Strong association of the Y402H variant in complement factor H at 1q32 with susceptibility to age-related macular degeneration

Today and future of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in people over 50 in developed countries. Understanding of the pathologic process, genetic mechanisms, and risk factors of this disease has the benefit of seeking newer and more effective treatment options. Current clinical therapy for AMD shows a dramatic change from a decade ago. Anti-VEGF drug therapy is regarded as the more effective treatment for neovascular AMD now, especially combining PDT therapy. In the future, the genetic and biochemical therapies may be the promising treatments for AMD. This paper will focus on the progress of pathology, candidate genes of AMD, risk factors, and the existing drugs or surgical therapies available, in order to present some new directions of care with the prospect of improved vision in many patients suffered from AMD.

Genetic associations in polypoidal choroidal vasculopathy: a systematic review and meta-analysis

PURPOSE

To investigate the genetic associations of polypoidal choroidal vasculopathy (PCV), the genetic difference between PCV and age-related macular degeneration (AMD), and the genotype-phenotype correlation of PCV.

METHODS

A systematic review and meta-analysis were performed. Published articles about genetic associations of PCV identified from a literature search were reviewed. The following data from individual studies were extracted and analyzed: 1) comparison of genetic polymorphisms between PCV and controls; 2) comparison of genetic polymorphisms between PCV and AMD; and 3) comparison of phenotypes between different genotype groups.

RESULTS

A total of 33 articles fulfilled the inclusion criteria. With meta-analyses, variants in four genes were found to be significantly associated with PCV: LOC387715 rs10490924 (n=9, allelic odds ratio [OR]=2.27, p<0.00001), HTRA1 rs11200638 (n=4, OR=2.72, p<0.00001), CFH rs1061170 (n=4, OR=1.72, p<0.00001), CFH rs800292 (n=5, OR=2.10, p<0.00001), and C2 rs547154 (n=3, OR=0.56, p=0.01). LOC387715 rs10490924 was the only variant showing a significant difference between PCV and wet AMD (n=5, OR=0.66, p<0.00001). The risk genotypes of rs10490924 were associated with larger lesion size, greater chance of vitreous hemorrhage, and worse therapeutic response in PCV.

CONCLUSIONS

LOC387715 rs10490924 was associated with PCV and its clinical manifestations, and showed a discrepant distribution between PCV and AMD. Variants in HTRA1, CFH, and C2 were also associated with PCV.

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.

Association between high-risk disease loci and response to anti-vascular endothelial growth factor treatment for wet age-related macular degeneration

PURPOSE

To investigate whether there is an association between known age-related macular degeneration genetic risk variants in the CFH, ARMS2, and HTRA1 genes and response to anti-vascular endothelial growth factor (VEGF) (ranibizumab or bevacizumab) treatment for wet age-related macular degeneration.

METHODS

A retrospective review of 150 patients with documented wet age-related macular degeneration based on clinical examination and fluorescein angiogram was performed. Patients received anti-VEGF therapy with ranibizumab and/or bevacizumab. Patients were genotyped for the single-nucleotide polymorphism rs1061170, rs10490924, rs3750848, rs3793917, rs11200638, and rs932275 and for the indel del443ins54 spanning the CFH, ARMS2, and HTRA1 genes.

RESULTS

There were 57 patients who were characterized as negative responders to anti-VEGF therapy, and 93 patients who were characterized as positive responders. There was no significant difference in mean baseline visual acuity between the groups. Negative responders were followed for a mean duration of 24.0 months, while positive responders were followed for a mean duration of 22.0 months. Although the frequency of the at-risk alleles was higher in the positive responders when compared with the negative responder, this did not reach statistical significance. Additionally, there was no significant association between genotype and the number of injections or absolute change in visual acuity in both groups of responders.

CONCLUSION

In our patient cohort, there was no statistically significant association between response to anti-VEGF therapy and the genotype in both positive-responder and negative-responder groups. Larger studies with more power are necessary to further determine whether a pharmacogenetic association exists between wet age-related macular degeneration and anti-VEGF therapy.

Pharmacogenetics and age-related macular degeneration

Pharmacogenetics seeks to explain interpatient variability in response to medications by investigating genotype-phenotype correlations. There is a small but growing body of data regarding the pharmacogenetics of both nonexudative and exudative age-related macular degeneration. Most reported data concern polymorphisms in the complement factor H and age-related maculopathy susceptibility 2 genes. At this time, the data are not consistent and no definite conclusions may be drawn. As clinical trials data continue to accumulate, these relationships may become more apparent.

Complement Factor H Y402H polymorphism is associated with an increased risk of mortality after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) accounts for 10% to 15% of all strokes and is a major cause of morbidity and mortality. Despite advances in management, numerous clinical trials have failed to demonstrate significant benefit of medical and surgical interventions, underscoring the need for the identification of novel therapeutic targets based on improved understanding of ICH pathophysiology and optimal risk stratification based on reliable and effective prognosticators. The alternative complement cascade has been implicated as an important contributor to neurological injury after ICH. Therefore, common, functionally relevant genetic variants in the key components of this pathway have been associated with greater inflammation post-ictus, further cerebral damage, and ultimately, a worse outcome. We investigated the affects of single-nucleotide polymorphisms (SNP) on mortality in complement component 3 C3 (rs2230199), complement component 5 C5 (rs17611), and Complement Factor H (CFH; rs1061170) genes, which are associated with the onset and progression of several neurological diseases, in a prospective cohort of patients with spontaneous ICH. From February 2009 through May 2010, adult patients with spontaneous ICH were admitted to the Columbia University Neurological Intensive Care Unit and enrolled in the Intracerebral Hemorrhage Outcomes Project. Demographic, clinical, radiographic, and treatment data were prospectively collected. Buccal swabs were obtained, and isolated cells were sequenced for the aforementioned SNP. A total of 103 patients were admitted with ICH, and of these, 82 consented for genetic testing and were included in the analysis. The median age was 61 years and 39% were females. The median Glasgow Coma Scale score on admission was 11.5. The CFH SNP was significantly associated with both discharge (p = 0.01) and 6-month mortality (p = 0.02), while no such association was observed for C3 (p = 0.545 and p = 0.830) or C5 (p = 0.983 and p = 0.536) SNP. Additionally, after controlling for pertinent variables identified in the univariate analysis, the CFH genotype independently predicted mortality at discharge (p = 0.019, odds ratio [OR] 7.62, 95% confidence interval [CI] 1.40-41.6) and at 6 months (p = 0.041, OR 1.822, 95% CI 1.025-3.239). The CFH genotype was also independently predictive of survival duration (p = 0.041, OR 1.822, 95% CI 1.025-3.239). We concluded that CFH Y402H polymorphism independently predicts mortality at discharge and 6-months and survival duration after spontaneous ICH.

