title: Water Channels Aquaporin 4 and -1 Expression in Subependymoma Depends on the Localization of the Tumors.
abstract: BACKGROUND
  We analyzed aquaporin 4 and -1 expression in subependymomas, benign and slow growing brain tumors WHO grade I. Ten subependymoma cases were investigated, five of the fossa inferior and five of the fossa superior.
  
  
  RESULTS
  Using immunohistochemistry, we observed different aquaporin expression patterns depending on localization: aquaporin 4 and -1 were detected in infratentorial subependymomas in the entire tumor tissue. In contrast, supratentorial subependymomas revealed aquaporin 4 and -1 expression only in border areas of the tumor. PCR analyses however showed no difference in aquaporin 4 expression between all subependymomas independent of localization but at higher levels than in normal brain. In contrast, aquaporin 1 RNA levels were found to be higher only in infratentorial samples compared to supratentorial and normal brain samples. The reason for the different distribution pattern of aquaporin 4 in subependymomas still remains unclear. On the cellular level, aquaporin 4 was redistributed on the surface of the tumor cells, and in freeze fracture replicas no orthogonal arrays of particles were found. This was similar to our previous findings in malignant glioblastomas. From these studies, we know that extracellular matrix molecules within the tumor like agrin and its receptor alpha-dystroglycan are involved in forming orthogonal arrays of particles. In subependymomas neither agrin nor alpha-dystroglycan were detected around blood vessels.
  
  
  CONCLUSIONS
  Taken together, we show in this study that in the benign subependymomas aquaporins 1 and 4 are dramatically redistributed and upregulated. We speculate that extracellular environments of infra- and supratentorial subependymomas are different and lead to different distribution patterns of aquaporin 4 and -1.
authors.affiliation: Department of Neurosurgery, University of Tuebingen, Tuebingen, Germany.
authors.forename: Susan
authors.initials: S
authors.lastname: Noell
authors.affiliation: Institute of Pathology and Neuropathology, University of Tuebingen, Tuebingen, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Fallier-Becker
authors.affiliation: Institute of Clinical Anatomy and Cell Analysis, University of Tuebingen, Tuebingen, Germany.
authors.forename: Andreas F
authors.initials: AF
authors.lastname: Mack
authors.affiliation: Institute of Pathology and Neuropathology, University of Tuebingen, Tuebingen, Germany.
authors.forename: Maike
authors.initials: M
authors.lastname: Hoffmeister
authors.affiliation: Institute of Pathology and Neuropathology, University of Tuebingen, Tuebingen, Germany.
authors.forename: Rudi
authors.initials: R
authors.lastname: Beschorner
authors.affiliation: Department of Neurosurgery, University of Marburg, Marburg, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Ritz
mesh_terms: D000328:Adult; D000368:Aged; D051398:Aquaporin 1 / Q000096:biosynthesis*; D051401:Aquaporin 4 / Q000096:biosynthesis*; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018315:Glioma, Subependymal / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000096:biosynthesis*
chemical_list: C496020:AQP1 protein, human; C496030:AQP4 protein, human; D051401:Aquaporin 4; D009363:Neoplasm Proteins; D051398:Aquaporin 1