Contact inhibition induced dispersal promotes tissue ordering

During gastrulation, the endodermal cells of the developing zebrafish embryo undergo a period of dispersal mediated by Contact Inhibited Locomotion (CIL) followed by a period of convergence into the arrangement that forms the epithelial tissue sheet. In vivo observations have found the final distribution of endodermal cells to be highly regular and free of defects or density fluctuations. We propose that the high degree of tissue order arises from the system following a transition from a CIL dominated regime defined by repulsive interactions to a regime of attractive interactions finally forming cell-to-cell adhesion in a process similar to annealing. Preliminary simulations of this system suggest that the period of repulsive CIL-mediated interactions will produce hyperuniform distributions. We compare the results of particle-based simulations of active Brownian particles exhibiting CIL on a sphere's surface with the positions of in vivo wild-type endodermal cells as well as genetic and pharmacological perturbations. Our results highlight the relative contributions of the various cell-to-cell interactions to the final ordering of the cell population.