Reconsidering the connection between vitamin D levels and age-related macular degeneration

PURPOSE

Recent evidence has suggested a correlation between reduced vitamin D levels and delayed angiogenesis and reduced inflammatory response, which are known to have a major role in the development and progression of age-related macular degeneration (AMD).

DESIGN

Cross-sectional study.

PARTICIPANTS

Members of the Maccabi Healthcare Services (MHS, one of the four largest Israeli Health Maintenance Organization) aged ≥60 years, whose vitamin D levels were taken as part of routine examinations between 2000 and 2008.

METHODS

All data for this study were obtained from MHS databases that include medical information on 1.8 million subscribers.

MAIN OUTCOME MEASURES

Serum 25-OH vitamin D levels.

RESULTS

The total study population comprised of 1045 members diagnosed as having AMD, and 8124 as non-AMD, for whom there was information on vitamin D levels. The mean±SD level of 25-OH vitamin D was 24.1±9.41  ng/ml (range 0.8-120) for the AMD patients and 24.13±9.50  ng/ml (range 0.0-120) for the controls (P=ns). One-third (33.6%) of the AMD patients and 32.86% of the controls had a 25-OH vitamin D level <16  ng/ml, and the proportions of tests in which the 25-OH vitamin D level was >74  ng/ml were 0.19 and 0.14%, respectively (P=ns).

CONCLUSIONS

No association was detected between vitamin D levels and the presence of AMD in this cross-sectional study. These results raise some doubt about an association between reduced vitamin D levels and the prevalence of AMD.

Identifying subtypes of patients with neovascular age-related macular degeneration by genotypic and cardiovascular risk characteristics

BACKGROUND

One of the challenges in the interpretation of studies showing associations between environmental and genotypic data with disease outcomes such as neovascular age-related macular degeneration (AMD) is understanding the phenotypic heterogeneity within a patient population with regard to any risk factor associated with the condition. This is critical when considering the potential therapeutic response of patients to any drug developed to treat the condition. In the present study, we identify patient subtypes or clusters which could represent several different targets for treatment development, based on genetic pathways in AMD and cardiovascular pathology.

METHODS

We identified a sample of patients with neovascular AMD, that in previous studies had been shown to be at elevated risk for the disease through environmental factors such as cigarette smoking and genetic variants including the complement factor H gene (CFH) on chromosome 1q25 and variants in the ARMS2/HtrA serine peptidase 1 (HTRA1) gene(s) on chromosome 10q26. We conducted a multivariate segmentation analysis of 253 of these patients utilizing available epidemiologic and genetic data.

RESULTS

In a multivariate model, cigarette smoking failed to differentiate subtypes of patients. However, four meaningfully distinct clusters of patients were identified that were most strongly differentiated by their cardiovascular health status (histories of hypercholesterolemia and hypertension), and the alleles of ARMS2/HTRA1 rs1049331.

CONCLUSIONS

These results have significant personalized medicine implications for drug developers attempting to determine the effective size of the treatable neovascular AMD population. Patient subtypes or clusters may represent different targets for therapeutic development based on genetic pathways in AMD and cardiovascular pathology, and treatments developed that may elevate CV risk, may be ill advised for certain of the clusters identified.

Retinal pigment epithelial expression of complement regulator CD46 is altered early in the course of geographic atrophy

In geographic atrophy (GA), the non-neovascular end stage of age-related macular degeneration (AMD), the macular retinal pigment epithelium (RPE) progressively degenerates. Membrane cofactor protein (MCP, CD46) is the only membrane-bound regulator of complement expressed on the human RPE basolateral surface. Based on evidence of the role of complement in AMD, we hypothesized that altered CD46 expression on the RPE would be associated with GA development and/or progression. Here we report the timeline of CD46 protein expression changes across the GA transition zone, relative to control eyes, and relative to events in other chorioretinal layers. Eleven donor eyes (mean age 87.0 ± 4.1 yr) with GA and 5 control eyes (mean age 84.0 ± 8.9 yr) without GA were evaluated. Macular cryosections were stained with PASH for basal deposits, von Kossa for calcium, and for CD46 immunoreactivity. Internal controls for protein expression were provided by an independent basolateral protein, monocarboxylate transporter 3 (MCT3) and an apical protein, ezrin. Within zones defined by 8 different semi-quantitative grades of RPE morphology, we determined the location and intensity of immunoreactivity, outer segment length, and Bruch's membrane calcification. Differences between GA and control eyes and between milder and more severe RPE stages in GA eyes were assessed statistically. Increasing grades of RPE degeneration were associated with progressive loss of polarity and loss of intensity of staining of CD46, beginning with the stages that are considered normal aging (grades 0-1). Those GA stages with affected CD46 immunoreactivity exhibited basal laminar deposit, still-normal photoreceptors, and concomitant changes in control protein expression. Activated or anteriorly migrated RPE (grades 2-3) exhibited greatly diminished CD46. Changes in RPE CD46 expression thus occur early in GA, before there is evidence of morphological RPE change. At later stages of degeneration, CD46 alterations occur within a context of altered RPE polarity. These changes precede degeneration of the overlying retina and suggest that therapeutic interventions be targeted to the RPE.

Complement factor H Y402H gene polymorphism and response to intravitreal bevacizumab in exudative age-related macular degeneration

PURPOSE

To determine whether different complement factor H (CFH) genotypes play a role in treatment of age-related macular degeneration (AMD) with intravitreal bevacizumab.

