Retinal function and CFH-ARMS2 polymorphisms analysis: a pilot study in Italian AMD patients

Two major susceptibility genes, complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2), have been implicated in age-related macular degeneration (AMD) pathogenesis. We analyzed the association between CFH rs1061170 and/or ARMS2 rs10490924 polymorphisms with central retinal function properties, as evaluated by focal electroretinogram (fERG). Forty early AMD patients, with preserved visual acuity and typical macular lesions, underwent fERG recording (in response to 41 Hz flicker stimuli presented to the central 18 degrees) and CFH/ARMS2 genotyping. Mean fERG amplitude and sensitivity decreased in patients carrying CFH rs1061170 polymorphism (p < 0.01), compared with wild type ones, although visual acuity and funduscopic features were similar across the 2 groups. No significant fERG phase changes were observed. No association was detected between ARMS2 (rs10490924) polymorphism and fERG parameters. Our findings indicate that CFH (rs1061170) polymorphism impacts significantly on retinal function in early AMD patients, and support the hypothesis that dysfunctional CFH might result in early retinal function loss due to a reduction in the immune antioxidant defense mechanism.     

Common variants near FRK/COL10A1 and VEGFA are associated with advanced age-related macular degeneration

Despite significant progress in the identification of genetic loci for age-related macular degeneration (AMD), not all of the heritability has been explained. To identify variants which contribute to the remaining genetic susceptibility, we performed the largest meta-analysis of genome-wide association studies to date for advanced AMD. We imputed 6 036 699 single-nucleotide polymorphisms with the 1000 Genomes Project reference genotypes on 2594 cases and 4134 controls with follow-up replication of top signals in 5640 cases and 52 174 controls. We identified two new common susceptibility alleles, rs1999930 on 6q21-q22.3 near FRK/COL10A1 [odds ratio (OR) 0.87; P = 1.1 × 10(-8)] and rs4711751 on 6p12 near VEGFA (OR 1.15; P = 8.7 × 10(-9)). In addition to the two novel loci, 10 previously reported loci in ARMS2/HTRA1 (rs10490924), CFH (rs1061170, and rs1410996), CFB (rs641153), C3 (rs2230199), C2 (rs9332739), CFI (rs10033900), LIPC (rs10468017), TIMP3 (rs9621532) and CETP (rs3764261) were confirmed with genome-wide significant signals in this large study. Loci in the recently reported genes ABCA1 and COL8A1 were also detected with suggestive evidence of association with advanced AMD. The novel variants identified in this study suggest that angiogenesis (VEGFA) and extracellular collagen matrix (FRK/COL10A1) pathways contribute to the development of advanced AMD.     

Association of rs10490924 in ARMS2/HTRA1 with age‐related macular degeneration in the Pakistani population

Age‐related macular degeneration (AMD) is a disease of the elderly in which central vision is lost because of degenerative changes of the macula. The current study investigated the association of single‐nucleotide polymorphisms (SNPs) with AMD in the Pakistani population. Four SNPs were analyzed in this study: rs1061170 in the CFH, rs429608 near CFB, rs2230199 in the C3, and rs10490924 in ARMS2/HTRA1. This case‐control association study was conducted on 300 AMD patients (125 wet AMD and 175 dry AMD) and 200 unaffected age‐ and gender‐matched control individuals. The association of the SNP genotypes and allele frequency distributions were compared between patients and healthy controls, keeping age, gender, and smoking status as covariates. A significant genotype and variant allele association was found of rs10490924 in ARMS2/HTRA1 with wet AMD, while the SNPs in CFH, CFB, and C3 were not associated with AMD in the current Pakistani cohort. The lack of association of CFH, CFB, and C3 may be attributed to limited sample size. This study demonstrates that genetic causative factors of AMD differ among populations and supports the need for genetic association studies among cohorts from various populations to increase our global understanding of the disease pathogenesis.     

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.     

Complement factor H and hemicentin-1 in age-related macular degeneration and renal phenotypes

In this study, we investigated the associations of complement factor H (CFH) and hemicentin-1 (HMCN1) with age-related macular degeneration (AMD) and renal function. Three scales, measuring the course of AMD and drusen development, were examined in two samples: the Family Age-Related Macular degeneration Study (FARMS), consisting of families ascertained through a single individual with severe AMD, and an unascertained population-based family cohort, the Beaver Dam Eye Study (BDES), which was also used to assess longitudinal changes in AMD and associations with renal function. Associations were performed by a regression accounting for known risk factors as well as familial and sibling effects. Strong evidence of the association of rs1061170 (Y402H) variation with AMD was confirmed (P = 9.15 x 10(-5) in BDES, P = 0.016 in FARMS). This association was observed in multiple AMD scales, suggesting that its role is not phenotype-specific. Polymorphisms in both CFH and HMCN1 appeared to influence the longitudinal rate of change of AMD. The rs1061170 polymorphism was also associated with a reduction in estimated glomerular filtration rate (eGFR) (P = 0.046). Another CFH polymorphism, rs800292, was similarly associated with eGFR [beta = -0.90 (P = 0.022)]. Associations between rs743137 (P = 0.05) and rs680638 (P = 0.022) in HMCN1 with calculated creatinine clearance progression were also observed. Both genes appear to play a role in both AMD and renal pathophysiology. These findings support evidence for common pathways influencing ocular and renal function and suggest that further work is required on their common determinants.     

Multilocus analysis of age-related macular degeneration

Age-related macular degeneration (AMD) is a late onset vision disorder. Recent studies demonstrate that alterations in complement cascade genes are associated with AMD. Of the three identified complement loci, variants in complement factor H (CFH) have the highest impact as does an independent locus at 10q26. Our matched case–control study using the Age-Related Eye Disease Study (AREDS) cohort confirms and extends the associations in these loci. Subjects were genotyped for single nucleotide polymorphisms (SNPs) from CFH, complement component 2 (C2), complement component 3 (C3), complement factor B (CFB), age-related maculopathy susceptibility (ARMS2), HtrA serine peptidase 1 (HTRA1), and apolipoprotein E (APOE). Individual SNPs, and haplotypes showed risk trends consistent with those seen in other population studies for CFH, C3, C2, and CFB. SNP rs10490924 on chromosome 10 in exon 1 of the ARMS2 gene showed a highly significant association with an odds ratio (OR) of 3.2 (95% CI 2.4–4.2) for the risk allele and rs11200638 located in the proximal promoter region of HTRA1 showed a higher significant association with an OR of 3.4 (95% CI 2.5–4.6) with our AMD cases. We found that APOE haplotypes were not significantly associated with disease status. Adjustments for other risk factors did not significantly alter the observed associations. This study validates the complement pathway''s involvement in AMD and suggests that allelic variants in complement genes have a direct role in disease. These results also support previous findings that variants in the region of 10q26 exert an independent risk for AMD.     

Screening of DNA-variants in the properdin gene (CFP) in age-related macular degeneration (AMD)

Several variants in the complement cascade genes (complement factor H [CFH], C2, C3, CFB, and Serping1) have been reported to associate with age-related macular degeneration (AMD). Of these, a member of the complement alternative pathway, CFH, represents the highest risk. As properdin (P) is also an important protein in this pathway, we analysed whether variants in the properdin gene (CFP) at Xp11.4 are associated with AMD. Ten exons of CFP were sequenced in a total of 222 Finnish patients with AMD (150 sporadic cases and 72 familial cases). The controls were 86 age-matched non-AMD patients with no large drusen and no or minimal focal pigmentary abnormalities. A total of four single nucleotide polymorphisms (SNPs) were detected in CFP, three of them infrequent (in 5 patients and controls in total). The fourth SNP, rs1048118 in exon 10, was more frequent, but was not associated with AMD, either alone (p = 0.33) or in conjunction with other risk factors. Thus, CFP does not seem to confer any risk for AMD.     

