title: Myocilin is expressed in the glomerulus of the kidney and induced in mesangioproliferative glomerulonephritis.
abstract: BACKGROUND
  Myocilin is a 55 to 57 kD secreted glycoprotein and member of the olfactomedin protein family. It is expressed in high amounts in the outflow tissues of the aqueous humor in the eye where it is supposed to contribute to outflow resistance. Myocilin is mutated in some forms of primary open angle glaucoma and affected patients show very high intraocular pressures because of an increase in resistance to aqueous humor outflow. To obtain information, if myocilin may play a comparable role in other tissues with transendothelial fluid flow, we investigated its expression in the rat kidney.
  
  
  METHODS
  The expression of myocilin in the normal rat kidney and its changes during mesangioproliferative glomerulonephritis were investigated by immunohistochemistry, one- and two-dimensional gel electrophoresis with Western blotting, and reverse transcription-polymerase chain reaction (RT-PCR).
  
  
  RESULTS
  Myocilin and its mRNA were detected in isolated glomeruli. Immunohistochemistry showed specific labeling of glomerular cells, while tubular and interstitial regions were essentially negative. Double staining with the podocyte-specific markers synaptopodin and ezrin indicated that myocilin-positive cells were predominately podocytes. During mesangioproliferative glomerulonephritis, an induction of myocilin immunoreactivity was observed. Labeling for myocilin was now observed in activated mesangial cells and areas of glomerular sclerosis. In parallel cell culture experiments, mRNA for myocilin was detected in cultured murine podocytes and rat mesangial cells.
  
  
  CONCLUSIONS
  Myocilin is expressed in podocytes of the kidney and induced in mesangial cells during experimental mesangioproliferative glomerulonephritis. The specific function of myocilin in the kidney is not clear, but in a parallel to functions of other olfactomedin proteins, it might have a role in cell-cell adhesion and/or signaling processes.
authors.affiliation: Department of Anatomy, Molecular Anatomy and Embryology, University of Erlangen-Nürnberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Goldwich
authors.forename: Daniela C
authors.initials: DC
authors.lastname: Baulmann
authors.forename: Andreas
authors.initials: A
authors.lastname: Ohlmann
authors.forename: Cassandra
authors.initials: C
authors.lastname: Flügel-Koch
authors.forename: Harald
authors.initials: H
authors.lastname: Schöcklmann
authors.forename: Ernst R
authors.initials: ER
authors.lastname: Tamm
mesh_terms: D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000235:genetics* / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D005902:Glaucoma, Open-Angle / Q000235:genetics / Q000378:metabolism; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism; D015432:Glomerulonephritis, Membranoproliferative / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D006023:Glycoproteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007678:Kidney Glomerulus / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000099179:Myocilin
chemical_list: D003598:Cytoskeletal Proteins; D004247:DNA; D005136:Eye Proteins; D006023:Glycoproteins; D012333:RNA, Messenger; D000099179:Myocilin