Cigarette smoking strongly modifies the association of LOC387715 and age-related macular degeneration

Cigarette smoking and the natural history of age-related macular degeneration: the Beaver Dam Eye Study

PURPOSE

To examine the association of current cigarette smoking and pack-years smoked with the incidence and progression of age-related macular degeneration (AMD) and to examine the interactions of current smoking and pack-years smoked with complement factor H (CFH, rs1061170) and age-related maculopathy susceptibility 2 (ARMS2, rs10490924) genotype.

DESIGN

A longitudinal population-based study of AMD in a representative American community. Examinations were performed every 5 years over a 20-year period.

PARTICIPANTS

A total of 4439 participants in the population-based Beaver Dam Eye Study (BDES).

METHODS

Age-related macular degeneration status was determined from grading retinal photographs. Multi-state models were used to model the relationship of current smoking and pack-years smoked and interactions with CFH and ARMS2 with the incidence and progression of AMD over the entire age range.

MAIN OUTCOME MEASURES

Incidence and progression of AMD over a 20-year period and interactions between current smoking and pack-years smoked with CFH and ARMS2 genotype.

RESULTS

The incidence of early AMD over the 20-year period was 24.4%, and the incidence of late AMD was 4.5%. Current smoking was associated with an increased risk of transitioning from minimal to moderate early AMD. A greater number of pack-years smoked was associated with an increased risk of transitioning from no AMD to minimal early AMD and from severe early AMD to late AMD. Current smoking and a greater number of pack-years smoked were associated with an increased risk of death. There were no statistically significant multiplicative interactions between current smoking or pack-years smoked and CFH or ARMS2 genotype.

CONCLUSIONS

Current smoking and a greater number of pack-years smoked increase the risk of the progression of AMD. This has important health care implications because smoking is a modifiable behavior.

Rare complement factor H variant associated with age-related macular degeneration in the Amish

PURPOSE

Age-related macular degeneration is the leading cause of blindness among the adult population in the developed world. To further the understanding of this disease, we have studied the genetically isolated Amish population of Ohio and Indiana.

METHODS

Cumulative genetic risk scores were calculated using the 19 known allelic associations. Exome sequencing was performed in three members of a small Amish family with AMD who lacked the common risk alleles in complement factor H (CFH) and ARMS2/HTRA1. Follow-up genotyping and association analysis was performed in a cohort of 973 Amish individuals, including 95 with self-reported AMD.

RESULTS

The cumulative genetic risk score analysis generated a mean genetic risk score of 1.12 (95% confidence interval [CI]: 1.10, 1.13) in the Amish controls and 1.18 (95% CI: 1.13, 1.22) in the Amish cases. This mean difference in genetic risk scores is statistically significant (P = 0.0042). Exome sequencing identified a rare variant (P503A) in CFH. Association analysis in the remainder of the Amish sample revealed that the P503A variant is significantly associated with AMD (P = 9.27 × 10(-13)). Variant P503A was absent when evaluated in a cohort of 791 elderly non-Amish controls, and 1456 non-Amish cases.

CONCLUSIONS

Data from the cumulative genetic risk score analysis suggests that the variants reported by the AMDGene consortium account for a smaller genetic burden of disease in the Amish compared with the non-Amish Caucasian population. Using exome sequencing data, we identified a novel missense mutation that is shared among a densely affected nuclear Amish family and located in a gene that has been previously implicated in AMD risk.

CFH (rs1410996), HTRA1 (rs112000638) and ARMS2 (rs10490923) gene polymorphisms are associated with AMD risk in Spanish patients

PURPOSE

Age-related macular degeneration (AMD) is the main cause of legal blindness in the western adult population. We investigated the association between SNPs located in CFH, ARMS2 and HTRA1 and AMD in Spanish patients.

PATIENTS AND METHODS

We obtained peripheral blood samples from 121 patients with a diagnosis of AMD (84 exudative and 37 atrophic) at the Department of Ophthalmology of the University Hospital of Salamanca. We took 91 subjects as a control group. We studied a single nucleotide polymorphism (SNP) in each patient for each of the genes associated with high susceptibility to developing AMD using Real-time PCR with TaqMan probes for CFH and ARMS2 polymorphisms and PCR-RFLP for HTRA1 polymorphism.

RESULTS

We observed a statistically significant difference between patients and controls in the distribution of CFH rs1410996 genotypes, patients homozygous for the C-allele have twice the risk of developing the disease (p = 0.010; OR = 2,176 (1.194-3.964)). The analysis of ARMS2 rs10490923 polymorphism also showed differences in allelic distribution between the case and control groups (p < 0.001). Carriers of the T-allele appear more frequently in the group of patients (p < 0.001; O  = 3.340 (1.848-6.060)). Our results also confirm significant differences in the distribution of HTRA1 rs112000638 polymorphism with an increased representation of the G-allele in the patient's group (p < 0.001; OR = 6.254(3.463-12.280)). Our study also indicates that TTGG ARMS2/HTRA1 (rs10490923/rs112000638) haplotype increases the risk of developing AMD by 9 times.

CONCLUSIONS

Our results show that genotypes of ARMS2 (rs10490923), HTRA1 (rs112000638) and CFH (rs1410996) polymorphisms are related to an increased risk of suffering AMD in Spanish patients.