Ethnic variation in AMD-associated complement factor H polymorphism p.Tyr402His

Age-related macular degeneration (AMD) is the most common cause of irreversible visual loss in the developed world. Previous studies have demonstrated that the c.1204T>C, p.Tyr402His allelic variant in the complement factor H (CFH) gene is associated with an approximately three-fold increased risk for AMD in Caucasians of predominantly European descent. Both the prevalence as well as the phenotypic spectrum of AMD varies widely among persons of different ethnicities. We hypothesized that populations with a lower prevalence of AMD might also have a lower prevalence of the CFH risk allele. In this study we sought to determine the frequency of this sequence variant in control populations of Caucasians, African Americans, Hispanics, Somalis, and Japanese. Normal control populations were assembled for each ethnic group: Caucasian (n=148), Somali (n=128), African American (n=75), Hispanic (n=81), and Japanese (n=82). Individuals were genotyped using a restriction digest assay and the frequency of the C allele at nucleotide position 1204 of the CFH gene was determined. A bioinformatic approach was used to identify SNPs in linkage disequilibrium with rs1061170 (c.1204T>C, p.Tyr402His) from the human haplotype map project database (HapMap) in order to validate the findings. We found widely discordant frequencies of the risk allele between some of the different ethnic groups: Japanese 0.07+/-0.02, Hispanics 0.17+/-0.03, African-Americans 0.35+/-0.04, Caucasians 0.34+/-0.03, and Somalis 0.34+/-0.03. Allele frequencies generated by analysis of the HapMap database were consistent with these findings. This study suggests that there are other yet unidentified genetic factors important in the pathogenesis of AMD that may mitigate the effects of c.1204T>C, p.Tyr402His variant.     

A combination of two novels homozygous FCSK variants cause disorder of glycosylation with defective fucosylation: New patient and literature review

Pathogenic variants in FCSK cause Congenital Disorder of Glycosylation with Defective Fucosylation-2 (FCSK-CDG; MIM: 618,324). It is a rare autosomal recessive genetic disease caused by defects in the L-fucose kinase, which is necessary for the fucose salvage pathway. Herein, we report two novel variants in an Iranian patient, the fourth individual with FCSK-CDG described in the literature. Two homozygous variants in FCSK (rs376941268; NM_145059.3: c.379C > A, p. Leu127Met and rs543223292; NM_145059.3: c.394G > C, p. Asp132His) were identified in the proband. Sanger sequencing conducted on his unaffected parents revealed that they were heterozygous for the same variants. The proband, a four-and-a-half year old Iranian male born to consanguineous parents, manifested Intellectual disability, growth delay, ophthalmic abnormalities, seizures, speech disorder, and feeding difficulties.     

Correlation of complement factor H gene polymorphisms with exudative age-related macular degeneration in a Chinese cohort

To evaluate the association between complement factor H (CFH) gene polymorphism and the risk of exudative age-related macular degeneration (AMD) in a case-control study in a Chinese cohort. One hundred and thirty-six exudative AMD patients and 140 age- and sex-matched control subjects were recruited. We genotyped 3 common single nucleotide polymorphisms (SNPs), namely, -257C>T (rs3753394), Y402H (rs1061170) and IVS15 (rs1329428), genetic analyses were performed on all available genotype data. All the possible haplotypes of these 3 SNPs were detected. Polymerase chain reaction (PCR) and allele-specific restriction endonuclease digestion were performed, some PCR products of these 3 SNPs were sequenced. The risk alleles (T, C or G) of the 3 SNPs conferred 1.72-fold, 3.14-fold, and 1.79-fold of increased likelihood of the disease, respectively (P<0.05). The heterozygous genotype in rs1061170 (TC) revealed significant association, meanwhile rs3753394 and rs1329428 had a slight association with the disease, respectively. Significant differences were shown in the risk alleles in the 3 SNPs among different Chinese cohort. Low linkage disequilibrium was found among the 3 SNPs. The haplotypes TCG and CTG revealed as risk factors, whereas the protective haplotype CTA was over-represented in controls. We found significant association between risk alleles (T, C or G) of the 3 SNPs and the disease. The genetic divergence across multiple populations within Chinese existed. Risk haplotypes and protective haplotype were found in this study.     

