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 parti cular intraclonal cell surface glycoprotein and intermitotic time hete rogeneity found in the EC lines used, we have devised a cell cycle mod el and written a computer program for cell cycle stimulation. In the p resent investigation experimental tissue culture data obtained from th e EC lines were inserted into the computer program and the simulations represent a good fit to experimental data. It is shown that the dynam ics of the driving forces in the 'cell growth cycle' and the 'DNA-divi sion cycle', when assumed to be loosely coupled and analyzed in subseq uent cell cycles, reveal a mechanism that can commit the mother cell t o impel her daughter cells into the next stage in embryonic developmen t by altering the relationship between those two uncoupled subcycles. Thereby the nucleo/cytoplasmic ratio (DNA/mass) is altered in a simila r way in the two daughter cells. The simulations increase the reliabil ity of the model and open up possibilities to test other embryonic cel l systems.