Volume 6 Supplement 1

Epigenetics and Chromatin: Interactions and processes

Open Access

The hematopoietic master regulator RUNX1 reshapes the epigenetic landscape at the onset of hematopoiesis

  • Monika Lichtinger1, 2,
  • Nadine Obier2,
  • Richard Ingram1,
  • Rebecca Hannah3,
  • Maarten Hoogenkamp1, 2,
  • MS Vijayabaskar7,
  • Mengchu Wu6,
  • Salam A Assi7,
  • Daniel G Tenen5, 6,
  • David R Westhead7,
  • Valerie Kouskoff4,
  • Georges Lacaud4,
  • Berthold Göttgens3 and
  • Constanze Bonifer1, 2
Epigenetics & Chromatin20136(Suppl 1):O18

DOI: 10.1186/1756-8935-6-S1-O18

Published: 18 March 2013

Hematopoiesis in the embryo originates from mesodermal cells and proceeds via a common precursor (hemangioblast) of endothelial cells and blood cells. Hemangioblasts give rise to specialised endothelial cells (hemogenic endothelium) which subsequently undergo a transition into hematopoietic precursor cells. These cell fate decisions are governed by lineage-specific transcription factors, such as RUNX1, SCL/TAL1, FLI-1, PU.1 and C/EBP family members. In our work we study how dynamic shifts in the transcriptional regulatory network during this developmental pathway are regulated and how transcription factors control the activation of hematopoietic genes. We are also investigating, how these factors interact with each other and with the chromatin landscape.

To this end, we measured the genome-wide dynamics of chromatin alterations during the different steps of formation of the hematopoietic system from mesodermal cells using ES cell differentiation as model. We show that the hematopoietic program is already primed in the hemogenic endothelium as indicated by the binding of SCL/TAL1, FLI-1, C/EBPβ and enhancer-bound RNA-Polymerase II as well as the appearance of DNAsel hypersensitive sites. RUNX1 is absolutely required for the transition from hemogenic endothelium cells into hematopoietic progenitors. To obtain mechanistic information how this factor drives this process, we examined the assembly of hematopoietic transcription factors on their targets before and after this transition. Using an inducible system, we show that after induction RUNX1 binds to primed, but also novel elements and increases their histone acetylation. Moreover, RUNX1 initiates rapid global alterations in the binding patterns of SCL/TAL1 and FLI1, involving both the extinction of binding sites as well as the establishment of new sites. A significant fraction of new elements bind SCL/TAL1 and FLI1 in close proximity to RUNX1 in a pattern that is specific for hematopoietic cells.

RUNX1 has previously shown to be expendable in hematopoietic precursor cells once they have formed from the hemogenic endothelium. By precisely timed withdrawal studies we show that immediately after RUNX1 induction altered transcription factor complex assembly at many genes is still reversible, but not at all of them. Our experiments suggest a dynamic interplay between RUNX1 and other transcription factors that dictates the half-life of factor assemblies and their dependency on RUNX1 and give a fascinating insight into how a single master regulator shapes the epigenetic landscape.

Authors’ Affiliations

(1)
Section of Experimental Haematology Leeds Institute of Molecular Medicine, University of Leeds
(2)
School of Cancer Sciences, University of Birmingham
(3)
Cambridge Institute of Molecular Medicine
(4)
Paterson Institute for Cancer Research, University of Manchester
(5)
Cancer Science Institute, National University of Singapore
(6)
Harvard Stem Cell Institute, Harvard Medical School
(7)
Faculty of Biological Sciences, University of Leeds

Copyright

© Lichtinger et al; licensee BioMed Central Ltd. 2013

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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