Anita Agarwal

Genetic variants near TIMP3 and high-density lipoprotein–associated loci influence susceptibility to age-related macular degeneration

We executed a genome-wide association scan for age-related macular degeneration (AMD) in 2,157 cases and 1,150 controls. Our results validate AMD susceptibility loci near CFH (P < 10−75), ARMS2 (P < 10−59), C2/CFB (P < 10−20), C3 (P < 10−9), and CFI (P < 10−6). We compared our top findings with the Tufts/Massachusetts General Hospital genome-wide association study of advanced AMD (821 cases, 1,709 controls) and genotyped 30 promising markers in additional individuals (up to 7,749 cases and 4,625 controls). With these data, we identified a susceptibility locus near TIMP3 (overall P = 1.1 × 10−11), a metalloproteinase involved in degradation of the extracellular matrix and previously implicated in early-onset maculopathy. In addition, our data revealed strong association signals with alleles at two loci (LIPC, P = 1.3 × 10−7; CETP, P = 7.4 × 10−7) that were previously associated with high-density lipoprotein cholesterol (HDL-c) levels in blood. Consistent with the hypothesis that HDL metabolism is associated with AMD pathogenesis, we also observed association with AMD of HDL-c—associated alleles near LPL (P = 3.0 × 10−3) and ABCA1 (P = 5.6 × 10−4). Multilocus analysis including all susceptibility loci showed that 329 of 331 individuals (99%) with the highest-risk genotypes were cases, and 85% of these had advanced AMD. Our studies extend the catalog of AMD associated loci, help identify individuals at high risk of disease, and provide clues about underlying cellular pathways that should eventually lead to new therapies.

Cigarette Smoking Strongly Modifies the Association of LOC387715 and Age-Related Macular Degeneration

We used iterative association mapping to identify a susceptibility gene for age-related macular degeneration (AMD) on chromosome 10q26, which is one of the most consistently implicated linkage regions for this disorder. We employed linkage analysis methods, followed by family-based and case-control association analyses, using two independent data sets. To identify statistically the most likely AMD-susceptibility allele, we used the Genotype-IBD Sharing Test (GIST) and conditional haplotype analysis. To incorporate the two most important known AMD risk factors--smoking and the Y402H variant of the complement factor H gene (CFH)--we used logistic regression modeling to test for gene-gene and gene-environment interactions in the case-control data set and used the ordered-subset analysis to account for genetic linkage heterogeneity in the family-based data set. Our results strongly implicate a coding change (Ala69Ser) in the LOC387715 gene as the second major identified AMD-susceptibility allele, confirming earlier suggestions. This variants effect on AMD is statistically independent of CFH and is of similar magnitude to the effect of Y402H. The overall effect is driven primarily by a strong association in smokers, since we observed significant evidence for a statistical interaction between the LOC387715 variant and a history of cigarette smoking. This gene-environment interaction is supported by statistically independent family-based and case-control analysis methods. We estimate that CFH, LOC387715, and cigarette smoking together explain 61% of the population-attributable risk (PAR) of AMD. The adjusted PAR percentage estimates are 20% for smoking, 36% for LOC387715, and 43% for CFH. We demonstrate, for the first time, that a genetic susceptibility coupled with a modifiable lifestyle factor such as cigarette smoking confers a significantly higher risk of AMD than either factor alone.

Age-related maculopathy: a genomewide scan with continued evidence of susceptibility loci within the 1q31, 10q26, and 17q25 regions.

Age-related maculopathy (ARM), or age-related macular degeneration, is one of the most common causes of visual impairment in the elderly population of developed nations. In a combined analysis of two previous genomewide scans that included 391 families, containing up to 452 affected sib pairs, we found linkage evidence in four regions: 1q31, 9p13, 10q26, and 17q25. We now have added a third set of families and have performed an integrated analysis incorporating 530 families and up to 736 affected sib pairs. Under three diagnostic models, we have conducted linkage analyses using parametric (heterogeneity LOD [HLOD] scores under an autosomal dominant model) and nonparametric (Sall statistic) methods. There is ongoing evidence of susceptibility loci within the 1q31, 10q26, and 17q25 regions. If we treat the third set of families as a replication set, then two regions (10q26 and 17q25) are replicated, with LOD scores >1.0. If we pool all our data together, then four regions (1q31, 2q14.3, 10q26, and 17q25) show HLOD or Sall scores > or =2.0. Within the 1q31 region, we observed an HLOD of 2.72 (genomewide P=.061) under our least stringent diagnostic model, whereas the 17q25 region contained a maximal HLOD of 3.53 (genomewide P=.007) under our intermediate diagnostic model. We have evaluated our results with respect to the findings from several new independent genomewide linkage studies and also have completed ordered subset analyses (OSAs) with apolipoprotein E alleles, smoking history, and age at onset as stratifying covariates. The OSAs generate the interesting hypothesis that the effect of smoking on the risk of ARM is accentuated by a gene in the 10q26 region--a region implicated by four other studies.

