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ABSTRACT: Previous studies have shown that mouse bone marrow cells can produce mast cells when stimulated in vitro by stem cell factor (SCF) and interleukin-3 (IL-3). Experiments to define the marrow cells able to generate mast cells showed that the most active subpopulations were the Kit(+) Sca1(-) progenitor cell fraction and the more ancestral Kit(+) Sca1(+) blast colony-forming cell fraction. In clonal cultures, up to 64% of blast colony-forming cells were able to generate mast cells when stimulated by SCF and IL-3, and, of these, the most active were those in the CD34(-) Flt3R(-) long-term repopulating cell fraction. Basophils, identified by the monoclonal antibody mMCP-8 to mouse mast cell serine protease-8, were also produced by 50% of blast colony-forming cells with a strong concordance in the production of both cell types by individual blast colony-forming cells. Enriched populations of marrow-derived basophils were shown to generate variable numbers of mast cells after a further incubation with SCF and IL-3. The data extend the repertoire of lineage-committed cells able to be produced by multipotential hematopoietic blast colony-forming cells and show that basophils and mast cells can have common ancestral cells and that basophils can probably generate mast cells at least under defined in vitro conditions.
Proceedings of the National Academy of Sciences 05/2013; · 9.68 Impact Factor
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ABSTRACT: Previous studies have shown that mouse bone marrow cells can produce mast cells when stimulated in vitro by stem cell factor (SCF) and interleukin-3 (IL-3). Experiments to define the marrow cells able to generate mast cells showed that the most active subpopulations were the Kit + Sca1 – progenitor cell fraction and the more ancestral Kit + Sca1 + blast colony-forming cell fraction. In clonal cultures, up to 64% of blast colony-forming cells were able to generate mast cells when stimulated by SCF and IL-3, and, of these, the most active were those in the CD34 – Flt3R – long-term repopulating cell fraction. Basophils, identified by the monoclonal antibody mMCP-8 to mouse mast cell serine protease-8, were also produced by 50% of blast colony-forming cells with a strong con-cordance in the production of both cell types by individual blast colony-forming cells. Enriched populations of marrow-derived basophils were shown to generate variable numbers of mast cells after a further incubation with SCF and IL-3. The data extend the repertoire of lineage-committed cells able to be produced by mul-tipotential hematopoietic blast colony-forming cells and show that basophils and mast cells can have common ancestral cells and that basophils can probably generate mast cells at least under defined in vitro conditions.
Proceedings of the National Academy of Sciences 04/2013; · 9.68 Impact Factor
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Jian Zhong Tang,
Catherine L Carmichael,
Wei Shi, Donald Metcalf,
Ashley P Ng,
Craig D Hyland,
Nancy A Jenkins,
Neal G Copeland,
Viive M Howell,
Zhizhuang Joe Zhao,
Gordon K Smyth,
Benjamin T Kile,
Warren S Alexander
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ABSTRACT: To define genetic lesions driving leukemia, we targeted cre-dependent Sleeping Beauty (SB) transposon mutagenesis to the blood-forming system using a hematopoietic-selective vav 1 oncogene (vav1) promoter. Leukemias of diverse lineages ensued, most commonly lymphoid leukemia and erythroleukemia. The inclusion of a transgenic allele of Janus kinase 2 (JAK2)V617F resulted in acceleration of transposon-driven disease and strong selection for erythroleukemic pathology with transformation of bipotential erythro-megakaryocytic cells. The genes encoding the E-twenty-six (ETS) transcription factors Ets related gene (Erg) and Ets1 were the most common sites for transposon insertion in SB-induced JAK2V617F-positive erythroleukemias, present in 87.5% and 65%, respectively, of independent leukemias examined. The role of activated Erg was validated by reproducing erythroleukemic pathology in mice transplanted with fetal liver cells expressing translocated in liposarcoma (TLS)-ERG, an activated form of ERG found in human leukemia. Via application of SB mutagenesis to TLS-ERG-induced erythroid transformation, we identified multiple loci as likely collaborators with activation of Erg. Jak2 was identified as a common transposon insertion site in TLS-ERG-induced disease, strongly validating the cooperation between JAK2V617F and transposon insertion at the Erg locus in the JAK2V617F-positive leukemias. Moreover, loci expressing other regulators of signal transduction pathways were conspicuous among the common transposon insertion sites in TLS-ERG-driven leukemia, suggesting that a key mechanism in erythroleukemia may be the collaboration of lesions disturbing erythroid maturation, most notably in genes of the ETS family, with mutations that reduce dependence on exogenous signals.
