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Puapatanakul P, Miner JH. Alport syndrome and Alport kidney diseases - elucidating the disease spectrum. Curr Opin Nephrol Hypertens 2024; 33:283-290. [PMID: 38477333 PMCID: PMC10990029 DOI: 10.1097/mnh.0000000000000983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2024]
Abstract
PURPOSE OF REVIEW With the latest classification, variants in three collagen IV genes, COL4A3 , COL4A4 , and COL4A5 , represent the most prevalent genetic kidney disease in humans, exhibiting diverse, complex, and inconsistent clinical manifestations. This review breaks down the disease spectrum and genotype-phenotype correlations of kidney diseases linked to genetic variants in these genes and distinguishes "classic" Alport syndrome (AS) from the less severe nonsyndromic genetically related nephropathies that we suggest be called "Alport kidney diseases". RECENT FINDINGS Several research studies have focused on the genotype-phenotype correlation under the latest classification scheme of AS. The historic diagnoses of "benign familial hematuria" and "thin basement membrane nephropathy" linked to heterozygous variants in COL4A3 or COL4A4 are suggested to be obsolete, but instead classified as autosomal AS by recent expert consensus due to a significant risk of disease progression. SUMMARY The concept of Alport kidney disease extends beyond classic AS. Patients carrying pathogenic variants in any one of the COL4A3/A4/A5 genes can have variable phenotypes ranging from completely normal/clinically unrecognizable, hematuria without or with proteinuria, or progression to chronic kidney disease and kidney failure, depending on sex, genotype, and interplays of other genetic as well as environmental factors.
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Affiliation(s)
- Pongpratch Puapatanakul
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Jeffrey H. Miner
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
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Xiao T, Zhang J, Liu L, Zhang B. Genetic diagnosis of Alport syndrome in 16 Chinese families. Mol Genet Genomic Med 2024; 12:e2406. [PMID: 38433557 PMCID: PMC10910213 DOI: 10.1002/mgg3.2406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 05/05/2023] [Accepted: 02/07/2024] [Indexed: 03/05/2024] Open
Abstract
BACKGROUND Alport syndrome (AS) is a genetically heterogeneous disorder resulting from mutations in the collagen IV genes COL4A3, COL4A4, and COL4A5. The genetic diagnosis of AS is very important to make precise diagnosis and achieve optimal outcomes. METHODS In this study, 16 Chinese families with suspected AS were recruited after pedigree analysis, and the clinical presentations were analyzed by a nephrologist. The genetic diagnosis was performed by whole-exome sequencing (WES) and the disease-causing variants were confirmed by Sanger sequencing. RESULTS The cohort of probands included seven men and nine women, with a mean age of 19.9 years. Pathological analysis showed slight-to-moderate mesangial proliferation, and thin basement membrane was the main findings. Pathogenic variants were revealed by WES in each family, and the co-segregation with renal presentation was confirmed by PCR. In addition, RT-PCR analysis showed that the intronic variant led to aberrant splicing. CONCLUSION Our findings expand the spectrum of AS gene variation, which will inform genetic diagnosis and add to the theoretical basis for the prevention of AS.
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Affiliation(s)
- Tangli Xiao
- Department of Nephrology, the Key Laboratory for the Prevention and Treatment of Chronic Kidney Disease of Chongqing, Chongqing Clinical Research Center of Kidney and Urology DiseasesXinqiao Hospital, Army Medical University (Third Military Medical University)ChongqingP.R. China
| | - Jun Zhang
- Department of Nephrology, the Key Laboratory for the Prevention and Treatment of Chronic Kidney Disease of Chongqing, Chongqing Clinical Research Center of Kidney and Urology DiseasesXinqiao Hospital, Army Medical University (Third Military Medical University)ChongqingP.R. China
| | - Li Liu
- Department of Nephrology, the Key Laboratory for the Prevention and Treatment of Chronic Kidney Disease of Chongqing, Chongqing Clinical Research Center of Kidney and Urology DiseasesXinqiao Hospital, Army Medical University (Third Military Medical University)ChongqingP.R. China
| | - Bo Zhang
- Department of Nephrology, the Key Laboratory for the Prevention and Treatment of Chronic Kidney Disease of Chongqing, Chongqing Clinical Research Center of Kidney and Urology DiseasesXinqiao Hospital, Army Medical University (Third Military Medical University)ChongqingP.R. China
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Plevova P, Indrakova J, Savige J, Kuhnova P, Tvrda P, Cerna D, Hilscherova S, Kudrejova M, Polendova D, Jaklova R, Langova M, Jahnova H, Lastuvkova J, Dusek J, Gut J, Vlckova M, Solarova P, Kreckova G, Kantorova E, Soukalova J, Slavkovsky R, Zapletalova J, Tichy T, Thomasova D. A founder COL4A4 pathogenic variant resulting in autosomal recessive Alport syndrome accounts for most genetic kidney failure in Romani people. Front Med (Lausanne) 2023; 10:1096869. [PMID: 36844206 PMCID: PMC9948603 DOI: 10.3389/fmed.2023.1096869] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Accepted: 01/11/2023] [Indexed: 02/10/2023] Open
Abstract
Introduction Romani people have a high prevalence of kidney failure. This study examined a Romani cohort for pathogenic variants in the COL4A3, COL4A4, and COL4A5 genes that are affected in Alport syndrome (AS), a common cause of genetic kidney disease, characterized by hematuria, proteinuria, end-stage kidney failure, hearing loss, and eye anomalies. Materials and methods The study included 57 Romani from different families with clinical features that suggested AS who underwent next-generation sequencing (NGS) of the COL4A3, COL4A4, and COL4A5 genes, and 83 family members. Results In total, 27 Romani (19%) had autosomal recessive AS caused by a homozygous pathogenic c.1598G>A, p.Gly533Asp variant in COL4A4 (n = 20) or a homozygous c.415G>C, p.Gly139Arg variant in COL4A3 (n = 7). For p.Gly533Asp, 12 (80%) had macroscopic hematuria, 12 (63%) developed end-stage kidney failure at a median age of 22 years, and 13 (67%) had hearing loss. For p.Gly139Arg, none had macroscopic hematuria (p = 0.023), three (50%) had end-stage kidney failure by a median age of 42 years (p = 0.653), and five (83%) had hearing loss (p = 0.367). The p.Gly533Asp variant was associated with a more severe phenotype than p.Gly139Arg, with an earlier age at end-stage kidney failure and more macroscopic hematuria. Microscopic hematuria was very common in heterozygotes with both p.Gly533Asp (91%) and p.Gly139Arg (92%). Conclusion These two founder variants contribute to the high prevalence of kidney failure in Czech Romani. The estimated population frequency of autosomal recessive AS from these variants and consanguinity by descent is at least 1:11,000 in Czech Romani. This corresponds to a population frequency of autosomal dominant AS from these two variants alone of 1%. Romani with persistent hematuria should be offered genetic testing.
