title: Notch1 regulates progenitor cell proliferation and differentiation during mouse yolk sac hematopoiesis.
abstract: Loss-of-function studies have demonstrated the essential role of Notch in definitive embryonic mouse hematopoiesis. We report here the consequences of Notch gain-of-function in mouse embryo hematopoiesis, achieved by constitutive expression of Notch1 intracellular domain (N1ICD) in angiopoietin receptor tyrosine kinase receptor-2 (Tie2)-derived enhanced green fluorescence protein (EGFP(+)) hematovascular progenitors. At E9.5, N1ICD expression led to the absence of the dorsal aorta hematopoietic clusters and of definitive hematopoiesis. The EGFP(+) transient multipotent progenitors, purified from E9.5 to 10.5 Tie2-Cre;N1ICD yolk sac (YS) cells, had strongly reduced hematopoietic potential, whereas they had increased numbers of hemogenic endothelial cells. Late erythroid cell differentiation stages and mature myeloid cells (Gr1(+), MPO(+)) were also strongly decreased. In contrast, EGFP(+) erythro-myeloid progenitors, immature and intermediate differentiation stages of YS erythroid and myeloid cell lineages, were expanded. Tie2-Cre;N1ICD YS had reduced numbers of CD41(++) megakaryocytes, and these produced reduced below-normal numbers of immature colonies in vitro and their terminal differentiation was blocked. Cells from Tie2-Cre;N1ICD YS had a higher proliferation rate and lower apoptosis than wild-type (WT) YS cells. Quantitative gene expression analysis of FACS-purified EGFP(+) YS progenitors revealed upregulation of Notch1-related genes and alterations in genes involved in hematopoietic differentiation. These results represent the first in vivo evidence of a role for Notch signaling in YS transient definitive hematopoiesis. Our results show that constitutive Notch1 activation in Tie2(+) cells hampers YS hematopoiesis of E9.5 embryos and demonstrate that Notch signaling regulates this process by balancing the proliferation and differentiation dynamics of lineage-restricted intermediate progenitors.
authors.affiliation: 1] Immunology Department, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Ctra. Majadahonda-Pozuelo, km 2, 28220 Madrid, Spain [2] Centro de Biología Molecular, Consejo Superior de Investigaciones Científicas (CBM-CSIC), Campus de Cantoblanco, 28049 Madrid, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Cortegano
authors.affiliation: Program of Cardiovascular Developmental Biology, Department of Cardiovascular Development and Repair, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Melgar-Rojas
authors.affiliation: Program of Cardiovascular Developmental Biology, Department of Cardiovascular Development and Repair, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Luna-Zurita
authors.affiliation: Program of Cardiovascular Developmental Biology, Department of Cardiovascular Development and Repair, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Siguero-Álvarez
authors.affiliation: Centro de Biología Molecular, Consejo Superior de Investigaciones Científicas (CBM-CSIC), Campus de Cantoblanco, 28049 Madrid, Spain.
authors.forename: M A R
authors.initials: MA
authors.lastname: Marcos
authors.affiliation: Immunology Department, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Ctra. Majadahonda-Pozuelo, km 2, 28220 Madrid, Spain.
authors.forename: M L
authors.initials: ML
authors.lastname: Gaspar
authors.affiliation: Program of Cardiovascular Developmental Biology, Department of Cardiovascular Development and Repair, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: de la Pompa
mesh_terms: D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D047108:Embryonic Development; D041905:Erythroid Cells / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D055015:Megakaryocyte-Erythroid Progenitor Cells / Q000502:physiology; D008533:Megakaryocytes / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D051881:Receptor, Notch1 / Q000502:physiology*; D042787:Receptor, TIE-2 / Q000235:genetics / Q000378:metabolism; D015017:Yolk Sac / Q000166:cytology*
chemical_list: C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; D042787:Receptor, TIE-2; C079086:Tek protein, mouse