Fig. 4. (A) Transfection of C7 with claudin-2 cDNA. Western blots detecting claudin-1 and claudin-2 in MDCK clones stably transfected with claudin-2 cDNA (C7-cld-2), compared with control (transfected with vector alone, C7-vec). (B) Decrease of R^epi by introducing claudin-2 into MDCK-C7 cells. (C) Permeability of 4K FITC dextran in C7-vec and C7-cld-2. (D,E) Comparison of claudin-2 expression in the different clones using a confocal microscope. Detection of claudin-2 (red) and occludin (green) in C7-vec (D) and in C7-cld-2 (E). Transfectants did not show detectable changes in claudin-1 and -3 (not shown). F) Z-scans of C7-cld-2 detecting occludin (green) and claudin-2 (red). Scans as shown on the right or above the top views were performed in 200 nm steps over a range of 10 µm. A tight junctional colocalization of claudin-2 with occludin is observed.