Biology subjects

Murrell, M. P.

Publications and source records attributed to Murrell, M. P..

3 recordsLinked to original sources

bioRxiv2024

Growth-induced collective bending and kinetic trapping of cytoskeletal filaments

Growth and turnover of actin filaments play a crucial role in the construction and maintenance of actin networks within cells. Actin filament growth occurs within limited space and finite subunit resources in the actin cortex. To understand how filament growth shapes the emergent architecture of actin networks, we developed a minimal agent-based model coupling filament mechanics and growth in a limiting subunit pool. We find that rapid filament growth induces kinetic trapping of highly bent actin filaments. Such collective bending patterns are long-lived, organized around nematic defects, and arises from competition between filament polymerization and bending elasticity. The stability of nematic defects and the extent of kinetic trapping are amplified by an increase in the abundance of the actin pool and by crosslinking the network. These findings suggest that kinetic trapping is a robust consequence of growth in crowded environments, providing a route to program shape memory in actin networks.

biophysics↗

bioRxiv2023

Actin and microtubules position stress granules

Membraneless organelles, composed of protein and nucleic acids, alter the biochemical and physical landscape of the cell. While specific membraneless organelles are found in stereotypical locations, little is known about the physical mechanisms that guide their positioning. Here, we investigate how stress granules, a type of cytoplasmic membraneless organelle, establish their stereotypical perinuclear positioning. We find that actin and microtubules play complementary roles. Lamellar actin confines stress granules, and its retrograde flow drives them toward the cell center. Microtubules, in turn, adhere to stress granules through capillary interactions, which tend to concentrate stress granules in micro-tubule rich regions near the nucleus. Similar physical mechanisms are likely to play a role in the positioning of other membraneless organelles.

biophysics↗

bioRxiv2020

Tissue pressure and cell traction compensate to drive robust aggregate spreading

In liquid droplets, the balance of interfacial energies and substrate elasticity determines the shape of the droplet and the dynamics of wetting. In living cells, interfacial energies are not constant, but adapt to the mechanics of their environment. As a result, the forces driving the dynamics of wetting for cells and tissues are unclear and may be context specific. In this work, using a combination of experimental measurements and modeling, we show the surface tension of cell aggregates, as models of active liquid droplets, depends upon the size of the aggregate and the magnitude of applied load, which alters the wetting dynamics. Upon wetting rigid substrates, traction stresses are elevated at the boundary, and tension drives forward motion. By contrast, upon wetting compliant substrates, traction forces are attenuated, yet wetting occurs at a comparable rate. In this case, capillary forces at the contact line are elevated and aggregate surface tension contributes to strong outward, pressure-driven cellular flows. Thus, cell aggregates adapt to the mechanics of their environments, using pressure and traction as compensatory mechanisms to drive robust wetting.

biophysics↗