Figure 1.

Application of a single trapped Fn-coated bead triggers polarization of adhesion-naive 3T3 cells. (A) Still images from differential interference contrast in a time-lapse movie (see Movie S1 in the Supporting Material) of single oscillating 3T3 cells plated on Pll-PEG coated glass coverslips; and still transmitted-light images from a time-lapse movie (see Movie S2) of single cells plated on Pll-PEG coated glass coverslips and with Pll-coated (middle) and Fn-coated (bottom) bead applied on the cell cortex. (B) Schematics defining the two measured parameters: shape anisotropy of a cell fitted with an ellipse defined by major b and minor a axes, and cell orientation corresponding to the angle α (in degrees) between the major axis b and the cell geometrical center (GC)-bead axis (brown line). (C) Percentage of shape anisotropy variations for each assay conditions. The variation is calculated with respect to the initial cell shape at time 0. The number of analyzed cells is indicated on the histogram. (D) Rose diagrams indicate the proportion of cells for each angular sector under different assay conditions. (Red) Median angle. Statistical differences are indicated (Dunnett’s test: ^∗, P < 1; ^∗∗, P < 0.4; ^∗∗∗, P < 0.006; ^∗∗∗∗, P < 0.0001). All scale bars, 5 μm. Times shown in seconds (A, upper row) and minutes (A, middle and lower row).