Researchers link gene to some cases of autism

If a child has less or more than two copies of the gene, normal brain function is waylaid.

MCCLATCHY NEWSPAPERS

NEW YORK — A key gene involved with how brain cells “talk to each other” may be disrupted in some people with autism spectrum disorders, according to medical investigators who discovered the DNA flaw in a group of Long Island children.

Dr. Eli Hatchwell, an associate professor of pathology at Stony Brook University Medical Center, has found that mutations in a gene dubbed contactin 4 prevent it from properly performing its job: facilitating myriad connections within the brain in the complex network of cell-to-cell communication.

Two copies of the gene is considered normal, Hatchwell said Wednesday, but when a child has three copies or only one, normal brain function is waylaid by altered activity of contactin 4. He estimates that up to 2 percent of autism cases may be directly related to malfunctions in this gene.

“What we know about this gene is that it is involved with the development of axons,” Hatchwell said of the nerve cells needed in relaying messages between neurons. Neurons are the primary nerve cells that carry out all neurological functions.

“Axons help neurons talk to each other,” Hatchwell said, adding that his investigations are still relatively preliminary and that a lot more work is needed to better understand the gene and its impact on axons. He and his colleagues say the gene is located on chromosome 3. Forty-six chromosomes reside in the core, the nucleus, of cells that make up the human body.

“It is plausible that autism is a very complex condition,” involving numerous different genes, said Dr. Peter K. Gregersen, director of the Robert Boas Center for Genomics and Human Genetics in Manhasset. He was not connected with the contactin 4 research.

He cited last year’s genetic work by Michael Wigler of Cold Spring Harbor Laboratory as marking a milestone in understanding the genetics of autism. Wigler suggested that spontaneous mutations not passed on by parents can lead to autism. Gregersen said Hatchwell’s study adds yet another dimension.

The latest gene discovery involved testing 92 patients with autism from 81 families who are seen at the Cody Center for Autism and Developmental Disabilities at Stony Brook University.

Genetic material from these patients was compared with the DNA from 560 people without autism. Alterations in contactin 4 appeared to be inherited from fathers without an autism history.

When mapping the DNA, Hatchwell and colleagues found that patients with autism had deletions or duplications that disrupted the activity of contactin 4.

Hatchwell underscored that flaws involving contactin 4 are not the sole explanation of autism. There are likely to be many others for the spectrum of disorders estimated to affect 1 in every 150 children in the United States, according to the Centers for Disease Control and Prevention. People with autism can suffer marked social and developmental delays; some are mentally disabled.

“We’re getting much closer to understanding the molecular basis of autism,” said Geri Dawson, chief science officer for Autism Speaks, a national advocacy organization. She added that diagnostics will likely be the outcome of all the DNA research.

Hatchwell has cofounded Population Diagnostics in Melville with James Chinitz, its chief executive, to develop screenings for autism and other conditions, such as Alzheimer’s, Parkinson’s and diabetes.