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Rare mutation sheds light on the brain’s wiring

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The study of a Québec family with an unusual gene provides new insight into how our brain is built and offers a better understanding of psychiatric disorders such as depression, addictions, and schizophrenia, researchers say.

Very little is known about how the human brain wires itself. Mouse studies have previously shown that the gene DCC helps dopamine producing cells in the developing adolescent brain make specific connections.

Now, a new study that appears in the Journal of Neuroscience, shows that the gene seems to have the same effects in humans.

When they scanned the brains of 20 family members who share an altered copy of DCC, researchers found less connectivity between the areas where dopamine neurons originate (the substantia nigra and ventral tegmental area) and their target sites, such as the striatum and frontal cortex. One of these target sites—the striatum—was also smaller.

“It’s very interesting because we were able to show that this DCC gene alteration induces similar changes to the brain in both mice and humans,” says Cecilia Flores, professor in the psychiatry department at McGill University.

Because the brain systems affected by the gene influence responses to rewards, it was not surprising to see that the family members with the DCC mutation also have lower impulsivity traits and are less likely to smoke cigarettes.

MRIs of brain wiring promise better diagnosis

An increasing number of studies link DCC to psychiatric conditions, researchers say.

“Because the gene affects the brain’s dopamine pathways, which are implicated in schizophrenia, addiction, and depression, our study potentially helps us understand how these disorders arise,” says senior author Marco Leyton, also a professor in the psychiatry department

“The version of the gene inherited by the Québec family is probably protective, but other versions of the gene seem to increase risk. Our study helps us to understand why. It also provides clear evidence that a single gene has large effects on how the human nervous system is wired.”

The Canadian Institutes of Health Research and the US National Institute on Drug Abuse funded the study.

Source: McGill University

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