Shape, Strain, and Stability: Epithelia Under High Strain

Mechanical forces play crucial roles in epithelia tissue morphogenesis and function, yet individual cells often respond differently to the same external force. Strain heterogeneity, the non-uniform deformation of cells under uniform external mechanical stimuli, may underlie tissue-level robustness and guide morphogenetic outcomes. In this study, we applied a defined uniaxial strain to Xenopus laevis epithelial explants and investigated how strain was distributed at the cellular level. Live imaging and quantitative analysis revealed that despite a uniform tissue-level strain, cellular strain was heterogeneous, suggesting variable responses to a uniform mechanical stimulus. To understand the source of this variability, we used an image analysis pipeline to explore multiple aspects of cell morphology. We found that cell intrinsic material properties, represented by Poisson index, had the strongest correlation with strain heterogeneity, suggesting a dominant role in variable mechanical response. We further analyzed how force was distributed at the cellular level using a vinculin force sensor and laser ablation. These experiments demonstrated that forces are primarily transmitted through the medio-apical actomyosin cortex whereas junctional actomyosin facilitates dissipation and remodeling. These findings provide new insights into the physical principles that underlie epithelial resilience and adaptive remodeling, highlighting the importance of distinct functions of junctional and medio-apical actomyosin networks in mechanical adaptation.