Characterizing cytoquakes, heavy-tailed fluctuations in the actomyosin cortex, using super-resolved micropost arrays

The dynamics of the actomyosin network are responsible for a wide range of cellular behavior. The cellular cortex exhibits active fluctuations punctuated by rearrangements with large step-like displacements, termed “cytoquakes,” that show heavy-tailed distributions, and spatial and temporal correlations resembling those of earthquakes and avalanches [1].  Using high-resolution measurements of fluctuations in the cortex via arrays of flexible microposts, we find that the distributions of sizes of these cortical fluctuations are well-modeled by exponentially truncated Lévy distributions for multiple cell types and substrate stiffnesses. The tail exponent of these distributions, which governs their shape, exhibits a clear dependence on the time scale (lag time) of the measurements even when perturbations due to noise in the measurements are accounted for. The results suggest that cortical fluctuations over a wide range of time scales are the result of a single physical process, of which cytoquakes are the largest component.

[1] Y. Shi et al., PNAS 116, 13189 (2019).