RESUMEN
Improving effector activity of antigen-specific T cells is a major goal in cancer immunotherapy. Despite the identification of several effector T cell (TEFF)-driving transcription factors (TFs), the transcriptional coordination of TEFF biology remains poorly understood. We developed an in vivo T cell CRISPR screening platform and identified a key mechanism restraining TEFF biology through the ETS family TF, Fli1. Genetic deletion of Fli1 enhanced TEFF responses without compromising memory or exhaustion precursors. Fli1 restrained TEFF lineage differentiation by binding to cis-regulatory elements of effector-associated genes. Loss of Fli1 increased chromatin accessibility at ETS:RUNX motifs, allowing more efficient Runx3-driven TEFF biology. CD8+ T cells lacking Fli1 provided substantially better protection against multiple infections and tumors. These data indicate that Fli1 safeguards the developing CD8+ T cell transcriptional landscape from excessive ETS:RUNX-driven TEFF cell differentiation. Moreover, genetic deletion of Fli1 improves TEFF differentiation and protective immunity in infections and cancer.
Asunto(s)
Linfocitos T CD8-positivos/citología , Proteína Proto-Oncogénica c-fli-1/metabolismo , Animales , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/metabolismo , Sistemas CRISPR-Cas , Diferenciación Celular , Enfermedad Crónica , Subunidad alfa 3 del Factor de Unión al Sitio Principal/metabolismo , Epigénesis Genética , Redes Reguladoras de Genes , Infecciones/inmunología , Ratones , Neoplasias/inmunologíaRESUMEN
The transcription factor RUNX1 is mutated in familial platelet disorder with associated myeloid malignancy (FPDMM) and in sporadic myelodysplastic syndrome and leukemia. RUNX1 was shown to regulate inflammation in multiple cell types. Here we show that RUNX1 is required in granulocyte-monocyte progenitors (GMPs) to epigenetically repress two inflammatory signaling pathways in neutrophils: Toll-like receptor 4 (TLR4) and type I interferon (IFN) signaling. RUNX1 loss in GMPs augments neutrophils' inflammatory response to the TLR4 ligand lipopolysaccharide through increased expression of the TLR4 coreceptor CD14. RUNX1 binds Cd14 and other genes encoding proteins in the TLR4 and type I IFN signaling pathways whose chromatin accessibility increases when RUNX1 is deleted. Transcription factor footprints for the effectors of type I IFN signaling-the signal transducer and activator of transcription (STAT1::STAT2) and interferon regulatory factors (IRFs)-were enriched in chromatin that gained accessibility in both GMPs and neutrophils when RUNX1 was lost. STAT1::STAT2 and IRF motifs were also enriched in the chromatin of retrotransposons that were derepressed in RUNX1-deficient GMPs and neutrophils. We conclude that a major direct effect of RUNX1 loss in GMPs is the derepression of type I IFN and TLR4 signaling, resulting in a state of fixed maladaptive innate immunity.
Asunto(s)
Neutrófilos , Receptor Toll-Like 4 , Receptor Toll-Like 4/metabolismo , Monocitos/metabolismo , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Citocinas/metabolismo , Cromatina/metabolismo , Factor de Transcripción STAT1/metabolismoRESUMEN
Hematopoietic stem and progenitor cells (HSPCs) can reconstitute and sustain the entire blood system. We generated a highly specific transgenic reporter of HSPCs in zebrafish. This allowed us to perform high-resolution live imaging on endogenous HSPCs not currently possible in mammalian bone marrow. Using this system, we have uncovered distinct interactions between single HSPCs and their niche. When an HSPC arrives in the perivascular niche, a group of endothelial cells remodel to form a surrounding pocket. This structure appears conserved in mouse fetal liver. Correlative light and electron microscopy revealed that endothelial cells surround a single HSPC attached to a single mesenchymal stromal cell. Live imaging showed that mesenchymal stromal cells anchor HSPCs and orient their divisions. A chemical genetic screen found that the compound lycorine promotes HSPC-niche interactions during development and ultimately expands the stem cell pool into adulthood. Our studies provide evidence for dynamic niche interactions upon stem cell colonization. PAPERFLICK:
Asunto(s)