Proceedings of the National Academy of Sciences 03/2013; · 9.68 Impact Factor
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Shalin H Naik,
Priyanka Sathe,
Hae-Young Park, Donald Metcalf,
Anna I Proietto,
Aleksander Dakic,
Sebastian Carotta,
Meredith O'Keeffe,
Melanie Bahlo,
Anthony Papenfuss,
Jong-Young Kwak,
Li Wu,
Ken Shortman
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Seth L Masters,
Motti Gerlic, Donald Metcalf,
Simon Preston,
Marc Pellegrini,
Joanne A O'Donnell,
Kate McArthur,
Tracey M Baldwin,
Stephane Chevrier,
Cameron J Nowell,
Louise H Cengia,
Katya J Henley,
Janelle E Collinge,
Daniel L Kastner,
Lionel Feigenbaum,
Douglas J Hilton,
Warren S Alexander,
Benjamin T Kile,
Ben A Croker
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ABSTRACT: Cytopenias are key prognostic indicators of life-threatening infection, contributing to immunosuppression and mortality. Here we define a role for Caspase-1-dependent death, known as pyroptosis, in infection-induced cytopenias by studying inflammasome activation in hematopoietic progenitor cells. The NLRP1a inflammasome is expressed in hematopoietic progenitor cells and its activation triggers their pyroptotic death. Active NLRP1a induced a lethal systemic inflammatory disease that was driven by Caspase-1 and IL-1β but was independent of apoptosis-associated speck-like protein containing a CARD (ASC) and ameliorated by IL-18. Surprisingly, in the absence of IL-1β-driven inflammation, active NLRP1a triggered pyroptosis of hematopoietic progenitor cells resulting in leukopenia at steady state. During periods of hematopoietic stress induced by chemotherapy or lymphocytic choriomeningitis virus (LCMV) infection, active NLRP1a caused prolonged cytopenia, bone marrow hypoplasia, and immunosuppression. Conversely, NLRP1-deficient mice showed enhanced recovery from chemotherapy and LCMV infection, demonstrating that NLRP1 acts as a cellular sentinel to alert Caspase-1 to hematopoietic and infectious stress.
Immunity 12/2012; · 21.64 Impact Factor
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ABSTRACT: The transcription factor encoded by the E-twenty-six (ETS)-related gene, ERG, is an essential regulator of hematopoietic stem cell function and a potent human oncoprotein. Enforced expression of ERG
in murine hematopoietic cells leads to the development of a well-characterized lymphoid leukemia and a less well-defined non
lymphoid disease. To clarify the latter, we generated murine bone marrow chimeras with enforced Erg expression in engrafted
hematopoietic progenitor cells. As expected, these mice developed lymphoid leukemia. However, the previously reported non
lymphoid disease that developed was shown to be a uniform, transplantable leukemia with both erythroid and megakaryocytic
characteristics. In vivo, this disease had the overall appearance of an erythroleukemia, with an accumulation of immature
erythroblasts that infiltrated the bone marrow, spleen, liver, and lung. However, when stimulated in vitro, leukemic cell
clones exhibited both erythroid and megakaryocytic differentiation, suggesting that transformation occurred in a bipotential
progenitor. Thus, in mice, Erg overexpression induces the development of not only lymphoid leukemia but also erythro-megakaryocytic
leukemia.
