title: HIF1A is essential for the development of the intermediate plexus of the retinal vasculature.
abstract: OBJECTIVE
  HIF1A is one of the major transcription factors that regulate tissue response to low oxygen tension. It controls expression of a large number of genes involved in cell survival, proliferation, angiogenesis, and other cellular processes. HIF1A is present at increased levels in the early postnatal retina. In this study its potential function during postnatal development of the mouse retina and retinal vasculature was analyzed.
  
  
  METHODS
  A mouse line was generated with a Cre-mediated Hif1a knockdown in the peripheral retina. Retinal morphology and vasculature were analyzed in sections and flat mount preparations. Gene and protein expression were determined by real-time PCR and Western blot analysis.
  
  
  RESULTS
  The Cre-mediated knockdown caused a significant reduction in Hif1a gene expression and HIF1A protein levels in the early postnatal retina. Retinal morphology was normal but the Hif1a knockdown prevented the formation of the intermediate vascular plexus in the peripheral retina. The primary plexus and the outer plexus were less affected. The Hif1a knockdown did not affect expression of such angiogenesis-related genes as vascular endothelial growth factor (Vegf) but strongly induced expression of erythropoietin (Epo). At the protein level, EPAS1 (HIF2A) was stabilized in the Hif1a knockdown mice.
  
  
  CONCLUSIONS
  The results suggest that HIF1A may be directly or indirectly required for normal development of the retinal vasculature, especially of the intermediate plexus. EPO but not VEGF may play a significant role in the development of this phenotype. HIF1A may not be the main factor that regulates Vegf expression during retinal development in the mouse.
authors.affiliation: Lab for Retinal Cell Biology, Department of Ophthalmology, University of Zurich, Zurich, Switzerland. christian.caprara@usz.ch
authors.forename: Christian
authors.initials: C
authors.lastname: Caprara
authors.forename: Markus
authors.initials: M
authors.lastname: Thiersch
authors.forename: Christina
authors.initials: C
authors.lastname: Lange
authors.forename: Sandrine
authors.initials: S
authors.lastname: Joly
authors.forename: Marijana
authors.initials: M
authors.lastname: Samardzija
authors.forename: Christian
authors.initials: C
authors.lastname: Grimm
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D015153:Blotting, Western; D017931:DNA Primers / Q000737:chemistry; D015536:Down-Regulation; D004921:Erythropoietin / Q000235:genetics; D019084:Fluorescent Antibody Technique, Indirect; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic / Q000502:physiology*; D012171:Retinal Vessels / Q000254:growth & development* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D017931:DNA Primers; D004921:Erythropoietin; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D042461:Vascular Endothelial Growth Factor A; D000099162:Endothelial PAS Domain-Containing Protein 1; C497443:Hif1a protein, mouse; C467480:vascular endothelial growth factor A, mouse