The Experts below are selected from a list of 2109 Experts worldwide ranked by ideXlab platform
John D. Crispino - One of the best experts on this subject based on the ideXlab platform.
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PLATELETS AND THROMBOPOIESIS ETS2 and ERG promote Megakaryopoiesis and synergize with alterations in GATA-1 to immortalize hematopoietic progenitor cells
2016Co-Authors: Monika J Stankiewicz, John D. CrispinoAbstract:ETS2 and ERG are transcription factors, encoded on human chromosome 21 (Hsa21), that have been implicated in hu-man cancer. People with Down syndrome (DS), who are trisomic for Hsa21, are predisposed to acute megakaryoblastic leukemia (AMKL). DS-AMKL blasts har-bor a mutation in GATA1, which leads to loss of full-length protein but expression of the GATA-1s isoform. To assess the consequences of ETS protein misexpres-sion on Megakaryopoiesis, we expressed ETS2, ERG, and the related protein FLI-1 in wild-type and Gata1 mutant murine fetal liver progenitors. These studies re-vealed that ETS2, ERG, and FLI-1 facili-tated the expansion of megakaryocytes from wild-type, Gata1-knockdown, and Gata1s knockin progenitors, but none of the genes could overcome the differentia-tion block characteristic of the Gata1-knockdown megakaryocytes. Although overexpression of ETS proteins increased the proportion of CD41 cells generated from Gata1s-knockin progenitors, their expression led to a significant reduction in the more mature CD42 fraction. Serial replating assays revealed that overexpres-sion of ERG or FLI-1 immortalized Gata1-knockdown and Gata1s knockin, but not wild-type, fetal liver progenitors. Immortal-ization was accompanied by activation of the JAK/STAT pathway, commonly seen in megakaryocytic malignancies. These findings provide evidence for synergy between alterations in GATA-1 and overex-pression of ETS proteins in aberrant Megakaryopoiesis. (Blood. 2009;113
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gata 2 reinforces megakaryocyte development in the absence of gata 1
Molecular and Cellular Biology, 2009Co-Authors: Za Huang, Stua H Orki, Louis C Dore, Gang Feng, John D. CrispinoAbstract:GATA-2 is an essential transcription factor that regulates multiple aspects of hematopoiesis. Dysregulation of GATA-2 is a hallmark of acute megakaryoblastic leukemia in children with Down syndrome, a malignancy that is defined by the combination of trisomy 21 and a GATA1 mutation. Here, we show that GATA-2 is required for normal megakaryocyte development as well as aberrant Megakaryopoiesis in Gata1 mutant cells. Furthermore, we demonstrate that GATA-2 indirectly controls cell cycle progression in GATA-1-deficient megakaryocytes. Genome-wide microarray analysis and chromatin immunoprecipitation studies revealed that GATA-2 regulates a wide set of genes, including cell cycle regulators and megakaryocyte-specific genes. Surprisingly, GATA-2 also negatively regulates the expression of crucial myeloid transcription factors, such as Sfpi1 and Cebpa. In the absence of GATA-1, GATA-2 prevents induction of a latent myeloid gene expression program. Thus, GATA-2 contributes to cell cycle progression and the maintenance of megakaryocyte identity of GATA-1-deficient cells, including GATA-1s-expressing fetal megakaryocyte progenitors. Moreover, our data reveal that overexpression of GATA-2 facilitates aberrant Megakaryopoiesis.
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ets2 and erg promote Megakaryopoiesis and synergize with alterations in gata 1 to immortalize hematopoietic progenitor cells
Blood, 2009Co-Authors: Monika J Stankiewicz, John D. CrispinoAbstract:ETS2 and ERG are transcription factors, encoded on human chromosome 21 (Hsa21), that have been implicated in human cancer. People with Down syndrome (DS), who are trisomic for Hsa21, are predisposed to acute megakaryoblastic leukemia (AMKL). DS-AMKL blasts harbor a mutation in GATA1, which leads to loss of full-length protein but expression of the GATA-1s isoform. To assess the consequences of ETS protein misexpression on Megakaryopoiesis, we expressed ETS2, ERG, and the related protein FLI-1 in wild-type and Gata1 mutant murine fetal liver progenitors. These studies revealed that ETS2, ERG, and FLI-1 facilitated the expansion of megakaryocytes from wild-type, Gata1-knockdown, and Gata1s knockin progenitors, but none of the genes could overcome the differentiation block characteristic of the Gata1-knockdown megakaryocytes. Although overexpression of ETS proteins increased the proportion of CD41+ cells generated from Gata1s-knockin progenitors, their expression led to a significant reduction in the more mature CD42 fraction. Serial replating assays revealed that overexpression of ERG or FLI-1 immortalized Gata1-knockdown and Gata1s knockin, but not wild-type, fetal liver progenitors. Immortalization was accompanied by activation of the JAK/STAT pathway, commonly seen in megakaryocytic malignancies. These findings provide evidence for synergy between alterations in GATA-1 and overexpression of ETS proteins in aberrant Megakaryopoiesis.
