CFHR1 Research Articles

Shared germline genomic variants in two patients with double primary gastrointestinal stromal tumours (GISTs)

BackgroundGastrointestinal stromal tumours (GISTs) are prevalent mesenchymal tumours of the gastrointestinal tract, commonly exhibiting structural variations in KIT and PDGFRA genes. While the mutational profiling of somatic tumours is well...

Cfhr1 gene deficiency exacerbates Staphylococcus aureus-induced sepsis and acute lung injury through complement alternative pathway hyperactivation

ObjectiveTo explore the role of excessive activation of the complement alternative pathway (AP) in acute lung injury (ALI) and sepsis induced by Staphylococcus aureus. Subsequently, we aimed to define the effects of Cfhr gene deletion on Factor H expression, AP activation, and the development of sepsis-induced ALI. MethodsA sepsis-induced ALI model was established in Cfhr1-knockout mice by tail vein injection of S. aureus. Sepsis scores, bacterial load in lungs, and cytokine and complement factor levels in blood and lung tissues were evaluated at 6, 12, and 24 h after model establishment. Real-time quantitative PCR and RNA sequencing (RNA-seq) were employed to assess the expression of complement pathway-associated molecules and identify differentially expressed genes (DEGs) related to immune responses. ResultsCompared to wild-type mice, Cfhr1-knockout mice exhibited significantly increased C3a formation in lung tissues following S. aureus infection, indicating enhanced terminal complement pathway activation. Notably, these mice also had higher bacterial colony counts in the lungs, suggesting impaired S. aureus clearance. Transcriptome analysis provided further insights into the impact of Cfhr1 deletion on biological processes and signalling pathways involved in immune response regulation. ConclusionCfhr1 deletion leads to excessive AP activation, exacerbating S. aureus-induced sepsis and ALI.

Clinical characteristics and genetic profile of complement system in renal thrombotic microangiopathy in patients with severe forms of arterial hypertension

The spectrum of diseases characterized by the development of renal thrombotic microangiopathy (TMA) encompasses the malignant hypertension (MHT). TMA in MHT has conventionally been regarded as a variation of secondary TMA, the treatment of which is restricted to the stabilization of blood pressure levels, a measure that frequently fails to prevent the rapid progression to end-stage renal disease in patients. Nevertheless, there exists a rationale to suggest that, in certain instances, endothelial damage in MHT might be rooted in the dysregulation of the complement system (CS), thereby presenting potential opportunities for the implementation of complement-blocking therapy. To study clinical manifestations and genetic profile of CS in patients with morphologically confirmed renal TMA combined with severe AH. 28 patients with morphologically verified renal TMA and severe AH were enrolled to the study. Patients with signs of microangiopathic hemolysis and thrombocytopenia were not included in the study due to possible compliance with the criteria for atypical hemolytic uremic syndrome (aHUS). The prevalence of rare genetic defects (GD) of the CS was assessed by molecular genetic analysis (search for mutations in the clinically significant part of the human genome - exome) by next-generation sequencing technology (NGS). GD of CS were detected in a quarter of patients. Rare genetic variants classified as "likely pathogenic" including defects in CFI, C3, CD46, CFHR4, CFHR5 genes were detected in five cases. Two patients were found to have chromosomal deletions containing CFH-related proteins genes (CFHR1, CFHR3). Rare variants of CS genes linked to aHUS were found in 25% of patients with renal TMA, the genesis of which was originally thought to be secondary and attributed to MHT, with partial or complete absence of hematological manifestations of microangiopathic pathology. The key to confirming TMA associated with MHT, particularly in the absence of microangiopathic hemolysis and thrombocytopenia, elucidating its nature, and potentially effective complement-blocking therapy in patients with GD of CS, appears to be a genetic study of CS combined with a morphological study of a renal biopsy.

Whole Genome Sequencing Identifies Novel Common and Low-Frequency Variants Associated With Age-Related Macular Degeneration.

