VENTRAL MESODERM INDUCTION AND PATTERNING BY BONE MORPHOGENETIC PROTEIN HETERODIMERS IN XENOPUS EMBRYOS

Bone morphogenetic proteins (BMPs) perform diverse functions in verteb rate development. Here we demonstrate that the heterodimeric BMP-4/7 p rotein directly induces ventral mesoderm and blood in Xenopus animal c aps, and BMP-2/7 heterodimers may function similarly. We also provide indirect evidence that BMP heterodimers function in embryos, using ass ays with dominant-negative BMP ligands. Homodimeric BMP-2 and BMP-4 pr oteins do not induce mesoderm, but they ventralize mesoderm induction by activin. In contrast, BMP-7 protein interferes with mesoderm induct ion by activin, but BMP-7 stimulates ventral mesoderm induction by the heterodimer, BMP-4/7. This novel property of BMP-7 distinguishes it f rom other BMPs. BMP-7 may therefore function in early embryogenesis to antagonize activin signals and potentiate BMP signals. We propose tha t BMP heterodimers convey signals for ventral mesoderm induction and p atterning in Xenopus development. (C) 1998 Elsevier Science Ireland Lt d. All rights reserved.