Conditional Deletion of Dnaic1 as a Model of Primary Ciliary Dyskinesia

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DESCRIPTION (provided by applicant): Primary ciliary dyskinesia (PCD) is a rare disorder that causes pulmonary disease and is usually inherited in an autosomal recessive manner. PCD is caused by mutations in proteins that impair the ability of cilia to function property. In the airway, this results in absent or reduced mucociliary clearance, that in turn leads to chronic and recurrent infections of the respiratory system. Patients with PCD typically exhibit chronic rhinitis/sinusitis, recurrent otitis media, and bronchitis. Recent work has identified mutations in two ciliary proteins, DNAI1 and DNAH5, which together account for the disease in about 20% of the patients analyzed. However, while these recent studies have begun to unravel the genetics of this multi-allelic disease, there are still many questions regarding disease pathogenesis that remain unanswered. Primary among these is the mechanism responsible for the extremely low levels of exhaled nasal nitric oxide (NO) observed in PCD patients, and the role this drastically reduced level of NO plays in disease pathogenesis. In part, the lack of information available concerning PCD is due to the lack of a suitable model system. This is largely the result of three major limitations. First, PCD is a disease of ciliated cells, and as these cells are terminally differentiated, there are no cell lines available to study PCD. Second, PCD is by definition a rare disease, and the frequency and quantity of human tissue that may be obtained is extremely limited. And finally, in the available animal models of PCD, the animals develop hydrocephalus, making them unsuitable for studying pulmonary disease. The primary goal of this proposal is to develop a viable murine model of human PCD by using an inducible CreER/loxP system to introduce a deletion into the murine homologue of the human gene DNAI1. The CreER/loxP system will allow the induction of the PCD phenotype in mice after the time period during which hydrocephalus develops. To develop a mouse model for the human disease PCD, the following specific aims are proposed: Specific aim 1. To generate a model of Primary Ciliary Dvskinesia by conditional deletion of Dnaid. Specific aim 2a. To measure the effect of Dnaid deletion on ciliary structure, ciliary beat frequency. mucociliary clearance, exhaled nitric oxide, and susceptibility to bacterial infection in Dnaid null mice. Specific aim 2b. To determine if mice heterozygous for Dnaid deletion have reduced numbers of outer dynein arms, impaired ciliary function and clearance, reduced levels of exhaled nitric oxide, and increased susceptibility to bacterial infection. By creating a mouse model for the disease PCD, it will be possible to study in depth many key questions regarding the pathogenesis and possible treatments of PCD. If successful, this model will also provide a novel system to investigate other questions concerning pulmonary health and disease.