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New Clues on Genetic Causes of Autism

Research Also Sheds Light on Why Boys Are More Affected by Autism Than Girls

Autism Genes: Girls vs. Boys

In a second study, researchers from Cold Spring Harbor Laboratory and other institutions analyzed the same families. They used a similar approach.

They, too, confirmed a contribution from the sporadic mutations. They estimated the number of regions involved even higher, at up to 300.

They also found that girls appear to have a greater resistance to autism from genetic causes than do boys.

''When we looked at affected females, we don't see small mutations, but very large mutations," says Michael Ronemus, PhD, a researcher at Cold Spring Harbor Laboratory. "Girls are more resistant," he says. It appears to take a larger mutation to affect girls with autism compared with boys.

It's long been known that boys are much more likely to get autism than are girls.

In a third report, Ronemus and his colleagues developed a method for analysis of the genetic associations. They used a new method to help identify a network of genes affected by the rare mutations in autism.

"The genes we are finding are typically involved in early brain development, forming connections in the brain," Ronemus says. These genes are related to the development of synapses, the point of connection between two nerve cells, among other tasks, the researchers say.

Genetic Causes of Autism: Implications

While the new research provides more clues to the genetic underpinnings of autism, "the message is not 'go out and get tested,'" says Sanders."We really are not at that stage yet."

The new research provides new information ''but also confirms a lot of things we have already known,"  says Andy Shih, PhD, vice president of scientific affairs for Autism Speaks, an advocacy and research organization.

"It confirms that rare copy number variants are the main risk factors for many families," he says. However, he says, it also confirms that it's still impossible to explain the majority of cases of autism.

The sporadic mutations appear to play more of a role in families with just one child affected, Shih says. Eventually, the genetic findings could be useful information during genetic counseling in families who have one affected child, he says.

The findings are called a critical first step in the eventual goal of developing targeted treatments.


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