Molecular control of oocyte meiotic arrest and resumption

Mammalian oocytes within Graafian follicles are arrested at prophase I by factors from surrounding follicle cells, and resume meiosis after an LH surge from the pituitary. The maintenance of meiotic arrest requires high levels of cAMP, resulting from G-protein-coupled receptor (GPR) 3 and/or GPR12 activation of adenylyl cyclase within the oocyte. Recent studies indicate that natriuretic peptide precursor C (NPPC), acting via its cognate receptor NPR2, increases cGMP levels in granulosa cells; the cGMP then diffuses into oocytes and inhibits phosphodiesterase 3A activity and cAMP hydrolysis. Meiotic resumption is induced by LH via the generation of epidermal growth factor (EGF)-like growth factors in mural granulosa cells that activate EGF receptors in cumulus cells. However, the exact mechanisms underlying the actions of these growth factors on oocyte maturation are unclear. Herein we summarise the regulatory functions of NPPC and NPR2 in maintaining oocyte meiotic arrest and discuss the possibility that LH could stimulate meiotic resumption by decreasing NPPC content and NPR2 activity.

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Mouse Oocytes Enable LH-Induced Maturation of the Cumulus-Oocyte Complex via Promoting EGF Receptor-Dependent Signaling

Molecular Endocrinology ◽

10.1210/me.2009-0497 ◽

2010 ◽

Vol 24 (6) ◽

pp. 1230-1239 ◽

Cited By ~ 73

Author(s):

You-Qiang Su ◽

Koji Sugiura ◽

Qinglei Li ◽

Karen Wigglesworth ◽

Martin M. Matzuk ◽

...

Keyword(s):

Growth Factors ◽

Granulosa Cells ◽

Egf Receptor ◽

Cumulus Cells ◽

Wild Type ◽

Paracrine Factors ◽

Cumulus Oocyte Complex ◽

Egfr Expression

Abstract LH triggers the maturation of the cumulus-oocyte complex (COC), which is followed by ovulation. These ovarian follicular responses to LH are mediated by epidermal growth factor (EGF)-like growth factors produced by granulosa cells and require the participation of oocyte-derived paracrine factors. However, it is not clear how oocytes coordinate with the EGF receptor (EGFR) signaling to achieve COC maturation. The aim of the present study was to test the hypothesis that oocytes promote the expression of EGFR by cumulus cells, thus enabling them to respond to the LH-induced EGF-like peptides. Egfr mRNA and protein expression were dramatically reduced in cumulus cells of mutant mice deficient in the production of the oocyte-derived paracrine factors growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15). Moreover, microsurgical removal of oocytes from wild-type COCs dramatically reduced expression of Egfr mRNA and protein, and these levels were restored by either coculture with oocytes or treatment with recombinant GDF9 or GDF9 plus recombinant BMP15. Blocking Sma- and Mad-related protein (SMAD)2/3 phosphorylation in vitro inhibited Egfr expression in wild-type COCs and in GDF9-treated wild-type cumulus cells, and conditional deletion of Smad2 and Smad3 genes in granulosa cells in vivo resulted in the reduction of Egfr mRNA in cumulus cells. These results indicate that oocytes promote expression of Egfr in cumulus cells, and a SMAD2/3-dependent pathway is involved in this process. At least two oocyte-derived growth factors, GDF9 and BMP15, are required for EGFR expression by cumulus cells.

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Stops and starts in mammalian oocytes: recent advances in understanding the regulation of meiotic arrest and oocyte maturation

Reproduction ◽

10.1530/rep.1.00793 ◽

2005 ◽

Vol 130 (6) ◽

pp. 791-799 ◽

Cited By ~ 274

Author(s):

Lisa M Mehlmann

Keyword(s):

G Protein ◽

Oocyte Maturation ◽

Cumulus Cells ◽

Follicle Cells ◽

Meiotic Maturation ◽

Meiotic Arrest ◽

Epidermal Growth ◽

High Level ◽

G Protein Coupled ◽

Stimulation Of

Mammalian oocytes grow and undergo meiosis within ovarian follicles. Oocytes are arrested at the first meiotic prophase, held in meiotic arrest by the surrounding follicle cells until a surge of LH from the pituitary stimulates the immature oocyte to resume meiosis. Meiotic arrest depends on a high level of cAMP within the oocyte. This cAMP is generated by the oocyte, through the stimulation of the GsG-protein by the G-protein-coupled receptor, GPR3. Stimulation of meiotic maturation by LH occurs via its action on the surrounding somatic cells rather than on the oocyte itself. LH induces the expression of epidermal growth factor-like proteins in the mural granulosa cells that act on the cumulus cells to trigger oocyte maturation. The signaling pathway between the cumulus cells and the oocyte, however, remains unknown. This review focuses on recent studies highlighting the importance of the oocyte in producing cAMP to maintain arrest, and discusses possible targets at the level of the oocyte on which LH could act to stimulate meiotic resumption.