Endotelio/fisiología , Células Madre Hematopoyéticas/citología , Pez Cebra/embriología , Animales , Animales Modificados Genéticamente , División Celular , Subunidades alfa del Factor de Unión al Sitio Principal/genética , Subunidades alfa del Factor de Unión al Sitio Principal/metabolismo , Embrión no Mamífero/irrigación sanguínea , Embrión no Mamífero/fisiología , Endotelio/citología , Células Madre Hematopoyéticas/fisiología , Mesodermo/citología , Mesodermo/metabolismo , Ratones , Ratones Endogámicos C57BL , Nicho de Células Madre , Células del Estroma/citología , Células del Estroma/metabolismo , Pez Cebra/fisiologíaRESUMEN
Meningioma-1 (MN1) overexpression in AML is associated with poor prognosis, and forced expression of MN1 induces leukemia in mice. We sought to determine how MN1 causes AML. We found that overexpression of MN1 can be induced by translocations that result in hijacking of a downstream enhancer. Structure predictions revealed that the entire MN1 coding frame is disordered. We identified the myeloid progenitor-specific BAF complex as the key interaction partner of MN1. MN1 over-stabilizes BAF on enhancer chromatin, a function directly linked to the presence of a long polyQ-stretch within MN1. BAF over-stabilization at binding sites of transcription factors regulating a hematopoietic stem/progenitor program prevents the developmentally appropriate decommissioning of these enhancers and results in impaired myeloid differentiation and leukemia. Beyond AML, our data detail how the overexpression of a polyQ protein, in the absence of any coding sequence mutation, can be sufficient to cause malignant transformation.
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Carcinogénesis/genética , ADN Helicasas/genética , Proteínas Intrínsecamente Desordenadas/genética , Leucemia Mieloide Aguda/genética , Proteínas Nucleares/genética , Transactivadores/genética , Factores de Transcripción/genética , Proteínas Supresoras de Tumor/genética , Animales , Secuencia de Bases , Carcinogénesis/metabolismo , Carcinogénesis/patología , Línea Celular Tumoral , Cromatina/genética , Cromatina/metabolismo , Cromatina/patología , ADN Helicasas/metabolismo , Elementos de Facilitación Genéticos , Femenino , Regulación Leucémica de la Expresión Génica , Redes Reguladoras de Genes , Humanos , Proteínas Intrínsecamente Desordenadas/metabolismo , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/mortalidad , Leucemia Mieloide Aguda/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Proteínas Nucleares/metabolismo , Péptidos/genética , Péptidos/metabolismo , Mapeo de Interacción de Proteínas , Estabilidad Proteica , Transporte de Proteínas , Transducción de Señal , Análisis de Supervivencia , Transactivadores/metabolismo , Factores de Transcripción/metabolismo , Proteínas Supresoras de Tumor/metabolismoRESUMEN
Hematopoietic stem and progenitor cells (HSPCs) are generated de novo in the embryo from hemogenic endothelial cells (HECs) via an endothelial-to-hematopoietic transition (EHT) that requires the transcription factor RUNX1. Ectopic expression of RUNX1 alone can efficiently promote EHT and HSPC formation from embryonic endothelial cells (ECs), but less efficiently from fetal or adult ECs. Efficiency correlated with baseline accessibility of TGFß-related genes associated with endothelial-to-mesenchymal transition (EndoMT) and participation of AP-1 and SMAD2/3 to initiate further chromatin remodeling along with RUNX1 at these sites. Activation of TGFß signaling improved the efficiency with which RUNX1 specified fetal ECs as HECs. Thus, the ability of RUNX1 to promote EHT depends on its ability to recruit the TGFß signaling effectors AP-1 and SMAD2/3, which in turn is determined by the changing chromatin landscape in embryonic versus fetal ECs. This work provides insight into regulation of EndoMT and EHT that will guide reprogramming efforts for clinical applications.
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Hemangioblastos , Diferenciación Celular/genética , Cromatina/metabolismo , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Feto , Hemangioblastos/metabolismo , Hematopoyesis/genética , Células Madre Hematopoyéticas , Humanos , Factor de Crecimiento Transformador beta/metabolismo , Factor de Crecimiento Transformador beta1RESUMEN
Inflammatory signals support the birth of hematopoietic stem cells in zebrafish embryos, but their cellular source in mammals is not known. In this issue, Mariani et al. (2019) report that macrophages are a primary source of pro-inflammatory signals that promote blood cell formation in mammalian embryos.
