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Tasaki Y, Tsujimoto H, Yokoyama T, Sugimoto N, Kitajima S, Fujii H, Hidaka Y, Kato N, Maruyama S, Inoue N, Wada T. Case report: A family of atypical hemolytic uremic syndrome involving a CFH::CFHR1 fusion gene and CFHR3-1-4-2 gene duplication. Front Immunol 2024; 15:1360855. [PMID: 38524137 PMCID: PMC10957550 DOI: 10.3389/fimmu.2024.1360855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Accepted: 02/27/2024] [Indexed: 03/26/2024] Open
Abstract
Mutations in the complement factor H (CFH) gene are associated with complement dysregulation and the development of atypical hemolytic uremic syndrome (aHUS). Several fusion genes that result from genomic structural variation in the CFH and complement factor H-related (CFHR) gene regions have been identified in aHUS. However, one allele has both CFHR gene duplication and CFH::CFHR1 fusion gene have not been reported. An 8-month-old girl (proband) presented with aHUS and was treated with ravulizumab. Her paternal grandfather developed aHUS previously and her paternal great grandmother presented with anti-neutrophil cytoplasmic antibody-associated vasculitis and thrombotic microangiopathy (TMA). However, the proband's parents have no history of TMA. A genetic analysis revealed the presence of CFH::CFHR1 fusion gene and a CFHR3-1-4-2 gene duplication in the patient, her father, and her paternal grandfather. Although several fusion genes resulting from structural variations of the CFH-CFHR genes region have been identified, this is the first report of the combination of a CFH::CFHR1 fusion gene with CFHR gene duplication. Because the CFH-CFHR region is highly homologous, we hypothesized that CFHR gene duplication occurred. These findings indicate a novel pathogenic genomic structural variation associated with the development of aHUS.
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Affiliation(s)
- Yuko Tasaki
- Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical, and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Hiroshi Tsujimoto
- Department of Molecular Genetics, Wakayama Medical University, Wakayama, Japan
| | - Tadafumi Yokoyama
- Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical, and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Naotoshi Sugimoto
- Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical, and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Shinji Kitajima
- Department of Nephrology and Rheumatology, Kanazawa University, Kanazawa, Japan
| | - Hiroshi Fujii
- Department of Nephrology and Rheumatology, Ishikawa Prefectural Central Hospital, Kanazawa, Japan
| | - Yoshihiko Hidaka
- Department of Molecular Genetics, Wakayama Medical University, Wakayama, Japan
| | - Noritoshi Kato
- Department of Nephrology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shoichi Maruyama
- Department of Nephrology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Norimitsu Inoue
- Department of Molecular Genetics, Wakayama Medical University, Wakayama, Japan
| | - Taizo Wada
- Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical, and Health Sciences, Kanazawa University, Kanazawa, Japan
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Piras R, Valoti E, Alberti M, Bresin E, Mele C, Breno M, Liguori L, Donadelli R, Rigoldi M, Benigni A, Remuzzi G, Noris M. CFH and CFHR structural variants in atypical Hemolytic Uremic Syndrome: Prevalence, genomic characterization and impact on outcome. Front Immunol 2023; 13:1011580. [PMID: 36793547 PMCID: PMC9923232 DOI: 10.3389/fimmu.2022.1011580] [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: 08/04/2022] [Accepted: 12/28/2022] [Indexed: 01/31/2023] Open
Abstract
Introduction Atypical hemolytic uremic syndrome (aHUS) is a rare disease that manifests with microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure, and is associated with dysregulation of the alternative complement pathway. The chromosomal region including CFH and CFHR1-5 is rich in repeated sequences, favoring genomic rearrangements that have been reported in several patients with aHUS. However, there are limited data on the prevalence of uncommon CFH-CFHR genomic rearrangements in aHUS and their impact on disease onset and outcomes. Methods In this study, we report the results of CFH-CFHR Copy Number Variation (CNV) analysis and the characterization of resulting structural variants (SVs) in a large cohort of patients, including 258 patients with primary aHUS and 92 with secondary forms. Results We found uncommon SVs in 8% of patients with primary aHUS: 70% carried rearrangements involving CFH alone or CFH and CFHR (group A; n=14), while 30% exhibited rearrangements including only CFHRs (group B; n=6). In group A, 6 patients presented CFH::CFHR1 hybrid genes, 7 patients carried duplications in the CFH-CFHR region that resulted either in the substitution of the last CFHR1 exon(s) with those of CFH (CFHR1::CFH reverse hybrid gene) or in an internal CFH duplication. In group A, the large majority of aHUS acute episodes not treated with eculizumab (12/13) resulted in chronic ESRD; in contrast, anti-complement therapy induced remission in 4/4 acute episodes. aHUS relapse occurred in 6/7 grafts without eculizumab prophylaxis and in 0/3 grafts with eculizumab prophylaxis. In group B, 5 subjects had the CFHR31-5::CFHR410 hybrid gene and one had 4 copies of CFHR1 and CFHR4. Compared with group A, patients in group B exhibited a higher prevalence of additional complement abnormalities and earlier disease onset. However, 4/6 patients in this group underwent complete remission without eculizumab treatment. In secondary forms we identified uncommon SVs in 2 out of 92 patients: the CFHR31-5::CFHR410 hybrid and a new internal duplication of CFH. Discussion In conclusion, these data highlight that uncommon CFH-CFHR SVs are frequent in primary aHUS and quite rare in secondary forms. Notably, genomic rearrangements involving the CFH are associated with a poor prognosis but carriers respond to anti-complement therapy.
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Rodríguez de Córdoba S. Genetic variability shapes the alternative pathway complement activity and predisposition to complement-related diseases. Immunol Rev 2023; 313:71-90. [PMID: 36089777 PMCID: PMC10086816 DOI: 10.1111/imr.13131] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The implementation of next-generation sequencing technologies has provided a sharp picture of the genetic variability in the components and regulators of the alternative pathway (AP) of the complement system and has revealed the association of many AP variants with different rare and common diseases. An important finding that has emerged from these analyses is that each of these complement-related diseases associate with genetic variants altering specific aspects of the activation and regulation of the AP. These genotype-phenotype correlations have provided valuable insights into their pathogenic mechanisms with important diagnostic and therapeutic implications. While genetic variants in coding regions and structural variants are reasonably well characterized and occasionally have been instrumental to uncover unknown features of the complement proteins, data about complement expressed quantitative trait loci are still very limited. A crucial task for future studies will be to identify these quantitative variations and to determine their impact in the overall activity of the AP. This is fundamental as it is now clear that the consequences of genetic variants in the AP are additive and that susceptibility or resistance to disease is the result of specific combinations of genetic variants in different complement components and regulators ("complotypes").
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Lucientes-Continente L, Márquez-Tirado B, Goicoechea de Jorge E. The Factor H protein family: The switchers of the complement alternative pathway. Immunol Rev 2023; 313:25-45. [PMID: 36382387 PMCID: PMC10099856 DOI: 10.1111/imr.13166] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The factor H (FH) protein family is emerging as a complex network of proteins controlling the fate of the complement alternative pathway (AP) and dictating susceptibility to a wide range of diseases including infectious, inflammatory, autoimmune, and degenerative diseases and cancer. Composed, in man, of seven highly related proteins, FH, factor H-like 1, and 5 factor H-related proteins, some of the FH family proteins are devoted to down-regulating the AP, while others exert an opposite function by promoting AP activation. Recent findings have provided insights into the molecular mechanisms defining their biological roles and their pathogenicity, illustrating the relevance that the balance between the regulators and the activators within this protein family has in defining the outcome of complement activation on cell surfaces. In this review we will discuss the emerging roles of the factor H protein family, their impact in the complement cascade, and their involvement in the pathogenesis of complement-mediated diseases associated with the AP dysregulation.
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Affiliation(s)
- Laura Lucientes-Continente
- Department of Immunology, Ophthalmology and ENT, School of Medicine, Complutense University and Research Institute Hospital 12 de Octubre (imas12), Madrid, Spain
| | - Bárbara Márquez-Tirado
- Department of Immunology, Ophthalmology and ENT, School of Medicine, Complutense University and Research Institute Hospital 12 de Octubre (imas12), Madrid, Spain
| | - Elena Goicoechea de Jorge
- Department of Immunology, Ophthalmology and ENT, School of Medicine, Complutense University and Research Institute Hospital 12 de Octubre (imas12), Madrid, Spain
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5
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Unraveling Structural Rearrangements of the CFH Gene Cluster in Atypical Hemolytic Uremic Syndrome Patients Using Molecular Combing and Long-Fragment Targeted Sequencing. J Mol Diagn 2022; 24:619-631. [PMID: 35398599 DOI: 10.1016/j.jmoldx.2022.02.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 02/01/2022] [Accepted: 02/25/2022] [Indexed: 11/22/2022] Open
Abstract
Complement factor H (CFH) and its related proteins have an essential role in regulating the alternative pathway of the complement system. Mutations and structural variants (SVs) of the CFH gene cluster, consisting of CFH and its five related genes (CFHR1-5), have been reported in renal pathologies as well as in complex immune diseases like age-related macular degeneration and systemic lupus erythematosus. SV analysis of this cluster is challenging because of its high degree of sequence homology. Following first-line next-generation sequencing gene panel sequencing, we applied Genomic Vision's Molecular Combing Technology to detect and visualize SVs within the CFH gene cluster and resolve its structural haplotypes completely. This approach was tested in three patients with atypical hemolytic uremic syndrome and known SVs and 18 patients with atypical hemolytic uremic syndrome or complement factor 3 glomerulopathy with unknown CFH gene cluster haplotypes. Three SVs, a CFH/CFHR1 hybrid gene in two patients and a rare heterozygous CFHR4/CFHR1 deletion in trans with the common CFHR3/CFHR1 deletion in a third patient, were newly identified. For the latter, the breakpoints were determined using a targeted enrichment approach for long DNA fragments (Samplix Xdrop) in combination with Oxford Nanopore sequencing. Molecular combing in addition to next-generation sequencing was able to improve the molecular genetic yield in this pilot study. This (cost-)effective approach warrants validation in larger cohorts with CFH/CFHR-associated disease.
