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Chu L, Bi C, Wang C, Zhou H. The Relationship between Complements and Age-Related Macular Degeneration and Its Pathogenesis. J Ophthalmol 2024; 2024:6416773. [PMID: 38205100 PMCID: PMC10776198 DOI: 10.1155/2024/6416773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 06/08/2023] [Accepted: 12/23/2023] [Indexed: 01/12/2024] Open
Abstract
Age-related macular degeneration is a retinal disease that causes permanent loss of central vision in people over the age of 65. Its pathogenesis may be related to mitochondrial dysfunction, inflammation, apoptosis, autophagy, complement, intestinal flora, and lipid disorders. In addition, the patient's genes, age, gender, cardiovascular disease, unhealthy diet, and living habits may also be risk factors for this disease. Complement proteins are widely distributed in serum and tissue fluid. In the early 21st century, a connection was found between the complement cascade and age-related macular degeneration. However, little is known about the effect of complement factors on the pathogenesis of age-related macular degeneration. This article reviews the factors associated with age-related macular degeneration, the relationship between each factor and complement, the related functions, and variants and provides new ideas for the treatment of this disease.
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Affiliation(s)
- Liyuan Chu
- Department of Ophthalmology, China–Japan Union Hospital of Jilin University, Changchun, China
| | - Chaoran Bi
- College of Traditional Chinese Medicine, Hainan Medical University, Haikou, Hainan, China
| | - Caiming Wang
- Department of Ophthalmology, China–Japan Union Hospital of Jilin University, Changchun, China
| | - Hongyan Zhou
- Department of Ophthalmology, China–Japan Union Hospital of Jilin University, Changchun, China
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Hallam TM, Sharp SJ, Andreadi A, Kavanagh D. Complement factor I: Regulatory nexus, driver of immunopathology, and therapeutic. Immunobiology 2023; 228:152410. [PMID: 37478687 DOI: 10.1016/j.imbio.2023.152410] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 05/23/2023] [Accepted: 06/01/2023] [Indexed: 07/23/2023]
Abstract
Complement factor I (FI) is the nexus for classical, lectin and alternative pathway complement regulation. FI is an 88 kDa plasma protein that circulates in an inactive configuration until it forms a trimolecular complex with its cofactor and substrate whereupon a structural reorganization allows the catalytic triad to cleave its substrates, C3b and C4b. In keeping with its role as the master complement regulatory enzyme, deficiency has been linked to immunopathology. In the setting of complete FI deficiency, a consumptive C3 deficiency results in recurrent infections with encapsulated microorganisms. Aseptic cerebral inflammation and vasculitic presentations are also less commonly observed. Heterozygous mutations in the factor I gene (CFI) have been demonstrated to be enriched in atypical haemolytic uraemic syndrome, albeit with a very low penetrance. Haploinsufficiency of CFI has also been associated with decreased retinal thickness and is a strong risk factor for the development of age-related macular degeneration. Supplementation of FI using plasma purified or recombinant protein has long been postulated, however, technical difficulties prevented progression into clinical trials. It is only using gene therapy that CFI supplementation has reached the clinic with GT005 in phase I/II clinical trials for geographic atrophy.
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Affiliation(s)
- T M Hallam
- Gyroscope Therapeutics Limited, A Novartis Company, Rolling Stock Yard, London N7 9AS, UK; Translational and Clinical Research Institute, Newcastle University, Newcastle-upon-Tyne NE1 7RU, UK; National Renal Complement Therapeutics Centre, Building 26, Royal Victoria Infirmary, UK
| | - S J Sharp
- Gyroscope Therapeutics Limited, A Novartis Company, Rolling Stock Yard, London N7 9AS, UK
| | - A Andreadi
- Translational and Clinical Research Institute, Newcastle University, Newcastle-upon-Tyne NE1 7RU, UK; National Renal Complement Therapeutics Centre, Building 26, Royal Victoria Infirmary, UK
| | - D Kavanagh
- Translational and Clinical Research Institute, Newcastle University, Newcastle-upon-Tyne NE1 7RU, UK; National Renal Complement Therapeutics Centre, Building 26, Royal Victoria Infirmary, UK; NIHR Newcastle Biomedical Research Centre, Biomedical Research Building, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK.
