Primary ciliary dyskinesia (PCD) is a recessive, genetically heterogeneous disorder with defective mucociliary clearance. This ongoing project is designed to identify additional disease-causing mutations in PCD using whole exome sequencing, and then to correlate the molecular etiologies with the ciliary phenotype (ultrastructure, wave form and beat frequency), production of nasal nitric oxide in vivo, and clinical phenotype. We have robust preliminary data that discrete sets of genes contribute to the structure and function of the ciliary outer dynein arm (ODA), inner dynein arm (IDA), and central pair (CP) and radial spokes (RS). For patients with these ciliary ultrastructural (electron microscopic, EM) defects, nasal nitric oxide (nNO) production is uniformly low (~ 20 ml/min), including patients with mutations we recently discovered by exome sequencing in novel genes that cause ODA defects (CCDC114) or ODA+IDA defects (SPAG1; HEATR2; LRRC6; & ZMYND10). We are now identifying an increasing number of PCD patients with normal ciliary ultrastructure (up to 31% of PCD patients at UNC) and 50% of those patients have biallelic mutations in DNAH11, RSPH4A, or two novel genes we recently discovered (RSPH1 & CCDC65). Over the past 3 years, we have made great progress in identifying mutations in 15 genes that cause ~60% of PCD, but we need to identify the remaining major PCD-causing genes. We are now whole exome sequencing 100 additional patients (NIH 1X0101HL115246-01 grant) by an NHLBI-supported sequencing center (Yale; Dr. R. Lifton). This exome sequencing project will extend our search for disease-causing mutations by including patients who have a PCD-compatible clinical phenotype, but with nNO values that are higher than typical for PCD patients with ciliary EM defects. Followup studies will be performed at UNC to validate novel gene discoveries, and characterize gene/protein expression and function in human ciliated airway cells. Taken together, these studies will provide new insights regarding the relationship of mutations in novel genes to ciliary ultrastructural and functional defects. These studies will not only greatly enhance our ability to diagnose PCD, but will also lead to discovery of milder genetic mutations associated with normal ciliary ultrastructure and likely some residual ciliary function. Ultimately, this will allow development of clinical genetic testing for PCD, and future studies of the role of partial loss of ciliary function in the predisposition to moe common airways diseases, such as chronic obstructive pulmonary disease.