Complement Factor H Risk Allele Research Articles

Inflammasome Activation in Retinal Pigment Epithelium from Human Donors with Age-Related Macular Degeneration.

Age-related macular degeneration (AMD), the leading cause of blindness in the elderly, is characterized by the death of retinal pigment epithelium (RPE) and photoreceptors. One of the risk factors associated with developing AMD is the single nucleotide polymorphism (SNP) found within the gene encoding complement factor H (CFH). Part of the innate immune system, CFH inhibits alternative complement pathway activation. Multi-protein complexes called inflammasomes also play a role in the innate immune response. Previous studies reported that inflammasome activation may contribute to AMD pathology. In this study, we used primary human adult RPE cell cultures from multiple donors, with and without AMD, that were genotyped for the Y402H CFH risk allele. We found complement and inflammasome-related genes and proteins at basal levels in RPE tissue and cell cultures. Additionally, treatment with rotenone, bafilomycin A, and ATP led to inflammasome activation. Overall, the response to priming and activation was similar, irrespective of disease state or CFH genotype. While these data show that the inflammasome is present and active in RPE, our results suggest that inflammasome activation may not contribute to early AMD pathology.

No CFH or ARMS2 Interaction with Omega-3 Fatty Acids, Low versus High Zinc, or β-Carotene versus Lutein and Zeaxanthin on Progression of Age-Related Macular Degeneration in the Age-Related Eye Disease Study 2: Age-Related Eye Disease Study 2 Report No. 18

To assess whether genotypes at 2 major loci associated with age-related macular degeneration (AMD), complement factor H (CFH), or age-related maculopathy susceptibility 2 (ARMS2), modify the response to oral nutrients for the treatment of AMD in the Age-Related Eye Disease Study 2 (AREDS2). Post hoc analysis of a randomized trial. White AREDS2 participants. AREDS2 participants (n= 4203) with bilateral large drusen or late AMD in 1 eye were assigned randomly to lutein and zeaxanthin, omega-3 fatty acids, both, or placebo, and most also received the AREDS supplements. A secondary randomization assessed modified AREDS supplements in 4 treatment arms: lower zinc dosage, omission of β-carotene, both, or no modification. To evaluate the progression to late AMD, fundus photographs were obtained at baseline and annual study visits, and history of treatment for late AMD was obtained at study visits and 6-month interim telephone calls. Participants were genotyped for the single-nucleotide polymorphisms rs1061170 in CFH and rs10490924 in ARMS2. Bivariate frailty models using both eyes were conducted, including a gene-supplement interaction term and adjusting for age, gender, level of education, and smoking status. The main treatment effects, as well as the direct comparison between lutein plus zeaxanthin and β-carotene, were assessed for genotype interaction. The interaction between genotype and the response to AREDS2 supplements regarding progression to late AMD, any geographic atrophy (GA), and neovascular AMD. Complete data were available for 2775 eyes without baseline late AMD (1684 participants). The participants (mean age ± standard deviation, 72.1±7.7 years; 58.5% female) were followed up for a median of 5 years. The ARMS2 risk allele was associated significantly with progression to late AMD and neovascular AMD (P= 2.40× 10-5 and P= 0.002, respectively), but not any GA (P= 0.097). The CFH risk allele was not associated with AMD progression. Genotype did not modify significantly the response to any of the AREDS2 supplements. CFH and ARMS2 risk alleles do not modify the response to the AREDS2 nutrient supplements with respect to the progression to late AMD (GA and neovascular AMD).

CFH and ARMS2 Polymorphisms Interact with Zinc Supplements in Cognitive Impairment in the Women's Health Initiative Hormone Trial.

An interaction between genetic variants in complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) and high-dose zinc supplementation on progression to advanced age-related macular degeneration (AMD) exists. Because cognitive impairment (CI) is associated with AMD, we used data from the Women's Health Initiative (WHI) to search for a zinc/genetics interaction. To study the interaction of chronic zinc supplementation with genetic variants in CFH and ARMS2 on the development of CI. Zinc dietary supplements, CFH and ARMS2 genotypes, and serial mental status was analyzed in participants with available genetic data (n = 7,483). Cognition was assessed using the Modified Mini-Mental State Examination. The development of CI over 5 years was analyzed by genotype and zinc intake using a repeated measures logistic regression model. Zinc supplementation of approximately 15 mg/day was associated with decreased development of CI in women with 1 or 2 CFH and no ARMS2 risk alleles (OR = 0.46: 1 CFH risk allele; 0.20: 2 CFH risk alleles; p = 0.002). Low-dose zinc (approximately 15 mg) is associated with reduced CI in women with 2 CFH and 0 ARMS2 AMD risk alleles. This interaction is opposite in direction to that observed in AMD, where patients with 2 CFH and 0 ARMS2 risk alleles had increased progression to neovascular AMD if treated with 80 mg/day of zinc. This may be due to a zinc dose-response or to a fundamental difference in the role of zinc in the progression of early CI versus advanced AMD.