METHODS

In this prospective study, we included 197 patients with exudative AMD and treated with 1.25 mg intravitreal bevacizumab at 6-week intervals until choroidal neovascularization (CNV) was no longer active. In all patients, ophthalmological examinations, visual acuity, optical coherence tomography (OCT), fundus photography and fluorescein angiography were performed. Single nucleotide polymorphism (SNP) genotyping was performed using restriction fragment length polymorphism (RFLP) analysis of polymerase chain reaction (PCR) products.

RESULTS

Age, gender and baseline mean visual acuity were similar among the three CFH genotypes. There was no significant difference in underlying lesion type of CNV, lesion size, number of injections or macula thickness. When examining the effect of genotype on post-treatment visual acuities, we observed a significant worse outcome for distance and reading visual acuity in the CFH 402HH genotype group. The number of patients who lost 3 or more lines in distance and reading visual acuity testing was significantly higher in the CFH 402HH (41%, 46%) genotype group than in patients with the CFH 402YY (28%, 26%) and CFH 402YH (26%, 24%) genotype.

CONCLUSIONS

In addition to the higher risk for exudative AMD in patients with the CFH 402HH genotype that was found in previous studies, our results show that the CFH 402HH genotype also correlates with lower visual acuity outcome after treatment with bevacizumab, suggesting that pharmacogenetics of CFH plays a role in response to treatment of wet AMD.

Genetics of age-related macular degeneration: current concepts, future directions

Age-related macular degeneration (AMD) is a progressive degenerative disease which leads to blindness, affecting the quality of life of millions of Americans. More than 1.75 million individuals in the United States are affected by the advanced form of AMD. The etiological pathway of AMD is not yet fully understood, but there is a clear genetic influence on disease risk. To date, the 1q32 (CFH) and 10q26 (PLEKHA1/ARMS2/HTRA1) loci are the most strongly associated with disease; however, the variation in these genomic regions alone is unable to predict disease development with high accuracy. Therefore, current genetic studies are aimed at identifying new genes associated with AMD and their modifiers, with the goal of discovering diagnostic or prognostic biomarkers. Moreover, these studies provide the foundation for further investigation into the pathophysiology of AMD by utilizing a systems-biology-based approach to elucidate underlying mechanistic pathways.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Structural basis for engagement by complement factor H of C3b on a self surface

Complement factor H (FH) attenuates C3b molecules tethered by their thioester domains to self surfaces and thereby protects host tissues. Factor H is a cofactor for initial C3b proteolysis that ultimately yields a surface-attached fragment (C3d) corresponding to the thioester domain. We used NMR and X-ray crystallography to study the C3d-FH19-20 complex in atomic detail and identify glycosaminoglycan-binding residues in factor H module 20 of the C3d-FH19-20 complex. Mutagenesis justified the merging of the C3d-FH19-20 structure with an existing C3b-FH1-4 crystal structure. We concatenated the merged structure with the available FH6-8 crystal structure and new SAXS-derived FH1-4, FH8-15 and FH15-19 envelopes. The combined data are consistent with a bent-back factor H molecule that binds through its termini to two sites on one C3b molecule and simultaneously to adjacent polyanionic host-surface markers.

A review and meta-analysis of the association between C-reactive protein and age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in people over 60 in western countries. Inflammatory markers have been implicated in the development and progression of AMD. C-reactive protein (CRP) is an inflammatory marker known to be associated with cardiovascular disease, and a link between AMD and CRP has been suggested. In this systematic review we summarize the currently available evidence from clinic-based and population-based studies investigating this association. A meta-analysis of evidence from eleven studies (41,690 study participants) shows that high serum levels (>3 mg/L) of CRP are associated with a two-fold likelihood of late onset AMD, compared to low levels (<1mg/L). Sub-group meta-analyses show a higher association in studies using ophthalmoscopic examination, compared to those using photographic grading (pooled odds ratio 3.83 vs 1.36), to determine AMD status, or in clinic-based samples compared to population-based studies.

The retinal pigment epithelium in health and disease

Retinal pigment epithelial cells (RPE) constitute a simple layer of cuboidal cells that are strategically situated behind the photoreceptor (PR) cells. The inconspicuousness of this monolayer contrasts sharply with its importance [1]. The relationship between the RPE and PR cells is crucial to sight; this is evident from basic and clinical studies demonstrating that primary dysfunctioning of the RPE can result in visual cell death and blindness. RPE cells carry out many functions including the conversion and storage of retinoid, the phagocytosis of shed PR outer segment membrane, the absorption of scattered light, ion and fluid transport and RPE-PR apposition. The magnitude of the demands imposed on this single layer of cells in order to execute these tasks, will become apparent to the reader of this review as will the number of clinical disorders that take origin from these cells.

Age-related macular degeneration: genetic and environmental factors of disease

Age-related macular degeneration (AMD) is the most common cause of visual impairment among the elderly in developed countries, and its prevalence is thus increasing as the population ages; however, treatment options remain limited because the etiology and pathogenesis of AMD are incompletely defined. Recently, much progress has been made in gene discovery and mechanistic studies, which clearly indicate that AMD involves the interaction of multiple genetic and environmental factors. The identification of genes that have a substantial impact on the risk for AMD is not only facilitating the diagnosis and screening of populations at risk but is also elucidating key molecular pathways of pathogenesis. Pharmacogenetic studies of treatment responsiveness among patients with the "wet" form of AMD are increasingly proving to be clinically relevant; pharmacogenetic approaches hold great promise for both identifying patients with the best chance for vision recovery as well as tailoring individualized therapies.

Serum VEGF and CFH in exudative age-related macular degeneration

PURPOSE

To determine serum vascular endothelial growth factor 165 (VEGF165) levels and the association of the complement factor H gene (CFH) Y402H polymorphism in patients with exudative age-related macular degeneration (AMD) in comparison to unaffected control subjects.

METHODS

Sixty-six AMD patients and 66 healthy age- and gender-matched controls were included in this case-control study. The serum VEGF165 was assayed by ELISA (R&D). Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism analysis. Chi-squared tests were used regarding the polymorphism, a t-test regarding the VEGF-levels.

