April 20, 2018
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New mutations in autistic people may be due to older fathers

By Elizabeth Lopatto, Bloomberg News

NEW YORK — Newly found gene mutations tied to autism may one day help scientists classify types of the developmental disorder and shape treatments based on their DNA profiles, researchers said.

The mutations aren’t found in parents of autistic people, and don’t guarantee children will have autism, the scientists found. Some, though, are more common in children of older fathers, with the risk rising as the men age, according to one of three papers reported Wednesday in the journal Nature.

One in 88 U.S. children have autism spectrum disorders, according to a federal report last week. Although the disorders are classed together, symptoms are frequently different and DNA may hint at ways to group similar patients, said Evan Eichler, a professor of genome sciences at the University of Washington in Seattle and a study author.

“The analogy I’m hearing, and it’s being used increasingly, is that it’s like cancer,” said Andy Shih, vice president for scientific affairs at Autism Speaks, who wasn’t involved in the research. “The analogy is apt; many researchers say we aren’t looking at a single disorder.”

Cancers have similar clinical presentations: rapidly dividing cells. However, the way that these malignant cells come to divide varies widely, depending on genetic and environmental risk factors. Autism is probably similarly varied, Shih said.

All three studies in Nature looked at spontaneously- arising, or de novo, mutations in genes that code proteins. These mutations occur in egg and sperm cells, and become more frequent in children as parents age, increasing every decade.

“We’ve identified a subset to study more intensely, and we could apply therapies if there are any down the road,” Eichler said in a telephone interview. More practically, he said, the findings may be used by families to find and group together patients with similar symptoms.

“I’ve seen that be beneficial,” Eichler said. “They say things like, ‘My Johnny was never like the others,’ and now there’s a group of people with practical solutions for dealing with this specific form of developmental delay.”

Being able to make a connection with parents in similar situations can reduce stresses on the families and can improve patients’ situations, he said.

Matthew State, the author of one of the papers and a neurogeneticist and psychiatrist at Yale University, said a greater rate of mutation was found in patients with older parents. His research found mutations that disrupted genes expressed in the brain, suggesting multiple new variants that may be risk factors.

“Any one of those can hit a gene that’s relevant for autism,” he said, adding that fathers’ contributions are particularly important, as they contributed 4 times the mutations that mothers did.

The technology to identify these spontaneous mutations didn’t exist as recently as 3 years ago, said Benjamin Neale, an assistant in genetics at Massachusetts General Hospital in Boston. The majority of the population has at least one de novo mutation; the question is which ones may confer risk for autism and other specific disorders.

“We want to know what genetic risk factors predispose toward autism so we can improve prediction,” Neale said. ‘But also we want to know what biological processes are involved, so we can understand neurobiology and treatment.”

The discoveries described Wednesday should help scientists gain insights about how autism affects the developing brain, which can be challenging to do, he said. Neale’s study found many de novo mutations aren’t connected to the disease, and those that do many not necessarily cause autism in all people.

The candidate list is “excellent,” and more work will have to be done in order to understand what genes will be important, Neale said.

The research was sponsored by the National Heart, Lung, and Blood Institute, the Simons Foundation Autism Research Institute, the National Institutes of Health and other groups. Autism Speaks funds some of the researchers involved and assisted with sample collection, Shih said.

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