title: MLH1 and MSH2 expression in pterygia.
abstract: OBJECTIVE
  Pterygia have been reported to share some of the genetic defects seen in cancers, including microsatellite instability (MSI). We examined pterygia for the presence of proteins typically missing or defective in adenocarcinomas with MSI. We also performed microsatellite analysis on DNA from pterygia to test for instability in the size of the microsatellites, using markers conventionally used to characterize MSI in tumors (Bethesda convention markers).
  
  
  METHODS
  We examined 13 pterygia by immunohistochemistry for MLH1 and MSH2, 2 proteins involved in DNA mismatch repair. In addition, we amplified the pterygial DNA with primers specific for 5 Bethesda markers (BAT25, BAT26, D2S123, D5S346, and D17S250).
  
  
  RESULTS
  MLH1 staining was present at low levels in the basal cells of the cornea and migrating limbal cells of the pterygia. MSH2 staining was present in basal and in maturing epithelial cells of the cornea and migrating limbal cells of pterygia. We observed no reproducible examples of MSI or loss of heterozygosity (LOH).
  
  
  CONCLUSIONS
  We were unable to confirm the presence of MSI and LOH by using the markers we examined. MSH2 staining appeared to be normal in pterygia. MLH1 staining was present but in reduced amounts compared with that seen in the conjunctiva.
authors: Division of Gastroenterology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA. barbara.schneider@vanderbilt.edu
authors: Barbara G
authors: BG
authors: Schneider
authors: Deshdeepak
authors: D
authors: Sahni
authors: Juan C
authors: JC
authors: Torres
authors: Nicholas
authors: N
authors: Dushku
authors: Ted W
authors: TW
authors: Reid
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000368:Aged; D020137:Base Pair Mismatch / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair / Q000235:genetics; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D019656:Loss of Heterozygosity; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011625:Pterygium / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C088996:PMS1 protein, human; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins