Revealing the mechanical nature of active embryonic tissues with magnetic droplets

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 depend on the local tissue mechanical properties, which govern the system's response to the internally generated forces. Despite their relevance, the role of mechanical forces and mechanical properties, as well as their spatiotemporal variations, in developmental processes remains 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. I will present a novel technique that employs magnetic microdroplets to quantify the local mechanical properties and stresses in soft materials, including living tissues. Using zebrafish as model system, I will show that the spatiotemporal control of tissue mechanical properties, rather than cellular forces, plays a key role in the shaping of embryonic tissues.