title: Prophase I arrest of mouse oocytes mediated by natriuretic peptide precursor C requires GJA1 (connexin-43) and GJA4 (connexin-37) gap junctions in the antral follicle and cumulus-oocyte complex.
abstract: Fully grown germinal vesicle stage mouse oocytes remain arrested in meiotic prophase I until ovulation. This arrest is maintained by cGMP produced in cumulus granulosa cells surrounding the oocyte. Recently, it was found that cGMP production in cumulus cells depends on NPR2 guanylate cyclase activated by its ligand natriuretic peptide precursor C (NPPC). It is assumed that cGMP reaches the oocyte through gap junctions that couple cumulus granulosa cells to each other and to the oocyte. Previous work identified two main types of gap junctions in the follicle, connexin-43 gap junctions (GJA1 protein) between granulosa cells and connexin-37 gap junctions (GJA4) between cumulus cells and the oocyte. However, it had not been established that both types are required for meiotic arrest mediated by NPPC/NPR2 signaling. To investigate this, we used connexin mimetic peptides (CMPs) that specifically disrupt gap junction isoforms within cumulus-oocyte complexes (COCs) and isolated antral follicles in culture. We furthermore developed a punctured antral follicle preparation to permit CMP access to the antral cavity in an otherwise intact follicle. CMP directed against connexin-43 (Cx43 CMP) overcame NPPC-mediated meiotic arrest in both isolated COCs and antral follicles. Cx37 CMP, in contrast, had no effect when present in the medium, but released oocyte arrest in the presence of NPPC when microinjected into the perivitelline space near the oocyte surface in COCs. This is consistent with both connexin isoforms being required for meiotic arrest and with the reported localization of connexin-43 throughout the cumulus cells and connexin-37 at the oocyte surface.
authors.affiliation: Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, and Departments of Obstetrics and Gynecology, and Cellular and Molecular Medicine, University of Ottawa Faculty of Medicine, Ottawa, Ontario, Canada.
authors.forename: Samantha
authors.initials: S
authors.lastname: Richard
authors.affiliation: Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, and Departments of Obstetrics and Gynecology, and Cellular and Molecular Medicine, University of Ottawa Faculty of Medicine, Ottawa, Ontario, Canada jbaltz@ohri.ca.
authors.forename: Jay M
authors.initials: JM
authors.lastname: Baltz
mesh_terms: D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology; D018031:Connexin 43 / Q000378:metabolism*; D017630:Connexins / Q000378:metabolism*; D054885:Cumulus Cells / Q000166:cytology / Q000378:metabolism; D005260:Female; D005298:Fertility / Q000502:physiology; D017629:Gap Junctions / Q000502:physiology*; D049469:Meiotic Prophase I / Q000502:physiology*; D051379:Mice; D020098:Natriuretic Peptide, C-Type / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D006080:Ovarian Follicle / Q000166:cytology / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D017461:Receptors, Atrial Natriuretic Factor / Q000378:metabolism; D000097006:Gap Junction alpha-4 Protein; D000099242:Atrial Natriuretic Factor Receptor B
chemical_list: D018031:Connexin 43; D017630:Connexins; D020098:Natriuretic Peptide, C-Type; D011498:Protein Precursors; D017461:Receptors, Atrial Natriuretic Factor; D000097006:Gap Junction alpha-4 Protein; D000099242:Atrial Natriuretic Factor Receptor B; C543076:GJA1 protein, mouse; C553310:natriuretic peptide precursor type C, mouse
keywords: connexins; cumulus cells; gap junctions; oocyte; oocyte-follicle interactions