To identify associations of common, low-frequency, and rare variants with advanced age-related macular degeneration (AMD) using whole genome sequencing (WGS). WGS data were obtained for 2123 advanced AMD patients (participants of clinical trials for advanced AMD) and 2704 controls (participants of clinical trials for asthma [N = 2518] and Alzheimer's disease [N = 186]), and joint genotype calling was performed, followed by quality control of the dataset. Single variant association analyses were performed for all identified common, low-frequency, and rare variants. Gene-based tests were executed for rare and low-frequency variants using SKAT-O and three groups of variants based on putative impact information: (1) all variants, (2) modifier impact variants, and (3) high- and moderate-impact variants. To ascertain independence of the identified associations from previously reported AMD and asthma loci, conditional analyses were performed. Previously identified AMD variants at the CFH, ARMS2/HTRA1, APOE, and C3 loci were associated with AMD at a genome-wide significance level. We identified new single variant associations for common variants near the PARK7 gene and in the long non-coding RNA AC103876.1, and for a rare variant near the TENM3 gene. In addition, gene-based association analyses identified a burden of modifier variants in eight intergenic and gene-spanning regions and of high- and moderate-impact variants in the C3, CFHR5, SLC16A8, and CFI genes. We describe the largest WGS study in AMD to date. We confirmed previously identified associations and identified several novel associations that are worth exploring in further follow-up studies.

Clinical research advances of CFHR5 nephropathy: a recent review.

CFHR5 nephropathy is a type of clinical C3 glomerulopathy, which is a monogenic genetic disease caused by the internal replication of CFHR5 gene, a protein related to the complement regulatory factor H family. The disease seems to be prevalent only in people of Greek Cypriot descent. Because of the special variation of the internal replication of exon 2 and exon 3 of CFHR5 protein in the occurrence of disease, it has had a serious impact on local residents. At present, the mechanism of glomerular damage caused by CFHR5 protein mutations is still unclear. The purpose of this article is to review the clinical research advances of this disease in the past 10 years, including the study of mutant genes, the analysis of mutant proteins and the role of alternative pathways in glomerular injury. It covers the progress in diagnosis and clinical treatment of the disease and looks forward to the future development prospects of its treatment. It is hoped that the recent results will be summarized for the follow-up in-depth study of CFHR5 nephropathy.

The absence of CFHR3 and CFHR1 genes from the T2T-CHM13 assembly can limit the molecular diagnosis of complement-related diseases.

The absence of CFHR3 and CFHR1 genes from the T2T-CHM13 assembly can limit the molecular diagnosis of complement-related diseases.

Targeted Genotyping of MIS-C Patients Reveals a Potential Alternative Pathway Mediated Complement Dysregulation during COVID-19 Infection.

Complement dysregulation has been documented in adults with COVID-19 and implicated in relevant pediatric inflammatory responses against SARS-CoV-2. We propose that signatures of complement missense coding SNPs associated with dysregulation could also be identified in children with multisystem inflammatory syndrome (MIS-C). We investigated 71 pediatric patients with RT-PCR validated SARS-CoV-2 hospitalized in pediatric COVID-19 care units (November 2020–March 2021) in three major groups. Seven (7) patients suffered from MIS-C (MIS-C group), 32 suffered from COVID-19 and were hospitalized (admitted group), whereas 32 suffered from COVID-19, but were sent home. All patients survived and were genotyped for variations in the C3, C5, CFB, CFD, CFH, CFHR1, CFI, CD46, CD55, MASP1, MASP2, MBL2, COLEC11, FCN1, and FCN3 genes. Upon evaluation of the missense coding SNP distribution patterns along the three study groups, we noticed similarities, but also considerably increased frequencies of the alternative pathway (AP) associated with SNPs rs12614 CFB, rs1061170, and rs1065489 CFH in the MIS-C patients. Our analysis suggests that the corresponding substitutions potentially reduce the C3b-inactivation efficiency and promote slower and weaker AP C3bBb pre-convertase assembly on virions. Under these circumstances, the complement AP opsonization capacity may be impaired, leading to compromised immune clearance and systemic inflammation in the MIS-C syndrome.