Proceedings of the National Academy of Sciences 09/2012; 109(38):15437-15442. · 9.68 Impact Factor
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Marlyse A Debrincat,
Emma C Josefsson,
Chloé James,
Katya J Henley,
Sarah Ellis,
Marion Lebois,
Kelly L Betterman,
Rachael M Lane,
Kelly L Rogers,
Michael J White,
Andrew W Roberts,
Natasha L Harvey, Donald Metcalf,
Benjamin T Kile
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ABSTRACT: Mature megakaryocytes depend on the function of Bcl-x(L), a member of the Bcl-2 family of prosurvival proteins, to proceed safely through the process of platelet shedding. Despite this, loss of Bcl-x(L) does not prevent the growth and maturation of megakaryocytes, suggesting redundancy with other prosurvival proteins. We therefore generated mice with a megakaryocyte-specific deletion of Mcl-1, which is known to be expressed in megakaryocytes. Megakaryopoiesis, platelet production, and platelet lifespan were unperturbed in Mcl-1(Pf4Δ/Pf4Δ) animals. However, treatment with ABT-737, a BH3 mimetic compound that inhibits the prosurvival proteins Bcl-2, Bcl-x(L), and Bcl-w resulted in the complete ablation of megakaryocytes and platelets. Genetic deletion of both Mcl-1 and Bcl-x(L) in megakaryocytes resulted in preweaning lethality. Megakaryopoiesis in Bcl-x(Pf4Δ/Pf4Δ) Mcl-1(Pf4Δ/Pf4Δ) embryos was severely compromised, and these animals exhibited ectopic bleeding. Our studies indicate that the combination of Bcl-x(L) and Mcl-1 is essential for the viability of the megakaryocyte lineage.
Blood 02/2012; 119(24):5850-8. · 9.90 Impact Factor
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ABSTRACT: Hematopoietic progenitor cells are the progeny of hematopoietic stem cells that coordinate the production of precise numbers of mature blood cells of diverse functional lineages. Identification of cell-surface antigen expression associated with hematopoietic lineage restriction has allowed prospective isolation of progenitor cells with defined hematopoietic potential. To clarify further the cellular origins of megakaryocyte commitment, we assessed the in vitro and in vivo megakaryocyte and platelet potential of defined progenitor populations in the adult mouse bone marrow. We show that megakaryocytes arise from CD150(+) bipotential progenitors that display both platelet- and erythrocyte-producing potential in vivo and that can develop from the Flt3(-) fraction of the pregranulocyte-macrophage population. We define a bipotential erythroid-megakaryocyte progenitor population, the CD150(+)CD9(lo)endoglin(lo) fraction of Lin(-)cKit(+)IL7 receptor alpha(-)FcγRII/III(lo)Sca1(-) cells, which contains the bulk of the megakaryocyte colony-forming capacity of the bone marrow, including bipotential megakaryocyte-erythroid colony-forming capacity, and can generate both erythrocytes and platelets efficiently in vivo. This fraction is distinct from the CD150(+)CD9(hi)endoglin(lo) fraction, which contains bipotential precursors with characteristics of increased megakaryocytic maturation, and the CD150(+)CD9(lo)endoglin(hi) fraction, which contains erythroid lineage-committed cells. Finally, we demonstrate that bipotential erythroid-megakaryocyte progenitor and CD150(+)CD9(hi)endoglin(lo) cells are TPO-responsive and that the latter population specifically expands in the recovery from thrombocytopenia induced by anti-platelet serum.
Proceedings of the National Academy of Sciences 02/2012; 109(7):2364-9. · 9.68 Impact Factor
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ABSTRACT: Diverse mutations in the genes encoding hemoglobin (Hb) have been characterized in human disease. We describe here a mutation in the mouse Hbb-b2 gene, denoted Plt12, that precisely mimics the human hemoglobin Hotel Dieu variant. The mutation results in increased affinity of Hb for oxygen and Plt12 mutant mice exhibited reduced partial pressure of O(2) in the blood, accompanied by erythrocytosis characterized by elevated erythropoietin levels and splenomegaly with excess erythropoiesis. Most homozygous Hbb-b2(Plt12/Plt12) mice succumbed to early lethality associated with emphysema, cardiac abnormalities, and liver degeneration. Survivors displayed a marked thrombocytopenia without significant deficiencies in the numbers of megakaryocytes or megakaryocyte progenitor cells. The lifespan of platelets in the circulation of Hbb-b2(Plt12/Plt12) mice was normal, and splenectomy did not correct the thrombocytopenia, suggesting that increased sequestration was unlikely to be a major contributor. These data, together with the observation that megakaryocytes in Hbb-b2(Plt12/Plt12) mice appeared smaller and deficient in cytoplasm, support a model in which hypoxia causes thrombocytopenia as a consequence of an inability of megakaryocytes, once formed, to properly mature and produce sufficient platelets. The Plt12 mouse is a model of high O(2)-affinity hemoglobinopathy and provides insights into hematopoiesis under conditions of chronic hypoxia.
