Chromosome 17 Identified as Site for Drug Dependence Genes

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Chromosome 17 Identified as Site for Drug Dependence Genes

By Jeff Minerd, MedPage Today Staff Writer
Reviewed by Robert Jasmer, MD; Assistant Professor of Medicine, University of California, San Francisco
April 12, 2006


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Explain to patients that this study did not identify any potential candidate genes for drug dependence; it merely indicated where such genes are likely to be found.
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NEW HAVEN, Conn., April 12 - Researchers are one step closer to finding genes involved in drug addiction, including dependence on opioid drugs such as heroin, morphine, and OxyContin (oxycodone).

Two clusters of such genes appear to be hiding out on chromosome 17, according to a genetic linkage study conducted by Joel Gelernter, M.D., of Yale, and colleagues, published in the May issue of the American Journal of Human Genetics.

The study involved 393 families with at least one individual with drug dependence. Most of the families (235) had two or more members with drug dependence.

Through structured interviews, the investigators identified two subgroups of drug-dependent individuals, opioid users and non-opioid users who were dependent on other drugs such as cocaine, tobacco, alcohol, and marijuana.

After obtaining DNA samples from all study participants, the investigators used genetic linkage analysis software to conduct a genome-wide search for genetic markers associated with both groups of drug-dependent individuals. The investigators then sought to determine the chromosomal locations of those markers.

A cluster of genetic markers associated with opioid use was located at a specific site on chromosome 17. The logarithm of the odds (LOD) score for this site was 3.06. (A score of three or more is generally considered significant.)

A second cluster of markers associated with dependence on other drugs was also found on a separate chromosome 17 site. The LOD score for this site was 3.46. However, this site was a significant linkage location only for individuals of European descent, not African Americans.

"These results provide a first basis to identify genes for opioid dependence from a genome-wide investigation," Dr. Gelernter said. "Research in the laboratory now is focused on finding specific genes that modify risk for opioid dependence."

The most widely studied candidate gene for opioid dependence studied to date is the mu-opioid receptor OPRM1, he noted. This gene is located on chromosome six.

"Once specific genes that increase or decrease risk are known, we will be in a better position to figure out exactly what the environmental factors might be and, perhaps, how they can be modified to protect people who are genetically at risk," Dr. Gelernter said.



Primary source: The American Journal of Human Genetics
Source reference: Joel Gelernter et al. "Genomewide linkage scan for opioid dependence and related traits." The American Journal of Human Genetics 2006; 78:759-768.