Regulation of tight junction protein expression in the kidney. The protein levels of CLDN4 and 16 were measured by Western blotting. The differential expression of CLDN4 and 16 in each type of normal conditioned mice were compared (A). The impact of calcium deficiency on CLDN4, and CLDN16 protein expression in WT, CaBP-9 k KO, -28 k KO, and DKO animal was evaluated (B). Differential CLDN4 and CLDN16 protein expression was examined in all strains of mice that were calcium/vitamin D-deficient (C). β-actin was used as the control. The values represent means ± SD of three separate experiments. * indicates *P < 0.05 vs WT of each diet.