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Park J, Yhim HY, Kang KP, Bae TW, Cho YG. Copy number variation analysis using next-generation sequencing identifies the CFHR3/ CFHR1 deletion in atypical hemolytic uremic syndrome: a case report. Hematology 2022; 27:603-608. [PMID: 35617302 DOI: 10.1080/16078454.2022.2075121] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
OBJECTIVES Atypical hemolytic uremic syndrome (aHUS) is characterized by a triad of thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure resulting from platelet thrombi in the microcirculation of the kidney and other organs, in the absence of a preceding diarrheal illness. This report describes a case in which copy number variation (CNV) analysis using next-generation sequencing (NGS) identified the CFHR3/CFHR1 deletion in a patient with aHUS. METHODS A 49-year-old Korean female was diagnosed with aHUS based on clinical findings, including schistocytes in peripheral blood and marked thrombocytopenia, suggesting the presence of thrombotic microangiopathy, elevated serum lactate dehydrogenase, and acute kidney injury. Sequence variants and CNV generated from NGS data were estimated to determine if there was a potential genetic cause. Multiplex ligation-dependent probe amplification (MLPA) was conducted to confirm the CFHR3/CFHR1 deletion identified by NGS with CNV analysis. RESULTS No known or novel pathogenic single nucleotide variant or small insertion/deletion that would be predicted to have damaging effects that could lead to aHUS were identified. However, CNV analysis of NGS data identified the heterozygous CFHR3/CFHR1 deletion. MLPA confirmed this loss of one copy number between the CFHR3 and the CFHR1 genes on chromosome 1q31.3. CONCLUSION We genetically diagnosed a Korean woman harboring a heterozygous CFHR3/CFHR1 deletion of a known causative gene for aHUS. Our report emphasizes the need for CNV analysis of NGS data and gene dosage assays, such as MLPA, to evaluate large-scale deletions or duplications and generate hybrid CFH genes in patients with suspected aHUS.
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Affiliation(s)
- Joonhong Park
- Department of Laboratory Medicine, Jeonbuk National University Medical School and Hospital, Jeonju, Korea.,Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Korea
| | - Ho-Young Yhim
- Department of Internal Medicine, Jeonbuk National University Medical School and Hospital, Jeonju, Korea.,Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Korea
| | - Kyung Pyo Kang
- Department of Internal Medicine, Jeonbuk National University Medical School and Hospital, Jeonju, Korea.,Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Korea
| | - Tae Won Bae
- Department of Laboratory Medicine, Jeonbuk National University Medical School and Hospital, Jeonju, Korea.,Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Korea
| | - Yong Gon Cho
- Department of Laboratory Medicine, Jeonbuk National University Medical School and Hospital, Jeonju, Korea.,Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Korea
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7
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Xu B, Kang Y, Du Y, Guo W, Zhu L, Zhang H. Atypical Hemolytic Uremic Syndrome-Associated FHR1 Isoform FHR1*B Enhances Complement Activation and Inflammation. Front Immunol 2022; 13:755694. [PMID: 35126388 PMCID: PMC8814109 DOI: 10.3389/fimmu.2022.755694] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 01/03/2022] [Indexed: 11/13/2022] Open
Abstract
Atypical hemolytic uremic syndrome (aHUS) is a rare but severe type of thrombotic microangiopathy that is triggered by the abnormal activation of the alternative complement pathway. Previous studies have reported that three completely linked coding variants of CFHR1 form two haplotypes, namely, CFHR1*A (c.469C, c.475C, c.523G) and CFHR1*B (c.469T, c.475G, c.523C). CFHR1*B is associated with susceptibility to aHUS. To explore the genetic mechanism by which CFHR1 isoforms contribute to aHUS, we compared the structures of FHR1*A and FHR1*B by homology modeling and found differences in the angles between SCR3 and SCR4-SCR5, as FHR1*B had a larger angle than FHR1*A. Then, we expressed FHR1*A and FHR1*B recombinant proteins and compared their functions in complement system regulation and inflammation. We found that FHR1*B presented a significantly higher capacity for binding C3b and necrotic cells than FHR1*A. In a cofactor assay, the FHR-1*B showed stronger influence on FH mediated cofactor function than the FHR-1*A, resulted in fewer C3b cleavage products. In the C3 convertase assays, FHR1*B showed more powerful effect compared with FHR1*A regarding to de-regulate FH function of inhibition the assembling of C3bBb. Additionally, we also found that FHR1*B triggered monocytes to secrete higher levels of IL-1β and IL-6 than FHR1*A. In the present study, we showed that variants of CFHR1 might differently affect complement activation and sterile inflammation. Our findings provide a possible mechanism underlying the predisposition to aHUS caused by CFHR1 isoform CFHR1*B.
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Affiliation(s)
- Boyang Xu
- Renal Division, Department of Medicine, Peking University First Hospital, Peking University Institute of Nephrology, Key Laboratory of Renal Disease (Peking University), National Health Commission, Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education, Beijing, China
| | - Yuqi Kang
- Renal Division, Department of Medicine, Peking University First Hospital, Peking University Institute of Nephrology, Key Laboratory of Renal Disease (Peking University), National Health Commission, Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education, Beijing, China
| | - Yujing Du
- Department of Nuclear Medicine, Peking University First Hospital, Beijing, China
| | - Weiyi Guo
- Renal Division, Department of Medicine, Peking University First Hospital, Peking University Institute of Nephrology, Key Laboratory of Renal Disease (Peking University), National Health Commission, Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education, Beijing, China
| | - Li Zhu
- Renal Division, Department of Medicine, Peking University First Hospital, Peking University Institute of Nephrology, Key Laboratory of Renal Disease (Peking University), National Health Commission, Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education, Beijing, China
| | - Hong Zhang
- Renal Division, Department of Medicine, Peking University First Hospital, Peking University Institute of Nephrology, Key Laboratory of Renal Disease (Peking University), National Health Commission, Key Laboratory of Chronic Kidney Disease Prevention and Treatment, Ministry of Education, Beijing, China
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8
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Piras R, Breno M, Valoti E, Alberti M, Iatropoulos P, Mele C, Bresin E, Donadelli R, Cuccarolo P, Smith RJH, Benigni A, Remuzzi G, Noris M. CFH and CFHR Copy Number Variations in C3 Glomerulopathy and Immune Complex-Mediated Membranoproliferative Glomerulonephritis. Front Genet 2021; 12:670727. [PMID: 34211499 PMCID: PMC8240960 DOI: 10.3389/fgene.2021.670727] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 05/14/2021] [Indexed: 11/13/2022] Open
Abstract
C3 Glomerulopathy (C3G) and Immune Complex-Mediated Membranoproliferative glomerulonephritis (IC-MPGN) are rare diseases characterized by glomerular deposition of C3 caused by dysregulation of the alternative pathway (AP) of complement. In approximately 20% of affected patients, dysregulation is driven by pathogenic variants in the two components of the AP C3 convertase, complement C3 (C3) and Factor B (CFB), or in complement Factor H (CFH) and Factor I (CFI), two genes that encode complement regulators. Copy number variations (CNVs) involving the CFH-related genes (CFHRs) that give rise to hybrid FHR proteins also have been described in a few C3G patients but not in IC-MPGN patients. In this study, we used multiplex ligation-dependent probe amplification (MLPA) to study the genomic architecture of the CFH-CFHR region and characterize CNVs in a large cohort of patients with C3G (n = 103) and IC-MPGN (n = 96) compared to healthy controls (n = 100). We identified new/rare CNVs resulting in structural variants (SVs) in 5 C3G and 2 IC-MPGN patients. Using long-read single molecule real-time sequencing (SMRT), we detected the breakpoints of three SVs. The identified SVs included: 1) a deletion of the entire CFH in one patient with IC-MPGN; 2) an increased number of CFHR4 copies in one IC-MPGN and three C3G patients; 3) a deletion from CFHR3-intron 3 to CFHR3-3'UTR (CFHR34 - 6 Δ) that results in a FHR3-FHR1 hybrid protein in a C3G patient; and 4) a CFHR31 - 5-CFHR410 hybrid gene in a C3G patient. This work highlights the contribution of CFH-CFHR CNVs to the pathogenesis of both C3G and IC-MPGN.
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Affiliation(s)
- Rossella Piras
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | - Matteo Breno
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | - Elisabetta Valoti
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | - Marta Alberti
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | | | - Caterina Mele
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | - Elena Bresin
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | - Roberta Donadelli
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | - Paola Cuccarolo
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | - Richard J H Smith
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Ariela Benigni
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | - Giuseppe Remuzzi
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
| | - Marina Noris
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy
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9
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Poppelaars F, Goicoechea de Jorge E, Jongerius I, Baeumner AJ, Steiner MS, Józsi M, Toonen EJM, Pauly D. A Family Affair: Addressing the Challenges of Factor H and the Related Proteins. Front Immunol 2021; 12:660194. [PMID: 33868311 PMCID: PMC8044877 DOI: 10.3389/fimmu.2021.660194] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 03/08/2021] [Indexed: 12/19/2022] Open
Abstract
Inflammation is a common denominator of diseases. The complement system, an intrinsic part of the innate immune system, is a key driver of inflammation in numerous disorders. Recently, a family of proteins has been suggested to be of vital importance in conditions characterized by complement dysregulation: the human Factor H (FH) family. This group of proteins consists of FH, Factor H-like protein 1 and five Factor H-related proteins. The FH family has been linked to infectious, vascular, eye, kidney and autoimmune diseases. In contrast to FH, the functions of the other highly homologous proteins are largely unknown and, hence, their role in the different disease-specific pathogenic mechanisms remains elusive. In this perspective review, we address the major challenges ahead in this emerging area, including 1) the controversies about the functional roles of the FH protein family, 2) the discrepancies in quantification of the FH protein family, 3) the unmet needs for validated tools and 4) limitations of animal models. Next, we also discuss the opportunities that exist for the immunology community. A strong multidisciplinary approach is required to solve these obstacles and is only possible through interdisciplinary collaboration between biologists, chemists, geneticists and physicians. We position this review in light of our own perspective, as principal investigators of the SciFiMed Consortium, a consortium aiming to create a comprehensive analytical system for the quantitative and functional assessment of the entire FH protein family.
