Geometric Effects Position Renal Vesicles During Kidney Development

During kidney development, reciprocal signalling between the epithelium and the mesenchyme coordinates nephrogenesis with branching morphogenesis of the collecting ducts. The mechanism that positions the renal vesicles, and thus the nephrons, relative to the branching ureteric buds has remained elusive. By combining computational modelling and experiments, we show that geometric effects concentrate the key regulator, WNT9b, at the junctions between parent and daughter branches where renal vesicles emerge, despite its uniform expression in the ureteric epithelium. This curvature effect might be a general paradigm to create non-uniform signalling in development.