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Java A, Atkinson J, Hu Z, Pozzi N. Mutations in atypical hemolytic uremic syndrome provide evidence for the role of calcium in complement factor I. Blood 2023; 142:607-610. [PMID: 37363824 PMCID: PMC10447607 DOI: 10.1182/blood.2022019361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 03/29/2023] [Accepted: 04/26/2023] [Indexed: 06/28/2023] Open
Abstract
Atypical hemolytic uremic syndrome (aHUS) is a rare thrombotic microangiopathy. Genetic variants in complement proteins are found in ≈60% of patients. Of these patients, ≈15% carry mutations in complement factor I (CFI). Factor I (FI) is a multidomain serine protease that cleaves and thereby inactivates C3b and C4b in the presence of cofactor proteins. Crystal structures have shown that FI possesses 2 calcium-binding domains, low-density lipoprotein receptor class A (LDLRA) 1 and LDLRA2. Yet, the role of calcium in FI is unknown. We determined that 9 genetic variants identified in aHUS (N151S, G162D, G188A, V230E, A240G, G243R, C247G, A258T, and Q260D) cluster around the calcium-binding site of LDLRA1. Using site-directed mutagenesis, we established that the synthesis of all, except A258T, was impaired, implying defective protein folding, perhaps due to loss of calcium binding. To further explore this possibility, we generated 12 alanine mutants that coordinate with the calcium in LDLRA1 and LDLRA2 (K239A, D242A, I244A, D246A, D252A, E253A, Y276A, N279A, E281A, D283A, D289A, and D290A) and are expected to perturb calcium binding. Except for K239A and Y276A, none of the mutants was secreted. These observations suggest that calcium ions play key structural and functional roles in FI.
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Affiliation(s)
- Anuja Java
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - John Atkinson
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Zheng Hu
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Nicola Pozzi
- Department of Biochemistry and Molecular Biology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, MO
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Seddon JM, Rosner B, De D, Huan T, Java A, Atkinson J. Rare Dysfunctional Complement Factor I Genetic Variants and Progression to Advanced Age-Related Macular Degeneration. OPHTHALMOLOGY SCIENCE 2023; 3:100265. [PMID: 36909148 PMCID: PMC9993025 DOI: 10.1016/j.xops.2022.100265] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 12/02/2022] [Accepted: 12/27/2022] [Indexed: 12/31/2022]
Abstract
Purpose To evaluate associations between rare dysfunctional complement factor I (CFI) genetic variant status and progression to advanced age-related macular degeneration (AAMD), geographic atrophy (GA), and neovascular disease (NV). Design Prospective, longitudinal study. Participants Patients aged 55 to 80 years at baseline identifying as White with non-AAMD in 1 or both eyes at baseline were included. Follow-up grades were assigned as early, intermediate, or AAMD (GA or NV). CFI variants were categorized using genotyping and sequencing platforms. Methods Analyses were performed using the Seddon Longitudinal Cohort Study (N = 2116 subjects, 3901 eyes, and mean follow-up of 8.3 years) and the Age-Related Eye Disease Study (N = 2837 subjects, 5200 eyes, and mean follow-up of 9.2 years). CFI rare variants associated with low serum factor I (FI) protein levels and decreased FI function (type 1), other AMD genetic variants, and demographic, behavioral, and ocular factors were evaluated. Generalized estimating equations methods were used to assess the association between CFI rare variants and progression, independent of other genetic variants and covariates. Main Outcome Measures Progression to AAMD, GA, or NV. Results In the prospective cohort of 4953 subjects (9101 eyes with non-AAMD at baseline), 1% were type 1 rare CFI carriers. Over 12 years, progression to AAMD was 44% for carriers and 20% for noncarriers (P < 0.001), 30% of carriers versus 10% of noncarriers progressed to GA (P < 0.001), and 18% of carriers compared with 11% of noncarriers progressed to NV (P = 0.049). CFI carriers were more likely to have a family history of AMD (P for trend = 0.035) and a higher baseline AMD grade (P < 0.001). After adjusting for all covariates, CFI carrier status was associated with progression to GA (odds ratio [OR] = 1.91; 95% confidence interval [CI] = 1.03, 3.52) but not NV (OR = 0.96). Higher body mass index was associated with progression among CFI carriers (body mass index ≥ 25 vs. < 25; OR = 5.8; 95% CI 1.5, 22.3) but not for noncarriers (OR = 1.1; 95% CI = 0.9, 1.3), with P_interaction = 0.011. Conclusions Results suggest that carriers of rare dysfunctional type 1 CFI variants are at higher risk for progression to AAMD with GA. Financial Disclosures Proprietary or commercial disclosure may be found after the references.