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Affiliation(s)
- Felix Poppelaars
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Elena Goicoechea de Jorge
- Department of Immunology, Faculty of Medicine, Complutense University and Research Institute Hospital 12 de Octubre (imas12), Madrid, Spain
| | - Ilse Jongerius
- Department of Immunopathology, Sanquin Research and Landsteiner Laboratory of the Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
- Department of Pediatric Immunology, Rheumatology, and Infectious Diseases, Emma Children’s Hospital, Amsterdam University Medical Centre, Amsterdam, Netherlands
| | - Antje J. Baeumner
- Institute of Analytical Chemistry, Chemo-and Biosensors, Faculty of Chemistry and Pharmacy, University of Regensburg, Regensburg, Germany
| | | | - Mihály Józsi
- Department of Immunology, ELTE Eötvös Loránd University, Budapest, Hungary
- MTA-ELTE Complement Research Group, Eötvös Loránd Research Network (ELKH), Department of Immunology, ELTE Eötvös Loránd University, Budapest, Hungary
| | | | - Diana Pauly
- Department of Ophthalmology, University Hospital Regensburg, Regensburg, Germany
- Experimental Ophthalmology, University Marburg, Marburg, Germany
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10
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Australia and New Zealand renal gene panel testing in routine clinical practice of 542 families. NPJ Genom Med 2021; 6:20. [PMID: 33664247 PMCID: PMC7933190 DOI: 10.1038/s41525-021-00184-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 01/25/2021] [Indexed: 12/11/2022] Open
Abstract
Genetic testing in nephrology clinical practice has moved rapidly from a rare specialized test to routine practice both in pediatric and adult nephrology. However, clear information pertaining to the likely outcome of testing is still missing. Here we describe the experience of the accredited Australia and New Zealand Renal Gene Panels clinical service, reporting on sequencing for 552 individuals from 542 families with suspected kidney disease in Australia and New Zealand. An increasing number of referrals have been processed since service inception with an overall diagnostic rate of 35%. The likelihood of identifying a causative variant varies according to both age at referral and gene panel. Although results from high throughput genetic testing have been primarily for diagnostic purposes, they will increasingly play an important role in directing treatment, genetic counseling, and family planning.
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11
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Dunne OM, Gao X, Nan R, Gor J, Adamson PJ, Gordon DL, Moulin M, Haertlein M, Forsyth VT, Perkins SJ. A Dimerization Site at SCR-17/18 in Factor H Clarifies a New Mechanism for Complement Regulatory Control. Front Immunol 2021; 11:601895. [PMID: 33552059 PMCID: PMC7859452 DOI: 10.3389/fimmu.2020.601895] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 12/03/2020] [Indexed: 11/15/2022] Open
Abstract
Complement Factor H (CFH), with 20 short complement regulator (SCR) domains, regulates the alternative pathway of complement in part through the interaction of its C-terminal SCR-19 and SCR-20 domains with host cell-bound C3b and anionic oligosaccharides. In solution, CFH forms small amounts of oligomers, with one of its self-association sites being in the SCR-16/20 domains. In order to correlate CFH function with dimer formation and the occurrence of rare disease-associated variants in SCR-16/20, we identified the dimerization site in SCR-16/20. For this, we expressed, in Pichia pastoris, the five domains in SCR-16/20 and six fragments of this with one-three domains (SCR-19/20, SCR-18/20, SCR-17/18, SCR-16/18, SCR-17 and SCR-18). Size-exclusion chromatography suggested that SCR dimer formation occurred in several fragments. Dimer formation was clarified using analytical ultracentrifugation, where quantitative c(s) size distribution analyses showed that SCR-19/20 was monomeric, SCR-18/20 was slightly dimeric, SCR-16/20, SCR-16/18 and SCR-18 showed more dimer formation, and SCR-17 and SCR-17/18 were primarily dimeric with dissociation constants of ~5 µM. The combination of these results located the SCR-16/20 dimerization site at SCR-17 and SCR-18. X-ray solution scattering experiments and molecular modelling fits confirmed the dimer site to be at SCR-17/18, this dimer being a side-by-side association of the two domains. We propose that the self-association of CFH at SCR-17/18 enables higher concentrations of CFH to be achieved when SCR-19/20 are bound to host cell surfaces in order to protect these better during inflammation. Dimer formation at SCR-17/18 clarified the association of genetic variants throughout SCR-16/20 with renal disease.
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Affiliation(s)
- Orla M Dunne
- Division of Biosciences, Department of Structural and Molecular Biology, University College London, London, United Kingdom.,Life Sciences Group, Institut Laue Langevin, Grenoble, France
| | - Xin Gao
- Division of Biosciences, Department of Structural and Molecular Biology, University College London, London, United Kingdom.,Division of Medicine, University College London, London, United Kingdom
| | - Ruodan Nan
- Division of Biosciences, Department of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Jayesh Gor
- Division of Biosciences, Department of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Penelope J Adamson
- Department of Microbiology and Infectious Diseases, Flinders Medical Centre and Flinders University, Bedford Park, SA, Australia
| | - David L Gordon
- Department of Microbiology and Infectious Diseases, Flinders Medical Centre and Flinders University, Bedford Park, SA, Australia
| | - Martine Moulin
- Life Sciences Group, Institut Laue Langevin, Grenoble, France
| | | | - V Trevor Forsyth
- Life Sciences Group, Institut Laue Langevin, Grenoble, France.,Faculty of Natural Sciences, Keele University, Staffordshire, United Kingdom
| | - Stephen J Perkins
- Division of Biosciences, Department of Structural and Molecular Biology, University College London, London, United Kingdom
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12
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Skerka C, Pradel G, Halder LD, Zipfel PF, Zipfel SLH, Strauß O. Factor H-related protein 1: a complement regulatory protein and guardian of necrotic-type surfaces. Br J Pharmacol 2020; 178:2823-2831. [PMID: 33085794 DOI: 10.1111/bph.15290] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 09/21/2020] [Accepted: 10/01/2020] [Indexed: 11/30/2022] Open
Abstract
Factor H-related protein 1 (FHR-1) is a member of the factor H protein family, which is involved in regulating innate immune complement reactions. Genetic modification of the encoding gene, CFHR1 on human chromosome 1, is involved in diseases such as age-related macular degeneration, C3 glomerulopathy and atypical haemolytic uraemic syndrome, indicating an important role for FHR-1 in human health. Recent research data demonstrate that FHR-1 levels increase in IgA nephropathy and anti-neutrophilic cytoplasmic autoantibodies (ANCA) vasculitis and that FHR-1 induces strong inflammation in monocytes on necrotic-type surfaces, suggesting a complement-independent role. These new results increase our knowledge about the role of this complement protein in pathology and provide a new therapeutic target, particularly in the context of inflammatory diseases induced by necrosis. This review summarizes current knowledge about FHR-1 and discusses its role in complement reactions and inflammation. LINKED ARTICLES: This article is part of a themed issue on Canonical and non-canonical functions of the complement system in health and disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.14/issuetoc.
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Affiliation(s)
- Christine Skerka
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knöll-Institute, Jena, Germany
| | - Gabriele Pradel
- Division of Cellular and Applied Infection Biology, RWTH Aachen University, Aachen, Germany
| | - Luke D Halder
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knöll-Institute, Jena, Germany
| | - Peter F Zipfel
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knöll-Institute, Jena, Germany
| | - Svante L H Zipfel
- Department of Cardiovascular Surgery, University Heart Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Olaf Strauß
- Experimental Ophthalmology, Charité University Medicine, Campus Virchow Clinic, Berlin, Germany
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13
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Zipfel PF, Wiech T, Stea ED, Skerka C. CFHR Gene Variations Provide Insights in the Pathogenesis of the Kidney Diseases Atypical Hemolytic Uremic Syndrome and C3 Glomerulopathy. J Am Soc Nephrol 2020; 31:241-256. [PMID: 31980588 PMCID: PMC7003313 DOI: 10.1681/asn.2019050515] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Sequence and copy number variations in the human CFHR-Factor H gene cluster comprising the complement genes CFHR1, CFHR2, CFHR3, CFHR4, CFHR5, and Factor H are linked to the human kidney diseases atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy. Distinct genetic and chromosomal alterations, deletions, or duplications generate hybrid or mutant CFHR genes, as well as hybrid CFHR-Factor H genes, and alter the FHR and Factor H plasma repertoire. A clear association between the genetic modifications and the pathologic outcome is emerging: CFHR1, CFHR3, and Factor H gene alterations combined with intact CFHR2, CFHR4, and CFHR5 genes are reported in atypical hemolytic uremic syndrome. But alterations in each of the five CFHR genes in the context of an intact Factor H gene are described in C3 glomerulopathy. These genetic modifications influence complement function and the interplay of the five FHR proteins with each other and with Factor H. Understanding how mutant or hybrid FHR proteins, Factor H::FHR hybrid proteins, and altered Factor H, FHR plasma profiles cause pathology is of high interest for diagnosis and therapy.
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Affiliation(s)
- Peter F Zipfel
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany;
- Institute of Microbiology, Friedrich-Schiller-University, Jena, Germany; and
| | - Thorsten Wiech
- Section of Nephropathology, Institute of Pathology, University Hospital Hamburg-Eppendorf, Hamburg, Germany
| | - Emma D Stea
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany
| | - Christine Skerka
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany
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14
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Deletions in Genes Participating in Innate Immune Response Modify the Clinical Course of Andes Orthohantavirus Infection. Viruses 2019; 11:v11080680. [PMID: 31349540 PMCID: PMC6723883 DOI: 10.3390/v11080680] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 06/28/2019] [Accepted: 07/09/2019] [Indexed: 12/16/2022] Open
Abstract
Andes orthohantavirus (ANDV) is an important human pathogen causing hantavirus cardiopulmonary syndrome (HCPS) with a fatality rate of 30% in Chile. Around 60% of all cases have a severe clinical course, while the others have a mild clinical course. The main goal of this study was to understand if the genetic variation of patients is associated with the clinical course they develop after ANDV infection. For this, the frequency of copy number variants (CNVs, i.e., deletions and duplications) was studied in 195 patients, 88 with mild and 107 with severe HCPS. CNVs were called from intensity data of the Affymetrix Genome-Wide SNP Array 6.0. The analysis of the data was performed with PennCNV, ParseCNV and R softwares; Results: a deletion of 19, 416 bp in the q31.3 region of chromosome 1 is found more frequently in severe patients (p < 0.05). This region contains Complement Factor H Related (CFHR1) and CFHR3 genes, regulators of the complement cascade. A second deletion of 1.81 kb located in the p13 region of chr20 was significantly more frequent in mild patients (p < 0.05). This region contains the SIRPB1 gene, which participates in the innate immune response, more specifically in neutrophil trans-epithelial migration. Both deletions are associated with the clinical course of HCPS, the first being a risk factor and the second being protective. The participation of genes contained in both deletions in ANDV infection pathophysiology deserves further investigation.
