Differential Expression Patterns of Claudins, Tight Junction Membrane Proteins, in Mouse Nephron Segments

TLDR

Polyclonal antibodies for claudin‑7 and ‑12 were unavailable, and the study discusses segment‑specific claudin expression patterns in relation to nephron tight junction physiology. The study aimed to map claudin‑1 to ‑16 expression in mouse kidneys and to determine the segment‑specific distribution of claudins 1, 2, 3, 4, 8, 10, 11, and 16 using immunofluorescence microscopy. Expression was assessed by Northern blotting for claudins 1–16, and immunofluorescence microscopy with segment‑specific marker antibodies identified nephron segment localization. Only claudins 6, 9, 13, and 14 were undetectable, claudin‑5 and ‑15 were endothelial‑specific, and the remaining claudins exhibited highly segment‑specific expression patterns across the nephron.

Abstract

ABSTRACT. As the first step in understanding the physiologic functions of claudins (tight junction integral membrane proteins) in nephrons, the expression of claudin-1 to -16 in mouse kidneys was examined by Northern blotting. Among these claudins, only claudin-6, -9, -13, and -14 were not detectable. Claudin-5 and -15 were detected only in endothelial cells. Polyclonal antibodies specific for claudin-7 and -12 were not available. Therefore, the distributions of claudin-1, -2, -3, -4, -8, -10, -11, and -16 in nephron segments were examined with immunofluorescence microscopy. For identification of individual segments, antibodies specific for segment markers were used. Immunofluorescence microscopic analyses of serial frozen sections of mouse kidneys with polyclonal antibodies for claudins and segment markers revealed that claudins demonstrated very complicated, segment-specific, expression patterns in nephrons, i.e., claudin-1 and -2 in Bowman's capsule, claudin-2, -10, and -11 in the proximal tubule, claudin-2 in the thin descending limb of Henle, claudin-3, -4, and -8 in the thin ascending limb of Henle, claudin-3, -10, -11, and -16 in the thick ascending limb of Henle, claudin-3 and -8 in the distal tubule, and claudin-3, -4, and -8 in the collecting duct. These segment-specific expression patterns of claudins are discussed, with special reference to the physiologic functions of tight junctions in nephrons.