Affiliation:
1. Université de Paris, CNRS, Institut Jacques Monod, 75006 Paris, France
2. Equipe Labellisée Ligue Contre le Cancer, 75013 Paris, France
Abstract
Many studies of cytoplasm rheology have focused on small components in the submicrometer scale. However, the cytoplasm also baths large organelles like nuclei, microtubule asters, or spindles that often take significant portions of cells and move across the cytoplasm to regulate cell division or polarization. Here, we translated passive components of sizes ranging from few up to ~50 percents of the cell diameter, through the vast cytoplasm of live sea urchin eggs, with calibrated magnetic forces. Creep and relaxation responses indicate that for objects larger than the micron size, the cytoplasm behaves as a Jeffreys material, viscoelastic at short timescales, and fluidizing at longer times. However, as component size approached that of cells, cytoplasm viscoelastic resistance increased in a nonmonotonic manner. Flow analysis and simulations suggest that this size-dependent viscoelasticity emerges from hydrodynamic interactions between the moving object and the static cell surface. This effect also yields to position-dependent viscoelasticity with objects initially closer to the cell surface being harder to displace. These findings suggest that the cytoplasm hydrodynamically couples large organelles to the cell surface to restrain their motion, with important implications for cell shape sensing and cellular organization.
Funder
Agence Nationale de la Recherche
EC | European Research Council
Association pour la recherche sur le cancer
La Ligue Contre le Cancer
Fondation Bettencourt Schueller
Publisher
Proceedings of the National Academy of Sciences
Cited by
6 articles.
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