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Affiliation(s)
- Pavlina Plevova
- Department of Clinical and Molecular Pathology and Medical Genetics, University Hospital Ostrava, Ostrava, Czechia,Department of Biomedical Sciences, Faculty of Medicine, University of Ostrava, Ostrava, Czechia,*Correspondence: Pavlina Plevova,
| | - Jana Indrakova
- Department of Clinical and Molecular Pathology and Medical Genetics, University Hospital Ostrava, Ostrava, Czechia
| | - Judy Savige
- Department of Medicine (Melbourne Health and Northern Health), The University of Melbourne, Royal Melbourne Hospital, Melbourne, Australia
| | - Petra Kuhnova
- Department of Clinical and Molecular Pathology and Medical Genetics, University Hospital Ostrava, Ostrava, Czechia
| | - Petra Tvrda
- Department of Clinical and Molecular Pathology and Medical Genetics, University Hospital Ostrava, Ostrava, Czechia
| | - Dita Cerna
- Department of Clinical and Molecular Pathology and Medical Genetics, University Hospital Ostrava, Ostrava, Czechia
| | - Sarka Hilscherova
- Department of Clinical and Molecular Pathology and Medical Genetics, University Hospital Ostrava, Ostrava, Czechia
| | - Monika Kudrejova
- Department of Clinical and Molecular Pathology and Medical Genetics, University Hospital Ostrava, Ostrava, Czechia
| | - Daniela Polendova
- Department of Medical Genetics, Faculty of Medicine in Plzeň, Charles University and University Hospital Plzeň, Plzeň, Czechia
| | - Radka Jaklova
- Department of Medical Genetics, Faculty of Medicine in Plzeň, Charles University and University Hospital Plzeň, Plzeň, Czechia
| | - Martina Langova
- Department of Medical Genetics, Thomayer University Hospital, Prague, Czechia
| | - Helena Jahnova
- Department of Pediatrics, Third Faculty of Medicine, Charles University and University Hospital Královské Vinohrady, Prague, Czechia
| | - Jana Lastuvkova
- Department of Medical Genetics, Krajská zdravotní, a.s., Masaryk Hospital in Ústí nad Labem, Ústí nad Labem, Czechia
| | - Jiri Dusek
- Department of Pediatrics, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czechia
| | - Josef Gut
- Department of Pediatrics, Hospital Česká Lípa, Česká Lípa, Czechia
| | - Marketa Vlckova
- Department of Biology and Medical Genetics, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czechia
| | - Pavla Solarova
- Department of Medical Genetics, University Hospital Hradec Králové, Hradec Králové, Czechia
| | | | - Eva Kantorova
- Department of Medical Genetics, Hospital České Budějovice a.s., České Budějovice, Czechia
| | - Jana Soukalova
- Department of Medical Genetics and Genomics, University Hospital Brno, Brno, Czechia
| | - Rastislav Slavkovsky
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacký University Olomouc, Olomouc, Czechia
| | - Jana Zapletalova
- Department of Medical Biophysics, Faculty of Medicine and Dentistry, Palacký University Olomouc, Olomouc, Czechia
| | - Tomas Tichy
- Institute of Clinical and Molecular Pathology, Faculty of Medicine and Dentistry, Palacký University Olomouc, Olomouc, Czechia
| | - Dana Thomasova
- Department of Biology and Medical Genetics, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czechia
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Prevalence of hereditary tubulointerstitial kidney diseases in the German Chronic Kidney Disease study. Eur J Hum Genet 2022; 30:1413-1422. [PMID: 36100708 PMCID: PMC9712573 DOI: 10.1038/s41431-022-01177-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 07/14/2022] [Accepted: 08/15/2022] [Indexed: 11/09/2022] Open
Abstract
Hereditary chronic kidney disease (CKD) appears to be more frequent than the clinical perception. Exome sequencing (ES) studies in CKD cohorts could identify pathogenic variants in ~10% of individuals. Tubulointerstitial kidney diseases, showing no typical clinical/histologic finding but tubulointerstitial fibrosis, are particularly difficult to diagnose. We used a targeted panel (29 genes) and MUC1-SNaPshot to sequence 271 DNAs, selected in defined disease entities and age cutoffs from 5217 individuals in the German Chronic Kidney Disease cohort. We identified 33 pathogenic variants. Of these 27 (81.8%) were in COL4A3/4/5, the largest group being 15 COL4A5 variants with nine unrelated individuals carrying c.1871G>A, p.(Gly624Asp). We found three cysteine variants in UMOD, a novel missense and a novel splice variant in HNF1B and the homoplastic MTTF variant m.616T>C. Copy-number analysis identified a heterozygous COL4A5 deletion, and a HNF1B duplication/deletion, respectively. Overall, pathogenic variants were present in 12.5% (34/271) and variants of unknown significance in 9.6% (26/271) of selected individuals. Bioinformatic predictions paired with gold standard diagnostics for MUC1 (SNaPshot) could not identify the typical cytosine duplication ("c.428dupC") in any individual, implying that ADTKD-MUC1 is rare. Our study shows that >10% of selected individuals carry disease-causing variants in genes partly associated with tubulointerstitial kidney diseases. COL4A3/4/5 genes constitute the largest fraction, implying they are regularly overlooked using clinical Alport syndrome criteria and displaying the existence of phenocopies. We identified variants easily missed by some ES pipelines. The clinical filtering criteria applied enriched for an underlying genetic disorder.
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Novel and Founder Pathogenic Variants in X-Linked Alport Syndrome Families in Greece. Genes (Basel) 2022; 13:genes13122203. [PMID: 36553470 PMCID: PMC9778032 DOI: 10.3390/genes13122203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 11/08/2022] [Accepted: 11/18/2022] [Indexed: 11/27/2022] Open
Abstract
Alport syndrome (AS) is the most frequent monogenic inherited glomerulopathy and is also genetically and clinically heterogeneous. It is caused by semi-dominant pathogenic variants in the X-linked COL4A5 (NM_000495.5) gene or recessive variants in the COL4A3/COL4A4 (NM_000091.4/NM_000092.4) genes. The disease manifests in early childhood with persistent microhematuria and can progress to proteinuria and kidney failure in adolescence or early adulthood if left untreated. On biopsy, pathognomonic features include alternate thinning, thickening and lamellation of the glomerular basement membrane (GBM), in the presence of podocyte foot process effacement. Although previous studies indicate a prevalence of AS of about 1/50,000, a recent publication reported a predicted rate of pathogenic COL4A5 variants of 1/2320. We herewith present 98 patients (40 M/58 F) from 26 Greek families. We are selectively presenting the families segregating the X-linked form of AS with pathogenic variants in the COL4A5 gene. We found 21 different pathogenic variants, 12 novel: eight glycine and one proline substitutions in the collagenous domain, one cysteine substitution in the NC1 domain, two premature termination of translation codons, three splicing variants, one 5-bp insertion/frameshift variant, one indel-frameshift variant and four gross deletions. Notably, patients in six families we describe here and three families we reported previously, carried the COL4A5-p.G624D substitution, a founder defect encountered all over Europe which is hypomorphic with mostly milder symptomatology. Importantly, on several occasions, the correct genetic diagnosis reclassified patients as patients with AS, leading to termination of previous immunosuppressive/cyclosporine A therapy and a switch to angiotensin converting enzyme inhibitors (ACEi). With the understanding that all 98 patients span a wide range of ages from infancy to late adulthood, 15 patients (11 M/4 F) reached kidney failure and 11 (10 M/1 F) received a transplant. The prospects of avoiding lengthy diagnostic investigations and erroneous medications, and the advantage of delaying kidney failure with very early administration of renin-angiotensin-aldosterone system (RAAS) blockade, highlights the importance of timely documentation of AS by genetic diagnosis.
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Hirabayashi Y, Katayama K, Mori M, Matsuo H, Fujimoto M, Joh K, Murata T, Ito M, Dohi K. Mutation Analysis of Thin Basement Membrane Nephropathy. Genes (Basel) 2022; 13:genes13101779. [PMID: 36292665 PMCID: PMC9602179 DOI: 10.3390/genes13101779] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 09/29/2022] [Accepted: 09/30/2022] [Indexed: 11/04/2022] Open
Abstract
Thin basement membrane nephropathy (TBMN) is characterized by the observation of microhematuria and a thin glomerular basement membrane on kidney biopsy specimens. Its main cause is heterozygous mutations of COL4A3 or COL4A4, which also cause late-onset focal segmental glomerulosclerosis (FSGS) or autosomal dominant Alport syndrome (ADAS). Thirteen TBMN cases were analyzed using Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), and exome sequencing. Ten heterozygous variants were detected in COL4A3 or COL4A4 in nine patients via Sanger sequencing, three of which were novel variants. The diagnostic rate of “likely pathogenic” or “pathogenic” under the American College of Medical Genetics and Genomics guidelines was 53.8% (7 out of 13 patients). There were eight single nucleotide variants, seven of which were glycine substitutions in the collagenous domain, one of which was a splice-site single nucleotide variant, and two of which were deletion variants. One patient had digenic variants in COL4A3 and COL4A4. While MLPA analyses showed negative results, exome sequencing identified three heterozygous variants in causative genes of FSGS in four patients with no apparent variants on Sanger sequencing. Since patients with heterozygous mutations of COL4A3 or COL4A4 showed a wide spectrum of disease from TBMN to ADAS, careful follow-up will be necessary for these patients.
