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Nozu K, Takaoka Y, Kai H, Takasato M, Yabuuchi K, Yamamura T, Horinouchi T, Sakakibara N, Ninchoji T, Nagano C, Iijima K. Genetic background, recent advances in molecular biology, and development of novel therapy in Alport syndrome. Kidney Res Clin Pract 2020; 39:402-413. [PMID: 33214343 PMCID: PMC7771000 DOI: 10.23876/j.krcp.20.111] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/06/2020] [Accepted: 08/08/2020] [Indexed: 12/18/2022] Open
Abstract
Alport syndrome (AS) is a progressive inherited kidney disease characterized by hearing loss and ocular abnormalities. There are three forms of AS depending on inheritance mode: X-linked Alport syndrome (XLAS), autosomal recessive AS (ARAS), and autosomal dominant AS (ADAS). XLAS is caused by pathogenic variants in COL4A5, which encodes type IV collagen α5 chain, while ADAS and ARAS are caused by variants in COL4A3 or COL4A4, which encode type IV collagen α3 or α4 chain, respectively. In male XLAS or ARAS cases, end-stage kidney disease (ESKD) develops around a median age of 20 to 30 years old, while female XLAS or ADAS cases develop ESKD around a median age of 60 to 70 years old. The diagnosis of AS is dependent on either genetic or pathological findings. However, determining the pathogenicity of the variants detected by gene tests can be difficult. Recently, we applied the following molecular investigation tools to determine pathogenicity: 1) in silico and in vitro trimer formation assay of α345 chains to assess triple helix formation ability, 2) kidney organoids constructed from patients’ induced pluripotent stem cells to identify α5 chain expression on the glomerular basement membrane, and 3) in vitro splicing assay to detect aberrant splicing to determine the pathogenicity of variants. In this review article, we discuss the genetic background and novel assays for determining the pathogenicity of variants. We also discuss the current treatment approaches and introduce exon skipping therapy as one potential treatment option.
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Affiliation(s)
- Kandai Nozu
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yutaka Takaoka
- Division of Medical Informatics and Bioinformatics, Kobe University Hospital, Kobe, Japan
| | - Hirofumi Kai
- Department of Molecular Medicine, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
| | - Minoru Takasato
- Laboratory for Human Organogenesis, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan.,Laboratory of Molecular Cell Biology and Development, Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kensuke Yabuuchi
- Laboratory for Human Organogenesis, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Tomohiko Yamamura
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Tomoko Horinouchi
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Nana Sakakibara
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Takeshi Ninchoji
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - China Nagano
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Kazumoto Iijima
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
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Aoto Y, Kise T, Nakanishi K, Nagano C, Horinouchi T, Yamamura T, Ishiko S, Sakakibara N, Shima Y, Morisada N, Iijima K, Nozu K. A case with somatic and germline mosaicism in COL4A5 detected by multiplex ligation-dependent probe amplification in X-linked Alport syndrome. CEN Case Rep 2020; 9:431-436. [PMID: 32621070 DOI: 10.1007/s13730-020-00503-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 06/28/2020] [Indexed: 01/19/2023] Open
Abstract
X-linked Alport syndrome (XLAS) is a progressive hereditary kidney disease caused by mutations in the COL4A5 gene encoding the type IV collagen α5 chain. To date, 11 cases having somatic mosaic variants in COL4A5 have been reported; however, all of them involved single-nucleotide variations (SNVs). Here, we report a female XLAS patient with somatic mosaicism identified by copy number variation (CNV) in COL4A5. The case was a 35-year-old female, the mother of the proband, whose only clinical symptom was hematuria. The proband, who was the son of this patient, was diagnosed with XLAS by gene testing, which showed a large hemizygous deletion from exon 3-51 in COL4A5 detected by next-generation sequencing and then confirmed by multiplex ligation-dependent probe amplification (MLPA). Then, MLPA analysis revealed that the female patient had the same deletion with only a 20% copy number reduction compared with a normal female control; she was thus diagnosed with XLAS with somatic mosaicism. CNVs in COL4A5 are relatively rare and, to the best of our knowledge, somatic mosaic variants with CNVs have never been reported. This case clearly featured a germline variant because the patient's son exhibited XLAS. This is thus the first case report on an XLAS patient having CNV in COL4A5 with somatic mosaicism. The obtained findings were very important for the genetic counseling of this family.
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Affiliation(s)
- Yuya Aoto
- Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
| | - Tomoo Kise
- Division of Pediatric Nephrology, Okinawa Prefectural Nanbu Medical Center, Children's Medical Center, 118-1 Arakawa, Haebaru-cho, Simajiri-gun, Okinawa, 901-1105, Japan
| | - Koichi Nakanishi
- Department of Pediatrics, Graduate School of Medicine, University of the Ryukyus, 207 Uehara, Nishihara-cho, Nakagami-gun, Okinawa, 903-0125, Japan
| | - China Nagano
- Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan
| | - Tomoko Horinouchi
- Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan
| | - Tomohiko Yamamura
- Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan
| | - Shinya Ishiko
- Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan
| | - Nana Sakakibara
- Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan
| | - Yuko Shima
- Department of Pediatrics, Wakayama Medical University, 811-1 Kimiidera, Wakayama, 641-8509, Japan
| | - Naoya Morisada
- Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan
| | - Kazumoto Iijima
- Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan
| | - Kandai Nozu
- Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan
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Characterization of contiguous gene deletions in COL4A6 and COL4A5 in Alport syndrome-diffuse leiomyomatosis. J Hum Genet 2017; 62:733-735. [PMID: 28275241 DOI: 10.1038/jhg.2017.28] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 01/31/2017] [Accepted: 01/31/2017] [Indexed: 11/08/2022]
Abstract
Alport syndrome-diffuse leiomyomatosis (AS-DL, OMIM: 308940) is a rare variant of the X-linked Alport syndrome that shows overgrowth of visceral smooth muscles in the gastrointestinal, respiratory and female reproductive tracts in addition to renal symptoms. AS-DL results from deletions that encompass the 5' ends of the COL4A5 and COL4A6 genes, but deletion breakpoints between COL4A5 and COL4A6 have been determined in only four cases. Here, we characterize deletion breakpoints in five AS-DL patients and show a contiguous COL4A6/COL4A5 deletion in each case. We also demonstrate that eight out of nine deletion alleles involved sequences homologous between COL4A5 and COL4A6. Most breakpoints took place in recognizable transposed elements, including long and short interspersed repeats, DNA transposons and long-terminal repeat retrotransposons. Because deletions involved the bidirectional promoter region in each case, we suggest that the occurrence of leiomyomatosis in AS-DL requires inactivation of both genes. Altogether, our study highlights the importance of homologous recombination involving multiple transposed elements for the development of this continuous gene syndrome and other atypical loss-of-function phenotypes.
