Coding and noncoding variants in the CFH gene and cigarette smoking influence the risk of age-related macular degeneration in a Japanese population

Latest Development on Genetics of Common Retinal Diseases

Many complex forms of retinal diseases are common and pan-ethnic in occurrence. Among them, neovascular age-related macular degeneration, polypoidal choroidal vasculopathy, and central serous choroid retinopathy involve both choroidopathy and neovascularization with multifactorial etiology. They are sight-threatening and potentially blinding. Early treatment is crucial to prevent disease progression. To understand their genetic basis, candidate gene mutational and association analyses, linkage analysis, genome-wide association studies, transcriptome analysis, next-generation sequencing, which includes targeted deep sequencing, whole-exome sequencing, and whole genome sequencing have been conducted. Advanced genomic technologies have led to the identification of many associated genes. But their etiologies are attributed to complicated interactions of multiple genetic and environmental risk factors. Onset and progression of neovascular age-related macular degeneration and polypoidal choroidal vasculopathy are affected by aging, smoking, lifestyle, and variants in over 30 genes. Although some genetic associations have been confirmed and validated, individual genes or polygenic risk markers of clinical value have not been established. The genetic architectures of all these complex retinal diseases that involve sequence variant quantitative trait loci have not been fully delineated. Recently artificial intelligence is making an impact in the collection and advanced analysis of genetic, investigative, and lifestyle data for the establishment of predictive factors for the risk of disease onset, progression, and prognosis. This will contribute to individualized precision medicine for the management of complex retinal diseases.

Genetic Aspects of Age-Related Macular Degeneration and Their Therapeutic Potential

Age-related macular degeneration (AMD) is a complex and multifactorial disease, resulting from the interaction of environmental and genetic factors. The continuous discovery of associations between genetic polymorphisms and AMD gives reason for the pivotal role attributed to the genetic component to its development. In that light, genetic tests and polygenic scores have been created to predict the risk of development and response to therapy. Still, none of them have yet been validated. Furthermore, there is no evidence from a clinical trial that the determination of the individual genetic structure can improve treatment outcomes. In this comprehensive review, we summarize the polymorphisms of the main pathogenetic ways involved in AMD development to identify which of them constitutes a potential therapeutic target. As complement overactivation plays a major role, the modulation of targeted complement proteins seems to be a promising therapeutic approach. Herein, we summarize the complement-modulating molecules now undergoing clinical trials, enlightening those in an advanced phase of trial. Gene therapy is a potential innovative one-time treatment, and its relevance is quickly evolving in the field of retinal diseases. We describe the state of the art of gene therapies now undergoing clinical trials both in the field of complement-suppressors and that of anti-VEGF.

Age-Related Maculopathy Susceptibility 2 and Complement Factor H Polymorphism and Intraocular Complement Activation in Neovascular Age-Related Macular Degeneration

Purpose

To investigate the association of risk alleles in complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) with complement activation products in the aqueous humor in eyes with neovascular age-related macular degeneration (nAMD) including polypoidal choroidal vasculopathy (PCV), retinal angiomatous proliferation (RAP), and pachychoroid neovasculopathy (PNV).

Design

Prospective, comparative, observational study.

Participants

Treatment-naïve patients with nAMD and cataract patients as controls.

Methods

The study included 236 eyes of 236 patients with nAMD and 49 control eyes of 49 patients. Aqueous humor samples were collected from 67 eyes with drusen-associated nAMD, 72 eyes with PCV, 26 eyes with RAP, and 71 eyes with PNV before intravitreal anti-VEGF injection and cataract surgery in the 49 control eyes. Clinical samples were measured for complement component 3a (C3a), C4a, and C5a using a bead-based immunoassay. Genotyping of the ARMS2 A69S (rs10490924), CFH I62V (rs800292), and CFH Y402H (rs1061170) was performed using TaqMan genotyping.

Main Outcome Measures

The levels of complement activation products (C3a, C4a, and C5a) in the aqueous humor in each genotype of ARMS2 and CFH.

Results

The C3a level in the aqueous humor was significantly elevated (P = 0.006) in patients with nAMD and the ARMS2 A69S risk allele, whereas the levels of the complement activation products were not associated with CFH I62V and Y402H genotypes. Among the control eyes, no significant differences were seen in any complement activation products for all genetic polymorphisms. The levels of the complement activation products in the aqueous humor of eyes with the nAMD subtypes for each genetic polymorphism did not show significant differences.

Conclusions

The C3a concentration in the aqueous humor was significantly higher in Japanese nAMD patients with the ARMS2 A69S risk allele, whereas it was not elevated in the patients with CFH I62V. Age-related maculopathy susceptibility 2 A69S polymorphism is strongly associated with local complement activation in nAMD patients.

Association of genetic variants rs641153 (CFB), rs2230199 (C3), and rs1410996 (CFH) with age-related macular degeneration in a Brazilian population

This study aimed to investigate the association among genetic variants of the complement pathway CFB R32Q (rs641153), C3 R102G (rs2230199), and CFH (rs1410996) with age-related macular degeneration (AMD) in a sample of the Brazilian population. In a case-control study, 484 AMD patients were classified according to the clinical age-related maculopathy grading system (CARMS) and compared to 479 unrelated controls. The genetic variants rs1410996 of complement H (CFH), rs641153 of complement factor B (CFB), and rs2230199 of complement 3 (C3) were evaluated through polymerase chain reaction (PCR) and direct sequencing. The associations between single nucleotide polymorphisms (SNPs) and AMD, adjusted by age, were assessed by using logistic regression models. A statistically significant association was observed between AMD risk and rs2230199 variant with an OR of 2.01 (P  = 0.0002) for CG individuals compared to CC individuals. Regarding the comparison of advanced AMD versus the control group, the OR was 2.12 (P = 0.0036) for GG versus AA genotypes for rs1410996 variant. Similarly, the OR for rs2230199 polymorphism was 2.3034 (P  = 5.47^e-05) when comparing CG individuals to CC carriers. In contrast, the rs641153 variant showed a significant protective effect against advanced AMD for GA versus GG genotype (OR = 0.4406; P  = 0.0019). When comparing wet AMD versus controls, a significant association was detected for rs1410996 variant (OR = 2.16; P  = 0.0039) comparing carriers of the homozygous GG versus AA genotype, as well as in the comparisons of GG (OR = 3.0713; P  = 0.0046) and CG genotypes (OR = 2.2249; P  = 0.0002) versus CC genotype for rs2230199 variant, respectively. The rs641153 variant granted a significant protective effect against wet AMD for GA versus GG genotypes (OR = 0.4601; P  = 0.0044). Our study confirmed the risk association between rs2230199 and rs1410996 variants and AMD, and the protective role against AMD for rs641153 variant.

Revisiting the role of factor H in age-related macular degeneration: Insights from complement-mediated renal disease and rare genetic variants

Ophthalmologists are long familiar with the eye showing signs of systemic disease, but the association between age-related macular degeneration and abnormal complement activation, common to several renal disorders, has only recently been elucidated. Although complement activation products were identified in drusen almost three decades ago, it was not until the early 21st century that a single-nucleotide polymorphism in the complement factor H gene was identified as a major heritable determinant of age-related macular degeneration, galvanizing global efforts to unravel the pathogenesis of this common disease. Advances in proteomic analyses and familial aggregation studies have revealed distinctive clinical phenotypes segregated by the functional effects of common and rare genetic variants on the mature protein and its splice variant, factor H-like protein 1. The predominance of loss-of-function, N-terminal mutations implicate age-related macular degeneration as a disease of general complement dysregulation, offering several therapeutic avenues for its modulation. Here, we explore the molecular impact of these mutations/polymorphisms on the ability of variant factor H/factor H-like protein 1 to localize to polyanions, pentraxins, proinflammatory triggers, and cell surfaces across ocular and renal tissues and exert its multimodal regulatory functions and their clinical implications. Finally, we critically evaluate key therapeutic and diagnostic efforts in this rapidly evolving field.

