The influence of cell contact on the division of mouse 8-cell blastomeres.

The pattern of division of polarized 8-cell blastomeres with respect to the axis of cell polarity has been compared (i) for cells dividing alone with cells dividing in pairs, and (ii) for early and late dividing cells within a pair. Cell interactions do not seem to influence significantly the overall pattern of division within the population. The only significant difference found was that the second dividing cell in a pair tended to divide in the same way as its earlier dividing companion slightly more frequently than expected. These results suggest that cell interactions immediately prior to and during division do not influence strongly the orientation and position of the division plane. In contrast, interactions between the cells within an intact early 8-cell embryo, which is subsequently disaggregated to singletons or pairs, do influence the type of progeny generated at division to the 16-cell stage, and seem to do so via an effect on the size of the microvillous region generated at the cell apex.