Loss of Cilia Maintenance in Acquired and Genetic Lung Diseases

Summary Multiciliated cells containing hundreds of motile cilia line the airway to generate directional fluid flow essential for mucociliary clearance. Despite stressful environmental conditions, the half-life of multiciliated cells is long, on the order of 6-12 months. This long lifespan dictates that there must be strict maintenance programs for preserving cilia ultrastructure, length, motility, and functions required to provide continuous airway clearance. We propose that loss of cilia maintenance results in acquired ciliopathies featuring short or absent cilia, slowed motility, and impaired airway clearance observed in lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), and others. While much has been learned about genetic ciliary diseases, little is known about the cellular processes resulting in acquired airway ciliopathies. Our preliminary data shows that in airway tissues from patients with asthma and COPD, there is loss of cilia that surprising features uncoupling of BB proteins from their normal positions beneath cilia, and their translocation to the cytoplasm. We observed the same displacement of BB proteins to the cytoplasm suggesting loss of cilia maintenance in a mouse model of asthma, and in human airway epithelial cell cultures that were treated with inflammatory stimuli. To investigate the role of BB in regulation of cilia maintenance, we have conditionally deleted ciliopathy protein Cep120, which is essential for BB function during homeostasis, in multiciliated cells of adult mice with fully developed airways. Cep120 loss results in derangement of BB position and cilia structure similar to that observed in disease tissues. By tracking the loss of cilia in human tissues and mouse models, we identify that BB proteins accumulate in unique cytoplasmic degradation sites near the BB marked by autophagy and proteosome components. Collectively, our preliminary results suggest that acquired ciliopathies are due to disrupted BB function in mature multiciliated cells. Thus, we hypothesize that basal body functions are required for motile cilia maintenance in health, and that loss of BB proteins leads to cilia disassembly in acquired ciliopathies. This hypothesis will be tested in vitro and in vivo using a combination of genetic mouse models, multiciliated cell cultures of primary mouse and human cells, and airway disease patient-derived tissues. Our complementary Specific Aims will: (1) Identify changes in basal body proteins affecting cilia in acquired ciliopathies of chronic lung disease; and (2) Define the basal body mechanisms that maintain cilia during steady state in health. Loss of candidate BB proteins prior to cilia dysfunction in human diseased lung tissues and mouse models will support our hypothesis that cilia maintenance is dependent on BB, and that acquired ciliopathies are the result of failed BB functions. Our studies will define the novel role of the basal body in acquired ciliopathies, and provide new unique targets for maintenance of motile cilia and their functions in human lung diseases.