Growth differentiation factor 9 regulates the expression of estrogen receptors via Smad2/3 signaling in goat cumulus cells.

Both oocyte secretory factors (OSFs) and estrogen are essential for the development and function of mammalian ovarian follicles, playing synergistic role in regulating oocyte growth. OSFs can significantly affect the biological processes regulated by estrogen in cumulus cells (CCs). It is a scientific question worth investigating whether oocyte secretory factors can influence the expression of estrogen receptors in CCs. In our study, we observed a significant increase in the mRNA and protein expressions of estrogen receptor ß (Esr2/ERß) and G-protein-coupled estrogen receptor (GPER) in cumulus cells of goat cumulus-oocyte complexes (COCs) cultured in vitro for 6 h. Furthermore, the addition of 10 ng/mL growth-differentiation factor 9 (GDF9) and 5 ng/mL bone morphogenetic protein 15 (BMP15) to the culture medium of goat COCs resulted in a significant increase in the expressions of ERß and GPER in cumulus cells. To explore the mechanism further, we performed micromanipulation to remove oocyte contents and co-cultured the oocytectomized complexes (OOXs) with denuded oocytes (DOs) or GDF9/BMP15. The expressions of ERß and GPER in the co-culture groups were significantly higher than those in the OOXs group, but there was no difference compared to the COCs group. Mechanistically, we found that SB431542 (inhibitor of GDF9 bioactivity), but not LDN193189 (inhibitor of BMP15 bioactivity), abolished the upregulation of ERß and GPER in cumulus cells and the activation of Smad2/3 signaling. In conclusion, our results demonstrate that the oocyte secretory factor GDF9 promotes the activation of Smad2/3 signaling in cumulus cells during goat COCs culture in vitro, and the phosphorylation of Smad2/3 induces the expression of estrogen receptors ERß and GPER in cumulus cells.

Strained Lattice Gold-Copper Alloy Nanoparticles for Efficient Carbon Dioxide Electroreduction.

Electrocatalytic conversion of carbon dioxide (CO2) into specific renewable fuels is an attractive way to mitigate the greenhouse effect and solve the energy crisis. AunCu100-n/C alloy nanoparticles (AunCu100-n/C NPs) with tunable compositions, a highly active crystal plane and a strained lattice were synthesized by the thermal solvent co-reduction method. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) results show that AunCu100-n/C catalysts display a subtle lattice strain and dominant (111) crystal plane, which can be adjusted by the alloy composition. Electrochemical results show that AunCu100-n/C alloy catalysts for CO2 reduction display high catalytic activity; in particular, the Faradaic efficiency of Au75Cu25/C is up to 92.6% for CO at -0.7 V (vs. the reversible hydrogen electrode), which is related to lattice shrinkage and the active facet. This research provides a new strategy with which to design strong and active nanoalloy catalysts with lattice mismatch and main active surfaces for CO2 reduction reaction.

G protein-coupled estrogen receptor signaling dependent epidermal growth-like factor expression is required for NPR2 inhibition and meiotic resumption in goat oocytes.

G protein-coupled estrogen receptor (GPER), which is different from traditional estrogen nuclear receptors (ERs), mediates the rapid transduction of nongenomic signals in cells, and works by regulating transcription and intracellular second messengers. Studies have shown that GPER may regulate oocyte maturation, but the relevant mechanism is not entirely clear. Here, goat cumulus-oocyte complexes (COCs) were used as a model to explore the regulation and mechanism of GPER on oocyte maturation. Our study showed that 17ß-estradiol (E2) significantly reduced cyclic guanosine monophosphate (cGMP) synthesis in COCs and accelerated the meiotic resumption of goat oocytes via GPER. Further investigation found that GPER mediated the downregulation of natriuretic peptide receptor 2 (NPR2) protein expression in goat cumulus cells by E2. In addition, we found that E2 significantly upregulated the mRNA levels of epidermal growth (EGF)-like factors in goat cumulus cells through GPER, and activated the downstream EGF receptor (EGFR) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathways. Both AG1478 (EGFR inhibitor) and U0126 (ERK1/2 inhibitor) abolished the inhibitory effect of E2 on the protein expression of NPR2. These results indicate that, through GPER, E2 upregulates the mRNA levels of EGF-like factors in goat cumulus cells and activates the downstream EGF signaling network to suppress the expression of NPR2 protein, which results in a decrease in cGMP synthesis and acceleration of meiotic resumption in goat oocytes.