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Affiliation(s)
- Yosuke Hirabayashi
- Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu 514-8507, Japan
| | - Kan Katayama
- Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu 514-8507, Japan
- Correspondence: ; Tel.: +81-59-231-5403; Fax: +81-59-231-5569
| | - Mutsuki Mori
- Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu 514-8507, Japan
| | - Hiroshi Matsuo
- Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu 514-8507, Japan
- Department of Kidney Center, Suzuka Kaisei Hospital, Suzuka 513-8505, Japan
| | - Mika Fujimoto
- Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu 514-8507, Japan
- Department of Internal Medicine, Takeuchi Hospital, Tsu 514-0057, Japan
| | - Kensuke Joh
- Department of Pathology, The Jikei University School of Medicine, Tokyo 105-0003, Japan
| | - Tomohiro Murata
- Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu 514-8507, Japan
| | - Masaaki Ito
- Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu 514-8507, Japan
| | - Kaoru Dohi
- Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu 514-8507, Japan
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Sambharia M, Rastogi P, Thomas CP. Monogenic focal segmental glomerulosclerosis: A conceptual framework for identification and management of a heterogeneous disease. AMERICAN JOURNAL OF MEDICAL GENETICS. PART C, SEMINARS IN MEDICAL GENETICS 2022; 190:377-398. [PMID: 35894442 PMCID: PMC9796580 DOI: 10.1002/ajmg.c.31990] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 05/31/2022] [Accepted: 06/30/2022] [Indexed: 01/29/2023]
Abstract
Focal segmental glomerulosclerosis (FSGS) is not a disease, rather a pattern of histological injury occurring from a variety of causes. The exact pathogenesis has yet to be fully elucidated but is likely varied based on the type of injury and the primary target of that injury. However, the approach to treatment is often based on the degree of podocyte foot process effacement and clinical presentation without sufficient attention paid to etiology. In this regard, there are many monogenic causes of FSGS with variable presentation from nephrotic syndrome with histological features of primary podocytopathy to more modest degrees of proteinuria with limited evidence of podocyte foot process injury. It is likely that genetic causes are largely underdiagnosed, as the role and the timing of genetic testing in FSGS is not established and genetic counseling, testing options, and interpretation of genotype in the context of phenotype may be outside the scope of practice for both nephrologists and geneticists. Yet most clinicians believe that a genetic diagnosis can lead to targeted therapy, limit the use of high-dose corticosteroids as a therapeutic trial, and allow the prediction of the natural history and risk for recurrence in the transplanted kidney. In this manuscript, we emphasize that genetic FSGS is not monolithic in its presentation, opine on the importance of genetic testing and provide an algorithmic approach to deployment of genetic testing in a timely fashion when faced with a patient with FSGS.
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Affiliation(s)
- Meenakshi Sambharia
- Division of Nephrology, Department of Internal MedicineUniversity of IowaIowa CityIowaUSA
| | - Prerna Rastogi
- Department of PathologyUniversity of IowaIowa CityIowaUSA
| | - Christie P. Thomas
- Division of Nephrology, Department of Internal MedicineUniversity of IowaIowa CityIowaUSA,Department of PediatricsUniversity of IowaIowa CityIowaUSA,The Iowa Institute of Human GeneticsUniversity of IowaIowa CityIowaUSA,Medical ServiceVeterans Affairs Medical CenterIowa CityIowaUSA
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Adeva-Andany MM, Carneiro-Freire N. Biochemical composition of the glomerular extracellular matrix in patients with diabetic kidney disease. World J Diabetes 2022; 13:498-520. [PMID: 36051430 PMCID: PMC9329837 DOI: 10.4239/wjd.v13.i7.498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/19/2022] [Accepted: 06/26/2022] [Indexed: 02/06/2023] Open
Abstract
In the glomeruli, mesangial cells produce mesangial matrix while podocytes wrap glomerular capillaries with cellular extensions named foot processes and tether the glomerular basement membrane (GBM). The turnover of the mature GBM and the ability of adult podocytes to repair injured GBM are unclear. The actin cytoskeleton is a major cytoplasmic component of podocyte foot processes and links the cell to the GBM. Predominant components of the normal glomerular extracellular matrix (ECM) include glycosaminoglycans, proteoglycans, laminins, fibronectin-1, and several types of collagen. In patients with diabetes, multiorgan composition of extracellular tissues is anomalous, including the kidney, so that the constitution and arrangement of glomerular ECM is profoundly altered. In patients with diabetic kidney disease (DKD), the global quantity of glomerular ECM is increased. The level of sulfated proteoglycans is reduced while hyaluronic acid is augmented, compared to control subjects. The concentration of mesangial fibronectin-1 varies depending on the stage of DKD. Mesangial type III collagen is abundant in patients with DKD, unlike normal kidneys. The amount of type V and type VI collagens is higher in DKD and increases with the progression of the disease. The GBM contains lower amount of type IV collagen in DKD compared to normal tissue. Further, genetic variants in the α3 chain of type IV collagen may modulate susceptibility to DKD and end-stage kidney disease. Human cellular models of glomerular cells, analyses of human glomerular proteome, and improved microscopy procedures have been developed to investigate the molecular composition and organization of the human glomerular ECM.
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Aypek H, Krisp C, Lu S, Liu S, Kylies D, Kretz O, Wu G, Moritz M, Amann K, Benz K, Tong P, Hu ZM, Alsulaiman SM, Khan AO, Grohmann M, Wagner T, Müller-Deile J, Schlüter H, Puelles VG, Bergmann C, Huber TB, Grahammer F. Loss of the collagen IV modifier prolyl 3-hydroxylase 2 causes thin basement membrane nephropathy. J Clin Invest 2022; 132:147253. [PMID: 35499085 PMCID: PMC9057608 DOI: 10.1172/jci147253] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 03/16/2022] [Indexed: 01/12/2023] Open
Abstract
The glomerular filtration barrier (GFB) produces primary urine and is composed of a fenestrated endothelium, a glomerular basement membrane (GBM), podocytes, and a slit diaphragm. Impairment of the GFB leads to albuminuria and microhematuria. The GBM is generated via secreted proteins from both endothelial cells and podocytes and is supposed to majorly contribute to filtration selectivity. While genetic mutations or variations of GBM components have been recently proposed to be a common cause of glomerular diseases, pathways modifying and stabilizing the GBM remain incompletely understood. Here, we identified prolyl 3-hydroxylase 2 (P3H2) as a regulator of the GBM in an a cohort of patients with albuminuria. P3H2 hydroxylates the 3' of prolines in collagen IV subchains in the endoplasmic reticulum. Characterization of a P3h2ΔPod mouse line revealed that the absence of P3H2 protein in podocytes induced a thin basement membrane nephropathy (TBMN) phenotype with a thinner GBM than that in WT mice and the development of microhematuria and microalbuminuria over time. Mechanistically, differential quantitative proteomics of the GBM identified a significant decrease in the abundance of collagen IV subchains and their interaction partners in P3h2ΔPod mice. To our knowledge, P3H2 protein is the first identified GBM modifier, and loss or mutation of P3H2 causes TBMN and focal segmental glomerulosclerosis in mice and humans.
