Project description:Lineage specification during development involves reprogramming of chromatin states, but little is known about how this is regulated in vivo. We previously showed that the chromatin remodeler Chd1 regulates transcriptional output and self-renewal of mouse embryonic stem cells, and is essential for epiblast development. These results raise the question of whether Chd1 regulates the development of other progenitor populations. Here we report that endothelial-specific deletion of Chd1 using Tie2-Cre leads to embryonic lethality by E15.5. Development of the vasculature and of primitive hematopoiesis appears to occur normally in the mutants. However, mutant embryos show signs of anemia as early as E11.5, are depleted of definitive hematopoietic stem /progenitor cells, and display a complete failure of fetal liver erythropoiesis. While mutants at E10.5 appear morphologically normal and can develop hemogenic clusters in the dorsal aorta, the E10.5 mutant endothelium fails to activate a transcriptional program associated with hematopoiesis. This transcriptional program may serve as a resource for the identification of novel markers or regulators of definitive hematopoiesis. Finally, hematopoietic-specific Chd1 deletion using Vav-Cre yields no apparent defects during development or adulthood. These results suggest that Chd1 regulates chromatin-remodeling events critical for a specific developmental window during the transition of endothelial cells to definitive blood progenitors. Analysis of CD31+ tdTomato+ cells sorted from E10.5 whole embryos with an endothelial-specific deletion of Chd1, using 4 biological replicates of 2 genotypes (CreHet controls vs mutants).
Project description:Lineage specification during development involves reprogramming of chromatin states, but little is known about how this is regulated in vivo. We previously showed that the chromatin remodeler Chd1 regulates transcriptional output and self-renewal of mouse embryonic stem cells, and is essential for epiblast development. These results raise the question of whether Chd1 regulates the development of other progenitor populations. Here we report that endothelial-specific deletion of Chd1 using Tie2-Cre leads to embryonic lethality by E15.5. Development of the vasculature and of primitive hematopoiesis appears to occur normally in the mutants. However, mutant embryos show signs of anemia as early as E11.5, are depleted of definitive hematopoietic stem /progenitor cells, and display a complete failure of fetal liver erythropoiesis. While mutants at E10.5 appear morphologically normal and can develop hemogenic clusters in the dorsal aorta, the E10.5 mutant endothelium fails to activate a transcriptional program associated with hematopoiesis. This transcriptional program may serve as a resource for the identification of novel markers or regulators of definitive hematopoiesis. Finally, hematopoietic-specific Chd1 deletion using Vav-Cre yields no apparent defects during development or adulthood. These results suggest that Chd1 regulates chromatin-remodeling events critical for a specific developmental window during the transition of endothelial cells to definitive blood progenitors.
Project description:Pluripotent stem cells (PSC) represent an alternative source of hematopoietic stem cells (HSCs). Clinical translation is impeded by limited engraftment of human (h)PSC-multipotent progenitor cells (MPP). This barrier suggests that additional cues are required for definitive hematopoiesis. We hypothesized that vascular niche producing Notch ligands Jagged-1 (JAG1) and Delta-like ligand-4 (DLL4) would drive definitive hematopoiesis. To test our hypothesis, hes2 human embryonic stem cells (hESC) 2 and Macaca nemestrina (Mn) iPSC line-7 were differentiated with cytokines ± endothelial cells (EC), which express JAG1 and DLL4. EC co-culture supported emergence of 8-fold more CD34+CD45+ cells compared to co-culture with cytokines ± ECs with JAG1 or DLL4 knockdown. EC-induced cells exhibit Notch activation and express HSC-specific targets of Notch signaling RUNX1 and GATA2. EC-induced PSC-MPP engraft at a higher level in NSG mice compared to cytokine-induced cells (10% >5 months), and selection increased engraftment (30%). Long-term engraftment and the myeloid-to-lymphoid ratio achieved with vascular niche induction is similar to levels achieved for cord blood MPP and up to 20-fold higher than hPSC-MPP engraftment. Our findings identify a previously underappreciated role for endothelial Notch ligands in PSC definitive hematopoiesis and production of long-term engrafting CD34+ cells and suggest they are critical for HSC emergence. Transcriptome sequencing of Macaca nemestrina (Mn) iPSCs
Project description:We sorted endothelial (EC), hematopoietic (HC) and hematopoietic stem/progenitor (HSPC) cell populations from AGM of E11.5 C57Bl6 embryos, established and compared their transcriptome to highlight specific regulators of hematopoietic emergence.
