Super-Resolution Mapping of Basal Foot and the Characterization of a Novel Cilium in Human Airway Multiciliated Cells

During ciliogenesis, mother centriole-specific subdistal appendages undergo structural changes to become basal feet. This supramolecular assembly anchors the basal body to the microtubule cytoskeleton thereby regulating signaling in primary cilia and beating coordination in motile cilia. In mice, loss of the basal foot causes symptoms consistent with those observed in patients with Primary Ciliary Dyskinesia (PCD), an inherited lung disease. Despite its importance, the molecular structure of the basal foot remains to be characterized: its size is below the diffraction limit of conventional fluorescence microscopy and it is too large to be studied in vitro. By combining 3DSIM super-resolution microscopy, Electron Microscopy, and a novel tag-insertion mapping strategy, we discovered that the basal foot has a modular architecture conserved across different cilia. Moreover, we identified a new type of cilium in airway epithelial multiciliated cells with a potential mechanosensory role.