Presumed tubercular serpiginouslike choroiditis: clinical presentations and management.

PURPOSE Choroiditis, choroidal tubercles, and tuberculomas are well known ocular manifestations of systemic tuberculosis. The present series aimed to report the occurrence of serpiginouslike choroiditis of presumed tubercular origin. DESIGN Retrospective, noncomparative, interventional case series. PARTICIPANTS Eleven eyes in seven consecutive patients with a diagnosis of choroidal tuberculosis simulating serpiginous choroiditis were studied between 1997 and 2000. TESTING AND INTERVENTION: All patients had their fundus photographs taken at the time of initial presentation as well as during follow-up. All patients underwent a Mantoux skin test and chest radiography. In addition, five patients had their aqueous or vitreous humor subjected to polymerase chain reaction (PCR) for Mycobacterium tuberculosis. Sputum examination, biopsy, or both were carried out whenever recommended by the pulmonologist. Systemic antituberculosis chemotherapy was instituted in combination with treatment for ocular inflammation. MAIN OUTCOME MEASURE Therapeutic response and visual improvement. RESULTS There were five men and two women ranging in age from 17 to 32 years. Clinical presentations included three morphologic variants; multifocal progressive choroiditis showing wavelike progression to confluent, diffuse lesions resembling serpiginous choroiditis (three eyes); diffuse choroiditis characterized by diffuse plaquelike choroiditis with an amoeboid pattern suggestive of serpiginous choroiditis at initial presentation (four eyes); and mixed variety where opposite eyes had mixed features (four eyes). All patients had strongly positive Mantoux skin test results and positive chest radiograph results. The PCR results from aqueous and vitreous humor in four samples was positive for Mycobacterium tuberculosis; one had sputum positive for acid-fast bacilli, whereas two had histopathologic evidence of tuberculosis from cervical or parahilar lymph nodes. Treatment was associated with resolution of choroidal lesions and visual improvement. Final visual acuity of 20/30 or better was achieved in five eyes. CONCLUSIONS Choroidal tuberculosis may present as multifocal progressive or diffuse choroiditis resembling serpiginous choroiditis. It is important to recognize these presentations because these eyes show good response to systemic antituberculosis chemotherapy.

Acute zonal occult outer retinopathy: a long-term follow-up study

PURPOSE To report the long-term follow-up of patients with acute zonal occult outer retinopathy (AZOOR). DESIGN Observational consecutive case series. METHODS Prospective and retrospective review of medical records of patients with AZOOR. RESULTS Fifty-one patients (37 women and 14 men) with a median age of 33 years (mean, age 36 years; range, 13-63 years) were followed for a median of 96 months (mean 100 months; range, 36-420 months). At presentation, AZOOR was present in one eye of 31 patients (61%) and both eyes in 20 patients (39%). All patients presented with an acute loss of one or more zones of visual field, and 45 (88%) patients presented with photopsia. Corrected visual acuity was 20/40 or better in 68 (76%) of 90 affected eyes. Funduscopic examination was normal in 82 eyes and revealed signs of AZOOR in 8 eyes. Electroretinographic amplitudes were depressed in all affected eyes. The median delay in diagnosis of AZOOR was 17 months. During follow-up, AZOOR developed in 19 fellow eyes. At final follow-up AZOOR was present in one eye of 12 (24%) patients and both eyes of 39 (76%) patients. Sixteen patients had 23 recurrences of AZOOR. Visual field loss stabilized within 6 months in 37 patients (72%), progressed stepwise in 2 patients (4%), and partly improved in 12 patients (24%). Fourteen patients (28%) had autoimmune diseases, including Hashimotos thyroiditis in 6 patients and relapsing transverse myelopathy in 4 patients. At last follow-up all patients had residual visual field defects. Final visual acuity was 20/40 or better in 61 (68%) affected eyes. Nine patients (18%) were legally blind. The fundi of 90 affected eyes revealed no changes of AZOOR in 47 eyes (52%) and changes in the pigment epithelium and retina caused by AZOOR in 43 eyes (48%). CONCLUSIONS Visual loss in AZOOR is characterized by one or more episodes of acute dysfunction, and in some cases, death of retinal receptor cells in one or more zones of one or both eyes. Central vision is often spared, but recovery of visual field occurs infrequently. The etiology of AZOOR is unknown. Electroretinography is essential for early diagnosis. The value of treatment is uncertain.

