title: Abnormal angiogenesis and responses to glucose and oxygen deprivation in mice lacking the protein ARNT.
abstract: The arylhydrocarbon-receptor nuclear translocator (ARNT) is a member of the basic-helix-loop-helix-PAS family of heterodimeric transcription factors which includes the arylhydrocarbon receptor (AHR), hypoxia-inducible factor-1alpha (HIF-1alpha) and the Drosophila single-minded protein (Sim). ARNT forms heterodimeric complexes with the arylhydrocarbon receptor, HIF-1alpha, Sim and the PAS protein Per. In response to environmental pollutants, AHR-ARNT heterodimers regulate genes involved in the metabolism of xenobiotics, whereas ARNT-HIF-1alpha heterodimers probably regulate those involved in the response to oxygen deprivation. By generating a targeted disruption of the Arnt locus in the mouse, we show here that Arnt-/- embryonic stem cells fail to activate genes that normally respond to low oxygen tension. Arnt-/- ES cells also failed to respond to a decrease in glucose concentration, indicating that ARNT is crucial in the response to hypoxia and to hypoglycaemia. Arnt-/- embryos were not viable past embryonic day 10.5 and showed defective angiogenesis of the yolk sac and branchial arches, stunted development and embryo wasting. The defect in blood vessel formation in Arnt-/- yolk sacs is similar to the angiogenic abnormalities reported for mice deficient in vascular endothelial growth factor or tissue factor. On the basis of these findings, we propose a model in which increasing tissue mass during organogenesis leads to the formation of hypoxic/nutrient-deprived cells, the subsequent activation of ARNT, and a concomitant increase in the expression of genes (including that encoding vascular endothelial growth factor) that promote vascularization of the developing yolk sac and solid tissues.
authors.affiliation: Department of Pathology, Howard Hughes Medical Institute, University of Chicago, Illinois 60637, USA.
authors.forename: E
authors.initials: E
authors.lastname: Maltepe
authors.forename: J V
authors.initials: JV
authors.lastname: Schmidt
authors.forename: D
authors.initials: D
authors.lastname: Baunoch
authors.forename: C A
authors.initials: CA
authors.lastname: Bradfield
authors.forename: M C
authors.initials: MC
authors.lastname: Simon
mesh_terms: D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D004268:DNA-Binding Proteins; D005314:Embryonic and Fetal Development / Q000502:physiology; D005313:Fetal Death; D018507:Gene Expression Regulation, Developmental; D018390:Gene Targeting; D005947:Glucose / Q000378:metabolism*; D018257:Helix-Loop-Helix Motifs; D051379:Mice; D016254:Mutagenesis, Insertional; D009389:Neovascularization, Pathologic / Q000209:etiology*; D010100:Oxygen / Q000378:metabolism*; D018336:Receptors, Aryl Hydrocarbon / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D013234:Stem Cells; D014157:Transcription Factors / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D015017:Yolk Sac / Q000098:blood supply
chemical_list: C497397:Arnt protein, mouse; D004268:DNA-Binding Proteins; D018336:Receptors, Aryl Hydrocarbon; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D005947:Glucose; D010100:Oxygen