Localization of claudin proteins in mammalian kidney. Localization data were summarized from the following studies: claudins 1, 3, 4, and 11 [46], claudin-2 [19], claudin-6 [1, 95], claudins 7 and 8 [55], claudin-9 [1], claudin-10 [85], claudin-14 [7], claudin-16 [50, 78, 91] and claudin-19 [5, 50, 54]). Tubule expression of claudins 6 and 9 are only found in neonatal kidney [1]. Many of these claudins have not been rigorously examined in all nephron segments so the data shown are not comprehensive. Macula densa claudin expression is from our own unpublished results. Claudins 5 and 15 are confined to endothelial cells of the vasculature and glomeruli [46] and so are not shown. Claudins 12, 18 and 20–24 have not yet been examined. Figure modified from [4] (copyright Lippincott, Williams & Wilkins, 2007).