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15
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Altered Peripheral Blood Leucocyte Phenotype and Responses in Healthy Individuals with Homozygous Deletion of FHR1 and FHR3 Genes. J Clin Immunol 2019; 39:336-345. [DOI: 10.1007/s10875-019-00619-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 03/26/2019] [Indexed: 01/10/2023]
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16
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Abstract
The role of the complement factor H-related (FHR) proteins in homeostasis, pathogen defense, and autoimmune disease has recently attracted considerable interest. We highlight the exciting research that has contributed to our understanding of the FHR protein family. Unlike factor H, a potent negative regulator of complement C3 activation, the FHR proteins appear to promote C3 activation. These data have important implications for understanding complement-mediated diseases because, depending on the context, the balance between the actions of factor H and the FHR proteins determines the degree of complement activation.
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Affiliation(s)
| | - Matthew C Pickering
- Centre for Complement and Inflammation Research, Imperial College, London, UK
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17
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Abstract
The complement system is an essential part of the innate immune system that requires careful regulation to ensure responses are appropriately directed against harmful pathogens, while preventing collateral damage to normal host cells and tissues. While deficiency in some components of the complement pathway is associated with increased susceptibility to certain infections, it has also become clear that inappropriate activation of complement is an important contributor to human disease. A number of hematologic disorders are driven by complement, and these disorders may be termed "complementopathies". This includes paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), cold agglutinin disease (CAD) and other related disorders, which will be the focus of this review. A better understanding of the central role of the complement system in the pathophysiology of these disorders may allow for application of therapies directed at blocking the complement cascade.
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Affiliation(s)
- Andrea C Baines
- Division of Hematology, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.
| | - Robert A Brodsky
- Division of Hematology, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.
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18
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Kousios A. Does complement Factor H-Related protein 5 Nephropathy (Troodos Nephropathy) protect from rickettsial infections? Med Hypotheses 2017; 98:76-80. [DOI: 10.1016/j.mehy.2016.11.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 11/25/2016] [Indexed: 10/20/2022]
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19
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Schäfer N, Grosche A, Reinders J, Hauck SM, Pouw RB, Kuijpers TW, Wouters D, Ehrenstein B, Enzmann V, Zipfel PF, Skerka C, Pauly D. Complement Regulator FHR-3 Is Elevated either Locally or Systemically in a Selection of Autoimmune Diseases. Front Immunol 2016; 7:542. [PMID: 27965669 PMCID: PMC5124756 DOI: 10.3389/fimmu.2016.00542] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 11/16/2016] [Indexed: 12/30/2022] Open
Abstract
The human complement factor H-related protein-3 (FHR-3) is a soluble regulator of the complement system. Homozygous cfhr3/1 deletion is a genetic risk factor for the autoimmune form of atypical hemolytic-uremic syndrome (aHUS), while also found to be protective in age-related macular degeneration (AMD). The precise function of FHR-3 remains to be fully characterized. We generated four mouse monoclonal antibodies (mAbs) for FHR-3 (RETC) without cross-reactivity to the complement factor H (FH)-family. These antibodies detected FHR-3 from human serum with a mean concentration of 1 μg/mL. FHR-3 levels in patients were significantly increased in sera from systemic lupus erythematosus, rheumatoid arthritis, and polymyalgia rheumatica but remained almost unchanged in samples from AMD or aHUS patients. Moreover, by immunostaining of an aged human donor retina, we discovered a local FHR-3 production by microglia/macrophages. The mAb RETC-2 modulated FHR-3 binding to C3b but not the binding of FHR-3 to heparin. Interestingly, FHR-3 competed with FH for binding C3b and the mAb RETC-2 reduced the interaction of FHR-3 and C3b, resulting in increased FH binding. Our results unveil a previously unknown systemic involvement of FHR-3 in rheumatoid diseases and a putative local role of FHR-3 mediated by microglia/macrophages in the damaged retina. We conclude that the local FHR-3/FH equilibrium in AMD is a potential therapeutic target, which can be modulated by our specific mAb RETC-2.
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Affiliation(s)
- Nicole Schäfer
- Department of Ophthalmology, University Hospital Regensburg , Regensburg , Germany
| | - Antje Grosche
- Institute of Human Genetics, University of Regensburg , Regensburg , Germany
| | - Joerg Reinders
- Institute of Functional Genomics, University of Regensburg , Regensburg , Germany
| | - Stefanie M Hauck
- Research Unit Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH) , Neuherberg , Germany
| | - Richard B Pouw
- Department of Immunopathology, Sanquin Research and Landsteiner Laboratory of the Academic Medical Center, University of Amsterdam , Amsterdam , Netherlands
| | - Taco W Kuijpers
- Department of Pediatric Hematology, Immunology and Infectious Diseases, Academic Medical Center, Emma Children's Hospital, Amsterdam, Netherlands; Department of Blood Cell Research, Sanquin Research and Landsteiner Laboratory of the Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Diana Wouters
- Department of Immunopathology, Sanquin Research and Landsteiner Laboratory of the Academic Medical Center, University of Amsterdam , Amsterdam , Netherlands
| | - Boris Ehrenstein
- Klinik und Poliklinik für Rheumatologie und Klinische Immunologie, Asklepios Klinikum Bad Abbach , Bad Abbach , Germany
| | - Volker Enzmann
- Department of Ophthalmology, Inselspital, University of Bern , Bern , Switzerland
| | - Peter F Zipfel
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany; Friedrich Schiller University, Jena, Germany
| | - Christine Skerka
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology , Jena , Germany
| | - Diana Pauly
- Department of Ophthalmology, University Hospital Regensburg , Regensburg , Germany
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20
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Challis RC, Araujo GSR, Wong EKS, Anderson HE, Awan A, Dorman AM, Waldron M, Wilson V, Brocklebank V, Strain L, Morgan BP, Harris CL, Marchbank KJ, Goodship THJ, Kavanagh D. A De Novo Deletion in the Regulators of Complement Activation Cluster Producing a Hybrid Complement Factor H/Complement Factor H-Related 3 Gene in Atypical Hemolytic Uremic Syndrome. J Am Soc Nephrol 2015; 27:1617-24. [PMID: 26490391 DOI: 10.1681/asn.2015010100] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 09/07/2015] [Indexed: 02/06/2023] Open
Abstract
The regulators of complement activation cluster at chromosome 1q32 contains the complement factor H (CFH) and five complement factor H-related (CFHR) genes. This area of the genome arose from several large genomic duplications, and these low-copy repeats can cause genome instability in this region. Genomic disorders affecting these genes have been described in atypical hemolytic uremic syndrome, arising commonly through nonallelic homologous recombination. We describe a novel CFH/CFHR3 hybrid gene secondary to a de novo 6.3-kb deletion that arose through microhomology-mediated end joining rather than nonallelic homologous recombination. We confirmed a transcript from this hybrid gene and showed a secreted protein product that lacks the recognition domain of factor H and exhibits impaired cell surface complement regulation. The fact that the formation of this hybrid gene arose as a de novo event suggests that this cluster is a dynamic area of the genome in which additional genomic disorders may arise.
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Affiliation(s)
| | | | | | | | - Atif Awan
- Department of Nephrology, Our Lady's Children's Hospital, Crumlin, Dublin
| | - Anthony M Dorman
- Department of Renal Pathology, Beaumont Hospital, Royal College of Surgeons in Ireland, Dublin, Ireland; and
| | - Mary Waldron
- Department of Nephrology, Our Lady's Children's Hospital, Crumlin, Dublin
| | | | | | | | - B Paul Morgan
- Institute of Infection and Immunity, Cardiff University School of Medicine, Cardiff, United Kingdom
| | - Claire L Harris
- Institute of Infection and Immunity, Cardiff University School of Medicine, Cardiff, United Kingdom
| | - Kevin J Marchbank
- Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
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21
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Zipfel PF, Skerka C, Chen Q, Wiech T, Goodship T, Johnson S, Fremeaux-Bacchi V, Nester C, de Córdoba SR, Noris M, Pickering M, Smith R. The role of complement in C3 glomerulopathy. Mol Immunol 2015; 67:21-30. [PMID: 25929733 DOI: 10.1016/j.molimm.2015.03.012] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/09/2015] [Accepted: 03/10/2015] [Indexed: 12/12/2022]
Abstract
C3 glomerulopathy describes a spectrum of disorders with glomerular pathology associated with C3 cleavage product deposition and with defective complement action and regulation (Fakhouri et al., 2010; Sethi et al., 2012b). Kidney biopsies from these patients show glomerular accumulation or deposition of C3 cleavage fragments, but no or minor deposition of immunoglobulins (Appel et al., 2005; D'Agati and Bomback, 2012; Servais et al., 2007; Sethi and Fervenza, 2011). At present the current situation asks for a better definition of the underlining disease mechanisms, for precise biomarkers, and for a treatment for this disease. The complement system is a self activating and propelling enzymatic cascade type system in which inactive, soluble plasma components are activated spontaneously and lead into an amplification loop (Zipfel and Skerka, 2009). Activation of the alternative pathway is spontaneous, occurs by default, and cascade progression leads to amplification by complement activators. The system however is self-controlled by multiple regulators and inhibitors, like Factor H that control cascade progression in fluid phase and on surfaces. The activated complement system generates a series of potent effector components and activation products, which damage foreign-, as well as modified self cells, recruit innate immune cells to the site of action, coordinate inflammation and the response of the adaptive immune system in form of B cells and T lymphocytes (Kohl, 2006; Medzhitov and Janeway, 2002; Ogden and Elkon, 2006; Carroll, 2004; Kemper and Atkinson, 2007; Morgan, 1999; Muller-Eberhard, 1986; Ricklin et al., 2010). Complement controls homeostasis and multiple reactions in the vertebrate organism including defense against microbial infections (Diaz-Guillen et al., 1999; Mastellos and Lambris, 2002; Nordahl et al., 2004; Ricklin et al., 2010). In consequence defective control of the spontaneous self amplifying cascade or regulation is associated with numerous human disorders (Ricklin and Lambris, 2007; Skerka and Zipfel, 2008; Zipfel et al., 2006). Understanding the exact action and regulation of this sophisticated homeotic cascade system is relevant to understand disease pathology of various complement associated human disorders. Furthermore this knowledge is relevant for a better diagnosis and appropriate therapy. At present diagnosis of C3 glomerulopathy is primarily based on the kidney biopsy, and histological, immmunohistological and electron microscopical evaluation (D'Agati and Bomback, 2012; Fakhouri et al., 2010; Medjeral-Thomas et al., 2014a,b; Sethi et al., 2012b). The challenge is to define the actual cause of the diverse glomerular changes or damages, to define how C3 deposition results in the reported glomerular changes, the location of the cell damage and the formation of deposits.
