Genetics researchers have identified 25 additional copy number variations (CNVs) — missing or duplicated stretches of DNA — that occur in some patients with autism. According to the researchers, these are "high impact" CNVs: although individually rare, each has a strong effect in raising an individual's risk for autism.
"Many of these gene variants may serve as valuable predictive markers," said the study's corresponding author, Hakon Hakonarson, MD, PhD, director of the Center for Applied Genomics at The Children's Hospital of Philadelphia. "If so, they may become part of a clinical test that will help evaluate whether a child has an autism spectrum disorder."
The study, which was published recently in PLOS ONE, builds on and extends previous gene research by on autism spectrum disorders (ASDs). Estimated by the CDC to affect as many as one in 88 U.S. children, ASDs are known from family studies to be strongly influenced by genetics.
The researchers first analyzed DNA from 55 individuals from Utah families with multiple members diagnosed with ASDs. The team identified 153 CNVs as potentially specific to autism.
To investigate these CNVs in a broader ASD population, the study team custom-designed a DNA array with probes for those 153 CNVs, as well as for another 185 CNVs previously reported to be associated with autism. They then analyzed the actual prevalence of all the CNVs in a larger sample set of 3,000 ASD cases and 6,000 control subjects previously gathered in studies by The Children's Hospital of Philadelphia.
The researchers found that 15 of the CNVs found in the family studies, in addition to nine other CNVs found by their custom array, all had odds ratios greater than 2.0, meaning that subjects with those variants had at least two-fold increased risk of having an ASD, compared to controls. Another 31 CNVs previously reported to be associated with autism also had odds ratios above 2.0.
Further research may help establish whether the CNVs reported in the current study may be categorized by how they contribute to specific clinical subtypes of ASDs, Dr. Hakonarson said.