Genome-wide association study of age-related macular degeneration identifies associated variants in the TNXB-FKBPL-NOTCH4 region of chromosome 6p21.3

Age-related macular degeneration (AMD) is a leading cause of visual loss in Western populations. Susceptibility is influenced by age, environmental and genetic factors. Known genetic risk loci do not account for all the heritability. We therefore carried out a genome-wide association study of AMD in the UK population with 893 cases of advanced AMD and 2199 controls. This showed an association with the well-established AMD risk loci ARMS2 (age-related maculopathy susceptibility 2)-HTRA1 (HtrA serine peptidase 1) (P =2.7 × 10(-72)), CFH (complement factor H) (P =2.3 × 10(-47)), C2 (complement component 2)-CFB (complement factor B) (P =5.2 × 10(-9)), C3 (complement component 3) (P =2.2 × 10(-3)) and CFI (P =3.6 × 10(-3)) and with more recently reported risk loci at VEGFA (P =1.2 × 10(-3)) and LIPC (hepatic lipase) (P =0.04). Using a replication sample of 1411 advanced AMD cases and 1431 examined controls, we confirmed a novel association between AMD and single-nucleotide polymorphisms on chromosome 6p21.3 at TNXB (tenascin XB)-FKBPL (FK506 binding protein like) [rs12153855/rs9391734; discovery P =4.3 × 10(-7), replication P =3.0 × 10(-4), combined P =1.3 × 10(-9), odds ratio (OR) = 1.4, 95% confidence interval (CI) = 1.3-1.6] and the neighbouring gene NOTCH4 (Notch 4) (rs2071277; discovery P =3.2 × 10(-8), replication P =3.8 × 10(-5), combined P =2.0 × 10(-11), OR = 1.3, 95% CI = 1.2-1.4). These associations remained significant in conditional analyses which included the adjacent C2-CFB locus. TNXB, FKBPL and NOTCH4 are all plausible AMD susceptibility genes, but further research will be needed to identify the causal variants and determine whether any of these genes are involved in the pathogenesis of AMD.     

Genetic variants of Complement factor H gene are not associated with premature coronary heart disease: a family-based study in the Irish population

Background  

The complement factor H (CFH) gene has been recently confirmed to play an essential role in the development of age-related macular degeneration (AMD). There are conflicting reports of its role in coronary heart disease. This study was designed to investigate if, using a family-based approach, there was an association between genetic variants of the CFH gene and risk of early-onset coronary heart disease.     

New insights into disease-specific absence of complement factor H related protein C in mouse models of spontaneous autoimmune diseases

