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Published on: January 26, 2013

Regulation of the cell cycle during early Xenopus development

J W Newport, M W Kirschner

    Cell
    |July 1, 1984
    PubMed

    Insights

    Maturation-promoting factor (MPF) drives the cell cycle in frog eggs, controlling mitosis and DNA replication without new protein synthesis. Calcium ions restart the cell cycle by affecting MPF activity.

    Area of Science:

    • Cell Biology
    • Developmental Biology

    Background:

    • Maturation-promoting factor (MPF) is a key regulator of M-phase.
    • MPF activity is conserved across diverse species.
    • Frog oocytes are a model system for studying cell cycle control.

    Purpose of the Study:

    • To investigate the role of MPF in driving the mitotic cell cycle in frog eggs.
    • To understand how MPF activity is regulated by cytoplasmic factors and calcium ions.
    • To elucidate the mechanism by which MPF influences DNA replication.

    Main Methods:

    • Partial purification of MPF from frog egg lysates.
    • Microinjection of MPF and cytoplasm into frog eggs.
    • Monitoring of cell cycle events, including nuclear membrane dynamics, chromosome condensation, and DNA replication.
    • Assessment of MPF activity levels.

    Main Results:

    • MPF addition and removal, without protein synthesis, drove the complete mitotic cycle in frog eggs.
    • M-phase arrest induced by egg cytoplasm stabilized MPF activity.
    • Calcium ion injection restarted the cell cycle oscillator, decreasing MPF activity.
    • DNA replication response to MPF levels was mediated by chromatin template, not replication machinery.

    Conclusions:

    • Cell cycle events in Xenopus embryos, including mitosis and DNA replication, are controlled by MPF activity levels.
    • MPF activity is linked to an autonomous cytoplasmic cell-cycle oscillator.
    • The simple embryonic cell cycle may provide a basis for understanding more complex somatic cell cycles.

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