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1.
Genes (Basel) ; 14(10)2023 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-37895228

RESUMO

The Polycomb repressive complex 2 (PRC2) is a conserved chromatin-remodelling complex that catalyses the trimethylation of histone H3 lysine 27 (H3K27me3), a mark associated with gene silencing. PRC2 regulates chromatin structure and gene expression during organismal and tissue development and tissue homeostasis in the adult. PRC2 core subunits are associated with various accessory proteins that modulate its function and recruitment to target genes. The multimeric composition of accessory proteins results in two distinct variant complexes of PRC2, PRC2.1 and PRC2.2. Metal response element-binding transcription factor 2 (MTF2) is one of the Polycomb-like proteins (PCLs) that forms the PRC2.1 complex. MTF2 is highly conserved, and as an accessory subunit of PRC2, it has important roles in embryonic stem cell self-renewal and differentiation, development, and cancer progression. Here, we review the impact of MTF2 in PRC2 complex assembly, catalytic activity, and spatiotemporal function. The emerging paradoxical evidence suggesting that MTF2 has divergent roles as either a tumour suppressor or an oncogene in different tissues merits further investigations. Altogether, our review illuminates the context-dependent roles of MTF2 in Polycomb group (PcG) protein-mediated epigenetic regulation. Its impact on disease paves the way for a deeper understanding of epigenetic regulation and novel therapeutic strategies.


Assuntos
Proteínas de Drosophila , Histonas , Animais , Humanos , Cromatina , Proteínas de Drosophila/genética , Epigênese Genética , Histonas/genética , Histonas/metabolismo , Complexo Repressor Polycomb 2/genética , Complexo Repressor Polycomb 2/metabolismo , Proteínas do Grupo Polycomb/genética , Proteínas do Grupo Polycomb/metabolismo , Ligação Proteica
2.
Cancer Discov ; 8(11): 1376-1389, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30115703

RESUMO

Deep sequencing has revealed that epigenetic modifiers are the most mutated genes in acute myeloid leukemia (AML). Thus, elucidating epigenetic dysregulation in AML is crucial to understand disease mechanisms. Here, we demonstrate that metal response element binding transcription factor 2/polycomblike 2 (MTF2/PCL2) plays a fundamental role in the polycomb repressive complex 2 (PRC2) and that its loss elicits an altered epigenetic state underlying refractory AML. Unbiased systems analyses identified the loss of MTF2-PRC2 repression of MDM2 as central to, and therefore a biomarker for, refractory AML. Thus, immature MTF2-deficient CD34+CD38- cells overexpress MDM2, thereby inhibiting p53 that leads to chemoresistance due to defects in cell-cycle regulation and apoptosis. Targeting this dysregulated signaling pathway by MTF2 overexpression or MDM2 inhibitors sensitized refractory patient leukemic cells to induction chemotherapeutics and prevented relapse in AML patient-derived xenograft mice. Therefore, we have uncovered a direct epigenetic mechanism by which MTF2 functions as a tumor suppressor required for AML chemotherapeutic sensitivity and identified a potential therapeutic strategy to treat refractory AML.Significance: MTF2 deficiency predicts refractory AML at diagnosis. MTF2 represses MDM2 in hematopoietic cells and its loss in AML results in chemoresistance. Inhibiting p53 degradation by overexpressing MTF2 in vitro or by using MDM2 inhibitors in vivo sensitizes MTF2-deficient refractory AML cells to a standard induction-chemotherapy regimen. Cancer Discov; 8(11); 1376-89. ©2018 AACR. See related commentary by Duy and Melnick, p. 1348 This article is highlighted in the In This Issue feature, p. 1333.


