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Nephroplex: a kidney-focused NGS panel highlights the challenges of PKD1 sequencing and identifies a founder BBS4 mutation. J Nephrol 2021; 34:1855-1874. [PMID: 33964006 PMCID: PMC8610957 DOI: 10.1007/s40620-021-01048-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 04/04/2021] [Indexed: 12/02/2022]
Abstract
Background Genetic testing of patients with inherited kidney diseases has emerged as a tool of clinical utility by improving the patients’ diagnosis, prognosis, surveillance and therapy. Methods The present study applied a Next Generation Sequencing (NGS)-based panel, named NephroPlex, testing 115 genes causing renal diseases, to 119 individuals, including 107 probands and 12 relatives. Thirty-five (poly)cystic and 72 non (poly)cystic individuals were enrolled. The latter subgroup of patients included Bardet-Biedl syndrome (BBS) patients, as major components. Results Disease-causing mutations were identified in 51.5 and 40% of polycystic and non-polycystic individuals, respectively. Autosomal dominant polycystic kidney disease (ADPKD) patients with truncating PKD1 variants showed a trend towards a greater slope of the age-estimated glomerular filtration rate (eGFR) regression line than patients with (i) missense variants, (ii) any PKD2 mutations and (iii) no detected mutations, according to previous findings. The analysis of BBS individuals showed a similar frequency of BBS4,9,10 and 12 mutations. Of note, all BBS4-mutated patients harbored the novel c.332+1G>GTT variant, which was absent in public databases, however, in our internal database, an additional heterozygote carrier was found. All BBS4-mutated individuals originated from the same geographical area encompassing the coastal provinces of Naples. Discussion In conclusion, these findings indicate the potential for a genetic panel to provide useful information at both clinical and epidemiological levels. Graphic abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1007/s40620-021-01048-4.
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Horinouchi T, Yamamura T, Minamikawa S, Nagano C, Sakakibara N, Nakanishi K, Shima Y, Morisada N, Ishiko S, Aoto Y, Nagase H, Takeda H, Rossanti R, Ishimori S, Kaito H, Matsuo M, Iijima K, Nozu K. Pathogenic evaluation of synonymous COL4A5 variants in X-linked Alport syndrome using a minigene assay. Mol Genet Genomic Med 2020; 8:e1342. [PMID: 32543079 PMCID: PMC7434753 DOI: 10.1002/mgg3.1342] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 05/13/2020] [Accepted: 05/19/2020] [Indexed: 12/20/2022] Open
Abstract
Background X‐linked Alport syndrome (XLAS) is a progressive, hereditary glomerular nephritis of variable severity caused by pathogenic COL4A5 variants. Currently, genetic testing is widely used for diagnosing XLAS; however, determining the pathogenicity of variants detected by such analyses can be difficult. Intronic variants or synonymous variants may cause inherited diseases by inducing aberrant splicing. Transcript analysis is necessary to confirm the pathogenicity of such variants, but it is sometimes difficult to extract mRNA directly from patient specimens. Methods In this study, we conducted in vitro splicing analysis using a hybrid minigene assay and specimens from three XLAS patients with synonymous variants causing aberrant splicing, including previously reported pathogenic mutations in the same codon. The variants were c.876 A>T (p.Gly292=), c.2358 A>G (p.Pro786=), and c.3906 A>G (p.Gln1302=). Results The results from our hybrid minigene assay were sufficient to predict splicing abnormalities; c.876 A>T cause 17‐bp del and 35‐bp del, c.2358 A>G cause exon 29 skipping, c.3906 A>G cause exon 42 skipping, which are very likely to cause pathogenicity. Further, patients carrying c.2358 A>G exhibited a mild phenotype that may have been associated with the presence of both normal and abnormally spliced transcripts. Conclusion The minigene system was shown to be a sensitive assay and a useful tool for investigating the pathogenicity of synonymous variants.
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Affiliation(s)
- Tomoko Horinouchi
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Tomohiko Yamamura
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Shogo Minamikawa
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - China Nagano
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Nana Sakakibara
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Koichi Nakanishi
- Department of Child Health and Welfare (Pediatrics), Graduate School of Medicine, University of the Ryukyus, Nishihara, Japan
| | - Yuko Shima
- Department of Pediatrics, Wakayama Medical University, Wakayama, Japan
| | - Naoya Morisada
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Shinya Ishiko
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yuya Aoto
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroaki Nagase
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroki Takeda
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Rini Rossanti
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Shingo Ishimori
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroshi Kaito
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Masafumi Matsuo
- Department of Physical Therapy, Faculty of Rehabilitation, Kobe Gakuin University, Kobe, Japan
| | - Kazumoto Iijima
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Kandai Nozu
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
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Monogenic causes of chronic kidney disease in adults. Kidney Int 2019; 95:914-928. [PMID: 30773290 DOI: 10.1016/j.kint.2018.10.031] [Citation(s) in RCA: 148] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 10/10/2018] [Accepted: 10/19/2018] [Indexed: 12/18/2022]
Abstract
Approximately 500 monogenic causes of chronic kidney disease (CKD) have been identified, mainly in pediatric populations. The frequency of monogenic causes among adults with CKD has been less extensively studied. To determine the likelihood of detecting monogenic causes of CKD in adults presenting to nephrology services in Ireland, we conducted whole exome sequencing (WES) in a multi-centre cohort of 114 families including 138 affected individuals with CKD. Affected adults were recruited from 78 families with a positive family history, 16 families with extra-renal features, and 20 families with neither a family history nor extra-renal features. We detected a pathogenic mutation in a known CKD gene in 42 of 114 families (37%). A monogenic cause was identified in 36% of affected families with a positive family history of CKD, 69% of those with extra-renal features, and only 15% of those without a family history or extra-renal features. There was no difference in the rate of genetic diagnosis in individuals with childhood versus adult onset CKD. Among the 42 families in whom a monogenic cause was identified, WES confirmed the clinical diagnosis in 17 (40%), corrected the clinical diagnosis in 9 (22%), and established a diagnosis for the first time in 16 families referred with CKD of unknown etiology (38%). In this multi-centre study of adults with CKD, a molecular genetic diagnosis was established in over one-third of families. In the evolving era of precision medicine, WES may be an important tool to identify the cause of CKD in adults.
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Savige J, Storey H, Il Cheong H, Gyung Kang H, Park E, Hilbert P, Persikov A, Torres-Fernandez C, Ars E, Torra R, Hertz JM, Thomassen M, Shagam L, Wang D, Wang Y, Flinter F, Nagel M. X-Linked and Autosomal Recessive Alport Syndrome: Pathogenic Variant Features and Further Genotype-Phenotype Correlations. PLoS One 2016; 11:e0161802. [PMID: 27627812 PMCID: PMC5023110 DOI: 10.1371/journal.pone.0161802] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 08/14/2016] [Indexed: 01/15/2023] Open
Abstract
Alport syndrome results from mutations in the COL4A5 (X-linked) or COL4A3/COL4A4 (recessive) genes. This study examined 754 previously- unpublished variants in these genes from individuals referred for genetic testing in 12 accredited diagnostic laboratories worldwide, in addition to all published COL4A5, COL4A3 and COL4A4 variants in the LOVD databases. It also determined genotype-phenotype correlations for variants where clinical data were available. Individuals were referred for genetic testing where Alport syndrome was suspected clinically or on biopsy (renal failure, hearing loss, retinopathy, lamellated glomerular basement membrane), variant pathogenicity was assessed using currently-accepted criteria, and variants were examined for gene location, and age at renal failure onset. Results were compared using Fisher’s exact test (DNA Stata). Altogether 754 new DNA variants were identified, an increase of 25%, predominantly in people of European background. Of the 1168 COL4A5 variants, 504 (43%) were missense mutations, 273 (23%) splicing variants, 73 (6%) nonsense mutations, 169 (14%) short deletions and 76 (7%) complex or large deletions. Only 135 of the 432 Gly residues in the collagenous sequence were substituted (31%), which means that fewer than 10% of all possible variants have been identified. Both missense and nonsense mutations in COL4A5 were not randomly distributed but more common at the 70 CpG sequences (p<10−41 and p<0.001 respectively). Gly>Ala substitutions were underrepresented in all three genes (p< 0.0001) probably because of an association with a milder phenotype. The average age at end-stage renal failure was the same for all mutations in COL4A5 (24.4 ±7.8 years), COL4A3 (23.3 ± 9.3) and COL4A4 (25.4 ± 10.3) (COL4A5 and COL4A3, p = 0.45; COL4A5 and COL4A4, p = 0.55; COL4A3 and COL4A4, p = 0.41). For COL4A5, renal failure occurred sooner with non-missense than missense variants (p<0.01). For the COL4A3 and COL4A4 genes, age at renal failure occurred sooner with two non-missense variants (p = 0.08, and p = 0.01 respectively). Thus DNA variant characteristics that predict age at renal failure appeared to be the same for all three Alport genes. Founder mutations (with the pathogenic variant in at least 5 apparently- unrelated individuals) were not necessarily associated with a milder phenotype. This study illustrates the benefits when routine diagnostic laboratories share and analyse their data.
