A universal form for heavy-tailed fluctuations in the actomyosin cortex*

The fluctuations of the actomyosin cortex still defy a fully satisfying explanation, despite long study. Arrays of flexible microposts allow for high-resolution measurements of cortical activity across a wide range of length scales [1][2]. Here we report that, after accounting for static heterogeneity in cell–micropost contacts, the displacement distribution of the fluctuations displays a universal form across time, cell type, and substrate stiffness, resembling an exponentially truncated stable distribution (ETSD). The parameters describing the ETSD, including the stability parameter (exponent) and characteristic lengths exhibit clear dependence on lag time. The relationship of these heavy-tailed fluctuations to the previously reported cytoquakes—rearrangements with large step-like displacements—will be discussed. The appearance of such an ETSD descriptor underscores the cortex’s similarity to soft glasses, where similar distributions have been observed.

 

[1] Y. Shi et al, PNAS 116: 13839-46 (2019).

[2] Y. Shi et al, Integr. Biol. 13: 246-257 (2021).