Despite what you may hear from a very vocal celebrity wing of Twitter (seriously, Jim Carrey, just stop), vaccines don’t cause autism. But the true cause of the developmental disorder has yet to be determined. Many scientists tend to think there is a strong genetic basis, but the evidence hasn’t been definitive. Some new research out of Australia, however, sheds some more light on which genes are implicated, and what role they play.

In what’s being touted as a first-of-its-kind study, neuroscientists and geneticists from the University of New South Wales in Sydney say they’ve identified a link between mutations in certain gene segments and symptoms of autism. The researchers pinpointed more than 100 chunks of DNA known as enhancers, which control gene activity in the brain.

Trying to find the right mutations that lead to disease is no easy task. More than 95 percent of the DNA in the human body doesn’t code for any proteins, so there’s no discernible role for them in causing brain disorders. Some of this junk, however, does play a role as enhancers — which are essentially able to turn the coding genes off and on. This is crucial, since certain proteins are necessary for some parts and processes of the body, but useless (and potentially dangerous) elsewhere.

In a lengthy process involving gene activity maps and testing on brain tissue, the researchers found which enhancers were more active in the brain than in other tissues. After seeing which enhancers were more active and comparing them to mutations that were already known to lead to other brain disorders — they found a positive correlation between certain mutations and autism.

These findings suggest that enhancers play a role in progression of the disorder.

The researchers don’t know how these enhancer mutations occur, or exactly how the effects can be reversed. But the results are yet another step in an increasingly mounting pile of data that links autism to genes — and not vaccinations or other crazy theories. It’s unclear how much Jenny McCarthy and her ilk will be persuaded, but hey — one can hope!

Photos via Flickr user Spanish Flea