title: Aberrant DNA methylation of matrix remodeling and cell adhesion related genes in pterygium.
abstract: BACKGROUND
  Pterygium is a common ocular surface disease characterized by abnormal epithelial and fibrovascular proliferation, invasion, and matrix remodeling. This lesion, which migrates from the periphery to the center of the cornea, impairs vision and causes considerable irritation. The mechanism of pterygium formation remains ambiguous, and current treatment is solely surgical excision, with a significant risk of recurrence after surgery. Here, we investigate the role of methylation in DNA sequences that regulate matrix remodeling and cell adhesion in pterygium formation.
  
  
  RESULTS
  Pterygium and uninvolved conjunctiva samples were obtained from the same eye of patients undergoing surgery. The EpiTYPER Sequenom technology, based on differential base cleavage and bisulfite sequencing was used to evaluate the extent of methylation of 29 matrix and adhesion related genes. In pterygium, three CpG sites at -268, -32 and -29 bp upstream of transglutaminase 2 (TGM-2) transcription initiation were significantly hypermethylated (p<0.05), whereas hypomethylation was detected at CpGs +484 and +602 bp downstream of matrix metalloproteinase 2 (MMP-2) transcription start site, and -809, -762, -631 and -629 bp upstream of the CD24 transcription start site. RT-qPCR, western blot and immunofluorescent staining showed that transcript and protein expression were reduced for TGM-2 and increased for MMP-2 and CD24. Inhibition of methylation in cultured conjunctival epithelial cells increased these transcripts.
  
  
  CONCLUSIONS
  We found regions of aberrant DNA methylation which were consistent with alteration of TGM-2, MMP-2, and CD24 transcript and protein expression, and that inhibition of methylation in cultured cells can increase the expression of these genes. Since these genes were related to cell adhesion and matrix remodeling, dysregulation may lead to fibroblastic and neovascular changes and pterygium formation. These results have implications for the prognostication of pterygium in clinical practice, for example, detection of epigenetic changes may have a role in predicting post surgical recurrence of aggressive lesions.
authors.affiliation: Ocular Wound Healing and Therapeutics Laboratory, Singapore Eye Research Institute, Singapore, Singapore.
authors.forename: Andri K
authors.initials: AK
authors.lastname: Riau
authors.forename: Tina T
authors.initials: TT
authors.lastname: Wong
authors.forename: Wanwen
authors.initials: W
authors.lastname: Lan
authors.forename: Sharon N
authors.initials: SN
authors.lastname: Finger
authors.forename: Shyam S
authors.initials: SS
authors.lastname: Chaurasia
authors.forename: Ai Hua
authors.initials: AH
authors.lastname: Hou
authors.forename: Silin
authors.initials: S
authors.lastname: Chen
authors.forename: Shang Juan
authors.initials: SJ
authors.lastname: Yu
authors.forename: Louis
authors.initials: L
authors.lastname: Tong
mesh_terms: D051927:CD24 Antigen / Q000235:genetics / Q000378:metabolism; D002448:Cell Adhesion / Q000235:genetics; D002478:Cells, Cultured; D003228:Conjunctiva / Q000378:metabolism / Q000473:pathology; D019175:DNA Methylation / Q000502:physiology; D057890:Epigenomics; D005109:Extracellular Matrix / Q000235:genetics* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D053263:Gene Regulatory Networks; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011625:Pterygium / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011503:Transglutaminases / Q000235:genetics / Q000378:metabolism; D014945:Wound Healing / Q000235:genetics / Q000502:physiology
chemical_list: D051927:CD24 Antigen; C497889:CD24 protein, human; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D020778:Matrix Metalloproteinase 2; D019204:GTP-Binding Proteins