25 new gene variants linked to autism

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Scientists have identified 25 gene variants that may increase the chance a person will have autism.

The 25 additional copy variations (CNVs) are missing or duplicated stretches of DNA that have a "high impact" on autism. This means even though they rarely occur, they each raise the probability a person will have an autism spectrum disorder (ASD).

"Many of these gene variants may serve as valuable predictive markers," the study's corresponding author Dr. Hakon Hakonarson, director of the Center for Applied Genomics at The Children's Hospital of Philadelphia, said in a press release. "If so, they may become part of a clinical test that will help evaluate whether a child has an autism spectrum disorder."

According to the Centers for Disease Control and Prevention, one in 88 children in the U.S. has an ASD. ASDs are a term for different kinds of developmental disorders that cause social, communication and behavioral problems. Individuals with an ASD process information in their brain in a different way than the general population. There are three types of ASDs: autistic disorder, Asperger syndrome -- which will be dropped from the American Psychiatric Association manual in 2013 -- and pervasive developmental disorder - not otherwise specified. Each of these types can be mild or severe.

For the study, researchers looked at the DNA of 55 subjects from Utah families who had multiple members diagnosed with an ASD. They found 153 CNVs potentially linked to autism. They then looked for the 153 CNVs and another 185 CNVs previously associated with autism in a larger sample of 3,000 ASD subjects and 6,000 control subjects from the Children's Hospital of Philadelphia.

They found individuals that had one of 15 specific CNVs in the Utah family studies and 9 other CNVs that had been in a custom-designed DNA array made from the family data had at least twice the chance of having an ASD compared to the control group. Individuals with one of 31 out of 185 CNVs that had previously reported to be linked to autism also showed this twice-as-likely chance.

"These high-impact variants could be most useful in advising parents who already have one child with an ASD," Hakonarson said. "If a second child has delays in reaching developmental milestones, testing for these CNVs could help predict whether that child is also likely to develop an ASD." He added that the newly identified variants would need to be added to the existing commercially available diagnostic array in current use."

Researchers hope that they can use this data to help detect individuals at risk of an ASD.

"Oftentimes findings like this get published in academic journals, but they don't get translated into clinical use," author Chuck Hensel, senior manager of research at the genetic diagnostics company Lineagen, told TIME. "Our goal is to try to get these markers into the clinic."

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