Prevalence of age-related macular degeneration associated genetic risk factors and 4-year progression data in the Irish population

Background/aimsAge-related macular degeneration (AMD) is estimated to affect 196 million people >50 years old globally. Prevalence of AMD-associated genetic risk factors and rate of disease progression are unknown in Ireland.MethodsPrevalence...

Response to AREDS supplements according to genetic factors: survival analysis approach using the eye as the unit of analysis

Background/aimsThe Age-Related Eye Disease Study (AREDS) reported the beneficial impact of antioxidant and zinc supplements on the risk of progression to advanced stages of age-related macular degeneration (AMD). We evaluated...

Joint Associations of Diet, Lifestyle, and Genes with Age-Related Macular Degeneration

Unhealthy lifestyles have been associated with increased odds for age-related macular degeneration (AMD). Whether this association is modified by genetic risk for AMD is unknown and was investigated. Interactions between healthy lifestyles AMD risk genotypes were studied in relation to the prevalence of AMD, assessed 6 years later. Women 50 to 79 years of age in the Carotenoids in Age-Related Eye Disease Study with exposure and AMD data (n=1663). Healthy lifestyle scores (0-6 points) were assigned based on Healthy Eating Index scores, physical activity (metabolic equivalent of task hours/week), and smoking pack years assessed in 1994 and 1998. Genetic risk was based on Y402H in complement factor H (CFH) and A69S in age-related maculopathy susceptibility locus 2 (ARMS2). Additive and multiplicative interactions in odds ratios were assessed using the synergy index and a multiplicative interaction term, respectively. AMD presence and severity were assessed from grading of stereoscopic fundus photographs taken in 2001-2004. AMD was present in 337 women, 91% of whom had early AMD. The odds of AMD were 3.3 times greater (95% confidence interval [CI], 1.8-6.1) in women with both low healthy lifestyle score (0-2) and high-risk CFH genotype (CC), relative to those who had low genetic risk (TT) and high healthy lifestyle scores (4-6). There were no significant additive (synergy index [SI], 1.08; 95% CI, 0.70-1.67) or multiplicative (Pinteraction=0.94) interactions in the full sample. However, when limiting the sample to women with stable diets before AMD assessment (n=728) the odds for AMD associated with low healthy lifestyle scores and high-risk CFH genotype were strengthened (odds ratio, 4.6; 95% CI, 1.8-11.6) and the synergy index was significant (SI, 1.34; 95% CI, 1.05-1.70). Adjusting for dietary lutein and zeaxanthin attenuated, and therefore partially explained, the joint association. There were no significant additive or multiplicative interactions for ARMS2 and lifestyle score. Having unhealthy lifestyles and 2 CFH risk alleles increased AMD risk (primarily in the early stages), in an or additive or greater (synergistic) manner. However, unhealthy lifestyles increased AMD risk regardless of AMD risk genotype.

Treatment Response to Antioxidants and Zinc Based on CFH and ARMS2 Genetic Risk Allele Number in the Age-Related Eye Disease Study