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Key Words
- AAMD, advanced age-related macular degeneration
- AMD, age-related macular degeneration
- AREDS, Age-Related Eye Disease Study
- Advanced age-related macular degeneration
- BMI, body mass index
- C3, complementcomponent 3
- C9, complementcomponent 9
- CD35, cluster of differentiation 35 (also called complement receptor 1)
- CD46, cluster of differentiation 46 (also called membrane cofactor protein)
- CFH, complementfactor H
- CFI, complement factor I
- CI, confidence interval
- COOH, carboxy terminal
- CR1, complement receptor 1
- Complement factor I
- FI, factor I protein
- GA, geographic atrophy
- GRS, genetic risk score
- Genetic variants
- Geographic atrophy
- HR, hazard ratio
- NH2, amino terminal
- NV, neovascular
- Neovascular disease
- OR, odds ratio
- SAS, Statistical Analysis System
- SLCS, Seddon Longitudinal Cohort Study
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Affiliation(s)
- Johanna M. Seddon
- Department of Ophthalmology and Visual Sciences, University of Massachusetts Chan Medical School, Worcester, Massachusetts
| | - Bernard Rosner
- Channing Division of Network Medicine, Harvard Medical School, Boston, Massachusetts
| | - Dikha De
- Department of Ophthalmology and Visual Sciences, University of Massachusetts Chan Medical School, Worcester, Massachusetts
| | - Tianxiao Huan
- Department of Ophthalmology and Visual Sciences, University of Massachusetts Chan Medical School, Worcester, Massachusetts
| | - Anuja Java
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - John Atkinson
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
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Hallam TM, Cox TE, Smith-Jackson K, Brocklebank V, Baral AJ, Tzoumas N, Steel DH, Wong EKS, Shuttleworth VG, Lotery AJ, Harris CL, Marchbank KJ, Kavanagh D. A novel method for real-time analysis of the complement C3b:FH:FI complex reveals dominant negative CFI variants in age-related macular degeneration. Front Immunol 2022; 13:1028760. [PMID: 36643920 PMCID: PMC9832388 DOI: 10.3389/fimmu.2022.1028760] [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: 08/26/2022] [Accepted: 11/14/2022] [Indexed: 12/29/2022] Open
Abstract
Age-related macular degeneration (AMD) is linked to 2 main disparate genetic pathways: a chromosome 10 risk locus and the alternative pathway (AP) of complement. Rare genetic variants in complement factor H (CFH; FH) and factor I (CFI; FI) are associated with AMD. FH acts as a soluble cofactor to facilitate FI's cleavage and inactivation of the central molecule of the AP, C3b. For personalised treatment, sensitive assays are required to define the functional significance of individual AP genetic variants. Generation of recombinant FI for functional analysis has thus far been constrained by incomplete processing resulting in a preparation of active and inactive protein. Using an internal ribosomal entry site (IRES)-Furin-CFI expression vector, fully processed FI was generated with activity equivalent to serum purified FI. By generating FI with an inactivated serine protease domain (S525A FI), a real-time surface plasmon resonance assay of C3b:FH:FI complex formation for characterising variants in CFH and CFI was developed and correlated well with standard assays. Using these methods, we further demonstrate that patient-associated rare genetic variants lacking enzymatic activity (e.g. CFI I340T) may competitively inhibit the wild-type FI protein. The dominant negative effect identified in inactive factor I variants could impact on the pharmacological replacement of FI currently being investigated for the treatment of dry AMD.
