NPPA and Calcium oxalate nephrolithiasis: For example, mutations in the vacuolar-type H+-ATPase (V-ATPase) subunit genes ATP6V1B1 and ATP6V0A4 in humans have been identified in recurrent calcium oxalate kidney stones (78) and knockdown of the fly orthologs, Vha55 and Vha100-2, using Uro-Gal4 led to increased formation of calcium oxalate stones in Malpighian tubules (79).