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gata factor dependence of the multitype zinc finger protein fog 1 for its essential role in Megakaryopoiesis
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Aaron N Chang, John D. Crispino, Alan B. Cantor, Yuko Fujiwara, Maya B Lodish, Steven Droho, Stuart H OrkinAbstract:The function of GATA transcription factors in diverse developmental contexts depends in part on physical interaction with cofactors of the Friend of GATA (FOG) family. However, previous studies indicate that FOG-1 may play a GATA-1-independent role in early Megakaryopoiesis, suggesting that FOG proteins might act in a GATA factor-independent manner. Here, we have generated mouse knock-in (KI) mutants harboring a critical valine-to-glycine substitution in the amino-terminal zinc fingers of GATA-1 and GATA-2 to ablate FOG interaction. In contrast to male GATA-1KI (GATA-1 is located on the X-chromosome) or GATA-2KI/KI mice, compound GATA-1KI GATA-2KI/KI mutant mice display complete megakaryopoietic failure, a phenocopy of FOG-1−/− mice. We conclude that FOG-1 requires an interaction with either GATA-1 or -2 as part of its essential role in early Megakaryopoiesis. On the basis of these and previous reports, we infer that GATA factor dependence is a critical aspect of FOG protein function.
Weihong Tan - One of the best experts on this subject based on the ideXlab platform.
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requirement of tpo c mpl for il 17a induced granulopoiesis and Megakaryopoiesis
Journal of Leukocyte Biology, 2013Co-Authors: Bainan Liu, Adel L. Barsoum, Weihong Tan, Weitao Huang, Jay K. Kolls, Paul SchwarzenbergerAbstract:IL-17A is a critical, proinflammatory cytokine essential to host defense and is induced in response to microbial invasion. It stimulates granulopoiesis, leading to neutrophilia, neutrophil activation, and mobilization. TPO synergizes with other cytokines in stimulating and expanding hematopoietic progenitors, also leading to granulopoiesis and Megakaryopoiesis, and is required for thrombocytopoiesis. We investigated the effects of in vivo expression of IL-17A on granulopoiesis and Megakaryopoiesis in TPO receptor c-mpl-/- mice. IL-17A expression expanded megakaryocytes by 2.5-fold in normal mice but had no such effect in c-mpl-/- mice. The megakaryocyte expansion did not result in increased peripheral platelet counts. IL-17A expression did not impact bone marrow precursors in c-mpl-/- mice; however, it expanded splenic precursors, although to a lesser extent compared with normal controls (CFU-HPP). No peripheral neutrophil expansion was observed in c-mpl-/- mice. Moreover, in c-mpl-/- mice, release of IL-17A downstream cytokines was reduced significantly (KC, MIP-2, GM-CSF). The data suggest that IL-17A requires the presence of functional TPO/c-mpl to exert its effects on granulopoiesis and Megakaryopoiesis. Furthermore, IL-17A and its downstream cytokines are important regulators and synergistic factors for the physiologic function of TPO/c-mpl on hematopoiesis.
Toshiro Nagasawa - One of the best experts on this subject based on the ideXlab platform.
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simultaneous transient erythroblastopenia and agranulocytosis igg mediated inhibition of erythrogranulopoiesis
European Journal of Haematology, 2009Co-Authors: M Takashi D Hanada, Takao Ehara, Satoko Nakahara, Toshiyuki Suzuki, Toshiro Nagasawa, Hitoshi TakitaAbstract:We report a case of simultaneous transient erythroblastopenia and agranulocytosis recovering spontaneously. In vitro study using autologous bone marrow cells after recovery demonstrated IgG-mediated inhibition of both erythropoiesis and granulopoiesis but not Megakaryopoiesis. The inhibitory activity disappeared shortly after remission. These findings suggest that IgG-mediated inhibition of hematopoiesis may be pathogenetic for transient bone marrow failure of the patient.
