RESUMO
A classical view of blood cell development is that multipotent hematopoietic stem and progenitor cells (HSPCs) become lineage-restricted at defined stages. Lin-c-Kit+Sca-1+Flt3+ cells, termed lymphoid-primed multipotent progenitors (LMPPs), have lost megakaryocyte and erythroid potential but are heterogeneous in their fate. Here, through single-cell RNA sequencing, we identify the expression of Dach1 and associated genes in this fraction as being coexpressed with myeloid/stem genes but inversely correlated with lymphoid genes. Through generation of Dach1-GFP reporter mice, we identify a transcriptionally and functionally unique Dach1-GFP- subpopulation within LMPPs with lymphoid potential with low to negligible classic myeloid potential. We term these 'lymphoid-primed progenitors' (LPPs). These findings define an early definitive branch point of lymphoid development in hematopoiesis and a means for prospective isolation of LPPs.
Assuntos
Biomarcadores , Proteínas do Olho/metabolismo , Genômica , Células Progenitoras Linfoides/metabolismo , Análise de Célula Única , Animais , Células Cultivadas , Biologia Computacional/métodos , Proteínas do Olho/genética , Perfilação da Expressão Gênica , Genômica/métodos , Hematopoese/genética , Sequenciamento de Nucleotídeos em Larga Escala , Células Progenitoras Linfoides/citologia , Células Progenitoras Linfoides/imunologia , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Proteômica , Análise de Célula Única/métodosRESUMO
Despite significant progress in treating chronic lymphocytic leukaemia (CLL), resistance to therapy remains challenging. NOTCH1 activation, common in CLL, confers adverse prognosis. This study explores the impact of NOTCH1 signalling on venetoclax sensitivity in vitro. Although NOTCH1 activation minimally impaired the susceptibility of CLL cells to venetoclax, ex vivo cell competition studies reveal that cells with constitutive NOTCH1 activation outgrew their wild-type counterparts in the presence of ongoing venetoclax exposure. Our findings suggest that while NOTCH1 activation is insufficient to confer venetoclax refractoriness, there is enhanced potential for cells with NOTCH1 activation to escape and thus become fully resistant to venetoclax.
RESUMO
Unlike clustered HOX genes, the role of nonclustered homeobox gene family members in hematopoiesis and leukemogenesis has not been extensively studied. Here we found that the hematopoietically expressed homeobox gene Hhex is overexpressed in acute myeloid leukemia (AML) and is essential for the initiation and propagation of MLL-ENL-induced AML but dispensable for normal myelopoiesis, indicating a specific requirement for Hhex for leukemic growth. Loss of Hhex leads to expression of the Cdkn2a-encoded tumor suppressors p16(INK4a) and p19(ARF), which are required for growth arrest and myeloid differentiation following Hhex deletion. Mechanistically, we show that Hhex binds to the Cdkn2a locus and directly interacts with the Polycomb-repressive complex 2 (PRC2) to enable H3K27me3-mediated epigenetic repression. Thus, Hhex is a potential therapeutic target that is specifically required for AML stem cells to repress tumor suppressor pathways and enable continued self-renewal.
Assuntos
Inibidor p16 de Quinase Dependente de Ciclina/genética , Epigênese Genética , Proteínas de Homeodomínio/metabolismo , Leucemia Mieloide Aguda/fisiopatologia , Complexo Repressor Polycomb 2/genética , Complexo Repressor Polycomb 2/metabolismo , Fatores de Transcrição/metabolismo , Animais , Linhagem Celular Tumoral , Deleção de Genes , Regulação Neoplásica da Expressão Gênica , Proteínas de Homeodomínio/genética , Humanos , Leucemia Mieloide Aguda/genética , Camundongos , Camundongos Endogâmicos C57BL , Ligação Proteica , Fatores de Transcrição/genéticaRESUMO
Modulators of epithelial-to-mesenchymal transition (EMT) have recently emerged as novel players in the field of leukemia biology. The mechanisms by which EMT modulators contribute to leukemia pathogenesis, however, remain to be elucidated. Here we show that overexpression of SNAI1, a key modulator of EMT, is a pathologically relevant event in human acute myeloid leukemia (AML) that contributes to impaired differentiation, enhanced self-renewal, and proliferation of immature myeloid cells. We demonstrate that ectopic expression of Snai1 in hematopoietic cells predisposes mice to AML development. This effect is mediated by interaction with the histone demethylase KDM1A/LSD1. Our data shed new light on the role of SNAI1 in leukemia development and identify a novel mechanism of LSD1 corruption in cancer. This is particularly pertinent given the current interest surrounding the use of LSD1 inhibitors in the treatment of multiple different malignancies, including AML.