Proceedings of the National Academy of Sciences 12/2011; 109(2):576-81. · 9.68 Impact Factor
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ABSTRACT: The lamin B receptor (LBR) is a highly unusual inner nuclear membrane protein with multiple functions. Reduced levels are associated with decreased neutrophil lobularity, whereas complete absence of LBR results in severe skeletal dysplasia and in utero/perinatal lethality. We describe a mouse pedigree, Lym3, with normal bone marrow and thymic development but profound and progressive lymphopenia particularly within the T cell compartment. This defect arises from a point mutation within the Lbr gene with only trace mutant protein detectable in homozygotes, albeit sufficient for normal development. Reduced T cell homeostatic proliferative potential and life span in vivo were found to contribute to lymphopenia. To investigate the role of LBR in gene silencing in hematopoietic cells, we examined gene expression in wild-type and mutant lymph node CD8 T cells and bone marrow neutrophils. Although LBR deficiency had a very mild impact on gene expression overall, for common genes differentially expressed in both LBR-deficient CD8 T cells and neutrophils, gene upregulation prevailed, supporting a role for LBR in their suppression. In summary, this study demonstrates that LBR deficiency affects not only nuclear architecture but also proliferation, cell viability, and gene expression of hematopoietic cells.
The Journal of Immunology 11/2011; 188(1):122-34. · 5.79 Impact Factor
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Emma C Josefsson,
Chloé James,
Katya J Henley,
Marlyse A Debrincat,
Kelly L Rogers,
Mark R Dowling,
Michael J White,
Elizabeth A Kruse,
Rachael M Lane,
Sarah Ellis,
Paquita Nurden,
Kylie D Mason,
Lorraine A O'Reilly,
Andrew W Roberts, Donald Metcalf,
David C S Huang,
Benjamin T Kile
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ABSTRACT: It is believed that megakaryocytes undergo a specialized form of apoptosis to shed platelets. Conversely, a range of pathophysiological insults, including chemotherapy, are thought to cause thrombocytopenia by inducing the apoptotic death of megakaryocytes and their progenitors. To resolve this paradox, we generated mice with hematopoietic- or megakaryocyte-specific deletions of the essential mediators of apoptosis, Bak and Bax. We found that platelet production was unperturbed. In stark contrast, deletion of the prosurvival protein Bcl-x(L) resulted in megakaryocyte apoptosis and a failure of platelet shedding. This could be rescued by deletion of Bak and Bax. We examined the effect on megakaryocytes of three agents that activate the intrinsic apoptosis pathway in other cell types: etoposide, staurosporine, and the BH3 mimetic ABT-737. All three triggered mitochondrial damage, caspase activation, and cell death. Deletion of Bak and Bax rendered megakaryocytes resistant to etoposide and ABT-737. In vivo, mice with a Bak(-/-) Bax(-/-) hematopoietic system were protected against thrombocytopenia induced by the chemotherapeutic agent carboplatin. Thus, megakaryocytes do not activate the intrinsic pathway to generate platelets; rather, the opposite is true: they must restrain it to survive and progress safely through proplatelet formation and platelet shedding.
