ABSTRACT: Analysis of embryonic sten cell-derived embryoid bodies following endoglin knock out. Loss of endoglin leads to profound reduction of key hematopoietic regulators including SCL, LMO2, Gata2, and TGF-β signaling molecule ALK-1. Results provide insight into molecular mechanisms underlying hemangioblast and primitive hematopoietic development.
Project description:Analysis of embryonic sten cell-derived embryoid bodies following endoglin knock out. Loss of endoglin leads to profound reduction of key hematopoietic regulators including SCL, LMO2, Gata2, and TGF-? signaling molecule ALK-1. Results provide insight into molecular mechanisms underlying hemangioblast and primitive hematopoietic development. Total RNA obtained from differentiated day 3 EBs of endoglin knock out ES cells were compared to wild type E14 control ES cells.
Project description:Much remains unknown about the signals that induce early mesoderm to initiate hematopoietic differentiation. Here we show that endoglin (Eng), a receptor for the TGFβ superfamily, identifies all cells with hematopoietic fate in the early embryo. These arise in an Eng+Flk1+ mesodermal precursor population at E7.5, a cell fraction also endowed with endothelial potential. In Eng knockout embryos, hematopoietic colony activity and numbers of CD71+Ter119+ erythroid progenitors were severely reduced. This coincided with severely reduced expression of embryonic globin and key BMP target genes including the hematopoietic regulators Scl, Gata1, Gata2 and Msx-1. To interrogate molecular pathways active in the earliest hematopoietic progenitors, we applied transcriptional profiling to sorted cells from E7.5 embryos. Eng+Flk-1+ progenitors co-expressed TGFβ and BMP receptors and target genes. Furthermore, Eng+Flk-1+ cells presented high levels of phospho-SMAD1/5, indicating active TGFβ and/or BMP signaling. Remarkably, under hematopoietic serum-free culture conditions, hematopoietic outgrowth of endoglin-expressing cells was dependent on TGFβ superfamily ligands: BMP4, BMP2, or TGF-β1. These data demonstrate that the E+F+ fraction at E7.5 represents mesodermal cells competent to respond to TGFb1, BMP4, or BMP2, shaping their hematopoietic development, and that endoglin is a critical regulator in this process by modulating TGF/BMP signaling.
Project description:Much remains unknown about the signals that induce early mesoderm to initiate hematopoietic differentiation. Here we show that endoglin (Eng), a receptor for the TGFβ superfamily, identifies all cells with hematopoietic fate in the early embryo. These arise in an Eng+Flk1+ mesodermal precursor population at E7.5, a cell fraction also endowed with endothelial potential. In Eng knockout embryos, hematopoietic colony activity and numbers of CD71+Ter119+ erythroid progenitors were severely reduced. This coincided with severely reduced expression of embryonic globin and key BMP target genes including the hematopoietic regulators Scl, Gata1, Gata2 and Msx-1. To interrogate molecular pathways active in the earliest hematopoietic progenitors, we applied transcriptional profiling to sorted cells from E7.5 embryos. Eng+Flk-1+ progenitors co-expressed TGFβ and BMP receptors and target genes. Furthermore, Eng+Flk-1+ cells presented high levels of phospho-SMAD1/5, indicating active TGFβ and/or BMP signaling. Remarkably, under hematopoietic serum-free culture conditions, hematopoietic outgrowth of endoglin-expressing cells was dependent on TGFβ superfamily ligands: BMP4, BMP2, or TGF-β1. These data demonstrate that the E+F+ fraction at E7.5 represents mesodermal cells competent to respond to TGFb1, BMP4, or BMP2, shaping their hematopoietic development, and that endoglin is a critical regulator in this process by modulating TGF/BMP signaling. E7.5 pooled embryos (25 litters; 300 embryos approximately) were dissected and 3,000 cells were sorted in triplicate for Eng-Flk1-, Eng-Flk1+, Eng+Flk1+, and Eng+Flk1- fractions. Microarray results were analyzed with GeneSpring GX software.
Project description:Molecular mechanisms that regulate the generation of hematopoietic and endothelial cells from mesoderm are poorly understood. To define the underlying mechanisms, we compared gene expression profiles between embryonic stem (ES) cell-derived hemangioblasts (Blast-Colony-Forming Cells, BL-CFCs) and their differentiated progeny, Blast cells. Bioinformatic analysis indicated that BL-CFCs resembled other stem cell populations. A role for Gata2, one of the BL-CFC-enriched transcripts, was further characterized by utilizing the in vitro model of ES cell differentiation. Our studies revealed that Gata2 was a direct target of BMP4 and that enforced GATA2 expression upregulated Bmp4, Flk1 and Scl. Conditional GATA2 induction resulted in a temporal-sensitive increase in hemangioblast generation, precocious commitment to erythroid fate, and increased endothelial cell generation. GATA2 additionally conferred a proliferative signal to primitive erythroid progenitors. Collectively, we provide compelling evidence that GATA2 plays specific, contextual roles in the generation of Flk-1+ mesoderm, the Flk-1+Scl+ hemangioblast, primitive erythroid and endothelial cells. Keywords: Comparison of induced differetiated state to original cell line.
