Scientists Find First Definitive Genetic Links to Autism

Scientists have uncovered several gene mutations that sharply increase the chances of developing autism. It's the first time researchers have pinpointed a specific genetic component with the spectrum of disorders, which includes Asperger's.

They also found that the risk is higher in older parents, in particular new fathers over 35. The findings are published in three papers in the journal Nature.

A Genetic Autism Roadmap

The mutations are rare and account for a small number of actual cases, which have reached the alarming rate of one in every 88 children, according to a Centers for Disease Control and Prevention report released last week. Despite the small numbers, the discovery of the mutations is significant because it gives scientists a road map to further explore Autism's biology. Follow-up research, The New York Times reports, could uncover enough rare mutations to account for up to 20 percent of Autism spectrum cases.

Some researchers, however, were more cautious about the significance of the research:

"This is a great beginning, and I'm impressed with the work, but we don't know the cause of these rare mutations, or even their levels in the general population," said Dr. Aravinda Chakravarti of the Institute of Genetic Medicine at the Johns Hopkins University Medical School, who was not involved in the studies. "I'm not saying it's not worth it to follow up these findings, but I am saying it's going to be a hard slog."

Too Rare to be Coincidence

The three teams looked at DNA taken from blood samples of families in which parents have no signs of autism, but their children developed the disorder. They focused on rare genetic glitches called de novo mutations, which aren't inherited. They happen around the time of conception, are common, and are usually harmless. But these new studies indicate that kids with autism have a slightly higher rate. One team studied 200 people with autism along with parents and siblings without it. Two unrelated children with autism had de novo mutations in the same gene. The scientists say the chances of that being a coincidence are incredibly low—and the chance of the mutations being related to autism risk are "something like 99.9999 percent." The other two teams came up with similar findings.

Older Parents

One group found that de novo mutations were four times more likely to come from DNA from dads rather than moms. They also found that it is more likely as dads get older, which jives with previous research that associates older fathers with the increase in autism cases across the country.

Overall, the implications of the study itself are minor, and developing a treatment or cure based on the findings is an extremely long way off. And it's important to keep in mind that most diseases likely have both an environmental and a genetic component.

"These low frequency genetic links do not explain the majority of the disease," said Michael Skinner, a reproductive biology professor at Washington State University. "[The study is] interesting, but suggests the majority of disease is not explained through genetic abnormalities."

Science is frustratingly incremental, but these papers at least give scientists solid ground for future work. [The New York Times, Nature]

Image: Shutterstock/Aaron Amat