The association between complement factor H rs1061170 polymorphism and age-related macular degeneration: a comprehensive meta-analysis stratified by stage of disease and ethnicity

PURPOSE

The strength of association between complement factor H (CFH) rs1061170 polymorphism and age-related macular degeneration (AMD) differs between AMD subtypes and ethnicities. The main aim was to provide a systematic review and an updated meta-analysis stratified by stage of disease and ethnicity.

METHODS

A literature search in the PubMed-Medline, EMBASE and Web of Science databases was conducted to identify epidemiological studies, published before September 2017, that included at least twp comparison groups (a control group with no signs of AMD and a case group of AMD patients). Genotype distribution, phenotype of the cases, ethnicity, mean age and gender ratio were collected. Odds ratios (ORs) and 95%CIs were estimated under the allelic, homozygous and heterozygous models. Sensitivity and subgroup analyses, by AMD subtype and ethnicity, were performed.

RESULTS

The meta-analysis included data of 27 418 AMD patients and 32 843 controls from 76 studies. In Caucasians, the rs1061170 showed a significant association with early AMD (OR: 1.44; 95%CI 1.27-1.63), dry AMD (OR: 2.90; 95%CI 1.89-4.47) and wet AMD (OR: 2.46; 95%CI 2.15-2.83), under an allelic model. In Asians, the rs1061170 showed a significant association with advanced AMD (OR: 2.09; 95%CI 1.67-2.60), especially wet AMD (OR: 2.24; 95%CI 1.81-2.77).

CONCLUSION

Our work provides a more comprehensive meta-analysis of studies investigating the effect of the CFH rs1061170 polymorphism on AMD risk. These findings not only improve the assessment of disease risk associated with the polymorphism, but also constitute a scientific background to be translated into clinical practice for AMD prevention.

Association Between Complement Factor C2/C3/CFB/CFH Polymorphisms and Age-Related Macular Degeneration: A Meta-Analysis

BACKGROUND

Several previous studies have assessed the contribution of polymorphisms in genes encoding the complement factors C2/C3/CFB/CFH with the risk of age-related macular degeneration (AMD), however the results have been inconsistent. We conducted a meta-analysis to systematically review the potential association between complement factor polymorphisms and AMD.

METHODS

Studies that investigated associations between C2 (rs547154 and rs9332739), C3 (rs1047286), CFB (rs4151667 and rs641153), and CFH (rs551397 and rs2274700) polymorphisms and AMD were identified by searching PubMed, EMBASE, Web of Science, and Cochrane Library databases for articles published prior to January 1, 2018. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to evaluate the association between these polymorphisms and AMD using Stata 12.0 software. Q and I² statistics were used to evaluate between-study heterogeneity. Publication bias analyses were conducted using Begg's test. We also conducted an ethnic subgroup analysis.

RESULTS

A total of 53 studies that included data for 53,774 patients and 56,973 healthy controls were evaluated. The pooled ORs for rs551397, rs2274700, rs4151667, rs641153, rs1047286, rs9332739, and rs547154 in the heterozygote model were 0.53 (95% CI: 0.45-0.61), 0.53 (95% CI: 0.40-0.70), 0.54 (95% CI: 0.46-0.63), 0.48 (95% CI: 0.4-0.57), 1.42 (95% CI: 1.22-1.66), 0.5 (95% CI: 0.45-0.56), and 0.52 (95% CI: 0.43-0.62), respectively.

CONCLUSION

Our findings from this analysis confirmed the protective role of C2/CFB/CFH polymorphisms in the development of AMD, but showed that the single nucleotide polymorphism in C3 was a high-risk factor for AMD. The racial analysis results suggested that the effect of variant alleles was stronger in Caucasians than Asians.

Six-Year Incidence and Risk Factors of Age-Related Macular Degeneration in Singaporean Indians: The Singapore Indian Eye Study

We aimed to determine the 6-year incidence and risk factors of age-related macular degeneration (AMD) in first and second generations of Singaporean Indians. Baseline examination was conducted in 2007-9 and 6-year propsective follow-up examination of this Indian population in 2013-5. All participants underwent interviews with questionnaires and comprehensive medical and eye examinations. Incidence was age-standardized to Singaporean 2010 census. Risk factors associated with AMD incidence were assessed and compared between first and second generations of immigrants. Among 2200 persons who participated in the follow-up examination (75.5% response rate), gradable fundus photographs were available in 2105. The 6-year age-standardized incidences of early and late AMD were 5.26% and 0.51% respectively. Incident early AMD was associated with cardiovascular disease history (HR 1.59, 95% CI 1.04-2.45), underweight body mass index (BMI) (HR 3.12, 95% CI 1.37-7.14) (BMI of <18.5 vs 18.51-25 kg/m2), heavy alcohol drinking (HR 3.14 95% CI 1.25-7.89) and ARMS2 rs3750847 homozygous genetic loci carrier (HR 2.52, 95% CI 1.59-3.99). We found a relatively low incidence of early AMD in this Singaporean Indian population compared to Caucasian populations. Both first and second-generation Indian immigrants have similar incidence and risk factor patterns for early AMD.

Gender-specific association of early age-related macular degeneration with systemic and genetic factors in a Japanese population

The Tsuruoka Metabolomics Cohort Study included subjects aged 35–74 years from participants in annual health check-up programs in Tsuruoka, Japan. The gender-specific associations of early age-related macular degeneration (AMD) with systemic and genetic factors was assessed cross-sectionally. Of these, 3,988 subjects had fundus photographs of sufficient quality, and early AMD was present in 12.3% and 10.3% of men and women, respectively. In men, higher levels of high-density lipoprotein cholesterol and lower levels of triglycerides were associated with increased odds of having early AMD after adjusting for potential risk factors (for each 1 mmol/L increase, odds ratio [OR]: 1.61 and 0.78, 95% confidence interval [CI]: 1.17–2.23 and 0.64–0.96, respectively). In women, higher levels of total cholesterol and low-density lipoprotein cholesterol were associated with increased risk of having early AMD (OR: 1.21 and 1.26, 95% CI: 1.01–1.44 and 1.03–1.53, respectively). Sub-analysis demonstrated that women with ARMS2 A69S polymorphisms had a stronger risk for early AMD (OR: 3.25, 95% CI: 2.10–5.04) than men (OR: 1.65, 95% CI: 1.02–2.69). Differential associations of early AMD with both systemic and genetic factors by sex were demonstrated in a Japanese cohort, which suggests that disease process of early AMD could be different by sex.

Four complement factor H gene polymorphisms in association with AMD: A meta-analysis

AIM

To investigate the possible association between CFH gene polymorphisms -543G>A (rs1410996), A473A (rs2274700), -257C>T (rs3753394), IVS15 (rs1329428) and AMD risk.

METHODS

We searched the published literature in the Medline and Scopus from inception to May 2015. A meta-analysis was performed by the programs RevMan 5.1 and Stata 12.0, and the Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated in fixed or random effect model based on heterogeneity test among studies.

RESULTS

Nineteen studies with a total of 10,676 subjects were included in the present meta-analysis. A statistical significant association was observed between AMD risk and CFH -543G>A polymorphism with OR of 1.77 (95% CI, 1.47-2.12), 2.24 (95% CI, 1.71-2.94), 0.49 (95% CI, 0.38-0.62) and 0.25 (95% CI, 0.18-0.37) in additive, dominant, recessive and codominant models, respectively. Similar results were obtained in polymorphisms A473A, -257C>T, IVS15. Furthermore, stratified analysis for ethnicity showed a significantly strong association between -543G>A, A473A polymorphisms and AMD risk.

CONCLUSION

The present meta-analysis suggested that CFH -543G>A, A473A, -257C>T, and IVS15 polymorphisms might be moderately associated with AMD risk. This conclusion warrants confirmation by further studies.

Association of Two Polymorphisms, rs1061170 and rs1410996, in Complement Factor H with Age-Related Macular Degeneration in an Asian Population: A Meta-Analysis

BACKGROUND

With the increasing number of studies indicating that two single-nucleotide polymorphisms (SNPs), rs1061170 and rs1410996, in complement factor H (CFH) might be associated with the susceptibility to age-related macular degeneration (AMD), the exact association still remains uncertain. Thus, we conducted a meta-analysis to systematically summarize and clarify the association between the two SNPs and the AMD risk particularly in an Asian population.

