RESUMO
Erythropoietin (EPO) signaling is critical to many processes essential to terminal erythropoiesis. Despite the centrality of iron metabolism to erythropoiesis, the mechanisms by which EPO regulates iron status are not well-understood. To this end, here we profiled gene expression in EPO-treated 32D pro-B cells and developing fetal liver erythroid cells to identify additional iron regulatory genes. We determined that FAM210B, a mitochondrial inner-membrane protein, is essential for hemoglobinization, proliferation, and enucleation during terminal erythroid maturation. Fam210b deficiency led to defects in mitochondrial iron uptake, heme synthesis, and iron-sulfur cluster formation. These defects were corrected with a lipid-soluble, small-molecule iron transporter, hinokitiol, in Fam210b-deficient murine erythroid cells and zebrafish morphants. Genetic complementation experiments revealed that FAM210B is not a mitochondrial iron transporter but is required for adequate mitochondrial iron import to sustain heme synthesis and iron-sulfur cluster formation during erythroid differentiation. FAM210B was also required for maximal ferrochelatase activity in differentiating erythroid cells. We propose that FAM210B functions as an adaptor protein that facilitates the formation of an oligomeric mitochondrial iron transport complex, required for the increase in iron acquisition for heme synthesis during terminal erythropoiesis. Collectively, our results reveal a critical mechanism by which EPO signaling regulates terminal erythropoiesis and iron metabolism.
Assuntos
Células Eritroides/metabolismo , Eritropoetina/metabolismo , Ferroquelatase/metabolismo , Heme/biossíntese , Ferro/metabolismo , Proteínas de Membrana/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Animais , Células Eritroides/citologia , Eritropoese , Células HEK293 , Humanos , Proteínas de Membrana/química , Camundongos , Membranas Mitocondriais/metabolismo , Proteínas Mitocondriais/química , Transporte ProteicoRESUMO
Megakaryocyte (MK) development in the bone marrow progresses spatially from the endosteal niche, which promotes MK progenitor proliferation, to the sinusoidal vascular niche, the site of terminal maturation and thrombopoiesis. The chemokine stromal cell-derived factor-1 (SDF-1), signaling through CXCR4, is implicated in the maturational chemotaxis of MKs toward sinusoidal vessels. Here, we demonstrate that both IV administration of SDF-1 and stabilization of endogenous SDF-1 acutely increase MK-vasculature association and thrombopoiesis with no change in MK number. In the setting of radiation injury, we find dynamic fluctuations in marrow SDF-1 distribution that spatially and temporally correlate with variations in MK niche occupancy. Stabilization of altered SDF-1 gradients directly affects MK location. Importantly, these SDF-1-mediated changes have functional consequences for platelet production, as the movement of MKs away from the vasculature decreases circulating platelets, while MK association with the vasculature increases circulating platelets. Finally, we demonstrate that manipulation of SDF-1 gradients can improve radiation-induced thrombocytopenia in a manner additive with earlier TPO treatment. Taken together, our data support the concept that SDF-1 regulates the spatial distribution of MKs in the marrow and consequently circulating platelet numbers. This knowledge of the microenvironmental regulation of the MK lineage could lead to improved therapeutic strategies for thrombocytopenia.
