title: The transcription factor HOXC9 regulates endothelial cell quiescence and vascular morphogenesis in zebrafish via inhibition of interleukin 8.
abstract: BACKGROUND
  The transcription factor HOXC9 belongs to the homeobox gene family acting as developmental morphogen in several species. HOXC9 is EXPRESSED in different vascular beds in vivo. Yet vascular functions of HOXC9 have not been studied.
  
  
  OBJECTIVE
  This study was aimed at characterizing HOXC9 functions in human vascular endothelial cells and in zebrafish vascular development.
  
  
  RESULTS
  HOXC9 was abundantly expressed in resting human umbilical vein endothelial cells and was downregulated by hypoxia. Overexpression of HOXC9 inhibited endothelial cell proliferation, migration, and tube formation in vitro. Expression profiling and chromatin immunoprecipitation experiments in human umbilical vein endothelial cells identified interleukin 8 as the major HOXC9 target and demonstrated the direct binding of HOXC9 to the interleukin 8 promotor. HOXC9 overexpression led to reduced endothelial interleukin 8 production, whereas HOXC9 silencing increased interleukin 8. The antimigratory and antiangiogenic effect of HOXC9 overexpression could be rescued by external interleukin 8 administration. Corresponding to the cellular experiments, endothelial-specific overexpression of HOXC9 and morpholino-based interleukin 8 loss-of-function experiments inhibited zebrafish vascular development.
  
  
  CONCLUSIONS
  The data identify HOXC9 as an endothelial cell active transcriptional repressor promoting the resting, antiangiogenic endothelial cell phenotype in an interleukin 8-dependent manner.
authors.affiliation: Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Stoll
authors.forename: Susanne
authors.initials: S
authors.lastname: Bartsch
authors.forename: Hellmut G
authors.initials: HG
authors.lastname: Augustin
authors.forename: Jens
authors.initials: J
authors.lastname: Kroll
mesh_terms: D000818:Animals; D002196:Capillaries / Q000166:cytology / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000502:physiology; D042783:Endothelial Cells / Q000166:cytology / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D016209:Interleukin-8 / Q000502:physiology*; D018919:Neovascularization, Physiologic / Q000502:physiology*; D014471:Umbilical Veins / Q000166:cytology; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; C522807:Hoxc9 protein, human; D016209:Interleukin-8; D029961:Zebrafish Proteins; C560325:hoxc9a protein, zebrafish