Assuntos
Transformação Celular Neoplásica , Transição Epitelial-Mesenquimal/genética , Histona Desmetilases/metabolismo , Leucemia Mieloide Aguda/patologia , Fatores de Transcrição da Família Snail/fisiologia , Animais , Linhagem Celular Tumoral , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Células HEK293 , Células HL-60 , Histona Desmetilases/genética , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/metabolismo , Camundongos , Camundongos Transgênicos , Ligação Proteica , Fatores de Transcrição da Família Snail/genética , Fatores de Transcrição da Família Snail/metabolismoRESUMO
The transcription factor Hhex (hematopoietically expressed homeobox gene) is critical for development of multiple lymphoid lineages beyond the common lymphoid progenitor. In addition, Hhex regulates hematopoietic stem cell (HSC) self-renewal, emergency hematopoiesis, and acute myeloid leukemia initiation and maintenance. Hhex mediates its effects on HSCs and acute myeloid leukemia stem cells via repression of the Cdkn2a tumor suppressor locus. However, we report here that loss of Cdkn2a does not rescue the failure of lymphoid development caused by loss of Hhex. As loss of Hhex causes apoptosis of lymphoid progenitors associated with impaired Bcl2 expression and defective Stat5b signaling, we tested the effects of rescuing these pathways using transgenic mice. Expression of the anti-apoptotic factor Bcl2, but not activated Stat5, rescued the development of T-, B-, and NK-cell lineages in the absence of Hhex. These results indicate that Bcl2 expression, but not Stat5b signaling or loss of Cdkn2a, can overcome the lymphoid deficiencies caused by the absence of Hhex, suggesting that the primary role of this transcription factor is to promote survival of lymphoid progenitors during early lymphoid development.
Assuntos
Inibidor p16 de Quinase Dependente de Ciclina/imunologia , Proteínas de Homeodomínio/imunologia , Células Progenitoras Linfoides/imunologia , Fator de Transcrição STAT5/imunologia , Transdução de Sinais/imunologia , Fatores de Transcrição/imunologia , Animais , Apoptose/genética , Apoptose/imunologia , Sobrevivência Celular/genética , Sobrevivência Celular/imunologia , Inibidor p16 de Quinase Dependente de Ciclina/genética , Proteínas de Homeodomínio/genética , Células Progenitoras Linfoides/citologia , Camundongos , Camundongos Knockout , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/imunologia , Fator de Transcrição STAT5/genética , Transdução de Sinais/genética , Fatores de Transcrição/genéticaRESUMO
Somatically acquired mutations in PHF6 (plant homeodomain finger 6) frequently occur in hematopoietic malignancies and often coincide with ectopic expression of TLX3. However, there is no functional evidence to demonstrate whether these mutations contribute to tumorigenesis. Similarly, the role of PHF6 in hematopoiesis is unknown. We report here that Phf6 deletion in mice resulted in a reduced number of hematopoietic stem cells (HSCs), an increased number of hematopoietic progenitor cells, and an increased proportion of cycling stem and progenitor cells. Loss of PHF6 caused increased and sustained hematopoietic reconstitution in serial transplantation experiments. Interferon-stimulated gene expression was upregulated in the absence of PHF6 in hematopoietic stem and progenitor cells. The numbers of hematopoietic progenitor cells and cycling hematopoietic stem and progenitor cells were restored to normal by combined loss of PHF6 and the interferon α and ß receptor subunit 1. Ectopic expression of TLX3 alone caused partially penetrant leukemia. TLX3 expression and loss of PHF6 combined caused fully penetrant early-onset leukemia. Our data suggest that PHF6 is a hematopoietic tumor suppressor and is important for fine-tuning hematopoietic stem and progenitor cell homeostasis.
