead to an accumulation of unnecessary proteins and byproducts in the synapse, resulting in a condition known as synaptopathy. This condition is characterized by an accumulation of excitatory signals and a failure to have inhibitory signals in the synapse. Without inhibition, there is a loss of what is called tonic inhibition, which can disrupt the normal functioning of the neurons^[2][1].

Synaptic plasticity, or the ability of synapses to strengthen or weaken over time in response to increases or decreases in their activity, is also a key aspect of how neurons communicate. This process is crucial for specific functions to emerge, such as learning and memory^[3]. In Angelman Syndrome, there is a disruption in synaptic plasticity, which can lead to deficits in learning and memory^[4].

Research into Angelman Syndrome has also highlighted the importance of synaptic transmission, which is the process by which a signal is passed from the presynaptic neuron to the postsynaptic neuron. This process can be studied using electrophysiology, which allows researchers to examine how well the presynaptic and postsynaptic neurons are communicating with each other^[5].

In conclusion, the synapse is a critical component of neuronal communication, and disruptions in its function can lead to neurological disorders such as Angelman Syndrome. Understanding the role of the synapse in these conditions can provide valuable insights into potential therapeutic strategies.

Syndrome

A syndrome is a term used in medicine to describe a collection or group of recognizable symptoms, signs, or phenomena that are observed together and typically occur simultaneously in a patient. These symptoms and signs collectively characterize a particular abnormality or condition. The term “syndrome” is derived from the Greek word “syndromē,” which translates to “concurrence.”

Syndromes can be caused by a variety of factors, including genetic mutations, infections, chronic diseases, or environmental influences. They can affect any part of the body and can span across multiple organ systems. Some syndromes are present from birth, while others may develop later in life.

It’s important to note that a syndrome is not a diagnosis, but rather a set of symptoms and signs that provide clues to a potential underlying condition. The specific cause of a syndrome may not always be known, and the relationship between the symptoms may not be understood.

Syndromes are often named after the physician or group of physicians who first identified the condition, or they may be named based on the key features of the condition. For example, Down syndrome is named after John Langdon Down, the British physician who first described the condition in the 19th century.

In the context of medical research and treatment, understanding and identifying syndromes is crucial. It allows for the development of targeted therapies and interventions, and it can provide patients and their families with important information about prognosis and management of the condition.

Toxicity

Toxicity refers to the degree to which a substance can harm humans or animals. In the context of drug development and clinical trials, toxicity is a critical aspect that needs to be evaluated to ensure the safety and efficacy of a potential therapeutic agent. It involves assessing the adverse effects of a drug on the body, which can range from mild side effects to severe reactions that can potentially lead to death^[1].

In the development of treatments for Angelman Syndrome, toxicity studies are conducted in animal models before the drug is tested in humans. These studies aim to identify any potential adverse effects of the drug and to determine the dose levels that are safe for use^[2]. For instance, in the development of GTP-220, a gene replacement therapy for Angelman Syndrome, toxicity studies were conducted in non-human primates. The animals were infused with GTP-220 into the cerebrospinal fluid and then monitored over time for any clinical manifestations of toxicity. At designated time points, the animals were euthanized and their tissues were evaluated for the expression of the gene and any evidence of toxicity^[3].

Toxicity studies also aim to identify any genotoxicities, which refer to toxicities that can cause damage to the genome, chromosomes, or other genes. This is important to ensure that the drug does not cause irreversible changes to the genome that could potentially lead to other health problems^[2].

In addition to toxicity, other factors such as pharmacodynamics (how the drug works in the body), biodistribution or pharmacokinetics (where the drug goes in the body), and the drug’s effect on the disease pathway are also considered in the drug development process^[1][2].

It’s important to note that the process of evaluating toxicity is complex and time-consuming, which is why drug development can take a long time. However, these studies are crucial to ensure the safety and efficacy of potential treatments^[2].

Toxicology

Toxicology is a branch of science that focuses on the study of the adverse effects of chemical substances on living organisms. It involves the detection, effects, mechanisms, and treatments of toxins. In the context of drug development, toxicology studies are crucial to assess the safety and potential adverse effects of new therapeutic agents before they are tested in humans.

