For both the living and the dead, BCL-2 and RORA were decreased in samples from autistic persons.

Tellingly, these genes are associated with processes that appear to play a role in autism. BCL-2 is a gene believed to stop cell death in the brain. Earlier studies have shown it is 34 to 51 percent less expressed in autistic male brains than in control subjects. RORA regulates the body's circadian rhythms; it also controls muscle tone and shields brain cells from the harmful effects of inflammation and oxidative stress. Importantly, it's also involved in the development of the cerebellum, a part of the brain known to be affected in autism.

Although RORA has never before been implicated in ASD, Hu says a naturally mutated mouse studied for its lack of coordination of muscle movement, which suffers from RORA deficiencies, shows autistic-like behaviors, such as reduced maze exploration and repetitive movements.

But these two genes might just be the tip of the iceberg. In another study also published by Hu and her team last week, in Genome Medicine, they found widespread differences in microRNA in ASD subjects when compared with controls. MicroRNA are snippets of RNA that turn off RNA molecules, limiting their expression. Of the 43 microRNA changes found in ASD subjects, 16 were brain-related. Others were linked with muscle disorders and gastrointestinal disturbances, a controversial and not universally accepted symptom of autism.

CAUSE UNKNOWN

Hu, whose 22-year-old son was diagnosed with an ASD, admits they're not sure what makes the gene expression go awry.

"No one really understands, or knows, what the environmental factors are that might predispose to autism; that's the bottom-line, that we don't know enough," says Hu. "There's no substitute for knowledge in terms of saying one thing or another. The fact is, we just don't know enough about genes, we don't know enough about epigenetic mechanisms."

Her team is now planning future studies to see what environmental or biological risks might predispose vulnerability to the disorder.

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