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Affiliation(s)
- Judith Savige
- The University of Melbourne, Melbourne Health and Northern Health, Melbourne, Australia
- * E-mail:
| | - Helen Storey
- Molecular Genetics Laboratory, Guy’s and St Thomas’ Hospital, London, United Kingdom
| | - Hae Il Cheong
- Research Coordination Center for Rare Diseases, Seoul National University Hospital, Seoul, Korea
| | - Hee Gyung Kang
- Research Coordination Center for Rare Diseases, Seoul National University Hospital, Seoul, Korea
| | - Eujin Park
- Research Coordination Center for Rare Diseases, Seoul National University Hospital, Seoul, Korea
| | - Pascale Hilbert
- Institut de Pathologie et Genetique, Department of Molecular Biology, Gosselles, Belgium
| | - Anton Persikov
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | | | - Elisabet Ars
- Molecular Biology Laboratory and Department of Nephrology, REDINREN, Fundacio Puigvert, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Roser Torra
- Molecular Biology Laboratory and Department of Nephrology, REDINREN, Fundacio Puigvert, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Jens Michael Hertz
- Department of Clinical Genetics, Odense University Hospital, Odense, Denmark
| | - Mads Thomassen
- Department of Clinical Genetics, Odense University Hospital, Odense, Denmark
| | - Lev Shagam
- Institute of Pediatrics, Pirogov Russian Medical University, Moscow, Russia
| | - Dongmao Wang
- The University of Melbourne, Melbourne Health and Northern Health, Melbourne, Australia
| | - Yanyan Wang
- The University of Melbourne, Melbourne Health and Northern Health, Melbourne, Australia
| | - Frances Flinter
- Department of Genetics, Guy’s and St Thomas’ Hospital, London, United Kingdom
| | - Mato Nagel
- Centre for Nephrology and Metabolic Medicine, Weisswasser D-02943, Germany
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Weber S, Strasser K, Rath S, Kittke A, Beicht S, Alberer M, Lange-Sperandio B, Hoyer PF, Benz MR, Ponsel S, Weber LT, Klein HG, Hoefele J. Identification of 47 novel mutations in patients with Alport syndrome and thin basement membrane nephropathy. Pediatr Nephrol 2016; 31:941-55. [PMID: 26809805 DOI: 10.1007/s00467-015-3302-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 12/08/2015] [Accepted: 12/10/2015] [Indexed: 01/26/2023]
Abstract
BACKGROUND Alport syndrome (ATS) is a progressive hereditary nephropathy characterized by hematuria and proteinuria. It can be associated with extrarenal manifestations. In contrast, thin basement membrane nephropathy (TBMN) is characterized by microscopic hematuria, is largely asymptomatic, and is rarely associated with proteinuria and end-stage renal disease. Mutations have been identified in the COL4A5 gene in ATS and in the COL4A3 and COL4A4 genes in ATS and TBMN. To date, more than 1000 different mutations in COL4A5, COL4A3, and COL4A4 are known. METHODS In this study mutational analysis by exon sequencing and multiplex ligation-dependent probe amplification was performed in a large European cohort of families with ATS and TBMN. RESULTS Molecular diagnostic testing of 216 individuals led to the detection of 47 novel mutations, thereby expanding the spectrum of known mutations causing ATS and TBMN by up to 10 and 6%, respectively, depending on the database. Remarkably, a high number of ATS patients with only single mutations in COL4A3 and COL4A4 were identified. Additionally, three ATS patients presented with synonymous sequence variants that possible affect correct mRNA splicing, as suggested by in silico analysis. CONCLUSIONS The results of this study clearly broaden the genotypic spectrum of known mutations for ATS and TBMN, which will in turn now facilitate future studies into genotype-phenotype correlations. Further studies should also examine the significance of single heterozygous mutations in COL4A3 and COL4A4 and of synonymous sequence variants associated with ATS.
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Affiliation(s)
- Stefanie Weber
- Pediatric Nephrology, Pediatrics II, University of Duisburg-Essen, Essen, Germany
| | - Katja Strasser
- Pediatric Nephrology, Pediatrics II, University of Duisburg-Essen, Essen, Germany
| | - Sabine Rath
- Center for Human Genetics and Laboratory Diagnostics Dr. Klein, Dr. Rost and Colleagues, Martinsried, Germany
| | - Achim Kittke
- Center for Human Genetics and Laboratory Diagnostics Dr. Klein, Dr. Rost and Colleagues, Martinsried, Germany
| | - Sonja Beicht
- Center for Human Genetics and Laboratory Diagnostics Dr. Klein, Dr. Rost and Colleagues, Martinsried, Germany
| | - Martin Alberer
- Department of Infectious Diseases and Tropical Medicine, Ludwig-Maximilians University, Munich, Germany
| | - Bärbel Lange-Sperandio
- Pediatric Nephrology, University Children's Hospital, Ludwig-Maximilians University, Munich, Germany
| | - Peter F Hoyer
- Pediatric Nephrology, Pediatrics II, University of Duisburg-Essen, Essen, Germany
| | - Marcus R Benz
- Pediatric Nephrology, University Children's Hospital, Cologne, Germany
| | - Sabine Ponsel
- Pediatric Nephrology, University Children's Hospital, Ludwig-Maximilians University, Munich, Germany
| | - Lutz T Weber
- Pediatric Nephrology, University Children's Hospital, Cologne, Germany
| | - Hanns-Georg Klein
- Center for Human Genetics and Laboratory Diagnostics Dr. Klein, Dr. Rost and Colleagues, Martinsried, Germany
| | - Julia Hoefele
- Center for Human Genetics and Laboratory Diagnostics Dr. Klein, Dr. Rost and Colleagues, Martinsried, Germany. .,Institute of Human Genetics, Technische Universität München, Munich, Germany.
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Abe Y, Iyoda M, Nozu K, Hibino S, Hihara K, Yamaguchi Y, Yamamura T, Minamikawa S, Iijima K, Shibata T, Itabashi K. A Novel Mutation in a Japanese Family with X-linked Alport Syndrome. Intern Med 2016; 55:2843-2847. [PMID: 27725546 PMCID: PMC5088547 DOI: 10.2169/internalmedicine.55.6873] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We herein report a novel mutation in a Japanese family with an X-linked Alport syndrome (AS) mutation in COL4A5. Patient 1 was a 2-year-old Japanese girl. She and her mother (patient 2) had a history of proteinuria and hematuria without renal dysfunction, deafness, or ocular abnormalities. Pathological findings were consistent with AS, and a genetic analysis revealed that both patients had a heterozygous mutation (c.2767G>C) in exon 32. In summary, the identification of mutations and characteristic pathological findings was useful in making a diagnosis of AS. For a close long-term follow-up, the early detection and treatment of women with X-linked AS are important.
