Partition of protein (mass) to sister cell pairs at mitosis: a re-evaluation.

Since the 1960s it has been thought that there is to some extent a difference in the partition of mass to daughter cells at mitosis. Recent studies using modern techniques give further support to such a phenomenon, which has become almost an axiom in cell biology. It has been suggested that such unequal distribution of metabolic constituents at mitosis contributes to the dispersion in cell generation times. In the present work, PCC3 embryonal carcinoma (EC) cells were studied as undifferentiated G1 sister pairs by microspectrophotometry (MSP) following Feulgen-Naphthol Yellow staining (FNYS), in order to evaluate their protein content. Despite the considerable intraclonal intermitotic time heterogeneity found in undifferentiated PCC3 EC cells, it was concluded thta the postmitotic difference in mass (protein) between sister cell pairs exerts a minimal influence upon the cell population mass variability, whereas it was deduced to have an influence upon variation in interphase time duration when comparing sister cell pairs. This offers a cell-physiological explanation to the randomly distributed difference repeatedly found between sister cell generation times. Furthermore, there was no correlation seen between the mass difference found between sister cell pairs postmitotically and the size of the mother cell.