\set{final} \def\Author{Vickers} \def\author{vickers} \def\vol{8} \def\year{2002} \def\anum{46} \def\pages{389-393} \def\txt_title{The apolipoprotein [epsilon]4 gene is associated with elevated risk of normal tension glaucoma} \def\txt_authors{James C. Vickers, Jamie E. Craig, Jim Stankovich, Graeme H. McCormack, Adrian K. West, Joanne L. Dickinson, Paul J. McCartney, Michael A. Coote, Danielle L. Healey, David A. Mackey} \def\rcvd{22 May 2002} \def\accept{11 October 2002} \def\publ{14 October 2002} \def\pdfsize{} \def\PMID{} \include{mvstyle.hsm} \| External links \| Internal defs \def\Muller{M\uuml ller} \article{ \title{The apolipoprotein \epsilon 4 gene is associated with elevated risk of normal tension glaucoma} \authors{\mailto{James.Vickers@utas.edu.au}{James C. Vickers},\sup{1} \mailto{Jamie.Craig@fmc.sa.gov.au}{Jamie E. Craig},\sup{2} \mailto{jim.stankovich@utas.edu.au}{Jim Stankovich},\sup{3} \mailto{g.h.mccormack@utas.edu.au}{Graeme H. McCormack},\sup{1} \mailto{awest@utas.edu.au}{Adrian K. West},\sup{1} Joanne L. Dickinson,\sup{3} Paul J. McCartney,\sup{1} Michael A. Coote,\sup{4} Danielle L. Healey,\sup{4} David A. Mackey\sup{4}} \institutions{\sup{1}School of Medicine, University of Tasmania, Hobart, Tasmania, Australia; \sup{2}Department of Ophthalmology, Flinders Medical Centre, South Australia, Australia; \sup{3}Menzies Research Institute, Hobart, Tasmania, Australia; \sup{4}Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Australia} \correspondence{James Vickers, Associate Professor, School of Medicine, University of Tasmania, GPO Box 252-29, Hobart, Tasmania 7001, Australia; Phone: 61-3-62264827; FAX: 61-3-62264833; email: James.Vickers@utas.edu.au} \abstract \abs_purpose{Inheritance of a particular apolipoprotein E gene polymorphism, the \epsilon 4 allele, has been associated with elevated risk for Alzheimer's disease and a poor outcome following head injury. The neuronal injury associated with Alzheimer's disease and brain injury may have a number of similarities with the nerve cell changes associated with glaucoma. Thus, we have investigated the association of inheritance of apolipoprotein E allelic isoforms (\epsilon 2, \epsilon 3, and \epsilon 4) with relative risk for different forms of glaucoma.} \abs_methods{Apolipoprotein E genotype was examined in a Tasmanian population sample comprised of glaucoma sufferers with elevated or normal intraocular pressure and compared to a control sample of elderly Tasmanians without glaucoma.} \abs_results{Approximately twice as many normal tension (38.0%) and high tension (34.2%) glaucoma cases possessed an \epsilon 4 allele compared to control cases (18.9%). The odds of \epsilon 4 carriers having normal tension glaucoma were significantly greater than for \epsilon 3 homozygotes (odds ratio 2.45, 95% confidence interval \{1.02-5.91\}) even after adjusting for age and gender (odd ratio 2.87 \{1.02-8.05\}). The increased odds of high tension glaucoma among \epsilon 4 allele carriers were not significant (adjusted odds ratio 1.53 \{0.64-3.68\}).} \abs_conclusions{The data indicate that, in the Tasmanian population, inheritance of the \epsilon 4 allele is associated with elevated risk for glaucomatous changes that are not related to increased intraocular pressure.