Assuntos
Movimento Celular , Quimiocina CXCL12/fisiologia , Megacariócitos/citologia , Megacariócitos/fisiologia , Lesões Experimentais por Radiação , Nicho de Células-Tronco/genética , Trombopoese/genética , Animais , Células da Medula Óssea/citologia , Células da Medula Óssea/efeitos dos fármacos , Células da Medula Óssea/fisiologia , Células da Medula Óssea/efeitos da radiação , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Diferenciação Celular/efeitos da radiação , Movimento Celular/efeitos dos fármacos , Movimento Celular/genética , Movimento Celular/efeitos da radiação , Células Cultivadas , Quimiocina CXCL12/administração & dosagem , Feminino , Células Progenitoras de Megacariócitos/citologia , Células Progenitoras de Megacariócitos/efeitos dos fármacos , Células Progenitoras de Megacariócitos/fisiologia , Células Progenitoras de Megacariócitos/efeitos da radiação , Megacariócitos/efeitos dos fármacos , Megacariócitos/efeitos da radiação , Camundongos , Camundongos Endogâmicos C57BL , Lesões Experimentais por Radiação/genética , Lesões Experimentais por Radiação/patologia , Receptores CXCR4/administração & dosagem , Receptores CXCR4/metabolismo , Nicho de Células-Tronco/efeitos dos fármacos , Nicho de Células-Tronco/efeitos da radiação , Trombopoese/efeitos dos fármacos , Trombopoese/efeitos da radiaçãoRESUMO
Erythroid ontogeny is characterized by overlapping waves of primitive and definitive erythroid lineages that share many morphologic features during terminal maturation but have marked differences in cell size and globin expression. In the present study, we compared global gene expression in primitive, fetal definitive, and adult definitive erythroid cells at morphologically equivalent stages of maturation purified from embryonic, fetal, and adult mice. Surprisingly, most transcriptional complexity in erythroid precursors is already present by the proerythroblast stage. Transcript levels are markedly modulated during terminal erythroid maturation, but housekeeping genes are not preferentially lost. Although primitive and definitive erythroid lineages share a large set of nonhousekeeping genes, annotation of lineage-restricted genes shows that alternate gene usage occurs within shared functional categories, as exemplified by the selective expression of aquaporins 3 and 8 in primitive erythroblasts and aquaporins 1 and 9 in adult definitive erythroblasts. Consistent with the known functions of Aqp3 and Aqp8 as H2O2 transporters, primitive, but not definitive, erythroblasts preferentially accumulate reactive oxygen species after exogenous H2O2 exposure. We have created a user-friendly Web site (http://www.cbil.upenn.edu/ErythronDB) to make these global expression data readily accessible and amenable to complex search strategies by the scientific community.
Assuntos
Células Eritroides/metabolismo , Eritropoese/genética , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Animais , Aquaporina 1/genética , Aquaporina 3/genética , Aquaporinas/genética , Linhagem da Célula/genética , Células Cultivadas , Eritroblastos/metabolismo , Eritrócitos/metabolismo , Feminino , Sistema Hematopoético/citologia , Sistema Hematopoético/embriologia , Sistema Hematopoético/crescimento & desenvolvimento , Camundongos , Camundongos Endogâmicos ICR , Espécies Reativas de Oxigênio/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de TempoRESUMO
Erythropoiesis is a robust process of cellular expansion and maturation occurring in murine bone marrow and spleen. We previously determined that sublethal irradiation, unlike bleeding or hemolysis, depletes almost all marrow and splenic erythroblasts but leaves peripheral erythrocytes intact. To better understand the erythroid stress response, we analyzed progenitor, precursor, and peripheral blood compartments of mice post-4 Gy total body irradiation. Erythroid recovery initiates with rapid expansion of late-stage erythroid progenitors-day 3 burst-forming units and colony-forming units, associated with markedly increased plasma erythropoietin (EPO). Although initial expansion of late-stage erythroid progenitors is dependent on EPO, this cellular compartment becomes sharply down-regulated despite elevated EPO levels. Loss of EPO-responsive progenitors is associated temporally with a wave of maturing erythroid precursors in marrow and with emergence of circulating erythroid progenitors and subsequent reestablishment of splenic erythropoiesis. These circulating progenitors selectively engraft and mature in irradiated spleen after short-term transplantation, supporting the concept that bone marrow erythroid progenitors migrate to spleen. We conclude that sublethal radiation is a unique model of endogenous stress erythropoiesis, with specific injury to the extravascular erythron, expansion and maturation of EPO-responsive late-stage progenitors exclusively in marrow, and subsequent reseeding of extramedullary sites.
