Jean-François Rupprecht

Welcome to my personal webpage

I am a CNRS researcher at the Centre Physique Théorique (Université Aix-Marseille, Luminy campus)
and CENTURI (Turing Center for Living Systems) Group Leader.
Please click here for the Out-of-equilibrium Mechanics (OM) team webpage.

Opportunities

Join the OM team! We have post-doctoral openings on the following projects:
- ANR JCJC COVFEFE (COVariant Fluctuating theory of Epithelial Flows): see French/English summaries.
- ANR PRC IMPERIS (Inducing Mechanical Perturbations on the Immune Synapse) with P. Pierobon, E. Donnadieu, J. Fattacioli,
- ANR PRCi CODAC (CO-Dynamics of cell Adhesion and Contraction) with P.-F. Lenne, Ed. Munroe, P. Recouvreux.

Please contact me by email for more info. Informal inquiries are welcome.

In addition to joining a dynamic team composed of highly motivated people, please have in mind that the Luminy campus is arguably one the most beautiful campus in the world (see some images here).

Most recent research

Cell motility and Tissue Mechanics

• Vertex models
  - [Lin EPJE 21]: Vertex models were first used to described for passive foams made of pressurized bubbles. In epithelial tissues, the bulk of cells can also exert anisotropic stresses on top of pressure. How do you reconcile that with vertex models? (link to paper pdf)
  
- [Lin arxiv 22]: In vitro epithelial tissues often display chaotic flows. These generically appear in active nematic theories; yet, as these are coarse-grained descriptions, they may miss important aspects that are specific to a cellular material. Here we simulate the onset of flows in an active cellular material with extensile stresses. We find a previously unreported rhombile cell shape motif. Lowering the cell-cell tension, we find that the cell shape undergoes a first order transition with a vanishing low extensile activity. Overall, our work challenges established views on the solid-fluid transitions in cellular materials. (link to preprint)

• Active nematics in curved geometries
  We extend the active nematics framework for curved surfaces with an up-down asymmetry; we find thresholdless active flows, discontinuous transitions and hysteresis between flowing steady states (link to preprint)
• Apico-basal 3D cell rearrangements
  During the Drosophila embryogenesis, the epithelial cellular arrangement can differ between the apical and basal side of the embryo;
  some cells have intriguing 3D shapes. Our numerical description of tissues (3D vertex model) explains how such shapes can appear [see publication 27 and 11]
  See also: MBI science feature.
• Dendritic arborization
  See M.-E. Perrin PhD thesis, our publication [19] and the press coverage in La Marseillaise journal.

MODCOV-19 initiative

Group Testing: Our objective is to propose models and careful estimates of the risks and benefits of group testing techniques -- a technique currently used in several institutes around the world which has potential to increase the COVID19 diagnostics capacity by a significant multiplying factor.
We apply our calculations in a surveillance context and the prevention of epidemic outbreaks of closed communities (nursing homes, universities).
See related our publication [21] and the related CNRS press release.

Less recent research

Tissue mechanics

• Mechanical pattern formation - Fish slices show a V-pattern, why?
  Active stresses, differential tissue-friction and tissue plasticity shapes the zebrafish myotome [see publication 15] See also: MBI science feature.

Cell motility

• Universal law of cell migration
  fast cells take more time to change direction than slow cells [see publication 5].
  Our random walk model relies on a chemical inertia mechanism whereby the distribution of polarity markers is controlled by the speed of the actin retrograde flow.
  See also: Le Monde feature.
• Magnetotactic bacteria
  We propose a new run-and-tumble walk model that predicts a new type of phase transition to collective flow [see publication 6].
• Fluctuating active gel theory
  We show that cortical stress fluctuations affect the position distribution of the cell nucleus and cell polarity [see publications 12-13].
  See also: MBI science feature.

