BMP-4 ACTS AS A MORPHOGEN IN DORSOVENTRAL MESODERM PATTERNING IN XENOPUS

The marginal zone is a ring of tissue that gives rise to a characteris tic dorsoventral pattern of mesoderm in amphibian embryos. Bmp-4 is th ought to play an important role in specifying ventral mesodermal fate. Here we show (1) that different doses of Bmp-4 are sufficient to patt ern four distinct mesodermal cell types and to pattern gene expression in the early gastrula marginal zone into three domains, (2) that ther e is a graded requirement for a Bmp signal in mesodermal patterning, a nd (3) that Bmp-4 has long-range activity which can become graded in t he marginal zone by the antagonizing action of noggin. The results arg ue that Bmp-4 acts as a morphogen in dorsoventral patterning of mesode rm.