REGULATION OF EPIDERMAL INDUCTION BY BMP2 AND BMP7 SIGNALING

The specification of neural fate in Xenopus embryos has been shown to be under regulation by negative factors. The secreted protein bone mor phogenetic protein-4 (BMP4) has been identified as one of these factor s: in the early gastrula ectoderm, BMP4 can both inhibit neural fate a nd induce epidermis. In this study, we show that two other Xenopus BMP genes, BMP2 and BMP7, are endowed with the same types of activities. First, we show that expression of a dominant negative form of the BMP2 ligand, which blocks normal processing of the wild-type ligand, cause s neuralization of Xenopus ectoderm. Second, we have isolated the Xeno pus BMP2/7 receptor (XALK2) and generated a constitutively active muta nt that signals in a ligand-independent manlier. We show that signals from the activated BMP2/7 receptor also inhibit neuralization and indu ce epidermis in dissociated ectoderm cells. Consistent with both findi ngs we show that secreted BMP2 and BMP7 ligands can also mediate neura l inhibition and epidermal induction. These results suggest that both BMP2 and BMP7 may be involved independently or together with BMP4 in t he inhibition of the neural fate and the onset of the epidermal induct ion pathway in vivo. This further supports the idea that epidermal ind uction is due to the effects of multiple signals from heterogeneous BM P genes. (C) 1997 Academic Press.