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Trasplante de Células Madre Hematopoyéticas , Suelo , Animales , Aorta , Hematopoyesis , Células Madre Hematopoyéticas , Macrófagos , Pez CebraRESUMEN
Hematopoietic stem cell (HSC) ontogeny is accompanied by dynamic changes in gene regulatory networks. We performed RNA-seq and histone mark ChIP-seq to define the transcriptomes and epigenomes of cells representing key developmental stages of HSC ontogeny in mice. The five populations analyzed were embryonic day 10.5 (E10.5) endothelium and hemogenic endothelium from the major arteries, an enriched population of prehematopoietic stem cells (pre-HSCs), fetal liver HSCs, and adult bone marrow HSCs. Using epigenetic signatures, we identified enhancers for each developmental stage. Only 12% of enhancers are primed, and 78% are active, suggesting the vast majority of enhancers are established de novo without prior priming in earlier stages. We constructed developmental stage-specific transcriptional regulatory networks by linking enhancers and predicted bound transcription factors to their target promoters using a novel computational algorithm, target inference via physical connection (TIPC). TIPC predicted known transcriptional regulators for the endothelial-to-hematopoietic transition, validating our overall approach, and identified putative novel transcription factors, including the broadly expressed transcription factors SP3 and MAZ. Finally, we validated a role for SP3 and MAZ in the formation of hemogenic endothelium. Our data and computational analyses provide a useful resource for uncovering regulators of HSC formation.
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Regulación del Desarrollo de la Expresión Génica/genética , Redes Reguladoras de Genes/genética , Hematopoyesis/genética , Células Madre Hematopoyéticas/citología , Algoritmos , Animales , Proteínas de Unión al ADN/metabolismo , Elementos de Facilitación Genéticos/genética , Epigénesis Genética/genética , Edición Génica , Ratones , Factor de Transcripción Sp3/metabolismo , Factores de Transcripción/metabolismo , TranscriptomaRESUMEN
Hemogenic endothelial (HE) cells in the dorsal aorta undergo an endothelial-to-hematopoietic transition (EHT) to form multipotent progenitors, lympho-myeloid biased progenitors (LMPs), pre-hematopoietic stem cells (pre-HSCs) and adult-repopulating HSCs. These briefly accumulate in intra-arterial hematopoietic clusters (IAHCs) before being released into the circulation. It is generally assumed that the number of IAHC cells correlates with the number of HSCs. Here, we show that changes in the number of IAHC cells, LMPs and HSCs can be uncoupled. Mutations impairing MyD88-dependent toll-like receptor (TLR) signaling decreased the number of IAHC cells and LMPs, but increased the number of HSCs in the aorta-gonad-mesonephros region of mouse embryos. TLR4-deficient embryos generated normal numbers of HE cells, but IAHC cell proliferation decreased. Loss of MyD88-dependent TLR signaling in innate immune myeloid cells had no effect on IAHC cell numbers. Instead, TLR4 deletion in endothelial cells (ECs) recapitulated the phenotype observed with germline deletion, demonstrating that MyD88-dependent TLR signaling in ECs and/or in IAHCs regulates the numbers of LMPs and HSCs.
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Embrión de Mamíferos/metabolismo , Células Madre Hematopoyéticas/metabolismo , Factor 88 de Diferenciación Mieloide/metabolismo , Transducción de Señal , Animales , Diferenciación Celular , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Embrión de Mamíferos/citología , Células Endoteliales/citología , Células Endoteliales/metabolismo , Hemangioblastos/citología , Hemangioblastos/metabolismo , Células Madre Hematopoyéticas/citología , Inmunidad Innata , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Células Mieloides/citología , Células Mieloides/metabolismo , Factor 88 de Diferenciación Mieloide/deficiencia , Factor 88 de Diferenciación Mieloide/genética , Receptor Toll-Like 4/deficiencia , Receptor Toll-Like 4/genética , Receptor Toll-Like 4/metabolismo , Receptores Toll-Like/metabolismoRESUMEN
The hematopoietic stem cells (HSCs) that produce blood for the lifetime of an animal arise from RUNX1+ hemogenic endothelial cells (HECs) in the embryonic vasculature through a process of endothelial-to-hematopoietic transition (EHT). Studies have identified inflammatory mediators and fluid shear forces as critical environmental stimuli for EHT, raising the question of how such diverse inputs are integrated to drive HEC specification. Endothelial cell MEKK3-KLF2/4 signaling can be activated by both fluid shear forces and inflammatory mediators, and it plays roles in cardiovascular development and disease that have been linked to both stimuli. Here we demonstrate that MEKK3 and KLF2/4 are required in endothelial cells for the specification of RUNX1+ HECs in both the yolk sac and dorsal aorta of the mouse embryo and for their transition to intraaortic hematopoietic cluster (IAHC) cells. The inflammatory mediators lipopolysaccharide and interferon-γ increase RUNX1+ HECs in an MEKK3-dependent manner. Maternal administration of catecholamines that stimulate embryo cardiac function and accelerate yolk sac vascular remodeling increases EHT by wild-type but not MEKK3-deficient endothelium. These findings identify MEKK-KLF2/4 signaling as an essential pathway for EHT and provide a molecular basis for the integration of diverse environmental inputs, such as inflammatory mediators and hemodynamic forces, during definitive hematopoiesis.