In the development of treatments for Angelman Syndrome, toxicology plays a significant role. For instance, in the development of the clinical candidate GTP-220, experiments were conducted where GTP-220 was infused into the cerebrospinal fluid of non-human primates. The animals were then monitored over time for any clinical manifestations of toxicity. At designated time points, the animals were euthanized and tissues were obtained to evaluate for expression of the gene and any evidence of toxicity. This process helps to ensure the safety of the drug before it is tested in human trials^[1].

Toxicology studies also involve assessing the safety of the drug at different dose levels. This is important to ensure that the drug is safe and will not pose significant risks when translated to the clinic. For instance, in the development of ION582, a potential treatment for Angelman Syndrome, the compound was tested at doses and dosing regimens that far exceeded what would be expected in the clinic. This was done to observe the full range of the compound’s effects and to ensure its safety and tolerability^[2].

In addition to assessing the safety of the drug, toxicology studies also look at potential genotoxicities to the genome, chromosomes, and other genes. This is to ensure that the drug will not cause irreversible changes to the genome that could be harmful^[3].

Toxicology studies are typically conducted in animal models before moving on to human trials. The choice of animal model depends on whether the pharmacologic action of the drug can be emulated in that animal. For instance, in some cases, neither rats, monkeys, dogs, rabbits, nor other animals can emulate the way the drug would work in a human. In such cases, the toxicology takes a checkbox kind of mentality, assessing for chemical toxicity^[4].

In conclusion, toxicology is a critical aspect of drug development, ensuring the safety and efficacy of potential treatments before they are tested in humans. It involves a thorough evaluation of the potential adverse effects of a drug, including its effects at different dose levels and its potential genotoxicities.

Transcription

Transcription is a fundamental process in the field of genetics and molecular biology. It refers to the process by which the information stored in a segment of DNA, known as a gene, is copied into a molecule called messenger RNA (mRNA)^[1]. This process is the first step in gene expression, where the information in a gene is used to produce a functional product, typically a protein^[2].

The transcription process begins when an enzyme called RNA polymerase binds to a specific region of the DNA strand, usually a bit upstream of the part that codes for the protein. This region is known as the promoter. The RNA polymerase then unzips the DNA double helix and starts to synthesize the mRNA molecule by adding nucleotides that are complementary to the DNA strand^[3].

The DNA sequence is read from the 3’ end to the 5’ end, and the mRNA is synthesized in the 5’ to 3’ direction. The mRNA molecule is a single-stranded copy of the gene and carries the genetic information from the DNA to the ribosome, where it is used as a template for protein synthesis^[1].

Transcription is regulated by proteins called transcription factors. These proteins bind to specific sequences of the DNA and control which genes are turned on (transcribed into mRNA) and which are turned off (not transcribed). Transcription factors can be either activators, which promote transcription, or repressors, which inhibit transcription^[3].

In the context of therapeutic strategies for genetic disorders like Angelman Syndrome, understanding the process of transcription is crucial. For instance, artificial transcription factors are being explored as a potential therapy. These are designed to bind to specific DNA sequences and control gene expression, potentially allowing the activation of genes that are otherwise turned off^[4].

Moreover, other therapeutic strategies like antisense oligonucleotides work on the RNA level, after transcription has occurred. These are short DNA or RNA molecules that can bind to specific mRNA molecules and prevent them from being translated into proteins, thereby controlling gene expression post-transcription^[3].

In summary, transcription is a vital process in gene expression, playing a key role in the production of proteins, the regulation of cellular functions, and the development of potential therapeutic strategies for genetic disorders.

Transgene

A transgene is a segment of DNA containing a gene sequence that has been isolated from one organism and is introduced into a different organism. This process is often used in genetic engineering to create organisms that express a novel trait or characteristic not found naturally in the species. The introduced gene sequence, or transgene, can be from the same species or a different species and is engineered to give the host organism some beneficial trait.

In the context of gene therapy for diseases like Angelman Syndrome, a transgene can be used to introduce a healthy copy of a gene to compensate for a defective or missing gene in the patient’s cells. For instance, in Angelman Syndrome, there is a lack of the UBE3A gene, so a therapeutic transgene carrying a healthy copy of the UBE3A gene can be introduced to correct the problem^[1].