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Affiliation(s)
- Peter F Zipfel
- Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany; Friedrich Schiller University Jena, Germany.
| | - Christine Skerka
- Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany
| | - Qian Chen
- Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany
| | - Thorsten Wiech
- Institute for Pathology, University Hospital Hamburg-Eppendorf, Hamburg, Germany
| | - Tim Goodship
- Institute of Human Genetics, University of Newcastle upon Tyne, United Kingdom
| | - Sally Johnson
- Institute of Human Genetics, University of Newcastle upon Tyne, United Kingdom
| | - Veronique Fremeaux-Bacchi
- Assistance Publique-Hopitaux de Paris, Hospital European Georges-Pompidou and INSERM UMRS 1138, "Complement and Diseases" Team, Cordelier Research Center, Paris, France
| | - Clara Nester
- University of Iowa Carver College of Medicine, Otolaryngology, Iowa City, IA 52242, USA
| | - Santiago Rodríguez de Córdoba
- Departamento de Medicina Celular y Molecular, and Ciber de Enfermedades Raras, Centro de Investigaciones Biológicas, Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Marina Noris
- Mario Negri Institute for Pharmacological Research, Ranica, Bergamo, Italy
| | | | - Richard Smith
- University of Iowa Carver College of Medicine, Otolaryngology, Iowa City, IA 52242, USA
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22
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Nester CM, Barbour T, de Cordoba SR, Dragon-Durey MA, Fremeaux-Bacchi V, Goodship THJ, Kavanagh D, Noris M, Pickering M, Sanchez-Corral P, Skerka C, Zipfel P, Smith RJH. Atypical aHUS: State of the art. Mol Immunol 2015; 67:31-42. [PMID: 25843230 DOI: 10.1016/j.molimm.2015.03.246] [Citation(s) in RCA: 191] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 03/11/2015] [Accepted: 03/12/2015] [Indexed: 12/12/2022]
Abstract
Tremendous advances in our understanding of the thrombotic microangiopathies (TMAs) have revealed distinct disease mechanisms within this heterogeneous group of diseases. As a direct result of this knowledge, both children and adults with complement-mediated TMA now enjoy higher expectations for long-term health. In this update on atypical hemolytic uremic syndrome, we review the clinical characteristics; the genetic and acquired drivers of disease; the broad spectrum of environmental triggers; and current diagnosis and treatment options. Many questions remain to be addressed if additional improvements in patient care and outcome are to be achieved in the coming decade.
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Affiliation(s)
- Carla M Nester
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA, USA; Division of Nephrology, Stead Family Department of Pediatrics, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Thomas Barbour
- Centre for Complement and Inflammation Research, Department of Medicine, Imperial College, London W12 0NN, UK
| | | | - Marie Agnes Dragon-Durey
- Assistance Publique - Hopitaux de Paris, Service d'Immunologie Biologique, Hopital Europeen Georges Pompidou, Paris, France
| | - Veronique Fremeaux-Bacchi
- Assistance Publique - Hopitaux de Paris, Service d'Immunologie Biologique, Hopital Europeen Georges Pompidou, Paris, France
| | - Tim H J Goodship
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - David Kavanagh
- Assistance Publique - Hopitaux de Paris, Service d'Immunologie Biologique, Hopital Europeen Georges Pompidou, Paris, France
| | - Marina Noris
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Clinical Research Center for Rare Diseases "Aldo e Cele Daccò", Ranica, Bergamo, Italy
| | - Matthew Pickering
- Centre for Complement and Inflammation Research, Department of Medicine, Imperial College, London W12 0NN, UK
| | - Pilar Sanchez-Corral
- Unidad de Investigación and Ciber de Enfermedades Raras, Hospital Universitario de La Paz_IdiPAZ, Paseo de la Castellana 261, 28046 Madrid, Spain
| | - Christine Skerka
- Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany
| | - Peter Zipfel
- Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany; Friedrich Schiller University, Jena, Germany
| | - Richard J H Smith
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA, USA; Division of Nephrology, Stead Family Department of Pediatrics, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.
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23
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Mol JPS, Costa EA, Carvalho AF, Sun YH, Tsolis RM, Paixão TA, Santos RL. Early transcriptional responses of bovine chorioallantoic membrane explants to wild type, ΔvirB2 or ΔbtpB Brucella abortus infection. PLoS One 2014; 9:e108606. [PMID: 25259715 PMCID: PMC4178178 DOI: 10.1371/journal.pone.0108606] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 08/29/2014] [Indexed: 12/23/2022] Open
Abstract
The pathogenesis of the Brucella-induced inflammatory response in the bovine placenta is not completely understood. In this study we evaluated the role of the B. abortus Type IV secretion system and the anti-inflammatory factor BtpB in early interactions with bovine placental tissues. Transcription profiles of chorioallantoic membrane (CAM) explants inoculated with wild type (strain 2308), ΔvirB2 or ΔbtpB Brucella abortus were compared by microarray analysis at 4 hours post infection. Transcripts with significant variation (>2 fold change; P<0.05) were functionally classified, and transcripts related to defense and inflammation were assessed by quantitative real time RT-PCR. Infection with wild type B. abortus resulted in slightly more genes with decreased than increased transcription levels. Conversely, infection of trophoblastic cells with the ΔvirB2 or the ΔbtpB mutant strains, that lack a functional T4SS or that has impaired inhibition of TLR signaling, respectively, induced more upregulated than downregulated genes. Wild type Brucella abortus impaired transcription of host genes related to immune response when compared to ΔvirB and ΔbtpB mutants. Our findings suggest that proinflammatory genes are negatively modulated in bovine trophoblastic cells at early stages of infection. The virB operon and btpB are directly or indirectly related to modulation of these host genes. These results shed light on the early interactions between B. abortus and placental tissue that ultimately culminate in inflammatory pathology and abortion.
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Affiliation(s)
- Juliana P. S. Mol
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Erica A. Costa
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Alex F. Carvalho
- Departamento de Medicina Veterinária Preventiva, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Yao-Hui Sun
- Department of Medical Microbiology and Immunology, School of Medicine, University of California Davis, Davis, California, United States of America
| | - Reneé M. Tsolis
- Department of Medical Microbiology and Immunology, School of Medicine, University of California Davis, Davis, California, United States of America
| | - Tatiane A. Paixão
- Departamento de Patologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Renato L. Santos
- Departamento de Clínica e Cirurgia Veterinárias, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
- * E-mail:
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24
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Valoti E, Alberti M, Tortajada A, Garcia-Fernandez J, Gastoldi S, Besso L, Bresin E, Remuzzi G, Rodriguez de Cordoba S, Noris M. A novel atypical hemolytic uremic syndrome-associated hybrid CFHR1/CFH gene encoding a fusion protein that antagonizes factor H-dependent complement regulation. J Am Soc Nephrol 2014; 26:209-19. [PMID: 24904082 DOI: 10.1681/asn.2013121339] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Genomic aberrations affecting the genes encoding factor H (FH) and the five FH-related proteins (FHRs) have been described in patients with atypical hemolytic uremic syndrome (aHUS), a rare condition characterized by microangiopathic hemolytic anemia, thrombocytopenia, and ARF. These genomic rearrangements occur through nonallelic homologous recombinations caused by the presence of repeated homologous sequences in CFH and CFHR1-R5 genes. In this study, we found heterozygous genomic rearrangements among CFH and CFHR genes in 4.5% of patients with aHUS. CFH/CFHR rearrangements were associated with poor clinical prognosis and high risk of post-transplant recurrence. Five patients carried known CFH/CFHR1 genes, but we found a duplication leading to a novel CFHR1/CFH hybrid gene in a family with two affected subjects. The resulting fusion protein contains the first four short consensus repeats of FHR1 and the terminal short consensus repeat 20 of FH. In an FH-dependent hemolysis assay, we showed that the hybrid protein causes sheep erythrocyte lysis. Functional analysis of the FHR1 fraction purified from serum of heterozygous carriers of the CFHR1/CFH hybrid gene indicated that the FHR1/FH hybrid protein acts as a competitive antagonist of FH. Furthermore, sera from carriers of the hybrid CFHR1/CFH gene induced more C5b-9 deposition on endothelial cells than control serum. These results suggest that this novel genomic hybrid mediates disease pathogenesis through dysregulation of complement at the endothelial cell surface. We recommend that genetic screening of aHUS includes analysis of CFH and CFHR rearrangements, particularly before a kidney transplant.
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Affiliation(s)
- Elisabetta Valoti
- IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri," Clinical Research Center for Rare Diseases "Aldo e Cele Daccò," and "Centro Anna Maria Astori" Science and Technology Park Kilometro Rosso, Bergamo, Italy
| | - Marta Alberti
- IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri," Clinical Research Center for Rare Diseases "Aldo e Cele Daccò," and "Centro Anna Maria Astori" Science and Technology Park Kilometro Rosso, Bergamo, Italy
| | - Agustin Tortajada
- Centro de Investigaciones Biològicas and Centro de Investigacion Biomédica en Enfermedades Rares, Madrid, Spain
| | - Jesus Garcia-Fernandez
- Centro de Investigaciones Biològicas and Centro de Investigacion Biomédica en Enfermedades Rares, Madrid, Spain
| | - Sara Gastoldi
- IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri," Clinical Research Center for Rare Diseases "Aldo e Cele Daccò," and "Centro Anna Maria Astori" Science and Technology Park Kilometro Rosso, Bergamo, Italy
| | - Luca Besso
- Unit of Nephrology, Dialysis and Transplantation, Molinette Hospital, Turin, Italy; and
| | - Elena Bresin
- IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri," Clinical Research Center for Rare Diseases "Aldo e Cele Daccò," and "Centro Anna Maria Astori" Science and Technology Park Kilometro Rosso, Bergamo, Italy
| | - Giuseppe Remuzzi
- IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri," Clinical Research Center for Rare Diseases "Aldo e Cele Daccò," and "Centro Anna Maria Astori" Science and Technology Park Kilometro Rosso, Bergamo, Italy; Unit of Nephrology and Dialysis, Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy
| | | | - Marina Noris
- IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri," Clinical Research Center for Rare Diseases "Aldo e Cele Daccò," and "Centro Anna Maria Astori" Science and Technology Park Kilometro Rosso, Bergamo, Italy;
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Human factor H-related protein 2 (CFHR2) regulates complement activation. PLoS One 2013; 8:e78617. [PMID: 24260121 PMCID: PMC3832495 DOI: 10.1371/journal.pone.0078617] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Accepted: 09/13/2013] [Indexed: 11/25/2022] Open
Abstract
Mutations and deletions within the human CFHR gene cluster on chromosome 1 are associated with diseases, such as dense deposit disease, CFHR nephropathy or age-related macular degeneration. Resulting mutant CFHR proteins can affect complement regulation. Here we identify human CFHR2 as a novel alternative pathway complement regulator that inhibits the C3 alternative pathway convertase and terminal pathway assembly. CFHR2 is composed of four short consensus repeat domains (SCRs). Two CFHR2 molecules form a dimer through their N-terminal SCRs, and each of the two C-terminal ends can bind C3b. C3b bound CFHR2 still allows C3 convertase formation but the CFHR2 bound convertases do not cleave the substrate C3. Interestingly CFHR2 hardly competes off factor H from C3b. Thus CFHR2 likely acts in concert with factor H, as CFHR2 inhibits convertases while simultaneously allowing factor H assisted degradation by factor I.