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Affiliation(s)
- Thomas M. Hallam
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Thomas E. Cox
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Kate Smith-Jackson
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Vicky Brocklebank
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - April J. Baral
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Nikolaos Tzoumas
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - David H. Steel
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,Sunderland Eye Infirmary, Sunderland, United Kingdom,Biosciences Institute, Newcastle University, International Centre for Life, Newcastle upon Tyne, United Kingdom
| | - Edwin K. S. Wong
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Victoria G. Shuttleworth
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Andrew J. Lotery
- Clinical and Experimental Sciences, Faculty of Medicine, Southampton General Hospital, University of Southampton, Southampton, United Kingdom
| | - Claire L. Harris
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Kevin J. Marchbank
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - David Kavanagh
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom,National Renal Complement Therapeutics Centre, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom,National Institute for Health and Care Research (NIHR) Newcastle Biomedical Research Centre, Biomedical Research Building, Newcastle upon Tyne, United Kingdom,*Correspondence: David Kavanagh,
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Saleem M, Shaikh S, Hu Z, Pozzi N, Java A. Post-Transplant Thrombotic Microangiopathy due to a Pathogenic Mutation in Complement Factor I in a Patient With Membranous Nephropathy: Case Report and Review of Literature. Front Immunol 2022; 13:909503. [PMID: 35720299 PMCID: PMC9204634 DOI: 10.3389/fimmu.2022.909503] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/02/2022] [Indexed: 11/13/2022] Open
Abstract
Thrombotic microangiopathy (TMA) is characterized by microangiopathic hemolytic anemia, thrombocytopenia and organ injury occurring due to endothelial cell damage and microthrombi formation in small vessels. TMA is primary when a genetic or acquired defect is identified, as in atypical hemolytic uremic syndrome (aHUS) or secondary when occurring in the context of another disease process such as infection, autoimmune disease, malignancy or drugs. Differentiating between a primary complement-mediated process and one triggered by secondary factors is critical to initiate timely treatment but can be challenging for clinicians, especially after a kidney transplant due to presence of multiple confounding factors. Similarly, primary membranous nephropathy is an immune-mediated glomerular disease associated with circulating autoantibodies (directed against the M-type phospholipase A2 receptor (PLA2R) in 70% cases) while secondary membranous nephropathy is associated with infections, drugs, cancer, or other autoimmune diseases. Complement activation has also been proposed as a possible mechanism in the etiopathogenesis of primary membranous nephropathy; however, despite complement being a potentially common link, aHUS and primary membranous nephropathy have not been reported together. Herein we describe a case of aHUS due to a pathogenic mutation in complement factor I that developed after a kidney transplant in a patient with an underlying diagnosis of PLA2R antibody associated-membranous nephropathy. We highlight how a systematic and comprehensive analysis helped to define the etiology of aHUS, establish mechanism of disease, and facilitated timely treatment with eculizumab that led to recovery of his kidney function. Nonetheless, ongoing anti-complement therapy did not prevent recurrence of membranous nephropathy in the allograft. To our knowledge, this is the first report of a patient with primary membranous nephropathy and aHUS after a kidney transplant.
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Affiliation(s)
- Maryam Saleem
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Sana Shaikh
- Division of Nephrology, Department of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Zheng Hu
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Nicola Pozzi
- Department of Biochemistry and Molecular Biology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, MO, United States
| | - Anuja Java
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
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Java A, Pozzi N, Schroeder MC, Hu Z, Huan T, Seddon JM, Atkinson J. Functional analysis of rare genetic variants in complement factor I in advanced age-related macular degeneration. Hum Mol Genet 2022; 31:3683-3693. [PMID: 35531992 PMCID: PMC9616575 DOI: 10.1093/hmg/ddac103] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 04/07/2022] [Accepted: 04/28/2022] [Indexed: 11/14/2022] Open
Abstract
Factor I (FI) is a serine protease inhibitor of the complement system. Heterozygous rare genetic variants in complement factor I (CFI) are associated with advanced age-related macular degeneration (AMD). The clinical impact of these variants is unknown since a majority have not been functionally characterized and are classified as 'variants of uncertain significance' (VUS). This study assessed the functional significance of VUS in CFI. Our previous cross-sectional study using a serum-based assay demonstrated that CFI variants in advanced AMD can be categorized into three types. Type 1 variants cause a quantitative deficiency of FI. Type 2 variants demonstrate a qualitative deficiency. However, Type 3 variants consist of VUS that are less dysfunctional than Types 1 and 2 but are not as biologically active as wild type (WT). In this study, we employed site-directed mutagenesis followed by expression of the recombinant variant and a comprehensive set of functional assays to characterize nine Type 3 variants that were identified in 37 individuals. Our studies establish that the expression of the recombinant protein compared with WT is reduced for R202I, Q217H, S221Y and G263V. Further, G362A and N536K, albeit expressed normally, have significantly less cofactor activity. These results led to re-categorization of CFI variants R202I, Q217H, S221Y and G263V as Type 1 variants and to reclassification of N536K and G362A as Type 2. The variants K441R, Q462H and I492L showed no functional defect and remained as Type 3. This study highlights the utility of an in-depth biochemical analysis in defining the pathologic and clinical implications of complement variants underlying AMD.
