Figure 1.

Schematic representation of the expression pattern of the Wnt family members in the embryonic kidney. The Wnt-6, -7b, -9b and -11 genes are expressed in the epithelial ureteric bud that will form the future collecting duct of the kidney. Of these, Wnt-9b serves as a signal mediating reciprocal inductive signalling from the ureteric bud to the kidney mesenchyme to trigger nephrogenesis, while Wnt-11 controls ureteric bud branching morphogenesis to create the collecting duct tree. Wnt-4 is the only Wnt family member that has so far been found to be expressed in the pretubular mesenchymal cells. Wnt-4 is essential for controlling nephrogenesis. Wnt-2b gene is transiently expressed in the perinephric mesenchyme and may control ureteric branching from the mesenchymal periphery.⁵