ECM Remodeling and an Abrupt, Stochastic Transition to Arrest Determine Tissue Growth Kinetics

During development, multicellular organisms undergo stereotypical patterns of tissue growth in space and time, but how this is orchestrated remains unclear. Drosophila histoblast nests are small clusters of progenitor epithelial cells that undergo extensive growth to give rise to the abdominal epidermis and are amenable to live-imaging. Our quantitative analysis of the temporal dynamics of abdomen growth reveals that histoblasts display oscillatory cell division rates and that growth termination occurs through the rapid emergence of arrested cells rather than a gradual increase in cell cycle time. By examining tissue mechanics throughout histoblast expansion, we uncover an increase in tissue stress together with a decrease in extracellular matrix resistance as the histoblasts expand. The decrease in resistance is driven by timely extracellular matrix remodeling, which is necessary to trigger tissue expansion. Thus, changes in the tissue microenvironment, and a rapid cell cycle exit, control the formation of the adult Drosophila abdomen.