Calcium signaling differentiation during Xenopus oocyte maturation

Wassim El-Jouni, Byungwoo Jang, Shirley Haun, Khaled Machaca

Research output: Contribution to journalArticle

46 Citations (Scopus)


Ca2+ is the universal signal for egg activation at fertilization in all sexually reproducing species. The Ca2+ signal at fertilization is necessary for egg activation and exhibits specialized spatial and temporal dynamics. Eggs acquire the ability to produce the fertilization-specific Ca2+ signal during oocyte maturation. However, the mechanisms regulating Ca2+ signaling differentiation during oocyte maturation remain largely unknown. At fertilization, Xenopus eggs produce a cytoplasmic Ca2+ (Ca2+cyt) rise that lasts for several minutes, and is required for egg activation. Here, we show that during oocyte maturation Ca2+ transport effectors are tightly modulated. The plasma membrane Ca2+ ATPase (PMCA) is completely internalized during maturation, and is therefore unable to extrude Ca 2+ out of the cell. Furthermore, IP3-dependent Ca 2+ release is required for the sustained Ca2+ cyt rise in eggs, showing that Ca2+ that is pumped into the ER leaks back out through IP3 receptors. This apparent futile cycle allows eggs to maintain elevated cytoplasmic Ca2+ despite the limited available Ca2+ in intracellular stores. Therefore, Ca 2+ signaling differentiates in a highly orchestrated fashion during Xenopus oocyte maturation endowing the egg with the capacity to produce a sustained Ca2+cyt transient at fertilization, which defines the egg's competence to activate and initiate embryonic development.

Original languageEnglish
Pages (from-to)514-525
Number of pages12
JournalDevelopmental Biology
Issue number2
Publication statusPublished - 15 Dec 2005



  • Ca signaling
  • Endocytosis
  • IP receptor
  • Oocyte maturation
  • Plasma membrane Ca ATPase
  • Xenopus

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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