Fig. 3: Negative curvature induces anterograde flow of actin.

a, Representative 3D live SIM image showing radial fibre (RF) and transverse fibre (TF) organization at negative curvature. Colour-coded for cell height (0 μm being the surface of the coverslip). The magenta dashed line marks the edge of the fibronectin pattern. Scale bar, 5 μm. b, Kymograph along the white dashed line in a, showing anterograde flow of TFs and merging of TFs with actin cable at the edge. Horizontal scale bar, 1 μm; vertical scale bar, 10 min. c, Radial flow velocity of myosin flow at different substrate curvatures on patterned surfaces. Error bars indicate s.e.m. n = 10, 6, 8, 9, 13, 13, 9, 9, 6, 6, 9, 6, 6, 8, 10 for curvature values −0.200, −0.100, −0.0667, −0.0500, −0.0333, −0.0200, −0.0100, 0, 0.0100, 0.0200, 0.0333, 0.0500, 0.0667, 0.100, 0.200, respectively. A curvature value of 0 corresponds to regions of flat edges. Individual data points are shown as black dots, with red dots showing outliers. The red line shows the model fit to the negative curvature data (see text and Supplementary Information for details). d–f, Photoconversion of mEos2-actin on RF shows anterograde flow. d, mEos2-actin before photoconversion (green), the edge of the fibronectin pattern is marked by the white dashed line. e, mEos2-actin after photoconversion of a segment (magenta) on RF with a 405 nm laser. f, Kymograph along a photoconverted RF within the yellow box shown in d; the white dashed lines mark the edge of the fibronectin pattern. For d and e, scale bars, 2 μm; for f, horizontal scale bar, 1 μm, vertical scale bar, 1 min. g, Velocity vector map from fluorescent speckle microscopy (FSM) measurement. The magenta dashed line in g and h marks the edge of the fibronectin pattern. Scale bar, 5 μm. h, Heat map showing the magnitude of the actin flow velocity component along the radial direction in a representative cell at negative curvature measured by FSM. Scale bar, 5 μm. i, Decreasing flow profile of the radial velocity at negative curvature measured by FSM (blue, n = 3) and TF tracking (green, n = 5). Error bars indicate s.e.m. The red line shows the fitted model (see Supplementary Information for details).