Asunto(s)
Subunidad alfa 2 del Factor de Unión al Sitio Principal , Hemangioblastos , Hematopoyesis , Animales , Diferenciación Celular , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Endotelio/metabolismo , Hemangioblastos/citología , Hemangioblastos/metabolismo , Hemodinámica , Mediadores de Inflamación/metabolismo , Factores de Transcripción de Tipo Kruppel/genética , Factores de Transcripción de Tipo Kruppel/metabolismo , MAP Quinasa Quinasa Quinasa 3/metabolismo , RatonesRESUMEN
Developmental pathways that orchestrate the fleeting transition of endothelial cells into haematopoietic stem cells remain undefined. Here we demonstrate a tractable approach for fully reprogramming adult mouse endothelial cells to haematopoietic stem cells (rEC-HSCs) through transient expression of the transcription-factor-encoding genes Fosb, Gfi1, Runx1, and Spi1 (collectively denoted hereafter as FGRS) and vascular-niche-derived angiocrine factors. The induction phase (days 0-8) of conversion is initiated by expression of FGRS in mature endothelial cells, which results in endogenous Runx1 expression. During the specification phase (days 8-20), RUNX1+ FGRS-transduced endothelial cells commit to a haematopoietic fate, yielding rEC-HSCs that no longer require FGRS expression. The vascular niche drives a robust self-renewal and expansion phase of rEC-HSCs (days 20-28). rEC-HSCs have a transcriptome and long-term self-renewal capacity similar to those of adult haematopoietic stem cells, and can be used for clonal engraftment and serial primary and secondary multi-lineage reconstitution, including antigen-dependent adaptive immune function. Inhibition of TGFß and CXCR7 or activation of BMP and CXCR4 signalling enhanced generation of rEC-HSCs. Pluripotency-independent conversion of endothelial cells into autologous authentic engraftable haematopoietic stem cells could aid treatment of haematological disorders.
Asunto(s)
Diferenciación Celular , Reprogramación Celular , Endotelio/citología , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/inmunología , Linfocitos T/citología , Linfocitos T/inmunología , Inmunidad Adaptativa , Envejecimiento/genética , Animales , Línea Celular , Linaje de la Célula , Autorrenovación de las Células , Células Clonales/citología , Células Clonales/trasplante , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Células Endoteliales/citología , Células Endoteliales/metabolismo , Hematopoyesis , Trasplante de Células Madre Hematopoyéticas , Células Madre Hematopoyéticas/metabolismo , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-fos/genética , Proteínas Proto-Oncogénicas c-fos/metabolismo , Transactivadores/genética , Transactivadores/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , TranscriptomaRESUMEN
Hematopoietic stem and progenitor cell (HSPC) formation and lineage differentiation involve gene expression programs orchestrated by transcription factors and epigenetic regulators. Genetic disruption of the chromatin remodeler chromodomain-helicase-DNA-binding protein 7 (CHD7) expanded phenotypic HSPCs, erythroid, and myeloid lineages in zebrafish and mouse embryos. CHD7 acts to suppress hematopoietic differentiation. Binding motifs for RUNX and other hematopoietic transcription factors are enriched at sites occupied by CHD7, and decreased RUNX1 occupancy correlated with loss of CHD7 localization. CHD7 physically interacts with RUNX1 and suppresses RUNX1-induced expansion of HSPCs during development through modulation of RUNX1 activity. Consequently, the RUNX1:CHD7 axis provides proper timing and function of HSPCs as they emerge during hematopoietic development or mature in adults, representing a distinct and evolutionarily conserved control mechanism to ensure accurate hematopoietic lineage differentiation.
