A newly identified genetic variant could account for up to 15 per cent of autism cases, say researchers who studied genes that are important in connecting brain cells.

In Wednesday's issue of the journal Nature, researchers say the variant is carried by about 65 per cent of people with autism — a neurological condition that interferes with communication and social skills. The disorder can range from mild to profound.

"Many of the genes we identified concentrate their effects in brain regions that develop abnormally in autistic children," said study leader Dr. Hakon Hakonarson, director of the the Center for Applied Genomics at The Children's Hospital of Philadelphia.

"Our current findings, when coupled with anatomical and imaging studies, may suggest that [autism spectrum disorders] are a problem of neuronal disconnection," he added in a release.

Previous genetic discoveries have found extremely rare instances of genetic variants that were missing or copied too many times in autism, and accounted for a small fraction of autism case.

Hakonarson's study looked at more than 2,500 people with autism and 7,000 healthy controls.

The variant was found between cadherin 10 and cadherin 9 — cell surface proteins that enable cells to adhere to each other. In the developing brain, the proteins allow neurons to migrate to the correct places to connect with other neurons.

Variation pinpointed

A second study confirmed that autism spectrum disorder is associated with a variation near cadherin 10 and cadherin 9. That study was led by Margaret Pericak-Vance, director of the Miami Institute for Human Genomics in Florida, and was published in Tuesday's online issue of the Annals of Human Genetics.

A third study by Hakonarson published in Nature pointed to a link between autism and excess ubiquitin, a protein involved in developing connections within the central nervous system.

"Detailed analysis of the genes and how they affect brain development is likely to yield better strategies for diagnosing and treating children with autism," said Dr. Raynard Kington, acting director of the U.S. National Institutes of Health, which funded the research.

Autism spectrum disorders affect about one in 150 children in Canada, according to Health Canada.