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Affiliation(s)
| | - Christoph Krisp
- Institute of Clinical Chemistry and Laboratory Medicine, Mass Spectrometric Proteomics Group, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Shun Lu
- III. Department of Medicine and
| | | | | | | | | | - Manuela Moritz
- Institute of Clinical Chemistry and Laboratory Medicine, Mass Spectrometric Proteomics Group, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Kerstin Amann
- Department of Nephropathology, Institute of Pathology and
| | - Kerstin Benz
- Department of Pediatrics, University of Erlangen, Erlangen, Germany
| | - Ping Tong
- Department of Ophthalmology, The Second Xiangya Hospital and
| | - Zheng-mao Hu
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | | | - Arif O. Khan
- Eye Institute, Cleveland Clinic Abu Dhabi, Abu Dhabi, United Arab Emirates.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western University, Cleveland, Ohio, USA
| | - Maik Grohmann
- Medizinische Genetik Mainz, Limbach Genetics, Mainz, Germany
| | - Timo Wagner
- Medizinische Genetik Mainz, Limbach Genetics, Mainz, Germany
| | - Janina Müller-Deile
- Department of Nephrology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Hartmut Schlüter
- Institute of Clinical Chemistry and Laboratory Medicine, Mass Spectrometric Proteomics Group, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | - Carsten Bergmann
- Medizinische Genetik Mainz, Limbach Genetics, Mainz, Germany.,Department of Medicine IV, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
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Wopperer FJ, Knaup KX, Stanzick KJ, Schneider K, Jobst-Schwan T, Ekici AB, Uebe S, Wenzel A, Schliep S, Schürfeld C, Seitz R, Bernhardt W, Gödel M, Wiesener A, Popp B, Stark KJ, Gröne HJ, Friedrich B, Weiß M, Basic-Jukic N, Schiffer M, Schröppel B, Huettel B, Beck BB, Sayer JA, Ziegler C, Büttner-Herold M, Amann K, Heid IM, Reis A, Pasutto F, Wiesener MS. Diverse molecular causes of unsolved autosomal dominant tubulointerstitial kidney diseases. Kidney Int 2022; 102:405-420. [DOI: 10.1016/j.kint.2022.04.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 03/22/2022] [Accepted: 04/08/2022] [Indexed: 12/11/2022]
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Devarajan P, Chertow GM, Susztak K, Levin A, Agarwal R, Stenvinkel P, Chapman AB, Warady BA. Emerging Role of Clinical Genetics in CKD. Kidney Med 2022; 4:100435. [PMID: 35372818 PMCID: PMC8971313 DOI: 10.1016/j.xkme.2022.100435] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Chronic kidney disease (CKD) afflicts 15% of adults in the United States, of whom 25% have a family history. Genetic testing is supportive in identifying and possibly confirming diagnoses of CKD, thereby guiding care. Advances in the clinical genetic evaluation include next-generation sequencing with targeted gene panels, whole exome sequencing, and whole genome sequencing. These platforms provide DNA sequence reads with excellent coverage throughout the genome and have identified novel genetic causes of CKD. New pathologic genetic variants identified in previously unrecognized biological pathways have elucidated disease mechanisms underlying CKD etiologies, potentially establishing prognosis and guiding treatment selection. Molecular diagnoses using genetic sequencing can detect rare, potentially treatable mutations, avoid misdiagnoses, guide selection of optimal therapy, and decrease the risk of unnecessary and potentially harmful interventions. Genetic testing has been widely adopted in pediatric nephrology; however, it is less frequently used to date in adult nephrology. Extension of clinical genetic approaches to adult patients may achieve similar benefits in diagnostic refinement and treatment selection. This review aimed to identify clinical CKD phenotypes that may benefit the most from genetic testing, outline the commonly available platforms, and provide examples of successful deployment of these approaches in CKD.
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12
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Altun I, Saygılı S, Canpolat N, Özlük Y, Hürdoğan Ö, Yeşil G, Çalışkan S, Sever L. Strong mesangial IgA staining-does it always refer to IgA nephropathy in a patient with proteinuria and hematuria? Answers. Pediatr Nephrol 2021; 36:2043-2045. [PMID: 33459929 DOI: 10.1007/s00467-020-04899-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 12/01/2020] [Indexed: 01/28/2023]
Affiliation(s)
- Ilayda Altun
- Department of Pediatrics, Cerrahpasa Faculty of Medicine, Istanbul University-Cerrahpasa, Istanbul, Turkey
| | - Seha Saygılı
- Department of Pediatric Nephrology, Cerrahpasa Faculty of Medicine, Istanbul University-Cerrahpasa, Istanbul, Turkey.
| | - Nur Canpolat
- Department of Pediatric Nephrology, Cerrahpasa Faculty of Medicine, Istanbul University-Cerrahpasa, Istanbul, Turkey
| | - Yasemin Özlük
- Department of Pathology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Özge Hürdoğan
- Department of Pathology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Gözde Yeşil
- Department of Medical Genetics, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Salim Çalışkan
- Department of Pediatric Nephrology, Cerrahpasa Faculty of Medicine, Istanbul University-Cerrahpasa, Istanbul, Turkey
| | - Lale Sever
- Department of Pediatric Nephrology, Cerrahpasa Faculty of Medicine, Istanbul University-Cerrahpasa, Istanbul, Turkey
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13
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Shulman C, Liang E, Kamura M, Udwan K, Yao T, Cattran D, Reich H, Hladunewich M, Pei Y, Savige J, Paterson AD, Suico MA, Kai H, Barua M. Type IV Collagen Variants in CKD: Performance of Computational Predictions for Identifying Pathogenic Variants. Kidney Med 2021; 3:257-266. [PMID: 33851121 PMCID: PMC8039416 DOI: 10.1016/j.xkme.2020.12.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Rationale & Objective Pathogenic variants in type IV collagen have been reported to account for a significant proportion of chronic kidney disease. Accordingly, genetic testing is increasingly used to diagnose kidney diseases, but testing also may reveal rare missense variants that are of uncertain clinical significance. To aid in interpretation, computational prediction (called in silico) programs may be used to predict whether a variant is clinically important. We evaluate the performance of in silico programs for COL4A3/A4/A5 variants. Study Design, Setting, & Participants Rare missense variants in COL4A3/A4/A5 were identified in disease cohorts, including a local focal segmental glomerulosclerosis (FSGS) cohort and publicly available disease databases, in which they are categorized as pathogenic or benign based on clinical criteria. Tests Compared & Outcomes All rare missense variants identified in the 4 disease cohorts were subjected to in silico predictions using 12 different programs. Comparisons between the predictions were compared with: (1) variant classification (pathogenic or benign) in the cohorts and (2) functional characterization in a randomly selected smaller number (17) of pathogenic or uncertain significance variants obtained from the local FSGS cohort. Results In silico predictions correctly classified 75% to 97% of pathogenic and 57% to 100% of benign COL4A3/A4/A5 variants in public disease databases. The congruency of in silico predictions was similar for variants categorized as pathogenic and benign, with the exception of benign COL4A5 variants, in which disease effects were overestimated. By contrast, in silico predictions and functional characterization classified all 9 pathogenic COL4A3/A4/A5 variants correctly that were obtained from a local FSGS cohort. However, these programs also overestimated the effects of genomic variants of uncertain significance when compared with functional characterization. Each of the 12 in silico programs used yielded similar results. Limitations Overestimation of in silico program sensitivity given that they may have been used in the categorization of variants labeled as pathogenic in disease repositories. Conclusions Our results suggest that in silico predictions are sensitive but not specific to assign COL4A3/A4/A5 variant pathogenicity, with misclassification of benign variants and variants of uncertain significance. Thus, we do not recommend in silico programs but instead recommend pursuing more objective levels of evidence suggested by medical genetics guidelines.
