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Specific gene tied to abuse of alcohol

By Don Finley

Published: 12:00 a.m., Thursday, December 16, 2010

Using a pattern of brain waves unique to those at risk of alcoholism, San Antonio researchers and others have identified a gene linked to serotonin, a chemical messenger that plays a role in depression.

While scientists long have known alcoholism runs in families, the relationship between individual genes and alcoholism is complex.

By starting with brain waves measured in people given specific tasks — known as event-related brain oscillations — researchers first identified patterns common to those at risk of alcohol dependence.

“These event-related oscillations are measures of brain activity, and have shown to be different between people with alcoholism and a random person off the street,” said Laura Almasy, a geneticist at Southwest Foundation for Biomedical Research. “But an important point is that they’ve also been shown to be different in children of alcoholics. These differences in brain activity are not a consequence of someone’s drinking. They’re there beforehand.”

The study included 1,064 members of families with multiple generations of alcoholics in California, Connecticut, Indiana, Iowa, Missouri and New York.

Almasy and her foundation colleague Mark Zlojutro did a genomewide scan to find genes associated with those brainwave patterns. They found a strong link with a variation of the serotonin receptor gene known as HTR7.

The findings — the latest from the Collaborative Study on the Genetics of Alcoholism — recently were posted online in advance of publication in the American Journal of Medical Genetics.

Serotonin has an effect in the brain on mood and sleep, and many antidepressant drugs work by regulating serotonin. It’s also used by the digestive system.

Serotonin is altered in alcohol abuse, and some studies have linked alcoholism to genes involved in transporting serotonin through the brain.

Dr. Antonio Noronha, director of neuroscience and behavior at the National Institute on Alcohol Abuse and Alcoholism, said the study was one of the first to use a genomewide association search — a fairly new research tool — to hunt for alcohol genes.

“Serotonin has been implicated in a lot of psychiatric disorders,” Noronha said. “And this is good evidence of a gene that shows association with alcohol dependence with this (brain) wave.”

“Some people are uncomfortable with the idea that there’s a genetic component to addiction,” Almasy said. “But we know that these biological components to risk of addiction, some have to do with how you metabolize alcohol. Some of them have to do with differences in people’s brains that make them more or less susceptible to addiction.

“And we think this difference in brainwave patterns between people at risk and people not at risk is an echo of whatever that underlying biological difference is that makes some people more susceptible than others,” she said.

Stressing that alcoholism is a complex illness, Almasy said the gene they found might not be the final culprit in alcohol dependence, as scientists begin thinking about treating the disorder.

“If the difference is in the receptor,” she said, “it’s not necessarily at the receptor that we have to intervene.”