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

Overview

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 complexity and high density. Here, we used expansion microscopy to visualize and quantitatively map 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. A small subset of stable microtubules is detached from basal bodies and forms an apical crescent. By combining expansion microscopy with a newly developed averaging tool for multichannel volumetric data, we generated a high-resolution 3D map of the basal body. We delineated the position of structural components and proteins involved in microtubule nucleation and anchoring, uncovering some interesting differences with centrioles of dividing cells. 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 is 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.