Atomic Force Microscopy Reveals the Structure and Dynamics of the Cell Cortex

Abstract

Recent studies have shown that processes such as eukaryotic cell-cell interactions, differentiation and tissue development are controlled by mechanical signals. These mechanical stimuli come from the outside of the cells and induce remodeling of the cytoskeleton in the cell interior. Unfortunately, no dynamic data at high spatial resolution could be acquired so far on the cytoskeleton of live cells, and the mechanical heterogeneity at the subcellular level remains unknown. In particular, the cell cortex is a major determinant of the cell mechanics but its spatial arrangement is poorly understood, and the dynamic behavior of its elements could only be inferred through indirect methods. Here we demonstrate that simultaneous topography imaging and mechanical mapping of live cells under physiological conditions at high resolution and low forces is possible using atomic force microscopy. We applied our methods to perform direct imaging of the cell membrane actin cortex, reaching a resolution inferior to 100nm and a maximal 10s image acquisition rate. The cell cortex is structurally, mechanically and dynamically heterogeneous at the subcellular level, and its fastest rearrangement time was in the 10s range. Our resolution enabled direct sizing the sub-membrane actin meshwork, confirming estimates from electron microscopy and molecular diffusion studies. Furthermore, we can attribute dynamic parameters to actin meshworks of various architecture and estimate the forces that they can exert on neighboring cells.