Interference with brachyury function inhibits convergent extension, causesapoptosis, and reveals separate requirements in the FGF and activin signalling pathways

Brachyury plays a key role in mesoderm formation during vertebrate developm ent. Absence of the gene results in loss of posterior mesoderm and failure of the notochord to differentiate, while misexpression of Brachyury in the prospective ectoderm of Xenopus results in ectopic mesoderm formation. Brac hyury is therefore both necessary and sufficient for posterior mesoderm for mation. Here we present a detailed cellular and molecular analysis of the c onsequences of inhibiting Brachyury function during Xenopus development. Ou r results show that Brachyury is required for the convergent extension move ments of gastrulation, for mesoderm differentiation in response to FGF, and for the survival of posterior mesodermal cells in both Xenopus and mouse. (C) 1999 Academic Press.