Major Gene Study Points to Causes of Autism

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Those efforts have met with real success.

"First, we found several regions of the genome, particularly one region on chromosome 11, that seem to be very highly associated with the development of autism," said Scherer, who is also professor of medicine at the University of Toronto. While prior research had suggested chromosome 11 as a potential hotspot for autism-linked DNA, this study greatly strengthens that view, he said.

The researchers also used cutting-edge technologies to seek out what are known as "copy number variations" -- genes that appear not in pairs (as most genes passed down from mom and dad are), but as just a single copy, or as three or more copies.

"We found several regions of the genome -- sometimes the same region popping up in unrelated individuals -- with 3 or more copies," Scherer said. "We didn't see these in the individuals' parents, so that implies that these regions are harboring susceptibility genes for autism."

One gene in particular, called neurexin 1, appeared in some cases in just one copy. "In one family, both of the children who were autistic actually had that piece missing," Scherer said. "That's kind of a smoking gun that the gene is implicated."

It makes intuitive sense that dysfunctional neurexin 1 might play some role in autistic disorders, another expert said.

The neurexin 1 protein and its kin, "are very important in determining how properly the brain is wired up from one nerve cell to another, and in the chemical transmission of information from one nerve cell to another," said Dr. Bradley Peterson, a professor of child psychiatry at Columbia University Medical Center and the New York State Psychiatric Institute, in New York City.

Peterson, who was not involved in the project, said genes that effect early neural growth could be key to autistic disorders, since "the genetic and the non-genetic contributions to autism, by definition, have to exert their effect very early in brain development, either in utero or in the first months or couple of years of life."