Otger Campas, Ph.D., University of California, Santa Barbara
The sculpting of tissues into their functional morphologies requires a tight spatiotemporal control of their mechanics. While cell-generated mechanical forces power morphogenesis, the resulting tissue movements strongly depend on the local tissue mechanical (material) properties, as these govern the system's response to the internally generated forces. Despite their relevance, the specific roles of mechanical forces and mechanical properties in tissue morphogenesis remain largely unknown, mainly because of a lack in methodologies enabling direct in vivo and in situ measurements of cell-generated forces and mechanical properties within developing 3D tissues and organs. In this talk, I will present two microdroplet-based techniques that we have recently developed to quantify both local cellular forces and mechanical properties within developing 3D tissues. Focusing on body axis elongation in zebrafish, I will show that spatial variations in supra-cellular (tissue level) stresses, and especially in tissue mechanical properties, control the morphogenetic movements necessary to shape the embryonic axis. In contrast, the magnitude of cellular forces is largely uniform in the tissue. Overall, our results indicate that spatiotemporal variations in tissue mechanical properties, rather than cellular forces, regulate the sculpting of embryonic 3D tissues.