July 21, 2014
redOrbit Staff & Wire Reports Your Universe Online
The majority of the genetic risks for developing autism can be traced to common versions of genes, not rare variants or spontaneous mutations, according to the results of a National Institutes of Health-funded study that appeared in Sundays edition of the journal Nature Genetics.
In total, approximately 52 percent of the risk for autism was traced to common or rare inherited variation, while spontaneous mutations comprised just 2.6 percent of the overall risk, a team of researchers led by Dr. Joseph Buxbaum of the Icahn School of Medicine at Mount Sinai (ISMMS) in New York reported in the paper.
In addition, heritability was also found to outpace other risk factors. The study is said to be the largest of its kind, and the Population-Based-Autism Genetics and Environment Study (PAGES) Consortium researchers behind the paper claim that their findings indicate that inheritability outweighs environmental risk.
Dr. Buxbaum and his colleagues conducted a rigorous analysis of DNA sequence variations from an ongoing, comprehensive study of autism in Sweden. Health registry data from 3,000 patients, some of whom were autistic individuals and some belonging to a control group, was analyzed for the purposes of the study.
We show very clearly that inherited common variants comprise the bulk of the risk that sets up susceptibility to autism, explained Dr. Buxbaum, is an ISMMS professor as well as the director of the Seaver Autism Center for Research and Treatment. But while families can be genetically loaded for autism risk, it may take additional rare genetic factors to actually produce the disorder in a particular family member.
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, added Dr. Thomas R. Insel, director of the NIHs 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.
While autism is believed to be caused by the interplay of genetic and other factors, scientists have never been able to reach a consensus on the relative contributions of those factors, the researchers said. Recent research has uncovered mounting evidence that the genomes of autistic men and women are likely to contain de novo mutations rare, spontaneous mutations with strong effects that are largely to blame for certain cases of the ailment.
Many people have been focusing on de novo mutations, such as the ones that can occur in the sperm of an older father. While we find these mutations are also key contributors, it is important to know that there is underlying risk in the family genetic architecture itself, Dr. Buxbaum said.
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Common Variants Responsible For Most Genetic Risk Of Autism