Assuntos
Daunorrubicina/farmacologia , Resistencia a Medicamentos Antineoplásicos , Leucemia Mieloide Aguda/tratamento farmacológico , Complexo Repressor Polycomb 2/metabolismo , Proteínas Proto-Oncogênicas c-mdm2/metabolismo , Animais , Antibióticos Antineoplásicos/farmacologia , Humanos , Leucemia Mieloide Aguda/imunologia , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/patologia , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Complexo Repressor Polycomb 2/antagonistas & inibidores , Complexo Repressor Polycomb 2/genética , Proteínas Proto-Oncogênicas c-mdm2/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-mdm2/genética , Células Tumorais Cultivadas , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Ensaios Antitumorais Modelo de Xenoenxerto
3.
Stem Cells Dev ; 27(16): 1109-1124, 2018 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-29957134

RESUMO

Bronchopulmonary dysplasia (BPD), the most common complication of extreme preterm birth, can be caused by oxygen-related lung injury and is characterized by impaired alveolar and vascular development. Mesenchymal stromal cells (MSCs) have lung protective effects. Conversely, BPD is associated with increased MSCs in tracheal aspirates. We hypothesized that endogenous lung (L-)MSCs are perturbed in a well-established oxygen-induced rat model mimicking BPD features. Rat pups were exposed to 21% or 95% oxygen from birth to postnatal day 10. On day 12, CD146+ L-MSCs were isolated and characterized according to the International Society for Cellular Therapy criteria. Epithelial and vascular repair potential were tested by scratch assay and endothelial network formation, respectively, immune function by mixed lymphocyte reaction assay. Microarray analysis was performed using the Affymetrix GeneChip and gene set enrichment analysis software. CD146+ L-MSCs isolated from rat pups exposed to hyperoxia had decreased CD73 expression and inhibited lung endothelial network formation. CD146+ L-MSCs indiscriminately promoted epithelial wound healing and limited T cell proliferation. Expression of potent antiangiogenic genes of the axonal guidance cue and CDC42 pathways was increased after in vivo hyperoxia, whereas genes of the anti-inflammatory Janus kinase (JAK)/signal transducer and activator of transcription (STAT) and lung/vascular growth-promoting fibroblast growth factor (FGF) pathways were decreased. In conclusion, in vivo hyperoxia exposure alters the proangiogenic effects and FGF expression of L-MSCs. In addition, decreased CD73 and JAK/STAT expression suggests decreased immune function. L-MSC function may be perturbed and contribute to BPD pathogenesis. These findings may lead to improvements in manufacturing exogenous MSCs with superior repair capabilities.


Assuntos
Displasia Broncopulmonar/metabolismo , Lesão Pulmonar/metabolismo , Células-Tronco Mesenquimais/metabolismo , Oxigênio/efeitos adversos , Animais , Animais Recém-Nascidos , Displasia Broncopulmonar/etiologia , Displasia Broncopulmonar/fisiopatologia , Antígeno CD146/genética , Proliferação de Células/efeitos dos fármacos , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/patologia , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Humanos , Pulmão/metabolismo , Pulmão/patologia , Lesão Pulmonar/induzido quimicamente , Lesão Pulmonar/patologia , Células-Tronco Mesenquimais/patologia , Oxigênio/administração & dosagem , Ratos , Linfócitos T/metabolismo , Linfócitos T/patologia
4.
Cell Discov ; 4: 21, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29736258

RESUMO

Polycomb repressive complex 2 (PRC2) accessory proteins play substoichiometric, tissue-specific roles to recruit PRC2 to specific genomic loci or increase enzymatic activity, while PRC2 core proteins are required for complex stability and global levels of trimethylation of histone 3 at lysine 27 (H3K27me3). Here, we demonstrate a role for the classical PRC2 accessory protein Mtf2/Pcl2 in the hematopoietic system that is more akin to that of a core PRC2 protein. Mtf2-/- erythroid progenitors demonstrate markedly decreased core PRC2 protein levels and a global loss of H3K27me3 at promoter-proximal regions. The resulting de-repression of transcriptional and signaling networks blocks definitive erythroid development, culminating in Mtf2-/- embryos dying by e15.5 due to severe anemia. Gene regulatory network (GRN) analysis demonstrated Mtf2 directly regulates Wnt signaling in erythroblasts, leading to activated canonical Wnt signaling in Mtf2-deficient erythroblasts, while chemical inhibition of canonical Wnt signaling rescued Mtf2-deficient erythroblast differentiation in vitro. Using a combination of in vitro, in vivo and systems analyses, we demonstrate that Mtf2 is a critical epigenetic regulator of Wnt signaling during erythropoiesis and recast the role of polycomb accessory proteins in a tissue-specific context.