The transgene is packaged inside a vector, often a virus that has been modified to be safe, which delivers the transgene into the patient’s cells. This can be done either in vivo, where the genetic material is delivered directly into the person, such as through an injection, or ex vivo, where cells are genetically modified outside the body and then returned to the patient^[2].

The transgene itself can be used as it is, or it can undergo codon optimization, where small changes are made to the mRNA to make it more stable and help produce more protein. The transgene also includes a polyadenylation signal, or a PA signal, at the end, which signals the cell to stop and provides some important stability^[2].

In the case of Angelman Syndrome, several strategies are being pursued to deliver the UBE3A transgene into the patient’s cells. These include gene replacement therapy using adeno-associated virus (AAV) vectors^[3], artificial transcription factors^[4], and CRISPR technology for gene editing^[3].

It’s important to note that the safety and efficacy of these approaches are carefully evaluated in preclinical and clinical trials. This includes testing in animal models to demonstrate potential benefit and safety, and then in human studies where the primary goal is to show safety and possibly some level of efficacy^[5].

Translational research

Translational research, often referred to as “bench to bedside” research, is a scientific approach that aims to convert basic scientific discoveries into practical applications, particularly in the field of medicine. This type of research is designed to bridge the gap between laboratory findings and the development of treatments for diseases in patients^[1].

In the context of Angelman Syndrome, translational research involves taking findings from basic science, such as understanding the function and structure of the UBE3A gene, and applying these findings to develop potential treatments for the condition. For instance, one example of translational research in Angelman Syndrome is the work done by Scott Dindot, which involved using antisense oligonucleotides (ASOs) to block the transcription of the antisense for UBE3A, resulting in the activation of the paternal UBE3A gene. This research has now progressed to Phase 1/2 clinical trials^[1].

Another example of translational research in Angelman Syndrome is the work done by Joe Anderson at UC Davis. His team modified hematopoietic stem cells, which make up bone marrow, to express UBE3A. These cells can cross the blood-brain barrier and deliver UBE3A where it is needed in the brain. This research, which has shown promising results in mice, is a clear example of how a theoretical treatment can be translated into a potential therapy^[1].

Translational research is a complex and often expensive process. It involves a series of steps, known as IND-enabling studies, which are designed to evaluate critical information related to toxicity, target engagement, off-target risks, and overall safety for human application. These studies are necessary to get an investigational human drug or biologic from the animal model to humans through regulatory authorities^[2].

In conclusion, translational research is a critical component of the scientific process, particularly in the field of medical research. It is the bridge that connects basic scientific discoveries with the development of new treatments and therapies, ultimately aiming to improve patient outcomes. In the context of Angelman Syndrome, translational research has led to promising developments in potential treatments, bringing hope to patients and their families.

UBE3A

UBE3A is a gene that plays a crucial role in the development and function of the nervous system. It encodes a protein, also known as UBE3A, which is involved in the process of protein degradation within cells^[1]. This protein functions as an E3 ubiquitin ligase, a type of enzyme that tags other proteins with a small protein called ubiquitin^[2]. This tagging process, known as ubiquitination, signals for the tagged proteins to be degraded or ‘thrown in the trash’^[2].

UBE3A protein is found in various parts of the cell, including the nucleus and the cytoplasm^[2]. There are three different forms or isoforms of UBE3A, two long ones and one short one^[2]. The two long isoforms are found in the cytoplasm, while the short isoform is found in the nucleus^[2]. Research has shown that the short isoform, found in the nucleus, is very important for UBE3A function and for Angelman syndrome^[2].

In neurons, UBE3A is expressed from the maternal copy of the gene, while the paternal copy is typically silenced^[3]. However, in certain conditions like Angelman Syndrome, the maternal copy of the UBE3A gene is deleted or mutated, leading to a loss of UBE3A protein^[3]. This loss of UBE3A protein is what causes Angelman Syndrome, a genetic disorder characterized by intellectual disability, developmental delays, speech impairment, and problems with movement and balance^[3].

UBE3A is also involved in other cellular processes. For instance, it interacts with the proteasomal subunits, which are part of the cellular machinery that degrades proteins^[2]. Additionally, it may impact neuron function through its interaction with a protein phosphatase II phosphatase activator^[2]. However, the full range of proteins targeted by UBE3A and the implications of these interactions are not yet fully understood^[2].