Generation of induced pluripotent stem cells from conjunctiva

PURPOSE

The objective of this study was to determine whether cells from the conjunctiva could be reprogrammed into induced pluripotent stem (iPS) cells, providing an alternative source of stem cells.

METHODS

We employed a doxycycline-induced reprogrammable mouse strain to generate iPS cells from conjunctiva. The identity of the stem cells was confirmed by reverse transcription polymerase chain reaction (RT-PCR) and immunofluorescence assays. Immunocytochemistry and teratoma assays are established means for scoring stem cell pluripotency. The reprogramming efficiencies of conjunctival cells and ear fibroblasts were compared.

RESULTS

We confirmed the identity of the stem cells and demonstrated expression of pluripotency markers (OCT4, SOX2, NANOG, and SSEA1), as tested by RT-PCR and immunofluorescence assays. In addition, derived iPS cells differentiated successfully into embryoid bodies, and showed teratoma formation when injected into immunodeficient mice. Reprogramming conjunctival tissue is as efficient as reprogramming ear fibroblasts. Conjunctiva-iPS exhibited classic features of embryonic stem (ES) cells with respect to morphology, expression of surface antigens, and pluripotency-associated transcription factors, capacity to differentiate in vitro, and the ability to form all three germ layers in vivo.

CONCLUSION

The present study demonstrated that conjunctival cells, which are readily obtained during the course of many routine conjunctival biopsies and ophthalmic procedures, can be another reliable source of iPS cells.

Predictive value of VEGF A and VEGFR2 polymorphisms in the response to intravitreal ranibizumab treatment for wet AMD

BACKGROUND

To determine whether gene polymorphisms of the vascular endothelial growth factor A (VEGF A) and its receptor (VEGFR) influence the response to a variable-dosing treatment regimen with ranibizumab for age-related macular degeneration.

METHODS

This prospective cohort study included 94 patients (94 eyes) with exudative age-related macular degeneration (AMD) treated with ranibizumab. Patients underwent a 1-year treatment as in the Study of Ranibizumab in Patients with Subfoveal Choroidal Neovascularization Secondary to Age-Related Macular Degeneration (SUSTAIN). Injections were administered monthly during 3 months to all the patients diagnosed of neovascular AMD; reinjections were made when a patient lost 5 letters on the Early Treatment Diabetic Retinopathy Study chart or gained 100 μm in central subfield retinal thickness measured by OCT. Genotypes (VEGF A (rs 699947, rs833061) and VEGFR (rs 2071559)) were analyzed using TaqMan probes. Best-corrected visual acuity (BCVA), subjective improvement, and macular thickness measured with OCT values were compared with VEGF A and VEGFR genotypes. Multiple regression analysis was used to assess the statistical significance.

RESULTS

We found statistically significant differences in allelic distribution of VEGF A rs833061 polymorphism in relation with the response to intravitreal ranibizumab regarding to visual acuity improvement [p = 0,.34; OR: 1.619 (1.098-2.386)]. Patients carrying "protector" genotype CC had higher probability of best corrected visual acuity improvement. When we analyzed VEGF A rs699947 polymorphism we found that patients expressing AA genotype had a higher chance of increasing their best corrected visual acuity [p:0,022; OR 1,532 (1,015-2,313)]. We did not find statistically significant differences reagarding VEGFR rs2071559 polymorphism and treatment response.

CONCLUSIONS

Polymorphisms of VEGF A seem to influence the different response to antiangiogenic treatment in patients with AMD in our population, although further investigation is needed to know the mechanisms of this relationship.

Genetic markers and biomarkers for age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of visual impairment and blindness in the USA. Although the treatment of AMD has evolved to include laser photocoagulation, photodynamic therapy, surgical macular translocation and antiangiogenesis agents, treatment options for advanced AMD are limited. Furthermore, the dry form of AMD, albeit less devastating than the wet form, has even fewer viable treatment options. This review summarizes the various biomarkers of AMD and analyzes whether or not they may one day be exploited to determine risks of disease onset, measure progression of disease or even assess the effects of treatment of AMD. Potential biomarkers are important to identify since some might be utilized to reflect the disease state of a particular patient and to individualize therapy. Although studies have yielded promising results for nutrient and inflammatory biomarkers, these results have been inconsistent. At present, the best available markers of AMD risk are single nucleotide polymorphisms (SNPs). SNPs in complement factor H (CFH) and PLEKHA1/ARMS2/HtrA1 capture a substantial fraction of AMD risk and permit the identification of individuals at high risk of developing AMD.