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Affiliation(s)
- Yoshifusa Abe
- Department of Pediatrics, Showa University School of Medicine, Japan
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Nozu K, Vorechovsky I, Kaito H, Fu XJ, Nakanishi K, Hashimura Y, Hashimoto F, Kamei K, Ito S, Kaku Y, Imasawa T, Ushijima K, Shimizu J, Makita Y, Konomoto T, Yoshikawa N, Iijima K. X-linked Alport syndrome caused by splicing mutations in COL4A5. Clin J Am Soc Nephrol 2014; 9:1958-64. [PMID: 25183659 DOI: 10.2215/cjn.04140414] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVES X-linked Alport syndrome is caused by mutations in the COL4A5 gene. Although many COL4A5 mutations have been detected, the mutation detection rate has been unsatisfactory. Some men with X-linked Alport syndrome show a relatively mild phenotype, but molecular basis investigations have rarely been conducted to clarify the underlying mechanism. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS In total, 152 patients with X-linked Alport syndrome who were suspected of having Alport syndrome through clinical and pathologic investigations and referred to the hospital for mutational analysis between January of 2006 and January of 2013 were genetically diagnosed. Among those patients, 22 patients had suspected splice site mutations. Transcripts are routinely examined when suspected splice site mutations for abnormal transcripts are detected; 11 of them showed expected exon skipping, but others showed aberrant splicing patterns. The mutation detection strategy had two steps: (1) genomic DNA analysis using PCR and direct sequencing and (2) mRNA analysis using RT-PCR to detect RNA processing abnormalities. RESULTS Six splicing consensus site mutations resulting in aberrant splicing patterns, one exonic mutation leading to exon skipping, and four deep intronic mutations producing cryptic splice site activation were identified. Interestingly, one case produced a cryptic splice site with a single nucleotide substitution in the deep intron that led to intronic exonization containing a stop codon; however, the patient showed a clearly milder phenotype for X-linked Alport syndrome in men with a truncating mutation. mRNA extracted from the kidney showed both normal and abnormal transcripts, with the normal transcript resulting in the milder phenotype. This novel mechanism leads to mild clinical characteristics. CONCLUSIONS This report highlights the importance of analyzing transcripts to enhance the mutation detection rate and provides insight into genotype-phenotype correlations. This approach can clarify the cause of atypically mild phenotypes in X-linked Alport syndrome.
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Affiliation(s)
- Kandai Nozu
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan;
| | - Igor Vorechovsky
- Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Hiroshi Kaito
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Xue Jun Fu
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Koichi Nakanishi
- Department of Pediatrics, Wakayama Medical University, Wakayama, Japan
| | - Yuya Hashimura
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Fusako Hashimoto
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Koichi Kamei
- Division of Nephrology and Rheumatology, National Center for Child Health and Development, Tokyo, Japan
| | - Shuichi Ito
- Division of Nephrology and Rheumatology, National Center for Child Health and Development, Tokyo, Japan
| | - Yoshitsugu Kaku
- Department of Nephrology, Fukuoka Children's Hospital, Fukuoka, Japan
| | - Toshiyuki Imasawa
- Kidney Center, National Hospital Organization Chiba-East Hospital, Chiba, Japan
| | - Katsumi Ushijima
- Department of Pediatrics, Yokkaichi Municipal Hospital, Mie, Japan
| | - Junya Shimizu
- Department of Pediatrics, National Hospital Organization Okayama Medical Center, Okayama, Japan
| | - Yoshio Makita
- Education Center, Asahikawa Medical University, Hokkaido, Japan; and
| | - Takao Konomoto
- Department of Pediatrics, Faculty of Medicine, University of Miyazaki, Miyazaki, Japan
| | | | - Kazumoto Iijima
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
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Deltas C, Pierides A, Voskarides K. Molecular genetics of familial hematuric diseases. Nephrol Dial Transplant 2013; 28:2946-60. [PMID: 24046192 DOI: 10.1093/ndt/gft253] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The familial hematuric diseases are a genetically heterogeneous group of monogenic conditions, caused by mutations in one of several genes. The major genes involved are the following: (i) the collagen IV genes COL4A3/A4/A5 that are expressed in the glomerular basement membranes (GBM) and are responsible for the most frequent forms of microscopic hematuria, namely Alport syndrome (X-linked or autosomal recessive) and thin basement membrane nephropathy (TBMN). (ii) The FN1 gene, expressed in the glomerulus and responsible for a rare form of glomerulopathy with fibronectin deposits (GFND). (iii) CFHR5 gene, a recently recognized regulator of the complement alternative pathway and mutated in a recently revisited form of inherited C3 glomerulonephritis (C3GN), characterized by isolated C3 deposits in the absence of immune complexes. A hallmark feature of all conditions is the age-dependent penetrance and a broad phenotypic heterogeneity in the sense that subsets of patients progress to added proteinuria or proteinuria and chronic renal failure that may or may not lead to end-stage kidney disease (ESKD) anywhere between the second and seventh decade of life. In addition to other excellent laboratory tools that assist the clinician in reaching the correct diagnosis, the molecular analysis emerges as the gold standard in establishing the diagnosis in many cases of doubt due to equivocal findings that complicate the differential diagnosis. Recent work led to the description of candidate genetic modifiers which confer a variable risk for progressing to chronic renal failure when co-inherited on the background of a primary glomerulopathy. Finally, more families are still waiting to be studied and more genes to be mapped and cloned that are responsible for other forms of heritable hematuric diseases. The study of such genes and their protein products will likely shed more light on the structure and function of the glomerular filtration barrier and other important glomerular components.
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Affiliation(s)
- Constantinos Deltas
- Molecular Medicine Research Center and Laboratory of Molecular and Medical Genetics, Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus
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How benign is hematuria? Using genetics to predict prognosis. Pediatr Nephrol 2013; 28:1183-93. [PMID: 23325022 DOI: 10.1007/s00467-012-2399-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 12/17/2012] [Accepted: 12/18/2012] [Indexed: 01/22/2023]
Abstract
Hematuria is a common presenting feature of glomerular disease and is sometimes associated with kidney failure later in life. Where isolated microscopic hematuria occurs in children and young adults, an underlying monogenic disorder, such as Alport syndrome or thin basement membrane nephropathy, is frequently responsible. In this review, these and other diseases, which often present with isolated microscopic hematuria, including hereditary angiopathy, nephropathy, aneurysms, and muscle cramps (HANAC) syndrome, IgA nephropathy, and CFHR5 nephropathy, are discussed together with the associated molecular pathology, clinical features, and prognosis. Genetic testing for these conditions used in clinical practice can provide important diagnostic and prognostic information that is relevant to the patient and their family, particularly when kidney transplantation is considered.
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Antón-Martín P, Aparicio López C, Ramiro-León S, Santillán Garzón S, Santos-Simarro F, Gil-Fournier B. Alport Syndrome: De Novo Mutation in the COL4A5 Gene Converting Glycine 1205 to Valine. CLINICAL MEDICINE INSIGHTS-PEDIATRICS 2012; 6:41-9. [PMID: 23641165 PMCID: PMC3620815 DOI: 10.2147/cbf.s23366] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND Alport syndrome is a primary basement membrane disorder arising from mutations in genes encoding the type IV collagen protein family. It is a genetically heterogeneous disease with different mutations and forms of inheritance that presents with renal affection, hearing loss and eye defects. Several new mutations related to X-linked forms have been previously determined. METHODS We report the case of a 12 years old male and his family diagnosed with Alport syndrome after genetic analysis was performed. RESULT A new mutation determining a nucleotide change c.3614G > T (p.Gly1205Val) in hemizygosis in the COL4A5 gene was found. This molecular defect has not been previously described. CONCLUSION Molecular biology has helped us to comprehend the mechanisms of pathophysiology in Alport syndrome. Genetic analysis provides the only conclusive diagnosis of the disorder at the moment. Our contribution with a new mutation further supports the need of more sophisticated molecular methods to increase the mutation detection rates with lower costs and less time.
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Affiliation(s)
- Pilar Antón-Martín
- Department of Pediatrics, Division of Nephrology, Hospital Universitario de Getafe, Madrid, Spain
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11
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The role of molecular genetics in diagnosing familial hematuria(s). Pediatr Nephrol 2012; 27:1221-31. [PMID: 21688191 PMCID: PMC3382641 DOI: 10.1007/s00467-011-1935-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 05/24/2011] [Accepted: 05/25/2011] [Indexed: 01/18/2023]
Abstract
Familial microscopic hematuria (MH) of glomerular origin represents a heterogeneous group of monogenic conditions involving several genes, some of which remain unknown. Recent advances have increased our understanding and our ability to use molecular genetics for diagnosing such patients, enabling us to study their clinical characteristics over time. Three collagen IV genes, COL4A3, COL4A4, and COL4A5 explain the autosomal and X-linked forms of Alport syndrome (AS), and a subset of thin basement membrane nephropathy (TBMN). A number of X-linked AS patients follow a milder course reminiscent of that of patients with heterozygous COL4A3/COL4A4 mutations and TBMN, while at the same time a significant subset of patients with TBMN and familial MH progress to chronic kidney disease (CKD) or end-stage kidney disease (ESKD). A mutation in CFHR5, a member of the complement factor H family of genes that regulate complement activation, was recently shown to cause isolated C3 glomerulopathy, presenting with MH in childhood and demonstrating a significant risk for CKD/ESKD after 40 years old. Through these results molecular genetics emerges as a powerful tool for a definite diagnosis when all the above conditions enter the differential diagnosis, while in many at-risk related family members, a molecular diagnosis may obviate the need for another renal biopsy.
