Risk of Autism May Be Increased by Rare Gene Mutations

A study funded by the National Institute of Mental Health (NIMH) and other institutions indicates that the risk of autism spectrum disorders (ASDs) may be increased by very small, rare gene mutations. The increased risk appears to be greater than experts had thought.

The study's results were published on March 16 online in Science Express.

Researchers examined genetic material from 264 families. They specifically searched for genetic mutations which were present in children but not in either of their parents. The research team found "spontaneous" mutations in 14 of 195 patients with ASDs and in only 2 of 196 healthy control subjects. Of the 14 ASD patients who showed mutations, 12 were the only individuals in their families who had an ASD, and 2 had at least one case of an ASD in their families.

"These structural variations are emerging as a different kind of genetic risk for autism than the more common sequence changes in letters of the genetic code that we've been looking for," explained NIMH director Thomas Insel, M.D. "The best evidence yet that such deletions and duplications are linked to the disorder, these findings certainly complicate the search for genes contributing to autism. These are rare changes, dispersed across the genome, and they tell us that autism may be the final common path for many different genetic abnormalities."

"Our results show conclusively that these tiny glitches are frequent in autism, occurring in at least ten percent of cases, and primarily in the sporadic form of the disease, which accounts for 90 percent of affected individuals," added Sebat. "Understanding such sporadic autism will require different genetic approaches and stepped-up recruitment of families in which only one individual has the disease."