Fig. 4

Schematic diagram of the mechanisms by which meiosis-related genes regulate oocyte MI arrest and resumption. Upregulated genes are shown in red, and downregulated genes are shown in black. (A) Maintenance of oocyte arrest at prophase I requires high cAMP levels. CGCs produce NPPC, and the presence of NPR2 in MGCs stimulates the production of cGMP, which enters oocytes through Cx37 in GJs and prevents PDE3A from hydrolyzing cAMP. cAMP activates PKA, leading to the inactivation of MPF and maintenance of MI arrest. (B) A sharp increase in LH secretion inhibits AR and ER to reduce the transcription and production of NPPC and increases EGF expression to activate EGFR signaling and increase calcium levels in CGCs to further inactivate NPR2. LH also causes follicular GJs to shut down, preventing cGMP from entering oocytes. Low cAMP and PKA levels in turn increase MPF levels, thereby promoting meiotic resumption