Cell and nuclear scaling constrains tissue fluidity in a doubly-dense remodeling epithelium.

During epithelial remodeling, tissues exhibit solid- or fluid-like properties depending on developmental constraints. In soft matter systems like foams and colloidal glasses, component size influences material mechanics. Here, we investigated how cell and nuclear size affect tissue mechanics. mh mutant embryos have epithelia with doubled cell densities, creating cells with altered 3D aspect ratios. Nuclear volumes scale non-linearly with cell volumes, adopting rounder shapes and reduced apical-basal heights, suggesting that stiff nuclei deform less than cell cortices. These compacted nuclei resemble a jammed state, reducing tissue fluidity and impairing extension movements. Interestingly, oscillatory amplitudes and frequencies in mh cells are comparable to control despite their reduced size, demonstrating an uncoupling between biochemical oscillation machinery and cell dimensions. Additionally, though planar-polarized magnitudes are dampened, the angular assignment of interfacial behaviors is preserved, suggesting that this planar informational system still operates with high fidelity despite reduced cell dimensions. Thus, these results indicate that development has fine-tuned epithelial dimensions to work at time-scales compatible with embryonic requirements.