Symmetry Breaking and Emergence of Directional Flows in Minimal Actomyosin Cortices

• Main Authors: Sven K. Vogel, Christian Wölfer, Diego A. Ramirez-Diaz, Robert J. Flassig, Kai Sundmacher, Petra Schwille
• Format: Article
• Language: English
• Published: MDPI AG 2020-06-01
• Series: Cells
• Subjects: bottom-up synthetic biology; motor proteins; pattern formation; self-organization
• Online Access: https://www.mdpi.com/2073-4409/9/6/1432

Cortical actomyosin flows, among other mechanisms, scale up spontaneous symmetry breaking and thus play pivotal roles in cell differentiation, division, and motility. According to many model systems, myosin motor-induced local contractions of initially isotropic actomyosin cortices are nucleation points for generating cortical flows. However, the positive feedback mechanisms by which spontaneous contractions can be amplified towards large-scale directed flows remain mostly speculative. To investigate such a process on spherical surfaces, we reconstituted and confined initially isotropic minimal actomyosin cortices to the interfaces of emulsion droplets. The presence of ATP leads to myosin-induced local contractions that self-organize and amplify into directed large-scale actomyosin flows. By combining our experiments with theory, we found that the feedback mechanism leading to a coordinated directional motion of actomyosin clusters can be described as asymmetric cluster vibrations, caused by intrinsic non-isotropic ATP consumption with spatial confinement. We identified fingerprints of vibrational states as the basis of directed motions by tracking individual actomyosin clusters. These vibrations may represent a generic key driver of directed actomyosin flows under spatial confinement in vitro and in living systems.