Clinical features of children with anti-CFH autoantibody-associated hemolytic uremic syndrome: a report of 8 cases

Objective To explore the clinical characteristics, treatment protocol and prognosis of children with anti-complement factor H (CFH) autoantibody (Ab)-associated hemolytic uremic syndrome (HUS). Methods Clinical data of 8 patients with anti-CFH Ab-associated HUS who were admitted to Shandong Provincial Hospital from January 2011 to December 2020 were collected retrospectively. Results The age at disease onset ranged between 5.83 and 13.5 years, with a male: female ratio of 1.67:1. The time of onset was distributed from May to June and November to December. Digestive and upper respiratory tract infections were common prodromal infections. Positivity for anti-CFH Ab and reduced C3 levels were observed among all patients. Heterozygous mutation of the CHFR5 gene (c.669del A) and homozygous loss of the CFHR1 gene [loss2(EXON:2-6)] were found in two patients. All patients received early treatment with plasma exchange and corticosteroid therapy. Six patients were given immunosuppressive agents (cyclophosphamide and/or mycophenolate mofetil) for persistent proteinuria. The follow-up period was 12–114 months. Four of 8 patients achieved complete remission, 3 achieved partial remission, and 1 died. Relapse occurred in two patients. Conclusion Children with anti-CFH Ab-associated HUS were mainly school-aged and predominantly male, with onset times of summer and winter. Digestive and upper respiratory tract infections were common prodromal infections. Plasma exchange combined with methylprednisolone pulse therapy in the acute phase and cyclophosphamide or mycophenolate mofetil treatment for maintenance can be utilized in children with anti-CFH Ab-associated HUS if eculizumab is not available.

Hepatic transcriptome analysis identifies genes, polymorphisms and pathways involved in the fatty acids metabolism in sheep.

Fatty acids (FA) in ruminants, especially unsaturated FA (USFA) have important impact in meat quality, nutritional value, and flavour quality of meat, and on consumer's health. Identification of the genetic factors controlling the FA composition and metabolism is pivotal to select sheep that produce higher USFA and lower saturated (SFA) for the benefit of sheep industry and consumers. Therefore, this study was aimed to investigate the transcriptome profiling in the liver tissues collected from sheep with divergent USFA content in longissimus muscle using RNA deep-sequencing. From sheep (n = 100) population, liver tissues with higher (n = 3) and lower (n = 3) USFA content were analysed using Illumina HiSeq 2500. The total number of reads produced for each liver sample were ranged from 21.28 to 28.51 million with a median of 23.90 million. Approximately, 198 genes were differentially regulated with significance level of p-adjusted value <0.05. Among them, 100 genes were up-regulated, and 98 were down-regulated (p<0.01, FC>1.5) in the higher USFA group. A large proportion of key genes involved in FA biosynthesis, adipogenesis, fat deposition, and lipid metabolism were identified, such as APOA5, SLC25A30, GFPT1, LEPR, TGFBR2, FABP7, GSTCD, and CYP17A. Pathway analysis revealed that glycosaminoglycan biosynthesis- keratan sulfate, adipokine signaling, galactose metabolism, endocrine and other factors-regulating calcium metabolism, mineral metabolism, and PPAR signaling pathway were playing important regulatory roles in FA metabolism. Importantly, polymorphism and association analyses showed that mutation in APOA5, CFHR5, TGFBR2 and LEPR genes could be potential markers for the FA composition in sheep. These polymorphisms and transcriptome networks controlling the FA variation could be used as genetic markers for FA composition-related traits improvement. However, functional validation is required to confirm the effect of these SNPs in other sheep population in order to incorporate them in the sheep breeding program.

