EXPRESSION OF AN EXTRACELLULAR DELETION OF XOTCH DIVERTS CELL FATE IN XENOPUS-EMBRYOS

Xotch is a Xenopus homolog of Notch, a receptor involved in cell fate decisions in Drosophila. Using an extracellular deletion construct, XotchDELTAE, we show that Xotch has a similar role in Xenopus embryos. Broad expression causes the loss of dorsal structures and the expansion and disorganization of the brain. Single blastomere injections of XotchDELTAE induce autonomous neural and mesodermal hypertrophy, even in the absence of cell division. XotchDELTAE inhibits the early expression of epidermal and neural crest markers yet enhances and extends the response of animal caps to mesodermal and neural induction. Our data suggest a mechanism for the function of Notch homologs in which they delay differentiation and leave undetermined cells competent to respond to later inductive signals.