Localization and putative function of claudin proteins in mammalian kidney. Localization data were summarized from the following studies: claudins-1, -3,- 4, and -11 (59), claudin-2 (28), claudin-6 (1, 6, 118), claudins-7 and -8 (68), claudin-9 (1), claudin-10 (108), claudin-14 (12), claudin-16 (61, 91), and claudin-19 (6, 61). 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 Macula densa claudin expression is from our own unpublished results.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 (59) and so are not shown. Claudins-12, -18, and -20 to -24 have not yet been examined. Claudins are color coded according to their putative charge selectivity and permeability. Figure modified from Angelow S, Yu AS. Curr Opin Nephrol Hypertens 16: 459–464, 2007 (copyright Lippincott, Williams & Wilkins, 2007).