RESUMEN
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.
Asunto(s)
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
PURPOSE OF REVIEW: The hematopoietic compartment is tasked with the establishment and maintenance of the entire blood program in steady-state and in response to stress. Key to this process are hematopoietic stem cells (HSCs), which possess the unique ability to self-renew and differentiate to replenish blood cells throughout an organism's lifetime. Though tightly regulated, the hematopoietic system is vulnerable to both intrinsic and extrinsic factors that influence hematopoietic stem and progenitor cell (HSPC) fate. Here, we review recent advances in our understanding of hematopoietic regulation under stress conditions such as inflammation, aging, mitochondrial defects, and damage to DNA or endoplasmic reticulum. RECENT FINDINGS: Recent studies have illustrated the vast mechanisms involved in regulating stress-induced hematopoiesis, including cytokine-mediated lineage bias, gene signature changes in aged HSCs associated with chronic inflammation, the impact of clonal hematopoiesis and stress tolerance, characterization of the HSPC response to endoplasmic reticulum stress and of several epigenetic regulators that influence HSPC response to cell cycle stress. SUMMARY: Several key recent findings have deepened our understanding of stress hematopoiesis. These studies will advance our abilities to reduce the impact of stress in disease and aging through clinical interventions to treat stress-related outcomes.
Asunto(s)
Envejecimiento/metabolismo , Daño del ADN , Estrés del Retículo Endoplásmico , Epigénesis Genética , Hematopoyesis , Células Madre Hematopoyéticas/metabolismo , Mitocondrias/metabolismo , Envejecimiento/patología , Células Madre Hematopoyéticas/patología , Humanos , Inflamación/metabolismo , Inflamación/patología , Mitocondrias/patologíaRESUMEN
Polycomb repressive complexes (PRCs) play key roles in developmental epigenetic regulation. Yet the mechanisms that target PRCs to specific loci in mammalian cells remain incompletely understood. In this study we show that Bmi1, a core component of Polycomb Repressive Complex 1 (PRC1), binds directly to the Runx1/CBFß transcription factor complex. Genome-wide studies in megakaryocytic cells demonstrate significant chromatin occupancy overlap between the PRC1 core component Ring1b and Runx1/CBFß and functional regulation of a considerable fraction of commonly bound genes. Bmi1/Ring1b and Runx1/CBFß deficiencies generate partial phenocopies of one another in vivo. We also show that Ring1b occupies key Runx1 binding sites in primary murine thymocytes and that this occurs via PRC2-independent mechanisms. Genetic depletion of Runx1 results in reduced Ring1b binding at these sites in vivo. These findings provide evidence for site-specific PRC1 chromatin recruitment by core binding transcription factors in mammalian cells.
Asunto(s)
Cromatina/metabolismo , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Subunidad beta del Factor de Unión al Sitio Principal/metabolismo , Proteínas Represoras/metabolismo , Animales , Línea Celular , Cromatografía de Afinidad , Análisis por Conglomerados , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Subunidad beta del Factor de Unión al Sitio Principal/genética , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Técnicas de Silenciamiento del Gen , Células Madre Hematopoyéticas/fisiología , Megacariocitos/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Complejo Represivo Polycomb 1 , Proteínas del Grupo Polycomb , Unión Proteica , Multimerización de Proteína , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Represoras/genética , Proteínas Represoras/aislamiento & purificación , Linfocitos T/metabolismo , Timocitos/metabolismo , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismo , Pez Cebra/embriología , Pez Cebra/genéticaRESUMEN
Human exposure to Vibrio vulnificus, a gram-negative, halophilic environmental pathogen, is increasing. Despite this, the mechanisms of its pathogenicity and virulence remain largely unknown. Each year, hundreds of infections related to V. vulnificus occur, leading to hospitalization in 92% of cases and a mortality rate of 35%. The infection is severe, typically contracted through the consumption of contaminated food or exposure of an open wound to contaminated water. This can result in necrotizing fasciitis and the need for amputation of the infected tissue. Although several genes (rtxA1, vvpE, and vvhA) have been implicated in the pathogenicity of this organism, a defined mechanism has not been discovered. In this study, we examine environmentally isolated V. vulnificus strains using a zebrafish model (Danio rerio) to investigate their virulence capabilities. We found significant variation in virulence between individual strains. The commonly used marker gene of disease-causing strains, vcgC, did not accurately predict the more virulent strains. Notably, the least virulent strain in the study, V. vulnificus Sept WR1-BW6, which tested positive for vcgC, vvhA, and rtxA1, did not cause severe disease in the fish and was the only strain that did not result in any mortality. Our study demonstrates that virulence varies greatly among different environmental strains and cannot be accurately predicted based solely on genotype.