RESULTS

Levels of serum VEGF165 were similar in both groups (p-value = 0.2112). Genotype frequency differed significantly between patients with exudative AMD and the healthy control group (p  =  0.003136). The serum VEGF165 levels were similar irrespective of the presence of the CFH Y402H polymorphism (p  =  0.4113) and independent of the specific genotype (p  =  0.9634).

CONCLUSION

In the present study, exudative AMD is not associated to serum VEGF165 levels; furthermore, our data does not establish a statistical link between VEGF165 and the CFH Y402H polymorphism.

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

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

Association study of complement factor H, C2, CFB, and C3 and age-related macular degeneration in a Han Chinese population

PURPOSE

Genes in the complement pathway, including complement factor H (CFH), C2/BF, and C3, have been reported to be associated with age-related macular degeneration (AMD). Genetic variants, single-nucleotide polymorphisms (SNPs), in these genes were geno-typed for a case-control association study in a mainland Han Chinese population.

METHODS

One hundred and fifty-eight patients with wet AMD, 80 patients with soft drusen, and 220 matched control subjects were recruited among Han Chinese in mainland China. Seven SNPs in CFH and two SNPs in C2, CFB', and C3 were genotyped using the ABI SNaPshot method. A deletion of 84,682 base pairs covering the CFHR1 and CFHR3 genes was detected by direct polymerase chain reaction and gel electrophoresis.

RESULTS

Four SNPs, including rs3753394 (P = 0.0276), rs800292 (P = 0.0266), rs1061170 (P = 0.00514), and rs1329428 (P = 0.0089), in CFH showed a significant association with wet AMD in the cohort of this study. A haplotype containing these four SNPs (CATA) significantly increased protection of wet AMD with a P value of 0.0005 and an odds ratio of 0.29 (95% confidence interval: 0.15-0.60). Unlike in other populations, rs2274700 and rs1410996 did not show a significant association with AMD in the Chinese population of this study. None of the SNPs in CFH showed a significant association with drusen, and none of the SNPs in CFH, C2, CFB, and C3 showed a significant association with either wet AMD or drusen in the cohort of this study. The CFHR1 and CFHR3 deletion was not polymorphic in the Chinese population and was not associated with wet AMD or drusen.

CONCLUSION

This study showed that SNPs rs3753394 (P = 0.0276), rs800292 (P = 0.0266), rs1061170 (P = 0.00514), and rs1329428 (P = 0.0089), but not rs7535263, rs1410996, or rs2274700, in CFH were significantly associated with wet AMD in a mainland Han Chinese population. This study showed that CFH was more likely to be AMD susceptibility gene at Chr.1q31 based on the finding that the CFHR1 and CFHR3 deletion was not polymorphic in the cohort of this study, and none of the SNPs that were significantly associated with AMD in a white population in C2, CFB, and C3 genes showed a significant association with AMD.

Association of complement factor H Y402H polymorphism and age-related macular degeneration in Brazilian patients

PURPOSE

The aim of this study was investigate the association between complement Factor H polymorphism (Y402H) and age-related macular degeneration (AMD) in Brazilian patients.

METHODS

Patients with AMD aged 50 or more and age-matched healthy controls were enrolled in the study. Genomic DNA was isolated from leucocytes of patients and controls; the Y402H polymorphism of complement Factor H gene (CFH) was determined by polymerase chain reaction directed sequencing.

RESULTS

The frequency of 1277C allele of Factor H was 56.30% in patients with AMD compared with 36.51% in controls (p-value=0.001). The genotypic distribution differed significantly between the two groups (1277CC 36.98%, 1277CT 38.65% and 1277TT 24.37% for AMD group; 1277CC 13.16%, 1277CT 46.71% and 1277TT 40.13% for controls, p-value=0.001). The odds ratio for patients with AMD carrying only one 1277C allele was 1.36 and for those carrying two 1277C alleles was 4.63, when compared to the control group.

CONCLUSIONS

These results suggest the Y402H polymorphism of CFH is a risk factor to the development of AMD in Brazilian patients. This is in accordance with findings from the majority of previous study population in Europe and North American.

ARMS2/HTRA1 and CFH polymorphisms are not associated with choroidal neovascularization in highly myopic eyes of the elderly Japanese population

PURPOSE

The purpose of this study was to investigate whether the genetic risk factors of age-related macular degeneration (AMD) are associated with the development of choroidal neovascularization (CNV) in highly myopic eyes of elderly Japanese.

METHODS

Highly myopic elderly Japanese patients with and without CNV were genotyped for three AMD-associated single nucleotide polymorphisms (SNPs), namely rs10490924 (A69S) of ARMS2, rs11200638 of HTRA1, and rs1061170 (Y402H) of complement factor H (CFH), with the TaqMan SNP assay. One hundred and eighty-three unrelated highly myopic (axial lengths>26.00 mm or refractive errors>-6.0 diopters) Japanese patients with CNV who were >or=50 years of age (mean age+/-standard deviation of 62.7+/-6.3 years) and 170 highly myopic patients without CNV who were >or=50 years old (62.3+/-7.1 years) were studied. The differences in the genotypic distributions for the three SNPs between the two groups were tested with the Trend chi2 test, and logistic regression analyses were performed for age and gender adjustment.

RESULTS

No significant difference was detected in the distribution of the three SNPs, rs10490924 (P>0.1), rs11200638 (P>0.1), and rs1061170 (P>0.5), between the two groups even after adjustments for age and gender differences.

CONCLUSION

The genetic risk factors of AMD related to these SNPs do not contribute significantly to the development of CNV in a highly myopic elderly Japanese population.

Complement component C5a activates ICAM-1 expression on human choroidal endothelial cells

PURPOSE

The complement system plays a crucial role in the progression of age-related macular degeneration (AMD). In this study, the authors sought to evaluate the pathophysiologic roles of complement components C3a and C5a in the human choroid in AMD.

METHODS

Human RPE/choroid was assayed for the presence of C3a and C5a receptors (C3aR and C5aR) using RT-PCR and immunohistochemistry. Choroidal endothelial cell migration and proliferation were evaluated in the presence of C5a. Organ cultures of human choroid were incubated in C5a or bovine serum albumin (BSA) followed by quantitative immunohistochemistry and quantitative PCR for ICAM-1. AMD patients and controls were genotyped at SNPs in the C5R1 and C3AR1 genes.

