title: Preovulatory suppression of mouse oocyte cell volume-regulatory mechanisms is via signalling that is distinct from meiotic arrest.
abstract: GLYT1-mediated glycine transport is the main cell volume-homeostatic mechanism in mouse eggs and early preimplantation embryos. It is unique to these developmental stages and key to their healthy development. GLYT1 first becomes activated in oocytes only after ovulation is triggered, when meiotic arrest of the oocyte is released, but how this occurs was unknown. Here we show that GLYT1 activity is suppressed in oocytes in the preovulatory antral follicle and that its suppression is mediated by a mechanism distinct from the gap junction-dependent Natriuretic Peptide Precursor C (NPPC) pathway that controls meiotic arrest. GLYT1 remained suppressed in isolated antral follicles but not isolated cumulus-oocyte complexes (COCs) or isolated oocytes. Moreover, activating the NPPC signalling pathway could not prevent GLYT1 activation in oocytes within COCs despite maintaining meiotic arrest. Furthermore, blocking gap junctions in isolated follicles failed to induce GLYT1 activity in enclosed oocytes for an extended period after meiosis had resumed. Finally, isolated mural granulosa cells from preovulatory antral follicles were sufficient to suppress GLYT1 in oocytes within co-cultured COCs. Together, these results suggest that suppression of GLYT1 activity before ovulation is mediated by a novel signalling pathway likely originating from preovulatory mural granulosa cells.
authors.affiliation: Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.|Department of Obstetrics and Gynecology and Department of 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. jbaltz@ohri.ca.|Department of Obstetrics and Gynecology and Department of Cellular and Molecular Medicine, University of Ottawa Faculty of Medicine, Ottawa, Ontario, Canada. jbaltz@ohri.ca.
authors.forename: Jay M
authors.identifier: http://orcid.org/0000-0002-9749-2480
authors.initials: JM
authors.lastname: Baltz
mesh_terms: D000818:Animals; D002450:Cell Communication; D059447:Cell Cycle Checkpoints; D048429:Cell Size; D054885:Cumulus Cells / Q000166:cytology / Q000378:metabolism; D005260:Female; D017629:Gap Junctions / Q000378:metabolism; D050487:Glycine Plasma Membrane Transport Proteins / Q000819:agonists / Q000378:metabolism; D006107:Granulosa Cells / Q000378:metabolism; D008540:Meiosis; D051379:Mice; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism*; D009866:Oogenesis; D006080:Ovarian Follicle / Q000166:cytology; D010060:Ovulation; D015398:Signal Transduction
chemical_list: D050487:Glycine Plasma Membrane Transport Proteins; C493267:Slc6a9 protein, mouse