St. Louis-based researchers in the study said Wednesday they have identified a gene that appears to increase the risk of alcohol dependence.

At the same time, a different arm of the study, which includes a scientist from Southwest Foundation for Biomedical Research in San Antonio, is zeroing in on a different spot of the genome in a search for genes that are involved in alcohol metabolism and brain activity.

The work is all part of the $65 million Collaborative Study on the Genetics of Alcoholism (COGA), one of the largest research projects ever sponsored by the National Institutes of Alcohol Abuse and Alcoholism. The study has enrolled 10,000 people from six locations who come from families with a history of alcohol abuse. None of the study sites is in Texas.

Scientists long have known alcoholism runs in families. But the search for a specific gene has been an elusive one.

A paper published Wednesday in the journal Alcoholism: Clinical and Experimental Research pinpointed a specific gene on chromosome 15 that helps regulate gamma-amino butyric acid, or GABA — one of the brain chemicals that transmits messages between neurons in the brain.

GABA is involved in altering behavior, and doctors have known for some time that it is linked to psychiatric disorders, said Danielle Dick, a professor of psychiatry at Washington University School of Medicine in St. Louis and the principal author of the study.

"Stimulating GABA receptors will increase behavioral effects of alcohol, like motor coordination (and) reduction of anxiety," Dick said.

San Antonio scientist Laura Almasy is working with another group of researchers who have identified several parts of chromosome 4 that could contain genes related to alcohol metabolism and GABA receptors.

"We've got some great candidates in these regions," she said. "Now we have to try to figure out which of them is responsible, and then what specific mutations are influencing risk."

Almasy works at the foundation's SBC Genomics Computing Center, where 1,000 dual-processing computers work in tandem to analyze vast amounts of genetic data to speed the understanding of complex diseases, such as alcoholism.

Researchers expect to find a number of genes are involved in familial alcoholism.

"It is important to say that these genes all influence your risk," Dick said. "There is no one alcoholism gene."

Identifying the genes could open up new pathways for medications, she said.

People who carry the variants also could learn about their risk for alcohol abuse and decide whether they should drink, she added.

One of the first studies into alcoholism genes was done by a former University of Texas Health Science Center professor, Kenneth Blum, who studied brain samples from dead alcoholics and identified a form of a dopamine receptor gene that he said is a major cause of the disorder.

The study was controversial as other scientists questioned Blum's methodology and could not reproduce his results. Other scientists still have not been able to validate those findings, Dick said.

ctumiel@express-news.net