Complement factor H (CFH) protein is an inhibitor of the alternative pathway of complement (AP) both in the fluid phase and on the surface of host cells. Mouse and human complement factor H-related (CFHR) proteins also belong to the fH family of plasma glycoproteins. The main goal of the current study was to compare the presence of mRNA for two mCFHR proteins in spontaneously developing autoimmune diseases in mice such as dense deposit disease (DDD), diabetes mellitus (DM), basal laminar deposits (BLD), collagen antibody-induced arthrits (CAIA) and systemic lupus erythematosus (SLE). Here we report for the first time that the CFHR-C mRNA was universally absent in the liver from three strains of lupus-prone mice and in a diabetic-prone mouse strain. The mRNA levels (pg/ng) for CFH and CFHR-B in MRL-lpr/lpr, at 9 wks and 23 wks were 707.2 ± 44.4, 54.5 ± 5.75 and 729 ± 252.9, 74.04 ± 22.76, respectively. The mRNA levels for CFH and CFHR-B in NZB/NZW mice, at 9 wks and 54 wks were 579.9 ± 23.8, 58.8 ± 1.41 and 890.3 ± 135.2, 63.30 ± 9.2, respectively. CFHR-C protein was absent in the circulation of MRL-lpr/lpr and NZB/NZW mice before and after the development of lupus. Similarly, mRNA and protein for CFHR-C was universally absent in liver and other organs and in the circulation of NOD mice before and after the development of DM. In contrast, the mRNAs for CFH, CFHR-B and CFHR-C were universally present in the liver from mice with and without DDD, BLD and CAIA. The levels of mRNA for CFHR-B in mice with and without BLD were ∼4 times higher than the mice with lupus. The complete absence of mRNA for CFHR-C in lupus and diabetic-prone strains indicates that polymorphic variation within the mouse CFHR family exists and raises the possibility that such variation contributes to lupus and diabetic phenotypes.     

Targeted genotyping of COVID-19 patients reveals a signature of complement C3 and factor B coding SNPs associated with severe infection

We have attempted to explore further the involvement of complement components in the host COVID-19 (Coronavirus disease-19) immune responses by targeted genotyping of COVID-19 adult patients and analysis for missense coding Single Nucleotide Polymorphisms (coding SNPs) of genes encoding Alternative pathway (AP) components. We have identified a small group of common coding SNPs in Survivors and Deceased individuals, present in either relatively similar frequencies (CFH and CFI SNPs) or with stark differences in their relative abundance (C3 and CFB SNPs). In addition, we have identified several sporadic, potentially protective, coding SNPs of C3, CFB, CFD, CFH, CFHR1 and CFI in Survivors. No coding SNPs were detected for CD46 and CD55. Our demographic analysis indicated that the C3 rs1047286 or rs2230199 coding SNPs were present in 60 % of all the Deceased patients (n = 25) (the rs2230199 in 67 % of all Deceased Males) and in 31 % of all the Survivors (n = 105, p = 0.012) (the rs2230199 in 25 % of all Survivor Males). When we analysed these two major study groups using the presence of the C3 rs1047286 or rs2230199 SNPs as potential biomarkers, we noticed the complete absence of the protective CFB rs12614 and rs641153 coding SNPs from Deceased Males compared to Females (p = 0.0023). We propose that in these individuals, C3 carrying the R102G and CFB lacking the R32W or the R32Q amino acid substitutions, may contribute to enhanced association dynamics of the C3bBb AP pre-convertase complex assembly, thus enabling the exploitation of the activation of the Complement Alternative pathway (AP) by SARS-CoV-2.     

Common genetic variants in complement genes other than CFH, CD46 and the CFHRs are not associated with aHUS

It is well established that common genetic variants in CFH, CD46 and the CFHRs are additional risk factors for the development of aHUS. To examine the hypothesis that common variants in other complement genes have a similar effect we genotyped 501 SNPs in 47 complement genes in 94 aHUS patients from Newcastle, 126 aHUS patients from Paris, 374 UK controls and 165 French controls. We replicated the associations in CFH, CD46 and the CFHRs but found no association with any other complement gene. The strongest associations replicated in both cohorts were found for four SNPs within CD46 (p-value<10(-3)) and five SNPs within CFH (p-value<5×10(-3)). Significant replicable associations with single SNPs in CFHR2, CFHR4 and an intergenic SNP (CR1-CD46) were also found. Analysis of the Paris cohort showed that the association with CD46 SNPs was only present in those patients with complement mutations. Haplotype analysis showed at-risk and protective haplotypes in both CD46 and CFH. The CD46 haplotype was only disease-associated in those patients with mutations.     