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continuous expression of bcl xl protein during Megakaryopoiesis is post translationally regulated by thrombopoietin mediated akt activation which prevents the cleavage of bcl xl
Journal of Thrombosis and Haemostasis, 2007Co-Authors: Yukinori Kozuma, Hiroshi Kojima, Satoshi Yuki, Hidenori Suzuki, Toshiro NagasawaAbstract:Summary. Background: One of the important biological activities of thrombopoietin (TPO) is to prevent the apoptosis of megakaryocytes. As the antiapoptotic protein Bcl-xL, which has been proven to be indispensable for erythroid differentiation, is also abundantly expressed in megakaryocytes, it is assumed that Bcl-xL plays an important role in Megakaryopoiesis. Objectives: We investigated the expression of Bcl-xL during Megakaryopoiesis and the underlying regulatory mechanism. Methods and Results: In stem cell-derived megakaryocytes, expression of Bcl-xL increased in the early and mid-stages of the differentiation. Both in vitro in cell culture and in vivo in an animal model, expression of Bcl-xL protein was maintained until the platelet-producing stage. TPO depletion caused significant decrease in Bcl-xL protein level without affecting its mRNA in both megakaryocytes and TPO-dependent megakaryocytic UT-7/TPO cells, suggesting that Bcl-xL protein level in TPO-dependent cells is post-translationally regulated. In agreement with this finding, we recognized the appearance of a 12-kD fragment of Bcl-xL upon TPO depletion. This cleavage of Bcl-xL was inhibited by a caspase-3-specific inhibitor. Furthermore, pretreatment of UT-7/TPO with a phosphatidylinositol 3-kinase (PI3 K) inhibitor resulted in the cleavage of Bcl-xL even in the presence of TPO. We thus hypothesized that PI3 K inhibits the activation of caspase-3 and consequent cleavage of Bcl-xL. To prove this, we prepared UT-7/TPO cells transfected with constitutively active Akt-1. When TPO was depleted, the transfectant was significantly less liable to caspase-3 activation and Bcl-xL cleavage. Conclusions: Bcl-xL protein is expressed throughout Megakaryopoiesis until platelets are produced, and its expression level is at least in part post-translationally regulated through TPO-mediated Akt activation.
Yukinori Kozuma - One of the best experts on this subject based on the ideXlab platform.
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the pro apoptotic bh3 only protein bim regulates cell cycle progression of hematopoietic progenitors during Megakaryopoiesis
Journal of Thrombosis and Haemostasis, 2010Co-Authors: Yukinori Kozuma, Haruhiko Ninomiya, S Murata, Tomoko Kono, Harumi Y Mukai, Hiroshi KojimaAbstract:Summary. Background: The pro-apoptotic BH3-only protein Bim is recognized as a pivotal regulator of apoptosis induced by the depletion of cytokines. In the present study, we examined the role of Bim in Megakaryopoiesis. Methods: Megakaryocyte (MK) progenitors obtained from bim knockout (KO) mice were analyzed in vitro for liability to apoptosis after the depletion of cytokines, ability to differentiate into MKs and proliferation/cell cycle progression in response to thrombopoietin (TPO). The production of platelets in vitro was evaluated by assaying the formation of proplatelets in MKs. Megakaryopoiesis in vivo was observed in a mouse model of thrombocytopenia induced by injecting fluorouracil (5-FU). Results: Bim-deficient CD34-/c-kit+/Sca-1+/Lineage- stem cells and MKs were highly resistant to apoptosis induced by cytokine depletion, suggesting that Bim is involved in the apoptotic process in both stem cells and MKs. As bim KO mice exhibited splenomegaly and thrombocytopenia, splenectomized mice were used for experiments in vivo. Platelet recovery after 5-FU-induced thrombocytopenia was significantly delayed in bim KO mice. Corresponding with this, numbers of MKs in the recovery phase bone marrow were significantly reduced in bim KO mice. Culture of c-kit+/Lineage- progenitors with TPO revealed that Bim-deficient cells poorly proliferate and differentiate into CD41+ cells in comparison with wild-type (WT) cells. However, once differentiated into MKs, these cells matured normally. Furthermore, cell cycle analyses demonstrated that transition from the G1 to the S phase was delayed in Bim-deficient stem cells. Conclusions: In the present study, we demonstrated that Bim plays a pivotal role in the regulation of cell cycle progression in hepatopoietic progenitors during megakaryopiesis.
