RESTRICTION OF CELL FATE OF SUPERFICIAL CELLS IN THE MARGINAL ZONE OFTHE AMPHIBIAN EMBRYO PLEURODELES WALTL

The fate of circumblastoral cells has been studied in the Pleurodeles waltl late blastula and early gastrula. Individual superficial cells w ere labeled in defined regions with a fluorescent cell lineage tracer. Labeled progeny were located in sectioned tail bud stage embryos. The injection of defined cells at different developmental stages allowed us to compare the fates of superficial cells in similar locations in l ate blastula and early gastrula stages and thus to study the restricti on of developmental fate. A progressive spatial and temporal restricti on of cell fate was observed when comparing clones of cells derived fr om an injected blastula stage cell and an injected gastrula stage cell . At the blastula stage, the dorsal and dorsolateral regions contain f ew cells already restricted in their developmental fate to a single me sodermal organ. In contrast, at the gastrula stage, most cells in the dorsal and dorsolateral regions give rise to a single mesodermal deriv ative, whereas ventrolateral and ventral cells still form mesodermal d erivatives but also form ectodermal and endodermal derivatives. (C) 19 95 Wiley-Liss, Inc.