Chd1 is essential in the endothelial lineage for the emergence of definitive hematopoietic stem/progenitor cells
ABSTRACT: 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:Targeted disruption of the Runx1/ AML1 gene in mice has demonstrated that it is required for the emergence of definitive hematopoietic cells, but that it is not essential for the formation of primitive erythrocytes. These findings led to the conclusion that Runx1 is a stage-specific transcription factor acting only during definitive hematopoiesis. However, the zebrafish and Xenopus homologues of Runx1 have been shown to play roles in primitive hematopoiesis, suggesting that mouse Runx1 might also be involved in the development of primitive lineages. In order to identify differentially expressed genes in runx1-/- primitive erythroid, we carried out microarray analysis. Keywords: genetic modification Overall design: Total RNA from E10.5 wild type and Runx1–/– yolk sacs was extracted, and gene expression patterns were compared.
Project description:Targeted disruption of the Runx1/ AML1 gene in mice has demonstrated that it is required for the emergence of definitive hematopoietic cells, but that it is not essential for the formation of primitive erythrocytes. These findings led to the conclusion that Runx1 is a stage-specific transcription factor acting only during definitive hematopoiesis. However, the zebrafish and Xenopus homologues of Runx1 have been shown to play roles in primitive hematopoiesis, suggesting that mouse Runx1 might also be involved in the development of primitive lineages. In order to identify differentially expressed genes in runx1-/- primitive erythroid, we carried out microarray analysis. Experiment Overall Design: Total RNA from E10.5 wild type and Runx1–/– yolk sacs was extracted, and gene expression patterns were compared.
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: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:The pluripotent mammalian epiblast undergoes unusually fast cell proliferation. This rapid growth is expected to generate a high transcriptional demand, but the underlying mechanisms remain unknown. We report that the chromatin remodeler Chd1, which binds the activating histone mark H3K4me3 and is associated with transcription, is required for development of the mouse epiblast. Chd1-/- embryos exhibit proliferation defects and increased apoptosis, are smaller than controls by E5.5, and fail to grow, become patterned or gastrulate. We show that Chd1-/- ES cells have a self-renewal defect and a genome-wide reduction in transcriptional output that is associated with losses in RNA Pol II elongation at growth-promoting genes, including ribosomal proteins. We also report that Chd1 directly regulates ribosomal RNA transcription and that both Chd1-/- epiblast cells in vivo and ES cells in vitro express significantly lower levels of ribosomal RNA. Single cell analyses reveal abnormal nucleolar morphology in mutants in vivo and in vitro. These data indicate that Chd1 promotes a globally elevated transcriptional output required to sustain the distinct rapid growth of the mouse epiblast. Overall design: Cell-number normalized RNA-seq from wild-type and Chd1-/- mouse embryonic stem cells.
Project description:BACKGROUND: Deletion of the chromatin remodeler CHD1 is a common genomic alteration found in human prostate cancers (PCas). CHD1 loss represents a distinct PCa subtype characterized by SPOP mutation and higher genomic instability [1-3]. However, the role of CHD1 in PCa development in vivo and its clinical utility remain unclear. DESIGN: To study the role of CHD1 in PCa development and its loss in clinical management, we generated a genetically engineered mouse model with prostate-specific deletion of murine Chd1 as well as isogenic CHD1 WT and homozygous deleted human benign and PCa lines. We also developed patient-derived organoid cultures and screened patients with metastatic PCa for CHD1 loss. RESULTS: We demonstrate that CHD1 loss sensitizes cells to DNA damage and causes a synthetic lethal response to DNA damaging therapy in vivo, ex vivo and in a patient with metastatic PCa. Mechanistically, CHD1 loss leads to decreased error-free homologous recombination (HR) repair, which is compensated by increased error-prone non-homologous end joining (NHEJ) repair for DNA double-strand break (DSB) repair. CONCLUSIONS: Our study provides the first in vivo and in patient evidence supporting the role of CHD1 in DSB repair and in response to DNA damaging therapy. We uncover mechanistic insights that CHD1 modulates the choice between HR and NHEJ and suggest that CHD1 loss may contribute to genomic instability seen in this subset of PCa patients. Overall design: In total, 11 murine samples and 9 human samples were analyzed. For each genotype, there are 3 to 6 replicates.
Project description:We generated S.cerevisiae strains in which endogenous copies of candidate nucleosome spacing factors were replaced with the K.lactis copies. With this candidate approach, we found that K.lactis Chd1 directed longer nucleosome repeat length in S.cerevisiae. Generating chimeric proteins revealed that the strongest contribution to this differential spacing lies in the undercharacterised N-terminus of Chd1. Overall design: nucleosome mapping for S.cerevisiae hho1, ioc3isw1, and chd1 deletion mutants and complemented with the K.lactis copies
Project description:Identification of the regulators that lead to arterial specification with definitive hematopoietic potential should help to design strategies to recapitulate HSC development from human pluripotent stem cells (hPSCs). Here, using ETS1 conditional H1 hESC line, we found that ETS1 induction at the mesodermal stage of differentiation dramatically enhances the arterial specification in hPSC cultures and formation of DLL4+CXCR4+/- arterial HE with lymphoid potential and the capacity to produce red blood cells with high expression of BCL11a and b-globin. ETS1 effect was mediated through upregulation of NOTCH signaling. Together, these findings demonstrated that promotion of arterial specification in cultures could aid in generation of definitive hematopoiesis from hPSCs. Overall design: We engineered H1 human embryonic stem cells (hESC) carrying doxycycline (DOX)-inducible ETS1-P2A-EGFP transgene (iETS1-hESCs) and differentiated them to endothelial and hematopoietic cells in chemically defined conditions
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