High prevalence of CFHR deletions in Indian women with pregnancy-associated hemolytic uremic syndrome.

Pregnancy-associated hemolytic uremic syndrome (P-aHUS) is an important cause of peripartum acute kidney injury. Studies from Europe have described mutations in complement regulator genes, and data in Indian patients is scarce. Hence this study used multiplex ligation-dependent probe amplification (MLPA) to identify variants in complement genes in P-aHUS patients. We present 17 patients of P-aHUS who were investigated for complement protein levels and genetic analysis with MLPA for complement genes. Plasma exchange therapy was offered to all patients presenting in acute phase. Mean age 26.74 (3.36) years with 15/17 delivered by caesarean section. Eleven patients received early (within 7 days) plasma exchange, three were dialysis-dependent at 3months and seven were dialysis-free. Only one of the three patients receiving late (after 7 days) plasma exchange was dialysis-free. MLPA showed that 11 patients had heterozygous deletions of exons 3, 5, 6 of CFHR1 and upstream region of exons 1, 2, 3, 6 and intron 4 of CFHR3 gene while four patients had homozygous deletions at the same loci. Two patients had no MLPA-detectable variations. This study reports a high proportion of deletions of exons of CFHR1 & CFHR3 genes in Indian P-aHUS patients detectable by MLPA by copy number variations. This needs confirmation in large multicentre studies. Plasma exchange can be an effective therapy in the non-availability of Eculizumab.

Factor H-related protein 1 (FHR-1) is associated with atherosclerotic cardiovascular disease

Atherosclerotic cardiovascular disease (ACVD) is a lipid-driven inflammatory disease and one of the leading causes of death worldwide. Lipid deposits in the arterial wall lead to the formation of plaques that involve lipid oxidation, cellular necrosis, and complement activation, resulting in inflammation and thrombosis. The present study found that homozygous deletion of the CFHR1 gene, which encodes the plasma complement protein factor H-related protein 1 (FHR-1), was protective in two cohorts of patients with ACVD, suggesting that FHR-1 accelerates inflammation and exacerbates the disease. To test this hypothesis, FHR-1 was isolated from human plasma and was found to circulate on extracellular vesicles and to be deposited in atherosclerotic plaques. Surface-bound FHR-1 induced the expression of pro-inflammatory cytokines and tissue factor in both monocytes and neutrophils. Notably, plasma concentrations of FHR-1, but not of factor H, were significantly (p < 0.001) elevated in patients with ACVD, and correlated with the expression of the inflammation markers C-reactive protein, apolipoprotein serum amyloid protein A, and neopterin. FHR-1 expression also significantly correlated with plasma concentrations of low-density lipoprotein (LDL) (p < 0.0001) but not high-density lipoprotein (HDL). Taken together, these findings suggest that FHR-1 is associated with ACVD.

Mutations in the Alternative Complement Pathway in Multiple Myeloma Patients with Carfilzomib-Induced Thrombotic Microangiopathy

