Commentary In the Ovary, the Rhox Library Is the Lender and Some Genes Are the Borrowers

The genes of the Rhox homeobox gene cluster of the Hox family of nuclear transcription factors are expressed exclusive-ly in reproductive tissues and have been recognized to play important roles in reproductive processes [1]. In the male, the complexity of regulation by this family and its implications for maturation of spermatozoa in the epididymis have been demonstrated [1] and commented on [2]. The search for master regulators of folliculogenesis has taken an important and complementary turn, as reported in this issue of the Biology of Reproduction, by the McLean laboratory [3]. The work is derived from the hypothesis that, as in the male, the Rhox homeobox gene cluster may serve as master regulators of folliculogenesis. In particular, the Rhox family is one ‘‘library’’ where granulosa cell genes can ‘‘borrow’ ’ transcription factors for induction and progesterone can serve as the library card