} \introduction \p{The apolipoprotein E protein has a number of lipid transport related roles in various tissues. The gene encoding apolipoprotein E on chromosome 19q13.2 has three polymorphic variants in humans designated as \epsilon 2, \epsilon 3, and \epsilon 4. Inheritance of \epsilon 4 and \epsilon 2 alleles has been associated with higher and lower risk, respectively, of Alzheimer's disease [1,2], although this may not be the case for all ethnic populations [3,4]. The precise involvement of apolipoprotein E in Alzheimer's disease pathology has not been settled [5]. For example, there is evidence that the apolipoprotein E protein may act to promote the development of \beta-amyloid deposits [6-9]. Alternatively, apolipoprotein E may have a more generalized role in neural repair cellular pathways, particularly with respect to the mobilization of cholesterol and other lipids following neuronal damage [10]. In this respect, possession of \epsilon 4 alleles has been associated with a poor outcome following various forms of traumatic head injury [11-13] as well as more severe disease progression in multiple sclerosis [14,15] and reduced survival time in amyotrophic lateral sclerosis [16].} \p{We have presented evidence that the neuronal pathology of Alzheimer's disease may be attributed to an aberrant regenerative response of nerve cells triggered by the gradual compression and physical damage to axons within \beta-amyloid plaques that form in the brain [5]. Thus, the apolipoprotein E genotype may affect the response of neurons to injury by plaque formation [5]. Similarly, the selective injury to retinal ganglion cells observed in glaucoma may be caused by axonal injury, perhaps by compression and restriction of normal axoplasmic flow, at the level of the lamina cribrosa [17,18]. For the majority of glaucoma cases, prolonged increased intraocular pressure may exert physical force on the structural framework of the lamina cribrosa leading to axonal injury. However, there are also a significant proportion of cases designated normal tension glaucoma (NTG) in which a glaucoma-like pattern of degeneration is present in the absence of elevated intraocular pressure. The underlying cause of retinal neuron degeneration in NTG has yet to be determined. A further point of similarity between Alzheimer's disease and glaucoma is reflected in the pattern of cell vulnerability. In the neocortex, it is the subgroup of cortical nerve cells containing the neurofilament triplet proteins that are susceptible to neurofibrillary tangle formation [5] and it is the subgroup of retinal ganglion cells selectively containing these proteins that are highly susceptible to degeneration in glaucoma [19].} \p{Given the potential similarities between the cellular events leading to degeneration in both Alzheimer's disease and glaucoma, we proposed that the apolipoprotein E isoforms are a pliable candidate for glaucoma susceptibility With respect to eye diseases, there has been a reported negative association of risk for age related macular degeneration with inheritance of the \epsilon 4 allele [20]. We therefore sought to investigate whether the apolipoprotein E genotype is associated with either NTG or high tension glaucoma (HTG) in the Tasmanian population.} \methods \subsection{Case selection} \p{The Glaucoma Inheritance Study in Tasmania (GIST) project is a large study based in Tasmania and other states in Australia [21]. The primary aim has been to recruit all cases of glaucoma in the Tasmanian population, with a particular emphasis on identifying pedigrees with inherited forms of primary open angle glaucoma (POAG). All subjects recruited for the GIST project have undergone systematic examination of optic disc, visual field and intraocular pressure (IOP) [22,23]. The cases used in this investigation were unrelated to each other and were derived exclusively from the Tasmanian population. A series of elderly population controls were also screened for the presence of glaucoma, and those without glaucoma were subsequently utilized as control subjects (n=51). The mean age of these control subjects was 83.2 (\pom 7.0, standard deviation) and that of the NTG (n=70) and HTG (n=72) cases was 73.0 (\pom 10.3) and 75.6 (\pom 9.1), respectively. Written informed consent was obtained from patients involved in the GIST (as well as control subjects), and the study was approved by the ethics committees of the Royal Victorian Eye and Ear Hospital (Melbourne), the University of Tasmania (Hobart) and the Royal Hobart Hospital (Hobart). All procedures were conducted in accordance with the declaration of Helsinki and subsequent revisions.