This project will focus on the molecular etiology of interstitial cystitis (IC), an ill-defined and excruciatingly painful bladder disease affecting primarily women. Our strategy involves the use of the promoter region of a bladder-specific gene to drive the expression of various molecules in the urothelia of transgenic mice, and to assess whether any of these molecules can induce parts of, or the entire, IC process. Using this approach, we will test specifically three current hypotheses, i.e., that leaky urothelium, mastocytosis or nerve abnormality may cause IC. In our studies, we will focus on the genes that encode a group of integral membrane proteins, called uroplakins (UPs), that are the major differentiation products of mammalian urothelium. Molecular cloning data established the existence of four uroplakins (Ia, Ib, II and III). Since the uroplakin genes appear to be expressed in a bladder-specific manner, their promoters should be ideal for directing test molecules to be expressed in the bladders of transgenic mice. To establish such a system, we will perform several experiments. First, we will study the spatiotemporal regulation of the four uroplakin genes in mice to ensure that the promoter that we will use for transgenic studies is truly bladder-specific. Second, we will characterize our existing mouse UPIa, II and III genomic clones, and determine whether the 5'-upstream regulatory sequences of any of these genes can serve as a bladder-specific promoter in transgenic mice. Third, we will perturb the apical urothelial plaques, which are known to be a part of urothelial permeability barrier, by using a bladder- specific uroplakin promoter to drive the expression of a defective uroplakin in the urothelium of a transgenic mouse -- to see whether this will compromise the permeability barrier and cause IC. Fourth, we will drive the urothelial expression of mast cell growth factor to induce mastocytosis and degranulation. Finally, to perturb bladder innervation we will over-express nerve growth factor in urothelium. Therefore, using this approach, we will generate a panel of transgenic mice each carrying specific alterations in its bladder -- but all with clear-cut molecular etiology. These animals will provide unique opportunities for studying many important problems related to bladder structure and function including the permeability barrier, inflammation and innervation, and will allow us to assess the possible involvement of these processes in interstitial cystitis.
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