Gene Mutations Linked to Autism

In one study, published in the journal Molecular Psychiatry, scientists discovered that a mutation, or variant, of the CACNA1G gene, located on chromosome 17, was consistently associated with autism in boys. The rate of autism is four times higher among boys than girls. The gene helps move calcium between cells, and its mutation can be found in some 40 percent of Americans. As with each of the newly discovered gene variants, having it doesn’t mean a person has or will develop autism, just that he has a tendency toward it, and may only develop the disorder if other genetic and environmental factors are present, too.

The researchers analyzed the DNA of 1,046 members of families that had at least two sons with autism.

“We found 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,” said Stanley Nelson, a professor of human genetics at the David Geffen School of Medicine at the University of California at Los Angeles. “Our study may explain why boys are more susceptible to the disorder than girls.”
   
Two other studies appeared in the journal Nature, both led by Hakon Hakonarson, director of genomics research at the Children’s Hospital of Philadelphia. Both were genome-wide association studies, in which the scientists looked at the full range of human genes, comparing those of autistic children with normal children’s to find differences.
   
The researchers found that 65 percent of children with autism spectrum disorder, a group of progressively worse autism-like conditions that includes autism, had an autism risk mutation, and that 15 percent of autism diagnoses could be accounted for using just these risk markers.

Moreover, the research team discovered that the mutant genes – CDH9 and CDH10, on a region of chromosome 5 – coded for proteins crucial to intercellular communication. This lent credence to the theory that autism is at least partially caused by problems with brain-cell communication in early childhood development.

The study results don’t purport to suggest a specific cause or treatments, said Thomas Insel, director of the National Institutes of Health’s National Institute of Mental Health, who didn’t participate in any of the studies. “If you think about autism as a jigsaw puzzle with 500 pieces, each of these findings is an ‘edge’ piece.” But many edge pieces are needed to fill out the picture, he said.
   
“It would be a mistake for people to read this and think this is only about genetics,” Insel said. “Almost everybody agrees that autism is a collection of different disorders. Some of them may be heavily genetic. But I think most experts would say the bulk of autism is the result of both genetic and environmental effects that are interacting in some way that we have yet to fully describe.”