A pooled case-control study of the apolipoprotein E (APOE) gene in age-related maculopathy

Age-related maculopathy (ARM) is a multifactorial disorder known to have a substantial genetic component. The e4 allele of the apolipoprotein E gene (APOE-4) has previously been reported to have a protective effect on ARM risk, while the APOE-2 allele may increase disease risk. This study combined four independent data sets (three US and one European) of Caucasian ARM patients and controls in order to obtain better statistical power to examine the role of APOE in ARM. APOE genotype and allele frequencies were compared for 617 ARM cases and 1260 controls, adjusting for age and sex differences between the two groups via multiple logistic regression. The protective effect of the APOE-4 allele on ARM risk was confirmed (age- and sex-adjusted odds ratio (OR) for APOE-4 carriers 0.54, 95% confidence interval (CI) 0.41–0.70, p < 0.0001). The effect of APOE-4 did not differ significantly between males and females and was observed consistently for both atrophic and neovascular ARM. Evidence for an increased risk of ARM due to the APOE-2 allele was found for men, but not for women (OR for men 1.54, 95% CI 0.97–2.45; OR for women 0.74, 95% CI 0.52–1.06, p = 0.01 for interaction of sex and APOE-2 carrier status). These data confirm that the APOE-4 allele, or an allele in linkage disequilibrium with it, reduces the risk of ARM. They also suggest that the effect of the APOE-2 allele may vary by gender, and that APOE-2 may confer an increased risk only to males.

Focal inner retinal hemorrhages in patients with drusen : An early sign of occult choroidal neovascularization and chorioretinal anastomosis

Purpose To present evidence that superficial retinal hemorrhage in the macula of patients with age-related macular degeneration (ARMD) may be an early sign of occult chorioretinal anastomosis (OCRA) and type 1 occult choroidal neovascularization (OCNV). Methods Retrospective follow-up study of 16 patients presenting with a small focal area of superficial retinal hemorrhages and drusen in the juxtafoveolar area in 24 eyes. Results OCRA and OCNV occurred in an older subset of patients with ARMD (mean age, 75 years). Of 22 eyes with the early stages of chorioretinal anastomosis (CRA), 18 had evidence of a piggyback neovascular complex, with the smaller subsensory retinal type 2 complex lying anterior to the larger subretinal pigment epithelial type 1 complex. At initial presentation, three patients had OCRA and OCNV bilaterally, and three patients had large disciform cicatricial lesions with overt CRA in the fellow eye. Nine patients had one or more laser photocoagulation treatments for early stages of CRA. Only one patient maintained visual acuity of better than 20/200 for >1 year. At the last follow-up, 24 of 26 eyes with CRA had visual acuity of 20/200 or less. Conclusion Superficial retinal hemorrhage in the paracentral area of patients with drusen is the earliest sign of OCRA and OCNV. Fluorescein angiography and indocyanine green angiography are important in detecting the dual nature of the subretinal neovascular network. Photocoagulation and photodynamic treatment is usually unsuccessful in preserving central vision.