IntroductionVascular endothelial injury related to treatment with proteasome inhibitors (PI) has been previously described. Carfilzomib is an irreversible PI and has been associated with cardiovascular toxicity, suggesting increased risk of endothelial injury. Thrombotic microangiopathy (TMA) has been described in multiple myeloma (MM) patients receiving PIs; more often with carfilzomib. In the pediatric transplant population, increased risk of TMA was related to heterozygous mutation in the alternative complement pathway. The homozygous deletions enable uncontrolled complement activation and was found three times more frequently in TMA population. We hypothesized that MM patients with complement mutation are at increased risk of PI-related TMA.Materials and MethodsWe identified ten cases of renal TMA in MM patients receiving carfilzomib from two medical institutions in Greece and in the United States. TMA was diagnosed based on either renal biopsy or acute kidney injury, new-onset anemia, thrombocytopenia and increased LDH in the absence of disease progression. We performed targeted sequencing of the twelve genes implicated in TMA: CFH, CFI, MCP, CFB, CFHR5, C3, THBD, DGKE, PLG, ADAMTS13, MMACHC and G6PD genes. Multiplex Ligation-Dependent Probe Amplification (MLPA) was performed for the analysis of the CFH-CFHR5 region.ResultsPatient characteristics and laboratory values at TMA diagnosis are presented in Table 1. The median age of patients was 68 years (range, 47-73), with slight male predominance (60%). Median laboratory values at diagnosis included hemoglobin 9.35 g/dL, platelet count 26,500 x 10 6/L, LDH 356,5 U/L and creatinine 2.25 mg/dL. Patients were treated with carfilzomib doses ranging 20-70 mg/m 2. Regimens included carfilzomib-dexamethasone (Kd, 7 patients), carfilzomib-lenalidomide-dexamethasone (KRd, 1 patient), carfilzomib-pomalidomide-dexamethasone (KPd, 1 patient), and carfilzomib-daratumumab-dexamethasone (DaraKd, 1 patient). All patients had previously received at least one line of therapy and seven patients had previously undergone autologous stem cell transplant (ASCT), 1-12 years prior to TMA diagnosis. The median time between carfilzomib initiation and TMA diagnosis was 4.5 months (range, 1-60 months). Diagnosis was confirmed with renal biopsy in four cases. Carfilzomib was discontinued in all patients and five patients were treated with plasma exchange (PLEX) while one patient received eculizumab. Seven patients demonstrated clinical improvement and resolution of TMA at 1 year after discontinuation of carfilzomib. Two patients progressed to end stage renal disease (ESRD) requiring intermittent hemodialysis, and one patient developed multiorgan failure. Results of genetic panel are shown in Table 2. Deletions of the CFHR3-CFHR5 region were present in seven cases (70%): two patients carrying a homozygous deletion of CFHR3-CFHR1, four patients with a heterozygous deletion of CFHR3-CFHR1, and one patient with heterozygous deletion of CFHR1-CFHR4. Direct gene sequencing revealed identifiable mutations in CD46 (MCP) and CFHR5 in two distinct patients. The functional correlation and clinical significance are yet to be investigated.ConclusionsIn our cohort of ten patients of carfilzomib-induced TMA, deletions of CFHR3-CFHR5 occurred frequently (70%). In the setting of carfilzomib use, heterozygous CFHR3-CFHR1 deletion may represent a risk factor for the development of TMA. Our data set the bases for larger studies assessing complement mutation as a predisposing factor for PI-induced TMA. [Display omitted] DisclosuresKastritis: Amgen: Consultancy, Honoraria, Research Funding; Genesis Pharma: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Takeda: Honoraria; Pfizer: Consultancy, Honoraria, Research Funding. Dimopoulos: Janssen: Honoraria; BMS: Honoraria; Takeda: Honoraria; Beigene: Honoraria; Amgen: Honoraria. Richardson: AbbVie: Consultancy; Secura Bio: Consultancy; Sanofi: Consultancy; GlaxoSmithKline: Consultancy; Karyopharm: Consultancy, Research Funding; Regeneron: Consultancy; AstraZeneca: Consultancy; Oncopeptides: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Janssen: Consultancy; Celgene/BMS: Consultancy, Research Funding; Protocol Intelligence: Consultancy; Jazz Pharmaceuticals: Consultancy, Research Funding. Bianchi: Jacob D. Fuchsberg Law Firm: Consultancy; MJH: Honoraria; Karyopharm: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria.

FHR-5 Serum Levels and CFHR5 Genetic Variations in Patients With Immune Complex-Mediated Membranoproliferative Glomerulonephritis and C3-Glomerulopathy.

