(Great Neck, N.Y. - May 26, 2009) — Stanley F. Nelson, M.D., whose early research was supported by a NARSAD Young Investigator Award in 1994, and his team at the University of California, Los Angeles, have discovered a variant of a gene called CACNA1G that may increase children's risk of developing autism, particularly boys. The finding was reported in the journal Molecular Psychiatry in its May 19 online edition.
Classic autism strikes four times as many boys as girls. When including the entire spectrum of autism disorders, such as the milder Asperger syndrome, boys are 10 times more likely to be diagnosed.
"This is a strong finding," said Dr. Nelson, who is professor of human genetics at the David Geffen School of Medicine at UCLA and the study's principal investigator. "No one has scrutinized the role that CACNA1G plays in autism.”
The team discovered that a common form of the gene occurs more frequently in the DNA of families that have two or more sons affected by autism but no affected daughters. "Our study may explain why boys are more susceptible to the disorder than girls," Dr. Nelson said.
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. (A variant is a gene that has undergone subtle changes from the normal DNA yet is shared by a significant portion of the population). They scanned thousands of variants across all genes in the suspicious region of the chromosome to pluck out the most common forms.
"We wanted to identify what was happening in this region of chromosome 17 that boosts autism risk," Nelson said. "When the same genetic markers kept cropping up in a single region of the DNA, we knew we had uncovered a big clue."
The researchers traced the genetic markers to CACNA1G, which helps move calcium between 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 disorders, 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."
The UCLA team's next step will be to sequence the gene in people who possess the altered variant in order to identify the exact change that increases autism risk. These subtle variations offer potential markers for the real mutation causing greater susceptibility to the disease.
(The article was adapted with permission from UCLA).