Battle of the sexes: when the female embryo takes control

2017

Challenge

The consensus of sexual differentiation, which has been held for over half a century, contends that the female reproductive system forms passively by default, whereas the male reproductive system arises as a result of the active action of testicular hormones.

Advance

IRP researchers led by Humphrey Hung-Chang Yao, Ph.D., challenged the female-by-default theory with a series of experiments in genetically female mouse embryos that lacked a protein called COUP-TFII, which regulates numerous genes important for development. The team discovered that female embryos actively promote the elimination of the male reproductive tract through the action of COUP-TFII.

Impact

The findings alter the long-standing view that an embryo will automatically become female unless male hormones called androgens in the embryo make it male. This study also fills a void in our understanding of the mechanism of sexual differentiation and provides a unique animal model for investigating disorders of sex development in humans.

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