RESULTS

C5aR, but not C3aR, was detected in human choroid. C5a did not promote endothelial cell migration or proliferation. However, choriocapillaris endothelial cells in organ culture responded to C5a by increasing ICAM-1 mRNA and protein. No significant association of SNP genotypes was detected in AMD patients at the C3AR1 and C5R1 genes.

CONCLUSIONS

The generation of C5a peptides may lead to activation of choriocapillaris endothelial cells in AMD. Activation of the choroidal endothelium may affect the progression of AMD by recruitment of monocytes, leading to additional sequelae of AMD pathogenesis.

The role of complement Factor H in age-related macular degeneration: a review

Factor H is a 155kDa sialic acid containing glycoprotein that plays an integral role in the regulation of the complement-mediated immune system that is involved in microbial defense, immune complex processing, and programmed cell death. These events take place primarily in fluid phase and on the cell surface and are particularly important in the context of distinguishing self from non-self. Activation of the complement system occurs within seconds and results in a proteolytic cascade eventually forming the membrane attack complex leading to cell lysis. Factor H protects host cells from injury resulting from unrestrained complement activation. Mutations and SNPs (single nucleotide polymorphisms) in Factor H have been implicated in a variety of human conditions including age-related macular degeneration (AMD), atypical hemolytic uremic syndrome, and membranoproliferative glomuleronephritis type II or dense deposit disease. It should not be surprising that these seemingly unrelated diseases involving mutations in Factor H may share common features. Because the immune process involves, in part, an inflammatory response and common or similar surface antigens, it is also not unexpected to observe features of inflammation, including deposition of bioactive complement fragments such as C3a and C5a, a cellular influx of immune related cells such as lymphocytes, and the potential for multiple organ involvement. We review recent developments in molecular genetics; SNPs, including Y402H; the three-dimensional structure; and mass spectroscopy of Factor H as it relates to the pathogenesis of eye disease. In addition, we discuss the concepts of molecular mimicry, sequestered or hidden antigens, and antigenic cross reactivity, and propose that AMD should not simply be considered to be an eye disease, but rather a systemic vascular disease where the eye has the ability to self regulate a local immune response. Identification of the initial event or inciting antigen has yet to be determined and will significantly advance the understanding of the pathogenesis of AMD.

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.

The molecular basis of human retinal and vitreoretinal diseases

During the last two to three decades, a large body of work has revealed the molecular basis of many human disorders, including retinal and vitreoretinal degenerations and dysfunctions. Although belonging to the group of orphan diseases, they affect probably more than two million people worldwide. Most excitingly, treatment of a particular form of congenital retinal degeneration is now possible. A major advantage for treatment is the unique structure and accessibility of the eye and its different components, including the vitreous and retina. Knowledge of the many different eye diseases affecting retinal structure and function (night and colour blindness, retinitis pigmentosa, cone and cone rod dystrophies, photoreceptor dysfunctions, as well as vitreoretinal traits) is critical for future therapeutic development. We have attempted to present a comprehensive picture of these disorders, including biological, clinical, genetic and molecular information. The structural organization of the review leads the reader through non-syndromic and syndromic forms of (i) rod dominated diseases, (ii) cone dominated diseases, (iii) generalized retinal degenerations and (iv) vitreoretinal disorders, caused by mutations in more than 165 genes. Clinical variability and genetic heterogeneity have an important impact on genetic testing and counselling of affected families. As phenotypes do not always correlate with the respective genotypes, it is of utmost importance that clinicians, geneticists, counsellors, diagnostic laboratories and basic researchers understand the relationships between phenotypic manifestations and specific genes, as well as mutations and pathophysiologic mechanisms. We discuss future perspectives.

Genetic diversity and medicinal drug response in eye care

BACKGROUND

Individual variation in drug response and adverse drug reactions are a serious problem in medicine. This inter-individual variation in drug response could be due to multiple factors such as disease determinants, environmental and genetic factors. Much has been published in the literature in recent years about the potential of pharmacogenetic testing and individualized medicine. The development of personalized medicine is truly an exciting area of research.

METHODS

This pharmacogenetic concept in ophthalmology has existed for more than a century. Although substantial studies that link genetic variants to inter-individual difference in drug response have been reported in several diseases such as cancer and heart diseases, such studies are progressing slowly in the eye field. In this short article, an attempt has been made to summarize these results.

RESULTS

Recently, there have been some small-scale studies that seem to associate the drug response to the genotype of patients in two major eye disorders, namely age-related macular degeneration (ARMD) and glaucoma.

CONCLUSION

These studies are still in their infancy, and do not suggest that a pharmacogenetic basis of drug development is a credible concept and can become reality in the future. This is because most drug responses involve a large number of genes that have several polymorphisms and it is unlikely that any one single gene dictates the drug response. Therefore, a polygenic approach, whole genome single nucleotide polymorphism (SNP) analysis and a molecular understanding of disease itself may provide a better insight in the future about genetic predisposing factors for adverse drug reactions.

Analysis of the indel at the ARMS2 3'UTR in age-related macular degeneration

Controversy remains as to which gene at the chromosome 10q26 locus confers risk for age-related macular degeneration (AMD) and statistical genetic analysis is confounded by the strong linkage disequilibrium (LD) across the region. Functional analysis of related genetic variations could solve this puzzle. Recently, Fritsche et al. reported that AMD is associated with unstable ARMS2 transcripts possibly caused by a complex insertion/deletion (indel; consisting of a 443 bp deletion and an adjacent 54 bp insertion) in its 3'UTR (untranslated region). To validate this indel, we sequenced our samples. We found that this indel is even more complex and is composed of two side-by-side indels separated by 17 bp: (1) 9 bp deletion with 10 bp insertion; (2) 417 bp deletion with 27 bp insertion. The indel is significantly associated with the risk of AMD, but is also in strong LD with the non-synonymous single nucleotide polymorphism rs10490924 (A69S). We also found that ARMS2 is expressed not only in placenta and retina but also in multiple human tissues. Using quantitative PCR, we found no correlation between the indel and ARMS2 mRNA level in human retina and blood samples. The lack of functional effects of the 3'UTR indel, the amino acid substitution of rs10490924 (A69S), and strong LD between them suggest that A69S, not the indel, is the variant that confers risk of AMD. To our knowledge, it is the first time it has been shown that ARMS2 is widely expressed in human tissues. Conclusively, the indel at 3'UTR of ARMS2 actually contains two side-by-side indels. The indels are associated with risk of AMD, but not correlated with ARMS2 mRNA level.

