A plethora of genetic changes contributes to autism spectrum disorders, three new studies find. The new genetic data illustrate why researchers have struggled to find a single cause for the baffling suite of developmental and behavioral conditions, and may help point the way to a unifying process underlying them. The studies also begin to explain why autism spectrum disorders are more common in boys than girls.
Though the specific genetic changes identified by a trio of papers in the June 9 Neuron account for only 5 to 8 percent of autism cases, what they reveal about the biology of autism may have much wider implications.
“I think we’re still scratching the surface,” says Steve Scherer of the Hospital for Sick Children in Toronto, who wasn’t involved in the studies. “But we’re getting there, and I think these are very important papers.”
Two of the studies examined DNA samples taken from carefully screened families, a cohort called the Simons Simplex Collection. Each family included two unaffected parents and one high-functioning child diagnosed with autism spectrum disorder. For most families, an unaffected sibling was also included. By studying genetic changes in unaffected family members, the researchers could find abnormalities — specifically, duplications and deletions of DNA called copy number variations — that were not passed down from parents but arose spontaneously in the genomes of affected children.