Multilevel Dynamics in Zebrafish Gastrulation

We approach the understanding of zebrafish gastrulation, through the quantitative analysis and biomechanical modeling of multiscale in vivo imaging data. The cellular level of organization is taken as resulting from the integration of sub-cellular and supra-cellular processes. Cell dynamics are investigated through 3D+time imaging of developing embryos with fluorescent nuclear and membrane staining. The automated reconstruction of the cell lineage tree, annotated with nucleus and membrane segmentation, provides measurements for cell behavior: displacement, division, shape and contact changes, as well as fate and identity. This quantitative data is sufficient to find statistical models for cell proliferation and cell descriptors evolution in time and space, and characterize the spatial and temporal length scale of cell displacements and tissue deformations. Confronting numerical simulation derived from a multi-agent based biomechanical model with empirical measurements extracted from the reconstructed digital specimens, is the basis for testing hypotheses for processes underlying early embryogenesis. Further correlating cell behavior, tissue biomechanics and biochemical activities by comparing the patterns revealed by cell fate, velocity, strains or gene expression, is a step toward the integration of multi-level dynamics. This overall framework lays the ground for a transdiciplinary approach of living systems’ morphogenesis.