UPK3A (UPK3, Uroplakin 3) is a member of the uroplakin family, a group of transmembrane proteins that form complexes on the surface of the transitional epithelium of the bladder. UPK3 is an integral subunit of the urothelial plaque that contributes to the permeability barrier function of urothelium. Ablation of the gene can cause primary vesicoureteral reflux. Mutations in UPK3 are also associated with renal dysplasia. References: Kidney Int 2009 75(11):1153; J Cell Biol 2000 15(5):961.