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continuous expression of bcl xl protein during Megakaryopoiesis is post translationally regulated by thrombopoietin mediated akt activation which prevents the cleavage of bcl xl
Journal of Thrombosis and Haemostasis, 2007Co-Authors: Yukinori Kozuma, Hiroshi Kojima, Satoshi Yuki, Hidenori Suzuki, Toshiro NagasawaAbstract:Summary. Background: One of the important biological activities of thrombopoietin (TPO) is to prevent the apoptosis of megakaryocytes. As the antiapoptotic protein Bcl-xL, which has been proven to be indispensable for erythroid differentiation, is also abundantly expressed in megakaryocytes, it is assumed that Bcl-xL plays an important role in Megakaryopoiesis. Objectives: We investigated the expression of Bcl-xL during Megakaryopoiesis and the underlying regulatory mechanism. Methods and Results: In stem cell-derived megakaryocytes, expression of Bcl-xL increased in the early and mid-stages of the differentiation. Both in vitro in cell culture and in vivo in an animal model, expression of Bcl-xL protein was maintained until the platelet-producing stage. TPO depletion caused significant decrease in Bcl-xL protein level without affecting its mRNA in both megakaryocytes and TPO-dependent megakaryocytic UT-7/TPO cells, suggesting that Bcl-xL protein level in TPO-dependent cells is post-translationally regulated. In agreement with this finding, we recognized the appearance of a 12-kD fragment of Bcl-xL upon TPO depletion. This cleavage of Bcl-xL was inhibited by a caspase-3-specific inhibitor. Furthermore, pretreatment of UT-7/TPO with a phosphatidylinositol 3-kinase (PI3 K) inhibitor resulted in the cleavage of Bcl-xL even in the presence of TPO. We thus hypothesized that PI3 K inhibits the activation of caspase-3 and consequent cleavage of Bcl-xL. To prove this, we prepared UT-7/TPO cells transfected with constitutively active Akt-1. When TPO was depleted, the transfectant was significantly less liable to caspase-3 activation and Bcl-xL cleavage. Conclusions: Bcl-xL protein is expressed throughout Megakaryopoiesis until platelets are produced, and its expression level is at least in part post-translationally regulated through TPO-mediated Akt activation.
Paul Schwarzenberger - One of the best experts on this subject based on the ideXlab platform.
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requirement of tpo c mpl for il 17a induced granulopoiesis and Megakaryopoiesis
Journal of Leukocyte Biology, 2013Co-Authors: Bainan Liu, Adel L. Barsoum, Weihong Tan, Weitao Huang, Jay K. Kolls, Paul SchwarzenbergerAbstract:IL-17A is a critical, proinflammatory cytokine essential to host defense and is induced in response to microbial invasion. It stimulates granulopoiesis, leading to neutrophilia, neutrophil activation, and mobilization. TPO synergizes with other cytokines in stimulating and expanding hematopoietic progenitors, also leading to granulopoiesis and Megakaryopoiesis, and is required for thrombocytopoiesis. We investigated the effects of in vivo expression of IL-17A on granulopoiesis and Megakaryopoiesis in TPO receptor c-mpl-/- mice. IL-17A expression expanded megakaryocytes by 2.5-fold in normal mice but had no such effect in c-mpl-/- mice. The megakaryocyte expansion did not result in increased peripheral platelet counts. IL-17A expression did not impact bone marrow precursors in c-mpl-/- mice; however, it expanded splenic precursors, although to a lesser extent compared with normal controls (CFU-HPP). No peripheral neutrophil expansion was observed in c-mpl-/- mice. Moreover, in c-mpl-/- mice, release of IL-17A downstream cytokines was reduced significantly (KC, MIP-2, GM-CSF). The data suggest that IL-17A requires the presence of functional TPO/c-mpl to exert its effects on granulopoiesis and Megakaryopoiesis. Furthermore, IL-17A and its downstream cytokines are important regulators and synergistic factors for the physiologic function of TPO/c-mpl on hematopoiesis.
