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

Nature. 1989 Nov 30;342(6249):512-8. doi: 10.1038/342512a0.


The c-mos proto-oncogene product, pp39mos, is present in unfertilized Xenopus eggs, and disappears on fertilization. Microinjection of synthetic mos RNA into two-cell embryos induces cleavage arrest at metaphase. By contrast, egg cytosol extracts, when immunodepleted of endogenous pp39mos, lose their cleavage-arresting activity in injected embryos. These results demonstrate that Mos protein is the cytostatic factor CSF, long known as an endogenous meiotic inhibitor in vertebrate eggs.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blastomeres / cytology
  • Cell Division
  • Cleavage Stage, Ovum / cytology*
  • Fertilization
  • Growth Inhibitors
  • Immunologic Techniques
  • Meiosis*
  • Metaphase
  • Oocytes / physiology*
  • Proto-Oncogene Proteins / immunology
  • Proto-Oncogene Proteins / physiology*
  • Proto-Oncogene Proteins c-mos
  • Xenopus laevis


  • Growth Inhibitors
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-mos