3D nanoscale reconstruction of human airway multiciliogenesis reveals cellular architecture remodeling and cilia-mitochondria link via rootlets.
A central challenge in single-cell biology is understanding how molecular programs drive changes in cellular architecture that enable specialized function. A striking example of cellular remodeling is the differentiation of airway stem cells into the respiratory multiciliated epithelium, a protective tissue barrier that clears inhaled pathogens and particulate matter. Here, we present its first three-dimensional nanometer-scale reconstruction, revealing coordinated changes in cellular organization, organelle topology, and inter-organelle contacts during multiciliogenesis. We uncover a structural and functional association between motile cilia and mitochondria mediated by rootlets, striated cytoskeletal fibers that remain poorly characterized in human airway multiciliated cells. Rootlets connect to basal bodies through a multiprotein linker containing the uncharacterized rootletin/CROCC homolog CROCC2, oscillate at frequencies comparable to ciliary beating, promote basal body alignment, and when lost, reduce maximal mitochondrial respiratory capacity. Altogether, this work integrates structural, dynamic, and functional analyses to elucidate mechanisms underlying airway mucociliary defense.