What is Angelman Syndrome?

July 2, 2024

Unravel the complexities of Angelman Syndrome: from symptoms and treatment to current research.

Understanding Angelman Syndrome

Angelman syndrome is a complex genetic disorder that primarily affects the nervous system and is characterized by developmental delays, intellectual disabilities, speech impairments, and movement issues. This section delves into the history and prevalence of Angelman syndrome and explores the role of the UBE3A gene in this condition.

History and Prevalence

First described in medical literature in 1965 by English physician Dr. Harry Angelman, Angelman syndrome has since become recognized as a distinct neurological disorder. Despite its distinct characteristics, Angelman syndrome remains a rare condition, affecting approximately 1 in 12,000 to 20,000 people.

Symptoms such as delayed development, intellectual disability, severe speech impairment, and problems with movement and balance usually become noticeable by the age of 6 to 12 months.

While the majority of cases are the result of spontaneous gene mutations, Angelman syndrome affects people assigned male and female at birth equally.

The Role of the UBE3A Gene

Angelman syndrome is primarily caused by the loss of function of the UBE3A gene, which occurs early in fetal development before birth [1].

Most cases of Angelman syndrome (about 70 percent) occur when a segment of the maternal chromosome 15 containing the UBE3A gene is deleted. In other cases (about 10 to 20 percent), Angelman syndrome is caused by a mutation in the maternal copy of the UBE3A gene.

However, the causes of Angelman syndrome remain unknown in 10 to 15 percent of affected individuals. Changes involving other genes or chromosomes may be responsible for the disorder in these cases. Angelman syndrome can also be caused by a chromosomal rearrangement called a translocation, or by a mutation or other defect in the region of DNA that controls activation of the UBE3A gene.

Understanding the role of the UBE3A gene in Angelman syndrome is crucial not only for diagnosis but also in the development of potential therapies and interventions.

Diagnosis and Misdiagnosis

Diagnosing Angelman syndrome (AS) can be challenging due to its shared characteristics with other disorders. This complexity often leads to late or misdiagnosis, with 50% of AS cases initially diagnosed incorrectly. Misdiagnosis may cause individuals to miss out on early intervention programs, resources, personalized support, or life-changing treatments (Angelman Syndrome Foundation).

Symptoms of Angelman Syndrome

Angelman syndrome primarily affects the nervous system and is characterized by developmental delays, intellectual disabilities, speech impairments, and movement issues. It's caused by issues with the UBE3A gene that occur during fetal development (Cleveland Clinic).

Healthcare professionals may suspect Angelman syndrome if a child shows the following symptoms:

Developmental delays
Limited or no speech
Seizures
Difficulty with movement and balance
Small head size

It's important to note that due to the overlap of symptoms with other syndromes, AS can be difficult to diagnose (Mayo Clinic).

Genetic Testing Methods

A definitive diagnosis of Angelman syndrome can almost always be made through genetic testing. This involves a blood test to find chromosomal changes indicative of AS. A combination of gene tests can show the alterations linked to Angelman syndrome (Mayo Clinic).

Given the complexity of diagnosis and the potential for misdiagnosis, it's essential for healthcare professionals to consider Angelman syndrome when assessing patients with the symptoms mentioned above. Early diagnosis can open the door to appropriate treatment and management strategies, improving quality of life for individuals with AS.

The Impact of Angelman Syndrome

Angelman Syndrome, a rare condition affecting an estimated 1 in 12,000 to 20,000 people, brings forth a spectrum of physical and developmental symptoms that significantly impact the lives of affected individuals and their families [1].

Physical and Developmental Symptoms

The physical and developmental symptoms of Angelman Syndrome typically become noticeable during early childhood, appearing between the ages of 6 to 12 months. The condition is characterized by delayed development, intellectual disability, severe speech impairment, and problems with movement and balance. Most individuals with Angelman Syndrome also display distinctive facial features described as "coarse" and have unusually fair skin with light-colored hair. As the individual grows older, scoliosis can develop.

Symptom	Age of Onset
Delayed Development	6-12 months
Intellectual Disability	Early childhood
Speech Impairment	Early childhood
Movement and Balance Issues	Early childhood
Distinctive Facial Features	Adulthood
Fair Skin and Light Hair	Adulthood
Scoliosis	Adulthood

Living with Angelman Syndrome

Living with Angelman Syndrome presents an array of challenges due to its lifelong impact. Affected individuals continue to experience intellectual disability, severe speech impairment, and seizures throughout their lives. Despite these challenges, individuals with Angelman Syndrome have a nearly normal life expectancy.

The continuous nature of the symptoms necessitates ongoing care and management. This can include a combination of therapies, medication to manage seizures, and educational interventions to support development.

The support for individuals with Angelman Syndrome and their families is of paramount importance. Various support groups, clinical resources, and research initiatives are in place to assist those navigating life with Angelman Syndrome. Despite the challenges, the resilience and strength displayed by those affected by Angelman Syndrome are commendable, reminding us of the human spirit's ability to adapt and thrive, even in the face of adversity.

Current Research and Clinical Trials

Research into Angelman syndrome is currently focused on two main areas: gene therapy and reactivation strategies. Clinical trials are also underway, with the aim of developing new treatments and improving symptom management.

Gene Therapy and Reactivation Strategies

Gene therapy for Angelman Syndrome involves delivering the missing UBE3A gene to the appropriate cell type using an adeno-associated virus (AAV) and other engineered viruses. AAV is commonly used due to its safety and efficacy in delivering the gene to the cell.

Reactivation strategies aim to turn on the father's copy of UBE3A, which is silent in individuals with Angelman Syndrome due to UBE3A antisense RNA. Various approaches include the use of topoisomerase inhibitors, antisense oligonucleotides, RNA cutters like shRNAs, miRNAs, and siRNAs, as well as ribozymes and CRISPR/Cas9 technology [3].