Assuntos
Medula Óssea/patologia , Células Precursoras Eritroides/citologia , Eritropoese/fisiologia , Eritropoetina/administração & dosagem , Lesões Experimentais por Radiação/prevenção & controle , Baço/citologia , Animais , Medula Óssea/efeitos da radiação , Proliferação de Células , Ensaio de Unidades Formadoras de Colônias , Transfusão de Eritrócitos , Células Precursoras Eritroides/efeitos da radiação , Eritropoese/efeitos da radiação , Eritropoetina/sangue , Feminino , Camundongos , Camundongos Endogâmicos C57BL , Lesões Experimentais por Radiação/etiologia , Lesões Experimentais por Radiação/patologia , Baço/efeitos da radiação , Células-Tronco , Irradiação Corporal TotalRESUMO
The limited proliferative capacity of erythroid precursors is a major obstacle to generate sufficient numbers of in vitro-derived red blood cells (RBC) for clinical purposes. We and others have determined that BMI1, a member of the polycomb repressive complex 1 (PRC1), is both necessary and sufficient to drive extensive proliferation of self-renewing erythroblasts (SREs). However, the mechanisms of BMI1 action remain poorly understood. BMI1 overexpression led to 10 billion-fold increase BMI1-induced (i)SRE self-renewal. Despite prolonged culture and BMI1 overexpression, human iSREs can terminally mature and agglutinate with typing reagent monoclonal antibodies against conventional RBC antigens. BMI1 and RING1B occupancy, along with repressive histone marks, were identified at known BMI1 target genes, including the INK-ARF locus, consistent with an altered cell cycle following BMI1 inhibition. We also identified upregulated BMI1 target genes with low repressive histone modifications, including key regulator of cholesterol homeostasis. Functional studies suggest that both cholesterol import and synthesis are essential for BMI1-associated self-renewal. These findings support the hypothesis that BMI1 regulates erythroid self-renewal not only through gene repression but also through gene activation and offer a strategy to expand the pool of immature erythroid precursors for eventual clinical uses.
RESUMO
In mammalian nuclei, a select number of tissue-specific gene loci exhibit broadly distributed patterns of histone modifications, such as histone hyperacetylation, that are normally associated with active gene promoters. Previously, we characterized such hyperacetylated domains within mammalian ß-globin gene loci, and determined that within the murine locus, neither the ß-globin locus control region nor the gene promoters were required for domain formation. Here, we identify a developmentally specific erythroid enhancer, hypersensitive site-embryonic 1 (HS-E1), located within the embryonic ß-globin domain in mouse, which is homologous to a region located downstream of the human embryonic ε-globin gene. This sequence exhibits nuclease hypersensitivity in primitive erythroid cells and acts as an enhancer in gain-of-function assays. Deletion of HS-E1 from the endogenous murine ß-globin locus results in significant decrease in the expression of the embryonic ß-globin genes and loss of the domain-wide pattern of histone hyperacetylation. The data suggest that HS-E1 is an enhancer that is uniquely required for ß-like globin expression in primitive erythroid cells, and that it defines a novel class of enhancer that works in part by domain-wide modulation of chromatin structure.
Assuntos
Elementos Facilitadores Genéticos/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Histonas/metabolismo , Globinas beta/genética , Acetilação , Animais , Imunoprecipitação da Cromatina , Embrião de Mamíferos , Células Eritroides/metabolismo , Expressão Gênica , Histonas/genética , Camundongos , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
A transient erythromyeloid wave of definitive hematopoietic progenitors (erythroid/myeloid progenitors [EMPs]) emerges in the yolk sac beginning at embryonic day 8.25 (E8.25) and colonizes the liver by E10.5, before adult-repopulating hematopoietic stem cells. At E11.5, we observe all maturational stages of erythroid precursors in the liver and the first definitive erythrocytes in the circulation. These early fetal liver erythroblasts express predominantly adult ß-globins and the definitive erythroid-specific transcriptional modifiers c-myb, Sox6, and Bcl11A. Surprisingly, they also express low levels of "embryonic" ßH1-, but not εy-, globin transcripts. Consistent with these results, RNA polymerase and highly modified histones are found associated with ßH1- and adult globin, but not εy-globin, genes. E11.5 definitive proerythroblasts from mice transgenic for the human ß-globin locus, like human fetal erythroblasts, express predominately human γ-, low ß-, and no ε-globin transcripts. Significantly, E9.5 yolk sac-derived EMPs cultured in vitro have similar murine and human transgenic globin expression patterns. Later liver proerythroblasts express low levels of γ-globin, while adult marrow proerythroblasts express only ß-globin transcripts. We conclude that yolk sac-derived EMPs, the first of 2 origins of definitive erythropoiesis, express a unique pattern of globin genes as they generate the first definitive erythrocytes in the liver of the mammalian embryo.