METHODS

A systematic search of studies on the association of two SNPs with the susceptibility to AMD was conducted in PubMed, Embase and Web of Science. Summary odds ratios (ORs) and 95% confidence intervals (CIs) of allele contrast and genotype contrast were estimated using the random or fixed effects model. The Q statistic test was used to identify heterogeneity, and the funnel plot was adopted to evaluate publication bias. A total of 19 case-control studies on rs1061170 and 8 studies on rs1410996 were included.

RESULTS

Clearly a significantly increased trend of AMD was observed with the rs1061170 (T vs. C: OR = 1.91, 95% CI = 1.71-2.13, pH = 0.029; TC vs. CC: OR = 2.11, 95% CI = 1.30-3.42, pH = 0.792; TT vs. CC: OR = 3.90, 95% CI = 2.45-6.22, pH = 0.774). Similarly, the rs1410996 polymorphism also showed a rising AMD tendency (T vs. C: OR = 1.48, 95% CI = 1.17-1.87, pH < 0.001; TC vs. CC: OR = 1.52, 95% CI = 1.13-2.04, pH = 0.002; TT vs. CC: OR = 2.10, 95% CI = 1.27-3.49, pH < 0.001). What is more, subgroup analysis revealed that both polymorphisms indicated a high risk of nAMD (neovascular AMD) in Asian populations.

CONCLUSIONS

This meta-analysis suggested that CFH rs1061170 and rs1410996 polymorphisms were associated with AMD risk, both of which demonstrated a higher susceptibility to AMD, especially to nAMD. However, the results of rs1410996 should be interpreted with caution due to the limited sample and heterogeneity. Large-scale and well-designed studies are needed to validate our findings.

CFH polymorphisms in a Northern Spanish population with neovascular and dry forms of age-related macular degeneration

PURPOSE

To elucidate the potential role of single-nucleotide polymorphisms (SNPs) in complement factor H (CFH) gene in Northern Spanish patients with age-related macular degeneration (AMD).

METHODS

A case-control study of 130 unrelated native Northern Spanish diagnosed with AMD (46 dry, 35 neovascular and 49 mixed) and 96 healthy controls matched by age and ethnicity were enrolled. DNA was isolated from peripheral blood and genotyped for AMD-associated SNPs (rs3753394, rs529825, rs800292, rs3766404, rs203674, rs10671170, rs3753396 and rs1065489) using TaqMan probes and restriction fragment length polymorphism (RFLP). The association study was performed using the HaploView 4.0 software.

RESULTS

The allelic frequency analysis revealed that rs529825, rs800292, rs203674 and rs10671170 were significantly associated with an increased risk for AMD. The haplotypes CGG (rs3753394, rs529825 and rs800292) and GCAG (rs203674, rs1061170, rs3753396 and rs1065489) were significantly associated with AMD while the haplotypes CAA (rs3753394, rs529825 and rs800292) and TTAG (rs203674, rs1061170, rs3753396 and rs1065489) were found to be protective. Small differ-ences in allelic frequencies were found between dry and neovascular cases; however, these differences were not significant and did not distinguish one form the other.

CONCLUSIONS

This study found significant association of SNPs rs529825, rs800292, rs203674 and rs1061170 in the CFH gene with susceptibility to AMD. We identified haplotypes that confer protection or increased risk of AMD but not specific genetic variants in CFH capable to distinguish the different clinical forms of AMD in this cohort. Collectively, our results confirmed that CFH represents a strong genetic risk factor for this disease in the Northern Spanish population.

Ancestry of the Timorese: age-related macular degeneration associated genotype and allele sharing among human populations from throughout the world

We observed that the third leading cause of blindness in the world, age-related macular degeneration (AMD), occurs at a very low documented frequency in a population-based cohort from Timor-Leste. Thus, we determined a complete catalog of the ancestry of the Timorese by analysis of whole exome chip data and haplogroup analysis of SNP genotypes determined by sequencing the Hypervariable I and II regions of the mitochondrial genome and 17 genotyped YSTR markers obtained from 535 individuals. We genotyped 20 previously reported AMD-associated SNPs in the Timorese to examine their allele frequencies compared to and between previously documented AMD cohorts of varying ethnicities. For those without AMD (average age > 55 years), genotype and allele frequencies were similar for most SNPs with a few exceptions. The major risk allele of HTRA1 rs11200638 (10q26) was at a significantly higher frequency in the Timorese, as well as 3 of the 5 protective CFH (1q32) SNPs (rs800292, rs2284664, and rs12066959). Additionally, the most commonly associated AMD-risk SNP, CFH rs1061170 (Y402H), was also seen at a much lower frequency in the Korean and Timorese populations than in the assessed Caucasian populations (C ~7 vs. ~40%, respectively). The difference in allele frequencies between the Timorese population and the other genotyped populations, along with the haplogroup analysis, also highlight the genetic diversity of the Timorese. Specifically, the most common ancestry groupings were Oceanic (Melanesian and Papuan) and Eastern Asian (specifically Han Chinese). The low prevalence of AMD in the Timorese population (2 of 535 randomly selected participants) may be due to the enrichment of protective alleles in this population at the 1q32 locus.

Gene-gene interaction of CFH, ARMS2, and ARMS2/HTRA1 on the risk of neovascular age-related macular degeneration and polypoidal choroidal vasculopathy in Chinese population

PURPOSE

To evaluate the association and interaction of five single-nucleotide polymorphisms (SNPs) in three genes (CFH, ARMS2, and ARMS2/HTRA1) with neovascular age-related macular degeneration (nAMD) and polypoidal choroidal vasculopathy (PCV) in Chinese population.

METHODS

A total of 300 nAMD and 300 PCV patients and 301 normal subjects participated in the present study. The allelic variants of rs800292, rs2274700, rs3750847, rs3793917, and rs1065489 were determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Gene-gene interactions were evaluated by the data mining approach multifactor-dimensionality reduction (MDR) method.

RESULTS

The risk alleles of CFH rs800292, rs2274700, ARMS2 rs3057847, and ARMS2/HTRA1 rs3793917 showed significant difference between nAMD or PCV patients and controls (all P<0.01). The homozygosity of risk alleles for rs800292, rs2274700, rs3750847, and rs3793917 were significantly different between nAMD patients and controls (all P<0.01), and predisposed to PCV patients (all P<0.01). After cross-validation consistency (CVC) and permutation tests, the two-locus model rs2274700_rs3750847 has a balanced accuracy of 64.37% in predicting nAMD disease risk. The one-marker model, rs3750847, and two-locus model rs2274700_rs3750847 has a balanced accuracy of 66.07% and 65.89% in predicting PCV disease risk, respectively. Furthermore, CFH rs1065489 did not show significant association with nAMD (P>0.01), but was strongly associated with PCV in Chinese patients (P<0.001).

CONCLUSIONS

In this study, we found that the interaction of ARMS2 and ARMS2/HTRA1 is significantly associated with nAMD, and the interaction of CFH and ARMS2 is pronounced in PCV development in Chinese population.

Treatment of macular degeneration using embryonic stem cell-derived retinal pigment epithelium: preliminary results in Asian patients

Embryonic stem cells hold great promise for various diseases because of their unlimited capacity for self-renewal and ability to differentiate into any cell type in the body. However, despite over 3 decades of research, there have been no reports on the safety and potential efficacy of pluripotent stem cell progeny in Asian patients with any disease. Here, we report the safety and tolerability of subretinal transplantation of human embryonic-stem-cell (hESC)-derived retinal pigment epithelium in four Asian patients: two with dry age-related macular degeneration and two with Stargardt macular dystrophy. They were followed for 1 year. There was no evidence of adverse proliferation, tumorigenicity, ectopic tissue formation, or other serious safety issues related to the transplanted cells. Visual acuity improved 9–19 letters in three patients and remained stable (+1 letter) in one patient. The results confirmed that hESC-derived cells could serve as a potentially safe new source for regenerative medicine.

