Fitness of cell colonies to navigate obstacles*

We confront confluent epithelial cells with the need to adapt from wide-channel to narrow-channel growth. Upconversion from single cell, the colony self-organizes to facilitate migration with greater efficiency than that would be accomplished by fluid hydrodynamics. This is traced to long-range mechanical signaling. Stretched leader cells trigger acceleration of the whole group; the resulting velocity difference, in turn, reinforces stretching of the leaders and establishes positive feedback between cell morphology and mechanical strength, as we confirm by direct visualization of F-actin expression, cadherin localization, and the shapes of cells and their nuclei. The relevance is to show how mechanical signaling promotes a 'smart' group navigation strategy in which adaptations of individual cells to the local environment propagate over long distances to benefit the whole colony.