Chromosome 10q26 locus and age-related macular degeneration: a progress update

Age-related macular degeneration (AMD) is the leading cause of late-onset central vision loss in developed countries. Both genetic and environmental factors contribute to the onset of AMD. Variation at a locus on chromosome 10q26 has been consistently associated with this disease and represents one of the two strongest genetic effects being identified in AMD. At least three genes are located within the bounds of the locus: pleckstrin homology domain containing family A member 1 (PLEKHA1), age-related maculopathy susceptibility 2 (ARMS2) and high-temperature requirement A serine peptidase 1 (HTRA1), all of which are associated with AMD. Due to the strong linkage disequilibrium (LD) across this region, statistical genetic analysis alone is incapable of distinguishing the effect of an individual gene in the locus. Uncertainty remains, however, in regards to which gene is responsible for the linkage and association of the locus with AMD. Investigating functional consequences of the associated variants and related genes tends to be essential to identifying the biologically responsible gene(s) underlying AMD. This review examines the recent progress and current uncertainty on the genetic and functional analyses of the 10q26 locus in AMD with a focus on ARMS2 and HTRA1. A discussion, which entails the possible multi-faceted approaches for pinpointing the gene(s) in the locus underlying the pathogenesis of AMD, is also included.

Detecting rare haplotype-environment interaction with logistic Bayesian LASSO

Two important contributors to missing heritability are believed to be rare variants and gene-environment interaction (GXE). Thus, detecting GXE where G is a rare haplotype variant (rHTV) is a pressing problem. Haplotype analysis is usually the natural second step to follow up on a genomic region that is implicated to be associated through single nucleotide variants (SNV) analysis. Further, rHTV can tag associated rare SNV and provide greater power to detect them than popular collapsing methods. Recently we proposed Logistic Bayesian LASSO (LBL) for detecting rHTV association with case-control data. LBL shrinks the unassociated (especially common) haplotypes toward zero so that an associated rHTV can be identified with greater power. Here, we incorporate environmental factors and their interactions with haplotypes in LBL. As LBL is based on retrospective likelihood, this extension is not trivial. We model the joint distribution of haplotypes and covariates given the case-control status. We apply the approach (LBL-GXE) to the Michigan, Mayo, AREDS, Pennsylvania Cohort Study on Age-related Macular Degeneration (AMD). LBL-GXE detects interaction of a specific rHTV in CFH gene with smoking. To the best of our knowledge, this is the first time in the AMD literature that an interaction of smoking with a specific (rather than pooled) rHTV has been implicated. We also carry out simulations and find that LBL-GXE has reasonably good powers for detecting interactions with rHTV while keeping the type I error rates well controlled. Thus, we conclude that LBL-GXE is a useful tool for uncovering missing heritability.

Critical role of regulator G-protein signaling 10 (RGS10) in modulating macrophage M1/M2 activation

Regulator of G protein signaling 10 (RGS10), a GTPase accelerating protein (GAP) for G alpha subunits, is a negative regulator of NF-κB in microglia. Here, we investigated the role of RGS10 in macrophages, a closely related myeloid-derived cell type. Features of classical versus alternative activation were assessed in Rgs10-/- peritoneal and bone marrow-derived macrophages upon LPS or IL-4 treatments, respectively. Our results showed that Rgs10-/- macrophages produced higher levels of pro-inflammatory cytokines including TNF, IL-1β and IL-12p70 in response to LPS treatment and exerted higher cytotoxicity on dopaminergic MN9D neuroblastoma cells. We also found that Rgs10-/- macrophages displayed a blunted M2 phenotype upon IL-4 priming. Specifically, Rgs10-/- macrophages displayed lower YM1 and Fizz1 mRNA levels as measured by QPCR compared to wild type macrophages upon IL-4 treatment and this response was not attributable to differences in IL-4 receptor expression. Importantly, phagocytic activities of Rgs10-/- macrophages were blunted in response to IL-4 priming and/or LPS treatments. However, there was no difference in chemotaxis between Rgs10-/- and WT macrophages. Our data indicate that Rgs10-/- macrophages displayed dysregulated M1 responses along with blunted M2 alternative activation responses, suggesting that RGS10 plays an important role in determining macrophage activation responses.

Exclusion of influences of ARMS2 polymorphisms on the central visual field in retinitis pigmentosa

PURPOSE

To investigate the effects of polymorphisms of the age-related maculopathy susceptibility 2 (ARMS2) gene on the central visual field defects in retinitis pigmentosa (RP).

SUBJECTS AND METHODS

The visual field was evaluated using the 10-2 Swedish Interactive Threshold Algorithm Fast Program and mean deviation (MD) slope, and regression coefficients of average sensitivity of the central 4 points (Cent4) were compared between each genetic subgroup.

RESULTS

The MD slope (right/left) was as follows: GG, -1.37 ± 2.18/ -0.89 ± 1.15; GT, -0.56 ± 1.40/-0.77 ± 1.04; TT, -0.75 ± 0.64/ -0.38 ± 0.92 dB/year. The Cent4 was as follows: GG, -1.34 ± 2.37/-1.60 ± 3.21; GT, -1.15 ± 2.08/1.07 ± 1.80; TT, -1.20 ± 0.91/-0.65 ± 1.37 dB/year. No significant differences in the degree of progression were observed when comparing groups.

CONCLUSIONS

These data suggest that polymorphisms of the ARMS2 do not modify the progression of the central field of vision in RP patients.