Assuntos
Células-Tronco Hematopoéticas/citologia , Proteínas de Homeodomínio/metabolismo , Leucemia/etiologia , Proteínas Repressoras/fisiologia , Animais , Carcinogênese , Regulação da Expressão Gênica , Humanos , Camundongos , Camundongos Knockout , Receptores de Interferon , Proteínas Repressoras/genética , Proteínas Supressoras de TumorRESUMO
Deregulated activation of the latent transcription factor STAT3 has been implicated in the pathogenesis of myeloproliferative and lymphoproliferative hematologic disorders. The uncontrolled activation of STAT3 has traditionally been assigned to its elevated phosphorylation at tyrosine 705 (pY705) and associated nuclear transcriptional activity. By contrast, a transcriptional role for serine 727 phosphorylation (pS727) of STAT3 has recently emerged, suggesting that pS727 may account for the pathological activity of STAT3 in certain disease settings. Here, by coupling pS727-STAT3-deficient Stat3SA/SA mice with a STAT3-driven mouse model (gp130F/F) for myeloproliferative and lymphoproliferative pathologies, we reveal a key role for pS727-STAT3 in promoting multiple hematologic pathologies. The genetic blockade of pS727-STAT3 in gp130F/F:Stat3SA/SA mice ameliorated the neutrophilia, thrombocytosis, splenomegaly and lymphadenopathy that are features of gp130F/F mice. The protection against thrombocytosis in gp130F/F:Stat3SA/SA mice coincided with normalized megakaryopoiesis in both bone marrow and spleen compartments. Interestingly, pS727-STAT3-mediated abnormal lymphopoiesis in gp130F/F mice was more pronounced in lymph nodes compared to thymus, and was characterized by elevated numbers of B cells at the expense of T cells. Furthermore, pS727-STAT3 dependency for these hematologic pathologies coincided with transcriptional activity on STAT3-regulated genes, rather than its effect on mitochondrial and metabolic genes. Collectively, these findings suggest that pS727 plays a critical pathological role in modulating the transcriptional activity of STAT3 in hematologic disorders.
RESUMO
BACKGROUND: Androgens function through DNA and non-DNA binding-dependent signalling of the androgen receptor (AR). How androgens promote erythropoiesis is not fully understood. DESIGN AND METHODS: To identify the androgen signalling pathway, we treated male mice lacking the second zinc finger of the DNA-binding domain of the AR (ARΔZF2 ) with non-aromatizable 5α-dihydrotestosterone (5α-DHT) or aromatizable testosterone. To distinguish direct hematopoietic and non-hematopoietic mechanisms, we performed bone marrow reconstitution experiments. RESULTS: In wild-type mice, 5α-DHT had greater erythroid activity than testosterone, which can be aromatized to estradiol. The erythroid response in wild-type mice following 5α-DHT treatment was associated with increased serum erythropoietin (EPO) and its downstream target erythroferrone, and hepcidin suppression. 5α-DHT had no erythroid activity in ARΔZF2 mice, proving the importance of DNA binding by the AR. Paradoxically, testosterone, but not 5α-DHT, suppressed EPO levels in ARΔZF2 mice, suggesting testosterone following aromatization may oppose the erythroid-stimulating effects of androgens. Female wild-type mice reconstituted with ARΔZF2 bone marrow cells remained responsive to 5α-DHT. In contrast, ARΔZF2 mice reconstituted with female wild-type bone marrow cells showed no response to 5α-DHT. CONCLUSION: Erythroid promoting effects of androgens are mediated through DNA binding-dependent actions of the AR in non-hematopoietic cells, including stimulating EPO expression.
