REGULATION OF NEURAL INDUCTION BY THE CHD AND BMP-4 ANTAGONISTIC PATTERNING SIGNALS IN XENOPUS

IN Drosophila the amount of neurogenic ectoderm, from which the centra l nervous system (CNS) derives, is regulated by a dorsal-ventral syste m of positional information in which two secreted molecules of antagon istic functions, decapentaplegic (dpp) and short-gastrulation (sog), p lay fundamental roles(1-4). The vertebrate homologue of dpp is either bmp-4 or bmp-2 (ref. 5), and the homologue of sog is chd(4,6,7) (s-cho rdin). In Xenopus the CNS is induced by signals emanating from the org anizer(8), and two proteins secreted by the organizer, noggin(9) and f ollistatin(10), have been shown to induce neural tissue in animal-cap assays. Here we report that Chd, another organizer-specific secreted f actor(6), has neuralizing activity and that this activity can be antag onized by Bmp-4. Inhibition of the function of the endogenous Bmp-4 pr esent in the animal cap(1)1 also leads to neural differentiation. We s uggest that conserved molecular mechanisms involving chd/sog and bmp-4 /dpp gene products pattern the ectoderm in Xenopus and in Drosophila.