Computational Investigation of Cell Shape Changes Driven by Actomyosin Contractility

Changes in cell shapes are mostly driven by forces generated from the cytoskeleton. Recently, several in vitro experiments developed a synthetic cell-like system consisting of actin networks, cross-linking proteins, and myosin motors encapsulated by lipid vesicles or water droplets in order to study cell-scale behaviors facilitated by forces generated from actomyosin networks. However, these experiments are very hard to conduct, thus preventing exploration of wide parametric spaces. To overcome experimental limits and thus perform extensive parametric studies, we developed a novel agent-based model for a minimal cell-like structure comprised of discrete actomyosin cortex, osmotic pressure, and cell membrane simplified into a triangulated mesh. The cortex is coupled to the cell membrane to various extents via cross-linking proteins. Using this model, we found how cell shapes are regulated by a competition between actomyosin contractility that tends to induce contraction and osmotic pressure that tends to lead to expansion. We demonstrated that bulge that mimics cell blebs can be formed when the coupling level between the cortex and the membrane is intermediate. Our results provide insights into understanding how cell shapes are regulated under diverse conditions.