C3 R102G polymorphism increases risk of age-related macular degeneration

Inflammation has long been suspected to play a role in the pathogenesis of age-related macular degeneration (AMD). Association of variants in the complement factor H (CFH) and complement factor B (CFB) genes has targeted the search for additional loci to the alternative complement cascade, of which C3 is a major component. Two non-synonymous coding polymorphisms within C3, R102G and L314P, have previously been strongly associated with increased risk. These variants are in strong linkage disequilibrium (LD), making the contribution of this locus to AMD even more difficult to ascertain. We sought to determine whether the C3 association resulted primarily from only one of these two variants or from a combined effect of both in 223 families and an independent dataset of 701 cases and 286 unrelated controls. The C3 polymorphisms were in strong LD (r(2) = 0.85), and both were associated in the family-based and case-control datasets (R102G genoPDT P = 0.02, case-control genotypic P = 0.004; L314P genoPDT P = 0.001, case-control genotypic P = 0.04). In conditional analyses in the case-control dataset, R102G remained associated with disease in the L314P risk allele carriers (P = 0.01), but there was no effect of L314P in the R102G risk allele carriers (P = 0.2). After adjusting for age, smoking, CFH Y402H, LOC387715 A69S, and CFB R32Q, the effect of R102G remained strong [P = 0.015, odds ratio = 1.55, 95% confidence interval 1.09 to 2.21, adjusted PAR(population attributable risk) = 0.17]. Therefore, while the strong LD between R102G and L314P makes it difficult to disentangle their individual effects on disease risk, the R102G polymorphism acting alone provides the best model for disease in our data.

Mitochondrial DNA polymorphism A4917G is independently associated with age-related macular degeneration.

The objective of this study was to determine if MTND2*LHON4917G (4917G), a specific non-synonymous polymorphism in the mitochondrial genome previously associated with neurodegenerative phenotypes, is associated with increased risk for age-related macular degeneration (AMD). A preliminary study of 393 individuals (293 cases and 100 controls) ascertained at Vanderbilt revealed an increased occurrence of 4917G in cases compared to controls (15.4% vs.9.0%, p = 0.11). Since there was a significant age difference between cases and controls in this initial analysis, we extended the study by selecting Caucasian pairs matched at the exact age at examination. From the 1547 individuals in the Vanderbilt/Duke AMD population association study (including 157 in the preliminary study), we were able to match 560 (280 cases and 280 unaffected) on exact age at examination. This study population was genotyped for 4917G plus specific AMD-associated nuclear genome polymorphisms in CFH, LOC387715 and ApoE. Following adjustment for the listed nuclear genome polymorphisms, 4917G independently predicts the presence of AMD (OR = 2.16, 95%CI 1.20–3.91, p = 0.01). In conclusion, a specific mitochondrial polymorphism previously implicated in other neurodegenerative phenotypes (4917G) appears to convey risk for AMD independent of recently discovered nuclear DNA polymorphisms.

Ordered subset linkage analysis supports a susceptibility locus for age-related macular degeneration on chromosome 16p12

BackgroundAge-related macular degeneration (AMD) is a complex disorder that is responsible for the majority of central vision loss in older adults living in developed countries. Phenotypic and genetic heterogeneity complicate the analysis of genome-wide scans for AMD susceptibility loci. The ordered subset analysis (OSA) method is an approach for reducing heterogeneity, increasing statistical power for detecting linkage, and helping to define the most informative data set for follow-up analysis. OSA assesses the linkage evidence in subsets of potentially more homogeneous families by rank-ordering family-specific lod scores with respect to trait-associated covariates or phenotypic features. Here, we present results of incorporating five continuous covariates into our genome-wide linkage analysis of 389 microsatellite markers in 62 multiplex families: Body mass index (BMI), systolic (SBP) and diastolic (DBP) blood pressure, intraocular pressure (IOP), and pack-years of cigarette smoking. Chromosome-wide significance of increases in nonparametric multipoint lod scores in covariate-defined subsets relative to the overall sample was assessed by permutation.ResultsUsing a correction for testing multiple covariates, statistically significant lod score increases were observed for two chromosomal regions: 14q13 with a lod score of 3.2 in 28 families with average IOP ≤ 15.5 (p = 0.002), and 6q14 with a lod score of 1.6 in eight families with average BMI ≥ 30.1 (p = 0.0004). On chromosome 16p12, nominally significant lod score increases (p ≤ 0.05), up to a lod score of 2.9 in 32 families, were observed with several covariate orderings. While less significant, this was the only region where linkage evidence was associated with multiple clinically meaningful covariates and the only nominally significant finding when analysis was restricted to advanced forms of AMD. Families with linkage to 16p12 had higher averages of SBP, IOP and BMI and were primarily affected with neovascular AMD. For all three regions, linkage signals at or very near the peak marker have previously been reported.ConclusionOur results suggest that a susceptibility gene on chromosome 16p12 may predispose to AMD, particularly to the neovascular form, and that further research into the previously suggested association of neovascular AMD and systemic hypertension is warranted.