[Phorbol ester disrupts the cleavage pattern in sea urchin embryos]

Phorbol-12-myristate-13-acetate (PMA) treatment (9-170 nM) of S. mirabilis embryos from the fertilization to the IV cleavage division resulted in morphogenesis disturbances, such as decrease of the intercellular contacts' extent of blastomeres during the first cleavage divisions, inhibition of micromere formation, and formation of multiple blastulae. After washing from PMA embryos remained viable up to the pluteus stage. Morphogenetic disturbances were not accompanied by changes of intracellular pH or mechanical properties of blastomeres' surface during cleavage. Protein kinase C is suggested to control adhesion of the cell surface and intracellular nucleus movements.