Assuntos
Androgênios/metabolismo , Proteínas de Ligação a DNA/metabolismo , Eritropoese , Receptores Androgênicos/metabolismo , Androgênios/farmacologia , Animais , Biomarcadores , Eritropoese/efeitos dos fármacos , Eritropoetina/sangue , Feminino , Regulação da Expressão Gênica , Ferro/metabolismo , Masculino , Camundongos , Camundongos Transgênicos , Ligação Proteica , Receptores Androgênicos/genética , Transdução de SinaisRESUMO
Emerging evidence indicates that thymocyte self-renewal induced by progenitor deprivation carries an oncogenic risk that is modulated by intra-thymic competition from differentiation-committed cells. Here we discuss formative studies demonstrating that, in mice, early thymocytes acquire self-renewing potential when thymic progenitor supply is sub-physiological and the importance of cellular competition with this at-risk cell population to prevent lymphoid malignancy. We also consider the possibility that increased thymic residency time, established under conditions of limited cellular competition, may have contributed to oncogenesis observed in early SCID-X1 trials when combined with insertional activation of proto-oncogenes such as LMO2.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Carcinogênese/genética , Proteínas com Domínio LIM/genética , Neoplasias/imunologia , Timócitos/imunologia , Proteínas Adaptadoras de Transdução de Sinal/imunologia , Animais , Carcinogênese/imunologia , Autorrenovação Celular/imunologia , Transformação Celular Neoplásica/imunologia , Modelos Animais de Doenças , Terapia Genética , Células-Tronco Hematopoéticas/imunologia , Humanos , Proteínas com Domínio LIM/imunologia , Camundongos , Neoplasias/genética , Células-Tronco Neoplásicas/imunologiaRESUMO
The hematopoietically expressed homeobox transcription factor (Hhex) is important for the maturation of definitive hematopoietic progenitors and B-cells during development. We have recently shown that in adult hematopoiesis, Hhex is dispensable for maintenance of hematopoietic stem cells (HSCs) and myeloid lineages but essential for the commitment of common lymphoid progenitors (CLPs) to lymphoid lineages. Here, we show that during serial bone marrow transplantation, Hhex-deleted HSCs are progressively lost, revealing an intrinsic defect in HSC self-renewal. Moreover, Hhex-deleted mice show markedly impaired hematopoietic recovery following myeloablation, due to a failure of progenitor expansion. In vitro, Hhex-null blast colonies were incapable of replating, implying a specific requirement for Hhex in immature progenitors. Transcriptome analysis of Hhex-null Lin- Sca+ Kit+ cells showed that Hhex deletion leads to derepression of polycomb repressive complex 2 (PRC2) and PRC1 target genes, including the Cdkn2a locus encoding the tumor suppressors p16Ink 4a and p19Arf . Indeed, loss of Cdkn2a restored the capacity of Hhex-null blast colonies to generate myeloid progenitors in vitro, as well as hematopoietic reconstitution following myeloablation in vivo. Thus, HSCs require Hhex to promote PRC2-mediated Cdkn2a repression to enable continued self-renewal and response to hematopoietic stress. Stem Cells 2017;35:1948-1957.