Journal of Experimental Medicine 09/2011; 208(10):2017-31. · 13.85 Impact Factor
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Ben A Croker,
Joanne A O'Donnell,
Cameron J Nowell, Donald Metcalf,
Grant Dewson,
Kirsteen J Campbell,
Kelly L Rogers,
Yifang Hu,
Gordon K Smyth,
Jian-Guo Zhang,
Michael White,
Kurt Lackovic,
Louise H Cengia,
Lorraine A O'Reilly,
Philippe Bouillet,
Suzanne Cory,
Andreas Strasser,
Andrew W Roberts
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ABSTRACT: During immune responses, neutrophils must integrate survival and death signals from multiple sources to regulate their lifespan. Signals that activate either the Bcl-2- or death receptor-regulated apoptosis pathways can provide powerful stimuli for neutrophils to undergo cell death, but whether they act cooperatively in parallel or directly cross-talk in neutrophils is not known. Previous studies suggested that Bcl-2 family proteins are not required for Fas-induced cell death in neutrophils, but did not examine whether they could modulate its rapid onset. By monitoring the rate of change in neutrophil viability associated with activation of the Fas-triggered death receptor pathway using real-time cell imaging, we show that the Bcl-2-related proteins Bid, Bax, and Bak accelerate neutrophil apoptosis but are not essential for cell death. Increased Bcl-2 or Mcl-1 expression prevents efficient induction of apoptosis by Fas stimulation indicating that the Bcl-2-regulated apoptosis pathway can directly interfere with Fas-triggered apoptosis. Fas has been shown to initiate NFκB activation and gene transcription in cell lines, however gene transcription is not altered in Fas-activated Bid(-/-) neutrophils, indicating that apoptosis occurs independently of gene transcription in neutrophils. The specification of kinetics of neutrophil apoptosis by Bid impacts on the magnitude of neutrophil IL-1β production, implicating a functional role for the Bcl-2-regulated pathway in controlling neutrophil responses to FasL. These data demonstrate that the intrinsic apoptosis pathway directly controls the kinetics of Fas-triggered apoptosis in neutrophils.
Proceedings of the National Academy of Sciences 08/2011; 108(32):13135-40. · 9.68 Impact Factor
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ABSTRACT: Hematopoietic stem cells (HSCs) are rare residents of the bone marrow responsible for the lifelong production of blood cells. Regulation of the balance between HSC self-renewal and differentiation is central to hematopoiesis, allowing precisely regulated generation of mature blood cells at steady state and expanded production at times of rapid need, as well as maintaining ongoing stem cell capacity. Erg, a member of the Ets family of transcription factors, is deregulated in cancers; and although Erg is known to be required for regulation of adult HSCs, its precise role has not been defined. We show here that, although heterozygosity for functional Erg is sufficient for adequate steady-state HSC maintenance, Erg(+/Mld2) mutant mice exhibit impaired HSC self-renewal after bone marrow transplantation or during recovery from myelotoxic stress. Moreover, although mice functionally compromised for either Erg or Mpl, the receptor for thrombopoietin, a key regulator of HSC quiescence, maintained sufficient HSC activity to sustain hematopoiesis, Mpl(-/-) Erg(+/Mld2) compound mutant mice displayed exacerbated stem cell deficiencies and bone marrow failure. Thus, Erg is a critical regulator of adult HSCs, essential for maintaining self-renewal at times of high HSC cycling.
Blood 06/2011; 118(9):2454-61. · 9.90 Impact Factor
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ABSTRACT: Thrombopoietin (TPO) is the cytokine that is chiefly responsible for megakaryocyte production but increasingly attention has turned to its role in maintaining hematopoietic stem cells (HSCs). HSCs are required to initiate the production of all mature hematopoietic cells, but this differentiation needs to be balanced against self-renewal and quiescence to maintain the stem cell pool throughout life. TPO has been shown to support HSC quiescence during adult hematopoiesis, with the loss of TPO signaling associated with bone marrow failure and thrombocytopenia. Recent studies have shown that constitutive activation mutations in Mpl contribute to myeloproliferative disease. In this review, we will discuss TPO signaling pathways, regulation of TPO levels and the role of TPO in normal hematopoiesis and during myeloproliferative disease.
