NEURAL INDUCTION IN XENOPUS-LAEVIS - EVIDENCE FOR THE DEFAULT MODEL

At gastrulation, vertebrate ectoderm is competent to differentiate int o either neural tissue or epidermis. Several soluble factors that can neuralize ectoderm in explant cultures have been isolated. Alternative ly, neuralization can be achieved by dissociating the cells of the bla stula ectoderm. These various treatments appear to neuralize by blocki ng or diluting out the action of an epidermal-inducing factor. Recent results demonstrate that bone morphogenetic protein 4 (BMP-4), a membe r of the transforming growth factor beta (TGF-beta) ligand superfamily , is a potent neural inhibitor and epidermal inducer and may represent the endogenous epidermal-inducing factor.