Assuntos
Células Eritroides/citologia , Eritropoese/fisiologia , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Células-Tronco Hematopoéticas/citologia , Fígado , Globinas beta/genética , Animais , Animais não Endogâmicos , Linhagem da Célula/fisiologia , Eritroblastos/citologia , Eritrócitos/citologia , Fator de Transcrição GATA1/genética , Células-Tronco Hematopoéticas/fisiologia , Humanos , Fatores de Transcrição Kruppel-Like/genética , Fígado/citologia , Fígado/embriologia , Fígado/fisiologia , Mamíferos , Camundongos , Camundongos Transgênicos , Saco Vitelino/fisiologiaRESUMO
Primitive erythropoiesis is a critical component of the fetal cardiovascular network and is essential for the growth and survival of the mammalian embryo. The need to rapidly establish a functional cardiovascular system is met, in part, by the intravascular circulation of primitive erythroid precursors that mature as a single semisynchronous cohort. To better understand the processes that regulate erythroid precursor maturation, we analyzed the proteome, metabolome, and lipidome of primitive erythroblasts isolated from embryonic day (E) 10.5 and E12.5 of mouse gestation, representing their transition from basophilic erythroblast to orthochromatic erythroblast (OrthoE) stages of maturation. Previous transcriptional and biomechanical characterizations of these precursors have highlighted a transition toward the expression of protein elements characteristic of mature red blood cell structure and function. Our analysis confirmed a loss of organelle-specific protein components involved in messenger RNA processing, proteostasis, and metabolism. In parallel, we observed metabolic rewiring toward the pentose phosphate pathway, glycolysis, and the Rapoport-Luebering shunt. Activation of the pentose phosphate pathway in particular may have stemmed from increased expression of hemoglobin chains and band 3, which together control oxygen-dependent metabolic modulation. Increased expression of several antioxidant enzymes also indicated modification to redox homeostasis. In addition, accumulation of oxylipins and cholesteryl esters in primitive OrthoE cells was paralleled by increased transcript levels of the p53-regulated cholesterol transporter (ABCA1) and decreased transcript levels of cholesterol synthetic enzymes. The present study characterizes the extensive metabolic rewiring that occurs in primary embryonic erythroid precursors as they prepare to enucleate and continue circulating without internal organelles.
Assuntos
Eritroblastos , Proteômica , Animais , Embrião de Mamíferos/metabolismo , Eritroblastos/metabolismo , Eritropoese/genética , Hemoglobinas/metabolismo , Mamíferos , CamundongosRESUMO
BACKGROUND: Condensation of chromatin prior to enucleation is an essential component of terminal erythroid maturation, and defects in this process are associated with inefficient erythropoiesis and anemia. However, the mechanisms involved in this phenomenon are not well understood. Here, we describe a potential role for the histone variant H2A.X in erythropoiesis. RESULTS: We find in multiple model systems that this histone is essential for normal maturation, and that the loss of H2A.X in erythroid cells results in dysregulation in expression of erythroid-specific genes as well as a nuclear condensation defect. In addition, we demonstrate that erythroid maturation is characterized by phosphorylation at both S139 and Y142 on the C-terminal tail of H2A.X during late-stage erythropoiesis. Knockout of the kinase BAZ1B/WSTF results in loss of Y142 phosphorylation and a defect in nuclear condensation, but does not replicate extensive transcriptional changes to erythroid-specific genes observed in the absence of H2A.X. CONCLUSIONS: We relate these findings to Caspase-Initiated Chromatin Condensation (CICC) in terminal erythroid maturation, where aspects of the apoptotic pathway are invoked while apoptosis is specifically suppressed.
Assuntos
Cromatina , Eritropoese , Caspases , Histonas/metabolismo , FosforilaçãoRESUMO
Hematopoietic ontogeny consists of two broad programs: an initial hematopoietic stem cell (HSC)-independent program followed by HSC-dependent hematopoiesis that sequentially seed the fetal liver and generate blood cells. However, the transition from HSC-independent to HSC-derived hematopoiesis remains poorly characterized. To help resolve this question, we developed Mds1CreERT2 mice, which inducibly express Cre-recombinase in emerging HSCs in the aorta and label long-term adult HSCs, but not HSC-independent yolk-sac-derived primitive or definitive erythromyeloid (EMP) hematopoiesis. Our lineage-tracing studies indicate that HSC-derived erythroid, myeloid, and lymphoid progeny significantly expand in the liver and blood stream between E14.5 and E16.5. Additionally, we find that HSCs contribute the majority of F4/80+ macrophages in adult spleen and marrow, in contrast to their limited contribution to macrophage populations in brain, liver, and lungs. The Mds1CreERT2 mouse model will be useful to deconvolute the complexity of hematopoiesis as it unfolds in the embryo and functions postnatally.
