Abstract
Mutations in GLI3, a component of the Sonic Hedgehog (Shh) signaling pathway, cause a variety of human developmental syndromes. In this issue of the JCI, Cain and colleagues show that tightly regulated GLI3 repressor activity is essential for Shh-dependent differentiation of upper urinary tract pacemaker cells and the efficient flow of urine from the kidney to the bladder. These results link defective pacemaker cell differentiation with hydronephrosis and provide a cellular basis for one of the abnormal renal defects observed in humans with the GLI3-linked disease Pallister-Hall syndrome.