Figure 2.

Nesprin tension is sensitive to extracellular compression, stretch, and cell packing. (A) Top: Schematics of an event of cell migration through a narrow constriction. Bottom: Direct fluorescence image and FRET index map from the dotted box above with boundaries between the region within the constriction and that outside it. (B) FRET index of the CB construct and the CH mutant inside and outside constrictions, in MDCK (left; n = 24 CB, 40 CH mutant) and NIH 3T3 (right; n = 48 CB out, 38 CH mutant) cells; three replicates. (C) Top: Schematics of the cell-stretching experiment. Cells are plated on collagen stripes printed on a transparent, elastomeric sheet stretched in the direction of the adhesive stripes. Bottom: Direct fluorescence image and FRET index map from the dotted box above. (D) FRET index change upon stretching of the CB construct and the CH mutant as a function cell and nucleus strains (n = 6 CB, 5 CH mutant). Solid lines are linear fits; three replicates. (E) MDCK cells expressing the CB construct plated at 5 × 10² cells/mm² (1×) and 5 × 10³ cells/mm² (10×). Top: Fluorescence; bottom: FRET index map. (F) FRET index of the CB construct and the CH mutant at 1× and 10× densities in MDCK (left; n = 97 CB 1×, 82 CB 10×, 45 CH mutant 1×, 61 CH mutant 10×) and NIH 3T3 (right; n = 88 CB 1×, 120 CB 1×, 89 CH mutant 1×, 152 CH mutant 10×) cells; three replicates. Scale bar = 5 µm. Mean ± SEM. Two-tailed Mann-Whitney tests. *, P < 0.05; **, P < 0.01; ****, P < 0.0001. The color code follows that of Fig. 1.