Molecular characterization of DNAH11-associated primary ciliary dyskinesia: a globally significant but underreported diagnosis due to normal ciliary ultrastructure

• Applicant: Professor Dr. Heymut Omran
• Subject Area: Pediatric and Adolescent Medicine ; Human Genetics ; Cell Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555746761

Primary Ciliary Dyskinesia (PCD) is characterized by dyskinetic ciliary beating, particularly in the airways. The resulting decreased mucociliary clearance leads to chronic upper and lower respiratory tract infections, permanent lung damage (bronchiectasis) and decrease in lung function. A PCD diagnosis is supported by tests demonstrating airway cilia defect and identification of pathogenic variants in PCD associated genes (currently >50). DNAH11 mutations are a common but underdiagnosed cause of primary ciliary dyskinesia (PCD). Traditionally, a PCD diagnosis has been made by electron microscopy examination. However, our group demonstrated for the first time that DNAH11 mutations cause PCD with normal ultrastructure (Schwabe et al. 2008). By demonstrating a hyperkinetic ciliary beat pattern in DNAH11-mutant cilia using high-frequency video-microscopic analysis (HSVM), we could introduce a method for PCD diagnosis. However, HSVM shows only subtle abnormalities and is not widely available. More than 30 of the >50 known genetic defects for PCD have been identified by our research group (Wallmeier et al. 2020). Therefore, in the presence of pronounced genetic heterogeneity, genetic diagnostics come to the fore. However, genetic diagnostics for DNAH11 (82 exons) are hampered by the lack of functional tests to evaluate variants with unclear pathogenicity and/or the failure to identify the second disease-causing allele. Therefore, DNAH11 cases are likely underdiagnosed and require additional investigation at the protein and gene levels. However, a recent gene database analysis shows that DNAH11 is the most commonly affected PCD gene in most ethnicities (Hannah et al. 2022). The goal of this project is to establish immunofluorescence microscopy as a supportive diagnostic test to confirm the genetic diagnosis of PCD caused by DNAH11 mutations (Dougherty et al. 2016). It is particularly important to validate potentially disease-causing variants of unknown significance at the protein level to confirm the genetic diagnosis. Furthermore, we aim to analyze mucociliary clearance in detail using particle transport analyses on air-liquid-interface cultures from affected individuals. By means of protein chemical analyses (mass-spec and co-IPs) we will identify further interaction partners (Dougherty et al. 2020) to understand the cellular pathogenetic mechanisms. Using modern sequencing techniques, we will identify deep intronic DNAH11 mutations as well as mutations in genes encoding interaction partners that we have identified. Our genetic (hypomorphic vs. loss-of-function), cellular (e.g. DNAH11 and DNAH9 mislocalization) and functional (HSVM and ciliary particle transport analysis) data will be correlated with detailed clinical data from the international ERN-LUNG PCD core registry to comprehensively understand the disease picture. We expect that the results of this project will significantly improve the genetic diagnosis of PCD caused by DNAH11 dysfunction.

• DFG Programme: Research Grants