Molecular and clinical characterization of Angelman syndrome in Chinese patients.

Angelman syndrome (AS) is a neurobehavioral disorder caused by lack of function of the maternal copy of the ubiquitin-protein ligase E3A (UBE3A) gene. In our study, 49 unrelated patients with classic AS phenotypes were confirmed by methylation-specific PCR (MS-PCR) analysis, short tandem repeat linkage analysis, and mutation screening of the UBE3A gene. Among the Chinese AS patients, 83.7% (41/49) had deletions on maternal chromosome 15q11.2-13. Paternal uniparental disomy, imprinting defects, and UBE3A gene mutations each accounted for 4.1% (2/49). Two AS patients were confirmed by MS-PCR analysis, but the pathogenic mechanism was unknown because their parents' samples were unavailable. Of the two described UBE3A gene mutations, that is, p.Pro400His (c.1199C>A) and p.Asp563Gly (c.1688A>G), the latter has not been reported previously. Mutation transmission analysis showed that the p.Pro400His and p.Asp563Gly mutations originated from asymptomatic mothers. The patients with the maternal deletion showed AS clinical manifestations that were consistent with other studies. However, the incidence of microcephaly (36.7%, 11/30) was lower than that in the Caucasian population (approximately 80%), but similar to that of the Japanese population (34.5%). Our study demonstrated that the occurrence of microcephaly in AS may vary among different populations.