Gene Plays Role in Risk of Autism

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The UCLA researchers also found that the gene was strongest in families with autistic boys, compared to families with autistic boys and girls or families with autistic girls only.

"Autism strikes boys three times as often as girls," Maricela Alarcon, first study author and an assistant professor in residence of neurology at UCLA, said in a prepared statement. "This finding may partly explain why."

In the Johns Hopkins study, researchers found that a specific variation in the structure of CNTNAP2 makes a child more vulnerable to developing autism. They looked at more than 1,300 children with autism and their parents and found that where a single segment of the genetic code of CNTNAP2 could contain either the chemical base adenine or thymine, children with autism tended to have the thymine variant.

The researchers also found that children with autism were about 20 percent more likely to have inherited the thymine variant from their mothers than from their fathers.

"This is a common variant. People inherit it all the time. Our finding that it's associated with autism more often when it's inherited from mothers is intriguing, but needs to be replicated," Johns Hopkins researcher Aravinda Chakravarti said in a prepared statement.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about autism.