Forkhead transcription factors in ovarian function

Since the discovery of the conserved forkhead (Fkh) DNA binding domain more than 20 years ago, members of the Fkh or forkhead box (FOX) family of transcription factors have been shown to act as important regulators of numerous developmental and homeostatic processes. The human genome contains 44 Fkh genes, several of which have recently been reported to be essential for female fertility. In this review, we highlight the roles of specific FOX proteins in ovarian folliculogenesis and present our current understanding of their molecular function. In particular, we describe what we have learned from loss-of-function studies using mouse models as well as human genetics and illustrate how different stages of folliculogenesis, both in oocytes and in somatic granulosa and theca cells, are regulated by FOXC1, FOXL2, and FOXO subfamily members.