Discovery of common genetic risk factors for autism spectrum disorders

Researchers have made an important step forward in understanding the complex genetic structure of autism spectrum disorders.

A researcher collaboration, including geneticists from the University of Pennsylvania School of Medicine and The Children's Hospital of Philadelphia (CHOP), have detected variations along a genetic pathway that is responsible for neurological development, learning and memory, which appears to play a significant role in the genetic risk of autism. Their findings will be published online in the journal Nature on April 28.

Evidence suggests there is a strong genetic component increasing the likelihood of an autism diagnosis, estimated to impact 1 in 150 children in the United States. The study findings suggest that a particular genetic variation, found on a cluster between CDH10 and CDH9, is commonly found in children with autism, according to co-senior author Gerard Schellenberg, PhD, professor of pathology and laboratory medicine at the University of Pennsylvania School of Medicine.

"We studied more than 10, 000 children – of whom more than 4, 500 had been diagnosed with an autism spectrum disorder – and found a common genetic variation that increases the risk of a child developing autism, along with a rarer genetic change that contributes to some cases of autism," Schellenberg said. "This work yields important clues on what goes awry during development in children with autism and will help us focus on what is the cause of autism at a molecular level."

"It is very compelling to find evidence that mutations in genes involved in brain interconnections increase a child's risk of autism, because other autism researchers have made intriguing suggestions that autism arises from abnormal connections among brain cells during early development," said study leader Hakon Hakonarson, MD, PhD, director of the Center for Applied Genomics at The Children's Hospital of Philadelphia and associate professor of Pediatrics at the University of Pennsylvania School of Medicine.

In a second study, researchers found deleted or duplicated genes along two major central nervous system gene networks in children with autism spectrum disorders. The changes were on the ubiquitin pathway, which is responsible for regulating synaptic operations and nervous system development. One ubiquitin-related gene studied, UBE3A, was previously thought to be connected to autism, while another, PARK2, was previously found to mutate and lead to juvenile Parkinson's disease. Future research will test the effects of the missing or extra genetic copies.