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Mammalian egg activation: from Ca2+ spiking to cell cycle progression
1Institute for Cell and Molecular Biosciences, The Medical School, Framlington Place, University of Newcastle, Newcastle, NE2 4HH, UK. k.t.jones@newcastle.ac.uk
Reproduction (Cambridge, England)
|December 3, 2005
Summary
Sperm trigger mammalian egg activation through calcium (Ca2+) spikes, initiating cell cycle resumption and development. This process involves phospholipase C zeta (PLCzeta) and the Anaphase-Promoting Complex/Cyclosome (APC/C).
Area of Science:
- Reproductive Biology
- Cellular Biology
- Developmental Biology
Background:
- Mammalian eggs arrest at the second meiotic metaphase (MetII).
- Sperm initiate egg activation via calcium (Ca2+) spikes, crucial for cell cycle resumption.
- This activation involves sister chromatid separation and polar body extrusion.
Purpose of the Study:
- To review the mechanisms of MetII arrest establishment.
- To elucidate the induction of sperm-induced Ca2+ spiking.
- To explain the signal transduction pathway for cell cycle resumption.
Main Methods:
- Review of existing literature on mammalian egg activation.
- Presentation of a model for Ca2+ signaling and cell cycle control.
- Discussion of key molecular players like PLCzeta and APC/C.
Main Results:
- Sperm-specific phospholipase C zeta (PLCzeta) generates Ca2+ spikes.
- Ca2+ spikes activate calmodulin-dependent protein kinase II.
- This activation leads to Anaphase-Promoting Complex/Cyclosome (APC/C) activation.
Conclusions:
- Sperm-induced Ca2+ spiking is essential and sufficient for egg activation.
- APC/C activation drives securin and cyclin B1 degradation.
- This degradation enables sister chromatid segregation and chromatin decondensation.