Genetic analysis: Rare mutations cause half of all autism cases

COLD SPRING HARBOR, N.Y., Sept. 22 (UPI) -- Researchers found that rare mutations of a set of genes could be responsible for roughly half of all autism spectrum disorder, or ASD, cases. The "spontaneous" genetic mutations, researchers said, most likely happen to genes that are essential for normal brain development.

The new theory differs from a commonly held one that ASD is caused by a combination of genetic mutations that are harmless individually but when combined cause the disorder. Instead, researchers say mutations present in a germ cell or fertilized egg can result in ASD.

"Devastating de novo mutations in autism genes should be under strong negative selection," said Michael Wigler, a professor at Cold Spring Harbor Laboratory, in a press release. "And that is among the findings of the paper we're publishing today."

The study revealed vulnerable "autism genes" tend to have fewer mutations than most human genes.

Researchers analyzed data on ASD patients and their families collected as part of the Simons Simplex Collection, finding there are about 200 "candidate" autism genes that may be vulnerable to the mutations.

Genes considered vulnerable harbor what the researchers refer to as likely gene-disruption, or LGD. LGD spontaneous mutations occur between generations, and researchers said they were often carried by the mother and passed down.

"Our analysis also revealed that a surprising proportion of rare devastating mutations transmitted by parents occurs in genes expressed in the embryonic brain," Wigler said. The findings suggest at least some mutations that result in ASD occur in genes critical to brain development.

Such mutations are often not passed on, as most people with severe ASD do not reproduce.

The study is published in the Proceedings of the National Academy of Sciences.