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New Study to Explore Genetics of Autism

By Cheryl Simon Silver

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A $3 million grant from National Institute of Mental Health is supporting a new effort to try to identify the genetic factors that contribute to autism.

Aravinda Chakravarti of Johns Hopkins University School of Medicine in Baltimore is leading a team that will study the genes of people from 465 families, including 979 individuals with autism. The project includes researchers at Hopkins and the University of Chicago.

Experts estimate that autism occurs in one out of 500 children. While autism is known to run in families, no single gene has yet been linked to autism. One of the theories about the disease is that extra copies of genes or chromosomes may be involved.

“A credible hypothesis is that it’s not the gene sequence that matters, but how many copies of the sequence exist,” Chakravarti says. “All of us have two copies of every gene, but once in a while a gene is deleted, or a gene is added. People have looked for chromosomal changes in autism and while there are no consistent findings, there are hints.”

The researchers will employ digital technology for looking at chromosomes recently developed by Victor Velculescu of the Johns Hopkins Kimmel Cancer Center, who is a member of the project. They will compare the DNA of family members with and without autism, looking for extra copies of genes and also for genes that may be missing.

If the researchers find that extra copies of genes are present among many affected individuals, they will then try to determine whether this is a contributing factor in the disease.

Another goal is to identify genetic factors responsible for the broad range of symptoms in the disease. The severity of autism varies dramatically from one person to another with regard to the severity of social and communication deficits as well as other symptoms such as repetitive physical movements.

A number of researchers have suggested that environmental factors may be involved in spikes in autism incidence in California and parts of Britain. While Chakravarti believes that environmental factors may play a role in autism, he notes that there are an infinite number of potential environmental factors and it would be an impossible challenge to identify those that may interact with genes to trigger autism.

“Although the human genome is big,” he says, “it’s finite.”

The researchers are hopeful that what they learn about alterations in the numbers of copies of genes may prove useful in understanding other complex diseases.

“Psychiatric traits are the ultimate puzzle to solve,” Chakravarti says. “But I believe we have a very good chance of sorting this out.”

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