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12
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Antón-Martín P, López CA, Ramiro-León S, Garzón SS, Santos-Simarro F, Gil-Fournier B. Alport Syndrome: De Novo Mutation in the COL4A5 Gene Converting Glycine 1205 to Valine. CLINICAL MEDICINE. PEDIATRICS 2012. [DOI: 10.4137/cmped.s7509] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BackgroundAlport syndrome is a primary basement membrane disorder arising from mutations in genes encoding the type IV collagen protein family. It is a genetically heterogeneous disease with different mutations and forms of inheritance that presents with renal affection, hearing loss and eye defects. Several new mutations related to X-linked forms have been previously determined.MethodsWe report the case of a 12 years old male and his family diagnosed with Alport syndrome after genetic analysis was performed.ResultAnew mutation determining a nucleotide change C.3614G > T (p. Gly1205Val) in hemizygosis in the COL4A5 gene was found. This molecular defect has not been previously described.ConclusionMolecular biology has helped us to comprehend the mechanisms of pathophysiology in Alport syndrome. Genetic analysis provides the only conclusive diagnosis of the disorder at the moment. Our contribution with a new mutation further supports the need of more sophisticated molecular methods to increase the mutation detection rates with lower costs and less time.
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Affiliation(s)
- Pilar Antón-Martín
- Department of Pediatrics, Division of Nephrology, Hospital Universitario de Getafe, Madrid, Spain
| | - Cristina Aparicio López
- Department of Pediatrics, Division of Nephrology, Hospital Universitario de Getafe, Madrid, Spain
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Artuso R, Fallerini C, Dosa L, Scionti F, Clementi M, Garosi G, Massella L, Epistolato MC, Mancini R, Mari F, Longo I, Ariani F, Renieri A, Bruttini M. Advances in Alport syndrome diagnosis using next-generation sequencing. Eur J Hum Genet 2011; 20:50-7. [PMID: 21897443 DOI: 10.1038/ejhg.2011.164] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Alport syndrome (ATS) is a hereditary nephropathy often associated with sensorineural hypoacusis and ocular abnormalities. Mutations in the COL4A5 gene cause X-linked ATS. Mutations in COL4A4 and COL4A3 genes have been reported in both autosomal recessive and autosomal dominant ATS. The conventional mutation screening, performed by DHPLC and/or Sanger sequencing, is time-consuming and has relatively high costs because of the absence of hot spots and to the high number of exons per gene: 51 (COL4A5), 48 (COL4A4) and 52 (COL4A3). Several months are usually necessary to complete the diagnosis, especially in cases with less informative pedigrees. To overcome these limitations, we designed a next-generation sequencing (NGS) protocol enabling simultaneous detection of all possible variants in the three genes. We used a method coupling selective amplification to the 454 Roche DNA sequencing platform (Genome Sequencer junior). The application of this technology allowed us to identify the second mutation in two ATS patients (p.Ser1147Phe in COL4A3 and p.Arg1682Trp in COL4A4) and to reconsider the diagnosis of ATS in a third patient. This study, therefore, illustrates the successful application of NGS to mutation screening of Mendelian disorders with locus heterogeneity.
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Affiliation(s)
- Rosangela Artuso
- Medical Genetics Section, Biotechnology Department, University of Siena, Siena, Italy
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Zhang H, Ding J, Wang F, Zhao D. Mutation detection of COL4An gene based on mRNA of peripheral blood lymphocytes and prenatal diagnosis of Alport syndrome in China. Nephrology (Carlton) 2011; 16:377-80. [PMID: 21143337 DOI: 10.1111/j.1440-1797.2010.01438.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM Alport syndrome (AS) is a progressive renal disease characterized by haematuria and progressive renal failure. An accurate genetic diagnosis of AS is very important for genetic counselling and even prenatal diagnosis. METHODS We detected mutation of COL4An by amplifying the entire coding sequence mRNA of peripheral blood lymphocytes using polymerase chain reaction (PCR) in five Chinese AS families who asked for genetic counselling and prenatal diagnosis, then performed prenatal genetic diagnosis for four families. Mutation analysis of the foetus was made using DNA extracted from amniocytes. Foetus sex was determined by PCR amplification of SRY as well as karyotype analysis. Maternal cell contamination was excluded by linkage analysis. RESULTS Four different COL4A5 gene variants and two COL4A3 gene variants were detected in the five families. Because there was a de novo mutation in family 2, prenatal diagnosis was performed for the other four families. Results showed a normal male foetus for family 1 and family 4, respectively. Results showed an affected male foetus for families 3 and 5, and the pregnancies were terminated. CONCLUSION An easier, faster and efficacious method for COL4An gene mutation screening based on mRNA analysis from peripheral blood lymphocytes was established. Prenatal genetic diagnosis was performed in four AS families in China.
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Affiliation(s)
- Hongwen Zhang
- Department of Paediatrics, Peking University First Hospital, Beijing, China
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15
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Labelle-Dumais C, Dilworth DJ, Harrington EP, de Leau M, Lyons D, Kabaeva Z, Manzini MC, Dobyns WB, Walsh CA, Michele DE, Gould DB. COL4A1 mutations cause ocular dysgenesis, neuronal localization defects, and myopathy in mice and Walker-Warburg syndrome in humans. PLoS Genet 2011; 7:e1002062. [PMID: 21625620 PMCID: PMC3098190 DOI: 10.1371/journal.pgen.1002062] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 03/18/2011] [Indexed: 01/10/2023] Open
Abstract
Muscle-eye-brain disease (MEB) and Walker Warburg Syndrome (WWS) belong to a spectrum of autosomal recessive diseases characterized by ocular dysgenesis, neuronal migration defects, and congenital muscular dystrophy. Until now, the pathophysiology of MEB/WWS has been attributed to alteration in dystroglycan post-translational modification. Here, we provide evidence that mutations in a gene coding for a major basement membrane protein, collagen IV alpha 1 (COL4A1), are a novel cause of MEB/WWS. Using a combination of histological, molecular, and biochemical approaches, we show that heterozygous Col4a1 mutant mice have ocular dysgenesis, neuronal localization defects, and myopathy characteristic of MEB/WWS. Importantly, we identified putative heterozygous mutations in COL4A1 in two MEB/WWS patients. Both mutations occur within conserved amino acids of the triple-helix-forming domain of the protein, and at least one mutation interferes with secretion of the mutant proteins, resulting instead in intracellular accumulation. Expression and posttranslational modification of dystroglycan is unaltered in Col4a1 mutant mice indicating that COL4A1 mutations represent a distinct pathogenic mechanism underlying MEB/WWS. These findings implicate a novel gene and a novel mechanism in the etiology of MEB/WWS and expand the clinical spectrum of COL4A1-associated disorders. Muscle-eye-brain disease (MEB) and Walker-Warburg Syndrome (WWS) are devastating childhood diseases that belong to a subgroup of congenital muscular dystrophies (CMDs) characterized by ocular dysgenesis, neuronal migration defects, and congenital myopathy. Genetic studies have revealed a number of genes involved in the etiology of CMDs, and subsequent studies show that alterations in dystroglycan glycosylation underlie MEB/WWS. However, over half of MEB/WWS patients do not have mutations in known genes encoding glycosyltransferases, suggesting that other genes are involved. Here, we describe a novel and genetically complex mouse model for MEB/WWS and identify putative heterozygous mutations in COL4A1 in two MEB/WWS patients. We identify a novel gene implicated in the etiology of MEB/WWS, provide evidence of mechanistic heterogeneity for this subgroup of congenital muscular dystrophies, and develop an assay to test the functional significance of putative COL4A1 mutations. Our findings represent the first evidence for a dominant mutation leading to MEB/WWS–like diseases and expand the spectrum of clinical disorders resulting from Col4a1/COL4A1 mutations.
