<unk>  syndrome is caused by copy number variation (CNV) in which extra copies of certain genes are present in the genome. Two duplication types are commonly described in<unk>  syndrome, interstitial and isodicentric. Interstitial duplications are typically partial trisomies (i.e., one extra copy of each gene) and features these extra gene copies on the Chromosome 15 alongside the "original" copies. Isodicentric duplications are typically partial tetrasomies (i.e., two extra copies of each gene) and feature an extranumerary chromosome that contains the extra genes. Many important genes in the 15q11.2-13.1 region likely play crucial roles in the etiology of<unk>  syndrome. UBE3A is the causative gene of Angelman syndrome and has been associated with autism. It is involved in protein degradation via the ubiquitin pathway and also plays an important role in synaptic functioning. GABRA5, GABRB3, and GABRG3 encode the α5, β3, and γ3 subunits of GABAA receptors, respectively. Because GABA is the principal inhibitory neurotransmitter of the human brain, it is likely that duplications of these GABAA receptor genes affect or disrupt inhibitory neural transmission in<unk>  syndrome.
Dup15q
Distal 18q-
Xq28
Ring chromosome 15
Ring chromosome 18
X chromosome
Ring chromosome 22
RUB A535