Figure 3: Stress fibers direct contractile flow. | Nature Communications

Figure 3: Stress fibers direct contractile flow.

From: Optogenetic control of RhoA reveals zyxin-mediated elasticity of stress fibres

Figure 3

(a) Fluorescence time series of a cell expressing mApple-MLC shown prior and after two separate periods of activation (orange boxes). (b) Flow fields of myosin calculated from the images in panel a. Flow is always directed along the direction of the stress fibers. (c) A two-dimensional model of the cell was created using a triangular mesh of viscoelastic cables (k,η) connected at vertices viscously coupled (γ) to the environment. Stress fibres (blue line) consisting of contractile (σm), viscous (ηSF) and elastic elements (kSF) were embedded in the network. Using a simplified rectangular cell with this network, local RhoA activation could be simulated by activating force dipoles in network links in a region in the centre of the cell. (d) To calibrate the 2D discrete model, the average flow (white box in panel c), was measured and compared to the 1D continuum model presented above. (e,f) The 2D discrete model was used to explore two contractile scenarios: (e) contractile stress fibres (blue) embedded in a contractile mesh (grey); and (f) contractile stress fibres embedded in a non-contractile background. If both the stress fibres and mesh are contractile, a transverse contraction pinches together the stress fibres. If only the stress fibres contract, the flow profile is restricted to the orientation of the fibres, mimicking the experimental results. Scale bar is 10 μm.

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