Fig. 7: Model of the signaling pathways involved in somatic cells control of oocyte meiotic maturation and developmental competence.

In preovulatory follicles, LH stimulates the expression of EGF-like growth factors in mural granulosa cells to activate EGFR in cumulus cells. EGFR signaling causes SphK activation to produce S1P. S1P elevates the calcium levels of cumulus cells via PLN, S1P receptors, and/or undefined signaling(s) to decrease NPR2 activity and cGMP levels, resulting in oocyte meiotic maturation. In addition, S1P secreted from cumulus cells activates the Akt/mTOR cascade reaction in oocytes, and promotes oocyte spindle-related mRNA translation and developmental competence.