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Human embryonic-stem-cell-derived retinal pigment epithelial cells were transplanted

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Patches of increasing pigmentations were observed after transplantation of the cells

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Visual function stabilized or improved in all of these macular degeneration patients

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There were no serious adverse events associated with the cells up to 1 year

Prognostic phenotypic and genotypic factors associated with photodynamic therapy response in patients with age-related macular degeneration

BACKGROUND

This study aimed to demonstrate the phenotypic and genotypic factors associated with photodynamic therapy (PDT) for age-related macular degeneration (AMD).

METHODS

The study included 149 patients with exudative AMD treated by PDT. Eight phenotypic factors and ten genotypic factors for three single nucleotide polymorphisms (SNPs; rs800292, rs1061170, rs1410996) in the complement factor H (CFH) gene, rs 11200638-SNP in the high temperature requirement A-1 (HTRA1) gene, two SNPs (rs699947, rs2010963) in the vascular endothelial growth factor (VEGF) gene, and four SNPs (rs12948385, rs12150053, rs9913583, rs1136287) in the pigment epithelium-derived factor (PEDF) gene were evaluated.

RESULTS

A significant association with best-corrected visual acuity change was demonstrated in the greatest linear dimension, presence or absence of pigment epithelial detachment, and HTRA1-rs11200638 genotype statistically (P=3.67×10(-4), 1.95×10(-2), 1.24×10(-3), respectively). Best-corrected visual acuity in patients with AA genotype of HTRA1-rs11200638 significantly decreased compared with that in patients with GG genotype (P=1.33×10(-3)). Logistic regression analyses demonstrated HTRA1-rs11200638 genotype was most strongly associated with best-corrected visual acuity outcome from baseline at 12 months after photodynamic therapy (P=4.60×10(-3); odds ratio 2.363; 95% confidence interval 1.303-4.285).

CONCLUSION

The HTRA1-rs11200638 variant showed the most significant association. Therefore, this variant may be used as a prognostic factor to estimate the PDT response with significant predictive power.

Genomic aspects of age-related macular degeneration

Age-related macular degeneration (AMD) is a major late-onset posterior eye disease that causes central vision to deteriorate among elderly populations. The predominant lesion of AMD is the macula, at the interface between the outer retina and the inner choroid. Recent advances in genetics have revealed that inflammatory and angiogenic pathways play critical roles in the pathophysiology of AMD. Genome-wide association studies have identified ARMS2/HTRA1 and CFH as major AMD susceptibility genes. Genetic studies for AMD will contribute to the prevention of central vision loss, the development of new treatment, and the maintenance of quality of vision for productive aging.

Association between complement factor H Val62Ile polymorphism and age-related macular degeneration susceptibility: a meta-analysis

BACKGROUND

An increasing body of studies has assessed the contribution of Val62Ile polymorphism to age-related macular degeneration (AMD) risk, but the exact association still remains uncertain. This meta-analysis was undertaken in order to further characterize the potential association between Val62Ile polymorphism and AMD risk in four different ethnic populations.

METHODS

A meta-analysis was performed using data available from 16 case-control studies evaluating correlation between the Val62Ile polymorphism and AMD in Caucasian, Chinese, Japanese and South Korean populations. Data extraction and study quality assessment were performed in duplicate. Summary odds ratios (ORs) and 95% confidence intervals (CIs) of allele contrast and genotype contrast were estimated using the random-effects model. The Q-statistic test was used to identify heterogeneity, and the funnel plot was adopted to evaluate publication bias.

RESULTS

Sixteen studies involving a total of 11,400 subjects based on the search criteria were included in the meta-analysis. In overall populations, the Val62Ile polymorphism seemed to be associated with AMD (ORAA vs. GG=0.40, 95% CI=0.28-0.59; ORAA+GA vs. GG=0.72, 95% CI=0.64-0.80; ORAA vs. GC+GG=0.50, 95% CI=0.36-0.70; ORA vs. G=0.68, 95% CI=0.58-0.78; ORGA vs. GG=0.71, 95% CI=0.65-0.77). Similarly, subgroup analysis also revealed that this polymorphism was related to AMD in all ethnicities.

CONCLUSIONS

This meta-analysis suggested that Val62Ile polymorphism was associated with susceptibility to AMD.

Retinal angiomatous proliferation associated with risk alleles of ARMS2/HTRA1 gene polymorphisms in Japanese patients

Background

The purpose of this study was to investigate the association between ARMS2/HTRA1, CFH, and C3 gene polymorphisms and retinal angiomatous proliferation (RAP), an infrequent and severe form of exudative age-related macular degeneration, which is characterized by intraretinal neovascularization.

Methods

Diagnosis of RAP was based on fundus photographs, images of fluorescein and indocyanine green angiographies, and optical coherence tomography findings. Six single nucleotide polymorphisms (SNPs), A69S (rs10490924) in ARMS2, rs11200638 in HTRA1, I62V (rs800292) in CFH, Y402H (rs1061170) in CFH, R80G (rs2230199) in C3, and rs2241394 in C3, were genotyped in eight Japanese patients with RAP.

Results

The two SNPs in the ARMS2/HTRA1 were in complete linkage disequilibrium. The frequency of the risk T allele in ARMS2 (the risk A allele in HTRA1) was 93.8% in the RAP patients. The frequency of homozygosity for the risk genotype TT of ARMS2 (the risk genotype AA of HTRA1) was 87.5%. The frequency of the non-risk allele (A) of I62V was 100%. The frequencies of risk alleles of Y402H, R80G, and rs2241394 were 12.5%, 0%, and 18.8%, respectively.

Conclusion

Our results suggest that the risk alleles of the ARMS2/HTRA1 SNPs may be associated with development of RAP and play a major role in the pathogenesis of intraretinal angiogenesis.

Polypoidal choroidal vasculopathy: clinical features and genetic predisposition

Polypoidal choroidal vasculopathy (PCV) is currently recognized as a phenotype of age-related macular degeneration (AMD). PCV is believed to be a type of choroidal neovascularization, although some cases of PCV show a distinct vascular abnormality of the choroidal vessels. PCV often shows several unique clinical manifestations which are apparently different from typical neovascular AMD (tAMD). In addition, the natural course and response to treatment are often different between tAMD and PCV. Moreover, recent genetic studies suggested a possible difference in the genetic susceptibility to disease between tAMD and PCV, as well as the existence of heterogeneity among PCV cases. In viewing the accumulation of knowledge about PCV, we have summarized the recent literature regarding PCV in this review article to improve the understanding of this clinical entity including possible susceptibility genes. We will also discuss the optimal treatment strategies for PCV in accordance with the results of recent clinical and genetic studies.

Mitochondrial DNA haplogroups confer differences in risk for age-related macular degeneration: a case control study

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of vision loss in elderly, Caucasian populations. There is strong evidence that mitochondrial dysfunction and oxidative stress play a role in the cell death found in AMD retinas. The purpose of this study was to examine the association of the Caucasian mitochondrial JTU haplogroup cluster with AMD. We also assessed for gender bias and additive risk with known high risk nuclear gene SNPs, ARMS2/LOC387715 (G > T; Ala69Ser, rs10490924) and CFH (T > C; Try402His, rs1061170).

METHODS

Total DNA was isolated from 162 AMD subjects and 164 age-matched control subjects located in Los Angeles, California, USA. Polymerase chain reaction (PCR) and restriction enzyme digestion were used to identify the J, U, T, and H mitochondrial haplogroups and the ARMS2-rs10490924 and CFH-rs1061170 SNPs. PCR amplified products were sequenced to verify the nucleotide substitutions for the haplogroups and ARMS2 gene.

RESULTS

The JTU haplogroup cluster occurred in 34% (55/162) of AMD subjects versus 15% (24/164) of normal (OR = 2.99; p = 0.0001). This association was slightly greater in males (OR = 3.98, p = 0.005) than the female population (OR = 3.02, p = 0.001). Assuming a dominant effect, the risk alleles for the ARMS2 (rs10490924; p = 0.00001) and CFH (rs1061170; p = 0.027) SNPs were significantly associated with total AMD populations. We found there was no additive risk for the ARMS2 (rs10490924) or CFH (rs1061170) SNPs on the JTU haplogroup background.

