Changes in protein synthesis during differentiation of embryonal carcinoma cells, and a comparison with embryo cells.

Two-dimensional electrophoresis was used to find changes in protein synthesis occurring as pluripotent embryonal carcinoma (EC) cells differentiate to give embryoid bodies in vitro. 2-D patterns from other embryonic cell lines, and from the inner cell mass (ICM) cells of mouse embryos, were also analysed for the expression of those proteins showing some change during embryoid body formation and for overall differences between these and the EC cells. Most changes in protein synthesis occurred before 12 h but endoderm was not discerned morphologically on the outside of EC cell clumps until at least 18 h after their suspension. The number of changes occurring is small compared with the number of polypeptides resolved, but is in line with similar studies. Comparisons with nullipotent EC cells and an endodermal cell line have allowed these changes to be assigned, tentatively, to the different cell types within embryoid bodies, and may allow them to be used as markers of differentiation. Comparisons between the 2-D patterns derived from ICMs and EC cells reveal substantial differences between the two that might not have been expected from their developmental homology. The importance of these differences to their pluripotentiality is discussed.