Deletion Of CFHR3 Research Articles

A genome-wide association study identifies key modulators of complement factor H binding to malondialdehyde-epitopes

Genetic variants within complement factor H (CFH), a major alternative complement pathway regulator, are associated with the development of age-related macular degeneration (AMD) and other complementopathies. This is explained with the reduced binding of CFH or its splice variant factor H-like protein 1 (FHL-1) to self-ligands or altered self-ligands (e.g., malondialdehyde [MDA]-modified molecules) involved in homeostasis, thereby causing impaired complement regulation. Considering the critical role of CFH in inhibiting alternative pathway activation on MDA-modified surfaces, we performed an unbiased genome-wide search for genetic variants that modify the ability of plasma CFH to bind MDA in 1,830 individuals and characterized the mechanistic basis and the functional consequences of this. In a cohort of healthy individuals, we identified rs1061170 in CFH and the deletion of CFHR3 and CFHR1 as dominant genetic variants that modify CFH/FHL-1 binding to MDA. We further demonstrated that FHR1 and FHR3 compete with CFH for binding to MDA-epitopes and that FHR1 displays the highest affinity toward MDA-epitopes compared to CFH and FHR3. Moreover, FHR1 bound to MDA-rich areas on necrotic cells and prevented CFH from mediating its cofactor activity on MDA-modified surfaces, resulting in enhanced complement activation. These findings provide a mechanistic explanation as to why the deletion of CFHR3 and CFHR1 is protective in AMD and highlight the importance of genetic variants within the CFH/CFHR3/CFHR1 locus in the recognition of altered-self in tissue homeostasis.

Complement Factor H Related Protein 1 (CFHR1) Serum Level Correlates With Event-Free Survival In Follicular Lymphoma Patients Treated With Rituximab

The anti-CD20 monoclonal antibody rituximab (R) is widely used to treat B-cell malignancies including follicular lymphoma (FL). A better understanding of activity and resistance mechanisms is necessary for improving treatment outcomes. We previously reported that genetic variants in the complement pathway are associated with event-free survival of FL patients following R therapy. This correlation was particularly high for SNP rs3766404, located in intron 6 of Complement Factor H (CFH). Subjects with the minor allele of this SNP experienced inferior event-free survival.Five CFH related proteins (CFHR1-5) share a similar and sometimes overlapping function with CFH, including suppression of complement activation. Genetic variations within the CFH family locus are linked to a variety of complement-mediated disorders such as age-related macular degeneration (AMD) and atypical hemolytic uremic syndrome. Interestingly, AMD patients with the minor allele of rs3766404 frequently have deletion of CFHR3 and CFHR1, suggesting that loss of these proteins functionally impacts complement regulation.The current studies were designed to better understand the relationship between R therapy of FL and CFH family proteins. CFH and CFHR1 protein levels were quantified in serum samples from both normal subjects (n=59) and FL (n=108) subjects from the Iowa/Mayo Lymphoma SPORE Molecular Epidemiology Resource. No correlation was observed between the quantity of CFH in serum and SNP genotype in either cohort. However, in both cohorts, individuals homozygous for the minor allele in SNP rs3766404 lacked detectable expression of CFHR1. Homozygotes for the major allele expressed the highest levels of CFHR1, and heterozygotes expressed intermediate levels.Among FL subjects treated with R as a component of initial therapy, increased levels of CFHR1 were associated with improved event-free survival (hazard ratio 0.48, 95% confidence interval 0.28-0.82, p=0.0051). In contrast, CFHR1 levels had no impact on outcome among the FL subjects who did not receive R as a component of initial therapy. This subset of FL subjects included those observed off therapy. The effect of CFHR1 levels on outcome for those subjects treated with R versus those not treated with R was statistically different (p=0.0023 based on a Cox proportional hazard model). There was no correlation between CFH levels and outcome in any population.CFHR1 binds the complement component C3b, inhibiting downstream complement activation. We previously demonstrated that complement can inhibit R activity in vitro. Specifically, C3b deposition can have a negative impact on antibody–mediated tumor cell killing by interfering with R-induced NK cell activation and antibody dependent cellular cytotoxicity. Our current finding that higher CFHR1 correlates with improved outcome following R therapy provides further evidence that the effect of complement on therapeutic monoclonal antibodies is complex. These findings may have implications for predicting response to, and optimization of, anti-CD20 and other antibody therapies. Ongoing studies are exploring this possibility in additional patient cohorts, the potential role of other CFH family members, and the underlying biology associated with these observations. Disclosures:Link:Genentech: Consultancy; Millenium: Consultancy; Pharmacyclics: Consultancy; Spectrum: Consultancy; Genentech: Research Funding; Millenium: Research Funding; Pharacyclics: Research Funding.

