Ciliary movement analysis in primary ciliary dyskinesia with a long deletion in DRC1

<bold>Background:</bold> A long deletion in the <italic>DRC1</italic> gene is one of the common genetic variants observed in primary ciliary dyskinesia (PCD) in Japan. Approximately 49% of PCD cases in Japan are reported to have <italic>DRC1</italic> long deletions (Takeuchi K, et al. Mol Genet Genomic Med. 2020;8(3):e1137.) <bold>Objective:</bold> We analysed the ciliary movements of cultured respiratory epithelial cells obtained from patients with PCD who had <italic>DRC1</italic>-long deletions. <bold>Methods:</bold> Respiratory epithelial cells were obtained using a cytology brush from the nasal or bronchial walls of four patients with PCD and several controls without PCD. Written informed consent was obtained from all study subjects before sample collection, and the study was approved by our institution’s ethics committee. Following air-liquid interface culturing, the ciliary movements of the cells were observed using high-speed video analysis. <bold>Result:</bold> The average ciliary stroke angle was 40.9 ± 13.2° in patients with <italic>DRC1</italic> long deletions, and 91 ± 17.5° in the controls. The ciliary beat frequency (CBF) ranged between 4.8 and 31.8 Hz, with an average of 16.3 ± 10.8 Hz in patient 1 and 16.9 ± 9.6 Hz in patient 2 (both with <italic>DRC1</italic> long deletions). In a control patient without PCD, CBF ranged between 10.3 and 14.1 Hz, with an average of 12.5 ± 1.2 Hz. <bold>Conclusion:</bold> Ciliary movement was less flexible and had a smaller amplitude, with a greater degree of CBF variation, in patients with <italic>DRC1</italic> long deletions. We believe that this may reduce mucociliary transport. Understanding ciliary movement in cases of PCD with <italic>DRC1</italic> long deletions may deepen the general understanding of this disease and aid in the development of new treatment approaches.