Collective chemotaxis of cells with long-range communication

Cells use a variety of methods to navigate chemical gradients in order to move toward attractants or away from repellents. In addition, many cell types have been shown to improve the accuracy of their chemotaxis by acting as a collective and/or utilizing cell-cell communication, which can help reduce measurement noise. The ‘many wrongs’ model of collective migration is a well studied mechanism by which a collective tracks a gradient more precisely than an individual agent. However, when applied to cells, the many wrongs model typically assumes that cells interact via spatial contact. It remains unclear whether the benefits of cooperation can be extended to spatially separated cells that maintain such a coupling through long range communication. Using stochastic modeling and agent-based simulation, we study such an extension in which the cells communicate using a combination of secreted attractor and repulsor molecules. Surprisingly, we find that the accuracy of chemotaxis is optimized not when cells are tightly packed, but rather when cells are spaced at a nonzero average nearest-neighbor distance, resulting in a sparsely packed swarm. We discuss the mechanism behind the sparse packing and the implications for collective chemotaxis.