Regulatory regions of the paraoxonase 1 (PON1) gene are associated with neovascular age-related macular degeneration (AMD)

Physiological stress response and oxidative damage are factors for aging processes and, as such, are thought to contribute to neovascular age-related macular degeneration (AMD). Paraoxonase 1 (PON1) is an enzyme that plays an important role in oxidative stress and aging. We investigated association of DNA sequence variants (SNP) within the upstream regulatory region of the PON1 gene with neovascular AMD in 305 patients and 288 controls. Four of the seven tested SNPs (rs705379, rs705381, rs854573, and rs757158) were more frequently found in AMD patients compared to controls (P = 0.0099, 0.0295, 0.0121, and 0.0256, respectively), and all but one (SNP rs757158) are in linkage disequilibrium. Furthermore, haplotype TGGCCTC conferred protection (odds ratio (OR) = 0.76, (CI) = 0.60-0.97) as it was more frequently found in control individuals, while haplotype CGATGCT increased the risk (OR = 1.55, CI = 1.09-2.21) for AMD. These results were also reflected when haplotypes for the untranscribed and the 5'untranslated regions (5'UTR) were analyzed separately. To assess haplotype correlation with levels of gene expression, the three SNPs within the 5'UTR were tested in a luciferase reporter assay. In retinal pigment epithelium-derived ARPE19 cells, we were able to measure significant differences in reporter levels, while this was not observed in kidney-derived HEK293 cells. The presence of the risk allele A (SNP rs705381) caused an increase in luciferase activity of approximately twofold. Our data support the view that inflammatory reactions mediated through anti-oxidative activity may be relevant to neovascular age-related macular degeneration.

Functional effect of Saffron supplementation and risk genotypes in early age-related macular degeneration: a preliminary report

Background

To determine whether the functional effects of oral supplementation with Saffron, a natural compound that proved to be neuroprotective in early age-related macular degeneration, are influenced by complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) risk genotypes.

Methods

Thirty-three early AMD patients, screened for CFH (rs1061170) and ARMS2 (rs10490924) polymorphisms and receiving Saffron oral supplementation (20 mg/day) over an average period of treatment of 11 months (range, 6–12), were longitudinally evaluated by clinical examination and focal electroretinogram (fERG)-derived macular (18°) flicker sensitivity estimate. fERG amplitude and macular sensitivity, the reciprocal value of the estimated fERG amplitude threshold, were the main outcome measures.

Results

After three months of supplementation, mean fERG amplitude and fERG sensitivity improved significantly when compared to baseline values (p < 0.01). These changes were stable throughout the follow-up period. No significant differences in clinical and fERG improvements were observed across different CFH or ARMS2 genotypes.

Conclusions

The present results indicate that the functional effect of Saffron supplementation in individual AMD patients is not related to the major risk genotypes of disease.

Genetic factors in nonsmokers with age-related macular degeneration revealed through genome-wide gene-environment interaction analysis

Relatively little is known about the interaction between genes and environment in the complex etiology of age-related macular degeneration (AMD). This study aimed to identify novel factors associated with AMD by analyzing gene-smoking interactions in a genome-wide association study of 1207 AMD cases and 686 controls of Caucasian background with genotype data on 668,238 single nucleotide polymorphisms (SNPs) after quality control. Participants' history of smoking at least 100 cigarettes lifetime was determined by a self-administered questionnaire. SNP associations modeled the effect of the minor allele additively on AMD using logistic regression, with adjustment for age, sex, and ever/never smoking. Joint effects of SNPs and smoking were examined comparing a null model containing only age, sex, and smoking against an extended model including genotypic and interaction terms. Genome-wide significant main effects were detected at three known AMD loci: CFH (P = 7.51×10(-30) ), ARMS2 (P = 1.94×10(-23) ), and RDBP/CFB/C2 (P = 4.37×10(-10) ), while joint effects analysis revealed three genomic regions with P < 10(-5) . Analyses stratified by smoking found genetic associations largely restricted to nonsmokers, with one notable exception: the chromosome 18q22.1 intergenic SNP rs17073641 (between SERPINB8 and CDH7), more strongly associated in nonsmokers (OR = 0.57, P = 2.73 × 10(-5) ), with an inverse association among smokers (OR = 1.42, P = 0.00228), suggesting that smoking modifies the effect of some genetic polymorphisms on AMD risk.

Pharmacogenetics of the treatment response of age-related macular degeneration with ranibizumab and bevacizumab

INTRODUCTION

Age-related macular degeneration is a major cause of blindness among people aged 50 and older in industrialized countries. Anti-VEGF therapy has been tremendously successful in the treatment of neovascular macular degeneration. Examining the pharmacogenetics of patients' response to the anti-VEGF molecules could allow for a tailored treatment strategy based on patients' underlying genetics rather than the "one-size fits all" approach currently used.

METHODS

Review of the English literature for papers examining the pharmacogenetics of treatment response of neovascular macular degeneration to either ranibizumab or bevacizumab. Polymorphisms in CFH, ARMS2, HTRA1 and VEGF A were examined and reviewed.

RESULTS

Patients with the high-risk CC genotype in complement factor H (CFH) had a worse response to therapy with ranibizumab and bevacizumab. No clear trends were found with ARMS2, HTRA1 and VEGF A.

CONCLUSIONS

The goal of personalized medicine is to craft a treatment program that is ideally suited to an individual patient's disease and genetic make-up rather than simply what works for a large population who share similar disease characteristics. Continued research is needed to achieve this goal for the treatment of age-related macular degeneration.

