Gene Plays Role in Risk of Autism

THURSDAY Jan. 10, 2008 -- A gene that appears to play a key role in the development of autism has been identified by three different teams of researchers.

UCLA scientists found that the gene -- contactin-associated protein-like 2 (CNTNAP2) -- is most active in brain regions involved with language and thought and that the presence of the gene may explain speech delays in children with autism.

Their study appears in the Jan. 10 online edition of The American Journal of Human Genetics.

The same issue also features reports from research teams at Johns Hopkins University and Yale University that link the CNTNAP2 gene to autism. Meanwhile, a consortium of autism researchers from the Boston area reported in the Jan. 10 issue of the New England Journal of Medicine that abnormalities on chromosome 16 seemed to raise the risk of a certain kind of autism.

The UCLA scientists noted that the gene they discovered is tied closely to language development.

"This gene not only may predispose children to autism. It also may influence the development of brain structures involved in language, providing a tangible link between genes, the brain and behavior," principal investigator Dr. Daniel Geschwind, a professor of human genetics at UCLA's David Geffen School of Medicine, said in a prepared statement.

In the study, researchers analyzed DNA samples from almost 500 families that had at least one autistic child and found that CNTNAP2 showed up consistently in the samples.

The UCLA team also examined CNTNAP2 presence in early brain tissue and found that the gene was most active in developing brain structures involved in language and thought.

Researcher Brett Abrahams, a postdoctoral fellow, explained the significance of the finding by comparing the brain to a house.

"We know that different rooms in houses serve different purposes. For example, if an item only appears in the kitchen, it makes sense to assume it's involved in cooking. Or if we find an object only in the bedroom, it's likely connected to sleeping," he said in a prepared statement. "The fact that we found CNTNAP2 concentrated in the brain's structures that are involved in higher cognition gives us strong clues about how its disruption might adversely shape brain development, including speech and language."

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.

Posted: January 2008


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