CONCLUSIONS

There is a strong association of the JTU haplogroup cluster with AMD. In our Southern California population, the ARMS2 (rs10490924) and CFH (rs1061170) genes were significantly but independently associated with AMD. SNPs defining the JTU mitochondrial haplogroup cluster may change the retinal bioenergetics and play a significant role in the pathogenesis of AMD.

Asian Age-Related Macular Degeneration: Current Concepts and Gaps in Knowledge

Data on the epidemiology and treatment of age-related macular degeneration (AMD) in Asian populations have been scarce. Recently, significant advances in the current knowledge of AMD in Asia have been made, but deficiencies in important areas remain. Epidemiological data on AMD in those 80 years or older are lacking.There are also few incidence data on AMD or polypoidal choroidal vasculopathy (PCV), an important variant of AMD that seems to be more common in Asia. The risk factors for PCV have not been clearly defined to the extent that those for AMD have. No trials of nutritional supplementation for AMD prevention in Asia exist, and there is also a lack of long-term clinical trial data on combination therapy for PCV and indeed very few trial data on PCV. These represent opportunities for future research. With aging populations in Asia, increased data on the prevalence, risk factors, prevention, and treatment of AMD and PCV in Asian populations will be needed to formulate evidence-based public health and clinical guidelines.

Association of genetic polymorphisms with response to bevacizumab for neovascular age-related macular degeneration in the Chinese population

AIMS

To determine whether there is an association between CFH, ARMS2, HTRA1, VEGF, SERPING1 or C3 genotypes and patient response to treatment with intravitreal bevacizumab for neovascular age-related macular degeneration (AMD).

MATERIALS & METHODS

This was a multicenter prospective study. One hundred and forty four patients with neovascular AMD treated with bevacizumab were recruited from 13 centers. Twelve SNPs were genotyped using Sequenom. Visual acuity score (VAS), central retinal thickness and maximum thickness of lesion were measured at each visit.

RESULTS

For the CFH rs800292 polymorphism, mean VAS changes were 4.4, 8.7 and 15.5 letters in the CC, CT and TT genotype carriers (p = 0.009). For ARMS2 rs10490924, mean VAS changes were 3.6, 12.1 and 9.6 letters for the TT, TG and GG genotypes (p = 0.001). For HTRA1 rs11200638, mean VAS changes were 3.6, 12.3 and 9.6 letters for the AA, AG and GG genotypes (p < 0.001).

CONCLUSION

CFH, ARMS2 and HTRA1 genotypes may influence patient response to treatment with intravitreal bevacizumab for neovascular AMD.

Complement factor H genetic variant and age-related macular degeneration: effect size, modifiers and relationship to disease subtype

BACKGROUND

Variation in the complement factor H gene (CFH) is associated with risk of late age-related macular degeneration (AMD). Previous studies have been case-control studies in populations of European ancestry with little differentiation in AMD subtype, and insufficient power to confirm or refute effect modification by smoking.

METHODS

To precisely quantify the association of the single nucleotide polymorphism (SNP rs1061170, 'Y402H') with risk of AMD among studies with differing study designs, participant ancestry and AMD grade and to investigate effect modification by smoking, we report two unpublished genetic association studies (n = 2759) combined with data from 24 published studies (26 studies, 26,494 individuals, including 14,174 cases of AMD) of European ancestry, 10 of which provided individual-level data used to test gene-smoking interaction; and 16 published studies from non-European ancestry.

RESULTS

In individuals of European ancestry, there was a significant association between Y402H and late-AMD with a per-allele odds ratio (OR) of 2.27 [95% confidence interval (CI) 2.10-2.45; P = 1.1 x 10(-161)]. There was no evidence of effect modification by smoking (P = 0.75). The frequency of Y402H varied by ancestral origin and the association with AMD in non-Europeans was less clear, limited by paucity of studies.

CONCLUSION

The Y402H variant confers a 2-fold higher risk of late-AMD per copy in individuals of European descent. This was stable to stratification by study design and AMD classification and not modified by smoking. The lack of association in non-Europeans requires further verification. These findings are of direct relevance for disease prediction. New research is needed to ascertain if differences in circulating levels, expression or activity of factor H protein explain the genetic association.

A common complement C3 variant is associated with protection against wet age-related macular degeneration in a Japanese population

BACKGROUND

Genetic variants in the complement component 3 gene (C3) have been shown to be associated with age-related macular degeneration (AMD) in Caucasian populations of European descent. In particular, a nonsynonymous coding variant, rs2230199 (R102G), is presumed to be the most likely causal variant in the C3 locus based on strong statistical evidence for disease association and mechanistic functional evidence. However, the risk allele is absent or rare (<1%) in Japanese and Chinese populations, and the association of R102G with AMD has not been reported in Asian populations. Genetic heterogeneity of disease-associated variants among different ethnicities is common in complex diseases. Here, we sought to examine whether other common variants in C3 are associated with wet AMD, a common advanced-stage manifestation of AMD, in a Japanese population.

METHODOLOGY/PRINCIPAL FINDINGS

We genotyped 13 tag single nucleotide polymorphisms (SNPs) that capture the majority of common variations in the C3 locus and tested for associations between these SNPs and wet AMD in a Japanese population comprising 420 case subjects and 197 controls. A noncoding variant in C3 (rs2241394) exhibited statistically significant evidence of association (allelic P = 8.32 × 10(-4); odds ratio = 0.48 [95% CI = 0.31-0.74] for the rs2241394 C allele). Multilocus logistic regression analysis confirmed that the effect of rs2241394 was independent of the previously described loci at ARMS2 and CFH, and that the model including variants in ARMS2 and CFH plus C3 rs2241394 provided a better fit than the model without rs2241394. We found no evidence of epistasis between variants in C3 and CFH, despite the fact that they are involved in the same biological pathway.

CONCLUSIONS

Our study provides evidence that C3 is a common AMD-associated locus that transcends racial boundaries and provides an impetus for more detailed genetic characterization of the C3 locus in Asian populations.

Age-related macular degeneration and the complement system

Age-related macular degeneration (AMD) is the leading cause of blindness in the developed world. It is a complex multifactorial disease, and despite new advances in treatment, many patients still succumb to visual impairment. The complement pathway has been implicated in the pathogenesis of many diseases, and recently variants in several genes encoding complement pathway proteins have been associated with AMD. Complement proteins have been found in histological specimens of eyes with AMD. Altered levels of both intrinsic complement proteins and activated products have been found in the circulation of patients with AMD. Complement activation may be triggered by oxidative stress, resulting from retinal exposure to incoming light; indeed an inter-play between these two pathological processes seems to exist. Finally, complement inhibitors are currently being evaluated in clinical trials. This article reviews the role of the complement system in AMD, and the potential of complement inhibition in preventing the devastating blindness resulting from this disease.

Genetic factors associated with age-related macular degeneration

Age-related macular degeneration (AMD) is a complex, multifactorial disease associated with environmental and genetic factors. This review emphasizes the clinical impact of the major genetic factors mainly located in the complement factor H gene and on the 10q26 locus, and their current and future implications for the management of AMD.

Genetic variations strongly influence phenotypic outcome in the mouse retina

Variation in genetic background can significantly influence the phenotypic outcome of both disease and non-disease associated traits. Additionally, differences in temporal and strain specific gene expression can also contribute to phenotypes in the mammalian retina. This is the first report of microarray based cross-strain analysis of gene expression in the retina investigating genetic background effects. Microarray analyses were performed on retinas from the following mouse strains: C57BL6/J, AKR/J, CAST/EiJ, and NOD.NON-H2^-nb1 at embryonic day 18.5 (E18.5) and postnatal day 30.5 (P30.5). Over 3000 differentially expressed genes were identified between strains and developmental stages. Differential gene expression was confirmed by qRT-PCR, Western blot, and immunohistochemistry. Three major gene networks were identified that function to regulate retinal or photoreceptor development, visual perception, cellular transport, and signal transduction. Many of the genes in these networks are implicated in retinal diseases such as bradyopsia, night-blindness, and cone-rod dystrophy. Our analysis revealed strain specific variations in cone photoreceptor cell patterning and retinal function. This study highlights the substantial impact of genetic background on both development and function of the retina and the level of gene expression differences tolerated for normal retinal function. These strain specific genetic variations may also be present in other tissues. In addition, this study will provide valuable insight for the development of more accurate models for human retinal diseases.

