Feb. 12, 2013 Scientists at Washington University School of Medicine in St. Louis have identified a genetic mutation that may underlie common behaviors seen in some people with autism, such as difficulty communicating and resistance to change.

An error in the gene, CELF6, leads to disturbances in serotonin, a chemical that relays messages in the brain and has long been suspected to be involved in autism.

The researchers identified the error in a child with autism and then, working in mice, showed that the same genetic alteration results in autism-related behaviors and a sharp drop in the level of serotonin circulating in the brain.

While the newly discovered mutation appears to be rare, it provides some of the first clues to the biological basis of the disease, the scientists report Feb. 13 in the Journal of Neuroscience.

"Genetically, autism looks very complicated, with many different genetic routes that lead to the disease," says lead author Joseph D. Dougherty, PhD, an assistant professor of genetics at Washington University. "But it'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."

Autism is known to have a strong genetic component, but the handful of genes implicated in the condition so far explain only a small number of cases or make a small contribution to symptoms.

This led Dougherty and senior author Nathaniel Heintz, PhD, a Howard Hughes Medical Institute investigator at Rockefeller University, to speculate that some of the most common behavioral symptoms of autism may be caused by disruptions in a common biological pathway, like the one involved in serotonin signaling.

Some 30 percent of patients with autism have abnormal blood levels of serotonin. The chemical messenger plays an important role throughout the body, helping to regulate breathing, temperature and sleep as well as mood and learning. But it is produced by only a limited number of neurons in the brain.

Using a new molecular technique, the researchers exclusively targeted serotonin-producing neurons in healthy mice to look for genes that are "turned on" in these cells. They found nearly 200 genes involved in this process.

Then, they searched for variations in these genes in some 400 autistic children, whose DNA was made available to the scientists through the Autism Genetic Resource Exchange.

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Some autism behaviors linked to altered gene

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