SEVERITY OF AUTISM 'MAY DEPEND ON VERSION OF BRAIN GENE INHERITED'
Wednesday, October 22, 2003 (15:27:00)

Posted by sylvia

New Scientist, September 5, 2003

Whether boys with autism suffer a severe form or just a mild version might depend on which version of a brain gene they inherit, according to a new study. And it is possible that the same gene variants influence the language and social skills of people generally.

Studies on twins and families have shown that heredity plays a big part in autism, but there seem to be many genes involved, and pinning down the ones responsible for autism is proving difficult. Instead, Dr Ira Cohen, a psychologist at NYS Institute for Basic Research in New York, decided to look for gene variants that affect the severity of the condition.

Some people with autism have higher levels of the neurotransmitter, serotonin, in their blood, but no genes involved in serotonin synthesis have been directly linked to autism. So Dr Cohen's team looked at the gene coding for monoamine oxidase A (MOAO), an enzyme that inactivates serotonin.

A variation in the length of the control region at the start of the MAOA gene determines how much of the enzyme is produced. Men have only one copy of the gene, since it is found on the X chromosome, and approximately a third of them have the form that results in lower MAOA production.

The team tested 41 autistic boys to see which variant of the MAOA gene they had. They found a clear link with the children's language and social skills. "Boys with less enzyme are not doing as well, not keeping up with their peers," says Dr Cohen. "Whereas boys with the high- activity form show better progress in language and other skills."

One previous study failed to find a link between autism and the MAOA gene, but that study looked only at whether one of the gene variants triggered autism.

Dr Cohen's finding might make it possible to identify boys most likely to develop severe autism earlier on. But, Dr Cohen says, a larger study is needed to check the result.

Although the team looked at only autistic children, it is possible that the gene affects everyone's language and social skills, says Dr Tom Wassink, a psychiatrist at the University of Iowa. "Either way, it's interesting."