MONDAY, Sept. 29 (Health.com) — People who are missing a snippet of DNA from a brain-receptor gene are less likely to develop bipolar disorder than those with a longer version of the same gene.
The shorter version of the gene, which is called GRIK4, makes a more stable receptor for glutamate, a key brain-signaling molecule.
“This means it is part of the machinery that helps brain cells talk to each other,” says study author Benjamin Pickard, PhD, a geneticist at the University of Edinburgh in Scotland.
About 1% of people around the world have bipolar disorder, also known as manic depression, a psychiatric condition characterized by cycling episodes of depression and mania.
Pickard and his colleagues originally identified the GRIK4 gene in 2006 when they were studying a patient with schizophrenia and mental retardation. More testing suggested the gene might play a role in bipolar disorder as well as schizophrenia, according to the report in Proceedings of the National Academy of Sciences.
In the new study, they tested 356 people with bipolar disorder and 286 healthy people, and found healthy people were more likely to have the short version of GRIK4 than those with bipolar.
However, just because you have a short version of the gene doesn’t mean you won’t get the disease—it just decreases your risk.
For example, about 40% of healthy people have the shorter version, but only 20%–30% of those with bipolar disorder have the short version, Pickard says.
“Obviously this is not the only gene that leads to or protects against bipolar disorder,” says Colleen A. McClung, PhD, an assistant professor of psychiatry at the University of Texas Southwestern Medical Center in Dallas. However, the discovery of this gene variant does bolster the idea that glutamate activity is important in the development of this disease, she explains.
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