Figure 1.

Pattern of expression of claudin (CLDN) proteins along the human renal tubule and collecting duct. The figure is a summary of data published in References [26,27,28,29] (the expression pattern in rodent kidney has recently been summarized in several reviews [2,30,31]). Question mark means that direct evidence of the expression of the considered claudin in human is not available but that indirect evidence suggests that it should be expressed there. Brackets mean that the expression is low. The numbers above the various segments are: 1, proximal convoluted and straight tubule; 2, descending thin limb; 3, ascending thin limb; 4, distal straight tubule (thick ascending limb); 5, distal convoluted tubule; 6, cortical and outer medullary collecting duct. Colors illustrate the fact that composition and/or volume of tubular fluid changes along the renal tubule. Readers interested in mRNA expression pattern can visit https://hpcwebapps.cit.nih.gov/ESBL/Database/NephronRNAseq/All_transcripts.html.