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Affiliation(s)
- Cole Shulman
- Division of Nephrology, University Health Network, Toronto, Canada.,Toronto General Hospital Research Institute, Toronto General Hospital, Toronto, Canada
| | - Emerald Liang
- Division of Nephrology, University Health Network, Toronto, Canada.,Toronto General Hospital Research Institute, Toronto General Hospital, Toronto, Canada
| | - Misato Kamura
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, Kumamoto, Japan
| | - Khalil Udwan
- Division of Nephrology, University Health Network, Toronto, Canada.,Toronto General Hospital Research Institute, Toronto General Hospital, Toronto, Canada
| | - Tony Yao
- Division of Nephrology, University Health Network, Toronto, Canada.,Toronto General Hospital Research Institute, Toronto General Hospital, Toronto, Canada
| | - Daniel Cattran
- Division of Nephrology, University Health Network, Toronto, Canada.,Toronto General Hospital Research Institute, Toronto General Hospital, Toronto, Canada.,Institute of Medical Sciences, Toronto, Canada.,Department of Medicine, Toronto, Canada
| | - Heather Reich
- Division of Nephrology, University Health Network, Toronto, Canada.,Toronto General Hospital Research Institute, Toronto General Hospital, Toronto, Canada.,Institute of Medical Sciences, Toronto, Canada.,Department of Medicine, Toronto, Canada
| | - Michelle Hladunewich
- Division of Nephrology, University Health Network, Toronto, Canada.,Toronto General Hospital Research Institute, Toronto General Hospital, Toronto, Canada.,Institute of Medical Sciences, Toronto, Canada.,Department of Medicine, Toronto, Canada
| | - York Pei
- Division of Nephrology, University Health Network, Toronto, Canada.,Toronto General Hospital Research Institute, Toronto General Hospital, Toronto, Canada.,Institute of Medical Sciences, Toronto, Canada.,Department of Medicine, Toronto, Canada
| | - Judy Savige
- University of Melbourne, Melbourne, Australia
| | - Andrew D Paterson
- Division of Epidemiology and Biostatistics, Dalla Lana School of Public Health, Toronto, Canada.,Genetics and Genome Biology, Research Institute at Hospital for Sick Children, Toronto, Canada
| | - Mary Ann Suico
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, Kumamoto, Japan
| | - Hirofumi Kai
- Department of Molecular Medicine, Graduate School of Pharmaceutical Science, Kumamoto University, Kumamoto, Japan
| | - Moumita Barua
- Division of Nephrology, University Health Network, Toronto, Canada.,Toronto General Hospital Research Institute, Toronto General Hospital, Toronto, Canada.,Institute of Medical Sciences, Toronto, Canada.,Department of Medicine, Toronto, Canada
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14
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Matthaiou A, Poulli T, Deltas C. Prevalence of clinical, pathological and molecular features of glomerular basement membrane nephropathy caused by COL4A3 or COL4A4 mutations: a systematic review. Clin Kidney J 2020; 13:1025-1036. [PMID: 33391746 PMCID: PMC7769542 DOI: 10.1093/ckj/sfz176] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 11/06/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Patients heterozygous for COL4A3 or COL4A4 mutations show a wide spectrum of disease, extending from familial isolated microscopic haematuria, as a result of thin basement membranes (TBMs), to autosomal dominant Alport syndrome (ADAS) and end-stage renal disease (ESRD). Many patients are mentioned in the literature under the descriptive diagnosis of TBM nephropathy (TBMN), in which case it actually describes a histological finding that represents the carriers of autosomal recessive Alport syndrome (ARAS), a severe glomerulopathy, as most patients reach ESRD at a mean age of 25 years. METHODS We performed a systematic literature review for patients with heterozygous COL4A3/A4 mutations with the aim of recording the spectrum and frequency of pathological features. We searched three databases (PubMed, Embase and Scopus) using the keywords 'Autosomal Dominant Alport Syndrome' OR 'Thin Basement Membrane Disease' OR 'Thin Basement Membrane Nephropathy'. We identified 48 publications reporting on 777 patients from 258 families. RESULTS In total, 29% of the patients developed chronic kidney disease (CKD) and 15.1% reached ESRD at a mean age of 52.8 years. Extrarenal features and typical Alport syndrome (AS) findings had a low prevalence in patients as follows: hearing loss, 16%; ocular lesions, 3%; basement membrane thickening, 18.4%; and podocyte foot process effacement, 6.9%. Data for 76 patients from 54 families emphasize extensive inter- and intrafamilial heterogeneity, with age at onset of ESRD ranging between 21 and 84 years (mean 52.8). CONCLUSIONS The analysis enabled a comparison of the clinical course of patients with typical ARAS or X-linked AS with those with heterozygous COL4A mutations diagnosed with TBMN or ADAS. Despite the consequence of a potential ascertainment bias, an important outcome is that TBM poses a global high risk of developing severe CKD, over a long follow-up, with a variable spectrum of other findings. The results are useful to practicing nephrologists for better evaluation of patients.
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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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15
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Demir E, Caliskan Y. Variations of type IV collagen-encoding genes in patients with histological diagnosis of focal segmental glomerulosclerosis. Pediatr Nephrol 2020; 35:927-936. [PMID: 31254113 DOI: 10.1007/s00467-019-04282-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 05/01/2019] [Accepted: 05/31/2019] [Indexed: 01/07/2023]
Abstract
Focal segmental glomerulosclerosis (FSGS), an important cause of end-stage kidney disease (ESKD), covers a spectrum of clinicopathological syndromes sharing a common glomerular lesion, based on an injury of podocytes caused by diverse insults to glomeruli. Although it is well expressed in many reports that the term FSGS is not useful and applicable to a single disease, particularly in genetic studies, FSGS continues to be used as a single clinical diagnosis. Distinguishing genetic forms of FSGS is important for the treatment and overall prognosis because secondary forms of FSGS, produced by rare pathogenic variations in podocyte genes, are not good candidates for immunosuppressive treatment. Over the past decade, several next generation sequencing (NGS) methods have been used to investigate the patients with steroid resistance nephrotic syndrome (SRNS) or FSGS. Pathogenic variants in COL4A3, COL4A4, or COL4A5 genes have been frequently identified in patients with histologic diagnosis of FSGS. The contribution of these mostly heterozygous genetic variations in FSGS pathogenesis and the clinical course of patients with these variations have not been well characterized. This review emphasizes the importance of appropriate approach in selection and diagnosis of cases and interpretation of the genetic data in these studies and suggests a detailed review of existing clinical variant databases using newly available population genetic data.
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Affiliation(s)
- Erol Demir
- Division of Nephrology, Department of Internal Medicine, Istanbul School of Medicine, Istanbul University, Capa, Fatih, 34093, Istanbul, Turkey
| | - Yasar Caliskan
- Division of Nephrology, Department of Internal Medicine, Istanbul School of Medicine, Istanbul University, Capa, Fatih, 34093, Istanbul, Turkey.
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16
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How to resolve confusion in the clinical setting for the diagnosis of heterozygous COL4A3 or COL4A4 gene variants? Discussion and suggestions from nephrologists. Clin Exp Nephrol 2020; 24:651-656. [PMID: 32232700 PMCID: PMC7371658 DOI: 10.1007/s10157-020-01880-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 03/17/2020] [Indexed: 12/22/2022]
Abstract
Both thin basement membrane nephropathy (TBMN) and autosomal dominant Alport syndrome (ADAS) are types of hereditary nephritis resulting from heterozygous mutations in COL4A3 or COL4A4 genes. Although TBMN is characterized by hematuria and thinning of the glomerular basement membrane (GBM) with excellent renal prognosis, some patients develop end-stage renal disease (ESRD) later in life. In contrast, although AS is characterized by progressive nephropathy with lamellation of the GBM, there are some patients diagnosed with ADAS from a family history of ESRD but who only suffer from hematuria with GBM thinning. These findings indicate a limitation in distinction between TBMN and ADAS. Diagnosis of AS is significant because it facilitates careful follow-up and early treatment, whereas diagnosis of TBMN can underestimate the risk of ESRD. However, some experts are against using the term ADAS as the phenotypes of heterozygous variants vary from no urinary abnormality to ESRD, even between family members with the same mutations, indicating that unknown secondary factors may play a large role in the disease severity. These diagnostic difficulties result in significant confusion in clinical settings. Moreover, recent studies revealed that the number of patients with chronic kidney disease caused by these gene mutations is far higher than previously thought. The aim of this article is to review differing opinions regarding the diagnosis of heterozygous COL4A3 or COL4A4 variants, and to highlight the importance for nephrologists to recognize this disease, and the importance of the need to reclassify this disease to minimize the current confusion.
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17
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Rheault MN, Savige J, Randles MJ, Weinstock A, Stepney M, Turner AN, Parziale G, Gross O, Flinter FA, Miner JH, Lagas S, Gear S, Lennon R. The importance of clinician, patient and researcher collaborations in Alport syndrome. Pediatr Nephrol 2020; 35:733-742. [PMID: 31044288 PMCID: PMC7096363 DOI: 10.1007/s00467-019-04241-7] [Citation(s) in RCA: 11] [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: 02/24/2019] [Accepted: 03/15/2019] [Indexed: 12/19/2022]
Abstract
Alport syndrome is caused by mutations in the genes COL4A3, COL4A4 or COL4A5 and is characterised by progressive glomerular disease, sensorineural hearing loss and ocular defects. Occurring in less than 1:5000, Alport syndrome is a rare genetic disorder but still accounts for > 1% of the prevalent population receiving renal replacement therapy. There is also increasing awareness about the risk of chronic kidney disease in individuals with heterozygous mutations in Alport syndrome genes. The mainstay of current therapy is the use of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, yet potential new therapies are now entering clinical trials. The 2017 International Workshop on Alport Syndrome in Glasgow was a pre-conference workshop ahead of the 50th anniversary meeting of the European Society for Pediatric Nephrology. It focussed on updates in clinical practice, genetics and basic science and also incorporated patient perspectives. More than 80 international experts including clinicians, geneticists, researchers from academia and industry, and patient representatives took part in panel discussions and breakout groups. This report summarises the workshop proceedings and the relevant contemporary literature. It highlights the unique clinician, patient and researcher collaborations achieved by regular engagement between the groups.
