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      Nonsense mutation in CFAP43 causes normal-pressure hydrocephalus with ciliary abnormalities

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          Abstract

          Objective

          To identify genes related to normal-pressure hydrocephalus (NPH) in one Japanese family with several members with NPH.

          Methods

          We performed whole-exome sequencing (WES) on a Japanese family with multiple individuals with NPH and identified a candidate gene. Then we generated knockout mouse using CRISPR/Cas9 to confirm the effect of the candidate gene on the pathogenesis of hydrocephalus.

          Results

          In WES, we identified a loss-of-function variant in CFAP43 that segregated with the disease. CFAP43 encoding cilia- and flagella-associated protein is preferentially expressed in the testis. Recent studies have revealed that mutations in this gene cause male infertility owing to morphologic abnormalities of sperm flagella. We knocked out mouse ortholog Cfap43 using CRISPR/Cas9 technology, resulting in Cfap43-deficient mice that exhibited a hydrocephalus phenotype with morphologic abnormality of motile cilia.

          Conclusion

          Our results strongly suggest that CFAP43 is responsible for morphologic or movement abnormalities of cilia in the brain that result in NPH.

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          Most cited references9

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          Human genetic variation database, a reference database of genetic variations in the Japanese population

          Whole-genome and -exome resequencing using next-generation sequencers is a powerful approach for identifying genomic variations that are associated with diseases. However, systematic strategies for prioritizing causative variants from many candidates to explain the disease phenotype are still far from being established, because the population-specific frequency spectrum of genetic variation has not been characterized. Here, we have collected exomic genetic variation from 1208 Japanese individuals through a collaborative effort, and aggregated the data into a prevailing catalog. In total, we identified 156 622 previously unreported variants. The allele frequencies for the majority (88.8%) were lower than 0.5% in allele frequency and predicted to be functionally deleterious. In addition, we have constructed a Japanese-specific major allele reference genome by which the number of unique mapping of the short reads in our data has increased 0.045% on average. Our results illustrate the importance of constructing an ethnicity-specific reference genome for identifying rare variants. All the collected data were centralized to a newly developed database to serve as useful resources for exploring pathogenic variations. Public access to the database is available at http://www.genome.med.kyoto-u.ac.jp/SnpDB/.
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            Biallelic Mutations in CFAP43 and CFAP44 Cause Male Infertility with Multiple Morphological Abnormalities of the Sperm Flagella.

            Sperm motility is vital to human reproduction. Malformations of sperm flagella can cause male infertility. Men with multiple morphological abnormalities of the flagella (MMAF) have abnormal spermatozoa with absent, short, coiled, bent, and/or irregular-caliber flagella, which impair sperm motility. The known human MMAF-associated genes, such as DNAH1, only account for fewer than 45% of affected individuals. Pathogenic mechanisms in the genetically unexplained MMAF remain to be elucidated. Here, we conducted genetic analyses by using whole-exome sequencing and genome-wide comparative genomic hybridization microarrays in a multi-center cohort of 30 Han Chinese men affected by MMAF. Among them, 12 subjects could not be genetically explained by any known MMAF-associated genes. Intriguingly, we identified compound-heterozygous mutations in CFAP43 in three subjects and a homozygous frameshift mutation in CFAP44 in one subject. All of these recessive mutations were parentally inherited from heterozygous carriers but were absent in 984 individuals from three Han Chinese control populations. CFAP43 and CFAP44, encoding two cilia- and flagella-associated proteins (CFAPs), are specifically or preferentially expressed in the testis. Using CRISPR/Cas9 technology, we generated two knockout models each deficient in mouse ortholog Cfap43 or Cfap44. Notably, both Cfap43- and Cfap44-deficient male mice presented with MMAF phenotypes, whereas the corresponding female mice were fertile. Our experimental observations on human subjects and animal models strongly suggest that biallelic mutations in either CFAP43 or CFAP44 can cause sperm flagellar abnormalities and impair sperm motility. Further investigations on other CFAP-encoding genes in more genetically unexplained MMAF-affected individuals could uncover novel mechanisms underlying sperm flagellar formation.
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              Mutations in CFAP43 and CFAP44 cause male infertility and flagellum defects in Trypanosoma and human

              Spermatogenesis defects concern millions of men worldwide, yet the vast majority remains undiagnosed. Here we report men with primary infertility due to multiple morphological abnormalities of the sperm flagella with severe disorganization of the sperm axoneme, a microtubule-based structure highly conserved throughout evolution. Whole-exome sequencing was performed on 78 patients allowing the identification of 22 men with bi-allelic mutations in DNAH1 (n = 6), CFAP43 (n = 10), and CFAP44 (n = 6). CRISPR/Cas9 created homozygous CFAP43/44 male mice that were infertile and presented severe flagellar defects confirming the human genetic results. Immunoelectron and stimulated-emission-depletion microscopy performed on CFAP43 and CFAP44 orthologs in Trypanosoma brucei evidenced that both proteins are located between the doublet microtubules 5 and 6 and the paraflagellar rod. Overall, we demonstrate that CFAP43 and CFAP44 have a similar structure with a unique axonemal localization and are necessary to produce functional flagella in species ranging from Trypanosoma to human.
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                Author and article information

                Contributors
                Journal
                Neurology
                Neurology
                neurology
                neur
                neurology
                NEUROLOGY
                Neurology
                Lippincott Williams & Wilkins (Hagerstown, MD )
                0028-3878
                1526-632X
                14 May 2019
                14 May 2019
                : 92
                : 20
                : e2364-e2374
                Affiliations
                From the Departments of Neuropsychiatry (Y.M., N.Y., H.O.) and Otolaryngology-Head and Neck Surgery (C.S.), Unit of Translation Medicine, and Department of Human Genetics (S.Y., A.K., H.M., K.-i.Y., S.O.), Nagasaki University Graduate School of Biomedical Sciences; Department of Tumor and Diagnostic Pathology, Atomic Bomb Disease Institute (K.M., M.N.), Central Laboratory, Institute of Tropical Medicine (NEKKEN) (M.S.), and Gene Research Center, Center for Frontier Life Sciences (T.K.), Nagasaki University; Department of Infectious Diseases (T.T.) and Child and Adolescent Psychiatry Community Partnership Unit (A.I.), Nagasaki University Hospital; Department of Cell Pathology (Y.K.), Graduate School of Medical Sciences, Kumamoto University; and Department of Clinical Psychology, Faculty of Medicine (N.K.), Kagawa University, Takamatsu, Japan.
                Author notes

                Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.

                The Article Processing Charge was funded by Japan Society of Promotion of Science.

                Author information
                http://orcid.org/0000-0001-5050-2509
                Article
                NEUROLOGY2018945816
                10.1212/WNL.0000000000007505
                6598815
                31004071
                b8092257-a50e-4d24-a6c9-b89917c566bf
                Copyright © 2019 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.

                This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND), which permits downloading and sharing the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

                History
                : 17 October 2018
                : 22 January 2019
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