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

When multicellular systems need to communicate over long distances, and signalling molecules are too slow to diffuse, travelling fronts of these molecules emerge—a phenomenon now reconstituted in a coupled array of artificial cells. Living systems employ front propagation and spatiotemporal patterns encoded in biochemical reactions for communication, self-organization and computation 1 , 2 , 3 , 4 . Emulating such dynamics in minimal systems is important for understanding physical principles in living cells 5 , 6 , 7 , 8 and in vitro 9 , 10 , 11 , 12 , 13 , 14 . Here, we report a one-dimensional array of DNA compartments in a silicon chip as a coupled system of artificial cells, offering the means to 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.