Spontaneous mutations influence autism risk, researchers find

Studies identify link between disorder and paternal age

Three separate teams of researchers have identified several gene mutations that they believe sharply increase the risk of developing autism, according to a trio of studies published in Nature.

Scientists for decades have debated the influence of inherited and environmental factors on autism, and most today believe there is a strong genetic component. However, researchers have struggled to develop a clear understanding of the underlying genetics associated with autism spectrum disorders, which CDC says affect one in 88 children on average.

The three teams of researchers all analyzed genes from blood samples of families in which parents without autism gave birth to a child who developed the disorder. Specifically, the scientists focused on "de novo" mutations, which occur sporadically near or during conception.

"We found that 15% to 20% of sporadic patients could be explained by 'de novo' mutations," said Evan Eichler, professor of genome sciences at the University of Washington, who led one of the studies. Meanwhile, the second study—led by Yale University researchers—found that at least 14% of autism patients had multiple genetic mutations, which NIH says is five times the normal rate.

The third study, conducted by Harvard University researchers, found that nearly half of children in the study had spontaneous mutations, but that the rate was comparable among children with and without autism.

According to HealthDay, the findings do not suggest that the frequency of de novo mutations is significantly higher among autistic children; rather it indicates that the types of mutations are more detrimental in autistic children than their non-autistic siblings.

The studies also found evidence that the risk of de novo mutations increases alongside paternal age. For example, Eichler's team found that the mutations were four times more likely to be inherited from the father, and that the risk was higher for fathers at age 35 than 25. However, they noted that paternal age probably only plays a role in about 10% of cases (Storrs, HealthDay, 4/4; Carey, New York Times, 4/4; Falco, CNN, 4/5).

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