Assuntos
Autorrenovação Celular , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Hematopoese , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/metabolismo , Proteínas de Homeodomínio/metabolismo , Estresse Fisiológico , Fatores de Transcrição/metabolismo , Animais , Proliferação de Células , Deleção de Genes , Regulação da Expressão Gênica , Transplante de Células-Tronco Hematopoéticas , Camundongos Endogâmicos C57BL , Células Progenitoras Mieloides/citologia , Células Progenitoras Mieloides/metabolismoRESUMO
The hematopoietically expressed homeobox gene, Hhex, is a transcription factor that is important for development of definitive hematopoietic stem cells (HSCs) and B cells, and that causes T-cell leukemia when overexpressed. Here, we have used an Hhex inducible knockout mouse model to study the role of Hhex in adult hematopoiesis. We found that loss of Hhex was tolerated in HSCs and myeloid lineages, but resulted in a progressive loss of B lymphocytes in the circulation. This was accompanied by a complete loss of B-cell progenitors in the bone marrow and of transitional B-cell subsets in the spleen. In addition, transplantation and in vitro culture experiments demonstrated an almost complete failure of Hhex-null HSCs to contribute to lymphoid lineages beyond the common lymphoid precursor stage, including T cells, B cells, NK cells, and dendritic cells. Gene expression analysis of Hhex-deleted progenitors demonstrated deregulated expression of a number of cell cycle regulators. Overexpression of one of these, cyclin D1, could rescue the B-cell developmental potential of Hhex-null lymphoid precursors. Thus, Hhex is a key regulator of early lymphoid development, functioning, at least in part, via regulation of the cell cycle.
Assuntos
Proteínas de Ciclo Celular/genética , Ciclina D1/genética , Hematopoese/genética , Proteínas de Homeodomínio/genética , Linfopoese/genética , Células Precursoras de Linfócitos B/patologia , Fatores de Transcrição/genética , Animais , Células da Medula Óssea/imunologia , Células da Medula Óssea/patologia , Proteínas de Ciclo Celular/imunologia , Diferenciação Celular , Proliferação de Células , Ciclina D1/imunologia , Células Dendríticas/imunologia , Células Dendríticas/patologia , Deleção de Genes , Regulação da Expressão Gênica , Teste de Complementação Genética , Hematopoese/imunologia , Células-Tronco Hematopoéticas/imunologia , Células-Tronco Hematopoéticas/patologia , Proteínas de Homeodomínio/imunologia , Células Matadoras Naturais/imunologia , Células Matadoras Naturais/patologia , Contagem de Linfócitos , Depleção Linfocítica , Linfopoese/imunologia , Camundongos , Camundongos Knockout , Células Precursoras de Linfócitos B/imunologia , Baço/imunologia , Baço/patologia , Linfócitos T/imunologia , Linfócitos T/patologia , Fatores de Transcrição/deficiência , Fatores de Transcrição/imunologia , Transcrição GênicaRESUMO
Lmo2 is an oncogenic transcription factor that is frequently overexpressed in T-cell acute lymphoblastic leukemia (T-ALL), including early T-cell precursor ALL (ETP-ALL) cases with poor prognosis. Lmo2 must be recruited to DNA by binding to the hematopoietic basic helix-loop-helix factors Scl/Tal1 or Lyl1. However, it is unknown which of these factors can mediate the leukemic activity of Lmo2. To address this, we have generated Lmo2-transgenic mice lacking either Scl or Lyl1 in the thymus. We show that although Scl is dispensable for Lmo2-driven leukemia, Lyl1 is critical for all oncogenic functions of Lmo2, including upregulation of a stem cell-like gene signature, aberrant self-renewal of thymocytes, and subsequent generation of T-cell leukemia. Lyl1 expression is restricted to preleukemic and leukemic stem cell populations in this model, providing a molecular explanation for the stage-specific expression of the Lmo2-induced gene expression program. Moreover, LMO2 and LYL1 are coexpressed in ETP-ALL patient samples, and LYL1 is required for growth of ETP-ALL cell lines. Thus, the LMO2-LYL1 interaction is a promising therapeutic target for inhibiting self-renewing cancer stem cells in T-ALL, including poor-prognosis ETP-ALL cases.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Proteínas com Domínio LIM/genética , Proteínas de Neoplasias/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Diferenciação Celular/genética , Linhagem Celular Tumoral , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Análise por Conglomerados , Perfilação da Expressão Gênica , Regulação Leucêmica da Expressão Gênica , Humanos , Proteínas com Domínio LIM/metabolismo , Camundongos , Camundongos Transgênicos , Proteínas de Neoplasias/metabolismo , Células-Tronco Neoplásicas/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/mortalidade , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteína 1 de Leucemia Linfocítica Aguda de Células T , Linfócitos T/citologia , Linfócitos T/metabolismo , Timócitos/metabolismo , Timócitos/patologiaRESUMO
