Notch is required for outgrowth of the Xenopus tail bud.

It has previously been shown that Notch, Delta and Lunatic Fringe are expressed together in the leading edge of the tail bud of the Xenopus embryo prior to outgrowth (Beck and Slack, 1998). It has also been shown that ectopic expression of a constitutive form of Notch, Notch-ICD, will provoke ectopic tail formation (Beck and Slack, 1999). Here we show that inhibition of Notch activity in vivo prevents outgrowth of the tail bud. This is achieved using inhibitors of the protease that carries out the ligand-induced intramembranous cleavage of Notch. Other protease inhibitors that do not inhibit Notch cleavage do not affect tail outgrowth.