Dysregulation of the oxytocin receptor gene in Williams syndrome.

Williams syndrome (WS) is caused by a microdeletion of chromosome 7q11.23, and is characterized by various physical and cognitive symptoms. In particular, WS is characterized by hypersocial (overfriendly) behavior; WS has gained attention as aspects of the WS phenotype contrast with those of autism spectrum disorder (ASD). The oxytocin receptor gene (OXTR) contributes to social phenotypes in relation to regulation of oxytocin (OXT) secretion. Additionally, mounting evidence has recently shown that DNA methylation of OXTR is associated with human social behavior. However, the role of OXTR in WS remains unclear. This study investigated the regulation of OXTR in WS. We examined the gene expression levels in blood from WS patients and controls, and then analyzed the methylation levels in two independent cohorts. We showed that OXTR was down-regulated and hypermethylated in WS patients compared to controls. Our findings may provide an insight into OXTR in mediating complex social phenotypes in WS