In recent years, research has been focused on developing therapies to restore UBE3A function in individuals with Angelman Syndrome. For instance, one approach involves stabilizing the small amount of UBE3A that is expressed from the paternal copy of the gene^[4]. Another approach involves gene therapy, where a therapeutic UBE3A gene is delivered to neurons using a virus-derived carrier^[5]. These therapies aim to restore UBE3A function and improve the quality of life for individuals with Angelman Syndrome^[5].

UBE3A antisense transcript

The UBE3A antisense transcript is a strand of long non-coding RNA that plays a crucial role in the genetic mechanism of Angelman Syndrome (AS)^[1]. AS is caused by the loss of function of a single gene, UBE3A, on chromosome 15, which is vital to how the brain controls speech, movement, and learning^[1]. The UBE3A gene codes for UBE3A protein, which tags other proteins in our cells for recycling in a process called ubiquitination^[1].

In our central nervous system, only our mother’s copy of the UBE3A gene is expressed or active. The copy inherited from our father is silenced by a mechanism called the antisense transcript, where neurons manufacture a strand of long non-coding RNA called the UBE3A-ATS that is positioned on top of the functional paternal UBE3A gene, which results in it being silenced^[1].

The UBE3A antisense transcript prematurely terminates the reading of the paternal copy of the UBE3A gene, resulting in a failure of paternal UBE3A protein production^[1]. This is thought to be a collision process whereby UBE3A is being transcribed in one direction, the antisense is coming in the opposite direction, and you get this collision and neither one goes to completion^[2].

Research has been investigating a promising strategy that uses a technology called an antisense oligonucleotide, or ASO, a mixture of DNA and RNA designed to bind the RNA of the UBE3A antisense transcript in an exact location to unsilence the paternal copy of the UBE3A gene^[1]. The ASO sequence of RNA and DNA bases is arranged in a complementary order to the RNA, inhibiting the imprint^[1].

The ASO preparation is administered through a lumbar puncture into the spinal fluid. The drug travels through cerebrospinal fluid and flows into fluid-filled structures within the brain and spinal cord to affect the neurons of the central nervous system^[1]. Through a process called endocytosis, the ASOs enter neurons of the brain and spinal cord and then move to the cell nucleus to engage the chromatin, large structures composed of tightly wound and packaged DNA^[1].

Because the ASO sequence is complementary to the UBE3A antisense transcript, it can bind to that precise segment and form two complementary strands, which results in cleavage through the RNAase degradation^[1]. Naturally occurring cellular enzymes aid in the ASOs bonding to and degrading the RNA molecule that is blocking gene transcription, inhibiting the imprint and activating the paternal copy of the gene^[1]. Released from blockage, the now bioavailable paternal UBE3A gene is available to be transcribed into mRNA, which then threads into protein manufacturing ribosomes^[1].

This approach has shown promise in cell culture and animal models, with antisense drugs shown to decrease the production of the antisense transcript and increase the production of the UBE3A protein^[3][4].

UPD

Uniparental disomy (UPD) is a form of Angelman Syndrome (AS) where both copies of chromosome 15 are inherited from the father, instead of one from each parent. In the context of AS, this results in the absence of a maternal copy and the presence of two paternal copies, both of which are silenced by the UBE3A-antisense (UBE3A-AS) transcript. This leads to both copies not expressing UBE3A in neurons, thereby resulting in the symptoms of AS^[1].

In UPD, the fertilized egg cell duplicates the paternal chromosome 15 when it detects the absence of the maternal chromosome. This duplication allows the cell to survive, but the neurons recognize both copies as paternal and do not activate UBE3A on either of them, leading to AS^[2].

The UPD and imprinting center defect (ICD) genotypes are unique in that they have two copies of the paternal allele. Theoretically, this could result in the production of more UBE3A protein when targeting the transcript in patient cells compared to individuals with deletions or mutations^[3].

Research is ongoing to understand the implications of UPD in AS. For instance, studies are being conducted to understand the differences in phenotypes between different genotypes, such as deletions and UPD^[4]. There is also interest in understanding if paternal activation of UPD is dangerous, with current data suggesting it is not^[5].

