[Oocyte-cumulus dialog]

Abstract

The dialog between oocyte and cumulus cells brings a major contribution for oocyte meiotic and developmental competence. On the one hand, the oocyte will modulate follicle growth through specific gene expression (Figalpha, GDF-9, BMP15) as well as its meiosis (GPR3 et PDE3A). Beyond its action on proliferation, oocyte will control in part the differentiation of cumulus cells with a particular involvement of GDF-9, BMP15 in this late maturation process. On the other hand, somatic cells are the main targets of gonadotropins and will modulate both oocyte growth and maturation. Gap-junctions between oocyte and cumulus cells have a major role in this interaction, since they allow the action of some oocyte specific genes (GDF9) but also the control of its own metabolism and calcium movements. While ovulation will involve gonadotropins action on somatic cells, EGF-like factors recruited at the cumulus level will participate in this process. Finally we may suspect that improving the knowledge on oocyte-cumulus dialog will contribute to better define oocyte competence, while bringing some clues for in vitro maturation.