Expression of Human Complement Factor H Prevents Age-Related Macular Degeneration–Like Retina Damage and Kidney Abnormalities in Aged Cfh Knockout Mice

Complement factor H (CFH) is an important regulatory protein in the alternative pathway of the complement system, and CFH polymorphisms increase the genetic risk of age-related macular degeneration dramatically. These same human CFH variants have also been associated with dense deposit disease. To mechanistically study the function of CFH in the pathogenesis of these diseases, we created transgenic mouse lines using human CFH bacterial artificial chromosomes expressing full-length human CFH variants and crossed these to Cfh knockout (Cfh^−/−) mice. Human CFH protein inhibited cleavage of mouse complement component 3 and factor B in plasma and in retinal pigment epithelium/choroid/sclera, establishing that human CFH regulates activation of the mouse alternative pathway. One of the mouse lines, which express relatively higher levels of CFH, demonstrated functional and structural protection of the retina owing to the Cfh deletion. Impaired visual function, detected as a deficit in the scotopic electroretinographic response, was improved in this transgenic mouse line compared with Cfh^−/− mice, and transgenics had a thicker outer nuclear layer and less sub–retinal pigment epithelium deposit accumulation. In addition, expression of human CFH also completely protected the mice from developing kidney abnormalities associated with loss of CFH. These humanized CFH mice present a valuable model for study of the molecular mechanisms of age-related macular degeneration and dense deposit disease and for testing therapeutic targets.Age-related macular degeneration (AMD) is a disease that progressively damages the photoreceptors and retinal pigment epithelium (RPE) in the macula, resulting in loss of vision in the center of the visual field. AMD is the leading cause of blindness in the elderly population, affecting approximately 15% of the population older than 70 years of age.^1,2 The earliest clinical signs of AMD are pigmentary changes and the appearance of drusen, focal protein- and lipid-rich extracellular deposits that form between the RPE and the Bruch membrane (BrM). Late-stage AMD is characterized by choroidal neovascularization, geographic atrophy, or both, resulting in irreversible central loss of the choriocapillaris, RPE, and photoreceptors.^3–5 Abnormalities in dark adaptation are often the earliest functional change detected in patients with AMD and reflect impairment of rod photoreceptor function.^6,7AMD is a complex disease influenced by a variety of risk factors, including age, which is the greatest.⁸ Of the genetic risk factors, a common polymorphism (T1277C) in the complement factor H (CFH) gene, resulting in a tyrosine (Y) to histidine (H) substitution at amino acid 402 (H402), has been found to be strongly associated with the development of AMD.^9–12 The same polymorphism has also been linked to dense deposit disease (DDD, also known as membranoproliferative glomerulonephritis type II).^13,14 DDD is a condition that primarily affects kidney function. The symptoms usually appear between ages 5 and 15 years and include hematuria, proteinuria, and nephrotic syndrome.^15,16CFH is a major regulator of the alternative pathway (AP) of the complement system. The AP is initiated by complement component 3 (C3) hydrolysis in which a C3 thioester interacts with water to form C3(H₂O). This occurs spontaneously and causes the AP to be continuously active. Uninhibited, C3(H₂O) reacts with complement factor B (FB) to generate C3(H₂O)B, which in the presence of complement factor D is converted to the C3 convertase C3(H₂O)Bb. This conversion allows for further cleavage of C3 to C3b and formation of the C3bBb convertase and initiates the amplification loop. Without negative regulators, this positive feedback loop will quickly deplete all available C3 in the system. CFH is the soluble negative regulator of AP activation. CFH can inhibit formation of the C3 convertase by competing with FB for binding to C3b, accelerate decay of the C3 convertase, and act as a cofactor for factor I–mediated cleavage of C3b.¹⁷The complement system is important in defending an organism against foreign invasion by lyzing alien pathogens via the formation of membrane attack complex and signaling debris clearance. However, if dysregulated, the complement system can also attack host cells, causing local inflammation and tissue damage.¹⁸ Available data support the idea that in AMD, the AP is dysregulated owing to CFH malfunction, causing local inflammation and tissue damage in the macular region of the retina. However, the cellular/molecular mechanism(s) for the risk association of CFH in AMD pathogenesis remains unclear. Consistent with a role for CFH in AMD pathogenesis, aged mice lacking CFH (Cfh^−/−) have an ocular phenotype that shares characteristics of early AMD. These characteristics include decreased electroretinogram (ERG) response, loss of visual acuity, disrupted photoreceptor organization, and structural abnormalities of the BrM.^19,20 These mice also spontaneously develop DDD-like pathologic abnormalities.²¹To further elucidate the function of CFH in AMD pathogenesis, we generated mice in which full-length human CFH is expressed instead of mouse CFH. Using this mouse model, we tested whether i) human CFH interacts with the mouse AP of the complement system, ii) human CFH protein can rescue the ocular and renal phenotype in Cfh^−/− mice, and iii) there are phenotypic differences between mice expressing the normal Y402 or AMD risk–associated H variant of CFH.     