} \p{Subjects utilized were classified as normal (normal disc with full Humphrey visual field [Humphrey Instruments, San Leandro, CA], IOP less than 22 mm Hg), high tension glaucoma (HTG), or POAG (glaucomatous disc and/or field defect, IOP greater than 21 mm Hg) and normal tension glaucoma (NTG; glaucomatous disc and/or glaucomatous field defect in patients with no documented IOP greater than 21 mm Hg). Gonioscopy was utilized to confirm that all cases had open angles.} \subsection{Genomic DNA isolation and genotyping} \p{Genomic DNA was extracted from blood samples and apolipoprotein E genotyping conducted using protocols provided by QIAGEN Corp. (Bothell, WA). Briefly, 10 ml of blood was pelleted and the red/white nuclei were disrupted by shaking in the presence of 0.32 M sucrose, 10 mM Tris-HCl (pH 7.5), 5 mM MgCl\sub{2} and 1% Triton-X-100. The subsequent pellet was then digested with 1.3 mg Proteinase K in 1.15% SDS, 10 mM Tris-HCl (pH 7.5), 400 mM NaCl and 2 mM EDTA (pH 8.0) for 16 h at 50 \deg C. Saturated NaCl (6 M) was added to the digest. Protein and salts were precipitated with shaking and centrifugation, and the DNA containing supernatant was then ethanol precipitated. Genomic DNA was spooled out and washed in 70% ethanol after which the ethanol was evaporated. The DNA pellet was then re-suspended in 10 mM Tris-HCl, 1 mM Na\sub{2}EDTA pH 8.0. Genomic DNA was PCR amplified in the presence of 200 \mu M each dNTP, 1X Q-Solution (QIAGEN), 1X QIAGEN\reg\ PCR Buffer, 1.5 U QIAGEN Taq DNA polymerase and 0.25 \mu M of each primer. The two primers used were: E2mut (5'ACT GAC CCC GGT GGC GGA GGA GAC GCG \color{\red}{T}GC) upstream primer and E3 (5' TGT TCC ACC AGG GGC CCC AGG CGC TCG CGG) downstream primer. The upstream primer differs from the genomic sequence at the red position to create an additional \i{Afl} 111 recognition site in the PCR product. Reactions were treated to incubation at 94 \deg C for 3 min followed by 40 cycles of: 94 \deg C, 10 s; 65 \deg C, 30 s; 72 \deg C, 30 s. A final incubation at 72 \deg C for 7 min was carried out. The PCR product was then digested in two separate reactions at 37 \deg C for 48 h. One reaction used 10 \mu l PCR product, 2.5 units \i{Afl}111 (NEB), 25 \mu g BSA, 100 mM NaCl, 50 mM Tris-HCl, 10 mM MgCl\sub{2}, 1 mM DTT pH 7.9 (NEB buffer 3). The other reaction used 10 \mu l PCR product, 1.5 units Hae11 (NEB), 25 \mu g BSA, 50 mM potassium acetate, 20 mM Tris acetate, 10 mM magnesium acetate, 1 mM DTT pH 7.9 (NEB buffer 4). Electrophoresis of both digests was carried out on a 4% agarose in 1X TAE gel. The gel was then stained with SYBR Gold and imaged with a digital camera. Apolipoprotein E alleles were identified by a unique pattern of digested fragments as provided by QIAGEN Corp.} \p{Fisher's exact test [24] was used to determine the significances of differences in allele and genotype frequencies among the groups. Logistic regression was used to estimate the odds of glaucoma in \epsilon 4 and \epsilon 2 allele carriers compared to \epsilon 3/\epsilon 3 homozygotes. Both unadjusted and adjusted (for sex and age) odds ratios were estimated.