September 17, 2010

Gene variant may play role in men behaving badly

by K.C. Jaehnig

CARBONDALE, Ill. -- A bit of DNA just a hair too “long” may have something to do with how often some men behave badly, an interdisciplinary team of researchers from Southern Illinois University Carbondale has found.

That extra DNA lies on a particular form of a gene that regulates serotonin, a hormone that controls mood and emotion. In men with intellectual disabilities and a tendency to act up, this long version spells trouble.

“It seems to affect the intensity of the behavior -- you’ll see more frequent instances of aggression, self-injury and property destruction,” said behavior analyst Michael E. May, who headed the project.

“We did not find this effect in men with disabilities but no history of aggression or in our normally developing control group.”

The team, consisting of May, geneticist David A. Lightfoot, molecular biologist Ali Srour, statistician Rhonda K. Kowalchuk and Vanderbilt University behavioral analyst Craig H. Kennedy, will publish its findings in the peer-reviewed Brain Research Journal later this year. The project relates to earlier work linking aggression in this same population with MAO-A -- sometimes called the “warrior” gene. That study showed that men with MAO-A were more than twice as likely to lash out, destroy things or hurt themselves as those without it.

“The MAO-A gene is an enzyme that breaks down serotonin for recycling, where this gene transports serotonin, so (the current study) seemed like the next logical step,” May said.

“Our initial goal was to see if there was something specific about this particular variant of the transporter gene that was associated with aggression in people with intellectual disabilities. While we found it wasn’t directly related, we think it might affect the intensity -- turning it up or down or in this case shutting it off too early, leaving people hypersensitive to environmental adversities such as abuse or neglect.”

The findings complement previous research done by University of California psychiatrist David Hessl. Hessl has linked frequent problem behavior in people suffering from Fragile X Syndrome, a genetic condition related to developmental delays and autism, with the long version of the same transporter gene variant studied at SIUC.

“Taken together, this suggests that aggressive tendencies by themselves do not predict the severity of aggression,” May said. “It also suggests that the long version’s effect is not limited to one particular disability, that it might be more broadly associated across disabilities rather than focused within a particular subgroup.”

“Bad” gene variants do not inevitably lead to bad outcomes, May stressed. Environment plays a role, too -- a fact he finds cheering from a behavior analysis standpoint.

“We know that early intervention has a huge effect on the brain, which constantly goes through a remodeling process, building on connections that are most used and getting rid of the rest,” he said.

“If kids who are predisposed to aggression are constantly in an aversive environment, it will have an effect on their brain development. But if we can identify them with a simple cheek swab and then work with their parents and caregivers so they know how to reinforce the best behavior possible, they will be ahead of the game.”