Researchers have discovered a genetic defect responsible for 1 percent of the various forms of autism, they reported Wednesday.

Identifying the genetic defect could offer another way to screen early for the disease, Moreover, doctors could help children with treatments that can reduce some effects for the developmental disorder, researchers said.

“If we can identify children at risk for autism very early, we have the chance to intervene early while the brain is still developing,” says Annette Estes of the University of Washington's Autism Center Research Program.

This discovery comes after researchers at the California Department of Public Health on Monday said that removing thimerosal from all recommended infants vaccines as a precautionary measure in March 2001 had no effect on reducing the number of children suffering from autism. They reported that autism rates in California have continued to climb, from 3 per 1,000 in 2003 to 4 per 1,000 in 2007. The only childhood vaccines that contain more than trace amounts of thimerosal are multiple-dose vials of some flu vaccines.

Researchers in Boston and Chicago independently identified a genetic variation in a region of the DNA called chromosome 16 that is associated with about 1 percent of all autism cases. They also said that the abnormality is often inherited.

The discovery is not new as David Miller, a researcher at Children’s Hospital in Boston and a co-author of one of the studies said that about 15 percent of autism cases have a known genetic cause.

Researchers at University of Chicago, who published their results in Human Molecular Genetics, said the loss of a small portion of chromosome 16 results in a corresponding loss of 25 genes. At least three of those genes are believed to influence behavior, making them prime candidates for autism research.

"The hope is that eventually, if we can find genes that lead to brain mechanisms, we can think about treatment," said Fred Volkmar, an autism expert and director of the child study center at the Yale University School of Medicine, who was not involved in either study.
 
The second study, made by researchers from a group of Boston hospitals and universalities known as the Autism Consortium, was published Wednesday in the online issue of the New England Journal of Medicine.

The researchers scanned DNA samples from more than 3,000 people, including 1,441 diagnosed with autism to identify the link to chromosome 16. They discovered 13 children who were missing snippets of DNA and 11 who had duplications. In all the cases, the children had autism or related problems, the researchers reported.

Miller said that his team plans further study of the region to identify exactly which of these genes is most closely linked to autism.

“We think that this chromosome 16 region may have some genes that are very important in brain development, and when changes happen in those genes, it may be the cause of many cases of autism. We have to figure out what is it about the combination of this chromosome 16 with other genetic factors, or other environmental factors,” he said.