NEIGHBOR-Methylation in POAG

This is a case-control study of Primary Open Angle Glaucoma (POAG). POAG is a progressive optic neuropathy that eventually leads to blindness. More than 30 million people worldwide have Primary Open Angle Glaucoma (POAG), of which greater than 3 million are blind. Gene expression changes in the retina have been observed for POAG. Several recent studies, including the NEIGHBOR consortium (NEI Glaucoma Human genetic collaboration) have used GWAS to identify correlative regions of the genome. Despite this, the genetic basis of Glaucoma is not well understood. Epigenetic variation may account for low heritability and environmental effects on human disease. Despite the significant advances being made in understanding the role of epigenetics in gene regulation in other fields, little is known about the relationship between DNA methylation patterns, retinal gene expression, and retinal disease. The goal of this study is to identify differentially methylated regions in the peripheral blood of patients with POAG. The case identification is as per the NEIGHBOR description: Cases and controls were recruited from ophthalmology clinics and were examined by ophthalmologists. For cases the clinical exam included intraocular pressure measurements, optic nerve assessment and visual field evaluation. Controls had no family history of glaucoma, normal intraocular pressure and normal optic nerves. POAG and control samples come from two sources: Duke University and Massachusetts Eye and Ear Infirmary (MEEI). These samples were collected and genotyped as part of the NEIGHBOR study. From the 219 POAG cases contributed to NEIGHBOR by Duke, 75 samples were selected for exome sequencing by Dr. Terry Gaasterland (UCSD) as part of an ARRA grant. These samples were selected to mirror the distribution of the entire set of Duke patients for variables such as age, cup-to-disc ratio, CCT, and IOP. From these 75 patients, 43 were selected for our study and an additional seven patients chosen at random, for a total 50 patients from Duke. From the 219 Duke controls, 50 were selected to match the age (at the time of blood draw) and sex of the 50 Duke POAG patients. From the NEIGHBOR control samples from MEEI, 27 were selected who best matched the age (at blood draw), time since sample collection and sex of the POAG probands from GLAUGEN. Additional individual-level phenotype and genotype data may be obtained through the authorized access portal of phs000238 (Neighbor - Glaucoma GWAS Study).]]>
Unrelated individuals were selected as cases or controls for this study. All subjects consented to sharing their samples. Both cases and controls were examined by a trained ophthalmologist. All cases and controls were at least 35 years old and all were Caucasian. Cases had either reproducible visual field loss in at least one eye in a nerve fiber layer distribution on two independent reliable visual fields, or a vertical cup to disc ratio (CDR) of at least 0.8 in the one eye. For automated visual fields, a reliable visual field was defined by fixation loss ≤ 33%, false positive rate ≤ 20% and false negative rate ≤ 20%. Intraocular pressure was noted for all cases, but was not part of the case definition. Exclusion criteria for cases included: myopia of −8D or greater, clinical findings suggestive of secondary glaucomas (pigment dispersion, exfoliation and anterior segment dysgenesis) and narrow filtration angles. Controls did not have a family history of glaucoma, had intraocular pressures less than 21 mmHg, had vertical cup to disc ratios of less than 0.7 and CDR asymmetry of less than 0.2. Controls also did not have any evidence of secondary glaucomas or narrow filtration angles.]]>