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Affiliation(s)
- Cassandre Labelle-Dumais
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - David J. Dilworth
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - Emily P. Harrington
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - Michelle de Leau
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - David Lyons
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - Zhyldyz Kabaeva
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - M. Chiara Manzini
- Division of Genetics and The Manton Center for Orphan Disease Research, Children's Hospital Boston, Howard Hughes Medical Institute, and Harvard Medical School, Boston, Massachusetts, United States of America
| | - William B. Dobyns
- Departments of Human Genetics, Neurology, and Pediatrics, University of Chicago, Chicago, Illinois, United States of America
| | - Christopher A. Walsh
- Division of Genetics and The Manton Center for Orphan Disease Research, Children's Hospital Boston, Howard Hughes Medical Institute, and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Daniel E. Michele
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Douglas B. Gould
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
- * E-mail:
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Ma J, Pan X, Wang Z, Wang Y, Feng X, Ren H, Zhang W, Chen X, Wang W, Chen N. Twenty-one novel mutations identified in the COL4A5 gene in Chinese patients with X-linked Alport's syndrome confirmed by skin biopsy. Nephrol Dial Transplant 2011; 26:4003-10. [PMID: 21505094 DOI: 10.1093/ndt/gfr184] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The clinical and pathological features of Alport syndrome are characterized by abnormalities in the basement membrane collagen network which are composed of the α3, α4 and α5 chains of type IV collagen and usually associated with hearing loss and ocular lesions. The predominant form (85% of AS) is inherited as X-linked mode (XLAS) caused by mutations encoding the α5 chain of type IV collagen gene, COL4A5. Different mutations in the COL4A5 gene have been reported widely, but only a few mutations were identified in Chinese patients. METHODS We studied 71 Chinese patients from 35 unrelated families with XLAS confirmed by skin biopsy. Genomic DNA was extracted from peripheral blood of all patients. All 51 exons of the COL4A5 gene were screened by direct sequencing for the probands. RESULTS A total of twenty-five identified gene mutations were considered to be pathogenic, including 1 nonsense, 1 splice-site, 1 complex rearrangement, 5 small deletions, 2 small insertions and 15 missense mutations. Twenty-one mutations have not been reported previously. CONCLUSIONS We have identified 25 pathogenic mutations in 35 Chinese families with XLAS. Skin biopsy is effective for the diagnosis of XLAS.
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Affiliation(s)
- Jun Ma
- Department of Nephrology, Shanghai Jiaotong University School of Medicine, Shanghai, China
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17
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Demosthenous P, Voskarides K, Stylianou K, Hadjigavriel M, Arsali M, Patsias C, Georgaki E, Zirogiannis P, Stavrou C, Daphnis E, Pierides A, Deltas C. X-linked Alport syndrome in Hellenic families: phenotypic heterogeneity and mutations near interruptions of the collagen domain in COL4A5. Clin Genet 2011; 81:240-8. [PMID: 21332469 DOI: 10.1111/j.1399-0004.2011.01647.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The X-linked Alport syndrome (ATS) is caused by mutations in COL4A5 and exhibits a widely variable expression. Usually ATS is heralded with continuous microhematuria which rapidly progresses to proteinuria, hypertension and chronic or end-stage renal disease (ESRD) by adolescence, frequently accompanied by sensorineural deafness and ocular complications. Milder forms of ATS also exist. We studied 42 patients (19M, 23F) of nine Hellenic families suspected clinically of X-linked ATS who presented with marked phenotypic heterogeneity. We identified mutations in COL4A5 in six families. Two males with nonsense mutation E228X reached ESRD by ages 14 and 18. Frameshift mutation 2946delT followed the same course with early onset renal involvement and deafness. However, two males with the milder missense mutation G624D, reached ESRD after 39 years and one patient showed thin basement membrane nephropathy (TBMN). Another 5/8 affected males with missense mutation P628L also developed ESRD between 30 and 57 years, while three exhibit only mild chronic renal failure (CRF). The data support previous findings that certain mutations are associated with milder phenotypes and confirm that mutation G624D may be expressed as TBMN with familial hematuria. Similar conclusions apply for missense mutation P628L. Interestingly, mutations G624D and P628L are near the 12th natural interruption of COL4A5 triple helical domain, which may explain the milder phenotype.
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Affiliation(s)
- P Demosthenous
- Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus
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Bekheirnia MR, Reed B, Gregory MC, McFann K, Shamshirsaz AA, Masoumi A, Schrier RW. Genotype-phenotype correlation in X-linked Alport syndrome. J Am Soc Nephrol 2010; 21:876-83. [PMID: 20378821 DOI: 10.1681/asn.2009070784] [Citation(s) in RCA: 176] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Mutations in the COL4A5 gene cause X-linked Alport syndrome (XLAS). Understanding the correlation between clinical manifestations and the underlying mutations adds prognostic value to genetic testing, which is increasingly available. Our aim was to determine the association between genotype and phenotype in 681 affected male participants with XLAS from 175 US families. Hearing loss and ocular changes were present in 67 and 30% of participants, respectively. Average age of participants at onset of ESRD was 37 years for those with missense mutations, 28 years for those with splice-site mutations, and 25 years for those with truncating mutations (P < 0.0001). We demonstrated a strong relationship between mutation position and age at onset of ESRD, with younger age at onset of ESRD associated with mutations at the 5' end of the gene (hazard ratio 0.766 [95% confidence interval 0.694 to 0.846] per 1000 bp toward the 3' end; P < 0.0001). Affected participants with splice mutations or truncating mutations each had two-fold greater odds of developing eye problems than those with missense mutations; development of hearing impairment showed a similar trend. Hearing loss and ocular changes associated with mutations located closer to the 5; end of the gene. These strong genotype-phenotype correlations could potentially help in the evaluation and counseling of US families with XLAS.
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Affiliation(s)
- Mir Reza Bekheirnia
- Department of Medicine, University of Colorado Denver, Aurora, Colorado 80045, USA
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19
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Kaneko K, Tanaka S, Hasui M, Nozu K, Krol RP, Iijima K, Sugimoto K, Takemura T. A family with X-linked benign familial hematuria. Pediatr Nephrol 2010; 25:545-8. [PMID: 19937058 DOI: 10.1007/s00467-009-1370-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Revised: 10/19/2009] [Accepted: 10/22/2009] [Indexed: 11/24/2022]
Abstract
Gene mutations in COL4A5 located on Xq22 are believed to cause X-linked Alport syndrome, whereas mutations in COL4A3 and COL4A4 located on chromosome 2 are associated with autosomal inherited Alport syndrome or benign familial hematuria. A family with benign familial hematuria caused by COL4A5 mutation, implying X-linked transmission, is reported here for the first time. This result suggests that COL4A5 should be added to the list of causative genes for benign familial hematuria, although the mechanism(s) by which the same mutation leads to the distinct phenotypes, i.e. X-linked Alport syndrome or benign familial hematuria, remains unknown.
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Affiliation(s)
- Kazunari Kaneko
- Department of Pediatrics, Kansai Medical University, 2-3-1 Shin-machi, Hirakata-shi, Osaka 573-1191, Japan.
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20
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Pont-Kingdon G, Sumner K, Gedge F, Miller C, Denison J, Gregory M, Lyon E. Molecular testing for adult type Alport syndrome. BMC Nephrol 2009; 10:38. [PMID: 19919694 PMCID: PMC2780398 DOI: 10.1186/1471-2369-10-38] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 11/17/2009] [Indexed: 11/10/2022] Open
Abstract
Background Alport syndrome (AS) is a progressive renal disease with cochlear and ocular involvement. The majority of AS cases are X-linked (XLAS) and due to mutations in the COL4A5 gene. Although the disease may appear early in life and progress to end stage renal disease (ESRD) in young adults, in other families ESRD occurs in middle age. Few of the more than four hundred mutations described in COL4A5 are associated with adult type XLAS, but the families may be very large. Methods We classified adult type AS mutation by prevalence in the US and we developed a molecular assay using a set of hybridization probes that identify the three most common adult type XLAS mutations; C1564S, L1649R, and R1677Q. Results The test was validated on samples previously determined to contain one or none of these mutations. In the US, the test's clinical specificity and sensitivity are estimated to be higher than 99% and 75% respectively. Analytical specificity and sensitivity are above 99%. Conclusion This test may be useful for presymptomatic and carrier testing in families with one of the mutations and in the diagnosis of unexplained hematuria or chronic kidney disease.
