Signatures of Jamming in a Potts Model of Cellular Migration

We explore glassy behavior and the jamming transition in an equilibrium Cellular Potts Model (CPM) as a function of confinement, cell adhesion, and cell shape. We compare simulations of single cells, cellular aggregates, and confluent monolayers as a function of cell adhesion energies and target cell shape. We consider metrics that may identify signatures of this transition, including diffusion coefficients, anomalous diffusion exponents, cell shape, cell rearrangements, and velocity correlations. The onset of jamming coincides with an abrupt drop in cell mobility, rapid transition to sub-diffusive behavior, and cessation of cellular rearrangements that is unique to confluent monolayers. Velocity correlations reveal collective migration near the transition point as a natural consequence of high energy barriers to rearrangement for certain cell types. Cell shapes across the fluid-to-solid transition in the CPM are found to be consistent with predictions of jamming in vertex-type simulations and trends from experiment, while changes in cell shape within CPM monolayers can fluidize an otherwise jammed cellular collective. Finally, inclusion of a protrusion-based cell motility enhances collectivity in CPM monolayers and reproduces experimentally observed migration patterns.