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(For our list of subjects with an imprinting defect, click here.). UBE3A Mutation. Malfunction of the UBE3A gene on the maternal chromosome #15 seems to be the cause of Angelman syndrome. In the case of a UBE3A mutation, there is a mistake in the genetic code of the UBE3A gene.
While Angelman syndrome can be caused by a single mutation in the UBE3A gene, the most common genetic defect leading to Angelman syndrome is an ~4Mb (mega base) maternal deletion in chromosomal region 15q11-13 causing an absence of UBE3A expression in the paternally imprinted brain regions.