The Haematopoietically expressed homeobox transcription factor (Hhex) is a transcriptional repressor that is of fundamental importance across species, as evident by its evolutionary conservation spanning fish, amphibians, birds, mice and humans. Indeed, Hhex maintains its vital functions throughout the lifespan of the organism, beginning in the oocyte, through fundamental stages of embryogenesis in the foregut endoderm. The endodermal development driven by Hhex gives rise to endocrine organs such as the pancreas in a process which is likely linked to its role as a risk factor in diabetes and pancreatic disorders. Hhex is also required for the normal development of the bile duct and liver, the latter also importantly being the initial site of haematopoiesis. These haematopoietic origins are governed by Hhex, leading to its crucial later roles in definitive haematopoietic stem cell (HSC) self-renewal, lymphopoiesis and haematological malignancy. Hhex is also necessary for the developing forebrain and thyroid gland, with this reliance on Hhex evident in its role in endocrine disorders later in life including a potential role in Alzheimer's disease. Thus, the roles of Hhex in embryological development throughout evolution appear to be linked to its later roles in a variety of disease processes.
Assuntos
Genes Homeobox , Fatores de Transcrição , Humanos , Animais , Camundongos , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Regulação da Expressão Gênica , Fígado/metabolismo , Sistema Digestório/metabolismoRESUMO
Cell competition has recently emerged as an important tumor suppressor mechanism in the thymus that inhibits autonomous thymic maintenance. Here, we show that the oncogenic transcription factor Lmo2 causes autonomous thymic maintenance in transgenic mice by inhibiting early T cell differentiation. This autonomous thymic maintenance results in the development of self-renewing preleukemic stem cells (pre-LSCs) and subsequent leukemogenesis, both of which are profoundly inhibited by restoration of thymic competition or expression of the antiapoptotic factor BCL2. Genomic analyses revealed the presence of Notch1 mutations in pre-LSCs before subsequent loss of tumor suppressors promotes the transition to overt leukemogenesis. These studies demonstrate a critical role for impaired cell competition in the development of pre-LSCs in a transgenic mouse model of T cell acute lymphoblastic leukemia (T-ALL), implying that this process plays a role in the ontogeny of human T-ALL.
Assuntos
Leucemia-Linfoma Linfoblástico de Células T Precursoras , Timócitos , Camundongos , Humanos , Animais , Timócitos/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Fatores de Transcrição/metabolismo , Camundongos Transgênicos , Carcinogênese/patologia , Proteínas com Domínio LIM/genética , Proteínas com Domínio LIM/metabolismo , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismoRESUMO
Hedgehog (Hh) ligands bind to the Patched1 (Ptch1) receptor, relieving repression of Smoothened, which leads to activation of the Hh signaling pathway. Using conditional Ptch1 knockout mice, the aim of this study was to determine the effects of activating the Hh signaling pathway in hematopoiesis. Surprisingly, hematopoietic-specific deletion of Ptch1 did not lead to activation of the Hh signaling pathway and, consequently, had no phenotypic effect. In contrast, deletion of Ptch1 in nonhematopoietic cells produced 2 distinct hematopoietic phenotypes. First, activation of Hh signaling in epithelial cells led to apoptosis of lymphoid progenitors associated with markedly elevated levels of circulating thymic stromal lymphopoietin. Second, activation of Hh signaling in the bone marrow cell niche led to increased numbers of lineage-negative c-kit(+) Sca-1(+) bone marrow cells and mobilization of myeloid progenitors associated with a marked loss of osteoblasts. Thus, deletion of Ptch1 leads to hematopoietic effects by distinct cell-extrinsic mechanisms rather than by direct activation of the Hh signaling pathway in hematopoietic cells. These findings have important implications for therapeutics designed to activate the Hh signaling pathway in hematopoietic cells including hematopoietic stem cells.
