title: ALK1 signalling analysis identifies angiogenesis related genes and reveals disparity between TGF-beta and constitutively active receptor induced gene expression.
abstract: BACKGROUND
  TGF-beta1 is an important angiogenic factor involved in the different aspects of angiogenesis and vessel maintenance. TGF-beta signalling is mediated by the TbetaRII/ALK5 receptor complex activating the Smad2/Smad3 pathway. In endothelial cells TGF-beta utilizes a second type I receptor, ALK1, activating the Smad1/Smad5 pathway. Consequently, a perturbance of ALK1, ALK5 or TbetaRII activity leads to vascular defects. Mutations in ALK1 cause the vascular disorder hereditary hemorrhagic telangiectasia (HHT).
  
  
  METHODS
  The identification of ALK1 and not ALK5 regulated genes in endothelial cells, might help to better understand the development of HHT. Therefore, the human microvascular endothelial cell line HMEC-1 was infected with a recombinant constitutively active ALK1 adenovirus, and gene expression was studied by using gene arrays and quantitative real-time PCR analysis.
  
  
  RESULTS
  After 24 hours, 34 genes were identified to be up-regulated by ALK1 signalling. Analysing ALK1 regulated gene expression after 4 hours revealed 13 genes to be up- and 2 to be down-regulated. Several of these genes, including IL-8, ET-1, ID1, HPTPeta and TEAD4 are reported to be involved in angiogenesis. Evaluation of ALK1 regulated gene expression in different human endothelial cell types was not in complete agreement. Further on, disparity between constitutively active ALK1 and TGF-beta1 induced gene expression in HMEC-1 cells and primary HUVECs was observed.
  
  
  CONCLUSIONS
  Gene array analysis identified 49 genes to be regulated by ALK1 signalling and at least 14 genes are reported to be involved in angiogenesis. There was substantial agreement between the gene array and quantitative real-time PCR data. The angiogenesis related genes might be potential HHT modifier genes. In addition, the results suggest endothelial cell type specific ALK1 and TGF-beta signalling.
authors.affiliation: University Hospital Mannheim, Germany. a.lux@hs-mannhei.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Lux
authors.forename: Fiona
authors.initials: F
authors.lastname: Salway
authors.forename: Holly K
authors.initials: HK
authors.lastname: Dressman
authors.forename: Gabriele
authors.initials: G
authors.lastname: Kröner-Lux
authors.forename: Mathias
authors.initials: M
authors.lastname: Hafner
authors.forename: Philip J R
authors.initials: PJ
authors.lastname: Day
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Marchuk
authors.forename: John
authors.initials: J
authors.lastname: Garland
mesh_terms: D030301:Activin Receptors, Type II / Q000502:physiology*; D002460:Cell Line; D002478:Cells, Cultured; D000090702:Constitutive Androstane Receptor; D042783:Endothelial Cells; D004730:Endothelium, Vascular / Q000166:cytology; D005786:Gene Expression Regulation / Q000235:genetics*; D006801:Humans; D018919:Neovascularization, Physiologic / Q000235:genetics*; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology*; D053773:Transforming Growth Factor beta1
chemical_list: D000090702:Constitutive Androstane Receptor; D018160:Receptors, Cytoplasmic and Nuclear; C508960:TGFB1 protein, human; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C425364:ACVRL1 protein, human; D030301:Activin Receptors, Type II