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Affiliation(s)
- Michelle N. Rheault
- Department of Pediatrics, University of Minnesota Masonic Children’s Hospital, Minneapolis, MN USA
| | - Judith Savige
- Department of Medicine, Royal Melbourne Hospital, Victoria, Australia
| | - Michael J. Randles
- Wellcome Centre for Cell-Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, UK
| | | | - Melissa Stepney
- Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK
| | - A Neil Turner
- Renal Medicine, Royal Infirmary, University of Edinburgh, Edinburgh, UK
| | | | - Oliver Gross
- Clinic of Nephrology and Rheumatology, University Medicine Goettingen, Goettingen, Germany
| | - Frances A Flinter
- Department of Clinical Genetics, Guy’s & St Thomas’ NHS Foundation Trust, London, UK
| | - Jeffrey H Miner
- Division of Nephrology, Washington University School of Medicine, St Louis, MO USA
| | | | | | - Rachel Lennon
- Wellcome Centre for Cell-Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, UK. .,Department of Paediatric Nephrology, Royal Manchester Children's Hospital, Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK.
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18
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Davis J, Tjipto A, Hegerty K, Mallett A. The use of electron microscopy in the diagnosis of focal segmental glomerulosclerosis: are current pathological techniques missing important abnormalities in the glomerular basement membrane? F1000Res 2019; 8:1204. [PMID: 31781368 PMCID: PMC6854873 DOI: 10.12688/f1000research.19997.2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/04/2019] [Indexed: 01/15/2023] Open
Abstract
Background: There is an increasing appreciation that variants of the
COL4A genes may be associated with the development of focal segmental glomerulosclerosis (FSGS). On electron microscopy, such variants may produce characteristic changes within the glomerular basement membrane (GBM). These changes may be missed if glomerular lesions histologically diagnosed as FSGS on light microscopy are not subjected to electron microscopy. Methods: We conducted a retrospective cohort analysis of all patients presenting to two hospitals who received a primary histological diagnosis of FSGS to see if these samples underwent subsequent electron microscopy. Each such sample was also scrutinised for the presence of characteristic changes of an underlying type IV collagen disorder Results: A total of 43 patients were identified. Of these, only 30 underwent electron microscopy. In two samples there were histological changes detected that might have suggested the underlying presence of a type IV collagen disorder. Around one in three biopsy samples that had a histological diagnosis of FSGS were not subjected to electron microscopy. Conclusion: Renal biopsy samples that have a histological diagnosis of primary FSGS not subjected to subsequent electron microscopy may potentially miss ultrastructural changes in the GBM that could signify an underlying type IV collagen disorder as the patient’s underlying disease process. This could potentially affect both them and their families’ investigative and management decisions given potential for implications for transplant, heritability and different disease pathogenesis. This represents a gap in care which should be reflected upon and rectified via iterative standard care and unit-level quality assurance initiatives.
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Affiliation(s)
- Justin Davis
- Department of Nephrology, Barwon Health, Geelong, Victoria, 3220, Australia
| | - Alwie Tjipto
- Department of Nephrology, Barwon Health, Geelong, Victoria, 3220, Australia
| | - Katharine Hegerty
- Department of Nephrology, Royal Brisbane and Women's Hospital, Herston, Queensland, Australia
| | - Andrew Mallett
- Department of Nephrology, Royal Brisbane and Women's Hospital, Herston, Queensland, Australia
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19
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Guaragna MS, de Brito Lutaif ACG, de Souza ML, Maciel-Guerra AT, Belangero VMS, Guerra-Júnior G, de Mello MP. Promises and pitfalls of whole-exome sequencing exemplified by a nephrotic syndrome family. Mol Genet Genomics 2019; 295:135-142. [PMID: 31520189 DOI: 10.1007/s00438-019-01609-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 09/05/2019] [Indexed: 01/12/2023]
Abstract
High-throughput techniques such as whole-exome sequencing (WES) show promise for the identification of candidate genes that underlie Mendelian diseases such as nephrotic syndrome (NS). These techniques have enabled the identification of a proportion of the approximately 54 genes associated with NS. However, the main pitfall of using WES in clinical and research practice is the identification of multiple variants, which hampers interpretation during downstream analysis. One useful strategy is to evaluate the co-inheritance of rare variants in affected family members. Here, we performed WES of a patient with steroid-resistant NS (SRNS) and intermittent microhematuria. Currently, 15 years after kidney transplantation, this patient presents normal kidney function. The patient was found to be homozygous for a rare MYO1E stop-gain variant, and was heterozygous for rare variants in NS-associated genes, COL4A4, KANK1, LAMB2, ANLN, E2F3, and APOL1. We evaluated the presence or absence of these variants in both parents and 11 siblings, three of whom exhibited a milder phenotype of the kidney disease. Analysis of variant segregation in the family, indicated the MYO1E stop-gain variant as the putative causal variant underlying the kidney disease in the patient and two of her affected sisters. Two secondary variants in COL4A4-identified in some other affected family members-require further functional studies to determine whether they play a role in the development of microhematuria in affected family members. Our data illustrate the difficulties in distinguishing the causal pathogenic variants from incidental findings after WES-based variant analysis, especially in heterogenous genetic conditions, such as NS.
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Affiliation(s)
- Mara Sanches Guaragna
- Laboratory of Human Molecular Genetics, Center for Molecular Biology and Genetic Engineering (CBMEG), State University of Campinas, UNICAMP, Caixa Postal 6010, 13083-875, Campinas, SP, Brazil.
| | - Anna Cristina Gervásio de Brito Lutaif
- Integrated Center of Pediatric Nephrology (CIN), Department of Pediatrics, School of Medical Sciences (FCM), State University of Campinas, UNICAMP, Campinas, Brazil
| | - Marcela Lopes de Souza
- Laboratory of Human Molecular Genetics, Center for Molecular Biology and Genetic Engineering (CBMEG), State University of Campinas, UNICAMP, Caixa Postal 6010, 13083-875, Campinas, SP, Brazil
| | | | - Vera Maria Santoro Belangero
- Integrated Center of Pediatric Nephrology (CIN), Department of Pediatrics, School of Medical Sciences (FCM), State University of Campinas, UNICAMP, Campinas, Brazil.,Department of Pediatrics, School of Medical Sciences (FCM), UNICAMP, Campinas, SP, Brazil
| | - Gil Guerra-Júnior
- Department of Pediatrics, School of Medical Sciences (FCM), UNICAMP, Campinas, SP, Brazil.,Growth and Development Laboratory, Center for Investigation in Pediatrics (CIPED), School of Medical Sciences (FCM), UNICAMP, Campinas, SP, Brazil
| | - Maricilda Palandi de Mello
- Laboratory of Human Molecular Genetics, Center for Molecular Biology and Genetic Engineering (CBMEG), State University of Campinas, UNICAMP, Caixa Postal 6010, 13083-875, Campinas, SP, Brazil
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20
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Gribouval O, Boyer O, Hummel A, Dantal J, Martinez F, Sberro-Soussan R, Etienne I, Chauveau D, Delahousse M, Lionet A, Allard J, Pouteil Noble C, Tête MJ, Heidet L, Antignac C, Servais A. Identification of genetic causes for sporadic steroid-resistant nephrotic syndrome in adults. Kidney Int 2019; 94:1013-1022. [PMID: 30348286 DOI: 10.1016/j.kint.2018.07.024] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 06/18/2018] [Accepted: 07/12/2018] [Indexed: 01/15/2023]
Abstract
Monogenic forms of Steroid-Resistant Nephrotic Syndrome (SRNS) have been widely characterized, but genetic screening paradigms preferentially address congenital, infantile onset, and familial cases. Our aim was to characterize the distribution of disease-causing gene mutations in adults with sporadic SRNS or focal segmental glomerulosclerosis (FSGS). We selected adult patients with non-syndromic, biopsy-proven FSGS or SRNS in the absence of known family history. Strict clinical criteria included lack of response to glucocorticoids and cyclosporine, and no recurrence after kidney transplantation. Mutations in SRNS genes were detected using a targeted gene panel. Sixteen of 135 tested participants (11.8%) carried pathogenic mutations in monogenic SRNS genes, and 14 others (10.4%) carried two APOL1 high-risk alleles. Autosomal recessive disease was diagnosed in 5 participants, autosomal dominant disease in 9, and X-linked disease in 2. Four participants carried a de novo heterozygous mutation. Among the 16 participants with identified mutations in monogenic SNRS genes, 7 (43.7%) had type IV collagen mutations. Mutations in monogenic SNRS genes were identified primarily in participants with proteinuria onset before 25 years of age, while the age at disease onset was variable in those with APOL1 high-risk genotype. Mean age at diagnosis was lower and renal survival was worse in participants with identified mutations in SNRS genes than in those without mutations. We found a significant rate of pathogenic mutations in adults with SRNS, with Type IV collagen mutations being the most frequent. These findings may have immediate impact on clinical practice.