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Skerka C, Chen Q, Fremeaux-Bacchi V, Roumenina LT. Complement factor H related proteins (CFHRs). Mol Immunol 2013; 56:170-80. [PMID: 23830046 DOI: 10.1016/j.molimm.2013.06.001] [Citation(s) in RCA: 178] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 05/08/2013] [Indexed: 02/06/2023]
Abstract
Factor H related proteins comprise a group of five plasma proteins: CFHR1, CFHR2, CFHR3, CFHR4 and CFHR5, and each member of this group binds to the central complement component C3b. Mutations, genetic deletions, duplications or rearrangements in the individual CFHR genes are associated with a number of diseases including atypical hemolytic uremic syndrome (aHUS), C3 glomerulopathies (C3 glomerulonephritis (C3GN), dense deposit disease (DDD) and CFHR5 nephropathy), IgA nephropathy, age related macular degeneration (AMD) and systemic lupus erythematosus (SLE). Although complement regulatory functions were attributed to most of the members of the CFHR protein family, the precise role of each CFHR protein in complement activation and the exact contribution to disease pathology is still unclear. Recent publications show that CFHR proteins form homo- as well as heterodimers. Genetic abnormalities within the CFHR gene locus can result in hybrid proteins with affected dimerization or recognition domains which cause defective functions. Here we summarize the recent data about CFHR genes and proteins in order to better understand the role of CFHR proteins in complement activation and in complement associated diseases.
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Affiliation(s)
- Christine Skerka
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany.
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27
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Determining the population frequency of the CFHR3/CFHR1 deletion at 1q32. PLoS One 2013; 8:e60352. [PMID: 23613724 PMCID: PMC3629053 DOI: 10.1371/journal.pone.0060352] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 02/25/2013] [Indexed: 01/04/2023] Open
Abstract
In this study we have used multiplex ligation-dependent probe amplification (MLPA) to measure the copy number of CFHR3 and CFHR1 in DNA samples from 238 individuals from the UK and 439 individuals from the HGDP-CEPH Human Genome Diversity Cell Line Panel. We have then calculated the allele frequency and frequency of homozygosity for the copy number polymorphism represented by the CFHR3/CFHR1 deletion. There was a highly significant difference between geographical locations in both the allele frequency (X2 = 127.7, DF = 11, P-value = 4.97x10-22) and frequency of homozygosity (X2 = 142.3, DF = 22, P-value = 1.33x10-19). The highest frequency for the deleted allele (54.7%) was seen in DNA samples from Nigeria and the lowest (0%) in samples from South America and Japan. The observed frequencies in conjunction with the known association of the deletion with AMD, SLE and IgA nephropathy is in keeping with differences in the prevalence of these diseases in African and European Americans. This emphasises the importance of identifying copy number polymorphism in disease.
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Contribution of the infection-associated complement regulator-acquiring surface protein 4 (ErpC) to complement resistance of Borrelia burgdorferi. Clin Dev Immunol 2012; 2012:349657. [PMID: 22400034 PMCID: PMC3287035 DOI: 10.1155/2012/349657] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 10/05/2011] [Indexed: 11/17/2022]
Abstract
Borrelia burgdorferi evades complement-mediated killing by interacting with complement regulators through distinct complement regulator-acquiring surface proteins (CRASPs). Here, we extend our analyses to the contribution of CRASP-4 in mediating complement resistance of B. burgdorferi and its interaction with human complement regulators. CRASP-4 (also known as ErpC) was immobilized onto magnetic beads and used to capture proteins from human serum. Following Western blotting, factor H (CFH), CFH-related protein 1 (CFHR1), CFHR2, and CFHR5 were identified as ligands of CRASP-4. To analyze the impact of native CRASP-4 on mediating survival of serum-sensitive cells in human serum, a B. garinii strain was generated that ectopically expresses CRASP-4. CRASP-4-producing bacteria bound CFHR1, CFHR2, and CFHR5 but not CFH. In addition, transformed spirochetes deposited significant amounts of lethal complement components on their surface and were susceptible to human serum, thus indicating that CRASP-4 plays a subordinate role in complement resistance of B. burgdorferi.
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29
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A novel hybrid CFH/CFHR3 gene generated by a microhomology-mediated deletion in familial atypical hemolytic uremic syndrome. Blood 2012; 119:591-601. [DOI: 10.1182/blood-2011-03-339903] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Genomic disorders affecting the genes encoding factor H (fH) and the 5 factor H related proteins have been described in association with atypical hemolytic uremic syndrome. These include deletions of CFHR3, CFHR1, and CFHR4 in association with fH autoantibodies and the formation of a hybrid CFH/CFHR1 gene. These occur through nonallelic homologous recombination secondary to the presence of large segmental duplications (macrohomology) in this region. Using multiplex ligation-dependent probe amplification to screen for such genomic disorders, we have identified a large atypical hemolytic uremic syndrome family where a deletion has occurred through microhomology-mediated end joining rather than nonallelic homologous recombination. In the 3 affected persons of this family, we have shown that the deletion results in formation of a CFH/CFHR3 gene. We have shown that the protein product of this is a 24 SCR protein that is secreted with normal fluid-phase activity but marked loss of complement regulation at cell surfaces despite increased heparin binding. In this study, we have therefore shown that microhomology in this area of chromosome 1 predisposes to disease associated genomic disorders and that the complement regulatory function of fH at the cell surface is critically dependent on the structural integrity of the whole molecule.
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Kokotas H, Grigoriadou M, Petersen MB. Age-related macular degeneration: genetic and clinical findings. Clin Chem Lab Med 2010; 49:601-16. [PMID: 21175380 DOI: 10.1515/cclm.2011.091] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Age-related macular degeneration (AMD) is a sight threatening eye disease that affects millions of humans over the age of 65 years. It is considered to be the major cause of irreversible blindness in the elderly population in the developed world. The disease is prevalent in Europe and the United States, which has a large number of individuals of European descent. AMD is characterized by a progressive loss of central vision attributable to degenerative and neovascular changes that occur in the interface between the neural retina and the underlying choroid. This location contains the retinal photoreceptors, the retinal pigmented epithelium, a basement membrane complex known as Bruch's membrane and a network of choroidal capillaries. AMD is increasingly recognized as a complex genetic disorder where one or more genes contribute to an individual's susceptibility to development of the condition, while the prevailing view is that the disease stems from the interaction of multiple genetic and environmental factors. Although it has been proposed that a threshold event occurs during normal aging, the sequelae of biochemical, cellular, and molecular events leading to AMD are not fully understood. Here, we review the clinical aspects of AMD and summarize the genes which have been reported to have a positive association with the disease.
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Affiliation(s)
- Haris Kokotas
- Department of Genetics, Institute of Child Health, Aghia Sophia Children's Hospital, Athens, Greece.
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31
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Fritsche LG, Lauer N, Hartmann A, Stippa S, Keilhauer CN, Oppermann M, Pandey MK, Köhl J, Zipfel PF, Weber BHF, Skerka C. An imbalance of human complement regulatory proteins CFHR1, CFHR3 and factor H influences risk for age-related macular degeneration (AMD). Hum Mol Genet 2010; 19:4694-704. [PMID: 20843825 DOI: 10.1093/hmg/ddq399] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A frequent deletion of complement factor H (CFH)-related genes CFHR3 and CFHR1 (ΔCFHR3/CFHR1) is considered to have a protective effect against age-related macular degeneration (AMD), although the underlying mechanism remains elusive. The deletion seems to be linked to one of the two protective CFH haplotypes which are both tagged by the protective allele of single nucleotide polymorphism rs2274700 (CFH:A473A). In a German cohort of 530 AMD patients, we now show that protection against AMD conferred by ΔCFHR3/CFHR1 is independent of the effects of rs2274700 and rs1061170 (CFH:Y402H). This suggests a functional role of CFHR1 and/or CFHR3 in disease pathogenesis. We therefore characterized the CFHR3 function and identified CFHR3 as a novel human complement regulator that inhibits C3 convertase activity. CFHR3 displays anti-inflammatory effects by blocking C5a generation and C5a-mediated chemoattraction of neutrophils. In addition, CFHR3 and CFHR1 compete with factor H for binding to the central complement component C3. Thus, deficiency of CFHR3 and CFHR1 results in a loss of complement control but enhances local regulation by factor H. Our findings allude to a critical balance between the complement regulators CFHR3, CFHR1 and factor H and further emphasize the central role of complement regulation in AMD pathology.
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Affiliation(s)
- Lars G Fritsche
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, Regensburg, Germany
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32
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Buhé V, Loisel S, Pers JO, Le Ster K, Berthou C, Youinou P. Updating the physiology, exploration and disease relevance of complement factor H. Int J Immunopathol Pharmacol 2010; 23:397-404. [PMID: 20646335 DOI: 10.1177/039463201002300202] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The factor H (FH) protein (also known as beta1H globulin) is the main regulator of the complement alternative pathway. It exhibits multivalent binding sites to the complement component C3b, and polyanions and one binding site to sialic acid and cell surfaces. These multiple binding sites confer to FH a decay-accelerating factor activity in the fluid phase as well as at the cell surface. A defect in FH activity or a FH protein deficiency triggers chronic inflammation and tissue injury, leading to various disorders impacting the kidney or the eye. In contrast, some pathogens, as well as cancer cells, develop various strategies to bind FH and thereby subvert a complement attack. We focus on the functions of FH, and review the main pathological conditions in which FH is involved. Since the pathogenesis is elusive, appropriate FH dosage in biological fluids and FH gene analysis may help in improving understanding of such diseases.
