Etv2-mediated hemangiogenic fate commitment of mesoderm
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ABSTRACT: A comprehensive understanding of a lineage map and molecular mechanisms underlying lineage specification is fundamental to development. To this end, ETS transcription factor Etv2 functions as the master regulator of hematopoietic and endothelial cell formation. As such, Etv2 regulated hemangiogenesis provides an excellent model for assessing cell lineage specification. Herein, we generated several reporter embryonic stem (ES) cell lines to map developmental route pertaining to hemangiogenesis. We performed transcriptome analysis and high throughput CRISPR screening to further delineate molecular mechanisms regulating hemangiogenic lineage specification. We show a distinct lineage map of hemangiogenesis, in which hemangiogenic fate is specified not simply by the onset of Etv2 expression, but in a threshold-dependent manner. Importantly, VEGF-FLK1 signaling is necessary for efficiently achieving ETV2-threshold. Moreover, we find forkhead transcription factor Foxh1 to be required for FLK1 mesoderm formation. These studies provide a roadmap in hematopoietic and vascular cell generation and applications in regenerative medicine.
Project description:We discover that ER71/ETV2 initiates hemangiogenic program by activating blood and endothelial cell lineage specifying genes while enhancing FLK1 expression and expanding hemangioblast population. Furthermore, ER71/ETV2 establishes an ETS hierarchy by directly activating Ets genes in hematopoietic and endothelial cell lineage development. As such, ER71/ETV2-initiated blood and endothelial cell program is maintained by ER71/ETV2 downstream ETS factors through an ETS switching mechanism. ChIP-seq analysis of ER71 in differentiated embryonic stem cells
Project description:We discover that ER71/ETV2 initiates hemangiogenic program by activating blood and endothelial cell lineage specifying genes while enhancing FLK1 expression and expanding hemangioblast population. Furthermore, ER71/ETV2 establishes an ETS hierarchy by directly activating Ets genes in hematopoietic and endothelial cell lineage development. As such, ER71/ETV2-initiated blood and endothelial cell program is maintained by ER71/ETV2 downstream ETS factors through an ETS switching mechanism.
Project description:ETV2/ER71, an ETS transcription factor, is critical for hematopoiesis and vascular development. However, knowledge on the molecular mechanisms behind ETV2-mediated gene transcription is limited. Here, we show that ETV2 together with KDM4A, an H3K9 demethylase, regulates hematopoietic and endothelial genes. Etv2-/- mouse embryonic stem cells (mESCs), which fail to generate hematopoietic and endothelial cells, showed enhanced levels of H3K9me3 on hematopoietic and endothelial genes. ETV2 interacts with KDM4A and the ETV2-mediated transcriptional activation of hematopoietic and endothelial genes is dependent on KDM4A histone demethylase activity. ETV2 and KDM4A co-occupy the transcription regulatory regions of genes whose expression is directly regulated by ETV2. Mice lacking Kdm4a and Etv2 in endothelial cells (Cdh5Cre;Kdm4af/f;Etv2f/f) displayed a more severe defect in perfusion recovery and neovascularization compared with Cdh5Cre;Kdm4af/f, Cdh5Cre;Etv2f/f mice and controls. Collectively, we demonstrated that ETV2 interacts with KDM4A and that this interaction is critical for FLK1+ cell generation, differentiation into the downstream lineages, and vascular regeneration.
Project description:Mechanisms of cell fate specification are central to developmental biology and regenerative medicine. ETV2 is a master regulator for the endothelial cell lineage specification. Here, we study mechanisms by which ETV2 overexpression in human iPSC-derived mesodermal progenitors efficiently specifies ECs.
Project description:During embryogenesis, the endothelial and the hematopoietic lineages first appear during gastrulation in the blood island of the yolk sac. We have previously reported that an Ets variant gene 2 (Etv2/ER71) mutant embryo lacks hematopoietic and endothelial lineages, however, the precise roles of Etv2 in yolk sac development remains unclear. We carried out a transcriptome analysis using an ES cell line that can inducibly express Etv2. Cells were induced for 12 hours at day 3 of differentiation. An ES cell line (dervied from mouse of background strain 129P2/Ola) with a doxycycline inducible expression casette of Etv2 (ER71 A2Lox.cre) was differentiated in hanging drops. At 3 days of differentiation, cells were treated with doxycycline for 12 hours, and subsequently Flk1(+) cells were sorted. Experiment was done in triplicate and untreated cells were used for control.
Project description:To identify genes critical for vascular development, we generated mice where ETV2 is inactivated in FLK1+ cells by a loxP-Cre recombination approach. Results provide a detailed insight into the function of ETV2 in emrbyonic vasculare formation. Total RNA obtained from E9.5 yolk sacs from Flk1Cre;ETV2 CKO and control mice.
Project description:To identify genes critical for vascular development, we generated mice where ETV2 is inactivated in FLK1+ cells by a loxP-Cre recombination approach. Results provide a detailed insight into the function of ETV2 in emrbyonic vasculare formation.
Project description:The lineage-determining transcription factor ETV2 is necessary and sufficient for hematoendothelial fate commitment. We investigated how ETV2-driven gene regulatory networks promote hematoendothelial fate commitment. We resolved the sequential determination steps of hematoendothelial versus cardiac differentiation from mouse embryonic stem cells. Etv2 was strongly induced and bound to the enhancers of hematoendothelial genes in a common cardiomyocyte-hematoendothelial mesoderm progenitor. However, only Etv2 itself and Tal1, not other ETV2-bound genes, were induced. Despite ETV2 genomic binding and Etv2 and Tal1 expression, cardiomyogenic fate potential was maintained. A second wave of ETV2-bound target genes was up-regulated during the transition from the common cardiomyocyte-hematoendothelial progenitor to the committed hematoendothelial population. A third wave of ETV-bound genes were subsequently expressed in the committed hematoendothelial population for sub-lineage differentiation. The shift from ETV2 binding to productive transcription, not ETV2 binding to target gene enhancers, drove hematoendothelial fate commitment. This work identifies mechanistic phases of ETV2-dependent gene expression that distinguish hematoendothelial specification, commitment, and differentiation.
Project description:It has now been well established that hematopoietic stem and progenitor cells originate from a specialised subset of endothelium termed hemogenic endothelium (HE) via an endothelial-to-hematopoietic transition. However, the molecular mechanisms determining which endothelial progenitors possess or not this hemogenic potential is currently unknown. In this study, we investigated the changes in hemogenic potential in endothelial progenitors at the early stages of embryonic development. We use a microarray approach to profile the genes regulated between E7.5 and E8.5 embryonic day in the ETV2+FLK1+CD41- compartment. Cells were sorted based on ETV2::GFP+/FLK1+/CD41- immunophenotype from ETV2::GFP embryos at E7.5 and E8.5 developmental stage in triplicates
Project description:Etv2 transgene was expressed from ROSA26 locus by removing floxed STOP cassette by Vav Cre transgene. KSL or Mac1+/Gr1+ cells were sorted from control or Vav-Etv2 bone marrow and compared for gene expression in duplicate. This study will reveal the effect of Etv2 transgene in adult hematopoietic cells. The effect of Etv2 overexpression in relevant mouse tissue will be important to understand its effect in comparison with in ES cells. Genes aberrantly regulated by Etv2 overexpression will help to understand the caveat when using Etv2 to induce endothelial and hematopoietic cells in vitro. Sample ID #1;KSL;Control #2;KSL;Control #3;KSL;Tg #4;KSL;Tg #5;Gr;Control #6;Gr;Control #7;Gr;Tg #8;Gr;Tg