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A.G. Junemann, U. Reulbach, S. Bleich, C.Y. Mardin, J.B. Jonas, F.E. Kruse, J. Kornhuber; Genetic Association of Apolipoprotein E With Optic Disc Size . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2491.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Apolipoprotein E (ApoE) is involved in repair, growth, and maintenance of myelin and neuronal membranes during development or after injury. Recently it has been shown that ApoE plays a role in optic nerve morphogenesis. This study was undertaken to investigate whether ApoE isoforms (ε2, ε3, ε4) are associated with optic disc size. Methods: 96 patients with primary open–angle glaucoma, 54 patients with ocular hypertension, and 32 controls were included. All individuals were unrelated Caucasians and had open anterior chamber angles, clear optic media, and a visual acuity of 20/25 or better. Exclusion criteria were all eye diseases other than glaucoma, diabetes mellitus, and myopic refractive error exceeding –8 diopters. Planimetry of the optic disc was performed using 15° color stereo optic disc photographs. For APOE genotyping, genomic DNA was extracted from anticoagulated blood after isolation of peripheral lymphocytes following the salting out–method. As allele ε3 is considered to be the ancestral allele, and ε2 and ε4 are considered as variants on the basis of single point mutations, the ε3ε3 genotype was used as reference. As the frequency of the genotypes ε2ε2, ε2ε4, ε4ε4 was less or equal than 7, these genotypes were excluded from the analysis. Results: The size of the optic disc differed significantly between subjects with ε3ε2, ε3ε3, and ε4ε3 allele (Kruskal–Wallis–test, Chi–Square: 6.95, p =0.031; 2.39 (SD 0.56) vs. 2.77 (SD 0.69) vs. 2.78 (SD 0.88) mm2). Regarding the differences between the possible pairs (ε3ε2,ε3ε3; ε3ε2,ε4ε3; ε3ε3,ε4ε3), only subjects with ε3ε2 allele had a significant smaller size of the optic disc than subjects with the reference genotype ε3ε3 (Mann–Whitney U, Z=–2.74, p=0.018, Bonferroni corrected for multiple testing). Conclusions: The data from this study indicate that apolipoprotein E gene alleles are associated with optic disc size. Small optic disc size is associated with ApoE ε2 allele carrier, large optic disc size with ApoE ε4 allele carrier. Further studies are necessary to elucidate the interrelationship between optic disc size, apolipoprotein E and risk for glaucoma.
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