Propagating gene expression fronts in a one-dimensional coupled system of artificial cells

Living systems employ front propagation and spatiotemporal patterns encoded in biochemical reactions for communication, self-organization and computation(1-4). Emulating such dynamics in minimal systems is important for understanding physical principles in living cells(5-8) and in vitro(9-14). Here, we report a one-dimensional array of DNA compartments in a silicon chip as a coupled system of artificial cells, offering the meansto implement reaction-diffusion dynamics by integrated genetic circuits and chip geometry. Using a bistable circuit we programmed a front of protein synthesis propagating in the array as a cascade of signal amplification and short-range diffusion. The front velocity is maximal at a saddle-node bifurcation from a bistable regime with travelling fronts to a monostable regime that is spatially homogeneous. Near the bifurcation the system exhibits large variability between compartments, providing a possible mechanism for population diversity. This demonstrates that on-chip integrated gene circuits are dynamical systems driving spatiotemporal patterns, cellular variability and symmetry breaking.