Assuntos
Proteínas Hedgehog/fisiologia , Linfócitos/citologia , Linfopoese/fisiologia , Células Mieloides/citologia , Mielopoese/fisiologia , Receptores de Superfície Celular/fisiologia , Receptores Acoplados a Proteínas G/fisiologia , Animais , Transplante de Medula Óssea , Linhagem da Célula , Citocinas/sangue , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Fatores de Transcrição Kruppel-Like/biossíntese , Fatores de Transcrição Kruppel-Like/genética , Fatores de Transcrição Kruppel-Like/fisiologia , Linfócitos/metabolismo , Linfopoese/genética , Masculino , Camundongos , Camundongos Congênicos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Células Mieloides/metabolismo , Mielopoese/genética , Osteoblastos/citologia , Receptores Patched , Receptor Patched-1 , Quimera por Radiação , Receptores de Superfície Celular/deficiência , Receptores de Superfície Celular/genética , Receptores Acoplados a Proteínas G/biossíntese , Receptores Acoplados a Proteínas G/genética , Receptor Smoothened , Linfopoietina do Estroma do TimoRESUMO
Insights into the role of ankyrin-1 (ANK-1) in the formation and stabilization of the red cell cytoskeleton have come from studies on the nb/nb mice, which carry hypomorphic alleles of Ank-1. Here, we revise several paradigms established in the nb/nb mice through analysis of an N-ethyl-N-nitrosourea (ENU)-induced Ank-1-null mouse. Mice homozygous for the Ank-1 mutation are profoundly anemic in utero and most die perinatally, indicating that Ank-1 plays a nonredundant role in erythroid development. The surviving pups exhibit features of severe hereditary spherocytosis (HS), with marked hemolysis, jaundice, compensatory extramedullary erythropoiesis, and tissue iron overload. Red cell membrane analysis reveals a complete loss of ANK-1 protein and a marked reduction in beta-spectrin. As a consequence, the red cells exhibit total disruption of cytoskeletal architecture and severely altered hemorheologic properties. Heterozygous mutant mice, which have wild-type levels of ANK-1 and spectrin in their RBC membranes and normal red cell survival and ultrastructure, exhibit profound resistance to malaria, which is not due to impaired parasite entry into RBC. These findings provide novel insights into the role of Ank-1, and define an ideal model for the study of HS and malarial resistance.
Assuntos
Anquirinas/fisiologia , Células Eritroides/metabolismo , Etilnitrosoureia , Neoplasias Hematológicas/induzido quimicamente , Neoplasias Hematológicas/genética , Animais , Animais Recém-Nascidos , Anquirinas/genética , Anquirinas/metabolismo , Sequência de Bases , Carcinógenos , Citoesqueleto/genética , Citoesqueleto/patologia , Análise Mutacional de DNA , Eritrócitos/efeitos dos fármacos , Eritrócitos/patologia , Eritrócitos Anormais/patologia , Eritropoese/genética , Eritropoese/fisiologia , Neoplasias Hematológicas/patologia , Hemólise/efeitos dos fármacos , Hemólise/genética , Malária/genética , Malária/veterinária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Dados de Sequência MolecularRESUMO
The majority of cases of T-cell acute lymphoblastic leukemia (T-ALL) contain chromosomal abnormalities that drive overexpression of oncogenic transcription factors. However, whether these initiating oncogenes are required for leukemia maintenance is poorly understood. To address this, we developed a tetracycline-regulated mouse model of T-ALL driven by the oncogenic transcription factor Lmo2. This revealed that whilst thymus-resident pre-Leukemic Stem Cells (pre-LSCs) required continuous Lmo2 expression, the majority of leukemias relapsed despite Lmo2 withdrawal. Relapse was associated with a mature phenotype and frequent mutation or loss of tumor suppressor genes including Ikzf1 (Ikaros), with targeted deletion Ikzf1 being sufficient to transform Lmo2-dependent leukemias to Lmo2-independence. Moreover, we found that the related transcription factor TAL1 was dispensable in several human T-ALL cell lines that contain SIL-TAL1 chromosomal deletions driving its overexpression, indicating that evolution to oncogene independence can also occur in human T-ALL. Together these results indicate an evolution of oncogene addiction in murine and human T-ALL and show that loss of Ikaros is a mechanism that can promote self-renewal of T-ALL lymphoblasts in the absence of an initiating oncogenic transcription factor.