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Subunidad alfa 2 del Factor de Unión al Sitio Principal , Proteínas de Unión al ADN , Hematopoyesis , Animales , Diferenciación Celular , Línea Celular , Subunidad alfa 2 del Factor de Unión al Sitio Principal/química , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Femenino , Células Madre Hematopoyéticas , Humanos , Masculino , Ratones , Bazo/citología , Pez CebraRESUMEN
Hematopoietic stem and progenitor cells (HSPCs) in the bone marrow are derived from a small population of hemogenic endothelial (HE) cells located in the major arteries of the mammalian embryo. HE cells undergo an endothelial to hematopoietic cell transition, giving rise to HSPCs that accumulate in intra-arterial clusters (IAC) before colonizing the fetal liver. To examine the cell and molecular transitions between endothelial (E), HE, and IAC cells, and the heterogeneity of HSPCs within IACs, we profiled â¼40 000 cells from the caudal arteries (dorsal aorta, umbilical, vitelline) of 9.5 days post coitus (dpc) to 11.5 dpc mouse embryos by single-cell RNA sequencing and single-cell assay for transposase-accessible chromatin sequencing. We identified a continuous developmental trajectory from E to HE to IAC cells, with identifiable intermediate stages. The intermediate stage most proximal to HE, which we term pre-HE, is characterized by increased accessibility of chromatin enriched for SOX, FOX, GATA, and SMAD motifs. A developmental bottleneck separates pre-HE from HE, with RUNX1 dosage regulating the efficiency of the pre-HE to HE transition. A distal candidate Runx1 enhancer exhibits high chromatin accessibility specifically in pre-HE cells at the bottleneck, but loses accessibility thereafter. Distinct developmental trajectories within IAC cells result in 2 populations of CD45+ HSPCs; an initial wave of lymphomyeloid-biased progenitors, followed by precursors of hematopoietic stem cells (pre-HSCs). This multiomics single-cell atlas significantly expands our understanding of pre-HSC ontogeny.
Asunto(s)
Diferenciación Celular , Endotelio/embriología , Hemangioblastos/fisiología , Hematopoyesis/fisiología , Células Madre Hematopoyéticas/fisiología , Animales , Diferenciación Celular/genética , Subunidad alfa 2 del Factor de Unión al Sitio Principal/fisiología , Embrión de Mamíferos , Endotelio/citología , Endotelio/metabolismo , Femenino , Dosificación de Gen/fisiología , Regulación del Desarrollo de la Expresión Génica , Hemangioblastos/citología , Hematopoyesis/genética , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Embarazo , RNA-Seq/métodosRESUMEN
Identifying signaling pathways that regulate hematopoietic stem and progenitor cell (HSPC) formation in the embryo will guide efforts to produce and expand HSPCs ex vivo. Here we show that sterile tonic inflammatory signaling regulates embryonic HSPC formation. Expression profiling of progenitors with lymphoid potential and hematopoietic stem cells (HSCs) from aorta/gonad/mesonephros (AGM) regions of midgestation mouse embryos revealed a robust innate immune/inflammatory signature. Mouse embryos lacking interferon γ (IFN-γ) or IFN-α signaling and zebrafish morphants lacking IFN-γ and IFN-Ï activity had significantly fewer AGM HSPCs. Conversely, knockdown of IFN regulatory factor 2 (IRF2), a negative regulator of IFN signaling, increased expression of IFN target genes and HSPC production in zebrafish. Chromatin immunoprecipitation (ChIP) combined with sequencing (ChIP-seq) and expression analyses demonstrated that IRF2-occupied genes identified in human fetal liver CD34(+) HSPCs are actively transcribed in human and mouse HSPCs. Furthermore, we demonstrate that the primitive myeloid population contributes to the local inflammatory response to impact the scale of HSPC production in the AGM region. Thus, sterile inflammatory signaling is an evolutionarily conserved pathway regulating the production of HSPCs during embryonic development.