Analysis of Genetic and Predisposing Factors in Japanese Patients with Atypical Hemolytic Uremic Syndrome

AbstractAbstract 3337 Introduction:Hemolytic uremic syndrome (HUS) is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment. Approximately 10% of the cases are classified as atypical due to the absence of Shiga toxin-producing bacterial infection as a trigger. Compared to typical HUS, atypical HUS (aHUS) has a much poorer prognosis, with up to half of the patients progressing to end-stage renal disease, and a higher mortality. Uncontrolled activation of the complement system plays a role in the pathogenesis of aHUS. More than half of the patients with aHUS have the mutations of genes involved in the alternative pathway of the complement system. Mutations with loss-of-function of regulators (CFH, CFI, MCP and THBD) and gain-of-function of key of complement components (C3 and CFB) have been found to predispose to aHUS. In addition, genomic deletion of CFHR3 and CFHR1 has been linked to a risk of aHUS, sometimes together with the presence of CFH autoantibodies. Although many genetic studies on aHUS have been published in recent years, the Asian data are rare so far. It is important to perform genetic screening in patients with aHUS, because genotype-phenotype correlations have clinical significance in predicting renal recovery and transplant outcome. In this study, we analyzed 10 Japanese aHUS patients and the genotype-phenotype relationship was evaluated. Patients and Methods:Ten Japanese patients in Japan-Nara registry of thrombotic microangiopathy (TMA) with aHUS were investigated in this study; eight of them were sporadic and the other two were from one family. Diagnosis of aHUS was made by the simultaneous occurrence of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure without association to Shiga toxin. The CFH antigen level was analyzed by a rocket-immunoelectrophoresis method, and hemolytic assay was performed using sheep red blood cells (Sanchez-Corral P, et al. Mol Immunol 2004). Genomic DNA was extracted from peripheral blood leukocytes of patients and their family members. The genetic mutations of 6 candidate genes and the gene deletion in complement factor H (CFH) and CFH-related genes were analyzed.Results: (1) Clinical features and laboratory data:Plasma ADAMTS13 activity was not severely decreased in all patients (29–119% of the normal). The first episode of aHUS occurred at childhood (≤10 yr) in 7 patients. Nine cases had probable triggering events. The plasma C3 level was low in 4 patients. Three patients showed apparent hemolytic activity against the sheep erythrocytes. Five patients had experienced relapses by the most recent follow-up. Five patients progressed to end-stage renal disease and could not be maintained without hemodialysis or peritoneal dialysis. (2) The result of gene analysis:We identified 7 causative or potentially causative mutations in 8 of these patients, and these mutations were heterozygous. Three of the mutations, p.R1215Q in CFH, p.I1157T in C3, and p.Y189D in MCP, were identified previously, indicating that these mutations are definitely causative for aHUS. The remaining 4 missense mutations, p.A359V in MCP, p.S562L and p.R425C in C3, and p.T500M in THBD, were novel. We considered them as potentially causative mutations based on the available information, including the PolyPhen-2 prediction, a search of the literature, and the position of the missense mutation in the three-dimensional structure. Two patients, who showed apparently an enhanced hemolytic activity, carried CFH p.R1215Q and 3 other patients carried C3 p.I1157T. One patient had 2 causative mutations in different genes. One patient was a compound heterozygote of the 2 MCP mutations. The patients carrying mutations in CFH or C3 had a high frequency of relapse and a worse prognosis. Conclusion:In this study, we identified the cause of aHUS in 8 out of 10 patients. Since the phenotype-genotype correlation of aHUS has clinical significance in predicting renal recovery and transplant outcome, a comprehensively accurate assessment of molecular variation would be necessary as part of the clinical management for aHUS patients. Such an assessment system would facilitate aHUS phenotype- genotype studies in Japan. Disclosures:Matsumoto:Alexion Pharma: Membership on an entity's Board of Directors or advisory committees. Fujimura:Baxter BioScience: Membership on an entity's Board of Directors or advisory committees; Alexion Pharma: Membership on an entity's Board of Directors or advisory committees.

