Range and distribution of forces induced by myosin motors in the disordered actin network*

Mechanical forces generated by myosin motors in actin networks is responsible for a variety of processes such as cell shape changes and locomotion. These forces may be transmitted through the disordered elastic crosslinked actin network, potentially mediating mechanical interactions between distant myosin motors. We model myosin motors as contractile force dipoles embedded in a bond-diluted triangular lattice, representing the actin network, with bonds that resist bending and stretching. These model fiber networks show a transition from stretching to bending dominated regimes with increasing bond dilution. We quantify the range of force transmission and mechanical heterogeneity of these networks in response to force dipoles. Force propagates over longer ranges in stretching-dominated networks than in the dilute bending regime. Increasing the bending stiffness however restores long-range force transmission even in the dilute regime. By quantifying the decay of mean strain energy with distance, we show that a little bond dilution enhances range of force transmission relative to the ordered lattice. We also investigate the differences between tensile and compressive force propagation by analysing clusters comprising nodes connected to highly stretched or compressed bonds.