Asunto(s)
Regulación del Desarrollo de la Expresión Génica , Células Madre Hematopoyéticas/citología , Inmunidad Innata/genética , Inmunidad Innata/inmunología , Transducción de Señal , Animales , Antígenos Ly/genética , Antígenos Ly/metabolismo , Proliferación Celular/genética , Células Cultivadas , Citocinas/inmunología , Embrión de Mamíferos , Embrión no Mamífero , Perfilación de la Expresión Génica , Técnicas de Silenciamiento del Gen , Humanos , Inflamación/genética , Inflamación/inmunología , Interferones/genética , Interferones/metabolismo , Ratones , Pez Cebra/embriologíaRESUMEN
Hematopoietic cells differentiate during embryogenesis from a population of endothelial cells called hemogenic endothelium (HE) in a process called the endothelial-to-hematopoietic transition (EHT). The transcription factor Runx1 is required for EHT, but for how long and which endothelial cells are competent to respond to Runx1 are not known. Here, we show that the ability of Runx1 to induce EHT in non-hemogenic endothelial cells depends on the anatomical location of the cell and the developmental age of the conceptus. Ectopic expression of Runx1 in non-hemogenic endothelial cells between embryonic day (E) 7.5 and E8.5 promoted the formation of erythro-myeloid progenitors (EMPs) specifically in the yolk sac, the dorsal aorta and the heart. The increase in EMPs was accompanied by a higher frequency of HE cells able to differentiate into EMPs in vitro Expression of Runx1 just 1 day later (E8.5-E9.5) failed to induce the ectopic formation of EMPs. Therefore, endothelial cells, located in specific sites in the conceptus, have a short developmental window of competency during which they can respond to Runx1 and differentiate into blood cells.
Asunto(s)
Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Células Endoteliales/citología , Células Endoteliales/metabolismo , Hematopoyesis/fisiología , Animales , Diferenciación Celular , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Femenino , Regulación del Desarrollo de la Expresión Génica , Edad Gestacional , Hematopoyesis/genética , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/metabolismo , Masculino , Ratones , Ratones Transgénicos , Especificidad de Órganos , Embarazo , Saco Vitelino/citología , Saco Vitelino/embriología , Saco Vitelino/metabolismoRESUMEN
The hematopoietic system is one of the first complex tissues to develop in the mammalian conceptus. Of particular interest in the field of developmental hematopoiesis is the origin of adult bone marrow hematopoietic stem cells. Tracing their origin is complicated because blood is a mobile tissue and because hematopoietic cells emerge from many embryonic sites. The origin of the adult mammalian blood system remains a topic of lively discussion and intense research. Interest is also focused on developmental signals that induce the adult hematopoietic stem cell program, as these may prove useful for generating and expanding these clinically important cell populations ex vivo. This review presents a historical overview of and the most recent data on the developmental origins of hematopoiesis.
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Linaje de la Célula , Embrión de Mamíferos/citología , Células Madre Hematopoyéticas/fisiología , Animales , Linaje de la Célula/genética , Eritrocitos/citología , Células Madre Hematopoyéticas/citología , Humanos , RatonesRESUMEN
The Runx1 transcription factor is post-translationally modified by seryl/threonyl phosphorylation, acetylation, and methylation that control its interactions with transcription factor partners and epigenetic coregulators. In this issue of Genes & Development, Huang and colleagues (pp. 1587-1601) describe how the regulation of Runx1 tyrosyl phosphorylation by Src family kinases and the Shp2 phosphatase toggle Runx1's interactions between different coregulatory molecules.