Genetic and functional dissection of HTRA1 and LOC387715 in age-related macular degeneration

A common haplotype on 10q26 influences the risk of age-related macular degeneration (AMD) and encompasses two genes, LOC387715 and HTRA1. Recent data have suggested that loss of LOC387715, mediated by an insertion/deletion (in/del) that destabilizes its message, is causally related with the disorder. Here we show that loss of LOC387715 is insufficient to explain AMD susceptibility, since a nonsense mutation (R38X) in this gene that leads to loss of its message resides in a protective haplotype. At the same time, the common disease haplotype tagged by the in/del and rs11200638 has an effect on the transcriptional upregulation of the adjacent gene, HTRA1. These data implicate increased HTRA1 expression in the pathogenesis of AMD and highlight the importance of exploring multiple functional consequences of alleles in haplotypes that confer susceptibility to complex traits.

An association study of SERPING1 gene and age-related macular degeneration in a Han Chinese population

PURPOSE

Single nucleotide polymorphisms (SNPs) in the complement component 1 inhibitor (SERPING1) gene have been shown to be significantly associated with age-related macular degeneration (AMD) in Caucasian populations. A replication study of an association between these SNPs and AMD in a Chinese population is reported in this study.

METHODS

Six SNPs, including rs2511990, rs1005510, rs11546660, rs2511989, rs2511988, and rs4926 in SERPING1 were genotyped in a Han Chinese subject group using the SNaPshot method of ABI. This subject group was composed of 194 patients with choroidal neovascularization (CNV or wet) AMD, 78 patients with soft drusen, and 285 matched controls. P values of the SNPs were calculated using an additive model. Haplotype frequencies between cases and controls were compared by chi2 analysis. The haplotype analysis was performed using Haploview 4.0.

RESULTS

None of the six SNPs showed significant association with AMD. None of the major haplotypes were observed to be significantly associated with AMD or choroidal neovascularization AMD (CNV) after a stringent Bonferroni correction.

CONCLUSIONS

We demonstrate that SNPs in SERPING1 are not significantly associated with AMD in the mainland Han Chinese population.

Complement Factor H Y403H Polymorphism in the Turkish Population

Complement factor H (CFH) is an important regulator protein of the alternative pathway of the complement system. TheCFHmutations and polymorphisms in CFH have been associated with diseases of the kidney and eye. We investigated the allelic frequency of the most commonCFHpolymorphism, c.1277 T>C (Y402H), in 100 healthy Turkish volunteers from the Antalya Province by direct sequencing of the corresponding genomic region. We found a frequency of 0.65% for the T and 0.35% for the C alleles. The frequency of the TT, CT and CC genotypes was 0.40, 0.49 and 0.11% respectively. Thus, the disease-related C allele has a frequency in Turkey similar to that of Caucasian populations.

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.

Complement factor H gene polymorphisms and Chlamydia pneumoniae infection in age-related macular degeneration

PURPOSE

To investigate the association of the complement factor H gene (CFH)Y402H polymorphism and age-related macular degeneration (AMD) in the Austrian population (Caucasoid descent), and to determine whether there is an association between exposure to Chlamydia pneumoniae-responsible for up to 20% of community-acquired pneumoniae-and the AMD-associated CFHrisk polymorphism.

METHODS

Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism analysis in 75 unrelated AMD patients and compared with 75 healthy, age-matched control subjects. C. pneumoniaeserum IgG was tested by ELISA (R&D) in both groups. The association between the CFHY402H genetic polymorphism and the disease was examined by chi (2)-test and logistic regression.

RESULTS

CFH Y402H genotypefrequencies differed significantly between AMD patients and healthy controls (1277 TT, 22.7%; 1277 TC, 53.3%; and 1277 CC, 22.7% in the AMD group; 1277 TT, 48.0%; 1277 TC, 38.7%; and 1277 CC, 13.3% in the control group) showing a P-value <0.005 (OR:2.920/3.811).No association was found between a positive C. pneumoniae titre and AMD (P=0.192), nor was any association found between C. pneumoniae and the CFH Y402H polymorphism.

CONCLUSIONS

Our data confirm that the CFHY402H polymorphism is a risk factor for AMD in the Austrian population with a higher frequency of the Y402 polymorphism in AMD patients. No association between preceding C. pneumoniaeinfection and diagnosed AMD was found.

Comprehensive analysis of complement factor H and LOC387715/ARMS2/HTRA1 variants with respect to phenotype in advanced age-related macular degeneration

PURPOSE

To examine the interaction of genotypic variation of 16 single-nucleotide polymorphisms (SNP) in the complement factor H (CFH) and LOC387715/ARMS2/HTRA1 loci with clinical characteristics of age-related macular degeneration (AMD).

DESIGN

Retrospective cohort study.

METHODS

Eighty-four patients with neovascular AMD were genotyped using direct sequencing or Sequenom iPLEX technology. The Fisher exact test, Cochran-Mantel-Haenszel statistics, and Mann-Whitney U test were used to assess the effect of each SNP with respect to the following phenotypic manifestations: age at diagnosis, gender, affected eye, study and fellow eye visual acuity at diagnosis and at last follow-up, study eye best acuity during follow-up, presence of large drusen and retinal pigment epithelium (RPE) hyperpigmentation in study and fellow eye, choroidal neovascularization (CNV) angiographic subtype (classic vs occult), CNV size, presence of wet AMD in fellow eye, presence of dry AMD in fellow eye, and smoking history.

