A model for contractile stress fibers embedded in bulk actomyosin networks

Contractile cytoskeletal structures such as fine actomyosin meshworks and stress fibers are essential force-generators for mechanical phenomena in live cells, including motility, morphogenesis, and mechanosensing. While there have been many studies on the rheology and assembly of individual stress fibers, few mathematical models have explicitly modeled the bulk actomyosin network in which stress fibers are embedded, particularly not in the case of high actin turnover. Generally the extent of the interplay between embedded stress fibers and contractile bulk networks is still not well understood. To address this gap, we design a model of stress fibers embedded in bulk actomyosin networks which utilizes the immersed boundary method, allowing one to consider various stress fiber rheologies in the context of an approximately viscous, compressible, contractile bulk network. We characterize the dynamics of bulk actomyosin networks with and without embedded stress fibers, and simulate a laser ablation experiment to demonstrate the effective long-range interactions between stress fibers as well as how perturbations of stress fibers can result in symmetry breaking of the bulk actomyosin network.