FSH Modulates PKAI and GPR3 Activities in Mouse Oocyte of COC in a Gap Junctional Communication (GJC)-Dependent Manner to Initiate Meiotic Resumption

Abstract

Many studies have shown that cyclic adenosine-5′-monophosphate (cAMP)-dependent protein kinase A (PKA) and G-protein-coupled receptor 3 (GPR3) are crucial for controlling meiotic arrest in oocytes. However, it is unclear how gonadotropins modulate these factors to regulate oocyte maturation, especially by gap junctional communication (GJC). Using an in vitro meiosis-arrested mouse cumulus-oocyte complex (COC) culture model, we showed that there is a close relationship between follicle-stimulating hormone (FSH) and the PKA type I (PKAI) and GPR3. The effect of FSH on oocyte maturation was biphasic, initially inhibitory and then stimulatory. During FSH-induced maturation, rapid cAMP surges were observed in both cumulus cells and oocyte. Most GJC between cumulus cells and oocyte ceased immediately after FSH stimulation and recommenced after the cAMP surge. FSH-induced maturation was blocked by PKAI activator 8-AHA-cAMP. Levels of PKAI regulatory subunits and GPR3 decreased and increased, respectively, after FSH stimulation. In the presence of the GJC inhibitor carbenoxolone (CBX), FSH failed to induce the meiotic resumption and the changes in PKAI, GPR3 and cAMP surge in oocyte were no longer detected. Furthermore, GPR3 was upregulated by high cAMP levels, but not by PKAI activation. When applied after FSH stimulation, the specific phosphodiesterase 3A (PDE3A) inhibitor cilostamide immediately blocked meiotic induction, regardless of when it was administered. PKAI activation inhibited mitogen-activated protein kinase (MAPK) phosphorylation in the oocytes of COCs, which participated in the initiation of FSH-induced meiotic maturation in vitro. Just before FSH-induced meiotic maturation, cAMP, PKAI, and GPR3 returned to basal levels, and PDE3A activity and MAPK phosphorylation increased markedly. These experiments show that FSH induces a transient increase in cAMP levels and regulates GJC to control PKAI and GPR3 activities, thereby creating an inhibitory phase. After PDE3A and MAPK activities increase, meiosis resumes.

Transient Arrest of Germinal Vesicle Breakdown Improved In Vitro Development Potential of Buffalo (Bubalus Bubalis) Oocytes

“…Considering the complexity of GVBD event with respect to its regulation by different kinases and pathways [Stricker, ], we employed two inhibitors viz. Ros [Okumura et al, ] and Cil [Li et al, ], and found their combination to be highly efficient in inhibiting GVBD as compared to individual inhibitors (Fig. ).…”

Bidirectional communication between cumulus cells and the oocyte: Old hands and new players?

“…radioisotopes and calcein, [10,11,16]; 2) transfer of molecules/and or probes blocked by gap-junction inhibitors (e.g. carbenoxolone [17,18]; and 3) injected probes into the oocyte passing to the coronal cells of the cumulus oophorus (e.g. FITC-dextran, lucifer yellow [18][19][20].…”

“…The major regulatory signalling role of gap junctions is the passage of cyclic nucleotides into the oocyte from the cumulus cells which play a critical role in the regulation of meiosis [17], and therefore are impacted by the events surrounding ovulation (reviewed by [21]). Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) play critical inter-related roles in firstly preventing spontaneous meiotic activation from the germinal vesicle stage (prophase 1) prior to the ovulatory signal and then enabling re-induction of meiosis following the ovulatory signal.…”

NPR2 is involved in FSH-mediated mouse oocyte meiotic resumption

“…However, the subsequent developmental competence of oocytes matured in vitro is compromised compared with that of oocytes matured in vivo [ 8 – 10 ]. Gonadotrophin orchestrates the acquisition of oocyte competence, both in vivo and in vitro; therefore, in vitro culture systems of media were often supplemented with gonadotrophins, such as follicle-stimulating hormone (FSH), to induce cumulus cell expansion, nuclear maturation and cytoplasmic maturation and to improve embryonic development in many animals including the mouse [ 11 – 13 ], pig [ 14 ], cow [ 15 ], horse [ 16 ] and dog [ 17 ]. The molecular mechanisms by which gonadotrophins induce oocyte meiotic resumption is partly mediated by increasing the production of cAMP [ 18 , 19 ] and subsequently activating mitogen-activated protein kinase 3/1 (MAPK3/1) in its surrounding cumulus granulosa cells [ 20 – 22 ].…”