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The c-mos proto-oncogene product is a cytostatic factor responsible for meiotic arrest in vertebrate eggs

N Sagata1, N Watanabe, G F Vande Woude

  • 1Tsukuba Science Center (RIKEN), Ibaraki, Japan.

Nature
|November 30, 1989
PubMed

Insights

Mos protein is identified as the cytostatic factor (CSF) in Xenopus eggs. This key protein inhibits meiosis and its levels decrease upon fertilization, impacting embryonic development.

Area of Science:

  • Cell Biology
  • Developmental Biology
  • Molecular Oncology

Background:

  • The c-mos proto-oncogene product, pp39mos, is known to be present in unfertilized Xenopus eggs.
  • Fertilization triggers the disappearance of pp39mos in Xenopus eggs.
  • A cytostatic factor (CSF) has been long recognized as an endogenous meiotic inhibitor in vertebrate eggs.

Purpose of the Study:

  • To identify the molecular identity of the cytostatic factor (CSF) responsible for meiotic inhibition in Xenopus eggs.
  • To investigate the role of pp39mos in regulating embryonic cell cycle progression.

Main Methods:

  • Microinjection of synthetic mos RNA into two-cell Xenopus embryos.
  • Immunodepletion of endogenous pp39mos from egg cytosol extracts.
  • Assessment of cleavage arrest at metaphase in injected embryos.

Main Results:

  • Microinjection of mos RNA induced cleavage arrest at metaphase in Xenopus embryos.
  • Egg cytosol extracts depleted of pp39mos lost their cleavage-arresting activity.
  • These findings directly link Mos protein to the CSF activity.

Conclusions:

  • Mos protein is the functional cytostatic factor (CSF) in Xenopus eggs.
  • Mos protein plays a critical role in regulating meiotic arrest and embryonic cell cycle progression.
  • The regulation of Mos protein levels is a key event in Xenopus egg activation and development.

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