The Actomyosin Cortex of Cells: A Thin Film of Active Matter

The actomyosin cortex is a thin film, containing actin filaments and myosin molecular motors, located beneath the plasma-membrane of eukaryotic cells. Active processes, driven by ATP hydrolysis, can generate mechanical forces in the cortex. Coordinated force-generation drives large-scale mechanical flows and orientation patterns. These flows can pattern proteins coupled to the cortex leading to the emergence of active mechanochemical patterns. In this review, we discuss physical approaches to understand force-generation and the concomitant patterns observed in the actomyosin cortex. We briefly outline the hydrodynamic theory of active gels as applicable to the cortex and discuss its consequences. We speculate on the role of the actomyosin cortex in sculpting large-scale tissues and end with an outlook for open problems.