Oocyte Maturation and Cell Cycle Regulation in Echinoderms and Mammals
Summary
Oocyte maturation is the process by which quiescent germ cells resume meiosis and acquire competence for fertilisation. In both echinoderms and mammals, this transition relies on tightly controlled activation of maturation-promoting factor (MPF), a complex of cyclin-dependent kinase 1 (CDK1) and cyclin B. In echinoderms such as starfish, a steroid hormone trigger engages a G-protein-coupled receptor and a phosphatidylinositol 3-kinase (PI3K)-dependent cascade leading to serum- and glucocorticoid-regulated kinase (SGK) activation. SGK both raises intracellular pH and promotes de-phosphorylation of CDK1 regulators, culminating in germinal vesicle breakdown and first meiotic spindle formation. In mammals, luteinising hormone induces translation and stabilisation of cyclin B1 and activation of Polo-like kinase 1, while a cytostatic factor network centred on Emi2 maintains arrest at metaphase II until fertilisation. Across phyla, feedback loops between kinase activation, phosphatase inhibition and proteolytic degradation of cyclin B ensure that the meiotic divisions occur with high fidelity. Comparative studies have highlighted conserved principles, such as threshold mechanisms for CDK1 activation and the pivotal role of calcium-triggered events at fertilisation, alongside species-specific variations in checkpoint controls and spindle dynamics.
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Oocyte Maturation and Cell Cycle Regulation in Echinoderms and Mammals publication trend
The graph below shows the total number of articles in oocyte maturation and cell cycle regulation in echinoderms and mammals across all publications each year (not limited to Nature Index journals).
Technical terms
Germinal vesicle breakdown (GVBD): Dissolution of the oocyte nucleus indicating resumption of meiosis.
Maturation-promoting factor (MPF): Cyclin B–CDK1 complex that drives entry into meiotic M-phase.
Serum- and glucocorticoid-regulated kinase (SGK): Kinase activated downstream of PI3K that controls pH and CDK1 regulators in echinoderm oocytes.
Cytostatic factor (CSF): Network of proteins, including Emi2, that maintain metaphase II arrest in mammalian oocytes.
Threshold mechanism: Regulatory circuit that sets a hormone-dependent level of kinase activation required for irreversible cell-cycle transitions.
References
- MPF-based meiotic cell cycle control: Half a century of lessons from starfish oocytes. Proceedings of the Japan Academy Series B (2018).
- Two new competing pathways establish the threshold for cyclin-B–Cdk1 activation at the meiotic G2/M transition. Journal of Cell Science (2016).
- SGK regulates pH increase and cyclin B–Cdk1 activation to resume meiosis in starfish ovarian oocytes. Journal of Cell Biology (2019).
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