Cortical Flow-Driven Shapes of Nonadherent Cells

Area of Science:

• Cell biology
• Biophysics
• Theoretical biology

Background:

• Nonadherent polarized cells often exhibit a pear-like, elongated shape.
• The cell cortex, a layer beneath the plasma membrane, plays a crucial role in determining cell shape and mechanics.

Purpose of the Study:

• To investigate the relationship between active stresses in the cell cortex and cell morphology.
• To develop a minimal model explaining the elongated shape of nonadherent polarized cells.

Main Methods:

• Utilized a minimal biophysical model of the cell cortex as a contractile active gel.
• Analyzed the influence of cortical viscosity and filament ordering on active stress anisotropy.
• Investigated the dependence of cell shape on cortical flow patterns and cytoplasmic rheology.

Main Results:

• Cortical active stress anisotropy, driven by viscosity and filament ordering, can account for pear-like cell elongation.
• Predicted cell shapes are determined solely by the cortical flow pattern, independent of the flow's origin.
• Cell shape predictions showed weak sensitivity to cytoplasmic rheology.

Conclusions:

• The active gel model successfully explains observed cell morphologies, including spherical, elongated, and oblate shapes.
• A phase diagram of cell shapes was proposed based on actin flows from contractile instability.
• The model provides a unified framework for understanding diverse cell shapes observed experimentally.