BackgroundFactor H-related protein 5 (FHR-5) is a member of the complement Factor H protein family. Due to the homology to Factor H, the main complement regulator of the alternative pathway, it may also be implicated in the pathomechanism of kidney diseases where Factor H and alternative pathway dysregulation play a role. Here, we report the first observational study on CFHR5 variations along with serum FHR-5 levels in immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G) patients together with the clinical, genetic, complement, and follow-up data.MethodsA total of 120 patients with a histologically proven diagnosis of IC-MPGN/C3G were enrolled in the study. FHR-5 serum levels were measured in ELISA, the CFHR5 gene was analyzed by Sanger sequencing, and selected variants were studied as recombinant proteins in ELISA and surface plasmon resonance (SPR).ResultsEight exonic CFHR5 variations in 14 patients (12.6%) were observed. Serum FHR-5 levels were lower in patients compared to controls. Low serum FHR-5 concentration at presentation associated with better renal survival during the follow-up period; furthermore, it showed clear association with signs of complement overactivation and clinically meaningful clusters.ConclusionsOur observations raise the possibility that the FHR-5 protein plays a fine-tuning role in the pathogenesis of IC-MPGN/C3G.

MO275RARE VARIANTS OF COMPLEMENT FACTOR H AND THROMBOMODULIN ARE OVER-REPRESENTED IN A COHORT OF SEVERE IGA NEPHROPATHY PATIENTS

Abstract Background and Aims IgA nephropathy is the most frequent primary glomerulonephritis leading to end stage renal disease (ESRD) in about 30% of cases within 20 years after diagnosis. Complement activation through alternative and lectin pathways has been described to impact the pathogeny of the disease. We hypothesized in this study that rare variants of alternative pathways regulatory genes could be overrepresented and could play a role at initiating the disease and could harm the prognosis of IgA Nephropathy. Method Patients with biopsy proven IgA nephropathy with markers of severity comprising an evolution through ESRD and/or a proteinuria &amp;gt;0.5g/day with available DNA sample were included. All coding sequences of CFH, CFI, MCP, C3, Factor B THBD and CFHR5 genes were analyzed by next generation sequencing. We defined a variant as rare when its minor allele frequency was below 0.1% in the general population. Frequencies were compared to a French volonteers cohort (n=80) and a European large cohort (n=503) Results We screened 128 patients with IgA N, with following characteristics at diagnosis: median age 42.4 yo, proteinuria (median) 1.4g/day, hypertension 66%, median eGFR 48.7 mL/min/1.73m². The median follow-up was 99 months and 58% of patients progressed to ESRD. We identified rare variants with MAF&amp;lt;0.1% in 10.2 % (n=13) including 1 patient with two rare variants. The functional consequences of the 12 out the 14 variants are unknown. Two variants in CFH are located in function domains and are pathogenic. Patients with IgA N have high rates of rare variants in CFH (n=9/128 ; 7 %) versus normal controls (n=9/503 ; 1.8%) (p=0.004); Pathogenic Variants with minor allele frequency &amp;lt;0.1% in CFH were found in 2 IgA N (2 out of 128, 1.5%) versus 1 European controls (1 out of 503) In total, 11 % (14/128), 3.8 % (5/128) and 0.8 % (1/128) of the 128 patients were homozygous for the at-risk haplotype MCP ggaac, CFH tgtgt or both, respectively (versus 6.2 % (5/80), 3.8 % (3/80) and 0% in the controls) 6 patients carried the pathogenic variant in THDM gene p.Ala43Thr (6/128) versus 5 in 508 controls population (p=0.01). No difference in term of hypertension, proteinuria, eGFR, Oxford classification, vascular score at diagnosis was noticed between patients without any rare variant compared to patients with at least one rare variant. The progression through ESRD was not different between groups. Conclusion In this cohort of Caucasian IgA nephropathy patients, rare variants of CFH and THBD were found significantly overrepresented compared to a French and European control cohort. Rare variants of alternative pathway regulatory genes were not associated with particular severity or prognosis.

Association between thrombotic microangiopathy and activated alternative complement pathway in malignant nephrosclerosis.

