Oct. 7 (HealthDay News) -- New genes and genomic regions that might be associated with autism have been identified by an international research team.

The researchers identified a single-letter change on chromosome 5 near a gene called semaphorin 5A, which is believed to help guide the growth of neurons and their long progressions, called axons. The activity of this gene appears to be reduced in the brains of people with autism.

The scientists also found a possible link between autism and parts of chromosomes 6 and 20.

For the study, the researchers analyzed DNA from people with autism, their family members and unrelated people. The findings are in the Oct. 8 issue of Nature.

"These discoveries are an important step forward, but just one of many that are needed to fully dissect the complex genetics of this disorder," co-senior author Dr. Mark Daly, a senior associate member of the Broad Institute of Harvard and MIT and an associate professor at the Center for Human Genetic Research at Massachusetts General Hospital, said in a Broad Institute news release.

"The genomic regions we've identified help shed additional light on the biology of autism and point to areas that should be prioritized for further study," he said.

Though the study identifies some new genes and genomic regions that might be associated with autism, the findings are just one piece of a large and mostly unfinished puzzle, the researchers said. A better understanding of the link between autism and genetics could be achieved, they said, through future studies with larger numbers of people and improved genomic technologies.

SOURCE: Broad Institute, news release, Oct. 7, 2009