5.
Metabolites ; 8(1)2018 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-29495309

RESUMO

Because of their unique ability to modulate the immune system, mesenchymal stromal cells (MSCs) are widely studied to develop cell therapies for detrimental immune and inflammatory disorders. However, controlling the final cell phenotype and determining immunosuppressive function following cell amplification in vitro often requires prolonged cell culture assays, all of which contribute to major bottlenecks, limiting the clinical emergence of cell therapies. For instance, the multipotent Wharton's Jelly mesenchymal stem/stromal cells (WJMSC), extracted from human umbilical cord, exhibit immunosuppressive traits under pro-inflammatory conditions, in the presence of interferon-γ (IFNγ), and tumor necrosis factor-α (TNFα). However, WJMSCs require co-culture bioassays with immune cells, which can take days, to confirm their immunomodulatory function. Therefore, the establishment of robust cell therapies would benefit from fast and reliable characterization assays. To this end, we have explored the metabolic behaviour of WJMSCs in in vitro culture, to identify biomarkers that are specific to the cell passage effect and the loss of their immunosuppressive phenotype. We clearly show distinct metabolic behaviours comparing WJMSCs at the fourth (P4) and the late ninth (P9) passages, although both P4 and P9 cells do not exhibit significant differences in their low immunosuppressive capacity. Metabolomics data were analysed using an in silico modelling platform specifically adapted to WJMSCs. Of interest, P4 cells exhibit a glycolytic metabolism compared to late passage (P9) cells, which show a phosphorylation oxidative metabolism, while P4 cells show a doubling time of 29 h representing almost half of that for P9 cells (46 h). We also clearly show that fourth passage WJMSCs still express known immunosuppressive biomarkers, although, this behaviour shows overlapping with a senescence phenotype.

6.
Stem Cell Rev Rep ; 13(6): 817-825, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28918518

RESUMO

Gene regulatory networks in AML may be influenced by microRNAs (miRs) contained in exosomes derived from bone marrow mesenchymal stromal cells (MSCs). We sequenced miRs from exosomes isolated from marrow-derived MSCs from patients with AML (n = 3) and from healthy controls (n = 3; not age-matched). Known targets of mIRs that were significantly different in AML-derived MSC exosomes compared to controls were identified. Of the five candidate miRs identified by differential packaging in exosomes, only miR-26a-5p and miR-101-3p were significantly increased in AML-derived samples while miR-23b-5p, miR-339-3p and miR-425-5p were significantly decreased. Validation of the predicted change in gene expression of the potential targets was investigated by interrogating gene expression levels from public datasets of marrow-derived CD34-selected cells from patients with AML (n = 69) and healthy donors (n = 40). Two molecules with decreased gene expression in AML (EZH2 and GSK3ß) were predicted by the miR profiling and have been previously implicated in AML while three molecules were increased in AML-derived cells and have not been previously associated with leukemogenesis (KRBA2, RRBP1 and HIST2H 2BE). In summary, profiling miRs in exosomes from AML-derived MSCs allowed us to identify candidate miRs with potential relevance in AML that could yield new insights regarding leukemogenesis or new treatment strategies.


Assuntos
Carcinogênese/genética , Leucemia Mieloide Aguda/genética , Células-Tronco Mesenquimais/metabolismo , MicroRNAs/genética , Adulto , Idoso , Células da Medula Óssea/patologia , Diferenciação Celular/genética , Exossomos/genética , Feminino , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Humanos , Leucemia Mieloide Aguda/patologia , Masculino , Pessoa de Meia-Idade , Proteínas de Neoplasias/genética
7.
Cell Stem Cell ; 10(2): 218-29, 2012 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-22305571

RESUMO

Clinical hematopoietic transplantation outcomes are strongly correlated with the numbers of cells infused. Anticipated novel therapeutic implementations of hematopoietic stem cells (HSCs) and their derivatives further increase interest in strategies to expand HSCs ex vivo. A fundamental limitation in all HSC-driven culture systems is the rapid generation of differentiating cells and their secreted inhibitory feedback signals. Herein we describe an integrated computational and experimental strategy that enables a tunable reduction in the global levels and impact of paracrine signaling factors in an automated closed-system process by employing a controlled fed-batch media dilution approach. Application of this system to human cord blood cells yielded a rapid (12-day) 11-fold increase of HSCs with self-renewing, multilineage repopulating ability. These results highlight the marked improvements that control of feedback signaling can offer primary stem cell culture and demonstrate a clinically relevant rapid and relatively low culture volume strategy for ex vivo HSC expansion.