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Regulação Leucêmica da Expressão Gênica , Fator de Transcrição Ikaros/fisiologia , Proteínas com Domínio LIM/fisiologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Animais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Oncogenes , Leucemia-Linfoma Linfoblástico de Células T Precursoras/etiologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismoRESUMO
Hhex encodes a homeobox transcriptional regulator important for embryonic development and hematopoiesis. Hhex is highly expressed in NK cells, and its germline deletion results in significant defects in lymphoid development, including NK cells. To determine if Hhex is intrinsically required throughout NK cell development or for NK cell function, we generate mice that specifically lack Hhex in NK cells. NK cell frequency is dramatically reduced, while NK cell differentiation, IL-15 responsiveness, and function at the cellular level remain largely normal in the absence of Hhex. Increased IL-15 availability fails to fully reverse NK lymphopenia following conditional Hhex deletion, suggesting that Hhex regulates developmental pathways extrinsic to those dependent on IL-15. Gene expression and functional genetic approaches reveal that Hhex regulates NK cell survival by directly binding Bcl2l11 (Bim) and repressing expression of this key apoptotic mediator. These data implicate Hhex as a transcriptional regulator of NK cell homeostasis and immunity.
Assuntos
Proteínas de Homeodomínio/metabolismo , Células Matadoras Naturais/metabolismo , Fatores de Transcrição/metabolismo , Animais , Apoptose/genética , Diferenciação Celular/fisiologia , Proliferação de Células/fisiologia , Sobrevivência Celular/fisiologia , Feminino , Regulação da Expressão Gênica/genética , Hematopoese/genética , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/fisiologia , Interleucina-15/genética , Interleucina-15/imunologia , Células Matadoras Naturais/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Transdução de Sinais/fisiologia , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologiaRESUMO
T cell acute lymphoblastic leukaemia (T-ALL) cases include subfamilies that overexpress the TAL1/LMO, TLX1/3 and HOXA transcription factor oncogenes. While it has been shown that TAL1/LMO transcription factors induce self-renewal of thymocytes, whether this is true for other transcription factor oncogenes is unknown. To address this, we have studied NUP98-HOXD13-transgenic (NHD13-Tg) mice, which overexpress HOXA transcription factors throughout haematopoiesis and develop both myelodysplastic syndrome (MDS) progressing to acute myeloid leukaemia (AML) as well as T-ALL. We find that thymocytes from preleukaemic NHD13-Tg mice can serially transplant, demonstrating that they have self-renewal capacity. Transcriptome analysis shows that NHD13-Tg thymocytes exhibit a stem cell-like transcriptional programme closely resembling that induced by Lmo2, including Lmo2 itself and its critical cofactor Lyl1. To determine whether Lmo2/Lyl1 are required for NHD13-induced thymocyte self-renewal, NHD13-Tg mice were crossed with Lyl1 knockout mice. This showed that Lyl1 is essential for expression of the stem cell-like gene expression programme in thymocytes and self-renewal. Surprisingly however, NHD13 transgenic mice lacking Lyl1 showed accelerated T-ALL and absence of transformation to AML, associated with a loss of multipotent progenitors in the bone marrow. Thus multiple T cell oncogenes induce thymocyte self-renewal via Lmo2/Lyl1; however, NHD13 can also promote T-ALL via an alternative pathway.