title: Acute postnatal ablation of Hif-2alpha results in anemia.
abstract: Adaptive transcriptional responses to oxygen deprivation (hypoxia) are mediated by the hypoxia-inducible factors (HIFs), heterodimeric transcription factors composed of two basic helix-loop-helix-PAS family proteins. The transcriptional activity of HIF is determined by the hypoxic stabilization of the HIF-alpha proteins. HIF-1alpha and HIF-2alpha exhibit high sequence homology but have different mRNA expression patterns; HIF-1alpha is expressed ubiquitously whereas HIF-2alpha expression is more restricted to certain tissues, e.g., the endothelium, lung, brain, and neural crest derivatives. Germ-line deletion of either HIF subunit is embryonic lethal with unique features suggesting important roles for both HIF-alpha isoforms. Global deletion of Hif-2alpha results in distinct phenotypes depending on the mouse strain used for the mutation, clearly demonstrating an important role for HIF-2alpha in mouse development. The function of HIF-2alpha in adult life, however, remains incompletely understood. In this study, we describe the generation of a conditional murine Hif-2alpha allele and the effect of its acute postnatal ablation. Under very stringent conditions, we ablate Hif-2alpha after birth and compare the effect of acute global deletion of Hif-2alpha and Hif-1alpha. Our results demonstrate that HIF-2alpha plays a critical role in adult erythropoiesis, with acute deletion leading to anemia. Furthermore, although HIF-1alpha was first purified and cloned based on its affinity for the human erythropoietin (EPO) 3' enhancer hypoxia response element (HRE) and regulates Epo expression during mouse embryogenesis, HIF-2alpha is the critical alpha isoform regulating Epo under physiologic and stress conditions in adults.
authors.affiliation: Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Michaela
authors.initials: M
authors.lastname: Gruber
authors.forename: Cheng-Jun
authors.initials: CJ
authors.lastname: Hu
authors.forename: Randall S
authors.initials: RS
authors.lastname: Johnson
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Brown
authors.forename: Brian
authors.initials: B
authors.lastname: Keith
authors.forename: M Celeste
authors.initials: MC
authors.lastname: Simon
mesh_terms: D000740:Anemia / Q000209:etiology*; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000172:deficiency* / Q000502:physiology; D004920:Erythropoiesis; D004921:Erythropoietin / Q000235:genetics*; D005786:Gene Expression Regulation; D000860:Hypoxia; D051379:Mice; D018345:Mice, Knockout; D010641:Phenotype; D020033:Protein Isoforms / Q000502:physiology; D020218:Response Elements; D013312:Stress, Physiological / Q000235:genetics; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004921:Erythropoietin; D020033:Protein Isoforms; D000099162:Endothelial PAS Domain-Containing Protein 1