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Affiliation(s)
- Olivier Gribouval
- Inserm U1163, Imagine Institute, Paris Descartes University, Paris, France
| | - Olivia Boyer
- Inserm U1163, Imagine Institute, Paris Descartes University, Paris, France; Pediatric Nephrology, Centre de référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte, Necker Hospital, Paris, France
| | - Aurélie Hummel
- Inserm U1163, Imagine Institute, Paris Descartes University, Paris, France; Adult Nephrology & Transplantation, Centre de référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte, Necker Hospital, Paris, France
| | | | - Frank Martinez
- Adult Nephrology & Transplantation, Centre de référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte, Necker Hospital, Paris, France
| | - Rebecca Sberro-Soussan
- Adult Nephrology & Transplantation, Centre de référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte, Necker Hospital, Paris, France
| | - Isabelle Etienne
- Nephrology Department, Hôpital de Bois-Guillaume, CHU Rouen, Rouen, France
| | - Dominique Chauveau
- Department of Nephrology and Organ Transplantation, CHU Rangueil, Toulouse, France
| | | | - Arnaud Lionet
- Nephrology Department, Hôpital Huriez, CHU Lille, Lille, France
| | | | - Claire Pouteil Noble
- Nephrology-Transplantation Department, Hôpital Edouard Herriot, Lyon I University, Lyon, France
| | - Marie-Josèphe Tête
- Inserm U1163, Imagine Institute, Paris Descartes University, Paris, France
| | - Laurence Heidet
- Inserm U1163, Imagine Institute, Paris Descartes University, Paris, France; Pediatric Nephrology, Centre de référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte, Necker Hospital, Paris, France; Genetic Department, Necker Hospital, APHP, Paris, France
| | - Corinne Antignac
- Inserm U1163, Imagine Institute, Paris Descartes University, Paris, France; Genetic Department, Necker Hospital, APHP, Paris, France.
| | - Aude Servais
- Inserm U1163, Imagine Institute, Paris Descartes University, Paris, France; Adult Nephrology & Transplantation, Centre de référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte, Necker Hospital, Paris, France.
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21
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Imafuku A, Nozu K, Sawa N, Hasegawa E, Hiramatsu R, Kawada M, Hoshino J, Tanaka K, Ishii Y, Takaichi K, Fujii T, Ohashi K, Iijima K, Ubara Y. Autosomal dominant form of type IV collagen nephropathy exists among patients with hereditary nephritis difficult to diagnose clinicopathologically. Nephrology (Carlton) 2019; 23:940-947. [PMID: 28704582 PMCID: PMC6767408 DOI: 10.1111/nep.13115] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2017] [Indexed: 01/01/2023]
Abstract
The study revealed that 69% of families with hereditary nephritis that was difficult to diagnose clinicopathologically had heterozygous mutations of COL4A3/A4 (TBMN/ADAS). The finding suggests the importance of genetic testing in appropriate patients. Aim Type IV collagen nephropathies include Alport Syndrome and thin basement membrane nephropathy (TBMN), which are caused by mutations in COL4A3/A4/A5 genes. Recently, reports of patients with heterozygous mutations in COL4A3/A4 have been increasing. The clinical course of these patients has a wide variety, and they are diagnosed as TBMN, autosomal dominant Alport syndrome (ADAS), or familial focal segmental glomerular sclerosis. However, diagnosis, frequency and clinicopathological manifestation of them remains unclear. We tested COL4A3/A4/A5 genes in patients with hereditary nephritis that was difficult to diagnose clinicopathologically, and investigated who should undergo such testing. Methods We performed immunostaining for α5 chain of type IV collagen [α5 (IV)] in 27 patients from 21 families who fitted the following criteria: (i) haematuria and proteinuria (± renal dysfunction); (ii) family history of haematuria, proteinuria, and/or renal dysfunction (autosomal dominant inheritance); (iii) no specific glomerulonephritis; and (iv) thinning, splitting, or lamellation of the glomerular basement membrane (GBM) on electron microscopy. Then we performed genetic testing in 19 patients from 16 families who showed normal α5 (IV) patterns. We conducted a retrospective analysis of their clinicopathological findings. Results Among 16 families, 69% were detected heterozygous mutations in COL4A3/A4, suggesting the diagnosis of TBMN/ADAS. Twenty‐one percent of patients developed end stage renal disease. All patients showed thinning of GBM, which was accompanied by splitting or lamellation in seven patients. Conclusion A considerable fraction of patients with hereditary nephritis that is difficult to diagnose clinicopathologically have TBMN/ADAS. It is important to recognize TBMN/ADAS and perform genetic testing in appropriate patients.
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Affiliation(s)
- Aya Imafuku
- Nephrology Center, Toranomon Hospital, Minato-ku, Japan
| | - Kandai Nozu
- Department of Pediatrics, Kobe University, Kobe, Japan
| | - Naoki Sawa
- Nephrology Center, Toranomon Hospital, Minato-ku, Japan
| | - Eiko Hasegawa
- Nephrology Center, Toranomon Hospital, Minato-ku, Japan
| | | | | | | | - Kiho Tanaka
- Nephrology Center, Toranomon Hospital, Minato-ku, Japan
| | - Yasuo Ishii
- Nephrology Center, Toranomon Hospital, Minato-ku, Japan
| | - Kenmei Takaichi
- Nephrology Center, Toranomon Hospital, Minato-ku, Japan.,Okinaka Memorial Institute for Medical Research, Toranomon Hospital, Minato-ku, Japan
| | - Takeshi Fujii
- Department of Pathology, Toranomon Hospital, Minato-ku, Japan
| | - Kenichi Ohashi
- Department of Pathology, Toranomon Hospital, Minato-ku, Japan.,Department of Pathology, Yokohama City University, Graduate School of Medicine, Yokohama-shi, Japan
| | | | - Yoshifumi Ubara
- Nephrology Center, Toranomon Hospital, Minato-ku, Japan.,Okinaka Memorial Institute for Medical Research, Toranomon Hospital, Minato-ku, Japan
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22
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Features of Autosomal Recessive Alport Syndrome: A Systematic Review. J Clin Med 2019; 8:jcm8020178. [PMID: 30717457 PMCID: PMC6406612 DOI: 10.3390/jcm8020178] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Revised: 01/27/2019] [Accepted: 01/31/2019] [Indexed: 01/16/2023] Open
Abstract
Alport syndrome (AS) is one of the most frequent hereditary nephritis leading to end-stage renal disease (ESRD). Although X-linked (XLAS) inheritance is the most common form, cases with autosomal recessive inheritance with mutations in COL4A3 or COL4A4 are being increasingly recognized. A systematic review was conducted on autosomal recessive Alport syndrome (ARAS). Electronic databases were searched using related terms (until Oct 10th, 2018). From 1601 articles searched, there were 26 eligible studies with 148 patients. Female and male patients were equally affected. About 62% of patients had ESRD, 64% had sensorineural hearing loss (SNHL) and 17% had ocular manifestation. The median at onset was 2.5 years for hematuria (HU), 21 years for ESRD, and 13 years for SNHL. Patients without missense mutations had more severe outcomes at earlier ages, while those who had one or two missense mutations had delayed onset and lower prevalence of extrarenal manifestations. Of 49 patients with kidney biopsy available for electron microscopy (EM) pathology, 42 (86%) had typical glomerular basement membrane (GBM) changes, while 5 (10%) patients showed GBM thinning only. SNHL developed earlier than previously reported. There was a genotype phenotype correlation according to the number of missense mutations. Patients with missense mutations had delayed onset of hematuria, ESRD, and SNHL and lower prevalence of extrarenal manifestations.
