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WASHINGTON — Scientists have long theorized that about 15 different genes play a role in who is born with the severe brain disorder autism – and now they’ve finally found one of those genes. 

A study of 57 autism patients found that 40 percent carry a mutated version of the HOXA1 gene, which plays a crucial role in early brain development, University of Rochester scientists reported Monday. 

Children need to inherit just one copy of the mutated gene from one parent to have autism. In fact, scientists found only one patient, a very severe case, who inherited a copy of the bad gene from both parents, suggesting that when that happens the fetus usually dies, said lead researcher Patricia Rodier, who heads the university’s National Institutes of Health-funded autism research center. 

The NIH called the finding a significant step in understanding what predisposes people to developing autism. 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 the gene discovery, in the December issue of the journal Teratology, supports. 

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 said. 

HOXA1 is one of a family of genes vital to early embryo development because genes in the group turn on or off other genes. HOXA1’s specific role is in brain development.  

Mice who lack this gene have brainstem damage, malformed ears and other classic signs of autism – one reason Rodier’s research team decided to check the gene’s role in people. 

It’s 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. 

On the Net: 

NIH autism site: http://www.nichd.nih.gov/autism 

Teratology Society site with link to study abstract: http://www.teratology.org