Project description:Definitive hematopoiesis emerges during embryogenesis via an endothelial-to-hematopoietic transition. We attempted to induce this process in mouse fibroblasts by screening a panel of factors for hemogenic activity. We identified a combination of four transcription factors, Gata2, Gfi1b, cFos, and Etv6 that efficiently induces endothelial-like precursor cells with the subsequent appearance of hematopoietic cells. The precursor cells express a human CD34 reporter, Sca1 and Prominin1 within a global endothelial transcription program. Emergent hematopoietic cells possess nascent/specifying hematopoietic stem cell gene expression profiles and cell surface phenotypes. After transgene silencing and reaggregation culture, the specified cells generate hematopoietic colonies in vitro. Thus, we have shown that a simple combination of transcription factors is sufficient to induce a complex, dynamic and multi-step developmental program in vitro. These findings provide insights into the specification of definitive hemogenesis and a platform for future development of patient-specific stem/progenitor cells as well as more differentiated blood products. mRNA-seq profiling on populations generated after transduction with Gata2, Gfi1b, cFos and Etv6 at day 20 and day 35.
Project description:GATA2 is essential for the endothelial-to-hematopoietic transition (EHT) and generation of hematopoietic stem cells (HSCs). It is poorly understood how GATA2 controls the development of human pluripotent stem cell (hPSC)-derived HSC-like cells. Here, using human embryonic stem cells (hESCs) in which GATA2 overexpression was induced by doxycycline (Dox), we elucidated the dual functions of GATA2 in definitive hematopoiesis before and after the emergence of CD34+CD45+CD90+CD38- HSC-like cells. Specifically, GATA2 promoted expansion of hemogenic precursors via the EHT and then helped to maintain HSC-like cells in a quiescent state by arresting the cell cycle at G0/G1 phase. RNA-sequencing showed that hPSC-derived-HSC-like cells were very similar to human fetal liver-derived HSCs. Our findings will help to elucidate the mechanism that controls the early stages of human definitive hematopoiesis and may help to generate hPSC-derived HSCs.
Project description:Pluripotent stem cells (PSC) represent an alternative source of hematopoietic stem cells (HSCs). Clinical translation is impeded by limited engraftment of human (h)PSC-multipotent progenitor cells (MPP). This barrier suggests that additional cues are required for definitive hematopoiesis. We hypothesized that vascular niche producing Notch ligands Jagged-1 (JAG1) and Delta-like ligand-4 (DLL4) would drive definitive hematopoiesis. To test our hypothesis, hes2 human embryonic stem cells (hESC) 2 and Macaca nemestrina (Mn) iPSC line-7 were differentiated with cytokines ± endothelial cells (EC), which express JAG1 and DLL4. EC co-culture supported emergence of 8-fold more CD34+CD45+ cells compared to co-culture with cytokines ± ECs with JAG1 or DLL4 knockdown. EC-induced cells exhibit Notch activation and express HSC-specific targets of Notch signaling RUNX1 and GATA2. EC-induced PSC-MPP engraft at a higher level in NSG mice compared to cytokine-induced cells (10% >5 months), and selection increased engraftment (30%). Long-term engraftment and the myeloid-to-lymphoid ratio achieved with vascular niche induction is similar to levels achieved for cord blood MPP and up to 20-fold higher than hPSC-MPP engraftment. Our findings identify a previously underappreciated role for endothelial Notch ligands in PSC definitive hematopoiesis and production of long-term engrafting CD34+ cells and suggest they are critical for HSC emergence.
Project description:Development of the hematopoietic system is dynamically controlled by the interplay of transcriptional and epigenetic networks to determine cellular identity. Those networks are critical for homeostasis and frequently dysregulated in leukemias. We identified histone demethylase Kdm2b as a critical regulator of definitive hematopoiesis and lineage specification of hematopoietic stem and progenitor cells (HSPCs). RNA sequencing in murine HSPCs and genome-wide chromatin immunoprecipitation studies in human leukemias revealed that Kdm2b regulates differentiation, lineage choice, cytokine signaling, and quiescence. Comparison of gene expression in wild-type and knockout HSPCs
Project description:Development of the hematopoietic system is dynamically controlled by the interplay of transcriptional and epigenetic networks to determine cellular identity. Those networks are critical for homeostasis and frequently dysregulated in leukemias. We identified histone demethylase Kdm2b as a critical regulator of definitive hematopoiesis and lineage specification of hematopoietic stem and progenitor cells (HSPCs). RNA sequencing in murine HSPCs and genome-wide chromatin immunoprecipitation studies in human leukemias revealed that Kdm2b regulates differentiation, lineage choice, cytokine signaling, and quiescence. Identify the binding of KDM2B in seven human leukemia cell lines