The molecular signals that regulate growth and branching of the ureteric bud during
formation of the renal collecting system are largely undefined. Members of the bone
morphogenetic protein (BMP) family signal through the type I BMP receptor ALK3 to inhibit
ureteric bud and collecting duct cell morphogenesis in vitro. We investigated the function of
the BMP signaling pathway in vivo by generating a murine model of ALK3 deficiency
restricted to the ureteric bud lineage (Alk3 UB−/− mice). At the onset of branching …