Molecular processes

• Molecular ratchet - We proposed a new model on force generation by molecular motor assemblies [see publication 14].
  Cells sense the rigidity of their environment through local pinching – just as you would do with your fingers when you want to test if something is soft or rough;
  cells rely on myosin II motor assemblies – which contract over bundles of polymers called actin – to pinch their environment.
  Our model explains the challenging observations drawn from highly resolved experiments on these myosin assemblies.
  See also Nature Physics News and View feature, Curie Institute review and MBI summary.
• Super-resolution imaging - I developped algorithms optimizing image acquisition by stochastic optical microscopy [see publication 10].
• Theory of reactivity - We identify search strategies minimizing the average time of first encounter between a reactant and a fixed catalytic site.
  See also: A popular science overview of my PhD work (in French)
  
  

Publications list

See Google Scholar profile.

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1. Curvature-induced cell rearrangements in biological tissues
   Y. Lou, J.-F. Rupprecht, T. Hiraiwa, T. E. Saunders
   bioRxiv (2022)
2. Tissue fluidization by cell-shape-controlled active stresses
   S.-Z. Lin, M. Merkel, J.-F. Rupprecht
   arxiv (2022)
3. Active nematic flows on curved surfaces
   S. Bell (1), S.-Z. Lin(1), J.-F. Rupprecht*, J. Prost*
   arxiv (2022)
4. Mechanical stress driven by rigidity sensing governs epithelial stability
   S. Sonam(1), L. Balasubramaniam(1), S.-Z. Lin(1), ..., J.-F. Rupprecht*, B. Ladoux*
   bioRxiv (2022)
5. Implementation of cellular bulk stresses in vertex models of biological tissues
   S.-Z. Lin, M. Merkel, J.-F. Rupprecht,
   EPJE (2021) [author pdf]
6. Screening for SARS-CoV-2 by RT-PCR: Saliva or Nasopharyngeal Swab? Rapid Review and Meta-Analysis
   N. Ibrahimi, A. Delaunay-Moisan, C. Hill, G. Le Teuff, J.-F. Rupprecht, J.-Y. Thuret, D. Chaltiel, M.-C. Potier
   PLOS One (2021)
7. Group testing as a strategy for COVID-19 epidemiological monitoring and community surveillance
   V. Brault, B. Mallein, J.-F. Rupprecht
   PLOS Computational Biology (2021) + see CNRS press release and interviews in The Academic Times , News Medical, and Biologiste Infos
8. Cell junction mechanics beyond the bounds of adhesion and tension
   P.F. Lenne, J.-F. Rupprecht, V. Viasnoff
   Developmental Cell (2021) [HAL version]
9. Deterministic and stochastic rules of branching govern dendritic morphogenesis of sensory neurons
   A. Palavalli, N. Tizón-Escamilla, J.-F. Rupprecht, T. Lecuit
   Current Biology (2020) [HAL version]
   See also our press coverage in La Marseillaise journal.
10. Adhesion-mediated heterogeneous actin organization governs apoptotic cell extrusion
    A. P. Le, J.-F. Rupprecht, R.-M. Mège, Y. Toyama, C. T. Lim, B. Ladoux
    Nature Communications (2020) [HAL version]
11. Embryonic geometry underlies phenotypic variation in decanalized conditions
    A. Huang, J.-F. Rupprecht, and T. E. Saunders
    eLife, 9, e47380 (2020)
12. Microtubule plus-end dynamics link wound repair to the innate immune response
    C. Taffoni, S. Omi, C. Huber, S. Mailfert, M. Fallet, J.-F. Rupprecht, J. J. Ewbank, N. Pujol,
    eLife (2020)
13. Shaping the zebrafish myotome by intertissue friction and active stress
    S. Tlili, J. Yin, J.-F. Rupprecht, M. A. Mendieta-Serranoa, G. Weissbart, N. Verma, X. Teng, Y. Toyama, J. Prost, T. E. Saunders
    PNAS 116, 25430 (2019) [HAL version]
14. Myosin filaments reversibly generate large forces in cells
    J. Lohner (1), J.-F. Rupprecht (1), J. Hu, N. Mandriota, M. Saxena, J. Hone, D. Pitta de Araujo, O. Sahin, J. Prost, M. P. Sheetz
    Nature Physics, 15, 689–695 (2019)
15. Maximal fluctuations of confined actomyosin gels: dynamics of the cell nucleus
    J.-F. Rupprecht, A. Singh, G. V. Shivashankar, M. Rao, J. Prost
    Physical Review Letters, 120, 098001 (2018) Arxiv version.
    
