Cellular responses in the airway ciliary microenvironment from mouse models of primary ciliary dyskinesia with central pair apparatus defects

Dysfunction of motile cilia can impair mucociliary clearance in the airway and result in primary ciliary dyskinesia (PCD), a pediatric syndrome characterized by chronic respiratory infection and bronchiectasis, as well as infertility, laterality defects, and occasionally hydrocephalus due to defects in cilia in other organ systems. We have previously shown that mutations in genes encoding components of the ciliary central pair apparatus (CPA) perturb ciliary motility and result in PCD in mouse models. However, little is known about how epithelial cell types in the ciliary microenvironment of the upper airway respond to defects in ciliary motility and mucociliary clearance. In this study, we have used a single-cell RNA sequencing (scRNA-seq) approach to investigate the effects of ciliary dysfunction on the tracheal epithelial cells from mouse models with mutations in CPA genes Cfap221 (also known as Pcdp1), Cfap54, and Spef2. Expected cell types were identified in the tracheal epithelial samples, including basal cells, suprabasal cells, secretory cells, deuterosomal cells, ciliated cells, tuft cells, ionocytes, and neuroendocrine cells, as well as an unidentified cell type that does not express markers of typical airway cells. The deuterosomal cells were found to exist in two states that differ largely in expression of genes involved in differentiation into the ciliated cell type. Differentially expressed genes (DEGs) were identified for each cell type, and functional enrichment analysis revealed a variety of important cellular functions altered in mutant cells. Overlapping DEGs shed light on general cellular responses to cilia dysfunction, while unique DEGs indicate that some responses may be specific to the individual mutation and ciliary defect. These analyses uncover new information about cellular responses to mucociliary clearance defects in the airway and pathogenesis of PCD.