A new study from Duke University Medical Center found a "genetic signature" that correlates autism with deficiencies in how the brain process oxytocin. Oxytocin researchers for a long time have suspected that there's some connection, because some of the key symptoms of autism spectrum disorder, or ASD, involve reduced abilities to interact socially with other people.
Instead of mutations in genes, the Duke researchers found differences in the methylation of genes that regulate the expression of oxytocin receptors. Methylation of some proteins in the oxytocin receptors of people diagnosed with ASD was about 70 percent, compared to approximately 40 percent in the general population.
"These results provide a possible explanation of why social isolation forms part of the autism spectrum -- because an autistic individual's ability to respond to oxytocin may be limited," [said co-lead author Simon G. Gregory, Ph.D., assistant professor in the Duke Department of Medicine]. " Oxytocin has been tied to levels of trust and ability to read social cues."
The study was reported by Science Daily today.
Methylation is a molecular process that "switches off" or "switches on" genes. Remember that are genetic makeup is not constant. Genes may be expressed, that is, activated, by experience after birth. Those experiences include external events as well as molecular events.
To my mind, this gives some weight to the theory that a cause of autism -- or a contributor -- might be the extra dose of oxytocin usually given to women in labor. The theory is that all this extra oxytocin, in the form of a pitocin drip, hitting the baby's brain during labor may cause the oxytocin receptors in his brain to lower their receptivity, that is, to down-regulate, just like you'd lower the thermostat in your house when it's too warm.
Here's the citation, with a link to the abstract:
Simon G. Gregory, Jessica J. Connelly, Aaron J. Towers, Jessica Johnson, Dhani Biscocho, Christina A. Markunas, Carla Lintas, Ruth K. Abramson, Harry H. Wright, Peter Ellis, Cordelia F. Langford, Gordon Worley, G. Robert Delong, Susan K. Murphy, Michael L. Cuccaro, Antonello Persico and Margaret A. Pericak-Vance. Genomic and epigenetic evidence for oxytocin receptor deficiency in autism. BMC Medicine, 2009; (in press)