Oogenesis: transcriptional regulators and mouse models.

Oocyte differentiation into a totipotent cell requires initial germ cell cyst breakdown to form primordial follicles, recruitment of primordial follicles for development into primary follicles and remarkable growth of the ovarian follicle which culminates in ovulation. During oogenesis, the oocyte undergoes dynamic alterations in gene expression which are regulated by a set of well-coordinated transcription factors active in the germ line and soma. A number of germ cell specific as well as somatic expressed transcriptional regulators are critical in ovarian formation and folliculogenesis. These transcriptional regulators include: Foxo3, Foxl2, Figla, Lhx8, Nobox, Sohlh1 and Sohlh2. A subset of these transcriptional regulators is mutated in women with ovarian insufficiency and infertility. Studies on transcriptional regulators preferentially expressed in the ovary are important to develop a better understanding of the mechanisms of activation and survival of ovarian follicles, as well as an understanding of ovary specific pathways that can be modulated in the future to regulate fertility and protect against external insults such as chemotherapy.