Assuntos
Simulação por Computador , Transplante de Células-Tronco Hematopoéticas , Células-Tronco Hematopoéticas/citologia , Animais , Técnicas de Cultura de Células/instrumentação , Técnicas de Cultura de Células/métodos , Diferenciação Celular , Proliferação de Células , Sobrevivência Celular , Meios de Cultura/metabolismo , Retroalimentação Fisiológica , Sangue Fetal/citologia , Humanos , Camundongos , Camundongos SCID , Comunicação Parácrina
8.
Mol Syst Biol ; 6: 417, 2010 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-20924352

RESUMO

Intercellular (between cell) communication networks maintain homeostasis and coordinate regenerative and developmental cues in multicellular organisms. Despite the importance of intercellular networks in stem cell biology, their rules, structure and molecular components are poorly understood. Herein, we describe the structure and dynamics of intercellular and intracellular networks in a stem cell derived, hierarchically organized tissue using experimental and theoretical analyses of cultured human umbilical cord blood progenitors. By integrating high-throughput molecular profiling, database and literature mining, mechanistic modeling, and cell culture experiments, we show that secreted factor-mediated intercellular communication networks regulate blood stem cell fate decisions. In particular, self-renewal is modulated by a coupled positive-negative intercellular feedback circuit composed of megakaryocyte-derived stimulatory growth factors (VEGF, PDGF, EGF, and serotonin) versus monocyte-derived inhibitory factors (CCL3, CCL4, CXCL10, TGFB2, and TNFSF9). We reconstruct a stem cell intracellular network, and identify PI3K, Raf, Akt, and PLC as functionally distinct signal integration nodes, linking extracellular, and intracellular signaling. This represents the first systematic characterization of how stem cell fate decisions are regulated non-autonomously through lineage-specific interactions with differentiated progeny.


Assuntos
Comunicação Celular/fisiologia , Biologia Computacional/métodos , Células-Tronco Hematopoéticas/fisiologia , Análise de Variância , Diferenciação Celular/fisiologia , Células Cultivadas , Análise por Conglomerados , Simulação por Computador , Mineração de Dados , Sangue Fetal/citologia , Perfilação da Expressão Gênica , Redes Reguladoras de Genes , Células-Tronco Hematopoéticas/citologia , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/fisiologia , Modelos Lineares , Modelos Biológicos , Transdução de Sinais
9.
Blood ; 115(2): 257-60, 2010 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-19897585

RESUMO

Phenotypic markers associated with human hematopoietic stem cells (HSCs) were developed and validated using uncultured cells. Because phenotype and function can be dissociated during culture, better markers to prospectively track and isolate HSCs in ex vivo cultures could be instrumental in advancing HSC-based therapies. Using an expansion system previously shown to increase hematopoietic progenitors and SCID-repopulating cells (SRCs), we demonstrated that the rhodamine-low phenotype was lost, whereas AC133 expression was retained throughout culture. Furthermore, the AC133(+)CD38(-) subpopulation was significantly enriched in long-term culture-initiating cells (LTC-IC) and SRCs after culture. Preculture and postculture analysis of total nucleated cell and LTC-IC number, and limiting dilution analysis in NOD/SCID mice, showed a 43-fold expansion of the AC133(+)CD38(-) subpopulation that corresponded to a 7.3-fold and 4.4-fold expansion of LTC-ICs and SRCs in this subpopulation, respectively. Thus, AC133(+)CD38(-) is an improved marker that tracks and enriches for LTC-IC and SRC in ex vivo cultures.


Assuntos
ADP-Ribosil Ciclase 1 , Antígenos CD/biossíntese , Sangue Fetal/metabolismo , Regulação da Expressão Gênica/fisiologia , Glicoproteínas/biossíntese , Células-Tronco Hematopoéticas/metabolismo , Glicoproteínas de Membrana , Antígeno AC133 , Animais , Técnicas de Cultura de Células , Células Cultivadas , Sangue Fetal/citologia , Transplante de Células-Tronco Hematopoéticas , Células-Tronco Hematopoéticas/citologia , Humanos , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Peptídeos , Transplante Heterólogo
10.
Mol Syst Biol ; 5: 293, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19638974

