title: von Hippel-Lindau gene disruption in mouse pancreatic progenitors and its consequences on endocrine differentiation in vivo: importance of HIF1-α and VEGF-A upregulation.
abstract: OBJECTIVE
  Different studies have linked hypoxia to embryonic development. Specifically, when embryonic pancreases are cultured ex vivo under hypoxic conditions (3% O2), beta cell development is impaired. Different cellular signalling pathways are involved in adaptation to hypoxia, including the ubiquitous hypoxia-inducible-factor 1-α (HIF1-α) pathway. We aimed to analyse the effects of HIF1-α stabilisation on fetal pancreas development in vivo.
  
  
  METHODS
  We deleted the Vhl gene, which encodes von Hippel-Lindau protein (pVHL), a factor necessary for HIF1-α degradation, by crossing Vhl-floxed mice with Sox9-Cre mice.
  
  
  RESULTS
  HIF1-α was stabilised in pancreatic progenitor cells in which the HIF pathway was induced. The number of neurogenin-3 (NGN3)-expressing cells was reduced and consequently endocrine development was altered in Vhl knockout pancreases. HIF1-α stabilisation induced Vegfa upregulation, leading to increased vascularisation. To investigate the impact of increased vascularisation on NGN3 expression, we used a bioassay in which Vhl mutant pancreases were cultured with or without vascular endothelial growth factor (VEGF) receptor 2 (VEGF-R2) inhibitors (e.g. Ki8751). Ex vivo analysis showed that Vhl knockout pancreases developed fewer NGN3-positive cells compared with controls. Interestingly, this effect was blocked when vascularisation was inhibited in the presence of VEGF-R2 inhibitors.
  
  
  CONCLUSIONS
  Our data demonstrate that HIF1-α negatively controls beta cell differentiation in vivo by regulating NGN3 expression, and that this effect is mediated by signals from blood vessels.
authors.affiliation: U1016 Inserm/Institut Cochin, Groupe Hospitalier Cochin Port-Royal, Bâtiment Cassini, 123 Boulevard du Port-Royal, 75014, Paris, France.
authors.forename: Andrea
authors.initials: A
authors.lastname: Soggia
authors.forename: Cyrille
authors.initials: C
authors.lastname: Ramond
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Akiyama
authors.forename: Raphaël
authors.initials: R
authors.lastname: Scharfmann
authors.forename: Bertrand
authors.initials: B
authors.lastname: Duvillie
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D005260:Female; D005434:Flow Cytometry; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D010179:Pancreas / Q000166:cytology* / Q000196:embryology; D011247:Pregnancy; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009419:Nerve Tissue Proteins; D042461:Vascular Endothelial Growth Factor A; D051794:Von Hippel-Lindau Tumor Suppressor Protein; C407737:Neurog3 protein, mouse; C494469:VHL protein, mouse