Quantifying the forces associated with body elongation in a chicken embryo

The role of mechanical forces in the context of morphogenesis and growth regulation in an embryo is now well accepted. Yet, it is still a challenge to perform mechanical measurements and manipulations on a whole embryo to obtain quantitative insights. Here we use chick embryos in the gastrulation stage to study how the tissues that form the body axis coordinate their rates of elongation. We found that the coordination and axis straightness are achieved via a positive feedback loop involving mechanics, as revealed by surgical implantation of soft gels and mechanical manipulation with magnetic pins. We also show that cell movement is required for the generation of, and can be a response to, the tissue forces. Finally, we deploy custom tools to apply force-clamps on the embryo over long times to affect both the growth and form of the embryo.