Nephronophthisis-related ciliopathies (NPHP-RC) are degenerative recessive diseases that affect kidney, retina, and brain. Genetic defects in NPHP gene products that localize to cilia and centrosomes defined them as "ciliopathies." However, disease mechanisms remain poorly understood. Here, we identify by whole-exome resequencing, mutations of MRE11, ZNF423, and CEP164 as causing NPHP-RC. All three genes function within the DNA damage response (DDR) pathway. We demonstrate that, upon induced DNA damage, the NPHP-RC proteins ZNF423, CEP164, and NPHP10 colocalize to nuclear foci positive for TIP60, known to activate ATM at sites of DNA damage. We show that knockdown of CEP164 or ZNF423 causes sensitivity to DNA damaging agents and that cep164 knockdown in zebrafish results in dysregulated DDR and an NPHP-RC phenotype. Our findings link degenerative diseases of the kidney and retina, disorders of increasing prevalence, to mechanisms of DDR.

Chronic kidney disease (CKD) represents a major health burden. Its central feature of renal fibrosis is not well understood. By exome sequencing, we identified mutations in FAN1 as a cause of karyomegalic interstitial nephritis (KIN), a disorder that serves as a model for renal fibrosis. Renal histology in KIN is indistinguishable from that of nephronophthisis, except for the presence of karyomegaly. The FAN1 protein has nuclease activity and acts in DNA interstrand cross-link (ICL) repair within the Fanconi anemia DNA damage response (DDR) pathway. We show that cells from individuals with FAN1 mutations have sensitivity to the ICL-inducing agent mitomycin C but do not exhibit chromosome breakage or cell cycle arrest after diepoxybutane treatment, unlike cells from individuals with Fanconi anemia. We complemented ICL sensitivity with wild-type FAN1 but not with cDNA having mutations found in individuals with KIN. Depletion of fan1 in zebrafish caused increased DDR, apoptosis and kidney cysts. Our findings implicate susceptibility to environmental genotoxins and inadequate DNA repair as novel mechanisms contributing to renal fibrosis and CKD.

Rare single-gene disorders cause chronic disease. However, half of the 6000 recessive single gene causes of disease are still unknown. Because recessive disease genes can illuminate, at least in part, disease pathomechanism, their identification offers direct opportunities for improved clinical management and potentially treatment. Rare diseases comprise the majority of chronic kidney disease (CKD) in children but are notoriously difficult to diagnose. Whole-exome resequencing facilitates identification of recessive disease genes. However, its utility is impeded by the large number of genetic variants detected. We here overcome this limitation by combining homozygosity mapping with whole-exome resequencing in 10 sib pairs with a nephronophthisis-related ciliopathy, which represents the most frequent genetic cause of CKD in the first three decades of life. In 7 of 10 sibships with a histologic or ultrasonographic diagnosis of nephronophthisis-related ciliopathy, we detect the causative gene. In six sibships, we identify mutations of known nephronophthisis-related ciliopathy genes, while in two additional sibships we found mutations in the known CKD-causing genes SLC4A1 and AGXT as phenocopies of nephronophthisis-related ciliopathy. Thus, whole-exome resequencing establishes an efficient, noninvasive approach towards early detection and causation-based diagnosis of rare kidney diseases. This approach can be extended to other rare recessive disorders, thereby providing accurate diagnosis and facilitating the study of disease mechanisms.

Background The objective was to explore the efficacy of ablation lesion sets in addition to pulmonary vein isolation ( PVI ) for paroxysmal atrial fibrillation. The optimal strategy for catheter ablation of paroxysmal atrial fibrillation is debated. Methods and Results The SMASH-AF (Systematic Review and Meta-analysis of Ablation Strategy Heterogeneity in Atrial Fibrillation) study cohort includes trials and observational studies identified in PubMed, Scopus, and Cochrane databases from January 1 1990, to August 1, 2016. We included studies reporting single procedure paroxysmal atrial fibrillation ablation success rates. Exclusion criteria included insufficient reporting of outcomes, ablation strategies that were not prespecified and uniform, and a sample size of fewer than 40 patients. We analyzed lesion sets performed in addition to PVI ( PVI plus) using multivariable random-effects meta-regression to control for patient, study, and procedure characteristics. The analysis included 145 total studies with 23 263 patients ( PVI- only cohort: 115 studies, 148 treatment arms, 16 500 patients; PVI plus cohort: 39 studies; 46 treatment arms, 6763 patients). PVI plus studies, as compared with PVI -only studies, included younger patients (56.7 years versus 58.8 years, P=0.001), fewer women (27.2% versus 32.0% women, P=0.002), and were more methodologically rigorous with longer follow-up (29.5 versus 17.1 months, P 0.004) and more randomization (19.4% versus 11.8%, P<0.001). In multivariable meta-regression, PVI plus studies were associated with improved success (7.6% absolute improvement [95% CI, 2.6-12.5%]; P<0.01, I2=88%), specifically superior vena cava isolation (4 studies, 4 treatment arms, 1392 patients; 15.1% absolute improvement [95% CI, 2.3-27.9%]; P 0.02, I2=87%). However, residual heterogeneity was large. Conclusions Across the paroxysmal atrial fibrillation ablation literature, PVI plus ablation strategies were associated with incremental improvements in success rate. However, large residual heterogeneity complicates evidence synthesis.

Tubulin glutamylation is a post-translational modification that occurs predominantly in the ciliary axoneme and has been suggested to be important for ciliary function. However, its relationship to disorders of the primary cilium, termed ciliopathies, has not been explored. Here we mapped a new locus for Joubert syndrome (JBTS), which we have designated as JBTS15, and identified causative mutations in CEP41, which encodes a 41-kDa centrosomal protein. We show that CEP41 is localized to the basal body and primary cilia, and regulates ciliary entry of TTLL6, an evolutionarily conserved polyglutamylase enzyme. Depletion of CEP41 causes ciliopathy-related phenotypes in zebrafish and mice and results in glutamylation defects in the ciliary axoneme. Our data identify CEP41 mutations as a cause of JBTS and implicate tubulin post-translational modification in the pathogenesis of human ciliary dysfunction.