Thèses

Jeudi 26 Septembre 2024 à 14h00.

Characterization of the hypoxia-driven microphase separation of Dictyostelium

''Directeur de thèse / thesis director :
Jean-Paul Rieu,
Olivier Cochet-Escartin,
Christophe Anjard

Membres du jury / jury members :
Leonardo Gregory
Clément Nizak
Hélène Delanoe-Ayari
Salima Rafai
Jean-Paul Rieu
Olivier Cochet-Escartin
Christophe Anjard

Résumé / Abstract :

Since its discovery in 1935 by Raper, Dictyostelium discoideum has emerged as a model organism at the crossroads of biology and what we can call now active matter. The recent discovery of an aerotaxis response in Dd, a form of chemotaxis poorly documented in eukaryotic cells, along the associated aggregation behaviours, reinforces the potential of Dd to open new avenues for studying new active matter models and new biological processes. It is, therefore, not surprising that this thesis, along with other research, start to explore the aerotactic and hypoxic response of Dd. In this work, we focus on the new, oxygen-driven form of aggregation in Dd cells: the hypoxia-driven microphase separation. First we will present a quantitative description of this new phenomenon in terms of the preferred size of the aggregates. Afterward, we will correlate these properties to the amount of available oxygen and propose a simple model and numerical simulations, reproducing these parameters based on a competition between adhesion and long range repulsion by aerotaxis. Another interesting feature of this microphase separation is the higly dynamic behavior of the aggregates. Therefore, we will then focus on the migration of the formed aggregates and measure their dynamical properties (speed, mean squared displacements) and describe a non-trivial dependence of these parameters with aggregate size. To explain these results, we will propose a new simulation combining cell-cell adhesion, cell cooperation, cell persistence, aerotaxis and aerokinesis to reproduce the size-dependence of aggregate dynamics. In a final section, we will move away from a physical description of this microphase separation and start investigating the molecular determinants with a specific focus on adhesion molecules.

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