To evaluate the impact of complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) risk alleles on the observed response to components of the Age-Related Eye Disease Study (AREDS) formulation. Genetic and statistical subgroup analysis of a randomized, prospective clinical trial. White patients from the AREDS with category 3 or 4 age-related macular degeneration (AMD) with available DNA (n = 989). Four genotype groups based on CFH and ARMS2 risk allele number were defined. Progression to advanced AMD was analyzed by genotype and treatment using Cox proportionate hazards estimates and 7-year events. The effect of predefined genotype group on treatment-specific progression to advanced AMD. Patients with 2 CFH risk alleles and no ARMS2 risk alleles progressed more with zinc-containing treatment compared with placebo, with a hazard ratio (HR) of 3.07 (P = 0.0196) for zinc and 2.73 (P = 0.0418) for AREDS formulation (AF). Seven-year treatment-specific progression rates were: placebo, 17.0%; zinc, 43.2% (P = 0.023); and AF, 40.2% (P = 0.039). Patients with 0 or 1 CFH risk alleles and 1 or 2 ARMS2 risk alleles benefited from zinc-containing treatment compared with placebo, with an HR of 0.514 for zinc (P = 0.012) and 0.569 for AF (P = 0.0254). Seven-year treatment-specific AMD progression rates were as follows: placebo, 43.3%; zinc, 25.2% (P = 0.020); and AF, 27.3% (P = 0.011). Zinc and AF treatment each interacted statistically with these 2 genotype groups under a Cox model, with P values of 0.000999 and 0.00366, respectively. For patients with 0 or 1 CFH risk alleles and no ARMS2 risk alleles, neither zinc-containing treatment altered progression compared with placebo, but treatment with antioxidants decreased progression (HR, 0.380; P = 0.034). Seven-year progression with placebo was 22.6% and with antioxidants was 9.17% (P = 0.033). For patients with 2 CFH risk alleles and 1 or 2 ARMS2 risk alleles, no treatment was better than placebo (48.4%). The benefit of the AREDS formulation seems the result of a favorable response by patients in only 1 genotype group, balanced by neutral or unfavorable responses in 3 genotype groups.

Risk characteristics of the combined geographic atrophy and choroidal neovascularisation phenotype in age-related macular degeneration

AimTo investigate the risk characteristics of the combined geographic atrophy (GA) and choroidal neovascularisation (CNV) phenotype of age-related macular degeneration (AMD) compared to GA or CNV.MethodsPatients with advanced AMD were...

Environmental and genetic risk factors for retinal angiomatous proliferation.

To identify genetic and environmental risk factors in patients with retinal angiomatous proliferation (RAP), a clinical subtype of age-related macular degeneration (AMD). In this case-control study, 108 AMD cases with RAP, 258 AMD patients with choroidal neovascularization (CNV) without RAP and 443 healthy controls were evaluated. Single nucleotide polymorphisms in age-related maculopathy susceptibility 2 (ARMS2) and complement factor H (CFH) and various environmental risk factors were analysed. Statistical analysis was performed by univariate and multivariate regression analysis. High age, female sex and genetic variants in CFH and ARMS2 were identified as risk factors for developing any CNV. In RAP patients, arterial hypertension was also identified as a risk factor (OR 2.39; p = 0.0005). Compared with the 'non-RAP' CNV group, the association with high age (OR 1.05; p = 0.008) and arterial hypertension (OR 1.82; p = 0.02) was significantly higher in RAP patients, while the association with CFH risk alleles (homozygous OR 0.40; p = 0.003) was significantly lower, which was confirmed in a multivariate analysis (OR 0.41; p = 0.03 for the heterozygous risk allele and OR 0.38; p = 0.03 for the homozygous risk allele). The association with the CFH Y402 risk allele was less pronounced in RAP patients than in 'non-RAP' CNV patients, while the association with high age and arterial hypertension appeared to be stronger. These findings stress the importance of detailed phenotyping in AMD to identify homogeneous AMD subtypes and their different risk factors and disease mechanisms.

CFH and ARMS2 Genetic Polymorphisms Predict Response to Antioxidants and Zinc in Patients with Age-related Macular Degeneration

The Age-Related Eye Disease Study (AREDS) demonstrated that antioxidant and zinc supplementation decreases progression to advanced age-related macular degeneration (AMD) in patients with moderate to severe disease. We evaluated the interaction of genetics and type of nutritional supplement on progression from moderate to advanced AMD. Genetic analysis of a randomized, prospective clinical trial. White patients with AREDS category 3 AMD in 1 eye and AREDS categories 1 through 4 AMD in the fellow eye enrolled in the AREDS with available peripheral blood-derived DNA (995). Subjects were evaluated for known AMD genetic risk markers and treatment category. The progression rate to advanced AMD was analyzed by genotypes and AREDS treatment group using Cox regression. The effect of inherited gene polymorphisms on treatment group-specific rate of progression to advanced AMD. Over an average of 10.1 years, individuals with 1 or 2 complement factor H (CFH) risk alleles derived maximum benefit from antioxidants alone. In these patients, the addition of zinc negated the benefits of antioxidants. Treatment with zinc and antioxidants was associated with a risk ratio (RR) of 1.83 with 2 CFH risk alleles (P = 1.03E-02), compared with outcomes for patients without CFH risk alleles. Patients with age-related maculopathy sensitivity 2 (ARMS2) risk alleles derived maximum benefit from zinc-containing regimens, with a deleterious response to antioxidants in the presence of ARMS2 risk alleles. Treatment with antioxidants was associated with an RR of 2.58 for those with 1 ARMS2 risk allele and 3.96 for those with 2 ARMS2 risk alleles (P = 1.04E-6), compared with patients with no ARMS2 risk alleles. Individuals homozygous for CFH and ARMS2 risk alleles derived no benefit from any category of AREDS treatment. Individuals with moderate AMD could benefit from pharmacogenomic selection of nutritional supplements. In this analysis, patients with no CFH risk alleles and with 1 or 2 ARMS2 risk alleles derived maximum benefit from zinc-only supplementation. Patients with one or two CFH risk alleles and no ARMS2 risk alleles derived maximum benefit from antioxidant-only supplementation; treatment with zinc was associated with increased progression to advanced AMD. These recommendations could lead to improved outcomes through genotype-directed therapy.

