Zebrafish Ciliopathy Screen Plus Human Mutational Analysis Identifies C21orf59 and CCDC65 Defects as Causing Primary Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is caused when defects of motile cilia lead to chronic airway infections, male infertility, and situs abnormalities. Multiple causative PCD mutations account for only 65% of cases, suggesting that many genes essential for cilia function remain to be discovered. By using zebrafish morpholino knockdown of PCD candidate genes as an in vivo screening platform, we identified c21orf59, ccdc65, and c15orf26 as critical for cilia motility. c21orf59 and c15orf26 knockdown in zebrafish and planaria blocked outer dynein arm assembly, and ccdc65 knockdown altered cilia beat pattern. Biochemical analysis in Chlamydomonas revealed that the C21orf59 ortholog FBB18 is a flagellar matrix protein that accumulates specifically when cilia motility is impaired. The Chlamydomonas ida6 mutant identifies CCDC65/FAP250 as an essential component of the nexin-dynein regulatory complex. Analysis of 295 individuals with PCD identified recessive truncating mutations of C21orf59 in four families and CCDC65 in two families. Similar to findings in zebrafish and planaria, mutations in C21orf59 caused loss of both outer and inner dynein arm components. Our results characterize two genes associated with PCD-causing mutations and elucidate two distinct mechanisms critical for motile cilia function: dynein arm assembly for C21orf59 and assembly of the nexin-dynein regulatory complex for CCDC65

Mutation of Growth Arrest Specific 8 Reveals a Role in Motile Cilia Function and Human Disease

Ciliopathies are genetic disorders arising from dysfunction of microtubule-based cellular appendages called cilia. Different cilia types possess distinct stereotypic microtubule doublet arrangements with non-motile or ‘primary’ cilia having a 9+0 and motile cilia have a 9+2 array of microtubule doublets. Primary cilia are critical sensory and signaling centers needed for normal mammalian development. Defects in their structure/function result in a spectrum of clinical and developmental pathologies including abnormal neural tube and limb patterning. Altered patterning phenotypes in the limb and neural tube are due to perturbations in the hedgehog (Hh) signaling pathway. Motile cilia are important in fluid movement and defects in motility result in chronic respiratory infections, altered left-right asymmetry, and infertility. These features are the hallmarks of Primary Ciliary Dyskinesia (PCD, OMIM 244400). While mutations in several genes are associated with PCD in patients and animal models, the genetic lesion in many cases is unknown. We assessed the in vivo functions of Growth Arrest Specific 8 (GAS8). GAS8 shares strong sequence similarity with the Chlamydomonas Nexin-Dynein Regulatory Complex (NDRC) protein 4 (DRC4) where it is needed for proper flagella motility. In mammalian cells, the GAS8 protein localizes not only to the microtubule axoneme of motile cilia, but also to the base of non-motile cilia. Gas8 was recently implicated in the Hh signaling pathway as a regulator of Smoothened trafficking into the cilium. Here, we generate the first mouse with a Gas8 mutation and show that it causes severe PCD phenotypes; however, there were no overt Hh pathway phenotypes. In addition, we identified two human patients with missense variants in Gas8. Rescue experiments in Chlamydomonas revealed a subtle defect in swim velocity compared to controls. Further experiments using CRISPR/Cas9 homology driven repair (HDR) to generate one of these human missense variants in mice demonstrated that this allele is likely pathogenic

In Situ Localization of N and C Termini of Subunits of the Flagellar Nexin-Dynein Regulatory Complex (N-DRC) Using SNAP Tag and Cryo-electron Tomography

Cryo-electron tomography (cryo-ET) has reached nanoscale resolution for in situ three-dimensional imaging of macromolecular complexes and organelles. Yet its current resolution is not sufficient to precisely localize or identify most proteins in situ; for example, the location and arrangement of components of the nexin-dynein regulatory complex (N-DRC), a key regulator of ciliary/flagellar motility that is conserved from algae to humans, have remained elusive despite many cryo-ET studies of cilia and flagella. Here, we developed an in situ localization method that combines cryo-ET/subtomogram averaging with the clonable SNAP tag, a widely used cell biological probe to visualize fusion proteins by fluorescence microscopy. Using this hybrid approach, we precisely determined the locations of the N and C termini of DRC3 and the C terminus of DRC4 within the three-dimensional structure of the N-DRC in Chlamydomonas flagella. Our data demonstrate that fusion of SNAP with target proteins allowed for protein localization with high efficiency and fidelity using SNAP-linked gold nanoparticles, without disrupting the native assembly, structure, or function of the flagella. After cryo-ET and subtomogram averaging, we localized DRC3 to the L1 projection of the nexin linker, which interacts directly with a dynein motor, whereas DRC4 was observed to stretch along the N-DRC base plate to the nexin linker. Application of the technique developed here to the N-DRC revealed new insights into the organization and regulatory mechanism of this complex, and provides a valuable tool for the structural dissection of macromolecular complexes in situ

Predicting clinical outcomes after radical nephroureterectomy for upper tract urothelial carcinoma.