Topoisomerase inhibitors have been shown to successfully turn on the paternal copy of Ube3a in mice by binding to the UBE3A-ATS tracks, thereby stopping the train and allowing UBE3A protein production. However, these inhibitors can have side effects as they also stop other "trains" in the genome.

Antisense oligonucleotides and locked nucleic acids are being pursued by various companies for reactivation therapy in Angelman Syndrome. These drugs are highly targeted to UBE3A-ATS, causing the derailing of the UBE3A-ATS train and restoration of UBE3A. Injection into the cerebrospinal fluid (CSF) is required, and treatment may need repeated doses [3].

Ongoing Clinical Trials

Various clinical trials are currently underway for Angelman Syndrome, sponsored by companies such as Ionis Pharmaceuticals, Ultragenyx, Hoffman La Roche, Neuren Pharmaceuticals, and Roche/Genentech [4].

Clinical Trial	Sponsor	Age Range	Locations
Halos	Ionis Pharmaceuticals	2 to 50 years	US, Australia, Israel, Italy, UK
KIK-AS	Ultragenyx	4 to 17 years	US, Canada, UK
Tangelo	Hoffman La Roche	1 to 12 years	US, Italy, Netherlands, Spain
Aldebaran	Roche/Genentech	5 to 17 years	US, Australia, France, Italy, Spain

An example of pathway intervention therapy for Angelman Syndrome is OV101, which improved tonic inhibition in AS neurons. Initially intended for sleep issues, it was found to be safe and is now tested in individuals with AS to help manage symptoms. This does not represent a cure but may assist in symptom management.

These ongoing research efforts and clinical trials bring hope to individuals affected by Angelman Syndrome and their families. While current treatment options primarily focus on managing symptoms, these pioneering therapies have the potential to address the underlying genetic causes of the condition.

Treatment and Management

Managing Angelman Syndrome involves a comprehensive approach that includes early intervention, symptom management, and support for individuals and families coping with the condition.

Early Intervention and Symptom Management

Currently, there is no cure for Angelman Syndrome, and treatment focuses on managing the specific symptoms of the condition. Early diagnosis and treatment are crucial for maintaining the highest quality of life for individuals with Angelman Syndrome. The emphasis is on early intervention to assist with development, offering potential therapies for children diagnosed with Angelman Syndrome.

Current treatment focuses on managing symptoms and addressing the developmental delays in children with Angelman Syndrome. One example of pathway intervention therapy is OV101, a drug trialed by Ovid Therapeutics. Originally intended for sleep issues, OV101 improved tonic inhibition in AS neurons and was found to be safe. It has subsequently been tested in individuals with Angelman Syndrome to help manage symptoms. This type of drug does not represent a cure but may assist in symptom management.

Support for Individuals and Families

Living with Angelman Syndrome can be challenging for both the individual and their family. Support can come in various forms, including educational services, therapy programs, and support groups. These resources can provide families with a better understanding of Angelman Syndrome and strategies for managing daily challenges.

In addition to these resources, ongoing research offers hope for the future. Current studies are exploring gene therapy for Angelman Syndrome, which involves delivering the missing UBE3A gene to the appropriate cell type using an adeno-associated virus (AAV). AAV is commonly used due to its safety and efficacy in delivering the gene to the cell [3].

While managing Angelman Syndrome can be complex and challenging, early intervention and ongoing support can make a significant difference in the lives of those affected by the condition. By leveraging current treatments, exploring emerging therapies, and utilizing supportive resources, individuals with Angelman Syndrome and their families can navigate this journey with confidence and hope.

Genetics of Angelman Syndrome

Understanding the genetic basis of Angelman syndrome can provide valuable insights into its causes, diagnosis, and potential treatment strategies.

Genetic Causes and Mechanisms

Angelman syndrome is primarily caused by a problem with the UBE3A gene located on chromosome 15. While both parents typically contribute one copy of the UBE3A gene, only the maternal copy is active in nerve cells in the brain and spinal cord. The paternal copy, on the other hand, is usually silent.

Different genetic mechanisms can interrupt the normal function of the maternal UBE3A gene, leading to Angelman syndrome. These include deletion of the maternal chromosome 15 (occurring in about 70% of cases), mutations in the maternal UBE3A gene (10-20% of cases), paternal uniparental disomy, or chromosomal rearrangements. In some instances (10-15% of cases), the cause of Angelman syndrome remains unknown.

According to the Angelman Syndrome Foundation, the severity of Angelman syndrome symptoms can vary depending on the genotype. The most common genotype, deletion positive, is often associated with the most severe symptoms.

Inheritance and Recurrence Risk

While Angelman syndrome is a genetic disorder, the majority of cases are not inherited. Most often, the genetic changes leading to Angelman syndrome occur spontaneously during egg or sperm formation or early embryonic development. This is especially true for cases caused by a deletion in the maternal chromosome 15 or by paternal uniparental disomy.

Inherited cases of Angelman syndrome are rare and usually occur when a mutation in the UBE3A gene or a nearby DNA region is passed from one generation to the next. An interesting aspect of this inheritance is that a carrier father can pass on the genetic defect without causing symptoms, but if a carrier mother passes on the gene defect, it results in Angelman syndrome in her children.

According to the Angelman Syndrome Foundation, in more than 98% of the chromosome deletion cases, the genetic changes occur spontaneously and are not inherited, hence the recurrence risk for these families is less than 1%. For individuals with no known mechanism for Angelman syndrome (eliminating all 4 mechanisms), the recurrence risk is uncertain but likely increased, probably not exceeding 10%.