Malignant nephrosclerosis, defined as renal microangiopathy in the setting of severe hypertension, remains a critical renal emergency leading to end-stage renal disease despite aggressive anti-hypertensive treatment. Recently, activation of the complement alternative pathway (AP) has been reported to play a prominent role in the pathogenesis of malignant nephrosclerosis. However, subsequent study failed to recapitulate the findings of genetic complement abnormalities in the disease. This study aimed to determine the presence of AP activation and genetic complement defects and establish their correlations to renal microangiopathy lesions, clinical features and prognosis in patients with malignant nephrosclerosis. Fifty patients with malignant hypertension and concomitant thrombotic microangiopathy (TMA) proven by renal biopsy were investigated; 25 cases of kidney donors who received zero-hour allograft biopsies were used as normal controls. Various renal TMA lesions in patients with malignant nephrosclerosis were reviewed and evaluated using a semi-quantitative scoring system. Deposition of C5b-9, C3a, C5a, C4d and mannose-binding lectin was assessed by immunohistochemistry. Co-localization of C5b-9 and CD34 was detected by confocal microscopy. Complement factor B (FB), factor P (FP; properdin), factor D (FD), factor H (FH), C3a and C5a levels were quantified by enzyme-linked immonosorbent assay in plasma and urine samples of patients with malignant nephrosclerosis and controls. Genetic abnormalities of complement components were analysed by whole-exome sequencing. Renal biopsies of malignant nephrosclerosis showed identical histopathological and ultrastructural features to atypical haemolytic uraemic syndrome. C5b-9, C3a and C5a deposits were found along the walls of arteries/arterioles and glomerular capillaries and localized in the endothelial cells. Elevated plasma and urinary levels of FB, FP, FD, C3a and C5a as well as decreased FH levels were observed in patients with malignant nephrosclerosis compared with normal controls. The urinary levels of complement AP components, but not the plasma levels, were correlated with renal functions, prognosis and active TMA lesions except for arteriolar thrombi. Finally, mutations of the MCP, CFB, CFH and CFHR5 genes were identified in 8 of 20 patients with malignant nephrosclerosis. Aberrant complement AP dysregulation was demonstrated and associated with the activity, severity and renal outcomes of malignant nephrosclerosis. This observation warrants screening for complement defects in patients with malignant nephrosclerosis for the potential use of complement regulators and also highlights the need for further investigation of the precise role of AP in the pathogenesis of the disease.

Factor H Autoantibodies and Complement-Mediated Diseases.

Factor H (FH), a member of the regulators-of-complement-activation (RCA) family of proteins, circulates in human plasma at concentrations of 180–420 mg/L where it controls the alternative pathway (AP) of complement in the fluid phase and on cell surfaces. When the regulatory function of FH is impaired, complement-mediated tissue injury and inflammation occur, leading to diseases such as atypical hemolytic uremic syndrome (a thrombotic microangiopathy or TMA), C3 glomerulopathy (C3G) and monoclonal gammopathy of renal significance (MGRS). A pathophysiological cause of compromised FH function is the development of autoantibodies to various domains of the FH protein. FH autoantibodies (FHAAs) are identified in 10.9% of patients with aHUS, 3.2% of patients with C3G, and rarely in patients with MGRS. The phenotypic variability of FHAA-mediated disease reflects both the complexity of FH and the epitope specificity of FHAA for select regions of the native protein. In this paper, we have characterized FHAA epitopes in a large cohort of patients diagnosed with TMA, C3G or MGRS. We explore the epitopes recognized by FHAAs in these diseases and the association of FHAAs with the genetic deletion of both copies of the CFHR1 gene to show how these disease phenotypes are associated with this diverse spectrum of autoantibodies.

Deficiency of Mouse FHR-1 Homolog, FHR-E, Accelerates Sepsis, and Acute Kidney Injury Through Enhancing the LPS-Induced Alternative Complement Pathway.

