Structural, mechanical, and dynamical variability of the actin cortex in living cells.

In eukaryotic cells, an actin-based cortex lines the inner leaflet of the plasma membrane, endowing the cells with crucial mechanical and functional properties. Unfortunately, it has not been possible to study the structural dynamics of the actin cortex at high lateral resolution in living cells. Here, we performed atomic force microscopy time-lapse imaging and mechanical mapping of actin in the cortex of living cells at high lateral and temporal resolution. Cortical actin filaments adopted discernible arrangements, ranging from large parallel bundles with low connectivity to a tight meshwork of short filaments. Mixing of these architectures resulted in attuned cortex networks with specific connectivity, mechanical responses, and marked differences in their dynamic behavior.