March 28, 2008 — University of Virginia Health System researchers have identified a gene associated with nicotine dependence in both European and African Americans. Their research adds vital new evidence to a previous study linking the neurexin 1 gene (NRXN1) with nicotine dependence.

This study is significant, because it provides novel and strong evidence that NRXN1 is involved in nicotine dependence in the African-American population, and it confirms previous research linking this same gene with nicotine dependence in Caucasian Americans. Furthermore, this new research suggests that NRXN1 may be associated in American smokers of European and African descent in different ways.
 
A team of scientists led by Ming Li, Ph.D., professor and head of neurobiology in the Department of Psychiatry and Neurobehavioral Sciences, investigated the association of NRXN1 with nicotine dependence in two independent samples. The study, funded by the National Institutes of Health, involved more than 2,000 participants from 602 nuclear families of African or European American origin. Results revealed a significant association between NRXN1 and specified measures of nicotine dependence, such as smoking quantity, in both ethnic groups.
 
"This study is another major building block in our goal to identify and characterize the genes that cause a person to be predisposed to nicotine dependence," Li says. "Isolating genes, such as the neurexin 1 gene, and understanding their physiological functions are key to preventing and treating nicotine dependence."
 
In 2006, Li and his research team became the first group of scientists ever to identify a genetic link for nicotine dependence among African Americans. That study furthered widely accepted evidence that differences exist among ethnic groups in both their smoking patterns and in their risk of nicotine dependence.
 
Li's most recent findings, which appear in the Feb. 11 issue of the journal Human Molecular Genetics and the Feb. 28 issue of the journal Nature under "Research Highlights," add to his ongoing genome-wide studies identifying and characterizing candidate genes for nicotine dependence in both Caucasian and African American smokers.