Alternative complement pathway (AP) plays an important role in the development of sepsis, which is life threatening. Deficiency of factor H-related protein 1 (FHR-1), which is a regulator of AP, has been considered as a susceptible factor for atypical hemolytic uremic syndrome (aHUS) and other types of nephropathy when an inducer such as infection exists. However, the underlying mechanism of the disease development is largely unknown. There is no report on CFHR1 gene knockout in any animal infection model and its function in vivo is still unclear. Here, a Cfhr1 knockout mouse was generated for investigating AP in sepsis and sepsis-induced acute kidney injury (AKI). We found that murine FHR-1 homolog (FHR-E) deficiency enhanced lipopolysaccharide (LPS)-induced AP activation both in vitro and in vivo and that Cfhr1 knockout mice exhibited more severe sepsis and AKI in response to LPS challenge. These results indicated that FHR-E deficiency promoted LPS-induced sepsis and AKI through AP over-activation, providing a mouse model for studying AP regulation and sepsis. This study revealed the function of FHR-E in vivo, which may further provide hints to the pathogenesis of FHR-1 deficiency-related diseases by enhancing LPS-induced AP activation.

MRNA expression disturbance of complement system related genes in acute arterial thrombotic and paroxysmal atrial fibrillation patients.

This study aimed to compare the characteristics of mRNA expression of genes in complement system between acute arterial thrombotic patients and paroxysmal atrial fibrillation (PAF) patients. Twenty acute myocardial infarction (AMI) patients and 20 PAF patients were assigned into the experiment groups, and 20 stable angina pectoris (SAP) patients were enrolled in the control group. When compared with the control group, mRNA expression of C1QA, C1QB, C1QC, C1R, CFP, C5, CR1, ITGAM, ITGAX, ITGB2, C5AR1, CD46, CD55 and CD59 genes was significantly upregulated, and CR2 gene significantly downregulated in the AMI group (P<0.05); while mRNA expression of CFD, MBL2, MASP2, C5, C6, C8B, C9, C5AR1, CR2, CFI, CFHR1, CD46, CD55, VTN and CD59 genes was significantly downregulated in PAF patients (P<0.05). Results of the comparison between the AMI and PAF group showed that mRNA expression of C1QA, C1QB, C1QC, C1R, CFB, CFD, CFP, MBL2, MASP2, C5, C6, C8B, C9, CR1, ITGAM, ITGAX, ITGB2, C5AR1, CFI, CFHR1, CD46, CD55, CLU, VTN and CD59 genes was significantly upregulated in the AMI group (P<0.05). Taken SAP patients as controls, the complement system is in a high-intensive disturbance with simultaneous activation and inhibition in AMI patients, indicating that the cascade response of complement system is disturbed, and then the membrane attack complex (MAC) cannot form finally. The mRNA expression of related genes in the complement system is under a status of downregulation in PAF patients, indicating that the functions of cascade response in the complement system decreased significantly in PAF patients, leading to significantly decreased MAC functions.

CFHR Gene Variations Provide Insights in the Pathogenesis of the Kidney Diseases Atypical Hemolytic Uremic Syndrome and C3 Glomerulopathy.

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.

Perplexing Etiology of Acute Retinal Necrosis in a Renal Transplant Recipient.

Atypical hemolytic uremic syndrome is a rare form of thrombotic microangiopathy caused by complement pathogenic variants. We describe a case of a 33-year-old woman who presented as rapidly progressing renal failure requiring dialysis and had anemia, microhematuria, low C3, normal C4 levels, and normal platelet count. Renal biopsy revealed arteriolar thrombotic microangiopathy and acute tubular injury. Patient was treated with plasma exchange and hemodialysis as required. This resulted in partial recovery at 1 month. Genetic workup by multiplex ligation-dependent probe amplification revealed a 1.5 times higher signal intensity on downstream region of CFH gene and 50% reduced intensity of exon 6 of CFHR1 gene, suggesting a gene conversion event, similar to those previously reported from Spain and Portugal.