SCOTT SIMON, HOST:
Autism spectrum disorder has multiple causes and a wide range of symptoms. But scientists say they found a brain abnormality that seems to exist in all people with the disorder. NPR's Jon Hamilton reports that the finding, if it holds up, could lead to new treatments.
JON HAMILTON, BYLINE: Autism has been linked to everything from genetic mutations to infections during pregnancy. Yet many scientists think the brains of people with autism must have something in common, something that accounts for symptoms like social difficulties and repetitive behaviors. Brady Maher is a researcher at the Lieber Institute for Brain Development in Baltimore.
BRADY MAHER: The idea is that there is some kind of common pathway that is leading to this disorder.
HAMILTON: And Maher is part of a team that thinks they've found one. The discovery came while they were studying a rare gene mutation. It causes something called Pitt-Hopkins Syndrome.
MAHER: Children that have this mutation have autistic features. They have communication deficits and repetitive behaviors.
HAMILTON: The team noticed that in mice, this mutation seemed to affect a substance called myelin. Myelin is what insulates the nerve fibers that carry electrical signals in the brain. Maher, who is also on the faculty at Johns Hopkins University, says at first, the team had doubts about their discovery.
MAHER: This was such a strong signal that we just had to go and see if this was true. And so we just started to do experiments. And sure enough, there was a clear deficit.
HAMILTON: A deficit involving the cells that produce myelin. And that made the team wonder whether myelin might be a problem in other forms of autism. So they studied several mouse models of the disorder. Dr. Daniel Weinberger, who directs the Lieber Institute, says the mice confirmed their hunch.
DANIEL WEINBERGER: They seemed to have, also, an abnormality in the development and function of these very specific cells which make this lining of the nerve fibers.
HAMILTON: But mice don't get autism. So the team studied the brains of people on the autism spectrum using tissue taken during autopsies. And Weinberger says, once again, there were problems with the cells that produce myelin.
WEINBERGER: That was surprising because this had never previously been seen to be a common feature of all these different forms of autism.
HAMILTON: But he says the explanation makes sense.
WEINBERGER: This process of laying down myelin in the human brain really does not start in earnest until the first year or two of life. And this is around the time that autism is first apparent.
HAMILTON: If the cells that make myelin really are a big factor, it might offer a new approach to treatment. Scientists are already working on drugs to reverse the loss of myelin in people with multiple sclerosis. And Brady Maher says this sort of drug might also help children with autism.
MAHER: If we could get to these kids really early and begin treatment as soon as we diagnose this, that might be a critical window that we could really sort of change their developmental trajectory and improve their outcome.
HAMILTON: But first, scientists will need to confirm the link between autism spectrum disorder and myelin. Then they'll need to figure out how to tweak cells that make the substance in just the right way. Dr. Flora Vaccarino at Yale School of Medicine says that will be tricky because autism varies from child to child.
FLORA VACCARINO: In children with autism, you have some children that have a very large brain and some children that have a normal or smaller brain.
HAMILTON: So it could be that some kids are making too much myelin and others too little. Also, Vaccarino says, the brain's own system for regulating substances like myelin is a wonder.
VACCARINO: It's actually so complex that it's almost unfathomable to sort of think about, how is it done just right?
HAMILTON: Let alone try to fix the process when it's gone wrong. The myelin study appears in the journal Nature Neuroscience. Jon Hamilton, NPR News.
(SOUNDBITE OF SYBARITE'S "GREY SKY BRIGHT")
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.