Biophysical Society Thematic Meeting | Riga 2026

Active and Responsive Soft Matter: From Biological to Engineered Systems

Tuesday Speaker Abstracts

TOPOLOGICAL DEFECTS AND CELL-MATRIX FEEDBACK GOVERN MYOBLAST FUSION Yoann Le Toquin 3 ; Sushil Dubey 4,7,8 ; Aleksandra Ardaševa 1,2 ; Lakshmi Balasubramaniam 4,5 ; Emilie Delaune 3 ; Valérie Morin 3 ; Amin Doostmohammadi 2 ; Christophe Marcelle 3,6 ; Benoît Ladoux 4,7,8 ; 1 École Polytechnique Fédérale de Lausanne (EPFL), School of Life Science, Lausanne, Switzerland 2 University of Copenhagen, Niels Bohr Institute, Copenhagen, Denmark 3 Université Claude Bernard Lyon1, INMG, Lyon, France 4 Université Paris Cité, Institut Jacques Monod, Paris, France 5 University of Cambridge, Wellcome Trust / CRUK Gurdon Institute, Cambridge, United Kingdom 6 Monash University , Australian Regenerative Medicine Institute, Clayton, Australia 7 Friedrich-Alexander Universität Erlangen-Nürnberg, Department of Physics, Erlangen, Germany 8 Max-Planck-Zentrum für Physik und Medizin, Erlangen, Germany Myoblast fusion into myotubes is critical for muscle formation, growth, and repair. While the cellular and molecular mechanisms regulating this process are increasingly understood, the role of biomechanics remains largely unexplored. Here, we combine in vitro experiments with an active nematic theoretical framework to demonstrate that a feedback loop between cell mechanics and cell-generated stresses governs myoblast fusion. Here, we present experimental results showing that myoblast and myotube organization follows principles analogous to active liquid crystals. In particular, fusion events are spatially localized at comet-shaped topological defects in the cellular alignment field, which coincide with regions of elevated compressive stress. We then introduce a minimal theoretical framework in which the myoblasts are depicted as an active nematic coupled to extracellular matrix (ECM) dynamics, which is actively remodeled by myoblasts. The model shows that ECM deposition both reflects and reinforces nematic organization, leading to enhanced stress localization at defects. This coupled description quantitatively reproduces the observed self-organization patterns and predicts the stress landscapes that regulate fusion, in agreement with experimental measurements. Together, these results establish a predictive framework linking active stresses, topological defects, and time evolving ECM interactions in myogenesis, highlighting the central role of active matter physics in tissue morphogenesis.

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