Gene mutation contributes to autism

US researchers estimate there are likely about 1,000 or more genes that contribute to autism spectrum disorder risk, but mutations might be the key. Dr. Daniel Geschwind, a professor of neurology and psychiatry at the University of California, Los Angeles, and colleagues from Yale University, Carnegie Mellon University and the University of Pittsburgh, completed "whole-exome sequencing" of 238 parent-child quartets. A quartet is defined as two parents and one child without autism spectrum disorder and one child with autism spectrum disorder. Whole-exome sequencing is an efficient strategy to sequence the coding regions of the genome selectively, as a cheaper but still effective alternative to whole genome sequencing. The researchers compared mutation rates between unaffected individuals and those with autism spectrum disorder within a family, and then compared autism spectrum disorder mutations to the entire study. They found multiple variations between unaffected and affected groups. Specifically, among a total of 279 coding mutations, they identified a single instance in individual children with autism spectrum disorder -- and not in siblings -- in which two independent mutations disrupt the gene SCN2A. That same mutation was found in all the unrelated children with autism spectrum disorder, confirming its importance. The study was published in the journal Nature.