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Affiliation(s)
- Anuja Java
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Nicola Pozzi
- Department of Biochemistry and Molecular Biology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Molly C Schroeder
- Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Zheng Hu
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Tianxiao Huan
- Department of Ophthalmology and Visual Sciences, University of Massachusetts Chan Medical School, Worcester, MA 01655, USA
| | | | - John Atkinson
- To whom correspondence should be addressed at: Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA. Tel: +1 3143628391; Fax: +1 3143621366;
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8
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Ren Z, Perkins SJ, Love-Gregory L, Atkinson JP, Java A. Clinicopathologic Implications of Complement Genetic Variants in Kidney Transplantation. Front Med (Lausanne) 2021; 8:775280. [PMID: 34912830 PMCID: PMC8666976 DOI: 10.3389/fmed.2021.775280] [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: 09/13/2021] [Accepted: 11/08/2021] [Indexed: 12/23/2022] Open
Abstract
Genetic testing has uncovered rare variants in complement proteins associated with thrombotic microangiopathy (TMA) and C3 glomerulopathy (C3G). Approximately 50% are classified as variants of uncertain significance (VUS). Clinical risk assessment of patients carrying a VUS remains challenging primarily due to a lack of functional information, especially in the context of multiple confounding factors in the setting of kidney transplantation. Our objective was to evaluate the clinicopathologic significance of genetic variants in TMA and C3G in a kidney transplant cohort. We used whole exome next-generation sequencing to analyze complement genes in 76 patients, comprising 60 patients with a TMA and 16 with C3G. Ten variants in complement factor H (CFH) were identified; of these, four were known to be pathogenic, one was likely benign and five were classified as a VUS (I372V, I453L, G918E, T956M, L1207I). Each VUS was subjected to a structural analysis and was recombinantly produced; if expressed, its function was then characterized relative to the wild-type (WT) protein. Our data indicate that I372V, I453L, and G918E were deleterious while T956M and L1207I demonstrated normal functional activity. Four common polymorphisms in CFH (E936D, N1050Y, I1059T, Q1143E) were also characterized. We also assessed a family with a pathogenic variant in membrane cofactor protein (MCP) in addition to CFH with a unique clinical presentation featuring valvular dysfunction. Our analyses helped to determine disease etiology and defined the recurrence risk after kidney transplant, thereby facilitating clinical decision making for our patients. This work further illustrates the limitations of the prediction models and highlights the importance of conducting functional analysis of genetic variants particularly in a complex clinicopathologic scenario such as kidney transplantation.
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Affiliation(s)
- Zhen Ren
- Division of Allergy and Immunology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Stephen J. Perkins
- Department of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom
| | - Latisha Love-Gregory
- Genomic and Pathology Services, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, United States
| | - John P. Atkinson
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Anuja Java
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States
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de Jong S, Volokhina EB, de Breuk A, Nilsson SC, de Jong EK, van der Kar NCAJ, Bakker B, Hoyng CB, van den Heuvel LP, Blom AM, den Hollander AI. Effect of rare coding variants in the CFI gene on Factor I expression levels. Hum Mol Genet 2021; 29:2313-2324. [PMID: 32510551 PMCID: PMC7424754 DOI: 10.1093/hmg/ddaa114] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 05/29/2020] [Accepted: 06/03/2020] [Indexed: 12/25/2022] Open
Abstract
Factor I (FI) is one of the main inhibitors of complement activity, and numerous rare coding variants have been reported in patients with age-related macular degeneration, atypical hemolytic uremic syndrome and C3 glomerulopathy. Since many of these variants are of unknown clinical significance, this study aimed to determine the effect of rare coding variants in the complement factor I (CFI) gene on FI expression. We measured FI levels in plasma samples of carriers of rare coding variants and in vitro in the supernatants of epithelial cells expressing recombinant FI. FI levels were measured in 177 plasma samples of 155 individuals, carrying 24 different rare coding variants in CFI. In carriers of the variants p.Gly119Arg, p.Leu131Arg, p.Gly188Ala and c.772G>A (r.685_773del), significantly reduced FI plasma levels were detected. Furthermore, recombinant FI expression levels were determined for 126 rare coding variants. Of these variants 68 (54%) resulted in significantly reduced FI expression in supernatant compared to wildtype (WT). The recombinant protein expression levels correlated significantly with the FI level in plasma of carriers of CFI variants. In this study, we performed the most comprehensive FI expression level analysis of rare coding variants in CFI to date. More than half of CFI variants lead to reduced FI expression, which might impair complement regulation in vivo. Our study will aid the interpretation of rare coding CFI variants identified in clinical practice, which is in particular important in light of patient inclusion in ongoing clinical trials for CFI gene supplementation in AMD.
