Transforming growth factor-β superfamily members: Roles in branching morphogenesis in the kidney

The process of nephrogenesis and the number of nephrons formed during kidney development are both highly dependent upon ureteric branching morphogenesis. Abnormalities in branching and growth of the ureter have been implicated in a range of urogenital/renal pathologies including cystic renal disease and some forms of renal agenesis. The issue of how the branching of the ureter is regulated is therefore an important one. There is a growing list of candidate molecules (growth factors, oncogenes, transcription factors and extracellular matrix components) which have been directly or indirectly implicated in the regulation of ureteric branching. Among these, members of the transforming growth factor-β (TGF-β) superfamily are well represented. This review summarizes our knowledge of the roles of TGF-β superfamily members in ureteric branching morphogenesis.