RESULTS

Only SNPs in the LOC387715/ARMS2/HTRA1 (10q26) region were associated with disease phenotypes. The polymorphisms rs10664316 and rs1049331 were associated with a decreased risk of poor visual acuity during follow-up and at diagnosis; rs2672598 and rs2293870 were associated with a decreased risk of RPE hyperpigmentation; rs10664316 was associated with a decreased risk of RPE hyperpigmentation with large drusen in the study eye, but an increased risk of large drusen in the fellow eye; rs11200638 was associated with an increased risk of larger CNV; rs10490924 and rs11200638 were associated with younger age of diagnosis.

CONCLUSIONS

Several polymorphisms examined in the LOC387715/ARMS2/HTRA1 locus, but none in the CFH region, correlated with specific phenotypic attributes of AMD.

Genetic basis of inherited macular dystrophies and implications for stem cell therapy

Untreatable hereditary macular dystrophy (HMD) presents a major burden to society in terms of the resulting patient disability and the cost to the healthcare provision system. HMD results in central vision loss in humans sufficiently severe for blind registration, and key issues in the development of therapeutic strategies to target these conditions are greater understanding of the causes of photoreceptor loss and the development of restorative procedures. More effective and precise analytical techniques coupled to the development of transgenic models of disease have led to a prolific growth in the identification and our understanding of the genetic mutations that underly HMD. Recent successes in driving differentiation of pluripotent cells towards specific somatic lineages have led to the development of more efficient protocols that can yield enriched populations of a desired phenotype. Retinal pigmented epithelial cells and photoreceptors derived from these are some of the most promising cells that may soon be used in the treatment of specific HMD, especially since rapid developments in the field of induced pluripotency have now set the stage for the production of patient-derived stem cells that overcome the ethical and methodological issues surrounding the use of embryonic derivatives. In this review we highlight a selection of HMD which appear suitable candidates for combinatorial restorative therapy, focusing specifically on where those photoreceptor loss occurs. This technology, along with increased genetic screening, opens up an entirely new pathway to restore vision in patients affected by HMD.

DNA damage/repair and polymorphism of the hOGG1 gene in lymphocytes of AMD patients

Oxidative stress is thought to play a role in the pathogenesis of age-related macular degeneration (AMD). We determined the extent of oxidative DNA damage and the kinetics of its removal as well as the genotypes of the Ser326Cys polymorphism of the hOGG1 gene in lymphocytes of 30 wet AMD patients and 30 controls. Oxidative DNA damage induced by hydrogen peroxide and its repair were evaluated by the comet assay and DNA repair enzymes. We observed a higher extent of endogenous oxidative DNA damage and a lower efficacy of its repair in AMD patients as compared with the controls. We did not find any correlation between the extent of DNA damage and efficacy of DNA repair with genotypes of the Ser326Cys polymorphism. The results obtained suggest that oxidative DNA damage and inefficient DNA repair can be associated with AMD and the variability of the hOOG1 gene may not contribute to this association.

rs5888 variant of SCARB1 gene is a possible susceptibility factor for age-related macular degeneration

Major genetic factors for age-related macular degeneration (AMD) have recently been identified as susceptibility risk factors, including variants in the CFH gene and the ARMS2 LOC387715/HTRA1locus. Our purpose was to perform a case-control study in two populations among individuals who did not carry risk variants for CFHY402H and LOC387715 A69S (ARMS2), called “study” individuals, in order to identify new genetic risk factors. Based on a candidate gene approach, we analyzed SNP rs5888 of the SCARB1 gene, coding for SRBI, which is involved in the lipid and lutein pathways. This study was conducted in a French series of 1241 AMD patients and 297 controls, and in a North American series of 1257 patients with advanced AMD and 1732 controls. Among these individuals, we identified 61 French patients, 77 French controls, 85 North American patients and 338 North American controls who did not carry the CFH nor ARMS2 polymorphisms. An association between AMD and the SCARB1 gene was seen among the study subjects. The genotypic distribution of the rs5888 polymorphism was significantly different between cases and controls in the French population (p<0.006). Heterozygosity at the rs5888 SNP increased risk of AMD compared to the CC genotypes in the French study population (odds ratio (OR) = 3.5, CI95%: 1.4–8.9, p<0.01) and after pooling the 2 populations (OR = 2.9, 95% CI: 1.6–5.3, p<0.002). Subgroup analysis in exudative forms of AMD revealed a pooled OR of 3.6 for individuals heterozygous for rs5888 (95% CI: 1.7–7.6, p<0.0015). These results suggest the possible contribution of SCARB1, a new genetic factor in AMD, and implicate a role for cholesterol and antioxidant micronutrient (lutein and vitamin E) metabolism in AMD.

Cigarette smoking, oxidative stress, the anti-oxidant response through Nrf2 signaling, and Age-related Macular Degeneration

Age-related Macular Degeneration (AMD) is the leading cause of blindness among the elderly. While excellent treatment has emerged for neovascular disease, treatment for early AMD is lacking due to an incomplete understanding of the early molecular events. Cigarette smoking is the strongest epidemiologic risk factor, yet we do not understand how smoking contributes to AMD. Smoking related oxidative damage during the early phases of AMD may play an important role. This review explores how cigarette smoking and oxidative stress to the retinal pigmented epithelium (RPE) might contribute to AMD, and how the transcription factor Nrf2 can activate a cytoprotective response.

Analyses of single nucleotide polymorphisms and haplotype linkage of LOC387715 and the HTRA1 gene in exudative age-related macular degeneration in a Chinese cohort

PURPOSE

To investigate the effect of single nucleotide polymorphisms (SNPs) and haplotypes in the genes encoding age-related maculopathy susceptibility 2 (LOC387715/ARMS2) and high-temperature requirement A-1 (HTRA1) in a case-control study in a Chinese cohort of individuals with exudative age-related macular degeneration (AMD).

METHODS

We genotyped 2 SNPs, namely, LOC387715 rs10490924 and HTRA1 rs11200638, in 159 exudative AMD patients and 140 age- and sex-matched control subjects. All the four possible haplotypes of these two SNPs were detected. Comparisons of the risk genotypes and risk or protective haplotypes across multiple populations were performed.

