title: DNA methylation is associated with altered gene expression in AMD.
abstract: OBJECTIVE
  Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. Evidence suggests oxidative stress plays a role in the disease. To assess the potential contribution of epigenetic regulation of antioxidant genes relevant to AMD pathogenesis, we evaluated DNA methylation, a tissue-specific genetic modulation that affects gene expression.
  
  
  METHODS
  Using the Infinium HumanMethylation27 Illumina platform, we performed DNA bisulfite sequencing to compare the methylation status in postmortem retina pigment epithelium (RPE)/choroid between patients with AMD and age-matched controls. Gene expression was assessed with the Affymetrix Exon Array. TaqMan gene expression assays were used for relative quantification (RT-PCR) confirmation of the expression array results: Glutathione S-transferase isoform mu1 (GSTM1) and mu5 (GSTM5) promoter methylation was confirmed by CpG island bisulfite pyrosequencing. To assess protein levels and localization, we used Western analysis, immunohistochemistry, and immunofluorescence with murine and human samples.
  
  
  RESULTS
  The mRNA levels of GSTM1 and GSTM5 were significantly reduced in AMD versus age-matched controls in RPE/choroid and neurosensory retina (NSR), which corresponded to hypermethylation of the GSTM1 promoter. mRNA and protein levels were decreased (RPE to a greater extent than NSR) in AMD postmortem samples, irrespective of age. Immunohistochemistry and immunofluorescence confirm the presence of the enzymes in the NSR and RPE.
  
  
  CONCLUSIONS
  Comparison of DNA methylation, together with mRNA levels, revealed significant differences between AMD versus normal retinas. The evidence presented suggests that GSTM1 and GSTM5 undergo epigenetic repression in AMD RPE/choroid, which may increase susceptibility to oxidative stress in AMD retinas.
authors.affiliation: FM Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA. hunter.allan.a@gmail.com
authors.forename: Allan
authors.initials: A
authors.lastname: Hunter
authors.forename: Paul A
authors.initials: PA
authors.lastname: Spechler
authors.forename: Alyssa
authors.initials: A
authors.lastname: Cwanger
authors.forename: Ying
authors.initials: Y
authors.lastname: Song
authors.forename: Zhe
authors.initials: Z
authors.lastname: Zhang
authors.forename: Gui-Shuang
authors.initials: GS
authors.lastname: Ying
authors.forename: Anna K
authors.initials: AK
authors.lastname: Hunter
authors.forename: Edwin
authors.initials: E
authors.lastname: Dezoeten
authors.forename: Joshua L
authors.initials: JL
authors.lastname: Dunaief
mesh_terms: D015153:Blotting, Western; D002829:Choroid / Q000378:metabolism; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005091:Exons / Q000235:genetics; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000502:physiology*; D005982:Glutathione Transferase / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D055213:Retinal Pigment Epithelium / Q000378:metabolism; D057135:Wet Macular Degeneration / Q000235:genetics* / Q000473:pathology
chemical_list: D005982:Glutathione Transferase; D012333:RNA, Messenger; C524366:GSTM5 protein, human