A search for age-related macular degeneration risk variants in Alzheimer disease genes and pathways

Several lines of inquiry point to overlapping molecular mechanisms between late-onset Alzheimer disease (AD) and age-related macular degeneration (AMD). We evaluated summarized results from large genome-wide association studies for AD and AMD to test the hypothesis that AD susceptibility loci are also associated with AMD. We observed association of both disorders with genes in a region of chromosome 7, including PILRA and ZCWPW1 (peak AMD SNP rs7792525, minor allele frequency [MAF] = 19%, odds ratio [OR] = 1.14, p = 2.34 × 10⁻⁶), and with ABCA7 (peak AMD SNP rs3752228, MAF = 0.054, OR = 1.22, p = 0.00012). Next, we evaluated association of AMD with genes in AD-related pathways identified by canonical pathway analysis of AD-associated genes. Significant associations were observed with multiple previously identified AMD risk loci and 2 novel genes: HGS (peak SNP rs8070488, MAF = 0.23, OR = 0.91, p = 7.52 × 10⁻⁵), which plays a role in the clathrin-mediated endocytosis signaling pathway, and TNF (peak SNP rs2071590, MAF = 0.34, OR = 0.89, p = 1.17 × 10⁻⁵), which is a member of the atherosclerosis signaling and the LXR/RXR activation pathways. Our results suggest that AMD and AD share genetic mechanisms.     

The clinical significance of plasma CFHR 1–5 in lupus nephropathy

A deficiency of complement factor H may lead to excessive consumption of C3 and an increase in C3b deposition, which are important pathological characteristics of lupus nephritis. Complement factor H-related proteins (CFHRs), comprising CFHR1 to CFHR5 (CFHR1–5), are members of the wider factor H/CFHR family. Their role in lupus nephritis remains unclear. In this study, we compared circulating levels of CFHR1–5 in 152 patients diagnosed with lupus nephritis and 20 unrelated healthy individuals to explore the relationship between the expression of CFHR1–5 and development of the disease. We found that plasma levels of CFHR3 and CFHR5 were higher in patients with lupus nephritis than in healthy individuals; also, CFHR3 and CFHR5 concentrations increased with increasing systemic lupus erythematosus disease activity index (SLEDAI) values (P < 0.05). Pearson's and Spearman's correlation test results confirmed that plasma CFHR3 and CFHR5 levels in lupus nephritis patients were positively correlated with proteinuria and levels of creatinine (Cr) and anti-dsDNA (correlation coefficients = 0.491–0.717, P < 0.05), while they were negatively correlated with plasma C3 levels and eGFR [correlation coefficients = –(0.706–0.788), P < 0.05]. Receiver operating characteristic (ROC) curve analysis results confirmed that plasma CFHR3 and CFHR5 levels were predictive of SLEDAI values and disease end points (area under the curve = 0.664–0.884, P < 0.05), with patients with both high CFHR3 and high CFHR5 exhibiting the shortest progression-free survival. Thus, both CFHR3 and CFHR5 are of prognostic value in lupus nephritis status.