Submitted July 3, 2007
Accepted December 5, 2007
Runx genes are direct targets of Scl/Tal1 in the yolk sac and fetal liver
Josette-Renee Landry, Sarah Kinston, Kathy Knezevic, Marella F.T.R. de Bruijn, Nicola Wilson, Wade T. Nottingham, Michael Peitz, Frank Edenhofer, John E Pimanda, Katrin Ottersbach, and Berthold Gottgens*
Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
The Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
Stem Cell Engineering Group, Institute of Reconstructive Neurobiology, LIFE & BRAIN Center, University of Bonn and Hertie Foundation, Bonn, Germany
* Corresponding author; email: bg200{at}cam.ac.uk.
Transcription factors such as Scl/Tal1, Lmo2 and Runx1 are essential for the development of hematopoietic stem cells (HSCs). However, the precise mechanisms by which these factors interact to form transcriptional networks, as well as the identity of the genes downstream of these regulatory cascades remain largely unknown. To this end, we generated an Scl-/- yolk sac cell line to identify candidate Scl target genes by global expression profiling following re-introduction of a TAT-Scl fusion protein. Bioinformatics analysis resulted in the identification of nine candidate Scl target transcription factor genes, including Runx1 and Runx3. Chromatin immunoprecipitation confirmed that both Runx genes are direct targets of Scl in the fetal liver and that Runx1 is also occupied by Scl in the yolk sac. Furthermore, binding of an Scl-Lmo2-Gata2 complex was demonstrated to occur on the regions flanking the conserved E-boxes of the Runx1 loci and was shown to transactivate the Runx1 element. Together our data provides a key component of the transcriptional network of early haematopoiesis by identifying downstream targets of Scl that can explain key aspects of the early Scl-/- phenotype.
