Figure 1. Characterization of claudin-2–KO mice.

(A) Quantification of whole-kidney mRNA levels of claudin-2 relative to β-actin in claudin-2 hemizygous KO (–/Y), heterozygous (+/–), and WT (+/Y) mice (n = 6 per group). (B) Western blot of whole-kidney lysates probed with mouse anti–claudin-2 antibody showing a band at the expected size for claudin-2. Lower panel shows an immunoblot for β-actin as a loading control. (C) Immunolocalization of claudin-2. Frozen sections of mouse kidney were double stained with claudin-2 antibody (green) and antibody against ZO-1 (red), a tight-junction marker. Note the localization of claudin-2 in WT kidney to the tight junctions of the PTs (P) but not to the distal tubules (D), as well as the faint basolateral staining. In heterozygous mice, PT staining was heterogeneous, with claudin-2 absent from some cells (arrows) but present in others as a result of lyonization.