Identification of stage-specific polypeptides synthesized during murine preimplantation development.

[35S]Methionine-labeled extracts of mouse ova and preimplantation embryos were analyzed by two dimensional polyacrylamide gel electrophoresis. Of the 400-600 molecular species that have been resolved as distinct spots on autoradiograms of gels for every stage of development from unfertilized eggs to early blastocysts, particular attention has been paid to the identification of 36 of these proteins, each of which is expressed only for a portion of the period under investigation. These molecules are referred to as stage-specific polypeptides and they are biochemical markers of early embryonic development and differentiation.