Ca2+ cyt negatively regulates the initiation of oocyte maturation

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Abstract

Ca2+ is a ubiquitous intracellular messenger that is important for cell cycle progression. Genetic and biochemical evidence support a role for Ca2+ in mitosis. In contrast, there has been a long-standing debate as to whether Ca2+ signals are required for oocyte meiosis. Here, we show that cytoplasmic Ca2+ (Ca2+ cyt) plays a dual role during Xenopus oocyte maturation. Ca2+ signals are dispensable for meiosis entry (germinal vesicle breakdown and chromosome condensation), but are required for the completion of meiosis I. Interestingly, in the absence of Ca2+ cyt signals oocytes enter meiosis more rapidly due to faster activation of the MAPK-maturation promoting factor (MPF) kinase cascade. This Ca2+-dependent negative regulation of the cell cycle machinery (MAPK-MPF cascade) is due to Ca2+ cyt acting downstream of protein kinase A but upstream of Mos (a MAPK kinase kinase). Therefore, high Ca2+ cyt delays meiosis entry by negatively regulating the initiation of the MAPK-MPF cascade. These results show that Ca2+ modulates both the cell cycle machinery and nuclear maturation during meiosis.

Original languageEnglish
Pages (from-to)63-75
Number of pages13
JournalJournal of Cell Biology
Volume165
Issue number1
DOIs
Publication statusPublished - 12 Apr 2004
Externally publishedYes

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Keywords

  • Calcium
  • Cell cycle
  • Meiosis
  • Meiotic maturation
  • Xenopus

ASJC Scopus subject areas

  • Cell Biology

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