Bilateral symmetry and robustness during axis elongation in Drosophila

Bilateral symmetry is a highly conserved feature across many species. In Drosophila axis elongation, a process involving both global embryo-scale forces and local cell-scale forces, a remarkable amount of symmetry appears to be maintained between two lateral regions on the left and right sides of the embryo. Due to its importance in development, bilateral symmetry is likely to be a robust process capable of resisting heterogeneities and perturbations. However, it is unclear if this is due to coordination between cells in distant regions of the embryo that help to maintain symmetry. We first characterize baseline symmetry by comparing geometric and topological feature distributions and cell rearrangement events in wild-type embryos, confirming high degrees of symmetry and identifying a range of intrinsic variability. Next we identify spatiotemporally correlated regions of cells across the midline. We experimentally dissect how perturbing one region of the embryo via perturbations such as optogenetics, ablations, and mutants affects these correlated regions and events, lending insight into the degree and sources of bilateral coordination.These studies provide a foundation for unraveling how cell coordination may contribute to developmental robustness.