Spectrin determines junctional actomyosin network structure and stability. (a) Immunofluorescence analysis for αII-spectrin, F-actin, and non-muscle myosin heavy chain IIa (myosin-IIa, Myosin-9) (48 h high Ca²⁺) in Ctr and αII-spectrin–deficient (KO) cells. Single channels corresponding to Fig. 4 d. (b) Immunofluorescence analysis for αII-spectrin and F-actin (48 h high Ca²⁺) upon αII-spectrin knockdown and treatment with either DMSO or low-dose blebbistatin (5 µM). Representative images of n = 3 biological replicates each. Single channel gray scale and merged channels corresponding to Fig. 4 e. (c) Junctional laser ablation in apical keratinocytes with (48 h Ca²⁺) or without (40 h Ca²⁺) a cortical F-actin lattice. Time points after ablation (yellow line) are shown as indicated. (d) Quantification of the increase in vertex (dashed line) distance upon ablation. Lines: mean ± SD recoil of 11 ablations (no lattice) and 20 ablations (with lattice) from n = 3 biological replicates each. (e) Sequential ablation: short junctional ablation followed by a longer 17 µm ablation across the same junction. The latter one ablating the cortex connected to the ablated junction. (f) Quantification of vertex distance increase of sequential ablations. Line: mean ± SD recoil of seven sequential ablation from n = 2 biological replicates. (g) Cortical laser ablation showing straightening of curved cell–cell boarders (yellow line) after linear ablation of the lattice.