While researchers have long suspected that genes play a role in autism, they still haven't figured out how much. New research out today, however, suggests that it may be greater than expected. A set of gene variants that occur up to 20 percent more often in autistic children may be responsible for about 12 to 18 percent of cases of autism, according to a study published today in the journal Nature. This altered piece of DNA lies near a gene that's responsible for the transmission of signals between the brain's nerve cells.
So what does this mean for the parents of autistic children? U.S. News spoke to study leader Hakon Hakonarson, director of the Center for Applied Genomics at the Children's Hospital of Philadelphia.
Do these genetic findings apply to all cases in autistic spectrum disorder—severe, mild, and everything in between?
Yes. After we ran statistical tests, we found a significant association between this gene variant and an individual's risk of autism. Where previously we only identified variants responsible for less than 1 percent of autism cases, these variants are responsible for far more. We've known that autism runs in families, that those with one autistic child are more likely to have a second. We've also known that there's a stronger correlation of autism between identical twins compared to fraternal twins. But now we can point to why. It's a totally different ballgame now.
There's a possibility that we may be able to eventually do gene therapy to fix these variations that are causing autism. We may come to a point where we can diagnose the genetic defect before babies develop autism—which usually sets in around 2 to 3 years old—and then be able to administer therapy before those brain connections are disrupted. This, though, is years down the road, but at least it points the way to new research.
Does this mean that environmental factors don't play a role in autism?
Not at all. I think it's very likely that there are other factors. Otherwise, all the children who had these variants would get autism, and that's not the case. There could be additional gene mutations involved or environmental factors that are turning these genes on. I think there's probably an interaction between genes and lifestyle factors, including a mother's diet in utero, the age of the parents at a baby's conception, or chemicals a baby may have been exposed to. We just don't know at this point.
So what's the next step?
Creating a mouse model where we knock out a particular gene that's near these variants. We'll then insert a normal gene to see what effect it would have on these variants. Once we can study how these genes and variants interact in animals, we can go on to humans.