Angelman Syndrome (AS) is caused by a severe reduction of expression of the gene UBE3A in the brain. UBE3A is a ubiquitin ligase whose function and targets relevant to AS are still unknown.

 Angelman Syndrome is caused by a severe reduction of expression of the gene UBE3a in the brain. UBE3A is a ubiquitin ligase whose function and targets relevant to AS are still unknown.

Want more information on the genetics of Angelman Syndrome and what all those medical terms mean? Please see our Genetics 101 section

 
 ï»¿ï»¿

15q11.2-q13 deletions (~68% of cases)  ~ The majority of AS cases are caused by deletions on the maternal copy of Chromosome 15. Due to genomic imprinting, only the maternal copy of UBE3A is expressed in the brain. The deletion thus removes the normal expression of this gene in individuals with AS.

UBE3A mutations (~11% of cases) ~ In these individuals, mutations in the UBE3A gene either prevent its expression or function. Thus these individuals do not have the appropriate levels of functional UBE3A in the brain.

Uniparental disomy (UPD; ~7% of cases) ~  In UPD, the individual has two copies of paternal Chromosome 15. Because UBE3A is not expressed from the paternal copy, these individuals lack normal levels of UBE3A in the brain.

Imprinting Defect (~3% of cases) ~  These individuals may have a deletion of the imprinting centre on Chromosome 15, but cases can also be cause by loss of imprinting information during the mother's oogenesis. Loss of imprinting will prevent expression of the maternal UBE3A gene in the brain.

Clinical/Other (~11%) ~ In these individuals, all testing for Angelman Syndrome is normal, but they still meet the diagnostic criteria for AS. These individuals may have as yet unrecognised mutations that affect UBE3A or genomic imprinting on Chromosome 15. Please note that there are several other syndromes that present like AS that can be tested for (see right menu).

Summarised from GeneReviews on Angelman Syndrome by , MD, , MS, CGC, and , MD


 



 

Rhys, 13. UBE3A Mutation

Alternative Diagnosis

There are several other syndromes that share characteristics with Angelman Syndrome; view known mimicking syndromes here.>

The genetics

 Learn the jargon; a basic description of the genetics behind Angelman Syndrome.

*Note: this link will direct you to the United States Website in a new window.>

PROGNOSIS

Newly diagnosed families often wonder "What will my child be like?" Learn about variability in Angelman Syndrome here.>


Copyright © Foundation for Angelman Syndrome Therapeutics • Privacy Policy | Terms of Use
F.A.S.T. Australia • PO Box 248 • Salisbury • Queensland • 4107 • Phone 1300 078 108 • FAX 07 4032 5255