A dense actomyosin network forms at the apical surface of ERM- and LOK/SLK-knockout cells. (A) Representative SIM reconstructions of the apical surface of Jeg-3 cells labeled with anti–myo-IIB, phalloidin, and DAPI. Scale bars, 5 µm. (B) Line scans of the actin intensity across the center of the apical surface of each cell type shown as dotted yellow lines in A. (C) Example stacked SIM Z-slices from the middle of Ezr^−/−Rdx^−/− cells labeled with anti–myo-IIB and Alexa Fluor 647 phalloidin. Zoom-in highlighting the attachment of the apical contractile fibers to the cell–cell junctions. Scale bars, 5 µm; inset, 2 µm. (D) Averaged force indentation curves for wild-type Jeg-3 (blue), Ezr^−/− Rdx^−/− (green), and LOK^−/− SLK^−/− (magenta); semitransparent area around each line represents the SEM of the data. A steeper curve indicates a stiffer cell. (E) Young’s modulus stiffness parameters. Black line indicates each condition’s mean value (wild type, n = 356; Ezr^−/− Rdx^−/−, n = 304; LOK^−/− SLK^−/−, n = 431). Both knockout conditions were significantly stiffer than wild-type cells (***, P ≤ 0.0001, Kolmogorov-Smirnov test). AU, arbitrary units.