Expression of TJ proteins in the stably transfected MDCK C11 cells. A) Claudin-1, claudin-2, ZO-1 and ZO-2 expression is not affected by the stable transfection of the indicated occludin-FLAG3 constructs as detected by Western blotting. β-Actin was used as a loading control. Analysis of two different clones for each construct is shown. B) Transfection of the indicated occludin constructs does not affect cell proliferation as investigated by a XTT-assay. The graph summarizes the results of 4 experiments including two clones of each construct (mean values +/− SEM).