Complement factor H genotypes impact risk of age-related macular degeneration by interaction with oxidized phospholipids

The rs1061170T/C variant encoding the Y402H change in complement factor H (CFH) has been identified by genome-wide association studies as being significantly associated with age-related macular degeneration (AMD). However, the precise mechanism by which this CFH variant impacts the risk of AMD remains largely unknown. Oxidative stress plays an important role in many aging diseases, including cardiovascular disease and AMD. A large amount of oxidized phospholipids (oxPLs) are generated in the eye because of sunlight exposure and high oxygen content. OxPLs bind to the retinal pigment epithelium and macrophages and strongly activate downstream inflammatory cascades. We hypothesize that CFH may impact the risk of AMD by modulating oxidative stress. Here we demonstrate that CFH binds to oxPLs. The CFH 402Y variant of the protective rs1061170 genotype binds oxPLs with a higher affinity and exhibits a stronger inhibitory effect on the binding of oxPLs to retinal pigment epithelium and macrophages. In addition, plasma from non-AMD subjects with the protective genotype has a lower level of systemic oxidative stress measured by oxPLs per apolipoprotein B (oxPLs/apoB). We also show that oxPL stimulation increases expression of genes involved in macrophage infiltration, inflammation, and neovascularization in the eye. OxPLs colocalize with CFH in drusen in the human AMD eye. Subretinal injection of oxPLs induces choroidal neovascularization in mice. In addition, we show that the CFH risk allele confers higher complement activation and cell lysis activity. Together, these findings suggest that CFH influences AMD risk by modulating oxidative stress, inflammation, and abnormal angiogenesis.

Association of Pattern Dystrophy With an HTRA1 Single-Nucleotide Polymorphism

To evaluate if adult-onset foveomacular vitelliform dystrophy (AOFVD) and butterfly-shaped pigment dystrophy (BSPD) are associated with risk single-nucleotide polymorphisms (SNPs) for age-related macular degeneration (AMD). This was a tertiary referral center-based cross-sectional study including 35 consecutive patients with BSPD and AOFVD, 317 patients with AMD, and 159 unaffected individuals. Demographics, clinical information, and ophthalmic imaging studies were collected. Sequencing was performed for the peripherin/RDS and BEST1 genes, and genotyping was performed for SNPs in the genes for complement factor H (CFH) (rs1061170), HTRA1 (rs11200638), and complement component 3 (C3) (rs2231099). Adult-onset foveomacular vitelliform dystrophy and BSPD were diagnosed in 24 (68.6%) and 11 (31.4%) of the 35 patients, respectively. The mean (SD) age of patients with pattern dystrophy (PD) was 75.3 (10) years and median visual acuity was 0.7. Pattern dystrophy was associated with the HTRA1 risk allele compared with unaffected individuals (odds ratio, 1.72; 95% CI, 1.11-2.66; P = .03). The HTRA1 SNP showed similar prevalence in patients with AMD and PD. The CFH risk allele was significantly less common in patients with PD compared with patients with AMD (odds ratio, 0.47; 95% CI, 0.28-0.76; P = .002). No mutations in peripherin/RDS or BEST1 were detected. The AOFVD and BSPD phenotypes are associated with an HTRA1 risk SNP. These phenotypes often present in elderly individuals who do not carry peripherin/RDS gene mutations and are associated with retinal pigment epithelium alterations and increased risk for choroidal neovascularization. Further research is required to evaluate if AOFVD and BSPD phenotypes in aged individuals are associated with AMD.

