Major Gene Study Points to Causes of Autism

SUNDAY, Feb. 18 (HealthDay News) -- The largest study of the genetics of autism ever conducted, involving DNA from almost 1,200 affected families worldwide, has already yielded two important clues to the poorly understood disorder, scientists say.

Discoveries in two areas of the genome -- a region on chromosome 11 suspected of having links to autism, and aberrations in a brain-development gene calledneurexin 1-- could spur more targeted research, the experts noted.

"That's the real promise here," said Autism Genome Project co-researcher Dr. Stephen Scherer, director of the Center for Applied Genomics at The Hospital for Sick Children in Toronto. "When you identify certain genes, you can then develop genetic tests -- in some cases prenatal and in some cases postnatal -- because early diagnosis is crucial here."

Genetic discoveries can also further research toward a cure for autism, Scherer said.

"When we have this type of knowledge, we can actually think about designing better therapies based on what we know isnothappening properly in the [brain] cell. We can try and design things to make it work better," he explained.

The Autism Genome Project was funded by the U.S. National Institutes of Health and the nonprofit advocacy group Autism Speaks. Its findings were published in the Feb. 18 online edition ofNature Genetics.

Autism remains a real health crisis, with the U.S. Centers for Disease Control and Prevention announcing recently that one in every 150 American 8-year-olds now have some form of autistic spectrum disorder. That number is higher than prior estimates, and the debate rages as to just why the disease might be becoming more prevalent.

Experts agree that autism's causes remain cloaked in mystery, although prior research has pointed to a strong genetic component. For example, "there's about 90 percent concordance [of autism] between identical twins -- that's a significant genetic contribution," Scherer said.

So, the Autism Genome Project, which took five years to complete, sought to probe much deeper into the DNA driving the disorder. The project involved more than 120 scientists working at 50 institutions in 19 countries. They painstakingly sought out almost 1,200 families worldwide in which at least two members were affected by autism. The scientists then collected DNA samples from family members and analyzed these samples in the most advanced and standardized manner, looking for genomic "commonalities."

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.