Role of active stress and actin alignment in cell division: A hydrodynamic perspective

Abstract Cell division is a fundamental biological process in which a parent cell divides into two daughter cells. The cell cortex, a thin layer primarily composed of actin filaments and myosin motors beneath the plasma membrane, plays a critical role in ensuring proper cell division. In this study, we apply a hydrodynamic model to describe the actin cortex as an active nematic surface, incorporating orientational order arising from actin filament alignment and anisotropic active stress produced by myosin motors. By analyzing the linearized dynamics, we investigate how shape, flow, and stress regulators evolve over time when the surface deviates slightly from a sphere. Our findings reveal that the active alignment of actin filaments, often overlooked in previous studies, is crucial for successful division. Furthermore, we demonstrate that a cortical chiral flow naturally emerges as a consequence of this active alignment. Overall, our results provide a mechanistic explanation for key phenomena observed during cell division, offering new insights into the role of active stress and filament alignment in cortical dynamics.