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Updated: Aug 7, 2026
06:31
Reconstitution of Cell-cycle Oscillations in Microemulsions of Cell-free Xenopus Egg Extracts
Published on: September 27, 2018
Calcium oscillations in Xenopus egg cycling extracts
A A Tokmakov1, K I Sato, Y Fukami
1Laboratory of Molecular Biology, Biosignal Research Center, Kobe University, Nada, Kobe 657-8501, Japan. tokmak@kobe-u.ac.jp
Journal of Cellular Biochemistry
|June 16, 2001
Summary
Calcium oscillations regulate the cell cycle in Xenopus egg extracts. Cyclic calcium (Ca2+) fluctuations, peaking in metaphase, are essential for cell cycle progression and mitotic entry.
Area of Science:
- Cell Biology
- Developmental Biology
- Biochemistry
Background:
- Cell cycle progression and early embryonic development involve dynamic changes in intracellular calcium levels.
- Transient fluctuations in free cytosolic calcium concentration are characteristic of the cell cycle in various cell types and early embryos.
Purpose of the Study:
- To investigate the role and regulation of cyclic calcium (Ca2+) oscillations in cell-free Xenopus egg extracts during the cell cycle.
- To identify the source of Ca2+ and the mechanisms controlling its release within the cycling extracts.
Main Methods:
- Utilized fluorescent indicator fura-2 to monitor Ca2+ concentrations in cell-free Xenopus egg extracts.
- Employed inositol 1,4,5-trisphosphate (IP3) to stimulate Ca2+ release from intracellular stores.
- Used heparin as an IP3 receptor antagonist and BAPTA as a calcium chelator to assess the impact of Ca2+ levels on cell cycle progression.
Main Results:
- Demonstrated cyclic Ca2+ oscillations (approx. 100 nM amplitude) in synchrony with the mitotic cycle, peaking in early metaphase and reaching a minimum in interphase.
- Identified intracellular Ca2+ stores within a particulate fraction as the source of Ca2+, responsive to IP3 stimulation.
- Showed that Ca2+ depletion using BAPTA or inhibition of IP3-induced release with heparin arrested the cell cycle at specific stages, including prophase, metaphase, and interphase.
Conclusions:
- Cyclic Ca2+ oscillations are crucial for regulating the cell cycle in Xenopus egg extracts, with specific phases of oscillation correlating with cell cycle transitions.
- Inositol 1,4,5-trisphosphate-mediated release of Ca2+ from intracellular stores plays a key role in driving these oscillations and subsequent cell cycle progression.
- Disruption of Ca2+ homeostasis through chelation or inhibition of IP3 signaling leads to cell cycle arrest, highlighting the critical dependence of cell division on precise calcium dynamics.
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