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34
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de Córdoba SR, de Jorge EG. Translational mini-review series on complement factor H: genetics and disease associations of human complement factor H. Clin Exp Immunol 2008; 151:1-13. [PMID: 18081690 PMCID: PMC2276932 DOI: 10.1111/j.1365-2249.2007.03552.x] [Citation(s) in RCA: 223] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2007] [Indexed: 12/13/2022] Open
Abstract
Factor H is an abundant plasma glycoprotein that plays a critical role in the regulation of the complement system in plasma and in the protection of host cells and tissues from damage by complement activation. Several recent studies have described the association of genetic variations of the complement factor H gene (CFH) with atypical haemolytic uraemic syndrome (aHUS), age-related macular degeneration (AMD) and membranoproliferative glomerulonephritis (MPGN). This review summarizes our current knowledge of CFH genetics and examines the CFH genotype-phenotype correlations that are helping to understand the molecular basis underlying these renal and ocular pathologies.
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Affiliation(s)
- S Rodríguez de Córdoba
- Centro de Investigaciones Biológicas and Centro de Investigación Biomédica en Red de Enfermedades Raras, Madrid, Spain.
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35
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Zipfel PF, Edey M, Heinen S, Józsi M, Richter H, Misselwitz J, Hoppe B, Routledge D, Strain L, Hughes AE, Goodship JA, Licht C, Goodship THJ, Skerka C. Deletion of complement factor H-related genes CFHR1 and CFHR3 is associated with atypical hemolytic uremic syndrome. PLoS Genet 2007; 3:e41. [PMID: 17367211 PMCID: PMC1828695 DOI: 10.1371/journal.pgen.0030041] [Citation(s) in RCA: 260] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Accepted: 02/01/2007] [Indexed: 12/12/2022] Open
Abstract
Atypical hemolytic uremic syndrome (aHUS) is associated with defective complement regulation. Disease-associated mutations have been described in the genes encoding the complement regulators complement factor H, membrane cofactor protein, factor B, and factor I. In this study, we show in two independent cohorts of aHUS patients that deletion of two closely related genes, complement factor H–related 1 (CFHR1) and complement factor H–related 3 (CFHR3), increases the risk of aHUS. Amplification analysis and sequencing of genomic DNA of three affected individuals revealed a chromosomal deletion of ∼84 kb in the RCA gene cluster, resulting in loss of the genes coding for CFHR1 and CFHR3, but leaving the genomic structure of factor H intact. The CFHR1 and CFHR3 genes are flanked by long homologous repeats with long interspersed nuclear elements (retrotransposons) and we suggest that nonallelic homologous recombination between these repeats results in the loss of the two genes. Impaired protection of erythrocytes from complement activation is observed in the serum of aHUS patients deficient in CFHR1 and CFHR3, thus suggesting a regulatory role for CFHR1 and CFHR3 in complement activation. The identification of CFHR1/CFHR3 deficiency in aHUS patients may lead to the design of new diagnostic approaches, such as enhanced testing for these genes. Hemolytic uremic syndrome (HUS) is a severe kidney disease, which is characterized by hemolytic anemia, thrombocytopenia, and acute renal failure. The nondiarrhea-associated form, also known as atypical HUS (aHUS), is rare, sometimes familial, often recurrent, and has a poor outcome. Several studies have shown that aHUS is associated with mutations in genes coding for complement regulators, which leads to defective regulation of complement activation, particularly at cell surfaces. We report a novel susceptibility factor for aHUS in the form of a chromosomal deletion of a large (∼84 kb) genomic fragment in the regulators of complement activation gene cluster at Chromosome 1q32. This deletion is a result of nonallelic homologous recombination and leads to the loss of two genes, CFHR1 and CFHR3, which encode factor H–related proteins 1 and 3, respectively. We recommend diagnostic screening of aHUS patients for these susceptibility factors.
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Affiliation(s)
- Peter F Zipfel
- Leibniz Institute for Natural Product Research and Infection Biology, Hans Knoell Institute, Jena, Germany
- Friedrich Schiller University, Jena, Germany
| | - Matthew Edey
- Institute of Human Genetics, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Stefan Heinen
- Leibniz Institute for Natural Product Research and Infection Biology, Hans Knoell Institute, Jena, Germany
| | - Mihály Józsi
- Leibniz Institute for Natural Product Research and Infection Biology, Hans Knoell Institute, Jena, Germany
| | - Heiko Richter
- Leibniz Institute for Natural Product Research and Infection Biology, Hans Knoell Institute, Jena, Germany
| | | | - Bernd Hoppe
- Children's Hospital of the University of Cologne, Cologne, Germany
| | - Danny Routledge
- Northern Molecular Genetics Service Laboratory, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Lisa Strain
- Northern Molecular Genetics Service Laboratory, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Anne E Hughes
- Department of Medical Genetics, Queen's University, Belfast, United Kingdom
| | - Judith A Goodship
- Institute of Human Genetics, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Christoph Licht
- Division of Nephrology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Timothy H. J Goodship
- Institute of Human Genetics, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Christine Skerka
- Leibniz Institute for Natural Product Research and Infection Biology, Hans Knoell Institute, Jena, Germany
- * To whom correspondence should be addressed. E-mail:
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36
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Hellwage J, Eberle F, Babuke T, Seeberger H, Richter H, Kunert A, Härtl A, Zipfel PF, Jokiranta TS, Józsi M. Two factor H-related proteins from the mouse: expression analysis and functional characterization. Immunogenetics 2006; 58:883-93. [PMID: 17028856 DOI: 10.1007/s00251-006-0153-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2006] [Accepted: 08/15/2006] [Indexed: 10/24/2022]
Abstract
Complement factor H-related (FHR) proteins display structural and functional similarities to each other and to the complement regulator factor H (FH). FHRs have been identified in various species, including human, rat, and the fish barred sand bass. As mice provide a useful model system to study the physiological role of FHRs in vivo, we aimed at characterizing murine FHR proteins. Two putative FHRs of approximately 100 and 38 kDa were detected in mouse plasma using FH-specific antiserum. In a liver cDNA library, three murine FHR-encoding transcripts were identified. Two clones code for related FHR proteins termed FHR-C and FHR-C_v1, which in secreted form are composed of 14 and 13 short consensus repeat (SCR) domains, homologous to SCRs 6-17 and 19-20 of FH. The third transcript, FHR-B, is derived from a separate gene and codes for a secreted protein composed of five SCR domains. FHR-B displays homology to SCRs 5-7 and 19-20 of FH. Expression of FHR-B in various tissues was analyzed by real-time polymerase chain reaction and was identified at high levels in liver, kidney and heart. In liver, FHR-B transcript level was even higher than that of FH. In addition, FHR-B was expressed as a recombinant 37-kDa protein, and this recombinant FHR-B interacted with the ligands heparin and human C3b. Using mouse plasma, the native presumptive FHR proteins were also analyzed in binding assays. In summary, we identify two FHR proteins in mice and for the first time characterize a murine FHR as a heparin- and C3b-binding protein.
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Affiliation(s)
- Jens Hellwage
- Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute, Jena, Germany
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37
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Venables JP, Strain L, Routledge D, Bourn D, Powell HM, Warwicker P, Diaz-Torres ML, Sampson A, Mead P, Webb M, Pirson Y, Jackson MS, Hughes A, Wood KM, Goodship JA, Goodship THJ. Atypical haemolytic uraemic syndrome associated with a hybrid complement gene. PLoS Med 2006; 3:e431. [PMID: 17076561 PMCID: PMC1626556 DOI: 10.1371/journal.pmed.0030431] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Accepted: 08/16/2006] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Sequence analysis of the regulators of complement activation (RCA) cluster of genes at chromosome position 1q32 shows evidence of several large genomic duplications. These duplications have resulted in a high degree of sequence identity between the gene for factor H (CFH) and the genes for the five factor H-related proteins (CFHL1-5; aliases CFHR1-5). CFH mutations have been described in association with atypical haemolytic uraemic syndrome (aHUS). The majority of the mutations are missense changes that cluster in the C-terminal region and impair the ability of factor H to regulate surface-bound C3b. Some have arisen as a result of gene conversion between CFH and CFHL1. In this study we tested the hypothesis that nonallelic homologous recombination between low-copy repeats in the RCA cluster could result in the formation of a hybrid CFH/CFHL1 gene that predisposes to the development of aHUS. METHODS AND FINDINGS In a family with many cases of aHUS that segregate with the RCA cluster we used cDNA analysis, gene sequencing, and Southern blotting to show that affected individuals carry a heterozygous CFH/CFHL1 hybrid gene in which exons 1-21 are derived from CFH and exons 22/23 from CFHL1. This hybrid encodes a protein product identical to a functionally significant CFH mutant (c.3572C>T, S1191L and c.3590T>C, V1197A) that has been previously described in association with aHUS. CONCLUSIONS CFH mutation screening is recommended in all aHUS patients prior to renal transplantation because of the high risk of disease recurrence post-transplant in those known to have a CFH mutation. Because of our finding it will be necessary to implement additional screening strategies that will detect a hybrid CFH/CFHL1 gene.
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Affiliation(s)
- Julian P Venables
- Institute of Human Genetics, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
| | - Lisa Strain
- Northern Molecular Genetics Service Laboratory, Newcastle upon Tyne Hospitals National Health Service Trust, Newcastle upon Tyne, United Kingdom
| | - Danny Routledge
- Northern Molecular Genetics Service Laboratory, Newcastle upon Tyne Hospitals National Health Service Trust, Newcastle upon Tyne, United Kingdom
| | - David Bourn
- Northern Molecular Genetics Service Laboratory, Newcastle upon Tyne Hospitals National Health Service Trust, Newcastle upon Tyne, United Kingdom
| | - Helen M Powell
- Northern Molecular Genetics Service Laboratory, Newcastle upon Tyne Hospitals National Health Service Trust, Newcastle upon Tyne, United Kingdom
| | - Paul Warwicker
- Renal Unit, East and North Hertfordshire National Health Service Trust, Stevenage, United Kingdom
| | - Martha L Diaz-Torres
- Institute of Human Genetics, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
| | - Anne Sampson
- Department of Immunology, Newcastle upon Tyne Hospitals National Health Service Trust, Newcastle upon Tyne, United Kingdom
| | - Paul Mead
- Renal Unit, North Cumbria Acute Hospitals National Health Service Trust, Carlisle, United Kingdom
| | - Michelle Webb
- Renal Unit, East Kent Hospitals National Health Service Trust, Canterbury, United Kingdom
| | - Yves Pirson
- Service de Nephrologie, Cliniques Universitaires Saint-Luc, Brussels, Belgium
| | - Michael S Jackson
- Institute of Human Genetics, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
| | - Anne Hughes
- Department of Medical Genetics, Queen's University, Belfast, United Kingdom
| | - Katrina M Wood
- Department of Histopathology, Newcastle upon Tyne Hospitals National Health Service Trust, Newcastle upon Tyne, United Kingdom
| | - Judith A Goodship
- Institute of Human Genetics, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
| | - Timothy H. J Goodship
- Institute of Human Genetics, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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38
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Abstract
Noris and Remuzzi discuss a new study showing an association between atypical haemolytic uremic syndrome and a hybrid complement gene,CFH/CFHL1.