Assuntos
Envelhecimento/metabolismo , Alelos , Células-Tronco Hematopoéticas/metabolismo , Integrases/metabolismo , Animais , Linhagem da Célula/efeitos dos fármacos , Embrião de Mamíferos/metabolismo , Feto/citologia , Hemangioblastos/metabolismo , Hematopoese/efeitos dos fármacos , Fígado/embriologia , Proteína do Locus do Complexo MDS1 e EVI1 , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Tamoxifeno/farmacologiaRESUMO
Organogenesis is dependent on the formation of distinct cell types within the embryo. Important to this process are the hox genes, which are believed to confer positional identities to cells along the anteroposterior axis. Here, we have identified the caudal-related gene cdx4 as the locus mutated in kugelig (kgg), a zebrafish mutant with an early defect in haematopoiesis that is associated with abnormal anteroposterior patterning and aberrant hox gene expression. The blood deficiency in kgg embryos can be rescued by overexpressing hoxb7a or hoxa9a but not hoxb8a, indicating that the haematopoietic defect results from perturbations in specific hox genes. Furthermore, the haematopoietic defect in kgg mutants is not rescued by scl overexpression, suggesting that cdx4 and hox genes act to make the posterior mesoderm competent for blood development. Overexpression of cdx4 during zebrafish development or in mouse embryonic stem cells induces blood formation and alters hox gene expression. Taken together, these findings demonstrate that cdx4 regulates hox genes and is necessary for the specification of haematopoietic cell fate during vertebrate embryogenesis.
Assuntos
Genes Homeobox/fisiologia , Células-Tronco Hematopoéticas/metabolismo , Proteínas de Homeodomínio/metabolismo , Mutação/genética , Proteínas de Peixe-Zebra/metabolismo , Peixe-Zebra/embriologia , Animais , Padronização Corporal , Linhagem Celular , Clonagem Molecular , Regulação da Expressão Gênica no Desenvolvimento , Genes Homeobox/genética , Genótipo , Hematopoese , Células-Tronco Hematopoéticas/citologia , Proteínas de Homeodomínio/genética , Rim/embriologia , Camundongos , Dados de Sequência Molecular , Família Multigênica/genética , Fenótipo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Peixe-Zebra/genética , Proteínas de Peixe-Zebra/genéticaRESUMO
Stratification of enhancers by signal strength in ChIP-seq assays has resulted in the establishment of super-enhancers as a widespread and useful tool for identifying cell type-specific, highly expressed genes and associated pathways. We examine a distinct method of stratification that focuses on peak breadth, termed hyperacetylated chromatin domains (HCDs), which classifies broad regions exhibiting histone modifications associated with gene activation. We find that this analysis serves to identify genes that are both more highly expressed and more closely aligned to cell identity than super-enhancer analysis does using multiple data sets. Moreover, genetic manipulations of selected gene loci suggest that some enhancers located within HCDs work at least in part via a distinct mechanism involving the modulation of histone modifications across domains and that this activity can be imported into a heterologous gene locus. In addition, such genetic dissection reveals that the super-enhancer concept can obscure important functions of constituent elements.
Assuntos
Cromatina/metabolismo , Elementos Facilitadores Genéticos/genética , Loci Gênicos/genética , Ativação Transcricional , Acetilação , Animais , Linhagem Celular Tumoral , Imunoprecipitação da Cromatina , Sequenciamento de Cromatina por Imunoprecipitação , Conjuntos de Dados como Assunto , Embrião de Mamíferos , Eritroblastos , Feminino , Feto , Código das Histonas/genética , Histonas/genética , Histonas/metabolismo , Humanos , Camundongos , Regiões Promotoras Genéticas/genética , RNA-SeqRESUMO
Natural killer (NK) cells are a critical component of the innate immune system. However, their ontogenic origin has remained unclear. Here, we report that NK cell potential first arises from Hoxaneg/low Kit+CD41+CD16/32+ hematopoietic-stem-cell (HSC)-independent erythro-myeloid progenitors (EMPs) present in the murine yolk sac. EMP-derived NK cells and primary fetal NK cells, unlike their adult counterparts, exhibit robust degranulation in response to stimulation. Parallel studies using human pluripotent stem cells (hPSCs) revealed that HOXAneg/low CD34+ progenitors give rise to NK cells that, similar to murine EMP-derived NK cells, harbor a potent cytotoxic degranulation bias. In contrast, hPSC-derived HOXA+ CD34+ progenitors, as well as human cord blood CD34+ cells, give rise to NK cells that exhibit an attenuated degranulation response but robustly produce inflammatory cytokines. Collectively, our studies identify an extra-embryonic origin of potently cytotoxic NK cells, suggesting that ontogenic origin is a relevant factor in designing hPSC-derived adoptive immunotherapies.