RESUMO

Communication networks between cells and tissues are necessary for homeostasis in multicellular organisms. Intercellular (between cell) communication networks are particularly relevant in stem cell biology, as stem cell fate decisions (self-renewal, proliferation, lineage specification) are tightly regulated based on physiological demand. We have developed a novel mathematical model of blood stem cell development incorporating cell-level kinetic parameters as functions of secreted molecule-mediated intercellular networks. By relation to quantitative cellular assays, our model is capable of predictively simulating many disparate features of both normal and malignant hematopoiesis, relating internal parameters and microenvironmental variables to measurable cell fate outcomes. Through integrated in silico and experimental analyses, we show that blood stem and progenitor cell fate is regulated by cell-cell feedback, and can be controlled non-cell autonomously by dynamically perturbing intercellular signalling. We extend this concept by demonstrating that variability in the secretion rates of the intercellular regulators is sufficient to explain heterogeneity in culture outputs, and that loss of responsiveness to cell-cell feedback signalling is both necessary and sufficient to induce leukemic transformation in silico.


Assuntos
Células Sanguíneas/citologia , Comunicação Celular , Células-Tronco Hematopoéticas/citologia , Transformação Celular Neoplásica , Células Cultivadas , Retroalimentação Fisiológica , Hematopoese , Humanos , Cinética , Leucemia/etiologia , Modelos Biológicos
11.
Biol Blood Marrow Transplant ; 12(10): 1020-30, 2006 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-17084368

RESUMO

The clinical potential of umbilical cord blood-derived stem and progenitor cells has been demonstrated in various animal and human transplantation studies. However, the need for increased numbers of appropriate umbilical cord blood-derived cells continues to limit the development and success of these therapies. Ex vivo expansion has been widely studied as a method to overcome this limitation. We describe the use of a clinically relevant single-use, closed-system bioprocess capable of generating greater numbers of hematopoietic stem and progenitor cells that maintain in vivo and in vitro developmental potential. In addition to expanded numbers of CD34+ cells, CD34(+)CD38(-) cells, colony-forming cells, and long-term culture-initiating cells, the bioprocess generated > or =3.3-fold more long-term nonobese diabetic/severe combined immunodeficient repopulating cells (quantitatively determined using limiting dilution analysis) than present at input. Interestingly, these cells were also capable of multilineage engraftment and were shown to maintain their engraftment potency on a per long-term nonobese diabetic/severe combined immunodeficient repopulating cell basis compared with input noncultured cells. The developmental capacity of bioprocess-generated cells was further demonstrated by their ability to repopulate secondary nonobese diabetic/severe combined immunodeficient recipients. In vitro lineage analysis confirmed that bioprocess-generated cells could differentiate into myeloid and natural killer, B, and T cell lymphoid lineages. This in-depth analysis describes a bioprocess that generates human hematopoietic stem and progenitor cells with conserved hematopoietic activity, establishes analysis criteria for in vitro hematopoietic stem cell expansion studies, and serves as a foundation to test the therapeutic utility of cultured hematopoietic stem cells in large animals and humans.


Assuntos
Técnicas de Cultura de Células/métodos , Sangue Fetal/citologia , Células-Tronco Hematopoéticas/citologia , Animais , Subpopulações de Linfócitos B/citologia , Subpopulações de Linfócitos B/imunologia , Técnicas de Cultura de Células/instrumentação , Diferenciação Celular , Linhagem da Célula , Separação Celular/métodos , Células Cultivadas/citologia , Ensaio de Unidades Formadoras de Colônias , Transplante de Células-Tronco de Sangue do Cordão Umbilical/métodos , Sobrevivência de Enxerto , Humanos , Imunofenotipagem , Recém-Nascido , Células Matadoras Naturais/citologia , Células Matadoras Naturais/imunologia , Linfócitos/citologia , Linfócitos/imunologia , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Quimera por Radiação , Subpopulações de Linfócitos T/citologia , Subpopulações de Linfócitos T/imunologia , Transplante Heterólogo
12.
J Cell Sci ; 118(Pt 19): 4343-52, 2005 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-16144866

