UBE3A and Prader-Willi syndrome: The imprinting of Ube3a and its neighboring genes is coordinated by a regulatory region known as the Prader-Willi syndrome (PWS)-AS imprinting center (IC), which is located upstream of the adjacent SNURF (SNRPN upstream reading frame)–SNRPN (small nuclear ribonucleoprotein-associated protein N) gene on the human 15q11-q13 chromosome region (Buiting et al., 1999; Ohta et al., 1999; Perk et al., 2002).