Assuntos
Diferenciação Celular , Linhagem da Célula , Células-Tronco Embrionárias/citologia , Células Precursoras Eritroides/citologia , Células-Tronco Hematopoéticas/citologia , Células Matadoras Naturais/patologia , Células Progenitoras Mieloides/citologia , Animais , Células-Tronco Embrionárias/metabolismo , Células Precursoras Eritroides/metabolismo , Feminino , Hematopoese , Células-Tronco Hematopoéticas/metabolismo , Humanos , Células Matadoras Naturais/metabolismo , Masculino , Camundongos , Células Progenitoras Mieloides/metabolismo , Saco VitelinoRESUMO
The gene expression program underlying the specification of human cell types is of fundamental interest. We generated human cell atlases of gene expression and chromatin accessibility in fetal tissues. For gene expression, we applied three-level combinatorial indexing to >110 samples representing 15 organs, ultimately profiling ~4 million single cells. We leveraged the literature and other atlases to identify and annotate hundreds of cell types and subtypes, both within and across tissues. Our analyses focused on organ-specific specializations of broadly distributed cell types (such as blood, endothelial, and epithelial), sites of fetal erythropoiesis (which notably included the adrenal gland), and integration with mouse developmental atlases (such as conserved specification of blood cells). These data represent a rich resource for the exploration of in vivo human gene expression in diverse tissues and cell types.
Assuntos
Cromatina/metabolismo , Feto/citologia , Feto/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Análise de Célula Única , Atlas como Assunto , Humanos , Neurônios/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Ascl3, also know as Sgn1, is a member of the mammalian achaete scute (Mash) gene family of transcription factors, which have been implicated in cell fate specification and differentiation. In the mouse salivary gland, expression of Ascl3 is restricted to a subset of duct cells. Salivary gland function depends on the secretory acinar cells, which are responsible for saliva formation, and duct cells, which modify the saliva and conduct it to the oral cavity. The salivary gland ducts are also the putative site of progenitor cells in the adult gland. Using a Cre recombinase-mediated reporter system, we followed the fate of Ascl3-expressing cells after the introduction of an EGFP-Cre expression cassette into the Ascl3 locus by homologous recombination. Lineage tracing shows that these cells are progenitors of both acinar and ductal cell types in all three major salivary glands. In the differentiated progeny, expression of Ascl3 is down-regulated. These data directly demonstrate a progenitor-progeny relationship between duct cells and the acinar cell compartment, and identify a population of multipotent progenitor cells, marked by expression of Ascl3, which is capable of generating both gland cell types. We conclude that Ascl3-expressing cells contribute to the maintenance of the adult salivary glands.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Glândulas Salivares/citologia , Glândulas Salivares/metabolismo , Células-Tronco/citologia , Envelhecimento , Alelos , Animais , Compartimento Celular , Linhagem da Célula , Desenvolvimento Embrionário , Proteínas de Fluorescência Verde/metabolismo , Integrases/metabolismo , Camundongos , Ductos Salivares/citologia , Ductos Salivares/embriologia , Glândulas Salivares/embriologia , Glândula Sublingual/citologia , Glândula Sublingual/embriologiaRESUMO
Sox6 is a member of the Sox transcription factor family that is defined by the conserved high mobility group (HMG) DNA binding domain, first described in the testis determining gene, Sry. Previous studies have suggested that Sox6 plays a role in the development of the central nervous system, cartilage, and muscle. In the Sox6-deficient mouse, p100H, epsilony globin is persistently expressed, and increased numbers of nucleated red cells are present in the fetal circulation. Transfection assays in GM979 (erythroleukemic) cells define a 36-base pair region of the epsilony proximal promoter that is critical for Sox6 mediated repression. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays demonstrate that Sox6 acts as a repressor by directly binding to the epsilony promoter. The normal expression of Sox6 in wild-type fetal liver and the ectopic expression of epsilony in p100H homozygous fetal liver demonstrate that Sox6 functions in definitive erythropoiesis. The present study shows that Sox6 is required for silencing of epsilony globin in definitive erythropoiesis and suggests a role for Sox6 in erythroid cell maturation. Thus, Sox6 regulation of epsilony globin might provide a novel therapeutical target in the treatment of hemoglobinopathies such as sickle cell anemia and thalassemia.
