Wnt signaling modulates tissue mechanics, actin order, and regeneration inHydra vulgaris

Hydra vulgarisis a powerful model organism in the study of axial patterning and regeneration. While recent models emphasize the importance of mechanical cues in establishing the body axis ofHydratissue spheres, the precise role of the Wnt pathway, known to be central to axial patterning, in regulating tissue mechanics and cytoskeletal organization remains unclear. In this paper, we pharmacologically modulated the canonical Wnt pathway using alsterpaullone (AP) and iCRT14 and assessed their effects on regeneration, tissue rheology, osmotic oscillations and actin organization inHydratissue spheres. We found that AP prevents full regeneration, softens the constitutive tissues, disrupts osmotic oscillations and increases the area coverage of oriented actin fibers. Conversely, we found that treatment with iCRT14 does not systematically block regeneration despite inducing a small decrease in actin fibers area coverage. These results support the underlying hypotheses of two existing mechano-chemical models ofHydrapatterning, suggesting that Wnt-driven feedbacks on both tissue stiffness and actin order could contribute to the robust emergence of body axes. Our findings highlight the possibility of redundant and coupled mechanisms in theHydrapatterning system, potentially explaining its robustness.