Autism gene found?

University of Utah researchers are part of a worldwide consortium that has identified a gene that may predispose people to autism.

According to research released Sunday morning, the gene, neurexin 1, helps the brain cells form connections that transmit nerve impulses. The findings, which are part of ongoing research, was funded by a national nonprofit organization named Autism Speaks and the National Institutes of Health. They were published Sunday in Nature Genetics.

The Autism Genome Project, which includes the U. and 50 other institutions in the United States, Canada and Europe, embedded 10,000 DNA markers on a silicon microchip, then used it to analyze genetic samples taken from 1,200 families with siblings who have autism. It was a challenge to amass because the chance a family with an autistic child will have another with the condition is only 5 percent, said Dr. William M. McMahon, professor of psychiatry at the U. and co-investigator at the U. with Hilary Coon, Ph.D. research professor of psychiatry.

"The network put together the largest sample ever assembled of families that have more than one child with autism," he said. "Multiple-incidence families are uncommon and to make progress understanding the genetics of autism, we have to pool these families with other groups. It is remarkable cooperation."

The result showed a strong statistical signal on the short arm of chromosome 11, exciting to the researchers because that region includes the neurexin 1 gene, which has been implicated in previous studies of autism.

The next step, he said, will involve looking for sequence changes in the neurexin gene code and other genes on chromosome 11 that are also possibilities. Neurexin's role in brain cell communication makes it especially interesting. "We believe autism is a disease caused by faulty brain connections and it's exciting to have linkage in an area where there's such a good candidate gene."

He said a study of autism in twins suggests genes are very important. When one identical twin has autism, 60 percent of the time the other does, as well, suggesting genetic influences on the disorder. "But it's likely that the genetic influences work in concert with environmental factors as triggers," McMahon said.

He likens autism today to the term "fever" in the 17th century. "We recognize the external manifestations of it, but there are probably many causes. It may turn out there are 20 genes or more and several environmental factors that work in concert."