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Cellular Heterogeneity of the Luteinizing Hormone Receptor and Its Significance for Cyclic GMP Signaling in Mouse Preovulatory Follicles

Endocrinology ◽

10.1210/endocr/bqaa074 ◽

2020 ◽

Vol 161 (7) ◽

Cited By ~ 3

Author(s):

Valentina Baena ◽

Corie M Owen ◽

Tracy F Uliasz ◽

Katie M Lowther ◽

Siu-Pok Yee ◽

...

Keyword(s):

Luteinizing Hormone ◽

Granulosa Cells ◽

Hormone Receptor ◽

Cellular Localization ◽

Cumulus Cells ◽

Luteinizing Hormone Receptor ◽

Cellular Heterogeneity ◽

Signaling Proteins ◽

Meiotic Arrest ◽

Preovulatory Follicles

Abstract Meiotic arrest and resumption in mammalian oocytes are regulated by 2 opposing signaling proteins in the cells of the surrounding follicle: the guanylyl cyclase natriuretic peptide receptor 2 (NPR2), and the luteinizing hormone receptor (LHR). NPR2 maintains a meiosis-inhibitory level of cyclic guanosine 5′-monophosphate (cGMP) until LHR signaling causes dephosphorylation of NPR2, reducing NPR2 activity, lowering cGMP to a level that releases meiotic arrest. However, the signaling pathway between LHR activation and NPR2 dephosphorylation remains incompletely understood, due in part to imprecise information about the cellular localization of these 2 proteins. To investigate their localization, we generated mouse lines in which hemagglutinin epitope tags were added to the endogenous LHR and NPR2 proteins, and used immunofluorescence and immunogold microscopy to localize these proteins with high resolution. The results showed that the LHR protein is absent from the cumulus cells and inner mural granulosa cells, and is present in only 13% to 48% of the outer mural granulosa cells. In contrast, NPR2 is present throughout the follicle, and is more concentrated in the cumulus cells. Less than 20% of the NPR2 is in the same cells that express the LHR. These results suggest that to account for the LH-induced inactivation of NPR2, LHR-expressing cells send a signal that inactivates NPR2 in neighboring cells that do not express the LHR. An inhibitor of gap junction permeability attenuates the LH-induced cGMP decrease in the outer mural granulosa cells, consistent with this mechanism contributing to how NPR2 is inactivated in cells that do not express the LHR.

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Cellular heterogeneity of the LH receptor and its significance for cyclic GMP signaling in mouse preovulatory follicles

10.1101/2020.02.06.937995 ◽

2020 ◽

Cited By ~ 1

Author(s):

Valentina Baena ◽

Corie M. Owen ◽

Tracy F. Uliasz ◽

Katie M. Lowther ◽

Siu-Pok Yee ◽

...

Keyword(s):

Granulosa Cells ◽

Cyclic Gmp ◽

Cellular Localization ◽

Cumulus Cells ◽

Luteinizing Hormone Receptor ◽

Cellular Heterogeneity ◽

Signaling Proteins ◽

Meiotic Arrest ◽

Lh Receptor ◽

Preovulatory Follicles

AbstractMeiotic arrest and resumption in mammalian oocytes are regulated by two opposing signaling proteins in the cells of the surrounding follicle: the guanylyl cyclase NPR2, and the luteinizing hormone receptor (LHR). NPR2 maintains a meiosis-inhibitory level of cyclic GMP (cGMP) until LHR signaling causes dephosphorylation of NPR2, reducing NPR2 activity, lowering cGMP to a level that releases meiotic arrest. However, the signaling pathway between LHR activation and NPR2 dephosphorylation remains incompletely understood, due in part to imprecise information about the cellular localization of these two proteins. To investigate their localization, we generated mouse lines in which HA epitope tags were added to the endogenous LHR and NPR2 proteins, and used immunofluorescence and immunogold microscopy to localize these proteins with high resolution. The results showed that the LHR protein is absent from the cumulus cells and inner mural granulosa cells, and is present in only 13-48% of the outer mural granulosa cells. In contrast, NPR2 is present throughout the follicle, and is more concentrated in the cumulus cells. Less than 20% of the NPR2 is in the same cells that express the LHR. These results suggest that to account for the LH-induced inactivation of NPR2, LHR-expressing cells send a signal that inactivates NPR2 in neighboring cells that do not express the LHR. An inhibitor of gap junction permeability attenuates the LH-induced cGMP decrease in the outer mural granulosa cells, consistent with this mechanism contributing to how NPR2 is inactivated in cells that do not express the LHR.