International audienceBACKGROUND: Novel prognostic factors for patients after radical nephroureterectomy (RNU) for upper tract urothelial carcinoma (UTUC) have recently been described. OBJECTIVE: We tested the prognostic value of pathologic characteristics and developed models to predict the individual probabilities of recurrence-free survival (RFS) and cancer-specific survival (CSS) after RNU. DESIGN, SETTING, AND PARTICIPANTS: Our study included 2244 patients treated with RNU without neoadjuvant or adjuvant therapy at 23 international institutions. Tumor characteristics included T classification, grade, lymph node status, lymphovascular invasion, tumor architecture, location, and concomitant carcinoma in situ (CIS). The cohort was randomly split for development (12 centers, n=1273) and external validation (11 centers, n=971). INTERVENTIONS: All patients underwent RNU. MEASUREMENTS: Univariable and multivariable models addressed RFS, CSS, and comparison of discrimination and calibration with American Joint Committee on Cancer (AJCC) stage grouping. RESULTS AND LIMITATIONS: At a median follow-up of 45 mo, 501 patients (22.3%) experienced disease recurrence and 418 patients (18.6%) died of UTUC. On multivariable analysis, T classification (p for trend <0.001), lymph node metastasis (hazard ratio [HR]: 1.98; p=0.002), lymphovascular invasion (HR: 1.66; p<0.001), sessile tumor architecture (HR: 1.76; p<0.001), and concomitant CIS (HR: 1.33; p=0.035) were associated with disease recurrence. Similarly, T classification (p for trend<0.001), lymph node metastasis (HR: 2.23; p=0.001), lymphovascular invasion (HR: 1.81; p<0.001), and sessile tumor architecture (HR: 1.72; p=0.001) were independently associated with cancer-specific mortality. Our models achieved 76.8% and 81.5% accuracy for predicting RFS and CSS, respectively. In contrast to these well-calibrated models, stratification based upon AJCC stage grouping resulted in a large degree of heterogeneity and did not improve discrimination. CONCLUSIONS: Using standard pathologic features, we developed highly accurate prognostic models for the prediction of RFS and CSS after RNU for UTUC. These models offer improvements in calibration over AJCC stage grouping and can be used for individualized patient counseling, follow-up scheduling, risk stratification for adjuvant therapies, and inclusion criteria for clinical trials

PCD patient missense mutations in highly conserved regions of Gas8.

<p>(A) Sanger Sequence trace and amino acid sequence of human mutations. (B) ClustalOmega amino acid alignment indicates the high conservation of the missense mutant residues found in patients which are indicated by black boxes.</p

A391V is a potential pathogenic allele.

<p>(A) Sanger Sequence confirmation of the 1172 C>T point mutation in Gas8^AV mice reproducing the A391V missense mutation found in the human patient. (B) Ciliary beat frequency analysis on tracheal cilia of Gas8^GT/WT and Gas8^GT/AV mice shows no difference between controls and compound heterozygotes (n = 86 points from 3 trachea for Gas8^GT/WT (13.04 Hz), n = 76 points from 3 tracheas for Gas8^GT/AV (13.34 Hz)). (C) Tracking of red fluorescent latex beads added to lateral ventricles shows a trending but not significant decrease in ability of Gas8^GT/AV cilia to move fluid. (n = 3 for Gas8^GT/WT (163.7μm/sec), n = 2 for Gas8^GT/AV (135.9μm/sec)). (D) Nissl stained brains of 10 week old Gas8^GT/WT, Gas8^WT/AV, and Gas8^GT/AV mice. Mild to moderate hydrocephalus is present in the Gas8^GT/AV brains. Scale is 1mm (Arrowhead indicates mild, arrow indicates moderate) (n = 4). (E) Swim speed quantification of rescue of DRC4-D198K construct in <i>pf2</i> deficient <i>Chlamydomonas</i>. “<i>pf2</i>” denotes <i>pf2</i> deficient <i>Chlamydomonas</i>, “DK-GFP” denotes <i>pf2</i> deficient <i>Chlamydomonas</i> expressing the DRC4-D198K-GFP construct, “DRC4-GFP” denotes <i>pf2</i> deficient <i>Chlamydomonas</i> expressing the DRC4-GFP wild-type construct. * = significant difference from WT (p<0.05), # = significant difference from <i>pf2</i> (p<0.05), § = significant difference between DK-GFP and DRC4-GFP (p<0.05) (n = 390 for WT (123.9μm/sec), n = 271 for <i>pf2</i> (40.1μm/sec), n = 180 for DK-GFP (108.3μm/sec), n = 299 for DRC4-GFP (120.9μm/sec)).</p