Project description:Molecular mechanisms that regulate the generation of hematopoietic and endothelial cells from mesoderm are poorly understood. To define the underlying mechanisms, we compared gene expression profiles between embryonic stem (ES) cell-derived hemangioblasts (Blast-Colony-Forming Cells, BL-CFCs) and their differentiated progeny, Blast cells. Bioinformatic analysis indicated that BL-CFCs resembled other stem cell populations. A role for Gata2, one of the BL-CFC-enriched transcripts, was further characterized by utilizing the in vitro model of ES cell differentiation. Our studies revealed that Gata2 was a direct target of BMP4 and that enforced GATA2 expression upregulated Bmp4, Flk1 and Scl. Conditional GATA2 induction resulted in a temporal-sensitive increase in hemangioblast generation, precocious commitment to erythroid fate, and increased endothelial cell generation. GATA2 additionally conferred a proliferative signal to primitive erythroid progenitors. Collectively, we provide compelling evidence that GATA2 plays specific, contextual roles in the generation of Flk-1+ mesoderm, the Flk-1+Scl+ hemangioblast, primitive erythroid and endothelial cells. Keywords: Comparison of induced differetiated state to original cell line. Generation of Hemangioblast and Blast Colony cell populations: Scl+/hCD4 ES cells (Chung et al., Development, 2002) were maintained on a layer of mitotically inactivated STO cells in DMEM media in the presence of LIF. Two days before differentiation, the cells were transferred to gelatinized tissue culture flasks and the media was changed to IMDM-based. ES cells were differentiated in liquid-differentiation media in the presence of FCS for 2.75 days. D2.75 EBs were recovered, dissociated in Trypsin/EDTA and stained with antibodies against Flk-1 and human CD4. Cells were then flow sorted on the basis of Flk-1 and Scl expression and the hemangioblast population was considered to be Flk-1+Scl+. D2.75 EB cells were replated as described (Chung et al., 2002) and individual Blast colonies were picked and pooled, and RNA was generated with TRIzol according to the manufacturers protocol. RNA (20 ug) was given to the Washington University Array core were it was reverse transcribed and cRNA synthesized. Replicated of the two populations (hCD4, Blast) were made. Pairwaise comparisons were performed to identify enriched genes.
Project description:Successful derivation of a specific cell lineage from pluripotent stem cells will tremendously facilitate the clinical usage of pluripotent stem derived somatic cells. Herein, we demonstrate that ER71/Etv2, GATA2 and Scl form a core network in hemangioblast development and that transient co-expression of these three factors robustly induced hemangioblasts from ES cells. Such induced hemangioblasts potently generated hematopoietic and endothelial cells in culture as well as in vivo, warranting the evaluation of these cells in the future for repairing and/or regenerating hematopoietic and/or angiogenic defects. We have established a doxycycline inducible ES cell, iEGS, in which ER71/Etv2, GATA2 three transcription factors can be transiently co-expressed by doxycycline induction. We further analyzed the downstream target genes and signaling pathways at 6, 12 and 24hrs after ER71/Etv2, GATA2 induction. These data were obtained from three independent experiments.
Project description:Successful derivation of a specific cell lineage from pluripotent stem cells will tremendously facilitate the clinical usage of pluripotent stem derived somatic cells. Herein, we demonstrate that ER71/Etv2, GATA2 and Scl form a core network in hemangioblast development and that transient co-expression of these three factors robustly induced hemangioblasts from ES cells. Such induced hemangioblasts potently generated hematopoietic and endothelial cells in culture as well as in vivo, warranting the evaluation of these cells in the future for repairing and/or regenerating hematopoietic and/or angiogenic defects.
Project description:Combinatorial actions of relatively few transcription factors control hematopoietic differentiation. To investigate this process in erythro-megakaryopoiesis, we correlated the genome-wide chromatin occupancy signatures of four master hematopoietic transcription factors (GATA1, GATA2, SCL/TAL1 and FLI1) and three diagnostic histone modification marks with the gene expression changes that occur during development of primary megakaryocytes (MEG) and erythroblasts (ERY) from murine fetal liver hematopoietic stem/progenitor cells. We identified a robust, genome-wide mechanism of MEG-specific lineage priming by a previously described stem/progenitor cell-expressed transcription factor heptad (GATA2, LYL1, SCL/TAL1, FLI1, ERG, RUNX1, LMO2) binding to MEG-specific cis-regulatory modules in multipotential hematopoietic progenitors. This is followed by genome-wide GATA factor switching that mediates further induction of MEG-specific genes following lineage commitment. Interaction between GATA and ETS factors appears to be a key determinant of these processes. In contrast, ERY-specific lineage priming occurs is biased toward GATA2-independent mechanisms. In addition to its role in MEG lineage priming, GATA2 plays an extensive role in late megakaryopoiesis as a transcriptional repressor at loci defined by a specific DNA signature. Our findings reveal important new insights into how ERY and MEG lineages arise from a common bipotential precursor via overlapping and divergent functions of shared hematopoietic transcription factors. Gene expression changes during the development of primary megakaryocytes (MEG) and erythroblasts (ERY) from murine fetal liver hematopoietic stem/progenitor cells
Project description:Combinatorial transcription factor (TF) interactions control cellular phenotypes and therefore underpin stem cell formation, maintenance and differentiation. Here we report the genome-wide binding patterns and combinatorial interactions for 10 key regulators of blood stem/progenitor cells (Scl/Tal1, Lyl1, Lmo2, Gata2, Runx1, Meis1, Pu.1, Erg, Fli-1, Gfi1b) thus providing the most comprehensive TF dataset for any adult stem/progenitor cell type to date. Genome-wide computational analysis of complex binding patterns followed by functional validation revealed the following: First, a previously unrecognized combinatorial interaction between a heptad of TFs (Scl, Lyl1, Lmo2, Gata2, Runx1, Erg, Fli-1). Second, we implicate direct protein-protein interactions between four key regulators (Runx1, Gata2, Scl, Erg) in stabilising complex binding to DNA. Third, Runx1+/-::Gata2+/- compound heterozygous mice are not viable with severe haematopoietic defects at midgestation. Taken together, this study demonstrates the power of genome-wide analysis in generating novel functional insights into the transcriptional control of stem and progenitor cells.