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Human Granulosa Cells—Stemness Properties, Molecular Cross-Talk and Follicular Angiogenesis

Cells ◽

10.3390/cells10061396 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1396

Author(s):

Claudia Dompe ◽

Magdalena Kulus ◽

Katarzyna Stefańska ◽

Wiesława Kranc ◽

Błażej Chermuła ◽

...

Keyword(s):

Stem Cells ◽

Granulosa Cells ◽

Polycystic Ovary ◽

Ovarian Follicle ◽

Cumulus Cells ◽

Ovary Syndrome ◽

Different Types ◽

Metabolite Exchange ◽

Reproductive Techniques ◽

New Strategies

The ovarian follicle is the basic functional unit of the ovary, comprising theca cells and granulosa cells (GCs). Two different types of GCs, mural GCs and cumulus cells (CCs), serve different functions during folliculogenesis. Mural GCs produce oestrogen during the follicular phase and progesterone after ovulation, while CCs surround the oocyte tightly and form the cumulus oophurus and corona radiata inner cell layer. CCs are also engaged in bi-directional metabolite exchange with the oocyte, as they form gap-junctions, which are crucial for both the oocyte’s proper maturation and GC proliferation. However, the function of both GCs and CCs is dependent on proper follicular angiogenesis. Aside from participating in complex molecular interplay with the oocyte, the ovarian follicular cells exhibit stem-like properties, characteristic of mesenchymal stem cells (MSCs). Both GCs and CCs remain under the influence of various miRNAs, and some of them may contribute to polycystic ovary syndrome (PCOS) or premature ovarian insufficiency (POI) occurrence. Considering increasing female fertility problems worldwide, it is of interest to develop new strategies enhancing assisted reproductive techniques. Therefore, it is important to carefully consider GCs as ovarian stem cells in terms of the cellular features and molecular pathways involved in their development and interactions as well as outline their possible application in translational medicine.

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The Differential Metabolomes in Cumulus and Mural Granulosa Cells from Human Preovulatory Follicles

Reproductive Sciences ◽

10.1007/s43032-021-00691-3 ◽

2021 ◽

Author(s):

Er-Meng Gao ◽

Bongkoch Turathum ◽

Ling Wang ◽

Di Zhang ◽

Yu-Bing Liu ◽

...

Keyword(s):

Oocyte Maturation ◽

Granulosa Cells ◽

Quantitative Polymerase Chain Reaction ◽

Cumulus Cells ◽

Cholesterol Transport ◽

Vitro Fertilization ◽

Expression Of Genes ◽

Preovulatory Follicles ◽

Morphological Differences

AbstractThis study evaluated the differences in metabolites between cumulus cells (CCs) and mural granulosa cells (MGCs) from human preovulatory follicles to understand the mechanism of oocyte maturation involving CCs and MGCs. CCs and MGCs were collected from women who were undergoing in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) treatment. The differences in morphology were determined by immunofluorescence. The metabolomics of CCs and MGCs was measured by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) followed by quantitative polymerase chain reaction (qPCR) and western blot analysis to further confirm the genes and proteins involved in oocyte maturation. CCs and MGCs were cultured for 48 h in vitro, and the medium was collected for detection of hormone levels. There were minor morphological differences between CCs and MGCs. LC-MS/MS analysis showed that there were differences in 101 metabolites between CCs and MGCs: 7 metabolites were upregulated in CCs, and 94 metabolites were upregulated in MGCs. The metabolites related to cholesterol transport and estradiol production were enriched in CCs, while metabolites related to antiapoptosis were enriched in MGCs. The expression of genes and proteins involved in cholesterol transport (ABCA1, LDLR, and SCARB1) and estradiol production (SULT2B1 and CYP19A1) was significantly higher in CCs, and the expression of genes and proteins involved in antiapoptosis (CRLS1, LPCAT3, and PLA2G4A) was significantly higher in MGCs. The level of estrogen in CCs was significantly higher than that in MGCs, while the progesterone level showed no significant differences. There are differences between the metabolomes of CCs and MGCs. These differences may be involved in the regulation of oocyte maturation.

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