Cell cycle (Georgetown, Tex.) 05/2011; 10(10):1582-9. · 5.36 Impact Factor
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Ben A Croker,
Hiu Kiu,
Marc Pellegrini,
Jesse Toe,
Simon Preston, Donald Metcalf,
Joanne A O'Donnell,
Louise H Cengia,
Kate McArthur,
Nicos A Nicola,
Warren S Alexander,
Andrew W Roberts
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ABSTRACT: The lack of expression of the suppressor of cytokine signalling-3 (SOCS3) or inactivation of the negative regulatory capacity of SOCS3 has been well documented in rheumatoid arthritis, viral hepatitis and cancer. The specific qualitative and quantitative consequences of SOCS3 deficiency on interleukin-6 (IL-6)-mediated pro- and anti-inflammatory responses remain controversial in vitro and unknown in vivo. Mice with a conditional deletion of SOCS3 in hematopoietic cells develop lethal inflammatory disease during adult life and develop gross histopathological changes during experimental arthritis, typified by elevated IL-6 levels. To clarify the nature of the IL-6 responses in vivo, we generated mice deficient in SOCS3 (SOCS3(-/Δvav)) or both SOCS3 and IL-6 (IL-6(-/-)/SOCS3(-/Δvav)), and examined responses in models of acute and chronic inflammation. Acute responses to IL-1β were lethal to SOCS3(-/Δvav) mice but not IL-6(-/-)/SOCS3(-/Δvav) mice, indicating that IL-6 was required for the lethal inflammation induced by IL-1β. Administration of IL-1β to SOCS3(-/Δvav) mice induced systemic apoptosis of lymphocytes in the thymus, spleen and lymph nodes that was dependent on the presence of IL-6. IL-6 deficiency prolonged survival of SOCS3(-/Δvav) mice and ameliorated spontaneous inflammatory disease developing during adult life. Infection of SOCS3(-/Δvav) mice with LCMV induced a lethal inflammatory response that was dependent on IL-6, despite SOCS3(-/Δvav) mice controlling viral replication. We conclude that SOCS3 is required for survival during inflammatory responses and is a critical regulator of IL-6 in vivo.
Immunology and Cell Biology 04/2011; 90(1):124-9. · 3.66 Impact Factor
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ABSTRACT: The regulation of neutrophil recruitment, activation, and disposal is pivotal for circumscribed inflammation. SHP1(Y208N/Y208N) mutant mice develop severe cutaneous inflammatory disease that is IL-1R dependent. Genetic reduction in neutrophil numbers and neutrophilic responses to infection is sufficient to prevent the spontaneous initiation of this disease. Neutrophils from SHP1(Y208N/Y208N) mice display increased pro-IL-1β production due to altered responses to MyD88-dependent and MyD88-independent signals. The IL-1R-dependent inflammatory disease in SHP1(Y208N/Y208N) mice develops independently of caspase 1 and proteinase 3 and neutrophil elastase. In response to Fas ligand, a caspase 1-independent inducer of IL-1β production, neutrophils from SHP1(Y208N/Y208N) mice produce elevated levels of IL-1β but display reduced caspase 3 and caspase 7 activation. In neutrophils deficient in SHP1, IL-1β induces high levels of pro-IL-1β suggesting the presence of a paracrine IL-1β loop. These data indicate that the neutrophil- and IL-1-dependent disease in SHP1(Y208N/Y208N) mice is a consequence of loss of negative regulation of TLR and IL-1R signaling.