} \results \p{Frequencies of apolipoprotein E genotypes and alleles in controls, NTG cases and HTG cases are presented in \tabref{1}. \tabref{1} shows that the \epsilon 4 allele was more common in NTG cases and HTG cases than controls. Overall, approximately twice as many NTG (38.0%) and HTG (34.2%) cases possessed at least one apolipoprotein \epsilon 4 allele in comparison to the control group (18.9%). In particular, the relative proportion of the \epsilon 3/\epsilon 4 genotype was higher in both the NTG and HTG groups relative to controls (p=0.026 and p=0.027, respectively; Fisher's exact test for a difference of proportions). In addition, there were fewer individuals with the \epsilon 2/\epsilon 3 genotype in both the NTG and HTG groups, but this reached significance only for the HTG group (p=0.027). The only significant difference in allele frequencies was the lower frequency of the \epsilon 2 allele in HTG cases (4.9%) relative to the control group (14.7%, p=0.011).} \p{\tabref{2} shows odds ratios for the presence of NTG and HTG in \epsilon 4 carriers and \epsilon 2 carriers compared to the reference group of \epsilon 3/\epsilon 3 homozygotes. Unadjusted for age and sex, presence of an \epsilon 4 allele was associated with a significant increase in the odds of NTG (p=0.045). This odds ratio increased marginally after adjustment for age and sex, with a corresponding p value of 0.046. There was also an increase in the odds of HTG amongst \epsilon 4 carriers but it was not significant (p=0.26). The observed protective effect of the \epsilon 2 allele for HTG was not significant after adjustment (p=0.30).} \discussion \p{The analysis of apolipoprotein E genotypes in this Tasmanian population sample indicates that inheritance of the \epsilon 4 allele may represent a risk factor for glaucoma, particularly for cases associated with normal intraocular pressures. Thus, in addition to gene mutations linked with familial forms of glaucoma (e.g., myocilin [25], optineurin [26]), there are likely to be specific gene polymorphisms that increase or decrease risk for heritable and sporadic forms of the disease (e.g., apolipoprotein E and OPA1 [27]).} \p{It is important to note that the frequencies of the three apolipoprotein E alleles in the Tasmanian control population differ significantly from those reported in a large sample of Australian subjects aged over 70 drawn from the electoral roll in Canberra and Queanbeyan [28]. In this sample of 1276 alleles [28], the frequencies of the \epsilon 2, \epsilon 3, and \epsilon 4 alleles were 6.4%, 80.8%, and 12.9% respectively (p=0.02 for overall difference in frequencies compared to the Tasmanian controls). This suggests that the population distribution of apolipoprotein E alleles in Tasmania differs from the distributions in other Australian states. Tasmania is an island with a relatively stable and homogenous population. Compared to the mainland states of Australia, levels of immigration have been low subsequent to the initial colonization by Europeans in the early 1800s.} \p{However, as the \epsilon 4 allele has similar frequencies in the large cohort (12.9%) and the Tasmanian control population (11.8%), estimates of the increased odds ratios for NTG and HTG among \epsilon 4 carrier did not change greatly when we conducted a further analysis using the larger Canberra cohort [28] as the control population. For example, the odds of NTG among \epsilon 4 carriers are still significantly higher than among \epsilon 3 homozygotes (2.20, 95% confidence interval \{1.28-3.79\}) and this result changes little if NTG cases younger than 70 are excluded to match the age restrictions of the Canberra cohort (2.31, \{1.12-4.45\}).