Regulatory roles of transforming growth factor beta family members in folliculogenesis

Bidirectional signaling between the oocyte and surrounding somatic cells is absolutely essential for successful germ cell development in mammals. Oocytes secrete proteins that are necessary for granulosa cells growth and differentiation, whilst granulosa cells regulate oocyte development and integrate ovarian function with the rest of the body by orchestrating gonadal steroidogenesis. The importance of communication between the oocyte and granulosa cells is highlighted by genetic deletion of members of the transforming growth factor beta (TGFβ) family and their downstream signaling components. Such knockout models have uncovered an interesting spectrum of reproductive phenotypes that have greatly advanced our knowledge of ovarian function and dysfunction. The current review focuses on some of the more recent transgenic mouse models that elucidate the intraovarian TGFβ signaling vital for oocyte and granulosa cell development.