Using a transgenic animal line constitutively expressing ret in the ureter, it was possible to rescue branching morphogenesis in retinoid receptor mutants indicating that one critical function of retinoids is maintaining ret expression in the embryonic kidney. Dr. Mendelsohn's lab is using a similar approach to identify molecules important for ureter differentiation. Using transgenic animals expressing fluorescent proteins in distinct ureter cell types, it has been possible to systematically examine ureter development in vivo and in vitro, and to identify cell types important for retinoid-signaling. The results of these experiments indicate that the hydronephrosis and mega-ureter in retinoid knockout animals is likely to result from impaired smooth muscle differentiation of the ureter coat. Multiple abnormalities at various stages of organogenesis in RAR double mutants.
Stromal cells mediate retinoid-dependent functions essential for renal development.