UBE3A and neurodevelopmental disorder: Neurodevelopmental disorders, such as Prader–Willi syndrome (PWS) (resulting from the absence of paternally expressed genes in this region), Angelman syndrome (AS) (associated with the absence of the maternally expressed UBE3A gene), and 15q11–q13 duplication syndrome (resulting from the two common forms of duplications—either an extra isodicentric 15 chromosome or an interstitial 15 duplication), are the outcomes of genetic variations in this imprinting region.