RAD51 gene is associated with advanced age-related macular degeneration in Chinese population

OBJECTIVES

This study aims to investigate whether variations in RAD51, B3GALTL, TNFRSF10A and REST-C4ORF14-POLR2B-IGFBP7 are associated with advanced forms of age-related macular degeneration (AMD) in Chinese population.

DESIGN AND METHODS

A total of 119 Chinese patients with AMD and 99 control individuals were recruited. Genomic DNA was extracted from peripheral blood leukocytes. Seven single nucleotide polymorphisms (SNPs) from CFH, HTRA1, RAD51, B3GALTL, TNFRSF10A and REST-C4ORF14-POLR2B-IGFBP7 were genotyped by polymerase chain reaction (PCR) followed by allele-specific restriction enzyme digestion or SNaPshot.

RESULTS

Rs10483810 in RAD51 was significantly associated with advanced AMD (P=0.045). Compared with the wild-type genotype GG, the odds ratio for the risk of advanced AMD was 4.92 (95% confidence interval: 1.04-23.36) for the heterozygous TG genotype. Moreover, the GT genotype at rs10483810 confers significantly increased risk of bilateral AMD compared to unilateral AMD (OR=12.04, 95% CI: 2.50-57.69, P=0.002). Rs13278062 in TNFRSF10A, rs1713985 in REST-C4ORF14-POLR2B-IGFBP7 and rs9542236 in B3GALTL were not found to be associated with AMD (all P>0.05).

CONCLUSION

Our data suggested that the risk allele T of rs10483810 in RAD51 gene is associated with an increased risk of advanced AMD, especially bilateral AMD, in Chinese population.

Alternative complement pathway deficiency ameliorates chronic smoke-induced functional and morphological ocular injury

BACKGROUND

Age-related macular degeneration (AMD), a complex disease involving genetic variants and environmental insults, is among the leading causes of blindness in Western populations. Genetic and histologic evidence implicate the complement system in AMD pathogenesis; and smoking is the major environmental risk factor associated with increased disease risk. Although previous studies have demonstrated that cigarette smoke exposure (CE) causes retinal pigment epithelium (RPE) defects in mice, and smoking leads to complement activation in patients, it is unknown whether complement activation is causative in the development of CE pathology; and if so, which complement pathway is required.

METHODS

Mice were exposed to cigarette smoke or clean, filtered air for 6 months. The effects of CE were analyzed in wildtype (WT) mice or mice without a functional complement alternative pathway (AP; CFB(-/-) ) using molecular, histological, electrophysiological, and behavioral outcomes.

RESULTS

CE in WT mice exhibited a significant reduction in function of both rods and cones as determined by electroretinography and contrast sensitivity measurements, concomitant with a thinning of the nuclear layers as measured by SD-OCT imaging and histology. Gene expression analyses suggested that alterations in both photoreceptors and RPE/choroid might contribute to the observed loss of function, and visualization of complement C3d deposition implies the RPE/Bruch's membrane (BrM) complex as the target of AP activity. RPE/BrM alterations include an increase in mitochondrial size concomitant with an apical shift in mitochondrial distribution within the RPE and a thickening of BrM. CFB(-/-) mice were protected from developing these CE-mediated alterations.

CONCLUSIONS

Taken together, these findings provide clear evidence that ocular pathology generated in CE mice is dependent on complement activation and requires the AP. Identifying animal models with RPE/BrM damage and verifying which aspects of pathology are dependent upon complement activation is essential for developing novel complement-based treatment approaches for the treatment of AMD.

Risk alleles in CFH and ARMS2 and the long-term natural history of age-related macular degeneration: the Beaver Dam Eye Study

OBJECTIVE

To describe the relationships of risk alleles in complement factor H (CFH, rs1061170) and age-related maculopathy susceptibility 2 (ARMS2, rs10490924) to the incidence and progression of age-related macular degeneration (AMD) during a 20-year period.

METHODS

There were 4282 persons aged 43 to 86 years at the baseline examination in 1988-1990 enrolled in a population-based cohort study who participated in at least 1 examination spaced 5 years apart during a 20-year period and had gradable fundus photographs for AMD and genotype information on CFH and ARMS2. Low, intermediate, and high genetic risk for AMD was defined by the presence of 0 to 1, 2, or 3 to 4 risk alleles for CFH and ARMS2, respectively. Multistate models were used to estimate the progression of AMD throughout the entire age range.

RESULTS

There were 2820 (66%), 1129 (26%), and 333 persons (8%) with low, intermediate, and high genetic risk for AMD, respectively. The 5-year incidences of early and late AMD were 9.1% and 1.6%, respectively, and increased with age but did not differ significantly by sex. Using the multistate model, of persons aged 45 years with no AMD in the low, intermediate, and high AMD genetic risk groups, 33.0%, 39.9%, and 46.5%, respectively, were estimated to develop early AMD, and 1.4%, 5.2%, and 15.3% were estimated to develop late AMD by age 80 years.

CONCLUSIONS

These population-based data provide estimates of the long-term risk of the incidence and progression of AMD and its lesions by age and genetic risk alleles for CFH and ARMS2. They also show that when early AMD is present, knowing the phenotype contributes more to risk assessment than knowing the genetic risk based on these 2 AMD genes.