} \p{This finding is also interesting with respect to the reported linkage of the \epsilon 4 allele with lower risk for age related macular degeneration [20,29]. However, it has recently been suggested that this effect may be relatively modest and largely restricted to familial forms of this condition where the affected individual is of a younger age [30]. Apolipoprotein E immunoreactivity has been localized to basal laminar deposits and soft drusen in age related macular degeneration [20]. Apolipoprotein E has also been localized to the \Muller\ cells (specialized retinal glia) [20,31] and this protein may be increased in \Muller\ cells in glaucomatous eyes [32], indicating that this glial cell may have a role in the retinal response to glaucomatous injury.} \p{Inheritance of the \epsilon 4 allele has also been associated with elevated risk to Alzheimer's disease. In this regard, it is interesting that visual deficits have been reported in Alzheimer's disease cases. However, there are conflicting reports as to whether visual field loss observed in a relatively high proportion of Alzheimer's disease cases is associated with retinal or central damage [33-38]. It has recently been noted that both Alzheimer's disease and Parkinson's disease cases have increased glaucomatous retinal changes [39]. In the light of the current findings, there may be similar cellular processes involving apolipoprotein E related to neuronal damage that are relatively deficient in \epsilon 4 allele carriers. It has been argued that both Alzheimer's disease and glaucoma are ultimately axon damaging conditions and it is how nerve cells respond to this injury that leads to overall neuronal degeneration and the clinical picture of progressive loss of function [19]. \Muller\ cells that express particular apolipoprotein E isoforms may thus have an important role in regulating the response of retinal ganglion cells to injury. However, it can not be ruled out that apolipoprotein may be acting centrally to promote \beta-amyloid fibril formation in structures such as the lateral geniculate nucleus [40] and that these plaques are causing damage to retinal axons and visual pathways. In this regard, it would be intriguing to determine whether NTG cases may have a higher incidence of Alzheimer-type dementia.} \p{Inheritance of the \epsilon 4 allele appears to be associated with elevated risk of glaucoma, particularly NTG, in our well characterized Tasmanian glaucoma population. However, it will be important to replicate these results in populations from other geographical locations. In addition to identified genes with an autosomal dominant pattern of inheritance (myocilin, optineurin) there may be many gene variations that elevate or decrease risk for the retinal degeneration characteristic of glaucoma (OPA1, apolipoprotein E). The significance of inheritance of these apolipoprotein E allelic isoforms has yet to be established, as is the case for the potential role of this protein in many other neurodegenerative conditions, but it may be linked with associated hypertension, formation of central \beta-amyloid deposits or a more general role in the regulation of lipids following axonal injury. However, the current data points to a potential in overlap between the degenerative pathways underlying glaucoma, particularly NTG, and Alzheimer-type dementia and brain injury.} \acknowledgements \p{Funded by the National Health and Medical Research Council, Clifford Craig Medical Research Trust, Ophthalmic Research Institute of Australia and Glaucoma Research Foundation. We would like to thank Marian Quilty and Jyoti Chuckowree for reading the manuscript.