February 26, 2024: Madhav Mani

On the many-body physics of embryonic development
Abstract:
While the complexity and robustness of embryonic development are plain to see, a physicist might ask whether there are simple principles that underlie them. Can we ever have a “Theory” or is it just a matter of filling up repositories of data, tabulating what happens, but not why? Focusing on the development of a sea squirt, we develop theoretical approaches pointing to the origins of the embryo’s mechanical and chemical dynamics based on recent live-imaging and single-cell gene expression measurements. The physical models we propose go beyond rationalizing dynamics; in fact, they form the basis of parametric inferences that give insight into the dynamics of hidden variables and the origins of their collective modes. In particular, I will present 1) the first mechanical atlas for an embryo, where we provide the first glimpses of mechanical stresses in living and unperturbed embryos at single-cell resolution over time, and 2) the first interactome, where, through the construction of a Heisenberg-like model for the effective transcriptomic degrees of freedom, we identify a compact set of spatial (cell-cell) interactions that underlie the complex correlation structure we observe. The overarching theme that I hope to convey 1) the power of effective, or phenomenological, models when analyzing modern high-dimensional measurements of complex biological systems, and 2) the necessity of such models if we are to glean insights into dynamical principles that have the potential to shed light on a broader scope of phenomena than the one at hand.