Since the expression of several proximal tubule-specific genes is decreased in adult Vhl-deficient mice, but the Ksp1.3-Cre transgene drives gene deletion in only a small percentage of proximal tubular cells, it is likely that this observation reflects progressive kidney damage and nephron loss due to persistent hydronephrosis rather than representing the primary cause of the phenotype. The gene discussed is VHL; the disease is hydronephrosis.