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21
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Liapis H, Foster K, Theodoropoulou E, Monga G, Pizzolitto S, Mazzucco G. Phenotype/Genotype Correlations in the Ultrastructure of Monogenetic Glomerular Diseases. Ultrastruct Pathol 2009; 28:181-97. [PMID: 15693630 DOI: 10.1080/019131290505194] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Electron microscopy defined classic patterns of hereditary glomerular disease long before genetics revealed an underlying specific mutation. Genetic analysis is now easier to perform in clinical practice but an earlier optimism that genetics would predict disease severity and phenotype is challenged. The classic paradigm is Alport nephritis in which only a subset of mutations may predict glomerular abnormalities and disease severity. Interpretation of ultrastructural pathology of monogenetic diseases like Alport nephritis is complicated when the proband is the first family member to be diagnosed or there is discrepancy between clinical presentation and ultrastructural changes. In this review the authors have selected a dozen cases representative of common monogenetic glomerular diseases as a platform to discuss the utility of diagnostic electron microscopy in the era of molecular genetics. The emphasis is on genotype/glomerular phenotype correlations.
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Affiliation(s)
- H Liapis
- Department of Pathology and Immunology, Washington University, St. Louis, Missouri 63131, USA.
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22
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Detection of large deletion mutations in the COL4A5 gene of female Alport syndrome patients. Pediatr Nephrol 2008; 23:2085-90. [PMID: 18584212 DOI: 10.1007/s00467-008-0878-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 04/04/2008] [Accepted: 04/21/2008] [Indexed: 10/21/2022]
Abstract
Alport syndrome is the most common form of hereditary nephritis, and the majority of cases are caused by mutations in the COL4A5 gene. However, direct sequencing by polymerase chain reaction (PCR), from genomic DNA, or reverse transcriptase-polymerase chain reaction (RT-PCR), from mRNA, or polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) has reportedly resulted in detection rates of 31% to 84%, but of only 20% to 71% when restricted to female patients. This report concerns two female patients with X-linked Alport syndrome. Although mutational analysis of the COL4A5 gene was conducted with direct sequencing using genomic DNA and mRNA extracted from leukocytes, the results were negative for detection of mutations. Semi-quantitative PCR using genomic DNA was therefore conducted to detect large heterozygous deletions. The results were that the first patient showed complete loss of the COL4A5 gene and the second patient showed deletion from exons 37 to 51. Our patients possessed large heterozygous deletions in the COL4A5 gene that could not be detected with the standard direct sequencing method and were identified with semi-quantitative PCR. Previously reported mutation detection rates for female patients have been lower than overall rates. Our findings indicate that this difference may, in part, be due to failure to detect this type of mutation with conventional analytical methods.
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Hertz JM, Juncker I, Marcussen N. MLPA and cDNA analysis improves COL4A5 mutation detection in X-linked Alport syndrome. Clin Genet 2008; 74:522-30. [PMID: 18616531 DOI: 10.1111/j.1399-0004.2008.01051.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The X-linked form of Alport syndrome (AS) is caused by mutations in the COL4A5 gene encoding the alpha5 chain of type IV collagen. Most COL4A5 mutations are individual, and mutation analysis is complicated by the size of the gene and the number of exons. Larger structural rearrangements account for 10-15% of mutations. We have established a method for mutation analysis of COL4A5 based on reverse transcriptase-polymerase chain reaction analysis of mRNA from cultured skin fibroblasts and multiplex ligation-dependent probe amplification (MLPA) on genomic DNA. One advantage of using skin biopsies for the mRNA analysis is the possibility of immunohistochemical staining for the alpha5(IV) chain on skin sections to support a diagnosis of X-linked AS. A mutation was detected in all five cases included. One patient presenting with AS and diffuse leiomyomatosis was found to have a COL4A5 deletion extending into and comprising COL4A6 exons 1, 1', and 2. We have evaluated the MLPA assay on samples from 67 previously tested AS patients (45 males and 22 females) and 20 controls. We found that the combination of cDNA and MLPA analysis improves the mutation detection rate in COL4A5 and that MLPA should be the first step in genetic testing for X-linked AS.
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Affiliation(s)
- J M Hertz
- Department of Clinical Genetics, Aarhus University Hospital, Aarhus C, Denmark.
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Zhang H, Ding J, Wang F, Yang H. Prenatal diagnosis and genetic counseling of a Chinese Alport syndrome kindred. ACTA ACUST UNITED AC 2008; 12:1-7. [PMID: 18373399 DOI: 10.1089/gte.2007.0026] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Alport syndrome (AS) is a progressive renal disease characterized by hematuria and progressive renal failure. X-linked dominant AS (XLAS) is the major inheritance form, accounting for almost 80% of the cases, caused by mutations in COL4A5 gene. An accurate genetic diagnosis of AS is very important for genetic counseling and even prenatal diagnosis. In this study we detected mutation of COL4A5 by amplifying the entire coding sequence mRNA of peripheral blood lymphocytes using nested PCR in a Chinese XLAS family, and then performed the first prenatal diagnosis of AS in China. Mutation analysis of the fetus was performed on both cDNA-based level and DNA-based level of amniocytes. Fetus sex was determined by PCR amplification of SRY and karyotypes analysis. Maternal cell contamination was excluded by linkage analysis. There was a G-to-A substitution at position 4,271 in exon 46 of COL4A5 gene (c.G4271A) in the pregnant woman; this genetic variant has not been described previously and was a novel missense mutation. The fetus did not carry the same mutation as the mother. PCR amplification product of SRY and karyotypes analysis revealed a male fetus. Linkage analysis showed that there was no contamination of maternal cells in amniocytes.
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Affiliation(s)
- Hongwen Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, P. R. China
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25
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Tazón-Vega B, Ars E, Burset M, Santín S, Ruíz P, Fernández-Llama P, Ballarín J, Torra R. Genetic testing for X-linked Alport syndrome by direct sequencing of COL4A5 cDNA from hair root RNA samples. Am J Kidney Dis 2007; 50:257.e1-14. [PMID: 17660027 DOI: 10.1053/j.ajkd.2007.05.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Accepted: 05/11/2007] [Indexed: 11/11/2022]
Abstract
BACKGROUND Alport syndrome (AS) is a genetically heterogeneous hereditary renal disease. X-Linked AS (XLAS) is responsible for 80% to 85% of familial cases and is caused by mutations in the COL4A5 collagen gene. To date, indirect molecular diagnosis for XLAS is not well defined, and mutation screening of the COL4A5 gene is time consuming and complicated because of its large size and high allelic heterogeneity. Our aim is to facilitate XLAS genetic testing. METHODS For linkage analysis, we tested the applicability of 4 microsatellite markers defining a 1.2-megabase region flanking the COL4A5 gene. For mutation screening of the COL4A5 gene, we describe a new strategy based on direct sequencing of hair root COL4A5 messenger RNA (mRNA). RESULTS Three microsatellite markers proved accurate (DXS1120, DXS6802, and DXS1210) and 1 was discarded (DXS6797) because it was difficult to interpret. The mutation screening method provides results in 4 days, and when applied to 29 patients suspected of having XLAS, it identified mutations in 76% (22 of 29 patients). This study correlates COL4A5 mutations with effects at the mRNA level and suggests that mutations affecting mRNA splicing of the COL4A5 gene (41%; 9 of 22 patients) are more common than previously described. Many splicing mutations did not alter the canonical 5' and 3' splice sites. CONCLUSIONS A more reliable linkage analysis and a simple, fast, and efficient mutation screening are now available for the genetic testing of patients with XLAS.
