Molecular characterization of defects of the central pair complex of cilia causing Primary Ciliary Dyskinesia (PCD)

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Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder characterized by chronic airway disease, randomization of left-right (LR) body asymmetry and male infertility due to defects of motile cilia/flagella function. Currently PCD diagnosis mainly depends on demonstration of ultrastructural defects of respiratory motile cilia. In contrast to most forms of PCD, defects of the central pair (CP) complex cannot be identified by conventional TEM and neither is HSVM suitable for confirming a diagnosis. Therefore PCD types with defects of the CP are difficult to diagnose.Recently we demonstrated that several forms of PCD can be diagnosed by immunofluorescence microscopy (IF). The analysis of proteins associated with the CP revealed that SPEF2 is not detectable by IF in the cilia of HYDIN mutant respiratory cells. Genetic analysis of individuals in which SPEF2 could not be detected in respiratory cilia revealed the identification of SPEF2 as PCD-causing gene as well as HYDIN mutations in additional 15 individuals.Due to the fact that the newly identified mutations in HYDIN, SPEF2 and STK36 as well as most likely in all genes encoding parts of the CP complex, do not lead to a situs inversus or situs ambiguous and that structural defects of the CP apparatus are not regularly detectable with routine TEM, additional knowledge about the composition of the CP complex is of great importance to improve PCD diagnostic procedures and patient care. The objectives of this current proposal are therefore as follows: 1. Characterization of the human CP composition including novel components of the CP complex2. Translation of the results into the clinics by development of novel diagnostic tools such as immunofluorescence (IF) microscopy to identify specific CP complex defects3. Identification and characterization of novel mutations in genes encoding elements of the CP complexes in human PCD individuals4. Functional characterization of novel CP defects using Air-liquid interface (ALI) cell culture of primary respiratory epithelial cells to study cilia morphology, ciliary beat pattern, and mucociliary transport by particle tracking analysis 5. Genotype/phenotype correlation of PCD patients with defective proteins of the CP complexFollowing this strategy we expect, that we will 1) succeed to be able to detect several CP components and also novel CP complex defects in PCD patients and 2) succeed to characterize the composition of the CP complex in human cilia and cell type specific differences in more detail. These data will improve our understanding of normal cilia biology and which will give additional insights into the pathogenesis of PCD, thus improving diagnosis and genetic counseling of affected individuals. In addition we hope that – based upon this knowledge – we will be able to develop novel therapeutic strategies for PCD.