U.S. researchers have found disruptions in a gene, called contactin 4, stop it from working properly and appear to stop the brain from making proper networks, media reported Wednesday.

These disruptions, in which the child has either three copies of the gene or just one copy when two copies is normal, could account for up to 2.5 percent of autism cases, said Dr. Eli Hatchwell of Stony Brook University Medical Center in New York.

"That is a significant number," said Hatchwell."Generally the mistake that people make is they are looking for one unifying cause for autism, and there is no such thing and there never will be."

He said his finding adds to the list of potential tests for autism, and perhaps treatments for a range of conditions known as autism spectrum disorders.

Contactin 4 is involved in the development of axons, which are the long strings that connect one neuron to another. Otherdisruptions of this gene are known to cause developmental delay and mental retardation.

Contactin 4 are all inherited from fathers without a history of autism, which can cause severe social and developmental delays and even mental retardation.

This may seem like a small number but millions of people have some type of autism, Hatchwell noted. The U.S. Centers for Disease Control and Prevention estimates that one in every 150 children has autism or a related disorder such as Asperger's syndrome, which is marked by often mild social awkwardness.

(Agencies via Xinhua News Agency March 19, 2008)