Hypoxia affects mesoderm and enhances hemangioblast specification during early development.
Hypoxia Inducible Factor (HIF), consisting of HIF1alpha and ARNT (HIF1beta) subunits, activates multiple genes in response to oxygen (O(2)) deprivation. Arnt(-/-) mice exhibit substantial defects in blood cell and vessel development. We demonstrate that hypoxia accelerates the expression of Brachyury (a mesoderm-specific transcription factor), BMP4 (a mesoderm-promoting growth factor) and FLK1 (a marker of hemangioblasts, the bipotential progenitor of endothelial and hematopoietic cells) in differentiating ES cell cultures. Significantly, proliferation of embryonic hemangioblasts (BL-CFCs) is regulated by hypoxia, as Arnt(+/+) ES cells generate increased numbers of FLK1(+) cells, and BL-CFCs with accelerated kinetics in response to low O(2). This response is HIF-dependent as Arnt(-/-) ES cells produce fewer FLK1(+) cells and BL-CFCs, under both normoxic and hypoxic conditions. Interestingly, this defect is rescued when Arnt(-/-) ES cells are co-cultured with Arnt(+/+) ES cells. Vegf(+/-)or Vegf(-/-) ES cells generate proper numbers of FLK1(+) cells but fewer BL-CFCs, suggesting that additional factors regulated by HIF (other than VEGF) are involved in these early events. Thus, hypoxic responses are important for the establishment of various progenitor cells, including early mesoderm and its differentiation into hemangioblasts. Together these data suggest that ineffective responses to hypoxia in Arnt(-/-) embryos abrogate proper cardiovascular development during early embryogenesis, including the pathways controlling hemangioblast differentiation.
Ramírez-Bergeron
Diana L
DL
Howard Hughes Medical Institute and Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Runge
Anja
A
Dahl
Karen D Cowden
KD
Fehling
Hans Joerg
HJ
Keller
Gordon
G
Simon
M Celeste
MC
D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000235:genetics; D002452:Cell Count; D002454:Cell Differentiation; D002455:Cell Division; D002478:Cells, Cultured; D018920:Coculture Techniques; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D005326:Fetal Proteins / Q000235:genetics; D017353:Gene Deletion; D006133:Growth Substances / Q000494:pharmacology; D000860:Hypoxia / Q000235:genetics / Q000503:physiopathology*; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007700:Kinetics; D008648:Mesoderm / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins / Q000235:genetics; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism; D020825:T-Box Domain Proteins / Q000235:genetics; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000172:deficiency / Q000235:genetics; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000235:genetics / Q000378:metabolism; D000098908:Brachyury Protein
D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D005326:Fetal Proteins; D006133:Growth Substances; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; D000098908:Brachyury Protein; C497397:Arnt protein, mouse; C525810:Bmp4 protein, mouse; C497443:Hif1a protein, mouse