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Gene that controls serotonin linked to autism symptoms

Kathleen Blanchard's picture
Some autism symptoms newly linked to gene defect.

Researchers have discovered a gene defect that controls serotonin in the brain that could drive some behaviors linked to autism spectrum disorder. In the new study, scientists discovered specific autistic behaviors that include difficulty communicating and resistance to change may come from a mutation in the CELF6 gene.

The finding is important because researchers say understanding the mechanism of autistic behaviors can help explain the basis of the complex disease.

The study result that was carried out by scientists at Washington University School of Medicine in St. Louis also found the same gene defect causes serotonin levels in the brain to plummet.

Serotonin is a chemical messenger in the brain produced by a small number of neurons that has been suspected to play a role in autism. Thirty percent of people with autism have low serotonin levels.

The CELF6 gene defect has never been identified before and provides information about the biological basis of autism.

Lead author Joseph D. Dougherty, PhD, an assistant professor of genetics at Washington University said in a press release, "...t’s not possible to design a different drug for every child. The real key is to find the common biological pathways that link these different genetic routes and target those pathways for treatment.”

To date, only a few gene defects have been linked to the disorder. The mutations only occur in a small number of people with autism spectrum disorder that don't explain symptoms.

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For the study, researchers found 200 genes involved in serotonin production in healthy mice. After they identified the genes they looked for alterations in the DNA of 400 autistic children donated by the Autism Genetic Resource Exchange. They found alterations in the gene CELF6. The gene binds to RNA. In one patient a copy of the gene was so severely mutated it no longer functioned to produce serotonin.

The researchers explored the mutation further to find out if the discovery was coincidental by looking for the mutation in the DNA of another 860 children with autism. None of the children had the mutation, nor did 1,000 normal and healthy individuals whose DNA was tested.

The researchers kept looking, suspecting the gene defect was rare and might be linked to serotonin, so they again explored the pathway in mice.

"If this gene has some influence on whether a person gets autism, then mice with the same genetic mutation should have some behavioral features of autism,” Dougherty explained.

When the researcher bred mice without the CELF6 gene they discovered they had less serotonin in the brain and also displayed some of the same behaviors as autistic children/ Mouse pups had difficulty vocalizing when they were removed from their mother.

In another experiment the researchers exposed the mice to a variety of scents including chocolate, which was new. They were later allowed to consume the treat. The next day healthy mice vigorously explored the scents again - especially chocolate. Mice without the gene showed no change in behavior, much like children with autism.

“Our results suggest that we have found a mechanism by which a genetic mutation can disrupt serotonin signaling and lead to behavior that is characteristic of autism,” Dougherty says. “Serotonin signaling is just one biological pathway that can be interrupted in patients with autism. We think similar investigations can find other pathways that may be important in this disease.”

Journal of Neuroscience
February 13, 2013.

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