Angelman syndrome is caused by a genetic mutation affecting a specific gene on chromosome 15.
Understanding Angelman Syndrome and its Genetic Cause
Angelman syndrome is a complex genetic disorder primarily affecting the nervous system. It's characterized by intellectual disability, developmental delays, speech impairment, movement disorders, and a distinct behavioral profile often including frequent smiling and laughter. The root cause lies in a specific genetic defect.
The UBE3A Gene and Chromosome 15
The primary genetic cause of Angelman syndrome involves the UBE3A gene located on chromosome 15.
| Gene | Chromosome | Role |
|---|---|---|
| UBE3A | 15 | Critical for brain function and development |
Normally, individuals inherit two copies of the UBE3A gene, one from each parent. Both copies are typically active in many parts of the body. However, in certain areas of the brain, only the mother's copy (maternal copy) of the UBE3A gene is active.
The Genetic Defect Leading to Angelman Syndrome
Angelman syndrome arises when the maternally inherited UBE3A gene is either missing or mutated. According to reference information, Angelman syndrome occurs when only one copy of the UBE3A gene is active in specific areas of the brain. This can happen through several mechanisms:
- Deletion: A portion of chromosome 15 containing the UBE3A gene is missing.
- Mutation: The maternal copy of the UBE3A gene has a change (mutation) that prevents it from functioning correctly.
- Uniparental Disomy (UPD): The individual inherits two copies of chromosome 15 from their father (paternal UPD) and none from their mother.
- Imprinting Defect: There is a problem with the imprinting process, which normally ensures only the maternal copy of the UBE3A gene is active in certain brain regions.
- UBE3A Mutation: A mutation directly in the UBE3A gene on the maternal chromosome 15.
In all these scenarios, the result is the same: the individual lacks a functional maternal copy of the UBE3A gene in specific brain regions. This deficiency disrupts normal brain development and function, leading to the characteristic features of Angelman syndrome.