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Syndrome d’Alport : néphropathie héréditaire associée à des mutations dans les gènes codant les chaînes de collagène de type IV. Nephrol Ther 2016; 12:544-551. [DOI: 10.1016/j.nephro.2016.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Kim MS, Kang HJ, Park HJ, Yook YJ, Han BD, Kim CW, Kim NH, Lee JW, Kim H, Park KD, Shin HY, Ahn HS. Development of multiplex PCR method for the analysis of glutathione s-transferase polymorphism. Mol Diagn Ther 2012; 15:285-92. [PMID: 22047155 DOI: 10.1007/bf03256420] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
BACKGROUND Busulfan is a key compound in myeloablative chemotherapy before hematopoietic stem-cell transplantation in children. Genetic polymorphisms of glutathione S-transferase (GST), which is involved in the metabolism of busulfan, have been implicated in interindividual variability in busulfan pharmacokinetics. Development of a rapid and simplified method for polygenic analysis of GST may facilitate large pharmacogenetic studies and clinical application of individualized busulfan dose adjustment. We previously introduced an effective PCR method for analyzing multiple genes using a small amount of DNA, termed 'TotalPlex amplification'. OBJECTIVE The aim of this study was to extend the application of the TotalPlex method to the specific GST gene families (A1, P1, M1, and T1) that are related to busulfan metabolism, and thereby facilitate pharmacogenetic analysis of GST polymorphisms. METHODS Seven genetic polymorphisms (GSTA1 promoter -52G>A, -69C>T, -567T>G, and -631T>G; GSTP1 313A>G; GSTM1 deletion; and GSTT1 deletion) were analyzed by multiplex PCR and genotyping, and the genotyping results from TotalPlex were verified with those from uniplex PCR. RESULTS Using five pairs of specific bulging-specific primers, seven specific gene fragments were successfully amplified by multiplex amplification coupled to a multiplexed bead array detection system, with a smaller amount of DNA and a shorter process time than is needed for the conventional approach. The genotypes of seven loci from 30 different genomic DNA samples derived using the multiplex system were consistent with the results of standard genotyping methods. CONCLUSION Our multiplex system provides a fast, inexpensive, and accurate method of detecting multiple GST polymorphisms (GSTA1, GSTP1, GSTM1, and GSTT1).
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Affiliation(s)
- Min Sun Kim
- Department of Pediatrics, Cancer Research Institute, Seoul National University College of Medicine, South Korea
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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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Lo YF, Nozu K, Iijima K, Morishita T, Huang CC, Yang SS, Sytwu HK, Fang YW, Tseng MH, Lin SH. Recurrent deep intronic mutations in the SLC12A3 gene responsible for Gitelman's syndrome. Clin J Am Soc Nephrol 2010; 6:630-9. [PMID: 21051746 DOI: 10.2215/cjn.06730810] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND AND OBJECTIVES Gitelman's syndrome (GS) is an autosomal recessive renal tubular disorder caused by mutations in the SLC12A3 gene encoding the thiazide-sensitive Na(+)-Cl(-) cotransporter (NCC). Despite meticulous sequencing of genomic DNA, approximately one-third of GS patients are negative or heterozygotes for the known mutations. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Because blood leukocytes express NCC mRNA, we evaluate whether deep intronic mutations contribute to GS patients with uniallelic or undetectable SLC12A3 mutations. Twenty-nine patients with GS (men/women = 16/13), including eight negative and 21 uniallelic SLC12A3 mutations from 19 unrelated families, and normal controls were enrolled in an academic medical center. Analysis of cDNA from blood leukocytes, sequencing of the corresponding introns of genomic DNA for abnormal transcript, and analysis of NCC protein expression from renal biopsy were performed. RESULTS We identified nine Taiwan aboriginal patients carrying c.1670-191C→T mutations in intron 13 and 10 nonaboriginal patients carrying c.2548+253C→T mutations in intron 21 from 14 families (14/19). These two mutations undetected in 100 healthy subjects created pseudoexons containing new premature termination codons. Haplotype analysis with markers flanking SLC12A3 revealed that both mutations did not have founder effects. Apical NCC expression in the DCT of renal tissue was markedly diminished in two patients carrying deep intronic mutations. CONCLUSIONS Deep intronic mutations in SLC12A3 causing defective NCC expression can be identified with the RNA-based approach in patients with GS. c.1670-191C→T and c.2548+253C→T are hot spot mutations that can be screened in GS patients with uniallelic or negative SLC12A3 mutations.
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Affiliation(s)
- Yi-Fen Lo
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
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