Investigating modifications to the oxytocin gene (OXT), researchers at the University of Georgia (UGA) have learned that a reduction in the amount of oxytocin expressed affects human social behavior, according to new work published in the Proceedings of the National Academy of Sciences.
Oxytocin is a hormone and neurotransmitter and well known to be involved in bonding and sociability. Sometimes called the love hormone, it is important before and after childbirth as well as during breast-feeding.
Epigenetics refers to changes to a gene by external influences that impact the expression or function of the gene. Those modifications can be a result of a great many environmental factors including diet or even the life experiences of ancestors. In this study, researchers were studying a specific type of epigenetic modification called methylation, the addition of methyl groups to DNA.
"Methylation restricts how much a gene is expressed," said Brian Haas, the lead author of this study as well as an Assistant Professor of psychology at UGA. "An increase in methylation typically corresponds to a decrease in the expression of a gene, so it affects how much a particular gene is functioning.
"When methylation increases on the OXT gene, this may correspond to a reduction in this gene's activity. Our study shows that this can have a profound impact on social behaviors," Haas continues.
Over 120 volunteers provided DNA samples for the study so the level of methylation of their OXT gene could be measured. The subjects also went through a round of tests to assess their social skills in which they viewed video clips showing facial expressions morphing from neutral to emotional. Study participants had to indicate when they felt confident in what emotion was being showed in the video.
The research team found that study participants with higher levels of methylation also had more trouble recognizing emotional facial expressions and tended to harbor more anxiety about their relationships with loved ones. Because methylation limits gene expression, higher methylation levels very likely correspond to lower levels of oxytocin.
"Participants with greater methylation of the OXT gene were less accurate in describing the emotional states of the people they saw in pictures," Haas explains. "That's a typical characteristic associated with autism, for example."
Another part of the study used functional magnetic resonance imaging to see what regions of the brain was activated during a variety of tasks; they found that those study participants with increased methylation of their OXT gene also showed less activity in areas of the brain associated with social cognition. In addition, these people displayed reduced gray matter within the fusiform gyrus, a brain region important for facial perception.
"All of our tests indicate that the OXT gene plays an important role in social behavior and brain function," Haas says.
Haas and his team caution that their results are still preliminary; much work remains to elucidate the role of oxytocin and how it is controlled. They are hopeful that this work could lead to new and improved treatments for many social disorders.
The video below explains more about the role of oxytocin.
The following short video explains methylation and epigenetics in a little more depth.