A Hybrid CFHR3-1 Gene Causes Familial C3 Glomerulopathy

Controlled activation of the complement system, a key component of innate immunity, enables destruction of pathogens with minimal damage to host tissue. Complement factor H (CFH), which inhibits complement activation, and five CFH-related proteins (CFHR1-5) compose a family of structurally related molecules. Combined deletion of CFHR3 and CFHR1 is common and confers a protective effect in IgA nephropathy. Here, we report an autosomal dominant complement-mediated GN associated with abnormal increases in copy number across the CFHR3 and CFHR1 loci. In addition to normal copies of these genes, affected individuals carry a unique hybrid CFHR3-1 gene. In addition to identifying an association between these genetic observations and complement-mediated kidney disease, these results provide insight into the protective role of the combined deletion of CFHR3 and CFHR1 in IgA nephropathy.

Association of Genetic Variants in Complement Factor H and Factor H-Related Genes with Systemic Lupus Erythematosus Susceptibility

Systemic lupus erythematosus (SLE), a complex polygenic autoimmune disease, is associated with increased complement activation. Variants of genes encoding complement regulator factor H (CFH) and five CFH-related proteins (CFHR1-CFHR5) within the chromosome 1q32 locus linked to SLE, have been associated with multiple human diseases and may contribute to dysregulated complement activation predisposing to SLE. We assessed 60 SNPs covering the CFH-CFHRs region for association with SLE in 15,864 case-control subjects derived from four ethnic groups. Significant allelic associations with SLE were detected in European Americans (EA) and African Americans (AA), which could be attributed to an intronic CFH SNP (rs6677604, in intron 11, P meta = 6.6×10−8, OR = 1.18) and an intergenic SNP between CFHR1 and CFHR4 (rs16840639, P meta = 2.9×10−7, OR = 1.17) rather than to previously identified disease-associated CFH exonic SNPs, including I62V, Y402H, A474A, and D936E. In addition, allelic association of rs6677604 with SLE was subsequently confirmed in Asians (AS). Haplotype analysis revealed that the underlying causal variant, tagged by rs6677604 and rs16840639, was localized to a ∼146 kb block extending from intron 9 of CFH to downstream of CFHR1. Within this block, the deletion of CFHR3 and CFHR1 (CFHR3-1Δ), a likely causal variant measured using multiplex ligation-dependent probe amplification, was tagged by rs6677604 in EA and AS and rs16840639 in AA, respectively. Deduced from genotypic associations of tag SNPs in EA, AA, and AS, homozygous deletion of CFHR3-1Δ (P meta = 3.2×10−7, OR = 1.47) conferred a higher risk of SLE than heterozygous deletion (P meta = 3.5×10−4, OR = 1.14). These results suggested that the CFHR3-1Δ deletion within the SLE-associated block, but not the previously described exonic SNPs of CFH, might contribute to the development of SLE in EA, AA, and AS, providing new insights into the role of complement regulators in the pathogenesis of SLE.

Deletion of CFHR3 and CFHR1 genes in age-related macular degeneration

Age-related macular degeneration (AMD) impairs vision for approximately 7.5 million Americans. Both susceptibility variants and protective haplotypes in the complement factor H (CFH) gene modulate risk for AMD. Recently, deletion of the 'CFH-related' genes CFHR1 and CFHR3 was found to be segregating with a particular CFH haplotype, which reduced the risk of AMD. We tested the deletion for association in a Caucasian population of 780 cases and 265 controls and examined its effect in the context of known AMD risk factors. The deletion did not segregate perfectly with any one SNP, as previously suggested. CFH haplotype P2 was the most frequent haplotype in deletion homozygotes (47%), and the majority (14/16) of these individuals were homozygous for the non-risk allele of Y402H. Overall, deletion homozygosity was significantly more frequent in controls than cases (2.6% controls, 0.8% cases, P = 0.025, OR = 0.29, 95% CI = 0.10-0.86). After controlling for age, Y402H, smoking and LOC387715 A69S, the protective effect of the deletion was no longer statistically significant (P = 0.27). However, using a CFH haplotype that all deletion homozygotes share as a surrogate for the deletion, this marker remained modestly associated with AMD after adjustment for known risk factors (OR = 0.63, 95% CI 0.39-1.04, P = 0.07). Therefore, deletion of CFHR1 and CFHR3 may account for a small portion of the protection from AMD associated with particular haplotypes in CFH. The presence of protective haplotypes in CFH that do not carry the deletion, suggests that other protective variants in this region have yet to be discovered.