Adaptive viscoelasticity of epithelial cell junctions: from models to methods.

Epithelial morphogenesis relies on constituent cells' ability to finely tune their mechanical properties. Resulting elastic-like and viscous-like behaviors arise from mechanochemical signaling coordinated spatiotemporally at cell-cell interfaces. Direct measurement of junction rheology can mechanistically dissect mechanical deformations and their molecular origins. However, the physical basis of junction viscoelasticity has only recently become experimentally tractable. Pioneering studies have uncovered exciting findings on the nature of contractile forces and junction deformations, inspiring a fundamentally new way of understanding morphogenesis. Here, we discuss novel techniques that directly test junctional mechanics and describe the relevant Vertex Models, and adaptations thereof, capturing these data. We then present the concept of adaptive tissue viscoelasticity, revealed by optogenetic junction manipulation. Finally, we offer future perspectives on this rapidly evolving field describing the material basis of tissue morphogenesis.