Risk Alleles in CFH and ARMS2 Are Independently Associated with Systemic Complement Activation in Age-related Macular Degeneration

Systemic complement activation is associated with age-related macular degeneration (AMD) and has mainly been attributed to a risk allele in the complement factor H (CFH) gene. Whether other important AMD genes also influence complement activation is unclear. In the present case-control study, complement activity and concentrations of complement components and their activation products are measured in AMD patients and in unaffected controls and correlated with genetic variants in the CFH, ARMS2, C3, CFI, and CFB genes. Case-control study. A cohort of 197 confirmed AMD patients and 150 unaffected age-matched controls were recruited prospectively for the study. Hemolytic complement assays (AP50, CP50, and LP50), complement components (C3, CFB, CFI, and CFH), and the activation products (C3d, C5a, and SC5b-9) were analyzed in serum or plasma. The DNA samples were genotyped for 5 single nucleotide polymorphisms (SNPs) previously associated with AMD in the CFH, ARMS2, C3, CFB, and CFI genes. Complement concentrations and their associations with SNPs in the CFH, ARMS2, C3, CFB, and CFI genes. The AMD patients had increased activation of the alternative complement pathway (P = 0.003) and elevated levels of complement activation components C3d (P<0.0001) and C5a (P<0.0001), CFB (P<0.0001), and an increased C3d/C3 ratio (P<0.0001) calculated as a measure of C3 activation. While the CFH risk genotype was significantly associated with the elevated C3d/C3 ratios obtained, in the absence of CFH risk alleles the ARMS2 risk genotype also showed significantly increased levels of complement activation (P = 0.013). Furthermore, the carriers of the CFB protective allele had lower CFB concentrations. The current study found evidence showing that in AMD risk alleles in CFH and ARMS2 are independently associated with complement activation. Especially the C3d/C3 ratio seems to be a strong marker for AMD. The findings suggest that CFH and ARMS2 share a common pathway in the pathogenesis of AMD.

Analysis of complement factor H Y402H, LOC387715, HTRA1 polymorphisms and ApoE alleles with susceptibility to age‐related macular degeneration in Hungarian patients

Recent studies strongly support the role of genetic factors in the aetiology of age-related macular degeneration (AMD). We investigated the frequency of Tyr402His polymorphism of the complement factor H (CFH) gene, Ser69Ala polymorphism at LOC387715, rs11200638 polymorphism of the HTRA1 gene and different apolipoprotein E (ApoE) alleles in Hungarian patients with AMD in order to determine the disease risk conferred by these factors. In a case-control study, we performed clinical and molecular genetic examination of 105 AMD patients (48 patients in the early and 57 in the late subgroup) and 95 unrelated healthy controls. Detailed patient histories were recorded with the use of a questionnaire focusing on known risk factors for AMD. In the early AMD subgroup, homozygous CFH, LOC387715 or HTRA1 polymorphisms conferred a 4.9-fold (95% confidence interval [CI] 1.7-14.2), 7.4-fold (95% CI 2.1-26.2) or 10.1-fold (95% CI 2.5-40.8) risk of disease, respectively. In the late AMD subgroup, carriers of two CFH, LOC387715 or HTRA1 risk alleles were at 10.7-fold (95% CI 3.7-31.0), 11.3-fold (95% CI 3.2-40.4) or 13.5-fold (95% CI 3.3-55.4) greater disease risk, respectively. Two CFH and one LOC387715 risk alleles in combination conferred a 15.0-fold (95% CI 3.2-71.0) increase in risk, whereas two LOC387715 risk alleles combined with one CFH risk allele was associated with a 14.0-fold (95% CI 2.1-95.1) increased risk for late AMD. ApoE alleles neither increased disease risk nor proved to be protective. The CFH, LOC387715 and HTRA1 polymorphisms are strongly associated with the development of AMD in the Hungarian population. The association is particularly pronounced when homozygous risk alleles are present and in the late stages of the disease.

The dot-and-fleck retinopathy of X linked Alport syndrome is independent of complement factor H (CFH) gene polymorphisms

Background and aims:X linked Alport syndrome is characterised by renal failure, hearing loss, lenticonus, and a central and peripheral dot-and-fleck retinopathy. complement factor H (CFH) gene variants are strongly associated...

