Researchers have long recognized that autism runs in families, suggesting a genetic component. Yet, few genes have so far been identified and the underlying genetic nature of autism — how many genes contribute and to what extent they influence a person's chances of developing the disorder — remains poorly understood.

Now, a consortium led by several institutions, including the Perelman School of Medicine at the University of Pennsylvania, has taken a step toward addressing these questions by searching for mutations in the fraction of the human genome that codes for proteins. The researchers sequenced this region, known as the exome, in 175 autism patients and their unaffected parents, looking for single-letter DNA changes present only in the children. Their results, along with simultaneously published findings from two other research groups, suggest modest roles for hundreds of genes in the development of autism and pinpoint a few specific genes as genuine risk factors. The work is described in a paper that appears online this week in Nature.

"The genetic basis of autism is incredibly complex, and progress has been slow and frustrating," says co-author Gerard Schellenberg, PhD, professor of Pathology and Laboratory Medicine. “This study, using technology that has only become available in the past two years, is the start of finding genes that cause autism, and this work will help identify the underlying cause of this tragic disorder."

Schellenberg, co-author Li-San Wang, PhD, assistant professor of Pathology and Laboratory Medicine, and the Penn team performed some of the NextGeneration DNA sequencing used in the study.

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