Basal Cell-Contact Dynamics Influence Tissue Packing in a Proliferating Mammalian Epithelium.

Animal tissue morphology is determined by the shape, position, and proliferative capacity of individual epithelial cells. Nevertheless, it remains incompletely understood how the dynamic shape transformations implicit in mitotic proliferation influence tissue packing, particularly at the level of basal cell contacts. Here, we use an in silico vertex model to show that epithelial mitotic rounding necessitates a sequence of dynamic basal contact rearrangements, including basal diminution of the mitotic cell volume, transient multicellular rosette assembly, basal reinsertion of daughter cells, and neighbor reorganization. We then leverage a mammalian intestinal organoid model to confirm nearly identical basal cell-contact dynamics as those predicted in silico. Pharmacological inhibition of mitotic progression reveals that two events-basal diminution of the cell body and daughter cell reinsertion-independently drive distinct contact rearrangements. Together, our results uncover a previously underappreciated topological role for basal mitotic cell dynamics in shaping epithelial packing and morphogenesis.