Dynamic expression of Epac and Rap1 in mouse oocytes and preimplantation embryos

Cyclic adenosine monophosphate (cAMP) is an important secondary messenger that has long been recognized to control the initiation of meiosis through the activation of protein kinase A (PKA) in mammalian oocytes. However, PKA is not the only target for cAMP. Recent studies on cAMP-dependent and PKA-independent pathways suggest that Ras-related protein-1 (Rap1) is activated through its cAMP-responsive guanine exchange factors (cAMP-GEFs), which comprises the involvement of exchange proteins directly activated by cAMP (Epac) in various cellular processes. The aim of the present study was to investigate the possible implication of a cAMP/Epac/Rap1 pathway in mouse oocytes and embryos. Reverse transcription polymerase chain reaction and immunohistochemistry assays demonstrated the expression of Epac and Rap1 in oocytes and embryos at different stages. Immunofluorescene demonstrated that Epac and Rap1 had different dynamic subcellular localizations and expression patterns in oocytes and embryos at different stages. It was therefore indicated that Epac and Rap1 may have multiple and specific functions during oocyte maturation and embryonic development.