In terms of therapeutic approaches, it is believed that gene replacement could be beneficial for UPD. The concern lies in the potential overactivation of both copies, but data from animal models and cell lines suggest that this is unlikely to be a significant issue^[6].

Research models for UPD are being developed to aid in understanding gene activation in UPD. For example, a grant was funded to Dr. Albert Keung of North Carolina State University to create cellular models that mimic the UPD epigenotype of chromosome 15^[7]. These models will be valuable tools for evaluating therapeutics for UBE3A activation.

Vehicle

In the context of gene therapy for rare genetic neurodevelopmental disorders such as Angelman Syndrome, a delivery vehicle, also known as a vector, is a tool used to transport therapeutic genetic material into a patient’s cells^[1]. This is a crucial step in gene therapy as the genetic material cannot simply be inserted into the body and expected to find its way into the cells. Instead, it requires a carrier or a ‘taxi’ to transport it into the cell^[1].

There are both viral and non-viral vectors that can be used in gene therapy. Non-viral methods can include direct injection or transfection of DNA or delivery using a non-viral encapsulation. A common non-viral encapsulation method involves the use of liposomes, which are fat-like substances that surround the nucleic acid material and assist in its delivery into the cell^[1].

Viral approaches, on the other hand, involve the use of viruses that have had their viral DNA engineered or removed. This prevents the virus from replicating and causing disease. Instead, the virus is used as a carrier to transport the therapeutic transgene into the cell^[1]. A common type of virus used in this context is the adeno-associated virus (AAV), which is a small, single-stranded DNA, non-pathogenic virus^[1].

The delivery vehicle is a critical component of gene therapy platforms. Keeping the delivery vehicle consistent across different programs can lead to a higher probability of success, simplified clinical development, faster timelines, and less cash expenditure^[2].

The delivery of the vector can be achieved through different routes of administration. One approach is intravenous delivery, where the vector is injected into the bloodstream and must cross barriers to reach the target cells^[3]. Another approach is to inject the vector into the cerebral spinal fluid, which can be done in the lumbar space or closer to the brain in the cisterna magna^[3].

However, the delivery of the vector to the central nervous system (CNS) remains a significant challenge due to the blood-brain barrier. This barrier prevents the vector from moving from the blood to the other side where the neurons and target cells reside^[4]. Various strategies are being explored to improve this delivery, such as developing a gene delivery vehicle that can cross the blood-brain barrier^[4].

In summary, a delivery vehicle in gene therapy is a crucial tool that transports therapeutic genetic material into a patient’s cells. The choice of delivery vehicle and the route of administration are critical factors that can influence the success of the therapy.

Ventricle

A ventricle, in the context of the brain, refers to a set of four interconnected cavities (ventricles) in the brain where the cerebrospinal fluid (CSF) is produced. The ventricular system is composed of two lateral ventricles, the third ventricle, and the fourth ventricle. The lateral ventricles are the largest and are located in the cerebral hemispheres. The third ventricle is a narrow, funnel-shaped cavity located in the midline of the brain, while the fourth ventricle is located at the back of the pons and medulla oblongata.

The ventricles are lined by ependymal cells and are filled with CSF, which provides the brain with buoyancy and helps to protect it from injury. The CSF circulates through the ventricles and enters the subarachnoid space, where it further serves to cushion the brain and spinal cord and to remove waste products.

In the context of gene therapy for conditions like Angelman Syndrome, the ventricular system is being explored as a potential route for delivering therapeutic agents. The idea is to inject the therapeutic agent (such as a virus vector carrying a corrective gene) into the ventricles, allowing the normal flow of CSF to distribute the agent throughout the brain. This approach could potentially allow for widespread distribution of the therapeutic agent without the need for multiple injections into brain tissue^[1][2][3][4].

However, the effectiveness of this approach may depend on various factors, including the specific characteristics of the therapeutic agent and the individual patient’s brain anatomy. For instance, if a patient has a structural defect in the ventricular system, it might affect the distribution of the therapeutic agent^[5]. Furthermore, research suggests that while this approach can achieve a certain level of penetration into the brain, it may be more effective at targeting the surface of the brain and certain deeper structures that are in close proximity to the CSF compartments and vessels^[6].