Progesterone receptors and ovulation.

The steroid hormone, progesterone, plays a critical role in the regulation of female ovulation. The physiological effects of progesterone are mediated by two nuclear receptor transcription factors, PR-A and PR-B, which are produced from a single gene and upon binding progesterone regulate the expression of specific gene networks in reproductive tissues. Both null mutation of the PR gene to delete both receptor proteins and selective disruption of the PR-A isoform lead to a failure of ovulation due to disabled follicular rupture in response to gonadotrophin stimulation. Recent studies have revealed that the LH stimulus that triggers ovulation is transduced by PRs residing in mural granulosa cells that induce expression of paracrine signals that interact with cumulus cells to control cumulus matrix function and expansion to facilitate follicular rupture.