Chibby functions to preserve normal ciliary morphology through the regulation of intraflagellar transport in airway ciliated cells

Airway cilia provide the coordinated motive force for mucociliary transport, which prevents the accumulation of mucus, debris, pollutants, and bacteria in our respiratory tracts. As airway cilia are constantly exposed to the environment and, hence, are an integral component of the pathogenesis of several congenital and chronic pulmonary disorders, it is necessary to understand the molecular mechanisms that control ciliated cell differentiation and ciliogenesis. We have previously reported that loss of the basal body protein Chibby (Cby) results in chronic upper airway infection in mice due to a significant reduction in the number of airway cilia. In the present work, we demonstrate that Cby is required for normal ciliary structure and proper distribution of proteins involved in the bidirectional intraflagellar transport (IFT) system, which consists of 2 distinct sub-complexes, IFT-A and IFT-B, and is essential for ciliary biogenesis and maintenance. In fully differentiated ciliated cells, abnormal paddle-like cilia with dilated ciliary tips are observed in Cby-/- airways and primary cultures of mouse tracheal epithelial cells (MTECs). In addition, IFT88, an IFT-B sub-complex protein, robustly accumulates within the dilated tips of both multicilia in Cby-/- MTECs and primary cilia in Cby-/- mouse embryonic fibroblasts (MEFs). Furthermore, we show that only IFT-B components, including IFT20 and IFT57, but not IFT-A and Bardet-Biedl syndrome (BBS) proteins, amass with IFT88 in these distended tips in Cby-/- ciliated cells. Taken together, our findings suggest that Cby plays a role in the proper distribution of IFT particles to preserve normal ciliary morphology in airway ciliated cells.