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39
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Richards A, Buddles MR, Donne RL, Kaplan BS, Kirk E, Venning MC, Tielemans CL, Goodship JA, Goodship TH. Factor H mutations in hemolytic uremic syndrome cluster in exons 18-20, a domain important for host cell recognition. Am J Hum Genet 2001; 68:485-90. [PMID: 11170896 PMCID: PMC1235281 DOI: 10.1086/318203] [Citation(s) in RCA: 246] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2000] [Accepted: 12/12/2000] [Indexed: 11/03/2022] Open
Abstract
Several recent studies have established an association between abnormalities of complement factor H (FH) and the development of hemolytic uremic syndrome (HUS). To identify the relative importance of mutations in FH as a cause of HUS, we have undertaken mutation screening of the FH gene in 19 familial and 31 sporadic patients with FH. Mutations were found in two familial and three sporadic patients, and these clustered in exons 18-20, a domain important for host recognition. Moreover, this study demonstrates that familial HUS is likely to be a heterogeneous condition.
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Affiliation(s)
- A Richards
- School of Clinical Medical Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 4LP, United Kingdom
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40
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Vollmer M, Kremer M, Ruf R, Miot S, Nothwang HG, Wirth J, Otto E, Krapf R, Hildebrandt F. Molecular cloning of the critical region for glomerulopathy with fibronectin deposits (GFND) and evaluation of candidate genes. Genomics 2000; 68:127-35. [PMID: 10964510 DOI: 10.1006/geno.2000.6292] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Glomerulopathy with fibronectin deposits (GFND, MIM 601894) is an autosomal dominant kidney disease that leads to terminal renal failure at a median age of 47 years. It represents a distinct entity of membranoproliferative glomerulonephritis (MPGN) type III and is characterized by the unique feature of massive glomerular deposits of fibronectin. We have recently localized a gene locus for GFND to human chromosome 1q32 by total genome linkage analysis in a large kindred, within a 4.1-cM critical interval between markers D1S2872 and D1S2891. This interval contains a cluster of genes for "regulators of complement activation" (RCA), which represent strong candidates for GFND. To identify positional candidate genes for GFND within the critical genetic interval, we here report the cloning of the entire critical GFND region in a complete YAC and partial PAC contig. We constructed a high-resolution transcriptional map, thereby defining positional and functional candidate genes for the disease. To evaluate their role in GFND, we performed functional studies on RCA proteins in GFND patients from the large kindred, as well as mutational analysis of the genes for complement receptor-2 (CR2), membrane cofactor protein (MCP), and decay accelerating factor (DAF). Although no loss-of-function mutation has been identified as yet, these data provide a basis for the examination of candidate genes for GFND and other genes for MPGN, which localize to the vicinity of the GFND region.
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Affiliation(s)
- M Vollmer
- University Children's Hospital Freiburg, Freiburg, Germany
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Male DA, Ormsby RJ, Ranganathan S, Giannakis E, Gordon DL. Complement factor H: sequence analysis of 221 kb of human genomic DNA containing the entire fH, fHR-1 and fHR-3 genes. Mol Immunol 2000; 37:41-52. [PMID: 10781834 DOI: 10.1016/s0161-5890(00)00024-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Complement factor H (fH) is a member of a family of proteins involved in the regulation of complement activation (RCA). These proteins share a common structural motif, the Short Consensus Repeat (SCR), which is structurally conserved among related genes and between phylogenetically divergent species. fH is composed of 20 such SCRs and a variety of biological functions have been localised to specific SCR domains. The majority of individual SCRs identified are encoded by single exons, and processes such as gene conversion, duplication and exon shuffling have been implicated in the evolution and genomic radiation of SCR-encoding genes. We have analysed two GenBank sequence entries relating to two overlapping PAC clones sequenced at the Sanger Centre which contain the entire human fH gene and two adjacent fH-related (fHR) genes, fHR-1 and fHR-3. Here, we report the detailed analysis of the assembled 221 kb of contiguous, ungapped genomic sequence from human chromosome 1q32, in part employing the RUMMAGE-DP automated annotation tool. Genomic duplications involving fH and fHR exons were identified and Alu/L1 repeat dating established that the duplications occurred after the separation of rodent and primate lineages. The analysis indicates that retrotransposition as well as single and multiple exon duplication events are likely to have been involved in SCR radiation and RCA gene evolution, facilitated by conservation of splice-phasing and the single-exon, single-SCR nature of the encoded domains.
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Affiliation(s)
- D A Male
- Department of Microbiology and Infectious Diseases, Flinders Medical Centre, Flinders University of South Australia, Bedford Park, Australia.
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42
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Hellwage J, Jokiranta TS, Koistinen V, Vaarala O, Meri S, Zipfel PF. Functional properties of complement factor H-related proteins FHR-3 and FHR-4: binding to the C3d region of C3b and differential regulation by heparin. FEBS Lett 1999; 462:345-52. [PMID: 10622723 DOI: 10.1016/s0014-5793(99)01554-9] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The human factor H-related proteins FHR-3 and FHR4 are members of a family of proteins related to the complement factor H. Here, we report that the two proteins bind to the C3d region of complement C3b. The apparent K(A) values for the interactions of FHR-3 and FHR-4 with C3b are 7.5 x 10(6) M(-1) and 2.9 x 10(6) M(-1), respectively. Binding studies performed with C3b-coated pneumococci confirmed the results obtained with the biosensor system. A C-terminal construct of factor H showed similar binding characteristics. The interaction of FHR-3, but not of FHR4, with opsonised pneumococci was inhibited by heparin.
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Affiliation(s)
- J Hellwage
- Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
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Rodríguez de Córdoba S, Díaz-Guillén MA, Heine-Suñer D. An integrated map of the human regulator of complement activation (RCA) gene cluster on 1q32. Mol Immunol 1999; 36:803-8. [PMID: 10698333 DOI: 10.1016/s0161-5890(99)00100-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Friese MA, Hellwage J, Jokiranta TS, Meri S, Peter HH, Eibel H, Zipfel PF. FHL-1/reconectin and factor H: two human complement regulators which are encoded by the same gene are differently expressed and regulated. Mol Immunol 1999; 36:809-18. [PMID: 10698334 DOI: 10.1016/s0161-5890(99)00101-7] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
FHL-1/reconectin and factor H are two human complement regulators which are encoded by a single gene. FHL-1/reconectin contains the first 7 of 20 SCR protein domains of factor H and has four unique residues attached to its C-terminal end. The overlapping region of 445 amino acids explains the related complement regulatory functions of the two proteins. However, unique biological functions have also been reported for FHL-1/reconectin, such as cell adhesion and binding to microbial surfaces. Both proteins are synthesised and secreted by the liver. Extrahepatic synthesis occurs in a wide variety of cells, e.g. in monocytes, fibroblasts or neuronal cells. Unexpectedly, FHL-1/reconectin and factor H exhibit distinct expression patterns. This is also observed in disease situations such as in rheumatoid arthritis or malignancies. In rheumatoid arthritis a potentially protective role is suggested by the local synthesis of both FHL-1/reconectin and factor H in synovial fibroblasts and their induction by the anti-inflammatory agent dexamethasone and the cytokine IFN-gamma, but not by TNF-alpha. FHL-1/reconectin is overexpressed in certain tumor cells such as glioblastoma, conferring an exceptional resistance to such cells against complement mediated lysis. Although FHL-1/reconectin and factor H are encoded by a single gene, regulated by the same gene promoter and initiate transcription at the same start site, their transcripts are differently regulated. The putative control levels, which are responsible for this complex regulation, include transcript elongation, RNA processing, alternative splicing and differential poly(A) site selection.
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Affiliation(s)
- M A Friese
- Research Group of Biomolecular Medicine, Bernard Nocht Institute for Tropical Medicine, Hamburg, Germany
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Zipfel PF, Jokiranta TS, Hellwage J, Koistinen V, Meri S. The factor H protein family. IMMUNOPHARMACOLOGY 1999; 42:53-60. [PMID: 10408366 DOI: 10.1016/s0162-3109(99)00015-6] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The factor H gene family provides a prime example of a multidomain multifunctional protein family whose individual members are defined by conserved common structural elements and display diverse but often overlapping functions. The six identified members of this protein family represent secreted plasma proteins that are primarily synthesized in the liver. Here, we summarize the current understanding of the function of these proteins and suggest a common role in complement control. Factor H is the best characterized member and acts as a complement regulator. The protein displays cofactor activity for factor I in the degradation of the central complement component C3b, acts as a decay accelerating factor for the C3 convertase, C3bBb and is a competitor for factor B binding to C3b. Factor H is a multifunctional protein and displays functions outside the complement system: it binds to the cellular integrin receptor (CD11b/CD18), interacts with cell surface glycosaminoglycans and also binds to the surface of certain pathogenic microorganisms. In addition, factor H has several binding sites for the C3 protein. The factor H-like protein 1 (FHL-1) or reconectin shares the complement regulatory functions with factor H and interacts with heparin. The protein displays cell spreading activity and binds to the N-terminus of the streptococcal M protein. The function of the factor H-related proteins (FHR-1 to FHR-4) is currently under investigation. These proteins are differently distributed. Three proteins (FHR-1, FHR-2 and FHR-4) are constituents of lipoproteins, while FHR-3 interacts with heparin. Binding to C3b and C3d has been demonstrated for FHR-3 and FHR-4 and the two proteins display a cofactor related activity.
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Affiliation(s)
- P F Zipfel
- Research Group of Biomolecular Medicine, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
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