Failure of airway clearance is a characteristic feature of chronic airway disorders. Evidence that an intact mucociliary apparatus is essential for clearance derives from studies of genetic disease of cilia as well as reports that cilia dysfunctio may contribute to chronic obstructive pulmonary disease (COPD) and asthma. Comprehensive collections of ciliary genes and proteins have contributed to the rapid pace of progress in the identification of genetic etiologies of the syndrome of motile cilia dysfunction, called primary ciliary dyskinesia (PCD). However, there are no specific therapies for this disease that ultimately progresses to bronchiectasis. Here, we address a key set of questions to gain a more complete understanding of the assembly and regulation of motile cilia. Using novel genes mutated in PCD as a guide, we have uncovered specific regulatory steps that are critical for the assembly of motile cilia and offer the prospect of therapeutic intervention to augment ciliogenesis. Our preliminary data define a pathway for motile ciliogenesis that (i) commences at the earliest point of motor protein preassembly in the cytoplasm controlled by HEATR2, (ii) is functionally linked to a network that traffics protein from the cytoplasm to the basal bodies and motile cilia regulated by CCDC11, and (iii) requires the proteins CCDC39 and CCDC40 to establish the proper organization of motors and microtubules within the motile cilium. We show that mutation or depletion of each of these molecular linchpins results in unsuccessful motile cilia biogenesis and function as expected. We also uncover tractable mechanisms at each point of the pathway that we show are modified by the genetic disruption of novel suppressor genes to remediate cilia defects. Our preliminary and proposed studies take advantage of complementary models of primary multiciliated human airway epithelial cells, genetically deficient strains of zebrafish and the alga Chlamydomonas, which together provide in vitro and in vivo analysis and rapid genetic manipulation of cilia assembly pathways. Using these strategies, we will probe the assembly, trafficking and activity of dynein motor assembly in the following aims: (1) Identify the preassembly pathways required for dynein motor protein complex delivery; (2) Identify the regulation of motor protein trafficking from basal bodies to cilia; (3) Identify genes that can restore function to cells lacking docking and assembly factors for the motor proteins. We propose that manipulation of these pathways will offer possibilities of devising molecular therapies for defects in motile cilia.
Clearance of pathogens and particulates from the airway is an essential function for host defense, and dependent on the actions of beating of cilia. Failed ciliary function results in lung infection and the development of chronic lung disease. We identify key mechanisms for the assembly of motile cilia that provide critical points of regulation that can be modified as targets for therapy of lung disease associated with defective cilia.
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