Mutation ofCFAP57causes primary ciliary dyskinesia by disrupting the asymmetric targeting of a subset of ciliary inner dynein arms

Abstract

word count: 247 Text word count, without methods: 3856 Abstract (247/ 250 words)Primary ciliary dyskinesia (PCD) is characterized by chronic airway disease, male infertility, and randomization of the left/right body axis, and is caused by defects of motile cilia and sperm flagella. We screened a cohort of affected individuals that lack an obvious TEM structural phenotype for pathogenic variants using whole exome capture and next generation sequencing. The population sampling probability (PSAP) algorithm identified one subject with a homozygous nonsense variant [(c.1762C>T) p.(Arg588*) exon 11] in the uncharacterized CFAP57 gene. In normal human nasal epithelial cells, CFAP57 localizes throughout the ciliary axoneme. Analysis of cells from the PCD patient shows a loss of CFAP57, reduced beat frequency, and an alteration in the ciliary waveform. Knockdown of CFAP57 in human tracheobronchial epithelial cells (hTECs)recapitulates these findings. Phylogenetic analysis showed that CFAP57 is conserved in organisms that assemble motile cilia, and CFAP57 is allelic with the BOP2 gene identified previously in Chlamydomonas. Two independent, insertional fap57Chlamydomonas mutant strains show reduced swimming velocity and altered waveforms. Tandem mass spectroscopy showed that CFAP57 is missing, and the "g" inner dyneins (DHC7 and DHC3) and the "d" inner dynein (DHC2) are reduced. Our data demonstrate that the FAP57 protein is required for the asymmetric assembly of inner dyneins on only a subset of the microtubule doublets, and this asymmetry is essential for the generation of an effective axonemal waveform. Together, our data identifies mutations in CFAP57 as a cause of PCD with a specific defect in the inner dynein arm assembly process. Significance (119/120 words)Motile cilia are found throughout eukaryotic organisms and performs essential functions.Primary ciliary dyskinesia (PCD) is a rare disease that affects the function of motile cilia.By applying a novel population sampling probability algorithm (PSAP) that uses large population sequencing databases and pathogenicity prediction algorithms, we identified a variant in an uncharacterized gene, CFAP57. This is the first reported example of PCD caused by a mutation that affects only a subset of the inner dynein arms, which are needed to generate the waveform. CFAP57 identifies an address for specific dynein arms. These findings demonstrate the effectiveness of the PSAP algorithm, expand our understanding of the positioning of dynein arms, and identify mutations in CFAP57 as a cause of PCD.

Implementation of multigene panel NGS diagnosis in the national primary ciliary dyskinesia cohort of Cyprus: An island with a high disease prevalence

“…The main limitation of our study is the PCD genes that are not part of the panel either because they were identified in the last two years and were not incorporated in the multigene panel or are yet unknown. The genes identified during the last two years include CFAP57 (Bustamante‐Marin et al, 2019), CFAP221 (Bustamante‐Marin et al, 2020), NEK10 (Chivukula et al, 2020), NME5 (Cho et al, 2020), LRRC56 (Bonnefoy et al, 2018), TTC12 (Thomas et al, 2020), DNAH9 (M. R. Fassad, Shoemark, Legendre et al, 2018), FOXJ1 (Wallmeier et al, 2019), and GAS2L2 (Bustamante‐Marin et al, 2019). Due to significant pseudogene interference, we also did not perform a comprehensive analysis of the HYDIN gene and only exons 1–5 were assessed.…”

FAP57/WDR65 targets assembly of a subset of inner arm dyneins and connects to regulatory hubs in cilia

“…We suggest that FAP57/WDR65 should be screened as a candidate gene for those patients with PCD whose mutations have not been identified in the more commonly known PCD loci. Indeed, recent work has indicated that a FAP57/WDR65 mutation has been linked to disease in one patient with PCD (Bustamante-Marin et al , 2019).…”

Whole-exome sequencing accuracy in the diagnosis of primary ciliary dyskinesia

“…Moreover, mutations may have been missed due to the calling algorithms used for analysis. Future re-analysis using improved algorithms and use of exome trios may allow the identification of additional disease-causing mutations [ 41 ].…”