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Join Professor Aurélien Roux from University of Geneva for a Force Talk entitled “Topological defects control morphogenesis of cellular tornadoes and bicephalous hydra”.


Liquid crystals are characterized by unique flow properties, dictated by the long-range order of molecules with anisotropic shapes that locally align at high density. Cellular tissues are viscoelastic materials, that have unique flow properties, best exemplified during morphogenesis: oriented flows participate in the formation of shapes and organs. Tissues are composed of cells, and cell shape and forces are dictated by contractile filaments of the cytoskeleton. Thus, both cell assemblies and cytoskeleton assemblies can be described as active nematics, which creates topological defects because of their activity (growth, contractility). In the small animal Hydra, the regeneration of head and foot correlates with the position of integer topological defects in the nematic field of actin, suggesting that topological defects in muscle cells could control or drive morphogenesis. In vitro, flat assemblies of muscular cells form +1/2 and -1/2 defects spontaneously in their nematic order. I will show that by confining these cells on micropatterns, we can trigger the formation of integer defects, initially spirals, and then, through proliferation, the cell layer transitions to an aster configuration, and further grow into a vortex, forming a protrusion of half a millimetre [1-3]. I will further show that mechanical deformation of the nematic field of the actin in the Hydra causes bicephalous regeneration. Altogether, our findings support that topological defects in the nematic order of muscles cells or actin control the stress field in developing tissues, driving morphogenesis.


[1] P. Guillamat, C. Blanch-Mercader, G. Pernollet, K. Kruse, A. Roux, Integer topological defects organize stresses driving tissue morphogenesis, Nat Mater 21(5) (2022) 588-597.

[2] C. Blanch-Mercader, P. Guillamat, A. Roux, K. Kruse, Quantifying Material Properties of Cell Monolayers by Analyzing Integer Topological Defects, Phys Rev Lett 126(2) (2021) 028101.

[3] C. Blanch-Mercader, P. Guillamat, A. Roux, K. Kruse, Integer topological defects of cell monolayers: Mechanics and flows, Phys Rev E 103(1-1) (2021) 012405.


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At this event

Sergi  Garcia-Manyes

Professor of Biophysics