Clonal dominance in excitable cell networks

Clonal dominance arises when the descendants (clones) of one or a few founder cells contribute disproportionally to the final structure during collective growth 1 – 8 . In contexts such as bacterial growth, tumorigenesis and stem cell reprogramming 2 – 4 , this phenomenon is often attributed to pre-existing propensities for dominance, whereas in stem cell homeostasis, neutral drift dynamics are invoked 5 , 6 . The mechanistic origin of clonal dominance during development, where it is increasingly documented 1 , 6 – 8 , is less understood. Here, we investigate this phenomenon in the Drosophila melanogaster follicle epithelium, a system in which the joint growth dynamics of cell lineage trees can be reconstructed. We demonstrate that clonal dominance can emerge spontaneously, in the absence of pre-existing biases, as a collective property of evolving excitable networks through coupling of divisions among connected cells. Similar mechanisms have been identified in forest fires and evolving opinion networks 9 – 11 ; we show that the spatial coupling of excitable units explains a critical feature of the development of the organism, with implications for tissue organization and dynamics 1 , 12 , 13 . As tissues grow, a small fraction of cells can give rise to a large fraction of the tissue. A model borrowed from forest fires suggests that this can occur spontaneously in development as a collective property of the cell interaction network.