title: Store-operated Ca2+entry is not required for fertilization-induced Ca2+signaling in mouse eggs.
abstract: Repetitive oscillations in cytoplasmic Ca2+due to periodic Ca2+release from the endoplasmic reticulum (ER) drive mammalian embryo development following fertilization. Influx of extracellular Ca2+to support the refilling of ER stores is required for sustained Ca2+oscillations, but the mechanisms underlying this Ca2+influx are controversial. Although store-operated Ca2+entry (SOCE) is an appealing candidate mechanism, several groups have arrived at contradictory conclusions regarding the importance of SOCE in oocytes and eggs. To definitively address this question, Ca2+influx was assessed in oocytes and eggs lacking the major components of SOCE, the ER Ca2+sensor STIM proteins, and the plasma membrane Ca2+channel ORAI1. We generated oocyte-specific conditional knockout (cKO) mice for Stim1 and Stim2, and also generated Stim1/2 double cKO mice. Females lacking one or both STIM proteins were fertile and their ovulated eggs displayed normal patterns of Ca2+oscillations following fertilization. In addition, no impairment was observed in ER Ca2+stores or Ca2+influx following store depletion. Similar studies were performed on eggs from mice globally lacking ORAI1; no abnormalities were observed. Furthermore, spontaneous Ca2+influx was normal in oocytes from Stim1/2 cKO and ORAI1-null mice. Finally, we tested if TRPM7-like channels could support spontaneous Ca2+influx, and found that it was largely prevented by NS8593, a TRPM7-specific inhibitor. Fertilization-induced Ca2+oscillations were also impaired by NS8593. Combined, these data robustly show that SOCE is not required to support appropriate Ca2+signaling in mouse oocytes and eggs, and that TRPM7-like channels may contribute to Ca2+influx that was previously attributed to SOCE.
authors.affiliation: Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Miranda L
authors.initials: ML
authors.lastname: Bernhardt
authors.affiliation: Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Padilla-Banks
authors.affiliation: Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Paula
authors.initials: P
authors.lastname: Stein
authors.affiliation: Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Yingpei
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA. Electronic address: williamsc5@niehs.nih.gov.
authors.forename: Carmen J
authors.initials: CJ
authors.lastname: Williams
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D005306:Fertilization / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D000071740:ORAI1 Protein / Q000235:genetics / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D000071737:Stromal Interaction Molecule 1 / Q000235:genetics / Q000378:metabolism; D000071738:Stromal Interaction Molecule 2 / Q000235:genetics / Q000378:metabolism
chemical_list: D000071740:ORAI1 Protein; C520430:Orai1 protein, mouse; C100757:Stim1 protein, mouse; C525024:Stim2 protein, mouse; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D002118:Calcium
keywords: Calcium; Egg activation; Fertilization; Oocyte; Store-operated calcium entry