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Mroske C, Muci J, Wang J, Li K, Song W, Yan J, Feng J, Liu Q, Sommer SS. Toward a fluorescent single-strand conformation polymorphism technique that detects all mutations: F-DOVAM-S. Anal Biochem 2007; 368:250-7. [PMID: 17618861 PMCID: PMC2729706 DOI: 10.1016/j.ab.2007.05.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Revised: 05/17/2007] [Accepted: 05/19/2007] [Indexed: 11/18/2022]
Abstract
Although DOVAM-S (detection of virtually all mutations-SSCP) in effect detects all mutations and is less costly than direct sequencing, the technique currently requires the use of radioactivity. F-DOVAM-S (fluorescent DOVAM-S) was developed to replace the isotopic label with fluorescence and to increase throughput via dye color multiplexing. As proof of principle, two multitemperature slab gel electrophoresis conditions were evaluated through the blinded analysis of mutations in the factor IX (FIX) genes of 88 hemophilia B (HB) patients and 7 wild-type controls. Using only two conditions, it was determined that F-DOVAM-S had a detection sensitivity of 97%. It is anticipated that when three or four optimized conditions are employed, F-DOVAM-S will detect all mutations. Three patient samples were multiplexed per well using three different fluorescent dyes (6FAM, VIC, and NED), demonstrating that it is possible to analyze up to 44 kb of diploid, color-coded amplification product per gel lane. This value corresponds to a throughput of approximately 4 Mb of DNA analyzed per 96-well gel, which is approximately triple that of conventional radiolabeled DOVAM-S. Throughput is further enhanced by the rapidity at which the fluorescent signal can be captured and the resultant multicolor chromatograms analyzed. Given these data, F-DOVAM-S has the potential to be a particularly powerful technology for clinical diagnosis because it allows the mutation analysis of multiple patients to be performed within 24h.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Steve S. Sommer
- Corresponding author. Fax: +1 626 301 8142 Email address: (S.S. Sommer)
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Slajpah M, Gorinsek B, Berginc G, Vizjak A, Ferluga D, Hvala A, Meglic A, Jaksa I, Furlan P, Gregoric A, Kaplan-Pavlovcic S, Ravnik-Glavac M, Glavac D. Sixteen novel mutations identified in COL4A3, COL4A4, and COL4A5 genes in Slovenian families with Alport syndrome and benign familial hematuria. Kidney Int 2007; 71:1287-95. [PMID: 17396119 DOI: 10.1038/sj.ki.5002221] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Alport syndrome (ATS) and benign familial hematuria (BFH) are type IV collagen inherited disorders. Mutations in COL4A5 are generally believed to cause X-linked ATS, whereas mutations in COL4A3 and COL4A4 genes can be associated with the autosomal-recessive and -dominant type of ATS or BFH. In view of the wide spectrum of phenotypes, an exact diagnosis is sometimes difficult to achieve. This study involved screening each exon with boundary intronic sequences of COL4A3, COL4A4, and COL4A5 genes by optimized polymerase chain reaction-single-stranded conformational polymorphism analysis in 17 families with ATS and in 40 families diagnosed as having BFH. Twelve different mutations were found in the COL4A5 gene in ATS patients, comprising nine missense mutations, a splice site mutation, a mutation causing frameshift, and a nonsense mutation. One of the missense mutations (p.G624D) was present not only in one family with ATS but also in five families with suspected BFH. Three heterozygous mutations in the COL4A3 gene (two missense and one frameshift) and four heterozygous mutations in COL4A4 (two splice site, one in-frame deletion, and one missense) were identified in patients with BFH. Sixteen mutations are to the best of our knowledge new and private.
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Affiliation(s)
- M Slajpah
- Department of Molecular Genetics, Institute of Pathology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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28
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Hofman-Bang J, Behr ER, Hedley P, Tfelt-Hansen J, Kanters JK, Haunsøe S, McKenna WJ, Christiansen M. High-efficiency multiplex capillary electrophoresis single strand conformation polymorphism (multi-CE-SSCP) mutation screening of SCN5A: a rapid genetic approach to cardiac arrhythmia. Clin Genet 2006; 69:504-11. [PMID: 16712702 DOI: 10.1111/j.1399-0004.2006.00621.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mutations in the SCN5A gene coding for the alpha-subunit of the cardiac Na(+) ion channel cause long QT syndrome, Brugada syndrome, idiopathic ventricular fibrillation, sick sinus node syndrome, progressive conduction disease, dilated cardiomyopathy and atrial standstill. These diseases exhibit variable expressivity, and identification of gene carriers is clinically important, particularly in sudden infant and adult death syndromes. The SCN5A gene comprises 28 exons distributed over 100 kbp of genomic sequence at chromosome 3p21. Disease-causing mutations are private and scattered over the DNA sequence, making it difficult to screen for specific mutations. We developed a multiplex capillary-electrophoresis single-strand conformation polymorphism (Multi-CE-SSCP) mutation screening protocol on the ABI 3100 platform and applied it to 10 previously slab-gel SSCP identified mutations and SNPs and used it to identify one novel deletion. The method is highly efficient, with a turnover of 23 patients per 24 h and a false positive rate of 0.5% of the analyzed amplicons. Each variant has a particular elution pattern, and all 20 carriers of the H558R polymorphism out of 57 persons were correctly identified. We suggest that the method could become part of routine work-up of patients with suspicious syncope and of members of families with sudden unexplained death.
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Affiliation(s)
- J Hofman-Bang
- Copenhagen Heart Arrhythmia Research Center, Statens Serum Institut, Copenhagen, Denmark.
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29
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Hertz JM, Persson U, Juncker I, Segelmark M. Alport syndrome caused by inversion of a 21 Mb fragment of the long arm of the X-chromosome comprising exon 9 through 51 of the COL4A5 gene. Hum Genet 2005; 118:23-8. [PMID: 16133187 DOI: 10.1007/s00439-005-0013-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Accepted: 06/02/2005] [Indexed: 10/25/2022]
Abstract
The X-linked form of Alport syndrome (AS) is caused by mutation in the COL4A5 gene located at Xq22.3 and encoding the alpha5-chain of type IV-collagen. More than 400 different mutations have so far been detected in the COL4A5 gene. Not all mutations, however, will be detected using an exon-by-exon mutation detection strategy such as SSCP analysis or direct sequencing. We have previously reported the results of SSCP analysis of 81 patients suspected of X-linked AS. Genomic DNA from these 81 patients was also analyzed for larger genomic rearrangements, using Southern blotting analysis. Abnormal band patterns were found in three patients, two of which were caused by single base substitutions in the coding region, also detected by the SSCP analysis. Here we report the results of the analysis of a larger structural COL4A5 rearrangement that escaped the SSCP analysis. The rearrangement was found to be an inversion of a 21 Mb fragment of the COL4A5 gene comprising exon 9 through 51 with proximal breakpoint within intron 8 at Xq22.3 and a distal breakpoint 56 kb upstream to the initiation codon in the RAB33A gene at Xq25. The inversion of exon 9 through 51 is expected to result in a truncated or absent alpha5(IV)-chain and has not previously been associated with AS. These findings emphasize the need for a supplement to mutation detection strategies such as SSCP analysis and direct sequencing, in order to detect more complicated structural COL4A5 rearrangements. Larger structural rearrangements constitute 2.3% (1/43) of the mutations in the present material.
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Affiliation(s)
- Jens Michael Hertz
- Department of Clinical Genetics, Aarhus University Hospital, DK, 8000, Aarhus C, Denmark.
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30
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Wang F, Wang Y, Ding J, Yang J. Detection of mutations in the COL4A5 gene by analyzing cDNA of skin fibroblasts. Kidney Int 2005; 67:1268-74. [PMID: 15780079 DOI: 10.1111/j.1523-1755.2005.00204.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Alport syndrome is a progressive hereditary glomerulonephritis that is characterized by hematuria, sensorineural deafness, ocular lesions, and progressive renal failure. The majority of cases (about 85%) are caused by mutations in the COL4A5 gene on the X chromosome which encodes the type IV collagen alpha5 chain (X-linked Alport syndrome). METHODS In this study we performed a systematic analysis of the entire coding region of COL4A5 mRNA in 31 unrelated Chinese X-linked Alport syndrome patients and four controls by using reverse transcription-polymerase chain reaction (RT-PCR) and direct sequencing methods. The mRNA analyzed was isolated from cultured skin fibroblasts of Alport syndrome patients. RESULTS The entire sequences of mRNA of the controls corresponded exactly to the published sequence. There were 28 variants detected by analyzing mRNA of COL4A5 in 28/31 patients. Of those, a total of 25 functionally significant COL4A5 mutations was confirmed in 25/31 patients by using RT-PCR method and subsequently confirmed at genomic DNA level, which included seven different mutations described in previous reports, and 18 novel mutations. The mutation detection rate was 80.6% (25/31), which is comparable with the highest previous detection sensitivity of COL4A5 mutations in evident X-linked Alport syndrome using genomic DNA. Furthermore, three splicing mutations that occurred at the cryptic splice sites and would be overlooked or simply considered as intronic sequence variations by solely analyzing genomic DNA were identified in this study. CONCLUSION RT-PCR and direct sequencing using cultured skin fibroblasts RNA is a practical approach with high sensitivity for genetic analysis in X-linked Alport syndrome patients.