Prevalence and genomic association of reticular pseudodrusen in age-related macular degeneration

PURPOSE

To survey the prevalence of reticular pseudodrusen in late age-related macular degeneration (AMD) using multiple imaging methods, and to investigate the association between reticular pseudodrusen and polymorphisms in complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) genes.

DESIGN

Retrospective case series.

METHODS

This study included 216 consecutive patients with late AMD (typical AMD, polypoidal choroidal vasculopathy [PCV], retinal angiomatous proliferation [RAP], or geographic atrophy). Eyes were assessed for reticular pseudodrusen using the blue channel of color fundus photography, infrared reflectance, fundus autofluorescence, and spectral-domain optical coherence tomography. The major AMD-associated single nucleotide polymorphisms (CFH Y402 rs1061170, CFH I62V rs800292, and ARMS2 A69S rs10490924) were genotyped.

RESULTS

Forty-nine eyes of 30 patients had a reticular pattern in ≥2 imaging modalities and were diagnosed with reticular pseudodrusen. Of these, 16 had bilateral late AMD, whereas 32 of 186 patients without reticular pseudodrusen had bilateral late AMD (P < .001). The prevalence of reticular pseudodrusen was 83% in RAP, 50% in geographic atrophy, 9% in typical AMD, and 2% in PCV. The frequency of the T allele in ARMS2 A69S in patients with and without reticular pseudodrusen was 78.6% and 59.9%, respectively (P=.007).

CONCLUSIONS

The prevalence of reticular pseudodrusen was low in PCV cases. About 50% of patients with reticular pseudodrusen had bilateral late AMD. The connection of ARMS2 risk allele and reticular pseudodrusen was confirmed in a Japanese population.

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.

Influence of CFH, HTRA1 and ARMS2 haplotype polymorphisms in the development of age-related macular disease

OBJECTIVE

To demonstrate genetic influence on the onset of age-related macular disease (AMD), analyzing genotype distribution of haplotypes, including polymorphisms of genes with proved relationships with AMD risk (CFH, ARMS2, HTRA1) in patients with AMD and in healthy people.

METHODS

We took 101 consecutive patients with an AMD diagnosis following Wisconsin international classification. For our control group, we took 91 patients without AMD or any significant macular changes. We analyzed CFH rs1410996, ARMS2rs 10940923 polymorphisms using real time PCR with taqman probes, and HTRA1 -625 using restriction endonuclease digestion. We studied haplotypes by simultaneously combining genotypes which, in previous studies, had been shown to have relationship with AMD (CFH, ARMS2, HTRA1) in patients with AMD and healthy people.

RESULTS

There was a statistically significant higher proportion of patients with AMD simultaneously expressing CFH GG (rs1410996) and ARMS2 TT (rs10940923) (P=.037; OR: 7.742 [1.010-63.156]); ARMS2 TT (rs10940923) and HTRA1-625 TT (P=.001; OR: 9.006 [2.019-40.168]) and CFH GG (rs1410996), ARMS2 TT (rs1040923) and HTRA1 -625 GG (P=.043; OR: 6.702 [1.003-55.565]) genotypes.

CONCLUSIONS

Haplotypes which combine "risk genotypes", demonstrated in previous studies, of our analyzed polymorphisms are more frequent in patients with AMD than in the control group, and they seem to increase the risk of suffering the disease in our population.

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.

The ARMS2 A69S variant and bilateral advanced age-related macular degeneration

PURPOSE

To identify genetic associations between specific risk genes and bilateral advanced age-related macular degeneration (AMD) in a retrospective, observational case series of 1,003 patients: 173 patients with geographic atrophy in at least 1 eye and 830 patients with choroidal neovascularization in at least 1 eye.

METHODS

Patients underwent clinical examination and fundus photography. The images were subsequently graded using a modified grading system adapted from the Age-Related Eye Disease Study. Genetic analysis was performed to identify genotypes at 4 AMD-associated variants (ARMS2 A69S, CFH Y402H, C3 R102G, and CFB R32Q) in these patients.

RESULTS

There were no statistically significant relationships between clinical findings and genotypes at CFH, C3, and CFB. The genotype at ARMS2 correlated with bilateral advanced AMD using a variety of comparisons: unilateral geographic atrophy versus bilateral geographic atrophy (P = 0.08), unilateral choroidal neovascularization versus bilateral choroidal neovascularization (P = 9.0 × 10(-8)), and unilateral late AMD versus bilateral late AMD (P = 5.9 × 10(-8)).

CONCLUSION

In this series, in patients with geographic atrophy or choroidal neovascularization in at least 1 eye, the ARMS2 A69S substitution strongly associated with geographic atrophy or choroidal neovascularization in the fellow eye. The ARMS2 A69S substitution may serve as a marker for bilateral advanced AMD.

