title: Protein kinase C activity regulates the onset of anaphase I in mouse oocytes.
abstract: The metaphase-to-anaphase I transition is a key step in the completion of meiosis I. In mouse oocytes, competence to exit metaphase I (MI) is developmentally regulated and typically not acquired until the preovulatory stage. The possible role of protein kinase C (PKC) in regulating this critical transition was assessed in both normal oocytes isolated from small antral follicles (18-day-old B6SJLF1 mice), which have not yet developed the capacity to progress to metaphase II (MII), and also oocytes defective in their ability to exit MI despite development to the preovulatory stage (24-day-old CX8 recombinant inbred strains). In both systems, transient suppression of endogenous PKC activity by treatment with a PKC-specific inhibitor, bisindolylmaleimide I (BIM), promoted the onset of anaphase I in a dose-dependent manner, while activation of PKC with the phorbol ester TPA blocked progression to MII. Following a 2-h incubation with BIM, the majority of oocytes progressed to, and arrested at, MII. The resulting MII oocytes were fertilizable in vitro, showing similar cleavage and blastocyst development rates between BIM treated and untreated controls. Transferred embryos resulted in the development of pups to term in both groups. These data demonstrate that PKC plays an important role in regulating the onset of anaphase I in mouse oocytes. Moreover, it is concluded that oocytes isolated from small antral follicles become blocked at MI due to a PKC-mediated signal, suggesting that acquisition of competence to complete meiosis I involves, in part, the control of PKC activity. Similarly, failure to regulate PKC activity at the preovulatory stage likely promotes arrest at MI.
authors.affiliation: Center for Animal Transgenesis and Germ Cell Research, Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania 19348, USA. viveiros@vet.upenn.edu
authors.forename: Maria M
authors.initials: MM
authors.lastname: Viveiros
authors.forename: Marilyn
authors.initials: M
authors.lastname: O'brien
authors.forename: John J
authors.initials: JJ
authors.lastname: Eppig
mesh_terms: D000705:Anaphase / Q000502:physiology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D047108:Embryonic Development / Q000502:physiology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology; D008301:Maleimides / Q000008:administration & dosage / Q000494:pharmacology; D008677:Metaphase / Q000502:physiology; D051379:Mice; D008815:Mice, Inbred Strains; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D011493:Protein Kinase C; C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate