Scientists at Baylor College of Medicine and the Duncan Neurological Research Institute have identified genetic features that may help explain why autism is diagnosed approximately four times more often in men than in women. The study found that small changes in regulatory regions of the MECP2 gene on the X chromosome may increase the likelihood of developing the disorder. The findings were published in the American Journal of Human Genetics (AJHG).
The researchers studied DNA regions that regulate the activity of MECP2. This gene plays an important role in brain function: abnormally low or high levels of its activity can lead to neurodevelopmental disorders.
The scientists hypothesized that women may be partially protected against certain genetic changes because they have two X chromosomes, whereas men have only one. To test this hypothesis, the team examined regulatory regions of the gene and analyzed genetic variants in people with autism.
The researchers identified two regulatory regions in which the detected variants affected gene activity. One variant reduced MECP2 expression by approximately 30% in human neurons. In mouse experiments, similar changes were associated with differences in social behavior, hyperactivity, and anxiety. The person in whom this variant was identified had been diagnosed with autism and attention-deficit/hyperactivity disorder (ADHD).
The authors believe the findings help explain some of the differences in autism diagnosis rates between men and women. However, the identified variants are likely to account for only a small proportion of cases. The researchers plan to investigate similar genetic mechanisms in other X-chromosome genes involved in neurodevelopment.
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