MASPs regulate the epithelial barrier function. (A) RT-PCR of MASP-qKO cells. Reaction without reverse transcriptase (RT−) served as a negative control. (B) Immunoblotting of MASP-qKO cells using rabbit anti-EpCAM mAb and other antibodies. Black and gray arrowheads indicate full-length and cleaved EpCAM, respectively. Arrows and asterisks indicate specific and non-specific bands, respectively. (C and D) Staining of MASP-qKO cells using mouse anti-EPCAM mAb (C) or rabbit anti–claudin-7 pAb (D; red) together with rat anti–ZO-1 mAb (green) and DAPI (blue). Scale bars, 10 µm. (E) FFEM of MASP-qKO cells. Scale bar, 200 nm. (F) Quantification of the frequency of TJ strand branching points in the MASP-qKO cells. Ctrl data is the same one used in Fig. 2 H. Total length of TJ strands examined was 111 µm. Error bars indicate 95% confidence intervals. *, P < 0.05 (exact Poisson test). (G) Distribution of horizontal TJ strand number in the MASP-qKO cells. Blue lines indicate mean ± SD. Ctrl data is the same one used in Fig. 2 I. n = 400 (MASP-qKO#1). ***, P < 0.001 (two-tailed Welch’s t test). (H) Predicted TER values using simplified TJ strand network models based on the quantification data of TJ strand network complexity in the MASP-qKO cells. (I) TER measurements of MASP-qKO cells. n = 5. ***, P < 0.001 (two-tailed Welch’s t test with Bonferroni’s correction). (J) Effects of trypsin treatment form the apical side of the MASP-qKO cells and EpCAM-KO cells. n = 5. *, P < 0.05; ***, P < 0.001 (two-tailed paired t test). (K) FFEM images of the Ctrl cells (top) and MASP-qKO cells (bottom) treated with trypsin from the apical side. Scale bars, 200 nm. Source data are available for this figure: SourceData F5.