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Affiliation(s)
- Sarah de Jong
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Elena B Volokhina
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands.,Amalia Children's Hospital, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands.,Department of Laboratory Medicine, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Anita de Breuk
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Sara C Nilsson
- Department of Translational Medicine, Lund University, 21428 Malmö, Sweden
| | - Eiko K de Jong
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Nicole C A J van der Kar
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands.,Amalia Children's Hospital, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Bjorn Bakker
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Carel B Hoyng
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Lambert P van den Heuvel
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands.,Department of Laboratory Medicine, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Anna M Blom
- Department of Translational Medicine, Lund University, 21428 Malmö, Sweden
| | - Anneke I den Hollander
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
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10
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de Jong S, Gagliardi G, Garanto A, de Breuk A, Lechanteur YTE, Katti S, van den Heuvel LP, Volokhina EB, den Hollander AI. Implications of genetic variation in the complement system in age-related macular degeneration. Prog Retin Eye Res 2021; 84:100952. [PMID: 33610747 DOI: 10.1016/j.preteyeres.2021.100952] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 02/08/2021] [Accepted: 02/11/2021] [Indexed: 12/23/2022]
Abstract
Age-related macular degeneration (AMD) is the main cause of vision loss among the elderly in the Western world. While AMD is a multifactorial disease, the complement system was identified as one of the main pathways contributing to disease risk. The strong link between the complement system and AMD was demonstrated by genetic associations, and by elevated complement activation in local eye tissue and in the systemic circulation of AMD patients. Several complement inhibitors have been and are being explored in clinical trials, but thus far with limited success, leaving the majority of AMD patients without treatment options to date. This indicates that there is still a gap of knowledge regarding the functional implications of the complement system in AMD pathogenesis and how to bring these towards clinical translation. Many different experimental set-ups and disease models have been used to study complement activation in vivo and in vitro, and recently emerging patient-derived induced pluripotent stem cells and genome-editing techniques open new opportunities to study AMD disease mechanisms and test new therapeutic strategies in the future. In this review we provide an extensive overview of methods employed to understand the molecular processes of complement activation in AMD pathogenesis. We discuss the findings, advantages and challenges of each approach and conclude with an outlook on how recent, exciting developments can fill in current knowledge gaps and can aid in the development of effective complement-targeting therapeutic strategies in AMD.
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Affiliation(s)
- Sarah de Jong
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands
| | - Giuliana Gagliardi
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands
| | - Alejandro Garanto
- Department of Human Genetics, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands; Department of Pediatrics, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands; Amalia Children's Hospital, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands
| | - Anita de Breuk
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands
| | - Yara T E Lechanteur
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands
| | - Suresh Katti
- Gemini Therapeutics Inc., Cambridge, MA, 02139, USA
| | - Lambert P van den Heuvel
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands; Amalia Children's Hospital, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands; Department of Laboratory Medicine, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands
| | - Elena B Volokhina
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands; Amalia Children's Hospital, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands; Department of Laboratory Medicine, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands
| | - Anneke I den Hollander
- Department of Ophthalmology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands; Department of Human Genetics, Radboud University Medical Center, 6525, GA, Nijmegen, the Netherlands.