RESUMO

Cells expressing the CD45-associated hematopoietic marker are predominantly present in the mammalian bone marrow (BM), but have recently been shown to also reside in the skeletal muscle and potentially participate in muscle repair. Despite the consistent observations, the specific relationship and potential migration of CD45+ cells in the BM versus CD45+ cells residing in the muscle remain unclear, in addition to any understanding of the factors that may regulate the trafficking of CD45+-derived BM cells to skeletal muscle upon i.v. transplantation. Here, transplantation of BM-derived cells fully replaced the CD45+ fraction of skeletal muscle, but gave rise to progenitor cells with distinct hematopoietic lineage capacity from CD45+ cells residing in the BM. Using transwell migration assays, a subset of BM cells was shown to migrate exclusively to mature skeletal muscle cells and not BM-derived stromal cells. Unlike migration of BM cells to stroma, myofiber induced migration of BM-derived cells was not affected by stromal-derived factor-1 (SDF-1) neutralization or CXCR4-blocking antibody, but could be reduced by addition of c-met-blocking antibody and augmented by hepatocyte growth factor (HGF), the putative ligand for c-met. We suggest that the BM compartment consists of a functionally complex population of CD45+ progenitors that includes a subset of HGF/c-met responsive cells capable of migration to skeletal muscle. This previously unappreciated basis for cellular tracking now aids in defining regulatory networks that distinguish the stem cell niche of the BM versus skeletal muscle microenvironments.


Assuntos
Células da Medula Óssea/fisiologia , Movimento Celular/fisiologia , Fator de Crescimento de Hepatócito/metabolismo , Músculo Esquelético/citologia , Proteínas Proto-Oncogênicas c-met/metabolismo , Células-Tronco/fisiologia , Células Estromais/fisiologia , Animais , Células da Medula Óssea/citologia , Linhagem da Célula , Transplante de Células , Células Cultivadas , Quimiocina CXCL12 , Quimiocinas CXC/metabolismo , Técnicas de Cocultura , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/fisiologia , Antígenos Comuns de Leucócito/metabolismo , Camundongos , Músculo Esquelético/metabolismo , Receptores CXCR4/metabolismo , Células-Tronco/citologia , Células Estromais/citologia
13.
Blood ; 101(2): 517-23, 2003 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-12393491

RESUMO

Despite its wide use as a marker for hematopoietic stem cells (HSCs), the function of stem cell antigen-1 (Sca-1) (also known as lymphocyte activation protein-6A [Ly-6A]) in hematopoiesis remains poorly defined. We have previously established that Sca-1(-/-) T cells develop normally, although they are hyperresponsive to antigen. Here, we report detailed analysis of hematopoiesis in Sca-1-deficient animals. The differentiation potential of Sca-1-null bone marrow was determined from examination of the most mature precursors (culture colony-forming units [CFU-Cs]) to less committed progenitors (spleen CFUs [CFU-Ss]) to long-term repopulating HSCs. Sca-1-null mice are mildly thrombocytopenic with a concomitant decrease in megakaryocytes and their precursors. Bone marrow cells derived from Sca-1(-/-) mice also have decreased multipotential granulocyte, erythroid, macrophage, and megakaryocyte CFU (GEMM-CFU) and CFU-S progenitor activity. Competitive repopulation assays demonstrated that Sca-1(-/-) HSCs are at a competitive disadvantage compared with wild-type HSCs. To further analyze the potential of Sca-1(-/-) HSCs, serial transplantations were performed. While secondary repopulations using wild-type bone marrow completely repopulated Sca-1(-/-) mice, Sca-1(-/-) bone marrow failed to rescue one third of lethally irradiated wild-type mice receiving secondary bone marrow transplants from irradiation-induced anemia and contributed poorly to the surviving transplant recipients. These data strongly suggest that Sca-1 is required for regulating HSC self-renewal and the development of committed progenitor cells, megakaryocytes, and platelets. Thus, our studies conclusively demonstrate that Sca-1, in addition to being a marker of HSCs, regulates the developmental program of HSCs and specific progenitor populations.


Assuntos
Antígenos Ly/fisiologia , Hematopoese , Células-Tronco Hematopoéticas/citologia , Proteínas de Membrana/fisiologia , Animais , Antígenos Ly/genética , Transplante de Medula Óssea , Linhagem da Célula , Embrião de Mamíferos/citologia , Proteínas de Membrana/deficiência , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transdução de Sinais , Taxa de Sobrevida
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