} \references \p{1. Corder EH, Saunders AM, Strittmatter WJ, Schmechel DE, Gaskell PC, Small GW, Roses AD, Haines JL, Pericak-Vance MA. Gene dose of apolipoprotein E type 4 allele and the risk of Alzheimer's disease in late onset families. Science 1993; 261:921-3. \pubmed{8346443}} \p{2. Chartier-Harlin MC, Parfitt M, Legrain S, Perez-Tur J, Brousseau T, Evans A, Berr C, Vidal O, Roques P, Gourlet V, Frouchart JC, Delacourte A, Rossor M, Amouyel P. Apolipoprotein E, epsilon 4 allele as a major risk factor for sporadic early and late-onset forms of Alzheimer's disease: analysis of the 19q13.2 chromosomal region. Hum Mol Genet 1994; 3:569-74. \pubmed{8069300}} \p{3. Osuntokun BO, Sahota A, Ogunniyi AO, Gureje O, Baiyewu O, Adeyinka A, Oluwole SO, Komolafe O, Hall KS, Unverzagt FW, Hui SL, Yang M, Hendrie HC. Lack of an association between apolipoprotein E epsilon 4 and Alzheimer's disease in elderly Nigerians. Ann Neurol 1995; 38:463-5. \pubmed{7668835}} \p{4. Tang MX, Stern Y, Marder K, Bell K, Gurland B, Lantigua R, Andrews H, Feng L, Tycko B, Mayeux R. The APOE-epsilon4 allele and the risk of Alzheimer disease among African Americans, whites, and Hispanics. JAMA 1998; 279:751-5. \pubmed{9508150}} \p{5. Vickers JC, Dickson TC, Adlard PA, Saunders HL, King CE, McCormack G. The cause of neuronal degeneration in Alzheimer's disease. Prog Neurobiol 2000; 60:139-65. \pubmed{10639052}} \p{6. Wisniewski T, Frangione B. Apolipoprotein E: a pathological chaperone protein in patients with cerebral and systemic amyloid. Neurosci Lett 1992; 135:235-8. \pubmed{1625800}} \p{7. Rebeck GW, Reiter JS, Strickland DK, Hyman BT. Apolipoprotein E in sporadic Alzheimer's disease: allelic variation and receptor interactions. Neuron 1993; 11:575-80. \pubmed{8398148}} \p{8. Schmechel DE, Saunders AM, Strittmatter WJ, Crain BJ, Hulette CM, Joo SH, Pericak-Vance MA, Goldgaber D, Roses AD. Increased amyloid beta-peptide deposition in cerebral cortex as a consequence of apolipoprotein E genotype in late-onset Alzheimer disease. Proc Natl Acad Sci U S A 1993; 90:9649-53. \pubmed{8415756}} \p{9. Ma J, Yee A, Brewer HB Jr, Das S, Potter H. Amyloid-associated proteins alpha 1-antichymotrypsin and apolipoprotein E promote assembly of Alzheimer beta-protein into filaments. Nature 1994; 372:92-4. \pubmed{7969426}} \p{10. Poirier J. Apolipoprotein E in animal models of CNS injury and in Alzheimer's disease. Trends Neurosci 1994; 17:525-30. \pubmed{7532337}} \p{11. Teasdale GM, Nicoll JA, Murray G, Fiddes M. Association of apolipoprotein E polymorphism with outcome after head injury. Lancet 1997; 350:1069-71. \pubmed{10213549}} \p{12. Jordan BD, Relkin NR, Ravdin LD, Jacobs AR, Bennett A, Gandy S. Apolipoprotein E epsilon4 associated with chronic traumatic brain injury in boxing. JAMA 1997; 278:136-40. \pubmed{9214529}} \p{13. Friedman G, Froom P, Sazabon L, Grinblatt I, Shochina M, Tsenter J, Babaey S, Yehuda B, Groswasser Z. Apolipoprotein E-epsilon4 genotype predicts a poor outcome in survivors of traumatic brain injury. Neurology 1999; 52:244-8. \pubmed{9932938}} \p{14. Chapman J, Sylantiev C, Nisipeanu P, Korczyn AD. Preliminary observations on APOE epsilon4 allele and progression of disability in multiple sclerosis. Arch Neurol 1999; 56:1484-7. \pubmed{10593303}} \p{15. Evangelou N, Jackson M, Beeson D, Palace J. Association of the APOE epsilon4 allele with disease activity in multiple sclerosis. J Neurol Neurosurg Psychiatry 1999; 67:203-5. \pubmed{10406990}} \p{16. Drory VE, Birnbaum M, Korczyn AD, Chapman J. Association of APOE epsilon4 allele with survival in amyotrophic lateral sclerosis. J Neurol Sci 2001; 190:17-20. \pubmed{11574101}} \p{17. Quigley HA. Ganglion cell death in glaucoma: pathology recapitulates ontogeny. Aust N Z J Ophthalmol 1995; 23:85-91. \pubmed{7546696}} \p{18. Vickers JC. The cellular mechanism underlying neuronal degeneration in