Earlier this year we reported on studies that identified genetic linkages to autism, a condition that comprises a spectrum of behavioural and cognitive disturbances of childhood development and is known to be highly heritable. Despite efforts to identify the genetic components, fewer than 10% of autism cases have been attributed to single gene disorders.
In new work from Duke University Medical Center, researchers have unexpectedly identified an epigenetic component of autism. The study revealed a genomic deletion containing the oxytocin receptor gene (OXTR), previously implicated in autism, in an autistic child and his mother (who exhibits symptoms of obsessive-compulsive disorder). The child’s sibling, also autistic, did not have the deletion but exhibited DNA methylation at CpG sites known to be involved in regulation of OXTR expression. Further analysis in a larger set of affected individuals confirmed a significant increase in methylation of these sites compared to controls and that this correlated with decreased expression of OXTR mRNA in temporal cortex tissue.
Oxytocin is a hormone secreted into the bloodstream from the brain, and also released within the brain, where it has a bearing on social interaction. Previous studies have shown that giving oxytocin can improve an autistic person’s social engagement behaviour and it is being explored as a potential treatment. Increased methylation of the oxytocin receptor gene may make a person less sensitive to the hormone and the results of this study, published in the journal BMC Medicine, could provide information about which individuals will respond better to treatment with oxytocin.