How Living Tissue Can Flow While Remaining Rigid

Abstract:

Morphogenesis, the process by which an organism acquires its shape during development, involves not just tissue growth but also extensive cell rearrangement. This process is driven by internally generated and controlled forces, yet little is understood about how cells coordinate to achieve specific tissue shapes robustly. To address this question, we develop a model where cell rearrangements plastically deform the tissue while maintaining quasi-static force balance. Active forces are controlled by mechanical feedback loops instead of the constitutive relations that govern conventional materials. Nevertheless, force balance imposes strong constraints on local tissue geometry with testable implications for tissue dynamics. Our “active plastic flow” model predicts cell- and tissue-scale behaviors as observed in the early fruit fly embryo and explains how tissue can flow while remaining rigid. I will conclude with a perspective on how studying the mechanics of morphogenesis points us to exciting new soft matter physics.