Deletion or loss-of-function mutations in maternally-imprinted Ubiquitin Protein Ligase E3A (UBE3A) result in the neurodevelopment disorder Angelman syndrome, while duplication of the maternal allele of the chromosomal region that spans the UBE3A gene, 15q11.2–q13.1, results in another neurodevelopmental disorder, Duplication 15q syndrome (Dup15q) [27,61]. Here, UBE3A is linked to Angelman syndrome.