Assuntos
Proteínas de Ligação a DNA/fisiologia , Eritropoese/genética , Globinas/genética , Proteínas de Grupo de Alta Mobilidade/fisiologia , Fatores de Transcrição/fisiologia , Animais , Núcleo Celular/metabolismo , Imunoprecipitação da Cromatina , Eritrócitos/metabolismo , Homozigoto , Humanos , Camundongos , Camundongos Transgênicos , Regiões Promotoras Genéticas , Ligação Proteica , Fatores de Transcrição SOXD , Transcrição Gênica , TransfecçãoRESUMO
Purpose: Incidents, such as nuclear facility accidents and the release of a 'dirty bomb', might result in not only external irradiation of personnel, but additional internal exposures through concomitant inhalation and/or ingestion of radioactive particulates. The purpose of this study was to define the impact of such a combination of radiation injuries on the hematopoietic niche.Material and methods: To assess changes in the murine hematopoietic system, we used a combined exposure of total body irradiation (TBI, 6 Gy) followed immediately by an internal (intraperitoneal) administration of 100 µCi of soluble 137Cs. We then evaluated acute survival in combined versus single modality exposure groups, as well as assessing hematopoietic function at 12 and 26 week time points.Results: Acutely, the combination of external and internal exposures led to an unexpected delay in excretion of 137Cs, increasing the absorbed dose in the combined exposure group and leading to mortality from an acute hematopoietic syndrome. At 12 weeks, all exposure paradigms resulted in decreased numbers of phenotypic hematopoietic stem cells (HSCs), particularly the short-term HSCs (ST-HSC); long-term HSCs (LT-HSC) were depleted only in the internal and combined exposure groups. At 26 weeks, there was significant anemia in both the TBI alone and combined exposure groups. There were decreased numbers in both the LT- and ST-HSCs and decreased functionality, as measured by competitive repopulation, was seen in all radiation groups, with the greatest effects seen in the internal and combined exposure groups.Conclusions: Our data indicate that a combined injury of sublethal external irradiation with internal contamination induces significant and persistent changes in the hematopoietic system, as may have been predicted from the literature and our own group's findings. However, a novel observation was that the combined exposure led to an alteration in the excretion kinetics of the internal contamination, increasing the acute effects beyond those anticipated. As a result, we believe that a combined exposure poses a unique challenge to the medical community during both the acute and, possibly, delayed recovery stages.
Assuntos
Medula Óssea/efeitos da radiação , Hematopoese/efeitos da radiação , Células-Tronco Hematopoéticas/efeitos da radiação , Estresse Oxidativo/efeitos da radiação , Irradiação Corporal Total , Animais , Células Cultivadas , Radioisótopos de Césio , Feminino , Humanos , Estimativa de Kaplan-Meier , Camundongos , Camundongos Endogâmicos C57BL , Fenótipo , Lesões Experimentais por Radiação/fisiopatologia , Espécies Reativas de Oxigênio/metabolismoRESUMO
Platelets are essential for hemostasis; however, several studies have identified age-dependent differences in platelet function. To better understand the origins of fetal platelet function, we have evaluated the contribution of the fetal-specific RNA binding protein Lin28b in the megakaryocyte/platelet lineage. Because activated fetal platelets have very low levels of P-selectin, we hypothesized that the expression of platelet P-selectin is part of a fetal-specific hematopoietic program conferred by Lin28b. Using the mouse as a model, we find that activated fetal platelets have low levels of P-selectin and do not readily associate with granulocytes in vitro and in vivo, relative to adult controls. Transcriptional analysis revealed high levels of Lin28b and Hmga2 in fetal, but not adult, megakaryocytes. Overexpression of LIN28B in adult mice significantly reduces the expression of P-selectin in platelets, and therefore identifies Lin28b as a negative regulator of P-selectin expression. Transplantation of fetal hematopoietic progenitors resulted in the production of platelets with low levels of P-selectin, suggesting that the developmental regulation of P-selectin is intrinsic and independent of differences between fetal and adult microenvironments. Last, we observe that the upregulation of P-selectin expression occurs postnatally, and the temporal kinetics of this upregulation are recapitulated by transplantation of fetal hematopoietic stem and progenitor cells into adult recipients. Taken together, these studies identify Lin28b as a new intrinsic regulator of fetal platelet function.
