Vacuolar ATPase regulates ureteric bud branching morphogenesis during kidney development

Our studies have established that ureteric bud (UB) prorenin receptor (PRR/ATP6AP2), an accessory subunit of the vacuolar H⁺-ATPase (V-ATPase), is critical for normal UB branching. Here, we tested the hypothesis that V-ATPase activity, acidosis, and UB cell intracellular pH (pH_i) regulate UB branching morphogenesis during kidney development. The effect of specific V-ATPase inhibitor Bafilomycin, hypercapnic (high CO₂), and metabolic (low [Formula: see text]) acidosis on UB branching was determined in whole intact E12.5 <i>Hoxb7</i>^GFP+ mouse kidneys grown ex vivo by time-lapse photomicroscopy. The effect of Bafilomycin on UB cell migration in vitro was examined using a transwell migration assay (<i>n</i> = 3 wells/treatment group). The presence of V-ATPase and Na⁺-H⁺ exchanger (NHE) activity in UB cells was investigated by measurements of intracellular pH (pH_i). The ability of UB cells to regulate cell pH_i in vitro was determined by measurements of Na-dependent and Na-independent pH_i recovery from acid loads. The mean number of UB cells that migrated through the membrane after 24-h culture was reduced with Bafilomycin compared with control. Treatment with Bafilomycin, hypercapnic acidosis (induced by high CO₂), or metabolic acidosis (induced by low [Formula: see text] concentration) in the culture media caused a marked reduction in the number of UB tips compared with control. We conclude that intact V-ATPase activity is essential for normal UB branching during kidney development. V-ATPase-dependent reduction in UB cell pH_i is likely a cause of decreasing UB branching by inhibiting directional movements of UB cells.<b>NEW & NOTEWORTHY</b> Disruption of normal kidney development results in a spectrum of congenital anomalies of the kidney and urinary tract (CAKUT), the major cause of end-stage kidney disease in children. We demonstrate that acidosis, kidney cell intracellular pH, and activity of V-ATPase pump are essential for normal kidney development.