glaucoma: parallels with Alzheimer's disease. Aust N Z J Ophthalmol 1997; 25:105-9. \pubmed{9267595}} \p{19. Vickers JC, Schumer RA, Podos SM, Wang RF, Riederer BM, Morrison JH. Differential vulnerability of neurochemically identified subpopulations of retinal neurons in a monkey model of glaucoma. Brain Res 1995; 680:23-35. \pubmed{7663981}} \p{20. Klaver CC, Kliffen M, van Duijn CM, Hofman A, Cruts M, Grobbee DE, van Broeckhoven C, de Jong PT. Genetic association of apolipoprotein E with age-related macular degeneration. Am J Hum Genet 1998; 63:200-6. \pubmed{9634502}} \p{21. Sack J, Healey DL, de Graaf AP, Wilkinson RM, Wilkinson CH, Barbour JM, Coote MA, McCartney PJ, Rait JL, Cooper RL, Ring MA, Mackey DA. The problem of overlapping glaucoma families in the Glaucoma Inheritance Study in Tasmania (GIST). Ophthalmic Genet 1996; 17:209-14. \pubmed{9010872}} \p{22. McNaught AI, Allen JG, Healey DL, McCartney PJ, Coote MA, Wong TL, Craig JE, Green CM, Rait JL, Mackey DA. Accuracy and implications of a reported family history of glaucoma: experience from the Glaucoma Inheritance Study in Tasmania. Arch Ophthalmol 2000; 118:900-4. \pubmed{10900101}} \p{23. Craig JE, Baird PN, Healey DL, McNaught AI, McCartney PJ, Rait JL, Dickinson JL, Roe L, Fingert JH, Stone EM, Mackey DA. Evidence for genetic heterogeneity within eight glaucoma families, with the GLC1A Gln368STOP mutation being an important phenotypic modifier. Ophthalmology 2001; 108:1607-20. \pubmed{11535458}} \p{24. Agresti A. Categorical data analysis. New York: Wiley; 1990.} \p{25. Stone EM, Fingert JH, Alward WL, Nguyen TD, Polansky JR, Sunden SL, Nishimura D, Clark AF, Nystuen A, Nichols BE, Mackey DA, Ritch R, Kalenak JW, Craven ER, Sheffield VC. Identification of a gene that causes primary open angle glaucoma. Science 1997; 275:668-70. \pubmed{9005853}} \p{26. Rezaie T, Child A, Hitchings R, Brice G, Miller L, Coca-Prados M, Heon E, Krupin T, Ritch R, Kreutzer D, Crick RP, Sarfarazi M. Adult-onset primary open-angle glaucoma caused by mutations in optineurin. Science 2002; 295:1077-9. \pubmed{11834836}} \p{27. Aung T, Ocaka L, Ebenezer ND, Morris AG, Krawczak M, Thiselton DL, Alexander C, Votruba M, Brice G, Child AH, Francis PJ, Hitchings RA, Lehmann OJ, Bhattacharya SS. A major marker for normal tension glaucoma: association with polymorphisms in the OPA1 gene. Hum Genet 2002; 110:52-6. \pubmed{11810296}} \p{28. Henderson AS, Easteal S, Jorm AF, Mackinnon AJ, Korten AE, Christensen H, Croft L, Jacomb PA. Apolipoprotein E allele epsilon 4, dementia, and cognitive decline in a population sample. Lancet 1995; 346:1387-90. \pubmed{7475820}} \p{29. Souied EH, Benlian P, Amouyel P, Feingold J, Lagarde JP, Munnich A, Kaplan J, Coscas G, Soubrane G. The epsilon4 allele of the apolipoprotein E gene as a potential protective factor for exudative age-related macular degeneration. Am J Ophthalmol 1998; 125:353-9. \pubmed{9512153}} \p{30. Schmidt S, Saunders AM, De La Paz MA, Postel EA, Heinis RM, Agarwal A, Scott WK, Gilbert JR, McDowell JG, Bazyk A, Gass JD, Haines JL, Pericak-Vance MA. Association of the apolipoprotein E gene with age-related macular degeneration: possible effect modification by family history, age, and gender. Mol Vis 2000; 6:287-93 \mvref{6}{37}. \pubmed{11141572}} \p{31. Amaratunga A, Abraham CR, Edwards RB, Sandell JH, Schreiber BM, Fine RE. Apolipoprotein E is synthesized in the retina by Muller glial cells, secreted into the vitreous, and rapidly transported into the optic nerve by retinal ganglion cells. J Biol Chem 1996; 271:5628-32. \pubmed{8621425}} \p{32. Kuhrt H, Hartig W, Grimm D, Faude F, Kasper M, Reichenbach A. Changes in CD44 and ApoE immunoreactivities due to retinal pathology of