The results of three new studies, published in the journal Nature, suggest mutations in parts of genes that code for proteins - called the exome - play a significant role in autism.
And while these genetic mistakes can occur across the genetic code, and many are harmless, they can cause big problems when they occur in parts of the genome needed for brain development. One of the three teams found these glitches may result in a five to 20 times higher risk of developing autism.
"These results confirm that it's not the size of the genetic anomaly that confers risk, but its location," said Dr. Thomas Insel, director of the National Institute of Mental Health, one of the National Institutes of Health, which funded one of the studies.
Among the other findings, the teams - led by Mark Daly of the Broad Institute at Harvard and Massachusetts Institute of Technology, Dr. Matthew State of Yale University and Evan Eichler of the University of Washington in Seattle - identified several hundred new suspect genes that could eventually lead to new targets for autism treatments.
Many of the researchers were part of the Autism Sequencing Collaborative, the largest effort of its kind to use advanced gene sequencing technology to identify the genetic underpinnings of autism.
Autism encompasses a wide spectrum of disorders, ranging from profound inability to communicate and mental retardation to relatively mild symptoms, as in Asperger's syndrome.
Scientists previously have found dozens of genes that may raise the risk of autism. But genetic causes only explain about 10 percent of cases, and recent studies have pointed to environmental factors, possibly arising at conception, as a potential trigger.
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