Cytoplasmic and nucleic calcium oscillations in immature mouse oocytes: evidence of wave polarization by confocal imaging.
Using confocal laser scanning microscopy and time-lapse reconstruction, we monitored [Ca2+]i in living mouse oocytes loaded with the calcium-sensitive fluorescent dyes fluo-3/AM or NuCa Green (specific for nuclear calcium) at the time of meiosis reinitiation. Our data confirm that spontaneous Ca2+ oscillations occurred in most of the immature fully grown mouse oocytes at least during the first half hour after release of the follicle and these oscillating oocytes underwent GVB in a large proportion after 1 h of culture. These spontaneous oscillations were disrupted when GVB was inhibited by dbcAMP and suppressed in the absence of external calcium. They were dependent on intracellular InsP3-sensitive Ca2+ stores since they were inhibited by heparin, an InsP3-receptor antagonist, or thapsigargin, which depletes InsP3-sensitive Ca2+ stores. A relation appeared between the germinal vesicle chromatin appearance and the oocyte's ability to exhibit calcium oscillations. NuCa Green-loaded oocytes exhibited clear fluorescence oscillations in the nuclear region which lead us to discuss the implication of the nuclear calcium in the meiotic process. Moreover, the observation of a clear polarization of the Ca2+ waves in 30% of the oocytes permits us to hypothesize the existence of a predetermined localization for the initial point of the calcium wave.
Lefèvre
B
B
Institut National de la Santé et de la Recherche Médicale (I.N.S.E.R.M) Unité 355, Clamart, France.
Pesty
A
A
Testart
J
J
D000814:Aniline Compounds; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism; D003911:Dextrans; D005260:Female; D005456:Fluorescent Dyes; D007700:Kinetics; D008540:Meiosis / Q000502:physiology; D051379:Mice; D008845:Microinjections; D018613:Microscopy, Confocal / Q000379:methods; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors; D014966:Xanthenes
D000814:Aniline Compounds; D002843:Chromatin; D003911:Dextrans; D005456:Fluorescent Dyes; C093366:NuCa Green; D013729:Terpenes; D014966:Xanthenes; C059715:Fluo-3; D003994:Bucladesine; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium