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Oxygen driven spreading and microphase separation in Dictyostelium discoideum
Par Jean-Paul Rieu (Université Claude Bernard Lyon 1)
Le 6 Décembre 2022 à 11h00 - Salle de séminaires 5ème étage - LJP - Tours 32-33


Oxygen driven spreading and microphase separation of eukaryotic cells


J.-P. Rieu1,*, A. Carrère1, N. Ghazi1, C. Anjard1, F. Detchevery1, O. Cochet-Escartin1, S. Hirose3,K. Funamoto3, M. Demircigil2, S. V. Calvez2


1-Institut Lumière Matière and 2- Institut Camille Jordan, Université Claude Bernard Lyon 1, Villeurbanne, France. 3- Institute of Fluid Science, Tohoku University, Sendai, Japan


Cells exhibit multiple responses to environmental stresses. A state of low oxygen (O2) occurs frequently in soil, water and multicellular tissues and has played a pivotal evolutionary role in shaping multicellularity. We study the mechanisms of a novel behavior in the amoeba Dictyostelium discoideum (Dd) in which cells collectively regulate their motility and adhesion in response to self-generated hypoxia. 

Vertically confining a micro-colony of Dd cells in a growth medium with a coverglass triggers the propagation of a ring cells for days (Fig. C, [1]). Cells consume O2 and try to escape by aerotaxis the hypoxic zone. Below a millimetric culture medium film, Dd cells proliferate until some critical density. Then they assemble in compact domains, of about 100µm, surrounded by a dense cellular gas phase. Domains stay mobile and stable in size during several days. Their size is regulated by the O2 atmospheric level above the dish or the medium height (Fig. A-B, [2]). 

These observations as well as microfluidic experiments with imposed O2 gradients highlight the importance of oxygen regulation and self-generated gradients as an emergent organizing principle for biological matter. The variety of cell behaviors are modeled using both mean field PDE models and Monte-Carlo Lattice models with a few measurable parameters: cell division rate, motility (diffusion constant), aerotactic speed, oxygen modulated cell-cell adhesion and consumption [1]. In particular, the new dynamical microphase separation of Dd results from a balance between a long-range repulsion, trough self-generated O2 gradients due to O2 consumption, and a short-range attraction due to cell-cell adhesion.




Figure: (A) Dd aggregates under a culture medium layer of varying height, with the height profile from the dish wall (left) drawn above. (B) Zoom on one aggregate surrounded by a cellular gas phase (arrows point to the first layer of cell flattened on the surface). (C) Spreading of a Dd covered spot of cells with a ring formation moving outwardly toward free O2.


[1] O. Cochet-Escartin et al, elife 2021 10:e64731

[2] A. Carrère, et al. Microphase separation of living cells. bioRxiv (2022)