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Affiliation(s)
- Fang Wang
- Department of Pediatrics, Peking University First Hospital, Beijing, People's Republic of China
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31
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Wang YY, Rana K, Tonna S, Lin T, Sin L, Savige J. COL4A3 mutations and their clinical consequences in thin basement membrane nephropathy (TBMN). Kidney Int 2004; 65:786-90. [PMID: 14871398 DOI: 10.1111/j.1523-1755.2004.00453.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Thin basement membrane nephropathy (TBMN) is often caused by mutations in the COL4A3 and COL4A4 genes. METHODS We examined 62 unrelated individuals diagnosed with TBMN by renal biopsy (N= 49, 79%) or a positive family history of hematuria but without a biopsy (N= 13, 21%) for mutations in the COL4A3 gene and the COL4A3/COL4A4 promoter. All 52 exons of COL4A3 as well as the COL4A3/COL4A4 promoter were screened with single-stranded conformational polymorphism (SSCP) analysis at 4 degrees C and at room temperature. Amplicons that demonstrated electrophoretic abnormalities were sequenced. RESULTS Seven mutations were demonstrated in seven patients: G532C and G584C in exon 25, G596R in exon 26, G695R in exon 28, and IVS 2224 - 11C>T, IVS 2980 + 1G>A and IVS 3518 - 7C>G. No mutations were found in the COL4A3/COL4A4 promoter. Four novel polymorphisms or variants (P116T in exon 6, P690P in exon 27, and G895G and A899A in exon 33) were also demonstrated. In addition, P1109S and Q1495R, which had been described previously but whose status was unclear, were shown to be polymorphisms. All seven mutations described here were associated with hematuria. While one mutation (2980 + 1G>A) was found in an individual who also had proteinuria, none of her family members with the same mutation had increased urinary protein. None of the patients with these seven mutations had renal impairment. Hematuria was completely penetrant in families with the G532C, G584C, G596R, and IVS 2980 + 1G>A mutations but not with the G695R and IVS 3518 - 7C>G mutations. CONCLUSION COL4A3 mutations are common in TBMN.
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Affiliation(s)
- Yan Yan Wang
- University of Melbourne Department of Medicine, Austin and Repatriation Medical Centre, Heidelberg, Victoria, Australia
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32
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Jais JP, Knebelmann B, Giatras I, De Marchi M, Rizzoni G, Renieri A, Weber M, Gross O, Netzer KO, Flinter F, Pirson Y, Dahan K, Wieslander J, Persson U, Tryggvason K, Martin P, Hertz JM, Schröder C, Sanak M, Carvalho MF, Saus J, Antignac C, Smeets H, Gubler MC. X-linked Alport syndrome: natural history and genotype-phenotype correlations in girls and women belonging to 195 families: a "European Community Alport Syndrome Concerted Action" study. J Am Soc Nephrol 2004; 14:2603-10. [PMID: 14514738 DOI: 10.1097/01.asn.0000090034.71205.74] [Citation(s) in RCA: 295] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Alport syndrome (AS) is a type IV collagen hereditary disease characterized by progressive hematuric nephritis, hearing loss, and ocular changes. Mutations in the COL4A5 collagen gene are responsible for the more common X-linked dominant form of the disease characterized by much less severe disease in girls and women. A "European Community Alport Syndrome Concerted Action" (ECASCA) group was established to delineate the Alport syndrome phenotype in each gender and to determine genotype-phenotype correlations in a large number of families. Data concerning 329 families, 250 of them with an X-linked transmission, were collected. Characteristics of heterozygous girls and women belonging to the 195 families with proven COL4A5 mutation are compared with those of hemizygous boys and men. Hematuria was observed in 95% of carriers and consistently absent in the others. Proteinuria, hearing loss, and ocular defects developed in 75%, 28%, and 15%, respectively. The probability of developing end-stage renal disease or deafness before the age of 40 yr was 12% and 10%, respectively, in girls and women versus 90 and 80%, respectively, in boys and men. The risk of progression to end-stage renal disease appears to increase after the age of 60 yr in women. Because of the absence of genotype-phenotype correlation and the large intrafamilial phenotypic heterogeneity, early prognosis of the disease in X-linked Alport syndrome carriers remains moot. Risk factors for developing renal failure have been identified: the occurrence and progressive increase in proteinuria, and the development of a hearing defect.
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Affiliation(s)
- Jean Philippe Jais
- Biostatistique et Informatique Médicale, Hôpital Necker Enfants Malades, Université René Descartes, Paris, France
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Wang YF, Ding J, Wang F, Bu DF. Effect of glycine substitutions on alpha5(IV) chain structure and structure-phenotype correlations in Alport syndrome. Biochem Biophys Res Commun 2004; 316:1143-9. [PMID: 15044104 DOI: 10.1016/j.bbrc.2004.02.168] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2004] [Indexed: 01/22/2023]
Abstract
The phenotype variety caused by glycine substitutions in alpha5(IV) chain in X-linked Alport syndrome (XLAS) prompted the complexity of structure changes of alpha5(IV) chain that was little to know now. In this study, we expressed a domain of alpha5(IV) chain containing different glycine substitutions (G1015V and G1030S, respectively) which were revealed in two XLAS pedigrees with different phenotype severities and the corresponding domain of a control in Escherichia coli. The recombinant proteins were characterized by immunoblot and mass spectrometry and analyzed the secondary structure by using circular dichroism (CD) spectroscopy. CD analysis showed that the recombinant protein containing G1015V mutation identified in the pedigree of juvenile-onset XLAS exhibited 12.9% alpha-helix that was not found in the control recombinant protein. The spectrum of the recombinant protein containing G1030S mutation identified in the pedigree of adult-onset XLAS was slightly different from that of the control, that is, mostly with the random coil and the beta-sheet, while without alpha-helix. These results demonstrated that two kinds of glycine substitutions, although in the same domain of alpha5(IV) chain, displayed the distinctly different secondary structures. The changes of the secondary structure could explain the phenotypic diversities of XLAS, which would be hardly understood solely by analyzing genomic DNA or mRNA of alpha5(IV) chain.
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Affiliation(s)
- Yun-Feng Wang
- Department of Pediatrics, Peking University First Hospital, Beijing, PR China
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Tazón Vega B, Badenas C, Ars E, Lens X, Milà M, Darnell A, Torra R. Autosomal recessive Alport's syndrome and benign familial hematuria are collagen type IV diseases. Am J Kidney Dis 2004; 42:952-9. [PMID: 14582039 DOI: 10.1016/j.ajkd.2003.08.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
BACKGROUND Alport's syndrome (AS) is a genetically heterogeneous renal hereditary disease. Mutations in collagen type IV genes have been described to be responsible for X-linked (COL4A5), autosomal recessive, and autosomal dominant AS (COL4A3/COL4A4). Moreover, at least 40% of benign familial hematuria (BFH) cases cosegregate with the COL4A3/COL4A4 loci, following a dominant pattern of inheritance. Therefore, it has been suggested that BFH may represent the carrier state for autosomal recessive AS. METHODS We report a mutational study of the COL4A3 and COL4A4 genes in 14 AS and 2 BFH families. When possible, linkage analysis has been performed to confirm the pattern of inheritance. One affected proband from each family underwent mutation screening by single-strand conformation polymorphism/heteroduplex analysis. RESULTS We identified 13 mutations within the COL4A3 gene and 2 mutations within the COL4A4 gene, 9 of which are first reported here. We also detected 14 polymorphisms within the COL4A3 gene and 15 polymorphisms within the COL4A4 gene, 7 of them not previously described. In 2 of our AS families, we found mutations previously reported for BFH, and we characterized a novel mutation shared by an AS and a BFH family. CONCLUSION Collagen type IV nephropathy is an entity in itself, and phenotypic manifestations of COL4A3/COL4A4 mutations may range from monosymptomatic hematuria (BFH) to severe renal failure (AS), depending on the gene dosage. In 3 of our families, we genetically confirmed that BFH represents the carrier state for autosomal recessive AS.
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Affiliation(s)
- Bárbara Tazón Vega
- Laboratory Department, Molecular Biology Laboratory, Fundació Puigvert, Barcelona, Spain
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