Mechanism of inflammation in age-related macular degeneration

Age-related macular degeneration (AMD) is a multifactorial disease that represents the most common cause of irreversible visual impairment among people over the age of 50 in Europe, the United States, and Australia, accounting for up to 50% of all cases of central blindness. Risk factors of AMD are heterogeneous, mainly including increasing age and different genetic predispositions, together with several environmental/epigenetic factors, that is, cigarette smoking, dietary habits, and phototoxic exposure. In the aging retina, free radicals and oxidized lipoproteins are considered to be major causes of tissue stress resulting in local triggers for parainflammation, a chronic status which contributes to initiation and/or progression of many human neurodegenerative diseases such as AMD. Experimental and clinical evidences strongly indicate the pathogenetic role of immunologic processes in AMD occurrence, consisting of production of inflammatory related molecules, recruitment of macrophages, complement activation, microglial activation and accumulation within those structures that compose an essential area of the retina known as macula lutea. This paper reviews some attractive aspects of the literature about the mechanisms of inflammation in AMD, especially focusing on those findings or arguments more directly translatable to improve the clinical management of patients with AMD and to prevent the severe vision loss caused by this disease.

Polymorphisms in ARMS2/HTRA1 and complement genes and age-related macular degeneration in India: findings from the INDEYE study

PURPOSE

Association between genetic variants in complement factor H (CFH), factor B (CFB), component 2 (C2), and in the ARMS2/HTRA1 region with age-related macular degeneration (AMD) comes mainly from studies of European ancestry and case-control studies of late-stage disease. We investigated associations of both early and late AMD with these variants in a population-based study of people aged 60 years and older in India.

METHODS

Fundus images were graded using the Wisconsin Age-Related Maculopathy Grading System and participants assigned to one of four mutually exclusive stages based on the worse affected eye (0 = no AMD, 1-3 = early AMD, 4 = late AMD). Multinomial logistic regression was used to derive risk ratios (RR) accounting for sampling method and adjusting for age, sex, and study center.

RESULTS

Of 3569 participants, 53.2% had no signs of amd, 45.6% had features of early amd, and 1.2% had late amd. CFH (RS1061170), C2 (RS547154), OR CFB (RS438999) was not associated with early or late AMD. In the ARMS2 locus, RS10490924 was associated with both early (adjusted RR 1.22, 95% confidence interval [CI]: 1.13-1.33, P < 0.0001) and late AMD (adjusted RR 1.81, 95% CI: 1.15-2.86; P = 0.01); rs2672598 was associated only with early AMD (adjusted RR 1.12, 95% CI: 1.02-1.23; P = 0.02); rs10490923 was not associated with early or late AMD.

CONCLUSIONS

Two variants in ARMS2/HTRA1 were associated with increased risk of early AMD, and for one of these, the increased risk was also evident for late AMD. The study provides new insights into the role of these variants in early stages of AMD in India.

Genetics of immunological and inflammatory components in age-related macular degeneration

Age-related macular degeneration (AMD), affecting 30 to 50 million elder individuals worldwide, is a disease affecting the macular retina and choroid that can lead to irreversible central vision loss and blindness. Recent findings support a role for immunologic processes in AMD pathogenesis, including generation of inflammatory related molecules in the Bruch's membrane, recruitment of macrophages, complement activation, microglial activation and accumulation in the macular lesions. Pro-inflammatory effects of chronic inflammation and oxidative stress can result in abnormal retinal pigment epithelium, photoreceptor atrophy and choroidal neovascularization. The associations of immunological and inflammatory genes, in particular the genes related to innate immunity with AMD support the involvement of various immunological pathways in the AMD pathogenesis. We review the literature on the involvements of inflammatory genes in AMD, highlight recent genetic discoveries, and discuss the potential application of such knowledge in the management of patients with AMD.

RGS10 exerts a neuroprotective role through the PKA/c-AMP response-element (CREB) pathway in dopaminergic neuron-like cells

Regulator of G-protein signaling-10 (RGS10) is a GTPase activating protein for Gαi/q/z subunits that is highly expressed in the immune system and in a broad range of brain regions including the hippocampus, striatum, dorsal raphe, and ventral midbrain. Previously, we reported that RGS10-null mice display increased vulnerability to chronic systemic inflammation-induced degeneration of nigral dopaminergic (DA) neurons. Given that RGS10 is expressed in DA neurons, we investigated the extent to which RGS10 regulates cell survival under conditions of inflammatory stress. Because of the inherent limitations associated with use of primary DA neurons for biochemical analyses, we employed a well-characterized ventral mesencephalon DA neuroblastoma cell line (MN9D) for our studies. We found that stable over-expression of RGS10 rendered them resistant to TNF-induced cytotoxicity; whereas MN9D cells expressing mutant RGS10-S168A (which is resistant to phosphorylation by protein kinase A at a serine residue that promotes its nuclear translocation) showed similar sensitivity to TNF as the parental MN9D cells. Using biochemical and pharmacologic approaches, we identified protein kinase A and the downstream phospho-cAMP response element-binding signaling pathway (and ruled out ERK 1/2, JNK, and NFkB) as key mediators of the neuroprotective effect of RGS10 against inflammatory stress.

Macular pigment optical density in wet age-related macular degeneration among Indians

PURPOSE

To estimate the value of macular pigment optical density (MPOD) in adult south Indian population with wet age-related macular degeneration (AMD).

