David Page

For every girl diagnosed with autism, four boys receive the same diagnosis. Even as overall diagnoses of autism have increased in recent years, largely due to broadening of diagnostic criteria, this 1:4 ratio has stayed the same. Scientists often call this the “female protective effect,” but the biological reason behind it has been unclear. Our lab has been studying the so-called “inactive” X chromosome, or Xi, for answers.

Females have two X chromosomes, while males have one X and one Y. For decades, scientists thought one of the female X chromosomes was mostly silent. But new research from our lab shows that Xi is far from inactive.

We’ve found that many genes on Xi act like master switches. They influence the activity of thousands of genes across the rest of the genome. This includes the autosomes, the 22 pairs of non-sex chromosomes that are the same in males and females. In females, this extra layer of control may provide protection against certain genetic risks, including those linked to autism. 

While the Y chromosome carries its own versions of some of these genes, they don’t work quite the same way. By studying these differences, we hope to learn more about why autism is more common in boys.