VEGF gene polymorphism and response to intravitreal bevacizumab and triple therapy in age-related macular degeneration

PURPOSE

To investigate the association between the vascular endothelial growth factor (VEGF) gene and response to either intravitreal bevacizumab (IVB) or photodynamic therapy with intravitreal triamcinolone acetonide and IVB (triple therapy) for neovascular age-related macular degeneration (AMD).

METHODS

The study consisted of 94 patients with neovascular AMD who underwent IVB and 79 patients with neovascular AMD who underwent triple therapy. Genotypes were determined for four selected tagging single-nucleotide polymorphism (SNP)s of the VEGF gene.

RESULTS

Of the four SNPs studied, one SNP (rs699946) was associated significantly with visual acuity (VA) changes 12 months after treatment-irrespective of whether they received IVB alone (P = 0.044) or triple therapy 0.010). Baseline VA was not significantly different among the three genotypes of rs699946 in either treatment group. There were no significant differences in the number of treatments, incidence of recurrence, or the period until the recurrence according to VEGF rs699946 genetic variant.

CONCLUSIONS

The VEGF gene SNP rs699946 was associated with response to IVB alone and to triple therapy in this study. The G allele in SNP rs699946 can thus be applied as a marker for better visual prognosis in patients with neovascular AMD who receive either IVB or triple therapy.

Complement factor H Y402H variant and risk of age-related macular degeneration in Asians: a systematic review and meta-analysis

PURPOSE

To investigate whether the Y402H variant in the complement factor H gene is associated with age-related macular degeneration (AMD) in Asian populations.

DESIGN

Meta-analysis of previous publications.

PARTICIPANTS

Case-control groups of subjects with AMD and controls from 13 association studies.

METHODS

We performed a meta-analysis of the association between Y402H and AMD in Asian populations using data available from 13 case-control studies involving 3973 subjects. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using fixed- and random-effects models. The Q-statistic test was used to assess heterogeneity, and Egger's test was used to evaluate publication bias. Sensitivity analysis, cumulative meta-analysis, and meta-regression analysis were also performed.

MAIN OUTCOME MEASURES

Allele and genotype frequencies of the Y402H variant.

RESULTS

The Y402H variant showed a significant summary OR of 1.97 (95% CI, 1.54-2.52; P<0.001; allelic contrast model) per allele. Possession of at least 1 copy of the C allele increased the disease risk by 1.97-fold (95% CI, 1.63-2.39; P<0.001; dominant model) and accounted for 8.8% of the attributable risk of AMD in Asian populations. Sensitivity analysis indicated the robustness of our findings, and evidence of publication bias was not observed in our meta-analysis. Meta-regression analysis indicated no significant effect of baseline study characteristics on the summary effect size. Cumulative meta-analysis revealed that the summary ORs were stable and the 95% CIs narrowed with the accumulation of data over time.

CONCLUSIONS

Our analysis provides substantial evidence that the Y402H variant is significantly associated with AMD in Asian populations. Our results expand the number of confirmed AMD susceptibility loci for Asians populations, which provide a better understanding of the genetic architecture underlying disease susceptibility and may advance the potential for preclinical prediction in future genetic tests by a combined evaluation of inherited susceptibility with previously established loci.

Role of complement factor H I62V and age-related maculopathy susceptibility 2 A69S variants in the clinical expression of polypoidal choroidal vasculopathy

PURPOSE

To investigate the role of complement factor H (CFH) I62V (rs800292) and age-related maculopathy susceptibility 2 (ARMS2) A69S (rs10490924) variants in the clinical characteristics of polypoidal choroidal vasculopathy (PCV).

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 226 Japanese patients with PCV in both eyes (44 cases) or in 1 eye (182 cases).

METHODS

Genotyping was performed in all cases for CFH I62V using TaqMan technology and for ARMS2 A69S by denaturing high-performance chromatography. The incidence of 5 characteristic funduscopic findings was studied, including serous retinal detachment, subretinal hemorrhage, serous pigment epithelial detachment (PED), hemorrhagic PED, and classic choroidal neovascularization (CNV).

MAIN OUTCOME MEASURES

The association of clinical phenotypes, including the incidence of each of 5 specific fundus findings, bilaterality of the disease, and age at onset, with variants of CFH I62V or ARMS2 A69S.

RESULTS

Although there was no association of CFH I62V variants with any of the phenotypes in PCV, at-risk variants of ARMS2 A69S were associated with higher incidences of subretinal hemorrhage, serous PED, and hemorrhagic PED. In particular, the at-risk allele homozygosity of ARMS2 A69S increased the likelihood for hemorrhagic PED by 12.4-fold compared with non-carriers of the allele (confidence interval, 1.60-95.1, P = 0.0001). However, the at-risk allele of ARMS2 A69S was associated with a lower incidence of serous retinal detachment (P = 0.0092). Classic CNV was not associated with either variant. The mean age at the onset of PCV was significantly younger (68.8 years) in those with homozygosity of the at-risk allele of ARMS2 A69S than in those with heterozygosity (71.6 years) or in non-carriers (72.6 years) (P = 0.026). Moreover, the at-risk allele frequencies of the ARMS2 A69S were significantly higher in bilateral cases than in unilateral cases (75.0% vs. 59.3%, P = 0.007).

CONCLUSIONS

ARMS2 A69S variants were significantly associated with hemorrhagic or subpigment epithelium lesions of PCV, and with earlier onset and bilateral involvement. The genotyping of ARMS2 A69S is more informative than that of CFH I62V in understanding the clinical features in patients with PCV.

Complement factor H and high-temperature requirement A-1 genotypes and treatment response of age-related macular degeneration

PURPOSE

To determine whether there is an association between complement factor H (CFH), high-temperature requirement A-1 (HTRA1), vascular endothelial growth factor (VEGF), and pigment epithelium-derived factor (PEDF) genotypes and response to treatment with photodynamic therapy (PDT) for age-related macular degeneration (AMD) in a Japanese population.

DESIGN

Prospective, case-control study.

PARTICIPANTS

One hundred ten patients with exudative AMD treated by verteporfin PDT were recruited prospectively at the Department of Ophthalmology, Saitama Medical University Hospital, Saitama, Japan.

METHODS

The patients were genotyped for 4 single nucleotide polymorphisms (SNPs; rs800292, rs1061170, rs1410996, rs2274700) in the CFH gene, a rs11200638-SNP in the HTRA1 gene, 3 SNPs (rs699947, rs1570360, rs2010963) in the VEGF gene, and 4 SNPs (rs12150053, rs12948385, rs9913583, rs1136287) in the PEDF gene using a TaqMan assay.

MAIN OUTCOME MEASURES

The treatment outcomes and genotypes of CFH, HTRA1, VEGF, and PEDF polymorphisms.

RESULTS

Best-corrected visual acuity 1 year after PDT was significantly increased in patients with the HTRA1-rs11200638 GG genotype as compared with patients with the GA or AA genotypes (P = 2.9 × 10⁻², 7.0 × 10⁻⁴, respectively). The rate of recurrence in the 12-month period after PDT was also associated with HTRA1-rs11200638 genotype (P = 3.12 × 10⁻²). Patients with the AA genotype of HTRA1-rs11200638 had an approximately 6-fold greater risk of the recurrence than patients with the GG genotype (P = 5.58 × 10⁻³). Significant differences were demonstrated in the mean time interval from the initial treatment to the time of recurrence for the genotypes of CFH-rs1410996/-rs2274700 (P = 8.50 × 10⁻³).

CONCLUSIONS

The HTRA1-rs11200638 and CFH-rs1410996/-rs2274700 variants were associated with response to PDT in this study population. These variants may be used for genetic biomarkers to estimate visual outcomes and recurrences in the response to PDT with significant predictive power.

