Scientists have found several types of rare, genetic differences in more than 14,000 DNA samples from parents, affected children, and unrelated individuals that are linked to increased risk of autism.
According to a study led by Mount Sinai researchers and the Autism Sequencing Consortium, the number of definitive autism genes has been increased to almost fourfold to 33, compared to the 9 genes most closely tied to risk in recent years by similar studies in several labs. It also identified more than 70 additional, likely ASD genes. Each of these genes is mutated in more than 5 percent of individuals with autism, signifying a large, relative contribution to risk for a complex genetic disease.
By casting a wider net, a research team from 37 institutions found that previously unsuspected sets of genes may be involved in ASD risk, including some that control how nerve networks form in the brain. Occurring in one out of 68 children in the US, ASD affects a person's social interactions, including communication, as well as behaviors with varying levels of severity.
Joseph D. Buxbaum, PhD, Professor of Psychiatry, Neuroscience and Genetics and Genomic Sciences at the Icahn School of Medicine at Mount Sinai and Director of the Seaver Autism Center, said that the steps they added to their analysis over past studies provide the most complete theoretical picture to date of how many genetic changes pile up to affect the brains of children with autism.
The study authors were able to assess the effects of both inherited genetic differences and those that happen spontaneously in the sperm and eggs that go on to form human embryos. While small, rare genetic differences in the top 107 genes were found to confer a relatively large jump in a person's risk, many more changes in other genes add smaller amounts of risk. According to the authors, the interplay between gene variations, both common and rare, holds the key to understanding autism.
Along these lines, the team, by looking at how many times variations occurred in each of the 107 genes, was able to predict that small differences in about 1,000 genes will eventually be found to increase autism risk.
The study was published in the journal Nature.
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