man and rat. J Hirnforsch 1997; 38:223-9. \pubmed{9176734}} \p{33. Hinton DR, Sadun AA, Blanks JC, Miller CA. Optic-nerve degeneration in Alzheimer's disease. N Engl J Med 1986; 315:485-7. \pubmed{3736630}} \p{34. Trick GL, Barris MC, Bickler-Bluth M. Abnormal pattern electroretinograms in patients with senile dementia of the Alzheimer type. Ann Neurol 1989; 26:226-31. \pubmed{2774510}} \p{35. Sadun AA, Bassi CJ. Optic nerve damage in Alzheimer's disease. Ophthalmology 1990; 97:9-17. \pubmed{2314849}} \p{36. Tsai CS, Ritch R, Schwartz B, Lee SS, Miller NR, Chi T, Hsieh FY. Optic nerve head and nerve fiber layer in Alzheimer's disease. Arch Ophthalmol 1991; 109:199-204. \pubmed{1993028}} \p{37. Curcio CA, Drucker DN. Retinal ganglion cells in Alzheimer's disease and aging. Ann Neurol 1993; 33:248-57. \pubmed{8498808}} \p{38. Davies DC, McCoubrie P, McDonald B, Jobst KA. Myelinated axon number in the optic nerve is unaffected by Alzheimer's disease. Br J Ophthalmol 1995; 79:596-600. \pubmed{7542917}} \p{39. Bayer AU, Keller ON, Ferrari F, Maag KP. Association of glaucoma with neurodegenerative diseases with apoptotic cell death: Alzheimer's disease and Parkinson's disease. Am J Ophthalmol 2002; 133:135-7. \pubmed{11755850}} \p{40. Leuba G, Saini K. Pathology of subcortical visual centres in relation to cortical degeneration in Alzheimer's disease. Neuropathol Appl Neurobiol 1995; 21:410-22. \pubmed{8632836}} \endreferences } \begintables \tabfile{1}{ \tabtitle{1}{Apolipoprotein E genotype and allelic frequencies} \p{Distribution of genotypes and allelic frequencies in normal tension glaucoma, high tension glaucoma, and cases lacking glaucoma (controls). For each row of the table, differences in proportions between cases and controls were assessed using Fisher's exact test. Asterisks ("*") indicate significant differences (\alpha=0.05 for each test).} \box{\pre{ Control Normal tension High tension Genotype (n=51) glaucoma (n=70) glaucoma (n=72) --------- ---------- --------------- --------------- \epsilon 2/\epsilon 2 2 (3.9%) 5 (7.1%) 1 (1.4%) \epsilon 2/\epsilon 3 9 (17.7%) 5 (7.1%) 3 (4.7%)* \epsilon 3/\epsilon 3 30 (58.8%) 33 (47.1%) 45 (62.5%) \epsilon 3/\epsilon 4 6 (11.8%) 21 (30.0%)* 21 (29.2%)* \epsilon 2/\epsilon 4 2 (3.9%) 5 (7.1%) 2 (2.8%) \epsilon 4/\epsilon 4 2 (3.9%) 1 (1.4%) 0 (0.0%) Allele Control Normal tension High tension frequency (n=51) glaucoma (n=70) glaucoma (n=72) --------- ---------- --------------- --------------- \epsilon 2 15 (14.7%) 20 (14.3%) 7 (4.9%)* \epsilon 3 75 (73.5%) 92 (65.7%) 114 (79.2%) \epsilon 4 12 (11.8%) 28 (20.0%) 23 (16.0%) }} } \tabfile{2}{ \tabtitle{2}{Odds ratios by genotype} \p{Table of odds ratios (crude, adjusted for age and sex) for normal (NTG) and high (HTG) tension glaucoma, for \epsilon 2 carriers and \epsilon 4 carriers relative to \epsilon 3/\epsilon 3 homozygotes. Grouped genotypes contain at least one of the \epsilon 2 or \epsilon 4 alleles, respectively (i.e., \epsilon 2/\epsilon 4 cases are included in both) with the \epsilon 3/\epsilon 3 group serving as a reference.} \box{\pre{ Normal tension glaucoma (n=70) High tension glaucoma (n=72) ---------------------------------------- ---------------------------------------- Odds ratio \{95% CI\} Odds ratio \{95% CI\} Control ----------------------------------- ----------------------------------- Genotype (n=51) n Crude Adjusted n Crude Adjusted -------- ------- -- ---------------- ---------------- -- ---------------- ---------------- \epsilon 3/\epsilon 3 30 33 45 \epsilon 2/- 13 15 1.05 \{0.43-2.56\} 2.01 \{0.69-5.81\} 6 0.31 \{0.11-0.90\} 0.53 \{0.16-1.78\} \epsilon 4/- 10 27 2.45 \{1.02-5.91\} 2.87 \{1.02-8.05\} 23 1.53 \{0.64-3.68\} 1.74 \{0.67-4.55\} }} }