Asunto(s)
Vibriosis , Vibrio vulnificus , Pez Cebra , Vibrio vulnificus/patogenicidad , Vibrio vulnificus/genética , Vibrio vulnificus/aislamiento & purificación , Animales , Pez Cebra/microbiología , Virulencia/genética , Vibriosis/microbiología , Factores de Virulencia/genética , Modelos Animales de Enfermedad , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Humanos , Microbiología AmbientalRESUMEN
The complex processes necessary for embryogenesis require a gene regulatory network that is complex and systematic. Gene expression regulates development and organogenesis, but this process is altered and fine-tuned by epigenetic regulators that facilitate changes in the chromatin landscape. Epigenetic regulation of embryogenesis adjusts the chromatin structure by modifying both DNA through methylation and nucleosomes through posttranslational modifications of histone tails. The zebrafish is a well-characterized model organism that is a quintessential tool for studying developmental biology. With external fertilization, low cost and high fecundity, the zebrafish are an efficient tool for studying early developmental stages. Genetic manipulation can be performed in vivo resulting in quick identification of gene function. Large-scale genome analyses including RNA sequencing, chromatin immunoprecipitation and chromatin structure all are feasible in the zebrafish. In this review, we highlight the key events in zebrafish development where epigenetic regulation plays a critical role from the early stem cell stages through differentiation and organogenesis.
RESUMEN
Ikaros is a hematopoietic cell-specific zinc finger DNA binding protein that plays an important role in lymphocyte development. Genetic disruption of Ikaros results in T-cell transformation. Ikaros null mice develop leukemia with 100% penetrance. It has been hypothesized that Ikaros controls gene expression through its association with chromatin remodeling complexes. The development of leukemia in Ikaros null mice suggests that Ikaros has the characteristics of a tumor suppressor gene. In this report, we show that the introduction of Ikaros into an established mouse Ikaros null T leukemia cell line leads to growth arrest at the G0/G1 stage of the cell cycle. This arrest is associated with up-regulation of the cell cycle-dependent kinase inhibitor p27kip1, the induction of expression of T-cell differentiation markers, and a global and specific increase in histone H3 acetylation status. These studies provide strong evidence that Ikaros possesses the properties of a bona fide tumor suppressor gene for the T-cell lineage and offer insight into the mechanism of Ikaros's tumor suppressive activity.
Asunto(s)
Proteínas de Unión al ADN/fisiología , Genes Supresores de Tumor/fisiología , Leucemia de Células T/metabolismo , Linfocitos T/citología , Factores de Transcripción/fisiología , Acetilación , Animales , Ciclo Celular/genética , Ciclo Celular/fisiología , Proteínas de Ciclo Celular/genética , Diferenciación Celular , Línea Celular Tumoral , Proliferación Celular , Inhibidor p27 de las Quinasas Dependientes de la Ciclina , Proteínas de Unión al ADN/genética , Vectores Genéticos/genética , Histonas/metabolismo , Factor de Transcripción Ikaros , Leucemia de Células T/genética , Leucemia de Células T/patología , Ratones , Retroviridae/genética , Linfocitos T/fisiología , Timo/citología , Factores de Transcripción/genética , Transducción Genética , Proteínas Supresoras de Tumor/genética , Regulación hacia ArribaRESUMEN
The initiation of cellular programs is orchestrated by key transcription factors and chromatin regulators that activate or inhibit target gene expression. To generate a compendium of chromatin factors that establish the epigenetic code during developmental haematopoiesis, a large-scale reverse genetic screen was conducted targeting orthologues of 425 human chromatin factors in zebrafish. A set of chromatin regulators was identified that target different stages of primitive and definitive blood formation, including factors not previously implicated in haematopoiesis. We identified 15 factors that regulate development of primitive erythroid progenitors and 29 factors that regulate development of definitive haematopoietic stem and progenitor cells. These chromatin factors are associated with SWI/SNF and ISWI chromatin remodelling, SET1 methyltransferase, CBP-p300-HBO1-NuA4 acetyltransferase, HDAC-NuRD deacetylase, and Polycomb repressive complexes. Our work provides a comprehensive view of how specific chromatin factors and their associated complexes play a major role in the establishment of haematopoietic cells in vivo.