16. Soft inclusion in a confined fluctuating active fluid
    A. Singh, J.-F. Rupprecht, G. V. Shivashankar, J. Prost, M. Rao
    Physical Review E, 97, 032602 (2018) Arxiv version.
17. Geometric constraints alter cell arrangements within curved epithelial tissues
    J.-F. Rupprecht, K. H. Ong, J. Yin, A. Huang, A. P Singh, S. Zhang, W. Yu, T. E Saunders
    Molecular Biology of the Cell, mbc. E17-01-0060 (2017).
    
18. Trade-offs between structural integrity and acquisition time in stochastic super-resolution microscopy techniques
    J.-F. Rupprecht, A. Martinez-Marrades, Z. Zhang, R. Changede, P. Kanchanawong, G. Tessier
    Optics Express, 25, Issue 19, 23146 (2017).
19. The escape problem for mortal walkers
    D. Grebenkov, J.-F. Rupprecht
    The Journal of Chemical Physics, 146, 084106 (2017) -- Arxiv version.
20. Perspective: A fresh eye on nonequilibrium systems
    J.-F. Rupprecht, J. Prost
    Science, 352, Issue 6285, p. 514 (2016) , [HAL] .
21. Optimal search by run-and-tumble particles
    J.-F. Rupprecht, O. Bénichou, R. Voituriez,
    Physical Review E, 94, 012117 (2016) -- Arxiv version.
22. Velocity condensation of magnetotactic bacteria
    J.-F. Rupprecht, N. Waisbord, C. Ybert, C. Cottin-Bizonne and L. Bocquet
    Physical Review Letter 116, 168101 (2016) --- Arxiv version.
23. Actin flows mediate a universal coupling between cell speed and persistence
    P. Maiuri (1), J.-F. Rupprecht (1), S. Wieser (1),
    V. Ruprecht, N. Carpi, M. Coppey, S. De Beco, O. Bénichou, N. Gov, C.P. Heisenberg, C. Large-Crespo, F. Lautenschlaeger,
    M. Le Berre, A. M. Lennon-Dumenil, M. Raab, H.R. Thiam, M. Piel, M. Sixt, R. Voituriez,
    Cell, 161, 2, pp 374 (2015).
    
24. Exit time distribution in spherically symmetric two dimensional domains
    J.-F. Rupprecht, O. Bénichou, D. S. Grebenkov, R. Voituriez
    Journal of Statistical Physics 158, 1, pp 192 (2015) --- Arxiv version.
25. Stochastic 3D field mapping using Brownian scatterers
    A. Martinez-Marrades, J.-F. Rupprecht, M. Gross, G. Tessier
    Optics Express, Vol. 22, 23, pp. 29191-29203 (2014)
26. Kinetics of Active Surface-Mediated Diffusion in Spherically Symmetric Domains
    J.-F. Rupprecht, O. Bénichou, D. S. Grebenkov, R. Voituriez
    Journal of Statistical Physics 147, pp 891 (2012) --- Arxiv version.
27. Exact Mean Time for surface-mediated diffusion
    J.-F. Rupprecht, O. Bénichou, D. S. Grebenkov, R. Voituriez
    Physical Review E 86, pp 041135 (2012) --- Arxiv version.

Short CV

01/2019 onwards - CNRS researcher at the Centre Physique Théorique (Université Aix-Marseille, Luminy campus).
09/2015 - Research fellow with J. Prost at the Mechanobiology Institute (National University of Singapore).
2014-2015 - Post-doctoral research with L. Bocquet at LPS (Ecole Normale Supérieure, Paris).
2012-2014 - Graduate student with R. Voituriez and O. Bénichou at the LPTMC (Université Pierre-et-Marie-Curie, Paris).
2008-2012 - Elève at the Ecole Normale Supérieure (Paris).

Administrative duties

2021/2024 - Member of the CoNRS section 02 and 51.

Contact

Email: jean-francois.RUPPRECHT@univ-amu.fr
Address: Centre de Physique Théorique, Université Aix-Marseille, Campus de Luminy, 163 Avenue de Luminy, 13009 Marseille
Office: 5th floor, office 514
Phone: number in my email signature.