Abstract
ABSTRACT The intricate three-dimensional (3D) structures of multicellular organisms emerge through genetically encoded spatio-temporal patterns of mechanical stress. Cell atlases of gene expression during embryogenesis are now available, but connecting these to mechanical design principles that govern the emergence of embryonic shape requires an ability to measure mechanical stresses at single-cell resolution, across embryos, over time – A Mechanical Atlas. Developing a new mathematical theory for the static mechanics of 3D multicellular aggregates involving cell pressures and membrane and line tensions, we present a parameter-free and image-based strategy to constructing spatio-temporal maps of the mechanical stresses driving morphogenesis. We present in-silico and in-vivo evidence in favor of the accuracy and robustness of our approach. The ensuing mechanical atlas, within the context of ascidian gastrulation, reveals the adiabatic nature of the dynamics, its dependencies on the cell-cycle and cell-lineage, and the novel identification of spatio-temporal variations of cellular pressures.