Intercellular cyclic nucleotide dynamics mediate oocyte meiosis in mammalian preovulatory follicles

The cell cycle of the mammalian oocyte arrests in prophase around the time of birth and remains in meiotic arrest as it grows interdependently with increasing layers of surrounding somatic cells as a structure called an ovarian follicle. Within preovulatory follicles, gap junction communication between somatic cells and the oocyte allow cyclic nucleotides to maintain equilibrium concentrations that prevent premature meiotic resumption. Intercellular communication is also required for the mid-cycle surge in luteinizing hormone to alter cyclic nucleotide dynamics and cause the oocyte cell cycle to resume. In this review, the increasingly well-understood mechanisms by which meiotic arrest and meiotic resumption occur will be summarized, along with recent developments made possible by an improved cyclic nucleotide sensor and imaging techniques. These studies have uncovered new aspects of this process and helped clarify the required role of epidermal growth factor receptor signaling in meiotic resumption. Growing evidence that the cyclic nucleotide-associated participants in oocyte cell cycle regulation, first described in rodents, appear to be universal across mammals will also be summarized. This understanding has fostered new approaches to assisted reproductive technologies (ARTs) in domesticated animals and humans.