title: Partial rescue of defects in Cited2-deficient embryos by HIF-1alpha heterozygosity.
abstract: Hypoxia inducible factor-1 (HIF-1) initiates key cellular and tissue responses to physiological and pathological hypoxia. Evidence from in vitro and structural analyses supports a critical role for Cited2 in down-regulating HIF-1-mediated transcription by competing for binding with oxygen-sensitive HIF-1alpha to transcriptional co-activators CBP/p300. We previously detected elevated expression of HIF-1 target genes in Cited2(-/-) embryonic hearts, indicating that Cited2 inhibits HIF-1 transactivation in vivo. In this study, we show for the first time that highly hypoxic cardiac regions in mouse embryos corresponded to the sites of defects in Cited2(-/-) embryos and that defects of the outflow tract, interventricular septum, cardiac vasculature, and hyposplenia were largely rescued by HIF-1alpha haploinsufficiency. The hypoxia of the outflow tract and interventricular septum peaked at E13.5 and dissipated by E15.5 in wild-type hearts, but persisted in E15.5 Cited2(-/-) hearts. The persistent hypoxia and abnormal vasculature in the myocardium of interventricular septum in E15.5 Cited2(-/-) hearts were rescued with decreased HIF-1alpha gene dosage. Accordingly, mRNA levels of HIF-1-responsive genes were reduced in Cited2(-/-) embryonic hearts by HIF-1alpha heterozygosity. These findings suggest that a precise level of HIF-1 transcriptional activity critical for normal development is triggered by differential hypoxia and regulated through feedback inhibition by Cited2.
authors.affiliation: Department of Pharmacology and Cancer Center, Case Western Reserve University, School of Medicine, W319, Cleveland, OH 44106, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Xu
authors.forename: Yongqiu
authors.initials: Y
authors.lastname: Doughman
authors.forename: Mona
authors.initials: M
authors.lastname: Turakhia
authors.forename: Weihong
authors.initials: W
authors.lastname: Jiang
authors.forename: Chad E
authors.initials: CE
authors.lastname: Landsettle
authors.forename: Faton H
authors.initials: FH
authors.lastname: Agani
authors.forename: Gregg L
authors.initials: GL
authors.lastname: Semenza
authors.forename: Michiko
authors.initials: M
authors.lastname: Watanabe
authors.forename: Yu-Chung
authors.initials: YC
authors.lastname: Yang
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D006579:Heterozygote; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009206:Myocardium / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000378:metabolism
chemical_list: C110087:Cited2 protein, mouse; D004268:DNA-Binding Proteins; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012097:Repressor Proteins; D015534:Trans-Activators; D042461:Vascular Endothelial Growth Factor A