"Environmental factors might be important, but we don't know which or how much they affect the development of this disorder," Chakravarti said. "But I'm very confident that this is a first step in a series of steps we need to take to study autism with some measure of comprehensiveness before we can estimate the totality of meaning for the role of environmental factors."
In another lab across the country, researchers at UCLA landed upon the same gene — CNTNAP2 — as a possible candidate for autism. But the UCLA researchers identified the specific role this gene might play in affecting language, thought and behavior for people with autism.
Taking a different approach, these investigators used data from the Autism Genetic Resource Exchange and studied the DNA of 291 families nationwide who had at least one autistic child. They also found that an unusually high number of the autistic subjects had this gene variant.
To verify their findings, researchers studied the DNA of a new group of 304 families and found that the CNTNAP2 gene variant showed up consistently in the autistic subjects.
Moreover, researchers took a closer look at the gene to see how it might bring about autism. Daniel Geschwind, principal study investigator and director of the UCLA Center for Autism Research, said they discovered that in young children, the gene was most active in language and thought.
"We found that the longer the language delay an autistic child had, the more likely they were to have the CNTNAP2 variant," Geschwind explained. "So having this variant at least partially explains amount of language delay in autism."
A third study released in the same journal identified specific mutations on the same gene, which were individually rare for each autistic patient. Researchers at Yale University sequenced the entire gene and found that autistic patients often had unique mutations on the gene, which were not found in any members of the healthy control group.
This finding exemplifies the complexity of the findings on this gene as well as the disorder itself, said Dr. Matthew State, principal investigator of the study and director of the Program on Neurogenetics at Yale University. He noted that even though his team took a different approach to unlocking the possible genetic causes of autism than the other two teams, "we still landed on the same gene which is quite interesting, but more work needs to be done to sort out what's going on here."
Many experts support Chakravarti's belief that this research adds to the evidence that genetic factors play more of a role in the development of autism than environmental factors.
"Environmental factors in autism is a separate issue," said Carla Mazefsky, assistant professor of pediatrics and psychiatry at the University of Pittsburgh School of Medicine. "Given autism's strong genetic basis, identification of genes that play a role is of critical importance. This study further emphasizes the complexity of the genetics underlying autism."
"Autism is a disorder of fetal or early postnatal brain development with a genetic origin," agreed Vittorio Gallo, director of the Center for Neuroscience Research at the Children's National Medical Center in Washington, D.C.