Differentiation of epidermal cells in the regenerating planarian Dugesia japonica

Distribution of the cytoplasmic components in planarian epidermal cells is highly polarized, just as in vertebrate epithelia. Differentiating epidermal cells of the planarian Dugesia japonica Ichikawa et Kawakatsu were found to have relatively conspicuous accumulations of microtubules in their apical cytoplasm. When colchicine, a microtubule-disrupting drug, was applied to regenerating worms, it reversibly disorganized the polarity of differentiating epidermal cells. Cytochalasin B, which depolymerizes actin filaments, had no significant effect on the polarization, however. Tubulin could be localized by immunocytochemistry in the cytoplasm of differentiating epidermal cells; this reaction was inhibited by treatment with colchicine for 20 h. These observations indicate that microtubules play a role in establishing polarity during cell differentiation.