Haplotype analysis of the ARMS2/HTRA1 region in Japanese patients with typical neovascular age-related macular degeneration or polypoidal choroidal vasculopathy

PURPOSE

To compare the genomic contribution of the ARMS2/HTRA1 region of chromosome 10q26 to typical neovascular age-related macular degeneration (nAMD) (also known as typical exudative AMD) and to polypoidal choroidal vasculopathy (PCV) METHODS: DNA samples were prepared from 84 patients with typical nAMD, 181 patients with PCV, and 276 control participants. All of the 18 haplotype-tagging single-nucleotide polymorphisms (SNPs) derived from the HapMap data and the potential functional variant, rs11200638, which extended the ARMS2/HTRA1 region by 85.2 kb, were genotyped. Associations were tested using single-SNP and haplotype analyses.

RESULTS

Statistically significant associations were found for six of the 19 SNPs with both typical nAMD and PCV (P < 1 × 10(-3)), peaking at a segment containing three of the SNPs: rs3793917, rs10490924, and rs11200638 (P < 10(-7)). Six common haplotypes were inferred from the nine SNPs spanning 33 kb, which included the six SNPs associated with both phenotypes. Among the six common haplotypes, one showed a positive association with typical nAMD, and two, including the one mentioned above, were associated with PCV. In addition, they corresponded to the risk alleles rs10490924 and rs11200638.

CONCLUSIONS

The association pattern and haplotype estimation in the ARMS2/HTRA1 region of Japanese patients with PCV were very similar to those of Japanese patients with typical nAMD. The polymorphisms responsible for nAMD and PCV may be located in this region or in the strong linkage disequilibrium of rs10490924 and rs11200638.

The molecular genetic basis of age-related macular degeneration: an overview

Age-related macular degeneration (AMD) is a complex disorder of the eye and the third leading cause of blindness worldwide. With a multifactorial etiology, AMD results in progressive loss of central vision affecting the macular region of the eye in elderly. While the prevalence is relatively higher in the Caucasian populations, it has gradually become a major public health issue among the non-Caucasian populations (including Indians) as well due to senescence, rapidly changing demographics and life-style factors. Recent genome-wide association studies (GWAS) on large case-control cohorts have helped in mapping genes in the complement cascade that are involved in the regulation of innate immunity with AMD susceptibility. Genes involved with mitochondrial oxidative stress and extracellular matrix regulation also play a role in AMD pathogenesis. Majority of the associations observed in complement (CFH, CFB, C2 and C3) and other (ARMS2 and HTRA1) genes have been replicated in diverse populations worldwide. Gene-gene (CFH with ARMS2 and HTRA1) interactions and correlations with environmental traits (smoking and body mass index) have been established as significant covariates in AMD pathology. In this review, we have provided an overview on the underlying molecular genetic mechanisms in AMD worldwide and highlight the AMD-associated-candidate genes and their potential role in disease pathogenesis.

Phenotype and genotype characteristics of age-related macular degeneration in a Japanese population

PURPOSE

To describe phenotype and genotype characteristics of age-related macular degeneration (AMD) in Japanese patients.

DESIGN

A case-control study.

PARTICIPANTS

A total of 550 case-control samples composed of 408 consecutive AMD cases and 142 controls.

METHODS

Clinical information assessing age, gender, affected eyes, fundus features, and fluorescein/indocyanine green angiograms were systematically evaluated. Four single nucleotide polymorphisms (SNPs; rs800292, rs1061170, rs1410996, rs2274700) in the complement factor H (CFH) gene, 1 SNP (rs11200638) in the high-temperature requirement factor A1 (HTRA1) gene, 3 SNPs (rs699947, rs1570360, rs2010963) in the vascular endothelial growth factor (VEGF) gene, and 4 SNPs (rs12150053, rs12948385, rs9913583, rs1136287) in the pigment epithelium-derived factor (PEDF) gene were assessed using TaqMan technology.

MAIN OUTCOME MEASURES

The clinical phenotype information and genotypes of CFH, HTRA1, VEGF, and PEDF polymorphisms.

RESULTS

Of Japanese patients with neovascular AMD (nAMD), 219 (58.7%) had typical nAMD and 154 (41.3%) had polypoidal choroidal vasculopathy (PCV). The frequency of bilateral exudative involvement was similar between typical nAMD (15.5%) and PCV (13.6%) (P = 0.613). Significant soft drusen were observed in the fellow eyes of 88 (47.6%) of 185 patients with unilateral typical nAMD and in 25 (18.8%) of 133 patients with unilateral PCV (P = 1.24x10(-7)). A serous pigment epithelium detachment was seen in 55 (25.1%) of 219 patients with typical nAMD and in 64 (41.6%) of 154 patients with PCV. A significant association was noted in CFH-rs800292, CFH-rs1410996, CFH-rs2274700, and HTRA1-rs11200638 with AMD development (P = 2.36x10(-5), 7.18x10(-5), 7.18x10(-5), 2.70x10(-7), respectively; population attributable risk = 57.3%, 57.8%, 57.8%, and 58.9%, respectively). We estimated the highest-risk group to have an approximately 70-fold greater risk of nAMD compared with the lowest-risk group when analyzing a combination of 4 SNPs in the CFH and HTRA1 genes.

CONCLUSIONS

The Japanese AMD phenotype is characterized by a higher frequency of PCV, male predominance, and lower frequency of bilateral presentation compared with Caucasian AMD. Genotype analyses demonstrate a significant population attributable risk for SNPs in the CFH and HTRA1 genes and demonstrate joint effects for both genes. Gene variants in both CFH and HTRA1 contribute significantly to the AMD phenotype in a Japanese population.

An ecological correlation study of late age-related macular degeneration and the complement factor H Y402H polymorphism

PURPOSE

To investigate whether variation in the distribution of the risk allele frequency of the Y402H single-nucleotide polymorphism (SNP) across various ethnicities and geographic regions reflects differences in the prevalence of late age-related macular degeneration (AMD) in those ethnicities.

METHODS

Published data were obtained via a systematic search. Study samples were grouped into clusters by ethnicity and geographic location and the Spearman correlation coefficient of the prevalence of late AMD and risk allele frequencies was calculated across clusters.

RESULTS

Across all ethnicities, AMD prevalence was seen to increase with age. Populations of European descent had both higher risk allele frequencies and prevalence of late AMD than did Japanese, Chinese, and Hispanic descendants. Results for African descendants were anomalous: although allele frequency was similar to that in European populations, the age-specific prevalence of late AMD was considerably lower. The correlation coefficient for the association between allele frequency and AMD prevalence was 0.40 (95% confidence interval [CI] = -0.36 to 0.84, P = 0.28) in all populations combined and 0.71 (95% CI = 0.02-0.94, P = 0.04) when people of African descent were excluded.

CONCLUSIONS

Evidence was found at the population level to support a positive association between the Y204H risk allele and the prevalence of AMD after exclusion of studies undertaken on persons of African ancestry. Data in African, Middle Eastern, and South American populations are needed to provide a better understanding of the association of late AMD genetic risk across ethnicities.

Genetic analysis of typical wet-type age-related macular degeneration and polypoidal choroidal vasculopathy in Japanese population

Age-related macular degeneration (AMD) is a common cause of blindness in the elderly. Caucasian patients are predominantly affected by the dry form of AMD, whereas Japanese patients have predominantly the wet form of AMD and/or polypoidal choroidal vasculopathy (PCV). Although genetic association in the 10q26 (ARMS2/HTRA1) region has been established in many ethnic groups for dry-type AMD, typical wet-type AMD, and PCV, the contribution of the 1q32 (CFH) region seem to differ among these groups. Here we show a single nucleotide polymorphism (SNP) in the ARMS2/HTRA1 locus is associated in the whole genome for Japanese typical wet-type AMD (rs10490924: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ p = 4.1 \times 10 ^{ - 4}$$\end{document}, OR = 4.16) and PCV (rs10490924: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ p = 3.7 \times 10 ^{ -8}$$\end{document}, OR = 2.72) followed by CFH (rs800292: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ p = 7.4 \times 10 ^{ -5}$$\end{document}, OR = 2.08; \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ p = 2.6 \times {10^{ - 4}} $$\end{document}, OR = 2.00), which differs from previous studies in Caucasian populations. Moreover, a SNP (rs2241394) in complement component C3 gene showed significant association with PCV (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ p = 2.5 \times {10^{ - 3}} $$\end{document}, OR = 3.47). We conclude that dry-type AMD, typical wet-type AMD, and PCV have both common and distinct genetic risks that become apparent when comparing Japanese versus Caucasian populations.

