While researchers have theorized about 15 different genes involved in autism, they now believe they have identified one that may predispose people to developing the disorder.
University of Rochester scientists report in the current issue of Teratology that 40 percent of 57 autism patients in a study they performed carried a mutated version of the HOXA1 gene, which plays a crucial role in early brain development.
Gene Involved in Early Development
“These findings strongly suggest that a gene controlling early brain formation may underlie the development of autism in a large number of cases, “ says Duane Alexander, director of the National Institute of Child Health and Human Development in the National Institutes of Health.
To develop autism, children need to inherit just one copy of a mutated gene from one parent. Only one person in the study carried two copies of the variant gene. Such an event is rare, because two copies would probably interfere with survival, explains lead researcher Patricia Rodier, who heads the university’s autism research center, funded by the National Institutes of Health.
More than 400,000 Americans have the brain disorder, characterized by profound social withdrawal, repetitive behavior and inability to communicate. Research suggests it’s caused when something goes wrong during critical fetal brain development — a theory supported by the gene discovery.
Maternal Inheritance May Play Role
Why don’t parents who harbor the defective gene have autism themselves? Some do have very subtle symptoms, suggesting that something else, perhaps some other gene, keeps the autism-related gene in check, Rodier says.
The gene also expresses itself more readily when the person inherits from the mother than from the father, the researchers found. This finding agrees with other studies of autism in families: Inheritance from the mother seems to play a strong role in who develops the disorder.
Rodier said her co-workers decided to investigate the HOXA 1 gene after reviewing the pattern of birth defects resulting from prenatal exposure to thalidomide. Children born to mothers who took the drug during pregnancy have sometimes been born with autism. They also had misshapen ears and abnormalities of the nerves of the head and face.
Thalidomide Damages Gave Clues
Studies revealed that damage to the fetus from thalidomide occurred between the 20th and 24th day after conception, the time when the brain region that controls the muscles, eyes, face, tongue, jaw and throat is developing.
Mice engineered to lack the HOXA 1 gene show similar patterns of brain and ear abnormalities so researchers tested autism patients for mutations in the corresponding human gene.
HOXA 1 is not the kind of gene that could ever be fixed with gene therapy. But the discovery may help doctors unravel just how the brain changes when HOXA1 is abnormal, Rodier said.
“If you figure out the brain changes, you’re on your way, we hope, to finding better treatments,” she said.
Other research needs to be done to reproduce the findings.
ABCNEWS.com’s Robin Eisner and The Associated Press contributed to this report.