Why males have a higher incidence of autism than females

February 17, 2011

Scientists have found that male and female sex hormones regulate expression of

an important gene in neuronal cell culture through a mechanism that could

explain not only higher levels of testosterone observed in some individuals with

autism, but also why males have a higher incidence of autism than females.

The gene, RORA, encodes a protein that works as a " master switch " for gene

expression, and is critical in the development of the cerebellum as well as in

many other processes that are impaired in autism.

Washington University researcher Dr. Hu's previous study found

that RORA was decreased in the autistic brain. In this study, the research group

demonstrates that aromatase, a protein, which is regulated by RORA, is also

reduced in autistic brains. This is significant because aromatase converts

testosterone to estrogen.

Thus, a decrease in aromatase is expected to lead in part to build up of male

hormones, which, in turn, further decrease RORA expression, as demonstrated in

this study using a neuronal cell model.

On the other hand, female hormones were found to increase RORA in the neuronal

cells. The researchers believe that females may be more protected against RORA

deficiency not only because of the positive effect of estrogen on RORA

expression, but also because estrogen receptors, which regulate some of the same

genes as RORA, can help make up for the deficiency in RORA.

" It is well known that males have a higher tendency for autism than females;

however, this new research may, for the first time, provide a molecular

explanation for why and how this happens. This is just the tip of the iceberg in

terms of understanding some of the biology underlying autism, and we will

continue our work to discover new ways to understand and, hopefully, to someday

combat this neurodevelopmental disorder, " said Dr. Hu.

In her research published in 2009, Dr. Hu and colleagues found that RORA

deficiencies were only apparent in the most severe cases of autism and were

observed in the brain tissues of both male and female subjects.

They further found that the deficiency in RORA was linked to a chemical

modification of the gene (called methylation) which effectively reduces the

level of RORA. (ANI)

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