Involvment of the cytoskeleton in localization of P. lividus maternal mRNAs and proteins.

The maternal bep1 and bep4 mRNAs and their proteic products are localized at the animal pole of Paracentrotus lividus eggs. We have examined the role of the cytoskeleton in localization both of bep RNAs and BEP proteins in unfertilized and fertilized eggs and in determining the polarity of P. lividus eggs. The use of drugs such as colchicine and cytochalasin B, which depolymerize microtubules and microfilaments respectively, revealed a perturbation of localization of bep1 and bep4 mRNAs. In contrast, the microfilament inhibitor cytochalasin B had no effect on localization of BEP1 and BEP4 antigens localization, which appear to be due only to microtubules. Moreover, the presence of bepmRNAs and BEP proteins in a microtubule preparation has been demonstrated. Maintenance of the asymmetric distribution of BEP proteins during cellular division of eggs and embryos, by association with mitotic spindle, is also shown.