Washington, May 6 : Researchers at the Indiana University School of Medicine have identified a gene associated with alcohol dependence (AD) and cocaine dependence.
Researchers have found that seven of the nine single nucleotide polymorphisms - DNA sequence variations - in the 3' region of TACR3 have a significant association with AD as well as cocaine dependence.
Previous family-based research had linked a broad region on chromosome 4q with alcohol dependence (AD).
"We believe it is important to identify genes contributing to AD for two primary reasons," said Tatiana M. Foroud, director of the division of hereditary genomics at the Indiana University School of Medicine and first author of the study.
"First, better treatments can be developed which would improve the success rate for those wishing to end their AD. Second, being able to identify those at greater risk for AD at a young age would allow interventions to be initiated earlier, potentially reducing the likelihood that the individual will become AD," Foroud added.
"The past few years have been an incredibly exciting time in gene identification," added Danielle Dick, assistant professor of psychiatry, psychology, and human and molecular genetics at Virginia Commonwealth University.
"Scientists are now entering an era where genes are being associated with AD and, importantly, these findings are replicating across samples. We know that AD shows a lot of variability, with affected individuals differing on many dimensions, such as age of onset, severity of symptoms and other co-occurring psychiatric and drug problems. This study makes an effort to understand how the TACR3 gene might contribute to some of this variability, rather than simply treating all AD as the same," she added.
This study is part of the larger Collaborative Study on the Genetics of Alcoholism (COGA), said Foroud, which had previously detected a link between AD and a region on chromosome 4q.
Using COGA data, researchers searched for an association between AD and 30 SNPs throughout TACR3 among 219 European American families. Researchers also looked for any association with cocaine dependence.
"We have identified a gene that we believe contributes to the risk for AD and is, furthermore, particularly important for those individuals who meet not only the DSM-IV criteria for AD but also the more stringent ICD-10 criteria. Furthermore, we found that this gene was also strongly associated with cocaine dependence," said Foroud.
Foroud said these results help support the theory that there are many genes, each with small individual effects that contribute to the risk for AD.
The study is published in the June issue of Alcoholism: Clinical and Experimental Research and are currently available at OnlineEarly.