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11
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Java A, Baciu P, Widjajahakim R, Sung YJ, Yang J, Kavanagh D, Atkinson J, Seddon J. Functional Analysis of Rare Genetic Variants in Complement Factor I ( CFI) using a Serum-Based Assay in Advanced Age-related Macular Degeneration. Transl Vis Sci Technol 2020; 9:37. [PMID: 32908800 PMCID: PMC7453046 DOI: 10.1167/tvst.9.9.37] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 07/26/2020] [Indexed: 11/24/2022] Open
Abstract
Purpose Factor I (FI) is a serine protease regulator of the complement system. Genetic variants in CFI are associated with advanced age-related macular degeneration (AAMD). However, the clinical and functional impact of these variants is unknown. This study assessed the functional significance of rare CFI variants using a serum-based assay. Methods Carriers of rare variants with (n = 78) and without AAMD (n = 28), and noncarriers with (n = 49) and without AMD (n = 44) were evaluated. Function of FI was determined by measuring the proteolytic cleavage of C3b to iC3b, using the cofactor protein, Factor H. Results CFI variants were categorized into three groups based on antigenic and functional assessments. Type 1 variants (n = 18) in 35 patients with AAMD demonstrated low serum FI levels and a corresponding decrease in FI function. Type 2 variants (n = 6) in 7 individuals demonstrated normal serum FI antigenic levels but reduced degradation of C3b to iC3b. Type 3 variants (n = 15) in 64 individuals demonstrated normal antigenic levels and degradation of C3b to iC3b. However, iC3b generation was low when measured per unit of FI. Thus most rare CFI variants demonstrate either low antigenic levels (type 1) or normal levels but reduced function (types 2 or 3). Conclusions Results provide for the first time a comprehensive functional assessment in serum of CFI rare genetic variants and further establish FI's key role in the pathogenesis of AAMD. Translational Relevance Stratifying patients in the clinic with a rare CFI variant will facilitate screening and targeting patients most likely to benefit from complement therapies.
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Affiliation(s)
- Anuja Java
- Divisions of Nephrology and Rheumatology, Department of Medicine, Washington University, St. Louis, MO, USA
| | | | - Rafael Widjajahakim
- Department of Ophthalmology and Visual Sciences, University of Massachusetts School of Medicine, Worcester, MA, USA
| | - Yun Ju Sung
- Department of Psychiatry and Division of Biostatistics Washington University School of Medicine in St. Louis, MO, USA
| | | | - David Kavanagh
- National Renal Complement Therapeutics Centre, Newcastle University, Newcastle upon Tyne, UK
| | - John Atkinson
- Divisions of Nephrology and Rheumatology, Department of Medicine, Washington University, St. Louis, MO, USA
| | - Johanna Seddon
- Department of Ophthalmology and Visual Sciences, University of Massachusetts School of Medicine, Worcester, MA, USA
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12
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Java A. Peri- and Post-operative Evaluation and Management of Atypical Hemolytic Uremic Syndrome (aHUS) in Kidney Transplantation. Adv Chronic Kidney Dis 2020; 27:128-137. [PMID: 32553245 DOI: 10.1053/j.ackd.2019.11.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/25/2019] [Accepted: 11/25/2019] [Indexed: 01/05/2023]
Abstract
Atypical hemolytic uremic syndrome (aHUS) is a severe thrombotic microangiopathy characterized by over-activation of the alternative complement pathway. The etiology of the dysregulated complement system is commonly a genetic variant in one or more complement proteins as identified in ∼ 60%-70% patients. The risk of recurrence after a kidney transplantation is high and depends on the underlying complement abnormality. For a long time, kidney transplantation was contraindicated in these patients because of the high rate of recurrence and subsequent allograft loss. Over the past decade, advancements in the understanding of etiopathogenesis of aHUS and approval of the anti-complement drug, eculizumab, have allowed for successful kidney transplantation in these patients. All patients with ESRD due to aHUS should undergo screening for complement genetic variants. Patients in whom a genetic variant is not identified or in whom a genetic variant of uncertain significance is identified should undergo further testing to determine etiology of disease. This review aims to shed light on the diagnostic and therapeutic considerations in patients with aHUS preceding and following kidney transplantation.
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