Microtubule organization and molecular architecture of ciliary basal bodies in multiciliated airway cells

Microtubule organization depends on cell type and function. Microtubule networks of many differentiated cell types, such as epithelial cells, are poorly understood due to their high density. Here, we used expansion microscopy to quantitatively describe the three-dimensional organization of the microtubule network in human airway multiciliated cells. In these cells, most apical and apicobasal microtubules nucleate and anchor at the basal foot, a part of the ciliary basal body. Using a newly developed volumetric averaging tool, we generated a high-resolution 3D map of the basal body, delineating the position of structural components and proteins involved in microtubule nucleation and anchoring. γ-TuRC, its binding partners NEDD1 and Augmin/HAUS, and centriolar appendage proteins ninein and AKNA localize to the basal foot. Functional analyses demonstrated that NEDD1, but not ninein or HAUS are essential for basal foot-dependent microtubule organization. Our data reveal the distinct architecture of microtubule-organizing centers responsible for the formation of dense microtubule arrays in multiciliated cells.