Scientists at the University of California, Los Angeles (UCLA), have discovered a variant of a gene called CACNA1G that may increase a child's risk of developing autism, particularly in boys.

The journal Molecular Psychiatry published the findings in its May 19 advance online edition.

Classic autism strikes boys four times more often than girls. When including the entire spectrum of autism disorders, such as the milder Asperger syndrome, boys are diagnosed 10 times more often than girls.

"We found that a common form of the gene CACNA1G occurs more frequently in the DNA of families that have two or more sons affected by autism, but no affected daughters," Stanley Nelson, professor of human genetics at UCLA, said. "Our study may explain why boys are more susceptible to the disorder than girls."

Nelson and his colleagues zeroed in on a region of Chromosome 17 that previous studies have tied to autism. The research team scoured the DNA of 1,046 members of families with at least two sons affected by autism for common gene variants.

The researchers traced the genetic markers to CACNA1G, which helps move calcium between the cells. They discovered that the gene has a common variant that appears in the DNA of nearly 40 percent of the population.

"This alternate form of CACNA1G consistently increased the correlation to autism spectrum disorder, suggesting that inheriting the gene may heighten a child's risk of developing autism," Nelson said.

How the gene contributes to higher autism risk remains unclear, but Nelson emphasized that it cannot be considered a risk factor on its own.

"This variant is a single piece of the puzzle," he said, "We need a larger sample size to identify all of the genes involved in autism and to solve the whole puzzle of this disease."

Autism is a complex brain disorder that strikes in early childhood. The condition disrupts a child's ability to communicate and develop social relationships and is often accompanied by acute behavioral challenges.

(Xinhua News Agency May 20, 2009)