Increased actin polymerization in ERM- or LOK/SLK-knockout cells leads to junctional defects. (A) Jeg-3 cells treated with DMSO, 500 nM jasplakinolide, or 100 ng/ml latrunculin B for 30 min before immunostaining with ZO-1 and actin. Yellow boxes correspond with magnified images. Magenta arrowheads point to actin gaps at junctions, while blue arrowheads represent actin present at cell junctions. Scale bars, 10 µm. (B) Quantification of tortuosity between tight junction markers as described in Fig. 3. Jasplakinolide (Jas) treatment increases tortuosity values, while latrunculin B (LatB) rescues tortuosity to wild-type levels. n ≥ 10 cells per condition. Lines represent mean ± SEM. (C) Comparison of actin levels between apical and basolateral regions after treatment with drugs as visualized in A. n ≥ 21 cells per condition. Bars show mean ± SEM. P values were calculated with Welch’s t test (*, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001).