Synergistic effect between LH and estrogen in the acceleration of cumulus expansion via GPR30 and EGFR pathways.

The estrogen membrane receptor GPR30 (also known as G-protein coupled receptor 30) has recently been shown to be involved in the regulation of oocyte maturation and cumulus expansion. However, whether GPR30 expression is regulated by gonadotropin stimulation and how it participates in the regulation of the maturation process is still not clear. In this study, we explored the mechanism underlying the synergy between luteinizing hormone and 17ß-estradiol (17ß-E2) to improve the epidermal growth factor (EGF) response in cumulus oocyte complexes (COCs) during oocyte maturation in mice. The expression and distribution of GPR30, EGFR, and EGF-like growth factors were examined by real-time quantitative PCR, western blot, and immunofluorescence staining. Lyso-Tracker Red labeling was performed to detect the lysosomal activity in follicle granular cells (FGCs). Cumulus expansion of COCs was evaluated after in vitro maturation for 16 h. We found that EGF-like growth factors transmit LH signals to increase GRP30 levels by inhibiting protein degradation in lysosomes. Meanwhile, 17ß-E2 stimulates the GPR30 signaling pathway to increase EGF receptor levels, enhancing the response ability of EGF signaling in COCs and thus promoting cumulus expansion. In conclusion, our study reveals the synergistic mechanism between LH and estrogen in the regulation of cumulus expansion during oocyte maturation process.

Mechanisms of Estradiol-induced EGF-like Factor Expression and Oocyte Maturation via G Protein-coupled Estrogen Receptor.

Estrogen is an important modulator of reproductive activity through nuclear receptors and G protein-coupled estrogen receptor (GPER). Here, we observed that both estradiol and the GPER-specific agonist G1 rapidly induced cyclic adenosine monophosphate (cAMP) production in cumulus cells, leading to transient stimulation of phosphorylated cAMP response element binding protein (CREB), which was conducive to the transcription of epidermal growth factor (EGF)-like factors, amphiregulin, epiregulin, and betacellulin. Inhibition of GPER by G15 significantly reduced estradiol-induced CREB phosphorylation and EGF-like factor gene expression. Consistently, the silencing of GPER expression in cultured cumulus cells abrogated the estradiol-induced CREB phosphorylation and EGF-like factor transcription. In addition, the increase in EGF-like factor expression in the cumulus cells is associated with EGF receptor (EFGR) tyrosine kinase phosphorylation and extracellular signal-regulated kinase 1/2 (ERK1/2) activation. Furthermore, we demonstrated that GPER-mediated phosphorylation of EGFR and ERK1/2 was involved in reduced gap junction communication, cumulus expansion, increased oocyte mitochondrial activity and first polar body extrusion. Overall, our study identified a novel function for estrogen in regulating EGFR activation via GPER in cumulus cells during oocyte maturation.

Effect of FSH on E2/GPR30-mediated mouse oocyte maturation in vitro.

Mammalian oocyte restores meiosis can be stimulated by follicle-stimulating hormone (FSH) under normal physiological conditions. G-protein coupled receptor 30 (GPR30), an non-classical estrogen membrane receptor, has been widely reported in teleost oocyte maturation. However, it remains unknown whether GPR30 involves the role of FSH in mammalian cumulus expansion and oocyte maturation. Here, we used mouse cumulus-oocyte complexes (COCs) as a model to investigate how FSH affects the in vitro maturation of mouse oocytes mediated by 17ß-estradiol (E2)/GPR30signaling. Our study reveals that FSH starts regulating mouse cumulus expansion precisely at 8h in in vitro culture. ELISA measurement of E2 levels in culture medium revealed that FSH activated aromatase to promote E2 production in vitro in cultured mouse COCs. Moreover, the results of real-time quantitative PCR indicated that FSH-induced in vitro maturation of mouse oocytes was regulated by the estrogen-signaling pathway mediated by GPR30; FSH treatment markedly increased the mRNA expression of HAS2, PTGS2, and GREM1 in COCs. Exploration of the underlying mechanism suggested that E2 produced by mouse COCs regulated the phosphorylation level of extracellular signal-regulated kinase 1/2 (ERK1/2) through GPR30 and thereby promoted mouse cumulus-cell expansion and oocyte maturation. In conclusion, our study reveals that FSH induced estrogen production in mouse COCs through aromatase, and that aromatase/GPR30/ERK1/2 signaling is involved in FSH-induced cumulus expansion.