Embryonic cell commitment by a simultaneous alteration in nucleo/cytoplasmic ratio in sibling cells between subsequent cell cycles

Studies on murine embryonal carcinoma (EC) cell lines have revealed a mechanism for commitment of early embryonic cells. By means of a particular intraclonal cell surface glycoprotein and intermitotic time heterogeneity found in the EC lines used, we have devised a cell cycle model and written a computer program for cell cycle stimulation. In the present investigation experimental tissue culture data obtained from the EC lines were inserted into the computer program and the simulations represent a good fit to experimental data. It is shown that the dynamics of the driving forces in the 'cell growth cycle' and the 'DNA-division cycle', when assumed to be loosely coupled and analyzed in subsequent cell cycles, reveal a mechanism that can commit the mother cell to impel her daughter cells into the next stage in embryonic development by altering the relationship between those two uncoupled subcycles. Thereby the nucleo/cytoplasmic ratio (DNA/mass) is altered in a similar way in the two daughter cells. The simulations increase the reliability of the model and open up possibilities to test other embryonic cell systems.