BMP-4 affects the differentiation of metanephric mesenchyme and reveals anearly anterior-posterior axis of the embryonic kidney

Bone morphogenetic protein-4 (BMP-4), a member of the transforming growth f actor-beta (TGF-beta) family, regulates several developmental processes dur ing animal development. We have now studied the effects of BMP-4 in the met anephric kidney differentiation by using organ culture technique. Human rec ombinant BMP-4 diminishes the number of ureteric branches and changes the b ranching pat term. Our data suggest that BMP-4 affects the ureteric branchi ng indirectly via interfering with the differentiation of the nephrogenic m esenchyme. The clear positional preference of the defects to posterior mese nchyme might reflect sue early anterior-posterior patterning of the metanep hric mesenchyme. The smooth muscle alpha-actin expressing cell population a round the ureteric stalk, highly expressing Bmp-4 mRNA, is also expanded in kidneys treated with BMP-B. Thus, BMP-4 may be a physiological regulator o f the development of the periureteric smooth muscle layer and ureteric elon gation. (C) 2000 Wiley-Liss, Inc.