Fig. 2: Mechanical anisotropy of the cell and of the chromatin induced by different force modes.

a A representative image of adherent and elongated CHO (Chinese hamster ovary) cell with the GFP labeled chromatin domain (green dots; see the enlarged image within the dashed white lines). A 4-μm RGD-coated ferromagnetic bead (the solid black ball) was attached to the cell surface via integrins. Theta represents the angle of bead rolling direction with respect to the long axis of the cell (this notation applies to all cells in all figures). The bead and GFP spots in the white box were enlarged and shown on the right. Scale bar, 3 μm. The in-plane (X–Y plane) rotation has a direction along the Z-axis and the two out-of-plane rotations have directions along the X- and Y-axes, using the right-hand rule (see Fig. 1). b Peak 2D displacements of the center of the magnetic bead in the X–Y plane at stress angles 0° or 90° for the out-of-plane stress mode or the peak bead twisting angles for the in-plane stress mode in the same cell. In all stress modes, the peak amplitudes of the sinusoidal magnetic fields were maintained at 15 Pa and 0.3 Hz. Each triangle or dot represents one cell. c Cell stiffness computed with different stress modes. P = 0.0079 between 90° and in-plane stress modes; P < 0.001 between 0° and 90°, 0° and in-plane stress modes. d Fluorescent image of the three GFP spots in the same chromatin of a representative cell. Scale bar, 1 μm. e Normalized mean squared displacement (MSD) of all individual GFP spots when the stress (15 Pa at 0.3 Hz) was applied at 0° or 90° or in-plane mode. No stress data represent the spontaneous GFR spots movements in the absence of force application. f Chromatin deformation (i.e., changes of distances between any two GFP spots in the same chromatin domain) depends on stress modes. P < 0.001 between each different stress modes. g Tensile strains of the chromatin were computed from chromatin deformation²¹. P = 0.0055 between 0° and in-plane stress modes; P = 0.0017 between in-plane and 90° stress modes; P < 0.001 between 0° and 90° stress modes. h Shear strains were computed from the same chromatin deformation. P = 0.00701 between 0° and in-plane stress modes; P < 0.001 between in-plane and 90° and 0° and 90° stress modes. For b, c, and e–h, mean ± s.e.m.; n = 39 cells, 29 independent experiments; **P < 0.01; ***P < 0.001. P values were calculated and corrected using two-tailed Student’s t-test and Bonferroni correction. Source data are provided as a Source data file.