FATES OF THE BLASTOMERES OF THE 32-CELL STAGE PLEURODELES WALTL EMBRYO

Cell fate of the blastomeres at the 32-cell stage in the Pleurodeles w altl embryo was analyzed by injection of rhodamine or fluorescein lysi nated-dextran (RLDx or FLDx). At the tailbud stage, the progeny of eac h blastomere contributed to more than one germ layer with unequal dist ribution along the anteroposterior and dorsoventral axis. Such a regio nalized positioning of the descendants of the 32-cell blastomeres was found in the neuroectoderm, the epidermis, the notochord, the somites, the lateral plate, and the endoderm, but not in the head mesenchyme, the pronephros, or the blood islands. Results of double labeling of ju xtaposed blastomeres showed that cell mixing and rearrangement take pl ace during organ formation. Results are compared with those of the 32- cell stage fate map in Xenopus and Rana and reveal the more restricted fate of 32-cell stage blastomeres in Pleurodeles germ layers. (C) 199 7 Wiley-Liss, Inc.