Validating, augmenting and refining genome-wide association signals

Studies using genome-wide platforms have yielded an unprecedented number of promising signals of association between genomic variants and human traits. This Review addresses the steps required to validate, augment and refine such signals to identify underlying causal variants for well-defined phenotypes. These steps include: large-scale exact replication across both similar and diverse populations; fine mapping and resequencing; determination of the most informative markers and multiple independent informative loci; incorporation of functional information; and improved phenotype mapping of the implicated genetic effects. Even in cases for which replication proves that an effect exists, confident localization of the causal variant often remains elusive.

ARMS2 (LOC387715) variants in Japanese patients with exudative age-related macular degeneration and polypoidal choroidal vasculopathy

PURPOSE

To determine the characteristics of the polymorphisms in the ARMS2 gene in Japanese patients with age-related macular degeneration (AMD) and those with polypoidal choroidal vasculopathy (PCV) and in healthy controls, and also to show possible associations of the polymorphisms with the disease.

DESIGN

Case-control association study.

METHODS

Fifty-six unrelated Japanese individuals with AMD, 55 with PCV, and 77 controls were studied. The most common polymorphism in the ARMS2 gene on chromosome 10 was resequenced. Association tests were performed for inferred haplotypes.

RESULTS

A total of 22 polymorphisms were identified, and 13 were shared with those in White persons with AMD. The sequence of the deletion-and-insertion polymorphism, de1443ins54, a functional polymorphism causing an instability of the messenger ribonucleic acid of ARMS2 in the Japanese, did not differ from that in White persons. Among the polymorphisms seen in the White population, rs10490923 (R3H) as well as 7 other polymorphisms were not observed in the Japanese. One haplotype, which contained the T allele of the rs10490924 (A69S) and the variant of de1443ins54 polymorphism, had an odds ratio of 3.14 (P = 7.8 x 10(-6)) for AMD and 2.00 (P = .0058) for PCV. Among the 9 polymorphisms that were unique to the Japanese population, 2 had a minor allelic frequency of more than 0.05, and these 2 polymorphism were included as nonrisk haplotypes.

CONCLUSIONS

The de1443ins54 polymorphism is a common variant between White and Japanese populations. It is strongly associated not only with AMD but also with PCV.

Coding variant I62V in the complement factor H gene is strongly associated with polypoidal choroidal vasculopathy

PURPOSE

To investigate whether variants in the complement factor H (CFH) gene are associated with polypoidal choroidal vasculopathy (PCV).

DESIGN

Cross-sectional study.

PARTICIPANTS

A case-control group of 130 PCV subjects and 173 unrelated controls.

METHODS

We conducted an association analysis between CFH variants and PCV in a Japanese population, genotyping 12 tag single nucleotide polymorphisms (SNPs)-including rs3753394, rs800292 (I62V), and rs1061170 (Y402H)-that are highly representative of the common genetic variation in the CFH region. Genotyping was performed using TaqMan technology.

MAIN OUTCOME MEASURES

Allele and haplotype frequencies of the CFH variants.

RESULTS

A highly significant association with PCV was observed across the CFH region. The strongest association was observed at I62V (P = 1.7 x 10(-7)). Six other SNPs (rs3753394, rs6680396, rs1410996, rs2284664, rs1329428, and rs1065489) also showed significant association (10(-3) < P < 10(-6)). These associations became nonsignificant after accounting for rs800292 in a conditional logistic regression analysis. A significant omnibus haplotype association was detected in the entire CFH region (omnibus P = 1.6 x 10(-5) at 7 degrees of freedom). Conditional haplotype-based likelihood ratio tests revealed that the significant omnibus haplotype association disappeared when it was estimated conditional on I62V (omnibus P = 0.20, 6 degrees of freedom, post-I62V dependency), whereas the omnibus haplotype association remained significant when it was estimated conditional on any SNP other than I62V. These findings indicate that multiple observed effects were caused by linkage disequilibrium with I62V, and that this variant fully accounts for the association signals observed at the set of SNPs examined at this locus.

CONCLUSIONS

The present study provides evidence that the complement pathway plays a substantial role in the pathogenesis of PCV. The nonsynonymous variant I62V is a plausible candidate for a causal polymorphism leading to the development of PCV, given its potential for functional consequences on the CFH protein and our own statistical evidence.

FINANCIAL DISCLOSURE(S)

The authors have to proprietary or commercial interest in any materials discussed in this article.

Peripheral retinal drusen and reticular pigment: association with CFHY402H and CFHrs1410996 genotypes in family and twin studies

PURPOSE

To evaluate the relationship between peripheral retinal drusen and reticular pigment changes and genotypes associated with age-related macular degeneration (AMD).

METHODS

Using standard protocols, 2103 family members and twins were examined. Clinical and photographic data were graded according to the Clinical Age-Related Maculopathy Grading System (CARMS) as grade 1 (no AMD), grade 2 (small drusen and/or pigment irregularities), grade 3 (intermediate AMD), grade 4 (central or noncentral geographic atrophy), or grade 5 (neovascular disease). Peripheral drusen and reticular pigment were assessed with a standardized examination. Associations between six AMD genetic variants and retinal phenotypes were analyzed.

RESULTS

AMD grade was associated with peripheral drusen and reticular pigment (odds ratio [OR] 1.9 for advanced AMD; P<0.001). Both peripheral retinal phenotypes were associated with AMD related genotypes. For CFHY402H, the OR was 2.8 for the CC genotype versus TT (P for trend<0.001, with increase in peripheral drusen with each additional risk [C] allele). Similar results were seen for CFHrs1410996. Reticular pigment was related to CFHY402H, with OR 2.0 for the CC genotype versus TT (P for trend<0.001, for increase in pigment with each risk allele) and to CFHrs1410996 (P for trend=0.006). These findings were not seen for the LOC387715 A69S gene region, CFB, C2, or C3. Among individuals with no or minimal maculopathy, CFH variants were associated with more than a twofold increased risk of drusen and reticular pigment.

CONCLUSIONS

Peripheral retinal drusen and reticular pigment are associated with AMD and with CFHY402H and CFHrs1410996 genotypes, adjusting for AMD grade. These phenotypes may be a marker of genetic susceptibility for patients with or without AMD.

C2 and CFB genes in age-related maculopathy and joint action with CFH and LOC387715 genes

Background

Age-related maculopathy (ARM) is a common cause of visual impairment in the elderly populations of industrialized countries and significantly affects the quality of life of those suffering from the disease. Variants within two genes, the complement factor H (CFH) and the poorly characterized LOC387715 (ARMS2), are widely recognized as ARM risk factors. CFH is important in regulation of the alternative complement pathway suggesting this pathway is involved in ARM pathogenesis. Two other complement pathway genes, the closely linked complement component receptor (C2) and complement factor B (CFB), were recently shown to harbor variants associated with ARM.

Methods/Principal Findings

We investigated two SNPs in C2 and two in CFB in independent case-control and family cohorts of white subjects and found rs547154, an intronic SNP in C2, to be significantly associated with ARM in both our case-control (P-value 0.00007) and family data (P-value 0.00001). Logistic regression analysis suggested that accounting for the effect at this locus significantly (P-value 0.002) improves the fit of a genetic risk model of CFH and LOC387715 effects only. Modeling with the generalized multifactor dimensionality reduction method showed that adding C2 to the two-factor model of CFH and LOC387715 increases the sensitivity (from 63% to 73%). However, the balanced accuracy increases only from 71% to 72%, and the specificity decreases from 80% to 72%.

Conclusions/Significance

C2/CFB significantly influences AMD susceptibility and although accounting for effects at this locus does not dramatically increase the overall accuracy of the genetic risk model, the improvement over the CFH-LOC387715 model is statistically significant.