Asunto(s)
Hematopoyesis/genética , Proteínas de Pez Cebra/genética , Pez Cebra/genética , Animales , Cromatina/genética , Cromatina/metabolismo , Ensamble y Desensamble de Cromatina , Epigénesis Genética , Células Eritroides/metabolismo , Técnicas de Silenciamiento del Gen , Redes Reguladoras de Genes , Células Madre Hematopoyéticas/fisiología , Humanos , Morfolinos/genética , Mapas de Interacción de Proteínas , Subunidades de Proteína/genética , Subunidades de Proteína/metabolismo , Genética Inversa , Proteínas de Pez Cebra/metabolismoRESUMEN
Transcriptome analysis of adult hematopoietic stem cells (HSCs) and their progeny has revealed mechanisms of blood differentiation and leukemogenesis, but a similar analysis of HSC development is lacking. Here, we acquired the transcriptomes of developing HSCs purified from >2,500 murine embryos and adult mice. We found that embryonic hematopoietic elements clustered into three distinct transcriptional states characteristic of the definitive yolk sac, HSCs undergoing specification, and definitive HSCs. We applied a network-biology-based analysis to reconstruct the gene regulatory networks of sequential stages of HSC development and functionally validated candidate transcriptional regulators of HSC ontogeny by morpholino-mediated knockdown in zebrafish embryos. Moreover, we found that HSCs from in vitro differentiated embryonic stem cells closely resemble definitive HSCs, yet lack a Notch-signaling signature, likely accounting for their defective lymphopoiesis. Our analysis and web resource will enhance efforts to identify regulators of HSC ontogeny and facilitate the engineering of hematopoietic specification.
Asunto(s)
Células Madre Hematopoyéticas/citología , Animales , Diferenciación Celular , Células Madre Embrionarias/citología , Células Madre Embrionarias/metabolismo , Perfilación de la Expresión Génica , Células Madre Hematopoyéticas/metabolismo , Ratones , Saco Vitelino/citología , Pez CebraRESUMEN
Charged multivesicular body protein 1A (CHMP1A; also known as chromatin-modifying protein 1A) is a member of the ESCRT-III (endosomal sorting complex required for transport-III) complex but is also suggested to localize to the nuclear matrix and regulate chromatin structure. Here, we show that loss-of-function mutations in human CHMP1A cause reduced cerebellar size (pontocerebellar hypoplasia) and reduced cerebral cortical size (microcephaly). CHMP1A-mutant cells show impaired proliferation, with increased expression of INK4A, a negative regulator of stem cell proliferation. Chromatin immunoprecipitation suggests loss of the normal INK4A repression by BMI in these cells. Morpholino-based knockdown of zebrafish chmp1a resulted in brain defects resembling those seen after bmi1a and bmi1b knockdown, which were partially rescued by INK4A ortholog knockdown, further supporting links between CHMP1A and BMI1-mediated regulation of INK4A. Our results suggest that CHMP1A serves as a critical link between cytoplasmic signals and BMI1-mediated chromatin modifications that regulate proliferation of central nervous system progenitor cells.
Asunto(s)
Corteza Cerebelosa , Inhibidor p16 de la Quinasa Dependiente de Ciclina , Complejos de Clasificación Endosomal Requeridos para el Transporte , Proteína Quinasa 7 Activada por Mitógenos , Neuronas , Animales , Proliferación Celular , Corteza Cerebelosa/crecimiento & desarrollo , Corteza Cerebelosa/metabolismo , Inhibidor p16 de la Quinasa Dependiente de Ciclina/genética , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , Complejos de Clasificación Endosomal Requeridos para el Transporte/genética , Complejos de Clasificación Endosomal Requeridos para el Transporte/metabolismo , Regulación del Desarrollo de la Expresión Génica , Ligamiento Genético , Células HEK293 , Humanos , Ratones , Microcefalia/genética , Microcefalia/metabolismo , Proteína Quinasa 7 Activada por Mitógenos/genética , Proteína Quinasa 7 Activada por Mitógenos/metabolismo , Mutación , Células 3T3 NIH , Células-Madre Neurales/metabolismo , Células-Madre Neurales/patología , Neuronas/metabolismo , Neuronas/patología , Polimorfismo de Nucleótido Simple , Proteínas de Transporte Vesicular , Pez Cebra/genética , Pez Cebra/crecimiento & desarrollo , Pez Cebra/metabolismoRESUMEN
Ikaros and Notch1, two regulators of gene transcription, are critically important at many stages of T cell development. Deregulation of Ikaros and Notch activities cooperate to promote T cell leukemogenesis, providing evidence that they function in converging pathways in developing T cells. In this report, a mechanism for Ikaros:Notch cooperativity is described, revealing a non-redundant role for Ikaros in regulating expression of the Notch target gene Hes1 in a leukemia T cell line. We provide evidence that Ikaros directly represses Hes1 in concert with the transcriptional repressor, RBP-Jkappa, allowing for cross-talk between Notch and Ikaros that impacts regulation of CD4 expression. Taken together, these data describe a potential mechanism for Ikaros' function during T cell development and define Ikaros as an obligate repressor of Hes1.