Decrypting the war code of cells: cell competition and fitness selection during development.
Romain Levayer, Institute for Cell Biology, University of Bern, Switzerland

The genesis of a multicellular organism is a complex process by which multiple cells acquire distinct fates and properties with highly precise time and space control. Embryogenesis requires a high robustness of developmental programs, which could partially relies on the remarkable plasticity of embryonic tissues. This is well exemplified by a process called cell competition, where a subset of viable but suboptimal cells (so called "losers") can be eliminated and replaced by the surrounding best fitted cells (so called "winners") without any consequences on the final shape of the tissue. Although this process has been characterized a long time ago in Drosophila, the molecular basis of the cell-cell communication allowing the recognition and the elimination of fitness deprived cells is not yet well understood. By combining long term live-imaging of the process as well as systematic quantification of cell elimination, we propose a model where the surface of contact between losers and winners will determine their probability to die. We will also present evidences for active mechanisms of cell-cell mixing, which accelerate loser cell elimination by increasing the surface of contact between losers and winners. These results suggest that cell topology plays a crucial role in cell-cell communication and the final outcome of cell competition.

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