Speaker
Description
The freshwater cnidarian Hydra is well known for its almost unlimited regenerative capacity. Even when cut into several pieces, each fragment can regenerate into a complete animal within approximately one week. Owing to its exceptional simplicity, Hydra allows simultaneous tracking of regeneration associated gene expression and tissue deformation throughout the regeneration process, from patterning to morphogenesis, and has therefore been widely used as a model system for studying developmental processes.
Previous studies have shown that Wnt signaling plays a central role in Hydra regeneration. In parallel, recent work in physics has proposed that a shortening of the periodic inflation-burst cycle of regenerating tissue marks a symmetry-breaking event. However, because anisotropic axial deformation does not necessarily increase at this time point, the definition of symmetry breaking itself remains ambiguous.
Here, we performed live imaging of tissue deformation dynamics throughout the entire regeneration process of Hydra tissue fragments excised under different initial conditions. By applying Fourier mode analysis to the observed deformation patterns, together with a minimal mechanical model incorporating the emergence of anisotropic spontaneous curvature, we quantitatively characterized mechanical symmetry breaking during regeneration. This approach allowed us to rigorously redefine body axis formation, previously understood phenomenologically in terms of shape changes and cellular polarity, as a symmetry-breaking process from a physical perspective. Furthermore, manipulation of the Wnt signaling pathway altered not only the timing of symmetry breaking but also the onset of head formation, revealing a previously unexplored tight coupling between tissue mechanics and regenerative competence.
