Figure 3.

Single-cell actin cytoskeleton polarizes to match the stiffness gradients of the underlying matrix. Shown are typical and average cell actin substructure for X, I, and square fibronectin shapes with varying stiffness stimuli from the substrate. Black rectangles near orange schematics on the left represent stiff regions. Interior stress fibers preferentially orient towards contracted regions, initiating at regions of high stiffness, and terminating at regions of low stiffness. Of particular note are stress fibers in the single stiff adhesion case, which preferentially orient diagonally and terminate across the sample, and may be the source of the increased contraction of distal adhesions for this case. Scale bar is 5 μm.