A Gene for Alcoholism is Discovered
Researchers at Washington University and 5 other centers have combined forces
to identify a gene that is associated with alcoholism in some families. The
scientists focused on a region of chromosome 15 that contains several genes
involved in the movement of a brain chemical called GABA between neurons. One
version of the gene, GABRG3, was found statistically linked (associated) with
alcoholism in the affected families.
Our Comments: There is a
difference between identifying an attitude that runs in a family and discovering
a gene that contributes to alcoholism. The HealthDay title of the previous
article "Heredity May Play Part in Drinking Habits" is misleading. There is no
evidence whatsoever that attitudes toward drinking are hereditary. There are
familial, societal, and cultural attitudes toward alcohol consumption but this
does not mean that they have a genetic basis.
Genes clearly do contribute to alcoholism. However, even when a gene like
GABRG3 is found, that does not mean we understand the genetic basis of
alcoholism. The researchers do not yet know how changes in the GABA gene
increase a person's risk of alcoholism.
Barbara K. Hecht,
Ph.D.
Frederick Hecht, M.D.
Medical Editors, MedicineNet.com
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Alcohol-Dependence Gene Identified
St. Louis, Jan. 14, 2004 - Investigators at Washington University School of
Medicine in St. Louis, Indiana University School of Medicine and other centers
have identified a gene that appears to increase the risk of alcoholism.
The study, published in the January issue of the journal
Alcoholism: Clinical and Experimental Research, is the first to demonstrate an
association between
this particular gene and alcohol dependence.
The gene is related to a receptor that allows for the
movement of Gamma-amino butyric acid (GABA) between nerve cells. GABA is the
major inhibitory chemical
in the central nervous system.
"There were lines of evidence from other studies -
animal studies, in vitro studies - that suggested GABA receptors are involved in
the behavioral effects of alcohol," says lead author Danielle M. Dick, Ph.D., research
assistant professor of psychiatry at Washington University School of Medicine in
St. Louis. "Because GABA receptor genes were likely candidates and previous
studies had linked this area on chromosome 15 to alcoholism, we zeroed in on
three GABA receptor genes but only found significant association with one of
them."
The study was conducted as part of the national
Collaborative Study on the Genetics of Alcoholism (COGA), an ongoing project involving interviews and DNA
samples from more than 10,000 individuals from inpatient and outpatient alcohol
treatment centers and their families. Families in the COGA study usually have
several members with alcohol dependence.
For this study, the investigators analyzed DNA from 262 families, a total of
2,282 individuals. They isolated three genes on chromosome 15 - GABRA5, GABRB3
and GABRG3 - that sit very close together on the chromosome. Then the
investigators used markers called SNPs (single nucleotide polymorphisms) to
study differences between the participants' genes.
The markers demonstrated small genetic differences did appear to influence
the risk of alcohol dependence, but only in one of the genes: GABRG3.
But it is not known how GABRG3 influences alcoholism risk. Dick says previous
research has suggested chemicals that increase GABA receptor activity can
accentuate the behavioral effects of alcohol, such as sedation, loss of anxiety and problems with motor
coordination. Conversely, chemicals that decrease GABA
receptor activity can have the opposite effect.
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