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Genetic Mutations May Be Key Cause of Autism

Study Shows Changes in DNA Are Linked to Autism

Autism Gene Studies: What's Next?

Studies under way are trying to link specific sets of CNVs to specific autism symptoms. Once this is done, genetic testing for CNVs could help parents identify children at high risk of autism, says study researcher Geri Dawson, PhD, of the advocacy group Autism Speaks.

"I can imagine a day when one can identify the specific genetic risk that led to an individual child's autism, and then using that genetic information to say what pathway has been affected and then choosing a medical intervention," Dawson said at the news conference.

There are no such medical treatments, although there are drugs that affect some of the pathways now linked to autism.

The new findings also shed light on the puzzling question of why children with severe autism may have brothers and sisters -- even identical twins sharing 100% of their genes -- who are unaffected.

Many of the CNVs identified in the study have what geneticists call "incomplete penetrance." This means that even if a person carries an autism-linked CNV in his or her genome, there's a chance it will have no effect.

This poses a problem for genetic testing, as children found to have autism-linked CNVs won't necessarily have autism. According to Scherer, the genes identified in the study would aid in early autism diagnosis in only about 10% of families.

Autism isn't the first disease to be linked to CNV's affecting brain function. CNV variants -- affecting some of the same pathways affected by autism-linked CNVs -- also play a role in intellectual disability (formerly called mental retardation) and schizophrenia.

Might CNVs be the long-sought factor that might make some children more susceptible to the risks posed by environmental toxins or even vaccinations?

"We do believe that environmental factors play a role in autism," Dawson said. "It is important as we continue with our science to learn how environmental factors interact with the genes we have identified here. But as of now, there is no evidence that vaccination is one of these factors."

The study findings appear in the June 9 online issue of the journal Nature.

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