Polarized distribution of membrane components on two-cell mouse embryos

In two-cell mouse embryos, membrane components detected by a variety of antisera, lectins and lipid analogues and covalent labeling were found to be localized in the poles of the two blastomeres opposite the cleavage furrow. The proportion of polarized blastomeres increased rapidly during the first 4-5 h following first cleavage and then diminished approximately two-fold over the remaining period before second cleavage. Concurrent with this decrease in percent polarization, observed poles were found to be less spatially restricted. This polarization is not the result of a ligand induced capping or a manifestation of differences in surface topography. In light of recent measurements of lateral diffusion, the polarization of membrane components may be significant for the formation of morphogenetic gradients during cleavage.