Assuntos
Plaquetas/metabolismo , Regulação da Expressão Gênica , Proteínas de Ligação a RNA/genética , Fatores Etários , Animais , Biomarcadores , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/metabolismo , Leucócitos/imunologia , Leucócitos/metabolismo , Megacariócitos/citologia , Megacariócitos/metabolismo , Camundongos , Selectina-P/genética , Selectina-P/metabolismo , Ativação Plaquetária , Agregação Plaquetária/genética , Testes de Função Plaquetária , Proteínas de Ligação a RNA/metabolismoRESUMO
Hematopoiesis is precisely orchestrated by lineage-specific DNA-binding proteins that regulate transcription in concert with coactivators and corepressors. Mutations in the zebrafish moonshine (mon) gene specifically disrupt both embryonic and adult hematopoiesis, resulting in severe red blood cell aplasia. We report that mon encodes the zebrafish ortholog of mammalian transcriptional intermediary factor 1gamma (TIF1gamma) (or TRIM33), a member of the TIF1 family of coactivators and corepressors. During development, hematopoietic progenitor cells in mon mutants fail to express normal levels of hematopoietic transcription factors, including gata1, and undergo apoptosis. Three different mon mutant alleles each encode premature stop codons, and enforced expression of wild-type tif1gamma mRNA rescues embryonic hematopoiesis in homozygous mon mutants. Surprisingly, a high level of zygotic tif1gamma mRNA expression delineates ventral mesoderm during hematopoietic stem cell and progenitor formation prior to gata1 expression. Transplantation studies reveal that tif1gamma functions in a cell-autonomous manner during the differentiation of erythroid precursors. Studies in murine erythroid cell lines demonstrate that Tif1gamma protein is localized within novel nuclear foci, and expression decreases during erythroid cell maturation. Our results establish a major role for this transcriptional intermediary factor in the differentiation of hematopoietic cells in vertebrates.
Assuntos
Eritrócitos/patologia , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologia , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/fisiologia , Alelos , Animais , Apoptose , Transplante de Medula Óssea , Diferenciação Celular , Linhagem Celular , Núcleo Celular/metabolismo , Sobrevivência Celular , Transplante de Células , Clonagem Molecular , Códon de Terminação , DNA/química , Proteínas de Ligação a DNA/química , Eritrócitos/citologia , Regulação da Expressão Gênica , Hematopoese , Células-Tronco Hematopoéticas/citologia , Heterocromatina/metabolismo , Homozigoto , Immunoblotting , Camundongos , Dados de Sequência Molecular , Mutação , Fenótipo , Ligação Proteica , RNA Mensageiro/metabolismo , Fatores de Transcrição/metabolismo , Transcrição Gênica , Peixe-Zebra , Proteínas de Peixe-Zebra/químicaRESUMO
Primitive erythroblasts (precursors of red blood cells) enter vascular circulation during the embryonic period and mature while circulating. As a result, primitive erythroblasts constantly experience significant hemodynamic shear stress. Shear-induced deformation of primitive erythroblasts however, is poorly studied. In this work, we examined the deformability of primitive erythroblasts at physiologically relevant flow conditions in microfluidic channels and identified the regulatory roles of the maturation stage of primitive erythroblasts and cytoskeletal protein 4.1 R in shear-induced cell deformation. The results showed that the maturation stage affected the deformability of primitive erythroblasts significantly and that primitive erythroblasts at later maturational stages exhibited a better deformability due to a matured cytoskeletal structure in the cell membrane.