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Linfocitos T CD8-positivos/metabolismo , Diferenciación Celular/fisiología , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Megacariocitos/metabolismo , Proteína Tirosina Fosfatasa no Receptora Tipo 11/metabolismo , Transducción de Señal/fisiología , Familia-src Quinasas/metabolismo , Animales , HumanosRESUMEN
Inversion of chromosome 16 is a consistent finding in patients with acute myeloid leukemia subtype M4 with eosinophilia, which generates a CBFB-MYH11 fusion gene. Previous studies showed that the interaction between CBFß-smooth muscle myosin heavy chain (SMMHC; encoded by CBFB-MYH11) and RUNX1 plays a critical role in the pathogenesis of this leukemia. Recently, it was shown that chromodomain helicase DNA-binding protein-7 (CHD7) interacts with RUNX1 and suppresses RUNX1-induced expansion of hematopoietic stem and progenitor cells. These results suggest that CHD7 is also critical for CBFB-MYH11-induced leukemogenesis. To test this hypothesis, we generated Chd7f/fMx1-CreCbfb+/56M mice, which expressed the Cbfb-MYH11 fusion gene and deactivated Chd7 in hematopoietic cells upon inducing Cre with polyinosinic-polycytidylic acid. The Lin-Sca1-c-Kit+ (LK) population was significantly lower in Chd7f/fMx1-CreCbfb+/56M mice than in Mx1-CreCbfb+/56M mice. In addition, there were fewer 5-bromo-2'-deoxyuridine-positive cells in the LK population in Chd7f/fMx1-CreCbfb+/56M mice, and genes associated with cell cycle, cell growth, and proliferation were differentially expressed between Chd7f/fMx1-CreCbfb+/56M and Mx1-CreCbfb+/56M leukemic cells. In vitro studies showed that CHD7 interacted with CBFß-SMMHC through RUNX1 and that CHD7 enhanced transcriptional activity of RUNX1 and CBFß-SMMHC on Csf1r, a RUNX1 target gene. Moreover, RNA sequencing of c-Kit+ cells showed that CHD7 functions mostly through altering the expression of RUNX1 target genes. Most importantly, Chd7 deficiency delayed Cbfb-MYH11-induced leukemia in both primary and transplanted mice. These data indicate that Chd7 is important for Cbfb-MYH11-induced leukemogenesis by facilitating RUNX1 regulation of transcription and cellular proliferation.
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Proteínas de Unión al ADN/genética , Regulación Leucémica de la Expresión Génica , Leucemia/genética , Proteínas de Fusión Oncogénica/genética , Animales , Ciclo Celular , Proliferación Celular , Eliminación de Gen , Humanos , Leucemia/patología , Ratones , Ratones NoqueadosRESUMEN
The de novo generation of hematopoietic cells occurs during midgestation when a population of endothelial cells called hemogenic endothelium transitions into hematopoietic progenitors and stem cells. In mammalian embryos, the newly formed hematopoietic cells form clusters in the lumens of the major arteries in the embryo proper and in the vascular plexus of the yolk sac. Small clusters of hematopoietic cells that are independent of the vasculature (referred to here as extravascular islands) were shown to form in the mesentery during vascular remodeling of the vitelline artery. Using three-dimensional imaging of whole mouse embryos we demonstrate that extravascular budding of hematopoietic clusters is a more widespread phenomenon that occurs from the vitelline and the umbilical arteries both proximal to the embryo proper and distal in the extraembryonic yolk sac and placenta. Furthermore, we show that there are several mechanisms by which hematopoietic clusters leave the arteries, including vascular remodeling and extrusion. Lastly, we provide static images suggesting that extravascular islands contribute to the formation of new blood vessels. Thus, extravascular islands may represent a novel mechanism of vasculogenesis whereby established vessels contribute endothelial and hematopoietic cells to developing vascular beds.
Asunto(s)
Células Madre Hematopoyéticas/citología , Mesenterio/embriología , Neovascularización Fisiológica/fisiología , Animales , Antígenos Ly/análisis , Subunidad alfa 2 del Factor de Unión al Sitio Principal/análisis , Sistema Linfático/embriología , Proteínas de la Membrana/análisis , Mesenterio/citología , Ratones , Microscopía Confocal , Especificidad de Órganos , Arterias Umbilicales/embriología , Remodelación Vascular , Saco Vitelino/irrigación sanguíneaRESUMEN
The de novo generation of hematopoietic stem and progenitor cells (HSPC) occurs solely during embryogenesis from a population of epithelial cells called hemogenic endothelium (HE). During midgestation HE cells in multiple intra- and extraembryonic vascular beds leave the vessel wall as they transition into HSPCs in a process termed the endothelial to hematopoietic transition (EHT). Runx1 expression in HE cells orchestrates the transcriptional switch necessary for the transdifferentiation of endothelial cells into functional HSPCs. Runx1 is widely considered the master regulator of developmental hematopoiesis because it plays an essential function during specification of the hematopoietic lineage during embryogenesis. Here we review the role of Runx1 in embryonic HSPC formation, with a particular focus on its role in hemogenic endothelium.