The HtrA1 Promoter Polymorphism, Smoking, and Age-related Macular Degeneration in Multiple Case-control Samples

To assess the association and combined effect on the risk of age-related macular degeneration (AMD) by the HtrA1 and complement factor H (CFH) polymorphisms, smoking, and serum cholesterol. Clinic-based and population-based case control study. A total of 805 AMD cases and 921 controls from The Eye Clinic of National Eye Institute, Age-Related Eye Diseases Study, Blue Mountain Eye Study Cohort, and Minnesota Lions Eye Bank. DNA samples were genotyped for polymorphisms of rs11200638 in HtrA1 promoter and rs380390 in CFH. HtrA1 protein in ocular tissue was measured. Interactions of the HtrA1 risk allele with the CFH risk variant, smoking status, and cholesterol were assessed. AMD was evaluated by retinal specialists, and AMD subtypes (geographic atrophy and neovascularization) were determined. Strong associations of the HtrA1 risk allele (A) with AMD were present in all sample sets. A similar magnitude of association was observed for central geographic atrophy and neovascular AMD. The combination of the HtrA1 and CFH risk alleles increased AMD susceptibility, as did the combination of the HtrA1 risk allele with smoking. No combined effect of HtrA1 risk allele and cholesterol level was found. Enhanced expression of HtrA1 protein was detected in retina with AMD. Findings from multiple samples support an AMD genetic variant harbored within HtrA1. The risk of advanced AMD increased when the presence of risk alleles from HtrA1 was combined with either CFH risk alleles or history of smoking.

Complement factor H Y402H polymorphism and characteristics of exudative age‐related macular degeneration lesions

The Y402H polymorphism of the complement factor H (CFH) gene is associated with age-related macular degeneration (AMD) in many populations. The reported genotype-phenotype correlations in the CFH Y402H polymorphism have not been pronounced and no studies on the effect of the polymorphism on the subgroups within wet AMD have been performed. In this study, we wanted to evaluate whether the CFH Y402H polymorphism has an effect on clinical variables in recent exudative AMD lesions. The study included 172 patients with exudative AMD. The size of AMD lesions and the presence and area of other AMD lesion variables were recorded in fluorescein angiography (FA) and analysed in relation to the Y402H genotypes. The median lesion size (classic + occult choroidal neovascularization [CNV] + serous pigment epithelium detachment [PED] + haemorrhage, if present) was 8.15 mm(2) in patients homozygous for the CFH risk allele (CC), 7.50 mm(2) in heterozygous patients (CT), and 7.05 mm(2) in those with the normal genotype (TT) (p = 0.599). Areas of classic and occult CNV, combined, without serous PED or haemorrhage were 6.37 mm(2), 5.00 mm(2) and 5.18 mm(2), respectively (p = 0.407). There was a trend for CC patients to have more frequently minimally classic and less frequently predominantly classic lesion composition than CT or TT subjects. We detected no clear impact of the CFH Y402H polymorphism on recent exudative AMD lesion characteristics. Although the complement cascade is implicated in CNV formation and scarring processes in the retina, the Y402H polymorphism appears relatively neutral in these functions.

Evidence for association between multiple complement pathway genes and AMD

In this paper we explore the use of biological knowledge to supplement statistical analysis in identifying genes associated with disease. It has been previously found that the 402H variant in complement factor H (CFH) is associated with risk for developing age related macular degeneration (AMD). By focusing on the single nucleotide polymorphisms (SNPs) in the complement pathway, we were able to use the genotype data from a recently published AMD genome wide association study to identify two additional genes, C7 and MBL2, as potentially associated with subtypes of AMD. Two SNPs situated in introns of C7 and MBL2 could help differentiate between two forms of AMD: wet (more severe form of AMD) and dry (milder form of AMD). We identified a C7 haplotype associated with protection against developing wet AMD among individuals with homozygous CFH risk allele 402H (p-value 0.001 for wet AMD versus dry AMD, odds ratio (OR) 0.16, OR 95% CI 0.05-0.49) as well as among individuals with at least one CFH risk allele (p-value 0.007 for wet AMD versus dry AMD, OR 0.35, OR 95% CI 0.16-0.77). The fact that the statistical scores for the C7 and MBL2 SNPs were significant (low false discovery rate) at the pathway level, but not significant at the genome level suggests that focusing at the pathway level can be beneficial for identifying SNP signals that would be lost at the genome-wide level.

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.