METHODS

A total of 33 patients with wet AMD and 29 age-matched controls >50 years of age underwent MPOD measurement with the macular densitometer. The patients were also tested for their dietary intake of carotenoids, smoking history, and lifetime UV exposure.

RESULTS

The mean MPOD values in the Indian population with wet AMD was 0.23 (95% CI: 0.18-0.29) vs control was 0.43 (95% CI: 0.37-0.49), P<0.0001, at 0.5° eccentricity. Ex-smokers had a lower MPOD than non-smokers (0.16 (0.09-0.23) vs 0.28 (0.22-0.34), P=0.026) and the lowest level of carotenoids intake had 48% lower MPOD than the highest level (0.14 (0.08-0.21) vs 0.33 (0.24-0.43), P=0.012). There was no significant age-related decline or gender variation in MPOD.

CONCLUSION

This study establishes the MPOD in adult Indian population with wet AMD, with a lack of macular pigment in association with wet AMD.

Genetic insights into age-related macular degeneration: controversies addressing risk, causality, and therapeutics

Age-related macular degeneration (AMD) is a common condition among the elderly population that leads to the progressive central vision loss and serious compromise of quality of life for its sufferers. It is also one of the few disorders for whom the investigation of its genetics has yielded rich insights into its diversity and causality and holds the promise of enabling clinicians to provide better risk assessments for individuals as well as to develop and selectively deploy new therapeutics to either prevent or slow the development of disease and lessen the threat of vision loss. The genetics of AMD began initially with the appreciation of familial aggregation and increase risk and expanded with the initial association of APOE variants with the disease. The first major breakthroughs came with family-based linkage studies of affected (and discordant) sibs, which identified a number of genetic loci and led to the targeted search of the 1q31 and 10q26 loci for associated variants. Three of the initial four reports for the CFH variant, Y402H, were based on regional candidate searches, as were the two initial reports of the ARMS2/HTRA1 locus variants. Case-control association studies initially also played a role in discovering the major genetic variants for AMD, and the success of those early studies have been used to fuel enthusiasm for the methodology for a number of diseases. Until 2010, all of the subsequent genetic variants associated with AMD came from candidate gene testing based on the complement factor pathway. In 2010, several large-scale genome-wide association studies (GWAS) identified genes that had not been previously identified. Much of this historical information is available in a number of recent reviews (Chen et al., 2010b; Deangelis et al., 2011; Fafowora and Gorin, 2012b; Francis and Klein, 2011; Kokotas et al., 2011). Large meta analysis of AMD GWAS has added new loci and variants to this collection (Chen et al., 2010a; Kopplin et al., 2010; Yu et al., 2011). This paper will focus on the ongoing controversies that are confronting AMD genetics at this time, rather than attempting to summarize this field, which has exploded in the past 5 years.

How does the macula protect itself from oxidative stress?

Oxidative stress has been hypothesized to contribute to the development of age-related macular degeneration (AMD), the most common cause of blindness in the United States. At present, there is no treatment for early disease. Reactive oxygen species (ROS) play a physiological role in the retinal pigment epithelium (RPE), a key cell type in this disease, but with excessive ROS, oxidative damage or excessive innate immune system activation can result. The RPE has developed a robust antioxidant system driven by the transcription factor Nrf2. Impaired Nrf2 signaling can lead to oxidative damage or activate the innate immune response, both of which can lead to RPE apoptosis, a defining change in AMD. Several mouse models simulating environmental stressors or targeting specific antioxidant enzymes such as superoxide dismutase or Nrf2, have simulated some of the features of AMD. While ROS are short-lived, oxidatively damaged molecules termed oxidation specific epitopes (OSEs), can be long-lived and a source of chronic stress that activates the innate immune system through pattern recognition receptors (PRRs). The macula accumulates a number of OSEs including carboxyethylpyrrole, malondialdehyde, 4-hydroxynonenal, and advanced glycation endproducts, as well as their respective neutralizing PRRs. Excessive accumulation of OSEs results in pathologic immune activation. For example, mice immunized with the carboxyethylpyrrole develop cardinal features of AMD. Regulating ROS in the RPE by modulating antioxidant systems or neutralizing OSEs through an appropriate innate immune response are potential modalities to treat or prevent early AMD.

Single-marker family-based association analysis conditional on parental information

Family-based designs have been commonly used in association studies. Different family structures such as extended pedigrees and nuclear families, including parent-offspring triads and families with multiple affected siblings (multiplex families), can be ascertained for family-based association analysis. Flexible association tests that can accommodate different family structures have been proposed. The pedigree disequilibrium test (PDT) (Am J Hum Genet 67:146-154, 2000) can use full genotype information from general (possibly extended) pedigrees with one or multiple affected siblings but requires parental genotypes or genotypes of unaffected siblings. On the other hand, the association in the presence of linkage (APL) test (Am J Hum Genet 73:1016-1026, 2003) is restricted to nuclear families with one or more affected siblings but can infer missing parental genotypes properly by accounting for identity-by-descent (IBD) parameters. Both the PDT and APL are powerful association tests in the presence of linkage and can be used as complementary tools for association analysis. This chapter introduces these two tests and compares their properties. Recommendations and notes for performing the tests in practice are provided.