Common gene variants account for most genetic risk for autism
Most of the genetic risk for autism comes from versions of genes that are common in the population rather than from rare variants or spontaneous glitches, researchers funded by the National Institutes of Health have found. Heritability also outweighed other risk factors in this largest study of its kind to date.
About 52 percent of the risk for autism was traced to common and rare inherited variation, with spontaneous mutations contributing a modest 2.6 percent of the total risk.
“Genetic variation likely accounts for roughly 60 percent of the liability for autism, with common variants comprising the bulk of its genetic architecture,” explained Joseph Buxbaum, Ph.D., of the Icahn School of Medicine at Mount Sinai (ISMMS), New York City. “Although each exerts just a tiny effect individually, these common variations in the genetic code add up to substantial impact, taken together.”
Buxbaum, and colleagues of the Population-Based Autism Genetics and Environment Study (PAGES) Consortium, report on their findings in a unique Swedish sample in the journal Nature Genetics, July 20, 2014.
“Thanks to the boost in statistical power that comes with ample sample size, autism geneticists can now detect common as well as rare genetic variation associated with risk,” said Thomas R. Insel, M.D., director of the NIH’s National Institute of Mental Health (NIMH). “Knowing the nature of the genetic risk will reveal clues to the molecular roots of the disorder. Common variation may be more important than we thought.”
Although autism is thought to be caused by an interplay of genetic and other factors, including environmental, consensus on their relative contributions and the outlines of its genetic architecture has remained elusive. Recently, evidence has been mounting that genomes of people with autism are prone to harbouring rare mutations, often spontaneous, that exert strong effects and can largely account for particular cases of disease.
More challenging is to gauge the collective impact on autism risk of numerous variations in the genetic code shared by most people, which are individually much subtler in effect. Limitations of sample size and composition made it difficult to detect these effects and to estimate the relative influence of such common, rare inherited, and rare spontaneous variation.
Differences in methods and statistical models also resulted in sometimes wildly discrepant estimates of autism’s heritability – ranging from 17 to 50 percent.
NIH
