title: RUNX1B Expression Is Highly Heterogeneous and Distinguishes Megakaryocytic and Erythroid Lineage Fate in Adult Mouse Hematopoiesis.
abstract: The Core Binding Factor (CBF) protein RUNX1 is a master regulator of definitive hematopoiesis, crucial for hematopoietic stem cell (HSC) emergence during ontogeny. RUNX1 also plays vital roles in adult mice, in regulating the correct specification of numerous blood lineages. Akin to the other mammalian Runx genes, Runx1 has two promoters P1 (distal) and P2 (proximal) which generate distinct protein isoforms. The activities and specific relevance of these two promoters in adult hematopoiesis remain to be fully elucidated. Utilizing a dual reporter mouse model we demonstrate that the distal P1 promoter is broadly active in adult hematopoietic stem and progenitor cell (HSPC) populations. By contrast the activity of the proximal P2 promoter is more restricted and its upregulation, in both the immature Lineage- Sca1high cKithigh (LSK) and bipotential Pre-Megakaryocytic/Erythroid Progenitor (PreMegE) populations, coincides with a loss of erythroid (Ery) specification. Accordingly the PreMegE population can be prospectively separated into "pro-erythroid" and "pro-megakaryocyte" populations based on Runx1 P2 activity. Comparative gene expression analyses between Runx1 P2+ and P2- populations indicated that levels of CD34 expression could substitute for P2 activity to distinguish these two cell populations in wild type (WT) bone marrow (BM). Prospective isolation of these two populations will enable the further investigation of molecular mechanisms involved in megakaryocytic/erythroid (Mk/Ery) cell fate decisions. Having characterized the extensive activity of P1, we utilized a P1-GFP homozygous mouse model to analyze the impact of the complete absence of Runx1 P1 expression in adult mice and observed strong defects in the T cell lineage. Finally, we investigated how the leukemic fusion protein AML1-ETO9a might influence Runx1 promoter usage. Short-term AML1-ETO9a induction in BM resulted in preferential P2 upregulation, suggesting its expression may be important to establish a pre-leukemic environment.
authors.affiliation: Cancer Research UK Stem Cell Biology Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, United Kingdom.
authors.forename: Julia E
authors.initials: JE
authors.lastname: Draper
authors.affiliation: Cancer Research UK Stem Cell Biology Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, United Kingdom.|Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.|Centre for Epigenetics, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Patrycja
authors.initials: P
authors.lastname: Sroczynska
authors.affiliation: Cancer Research UK Stem Cell Biology Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, United Kingdom.
authors.forename: Olga
authors.initials: O
authors.lastname: Tsoulaki
authors.affiliation: Cancer Research UK Applied Computational Biology and Bioinformatics Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, United Kingdom.
authors.forename: Hui Sun
authors.initials: HS
authors.lastname: Leong
authors.affiliation: Cancer Research UK Stem Cell Biology Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, United Kingdom.
authors.forename: Muhammad Z H
authors.initials: MZ
authors.lastname: Fadlullah
authors.affiliation: Cancer Research UK Applied Computational Biology and Bioinformatics Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, United Kingdom.
authors.forename: Crispin
authors.initials: C
authors.lastname: Miller
authors.affiliation: Cancer Research UK Stem Cell Haematopoiesis Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, United Kingdom.
authors.forename: Valerie
authors.initials: V
authors.lastname: Kouskoff
authors.affiliation: Cancer Research UK Stem Cell Biology Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, United Kingdom.
authors.forename: Georges
authors.initials: G
authors.lastname: Lacaud
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D019070:Cell Lineage / Q000235:genetics*; D050676:Core Binding Factor Alpha 2 Subunit / Q000096:biosynthesis* / Q000235:genetics; D004622:Embryo, Mammalian; D018507:Gene Expression Regulation, Developmental; D006410:Hematopoiesis / Q000235:genetics*; D006412:Hematopoietic Stem Cells; D008533:Megakaryocytes / Q000166:cytology; D051379:Mice; D011401:Promoter Regions, Genetic; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D050676:Core Binding Factor Alpha 2 Subunit; C493726:Runx1 protein, mouse