The Journal of Immunology 01/2011; 186(2):1131-9. · 5.79 Impact Factor
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Ellen Menkhorst,
Jian-Guo Zhang,
Natalie A Sims,
Phillip O Morgan,
Priscilla Soo,
Ingrid J Poulton, Donald Metcalf,
Estella Alexandrou,
Melissa Gresle,
Lois A Salamonsen,
Helmut Butzkueven,
Nicos A Nicola,
Evdokia Dimitriadis
[show abstract]
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ABSTRACT: Female-controlled contraception/HIV prevention is critical to address health issues associated with gender inequality. Therefore, a contraceptive which can be administered in tandem with a microbicide to inhibit sexually transmitted infections, is desirable. Uterine leukemia inhibitory factor (LIF) is obligatory for blastocyst implantation in mice and associated with infertility in women. We aimed to determine whether a PEGylated LIF inhibitor (PEGLA) was an effective contraceptive following vaginal delivery and to identify non-uterine targets of PEGLA in mice.Vaginally-applied (125)I-PEGLA accumulated in blood more slowly (30 min vs 10 min) and showed reduced tissue and blood retention (24 h vs 96 h) compared to intraperitoneal injection in mice. Vaginally-applied PEGLA blocked implantation. PEGLA administered by intraperitoneal injection inhibited bone remodelling whereas vaginally-applied PEGLA had no effect on bone. Further, PEGLA had no effect in an animal model of multiple sclerosis, experimental auto-immune encephalomyelitis, suggesting PEGLA cannot target the central nervous system.Vaginally-administered PEGLA is a promising non-hormonal contraceptive, one which could be delivered alone, or in tandem with a microbicide. Vaginal application reduced the total dose of PEGLA required to block implantation and eliminated the systemic effect on bone, showing the vagina is a promising site of administration for larger drugs which target organs within the reproductive tract.
PLoS ONE 01/2011; 6(5):e19665. · 4.09 Impact Factor
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ABSTRACT: Thrombopoietin (TPO), acting through its receptor Mpl, has two major physiological roles: ensuring production of sufficient platelets via stimulation of megakaryocyte production and maintaining hematopoietic stem cell (HSC) quiescence. Mpl also controls circulating TPO concentration via receptor-mediated internalization and degradation. Here, we demonstrate that the megakaryocytosis and increased platelet mass in mice with mutations in the Myb or p300 genes causes reduced circulating TPO concentration and TPO starvation of the stem-cell compartment, which is exacerbated because these cells additionally exhibit impaired responsiveness to TPO. HSCs from Myb(Plt4/Plt4) mice show altered expression of TPO-responsive genes and, like HSCs from Tpo and Mpl mutant mice, exhibit increased cycling and a decline in the number of HSCs with age. These studies suggest that disorders of platelet number can have profound effects on the HSC compartment via effects on the feedback regulation of circulating TPO concentration.
Proceedings of the National Academy of Sciences 11/2010; 107(50):21689-94. · 9.68 Impact Factor
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ABSTRACT: Diverse human cancers with poor prognosis, including many lymphoid and myeloid malignancies, exhibit high levels of Mcl-1. To explore the impact of Mcl-1 overexpression on the hematopoietic compartment, we have generated vavP-Mcl-1 transgenic mice. Their lymphoid and myeloid cells displayed increased resistance to a variety of cytotoxic agents. Myelopoiesis was relatively normal, but lymphopoiesis was clearly perturbed, with excess mature B and T cells accumulating. Rather than the follicular lymphomas typical of vavP-BCL-2 mice, aging vavP-Mcl-1 mice were primarily susceptible to lymphomas having the phenotype of a stem/progenitor cell (11 of 30 tumors) or pre-B cell (12 of 30 tumors). Mcl-1 overexpression dramatically accelerated Myc-driven lymphomagenesis. Most vavP-Mcl-1/ Eμ-Myc mice died around birth, and transplantation of blood from bitransgenic E18 embryos into unirradiated mice resulted in stem/progenitor cell tumors. Furthermore, lethally irradiated mice transplanted with E13 fetal liver cells from Mcl-1/Myc bitransgenic mice uniformly died of stem/progenitor cell tumors. When treated in vivo with cyclophosphamide, tumors coexpressing Mcl-1 and Myc transgenes were significantly more resistant than conventional Eμ-Myc lymphomas. Collectively, these results demonstrate that Mcl-1 overexpression renders hematopoietic cells refractory to many cytotoxic insults, perturbs lymphopoiesis and promotes malignant transformation of hematopoietic stem and progenitor cells.
Blood 10/2010; 116(17):3197-207. · 9.90 Impact Factor