RESULTS

Allelic or genotype association tests yielded significant results at P < 0.001. We observed that homozygous risk genotypes (TT in rs10490924 and AA in rs11200638) were more strongly associated with AMD than the heterozygous genotypes (GT in rs10490924 and geographic atrophy in rs11200638) for both SNPs. Comparisons of the odds ratios for genotypes revealed that there is ethnic disparity in AMD prevalence, even within the Chinese population. The haplotype TA, comprising both the SNPs, was identified as an at-risk factor and was significantly associated with AMD, whereas the protective haplotype GG was significantly overrepresented in the controls (P < 0.001). The frequency of the TA haplotype was relatively higher in the Chinese population than in the white population in both groups, whereas the frequency of the GG haplotype was relatively lower in the Chinese controls than in the white and Japanese controls.

CONCLUSION

Both SNPs are significantly associated with exudative AMD in the Chinese cohort and seem to contribute equally to the disease status. A higher frequency of homozygous risk genotypes and risk haplotype and a lower frequency of protective haplotype in the Chinese may be the cause of higher prevalence of exudative AMD in the Chinese than in the whites.

Localization of age-related macular degeneration-associated ARMS2 in cytosol, not mitochondria

PURPOSE

To analyze the relationship between ARMS2 and HTRA1 in the association with age-related macular degeneration (AMD) in an independent case-control dataset and to investigate the subcellular localization of the ARMS2 protein in an in vitro system.

METHODS

Two SNPs in ARMS2 and HTRA1 were genotyped in 685 cases and 269 controls by a genotyping assay. Allelic association was tested by a chi(2) test. A likelihood ratio test (LRT) of full versus reduced models was used to analyze the interaction between ARMS2 and smoking and HTRA1 and smoking, after adjustment for CFH and age. Immunofluorescence and immunoblot were applied to localize ARMS2 in retinal epithelial ARPE-19 cells and COS7 cell transfected by ARMS2 constructs.

RESULTS

Both significantly associated SNP rs10490924 and rs11200638 (P < 0.0001) are in strong linkage disequilibrium (LD; D' = 0.97, r(2) = 0.93) that generates virtually identical association test and odds ratios. In separate logistic regression models, the interaction effect for both smoking with ARMS2 and with HTRA1 was not statistically significant. Immunofluorescence and immunoblot show that both endogenous and exogenous ARMS2 are mainly distributed in the cytosol, not the mitochondria. Compared with the wild-type, ARMS2 A69S is more likely to be associated with the cytoskeleton in COS7 cells.

CONCLUSIONS

The significant associations in ARMS2 and HTRA1 are with polymorphisms in strong LD that confer virtually identical risks, preventing differentiation at the statistical level. ARMS2 was mainly distributed in the cytosol, not in the mitochondrial outer membrane as previously reported, suggesting that ARMS2 may not confer risk to AMD through the mitochondrial pathway.

Complement factor H and LOC387715 gene polymorphisms in a Greek population with age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of severe visual loss among people over 60 years old. The lack of a broadly effective treatment for AMD underscores the need to identify causative biomarkers that could serve as preventive targets. Thus far, two major susceptibility loci for AMD have been identified, CFH T1277C and LOC387715 G270T. The primary goal of the present study was to elucidate whether these polymorphisms are major genetic determinants of AMD in a Greek population.

PATIENTS AND METHODS

A clinic-based, case-control association study was conducted, comprising 100 Greek patients with early and late-stage AMD and 115 independent controls of Caucasian origin. All participants underwent clinical examination including best-corrected visual acuity, intraocular pressure, and dilated fundus examination. Moreover, they were genotyped for CFH T1277C and LOC387715 G270T polymorphisms, by direct sequencing and ARMS PCR, respectively.

RESULTS

The frequency of the CFH 1277C allele was significantly higher in AMD patients in comparison with controls while the odds ratios (ORs) for AMD were 4.4-5.5. Statistical comparison of early and advanced AMD patients, on the basis of CFH genotype, revealed that the CFH 1277C allele was associated with both subgroups when compared with the controls (P < 0.001). When statistical comparison was performed between early and advanced patients on the basis of CFH genotypic frequencies, the CC genotype was found to be more prevalent in advanced AMD patients (P = 0.008, OR = 2.3). The frequency of the LOC387715 270 T allele was higher in AMD patients in comparison with controls (P < 0.04) while the ORs for AMD were 1.4-2. No statistically significant differences were located between the early AMD patients and controls, on the basis of LOC387715 genotype (P = 0.189). On the contrary, the T270G polymorphism was associated with advanced AMD (P = 0.04). Moreover, the TT genotype was more prevalent in patients with advanced AMD (P = 0.011, OR = 1.7) when compared with early AMD patients. Assessment of the combined contribution of CFH T1277C and LOC387715 G270T SNPs showed an independent manner of action of these polymorphisms in the development of the disease.

CONCLUSIONS

The replication of the reported associations of CFH T1277C polymorphism with AMD suggest that the 1277C allele could serve as a high-risk genetic marker for the development of AMD and the progression of the disease to the advanced clinical stage in the Greek population.

Human retinal cadmium accumulation as a factor in the etiology of age-related macular degeneration

Cadmium is a naturally occurring, highly toxic, metallic element. It pollutes the environment as a result of industrial activity and accumulates in human tissues with a long biological half-life. Cadmium content has been demonstrated to increase in human retinal tissues as a function of age and tobacco smokers have approximately twice as much cadmium in retinal tissues than non-smokers. Smoking is also a key environmental risk factor for the retinal disease age-related macular degeneration (AMD). Recent studies have shown that urinary cadmium levels (a measure of Cd body burden) are higher in smokers who have AMD. We now report the Cd measurements in human retinal tissues from eyes afflicted with AMD compared to non-diseased eyes (controls) from age-matched donors. Human donor eyes frozen under argon gas were assessed for AMD severity using color stereoscopic fundus photographs and the Minnesota Grading System. Cadmium, zinc and, copper levels were measured in retinal tissues (neural retina, retinal pigment epithelium and choroid) using inductively coupled plasma mass spectrometry and graphite furnace spectrophotometry and values were normalized to tissue protein levels. Higher Cd levels were found in the neural retina and RPE for eyes afflicted with AMD compared to controls in males, differences were not statistically significant in females. The results indicate that higher retinal cadmium burdens are associated with the presence of AMD at least in males and suggest possible gender differences in the metabolism of metals in the human retina.