Mechanochemical active fluids

We are interested in the emergent dynamics observed in animal cells, resulting from the coupling of active mechanics and biochemical signaling. We have theoretically shown that coupling non-linear signaling circuits with active flows robustly leads to localized (i.e. spatially confined) dynamics in the actomyosin cortex. Experimental tests of this and further self-organized dynamics are currently being performed by our collaborators.

With Daniel Riveline, Olivier Pertz, Damian Brunner and Karsten Kruse

Figure: trigger waves and spirals in an active fluid.

Localized states in active fluids (2022)

DNA condensates

In viruses and cells, DNA is closely packed and tightly curved thanks to polyvalent cations inducing an effective attraction between its negatively charged filaments. Our understanding of this effective attraction remains very incomplete, mainly because it results from multiple microscopic mechanisms that are hard to predict starting from first principles. We study this fundamental attraction by combining structural data of DNA condensates realized in vitro with effective equilibrium theories, where inter-helical forces compete with DNA elasticity.

With Amélie Leforestier, Françoise Livolant and Martin Lenz

Figure: math. model of a twisted DNA toroid.

Twist-induced local curvature of filaments in DNA toroids (2021)
Local structure of DNA toroids reveals curvature-dependent intermolecular forces (2021)

Protein-membrane interaction

ESCRT-III polymers are responsible for membrane remodeling in many cellular processes, ranging from the maturation of retroviruses (like HIV and Ebola) to the constriction of the cytokinetic bridge. Despite its ubiquitous biological role, many aspects of ESCRT-mediated membrane remodeling are still unclear. Recent in vitro experiments revealed that ESCRT polymers can reshape spherical vesicles into helical tubes. Inspired by structural insights from such experiments, we develop generic theories on the competition between ESCRT and membrane elasticity to shed light on the ESCRT-membrane interactions responsible of membrane remodeling in vivo.

With Joachim Moser Von Filseck, Aurélien Roux and Martin Lenz

Figure: exptal image vs. math. model of a helical membrane tube.

Anisotropic ESCRT-III architecture governs helical membrane tube formation (2020)