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23
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Advances in molecular diagnosis and therapeutics in nephrotic syndrome and focal and segmental glomerulosclerosis. Curr Opin Nephrol Hypertens 2019; 27:194-200. [PMID: 29465426 DOI: 10.1097/mnh.0000000000000408] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
PURPOSE OF REVIEW The widespread adoption of next-generation sequencing by research and clinical laboratories has begun to uncover the previously unknown genetic basis of many diseases. In nephrology, one of the best examples of this is seen in focal and segmental glomerulosclerosis (FSGS) and nephrotic syndrome. We review advances made in 2017 as a result of human and molecular genetic studies as it relates to FSGS and nephrotic syndrome. RECENT FINDINGS There are more than 50 monogenic genes described in steroid-resistant nephrotic syndrome and FSGS, with seven reported in 2017. In individuals presenting with FSGS or nephrotic syndrome before or at the age of 18 years, the commonest genes in which a mutation is found continues to be limited to only a few including NPHS1 and NPHS2 based on multiple studies. For FSGS or nephrotic syndrome that presents after 18 years, mutations in COl4A3/4/5, traditionally associated with Alport syndrome, are increasingly being reported. Despite the extensive genetic heterogeneity in FSGS, there is evidence that some of these genes converge onto common pathways. There are also reports of in-vivo models exploring apolipoprotein 1 biology, variants in which account for part of the increased risk of nondiabetic kidney disease in African-Americans. Finally, genetic testing has several clinical uses including clarification of diagnosis and treatment; identification of suitable young biologic relatives for kidney donation; and preimplantation genetic diagnosis. CRISPR gene editing is currently an experimental tool only, but the recent reports of excising mutations in embryos could be a therapeutic option for individuals with any monogenic disorder in the future. SUMMARY Sequencing efforts are bringing novel variants into investigation and directing the efforts to understand how these lead to disease phenotypes. Expanding our understanding of the genetic basis of health and disease processes is the necessary first step to elaborate the repertoire of therapeutic agents available for patients with FSGS and nephrotic syndrome.
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Savige J. Should We Diagnose Autosomal Dominant Alport Syndrome When There Is a Pathogenic Heterozygous COL4A3 or COL4A4 Variant? Kidney Int Rep 2018; 3:1239-1241. [PMID: 30450445 PMCID: PMC6224634 DOI: 10.1016/j.ekir.2018.08.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Affiliation(s)
- Judy Savige
- Department of Medicine (Melbourne Health) and Northern Health, The University of Melbourne, Parkville, Victoria, Australia
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25
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Voskarides K, Papagregoriou G, Hadjipanagi D, Petrou I, Savva I, Elia A, Athanasiou Y, Pastelli A, Kkolou M, Hadjigavriel M, Stavrou C, Pierides A, Deltas C. COL4A5 and LAMA5 variants co-inherited in familial hematuria: digenic inheritance or genetic modifier effect? BMC Nephrol 2018; 19:114. [PMID: 29764427 PMCID: PMC5954460 DOI: 10.1186/s12882-018-0906-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 10/25/2017] [Accepted: 01/21/2018] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND About 40-50% of patients with familial microscopic hematuria (FMH) caused by thin basement membrane nephropathy (TBMN) inherit heterozygous mutations in collagen IV genes (COL4A3, COL4A4). On long follow-up, the full phenotypic spectrum of these patients varies a lot, ranging from isolated MH or MH plus low-grade proteinuria to chronic renal failure of variable degree, including end-stage renal disease (ESRD). METHODS Here, we performed Whole Exome Sequencing (WES) in patients of six families, presenting with autosomal dominant FMH, with or without progression to proteinuria and loss of renal function, all previously found negative for severe collagen IV mutations. Hierarchical filtering of the WES data was performed, followed by mutation prediction analysis, Sanger sequencing and genetic segregation analysis. RESULTS In one family with four patients, we found evidence for the contribution of two co-inherited variants in two crucial genes expressed in the glomerular basement membrane (GBM); LAMA5-p.Pro1243Leu and COL4A5-p.Asp654Tyr. Mutations in COL4A5 cause classical X-linked Alport Syndrome, while rare mutations in the LAMA5 have been reported in patients with focal segmental glomerulosclerosis. The phenotypic spectrum of the patients includes hematuria, proteinuria, focal segmental glomerulosclerosis, loss of kidney function and renal cortical cysts. CONCLUSIONS A modifier role of LAMA5 on the background of a hypomorphic Alport syndrome causing mutation is a possible explanation of our findings. Digenic inheritance is another scenario, following the concept that mutations at both loci more accurately explain the spectrum of symptoms, but further investigation is needed under this concept. This is the third report linking a LAMA5 variant with human renal disease and expanding the spectrum of genes involved in glomerular pathologies accompanied by familial hematurias. The cystic phenotype overlaps with that of a mouse model, which carried a Lama5 hypomorphic mutation that caused severely reduced Lama5 protein levels and produced kidney cysts.
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Affiliation(s)
- Konstantinos Voskarides
- Molecular Medicine Research Center, Department of Biological Sciences, University of Cyprus, 1, University Avenue, 2109, Nicosia, Cyprus. .,Medical School, University of Cyprus, Nicosia, Cyprus.
| | - Gregory Papagregoriou
- Molecular Medicine Research Center, Department of Biological Sciences, University of Cyprus, 1, University Avenue, 2109, Nicosia, Cyprus
| | - Despina Hadjipanagi
- Molecular Medicine Research Center, Department of Biological Sciences, University of Cyprus, 1, University Avenue, 2109, Nicosia, Cyprus
| | - Ioanelli Petrou
- Molecular Medicine Research Center, Department of Biological Sciences, University of Cyprus, 1, University Avenue, 2109, Nicosia, Cyprus
| | - Isavella Savva
- Molecular Medicine Research Center, Department of Biological Sciences, University of Cyprus, 1, University Avenue, 2109, Nicosia, Cyprus
| | - Avraam Elia
- Department of Pediatric Nephrology, Archbishop Makarios III Hospital, Nicosia, Cyprus
| | | | | | - Maria Kkolou
- Department of Nephrology, Larnaca General Hospital, Larnaca, Cyprus
| | | | | | - Alkis Pierides
- Molecular Medicine Research Center, Department of Biological Sciences, University of Cyprus, 1, University Avenue, 2109, Nicosia, Cyprus.,Hippocrateon Hospital, Nicosia, Cyprus
| | - Constantinos Deltas
- Molecular Medicine Research Center, Department of Biological Sciences, University of Cyprus, 1, University Avenue, 2109, Nicosia, Cyprus. .,College of Medicine, Qatar University, Doha, Qatar.
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26
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Deltas C. Digenic inheritance and genetic modifiers. Clin Genet 2018; 93:429-438. [PMID: 28977688 DOI: 10.1111/cge.13150] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 09/27/2017] [Accepted: 09/28/2017] [Indexed: 12/28/2022]
Abstract
Digenic inheritance (DI) concerns pathologies with the simplest form of multigenic etiology, implicating more than 1 gene (and perhaps the environment). True DI is when biallelic or even triallelic mutations in 2 distinct genes, in cis or in trans, are necessary and sufficient to cause pathology with a defined diagnosis. In true DI, a heterozygous mutation in each of 2 genes alone is not associated with a recognizable phenotype. Well-documented diseases with true DI are so far rare and follow non-Mendelian inheritance. DI is also encountered when by serendipity, pathogenic mutations responsible for 2 distinct disease entities are co-inherited, leading to a mixed phenotype. Also, we can consider many true monogenic Mendelian conditions, which show impressively broad spectrum of phenotypes due to pseudo-DI, as a result of co-inheriting genetic modifiers (GMs). I am herewith reviewing examples of GM and embark on presenting some recent notable examples of true DI, with wider discussion of the literature. Undeniably, the advent of high throughput sequencing is bound to unravel more patients suffering with true DI conditions and elucidate many important GM, thus impacting precision medicine.
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Affiliation(s)
- C Deltas
- College of Medicine, Qatar University, Doha, Qatar.,Department of Biological Sciences, Molecular Medicine Research Center, University of Cyprus, Nicosia, Cyprus
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