Expanding Hematopoietic Stem Cell pool through Fine tuning of Tpo receptor with diabodies.
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE115235 | GEO | 2021/02/01
REPOSITORIES: GEO
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Project description:Small molecular TPO mimetics, LGD-4665 and eltrombopag, were efficacious in stimulating the formation of CD41+ cells from human bone marrow CD34+ cells. To better understand the mechanism of action of TPO mimetics, a microarray study was performed to compare global gene expression in CD34+ cells induced by small molecular TPO mimetics eltrombopag and LGD4665, to changes in response to recombinant human thrombopoietin (TPO). Keywords: Drug Treatment
2019-03-24 | GSE12968 | GEO
Project description:The haematopoietic cytokine thrombopoietin (Tpo) is the primary regulator of megakaryocyte and platelet numbers and is required for maintenance of the haematopoetic stem cell compartment. Tpo is a heavily glycosylated, hepatocyte-derived cytokine which functions by binding to its receptor (TpoR) on target cells and thereby activating intracellular signalling cascades that induce their proliferation and/or differentiation. In addition to its role in signal propagation, TpoR is expressed on the surface of platelets, where it contributes to regulation of Tpo levels by sequestering circulating cytokine. TpoR belongs to the homodimeric Class I cytokine receptor family but is unusual due to a duplication of the Cytokine binding Homology Region (CHR). Almost thirty years after initial discovery of TpoR, the structure of the human Tpo:TpoR interaction was recently reported. Here we determine the structure of extracellular portion of the murine Tpo:TpoR signalling complex using single particle cryo-EM. The structure reveals that Tpo:TpoR forms a largely symmetrical 1:2 complex. The cytokine cross-links the same site on the membrane-distal CHR of both receptor chains using opposing surfaces and with significantly different affinities. This orients the two membrane-proximal CHRs such that they contact one another adjacent to the plasma membrane. The potential cytokine-binding site in CHR2 is glycosylated and does not interact with Tpo. A large insertion in CHR1 that is unique to Tpo forms a partially structured loop that is disulphide bonded to CHR2 and, in one receptor chain, contacts cytokine. Biochemical analyses indicate that the glycosylated C-terminal domain of Tpo does not influence receptor binding. We demonstrate that the therapeutic TpoR agonist Romiplostim binds to the same site on the receptor as does cytokine. Our study characterises the Tpo/TpoR interaction structurally and biochemically to allow for the future development of potent TpoR agonists for therapeutic use.
2024-01-09 | PXD046926 | Pride
Project description:The STOPAGO study enrolled adults with persistent or chronic primary immune thrombocytopenia (ITP) and complete response to thrombopoietin receptor agonist (TPO-RA). TPO-RA discontinuation was planned in the study and patients with sustained complete response off-treatment (SCROT, platelet count > 100 G/L and no bleeding) and non sustained response (NSR, platelet count < 30 G/L or bleeding) were identified at week 24. RNAseq of peripheral blood mononuclear cells was performed at baseline, before TPO-RA discontinuation. Samples originated from 8 patients (4 with SCROT and 4 with NSR). The objectif was to identify putative markers that would predict relapses after TPO-RA discontinuation by comparing SCROT and NSR patients.
2023-10-01 | E-MTAB-12397 | biostudies-arrayexpress
Project description:TPO mimetics have been shown to activate TPO receptor, the downstream JAK-STAT pathway, and induce differentiation of hematopoietic stem cells into megakaryocytes. However, the action of these TPO mimetics is initiated by binding to the transmembrane domain of the TPO receptor, which is distinct from the binding site of the native ligand, TPO. To determine whether TPO mimetics can differentiate hematopoietic stem cells into the same megakaryocytes as native TPO does, we performed a microarray experiment to compare the globe gene expression in purified CD61+ cells derived from TPO or TPO mimetic treated CD34+ bone marrow cells. Keywords: Drug Treatment
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Project description:Thrombopoietin (TPO) acting via its receptor Mpl is the major cytokine regulator of platelet number. To precisely define the role of specific hematopoietic cells in TPO dependent hematopoiesis, we generated mice that express the Mpl receptor normally on stem/progenitor cells but lack expression on megakaryocytes and platelets (MplPF4cre/PF4cre). MplPF4cre/PF4cre mice displayed profound megakaryocytosis and thrombocytosis with a remarkable expansion of megakaryocyte-committed and multipotential progenitor cells, the latter displaying biological responses and a gene expression signature indicative of chronic TPO over-stimulation as the underlying causative mechanism, despite a normal circulating TPO level. Thus, TPO signaling in megakaryocytes is dispensable for platelet production; its key role in control of platelet number is via generation and stimulation of the bipotential megakaryocyte precursors. Nevertheless, Mpl expression on megakaryocytes and platelets is essential to prevent megakaryocytosis and myeloproliferation by restricting the amount of TPO available to stimulate the production of megakaryocytes from the progenitor cell pool.
2014-06-10 | E-MTAB-2389 | biostudies-arrayexpress
Project description:Thrombopoietin (TPO) is a critical cytokine regulating hematopoietic stem cell maintenance and differentiation into the megakaryocytic lineage. However, the transcriptional and chromatin dynamics elicited by TPO signaling are poorly understood. Here, we study the immediate early transcriptional and cis-regulatory responses to TPO in hematopoietic stem/progenitor cells (HSPCs) and use this paradigm of cytokine signaling to chromatin to dissect the relation between cis-regulatory activity and chromatin architecture. We show that TPO profoundly alters the transcriptome of HSPCs, with key hematopoietic regulators being transcriptionally repressed within 30 minutes of TPO. By examining cis-regulatory dynamics and chromatin architectures, we demonstrate that these changes are accompanied by rapid and extensive epigenome remodeling of cis-regulatory landscapes that is spatially coordinated within topologically associating domains (TADs). Moreover, homotypic TPO-responsive enhancers are spatially clustered and engage in preferential intra- and inter-TAD interactions that are only moderately perturbed by TPO signaling. By further examining the link between cis-regulatory dynamics and chromatin looping, we show that rapid modulation of cis-regulatory activity is largely independent of chromatin looping dynamics. Finally, we show that activated and repressed cis-regulatory elements share a remarkably similar DNA sequence composition and that in vivo transcription factor binding patterns accurately predict rapid cis-regulatory responses to TPO.
2018-01-25 | GSE100835 | GEO
Project description:Thrombopoietin (TPO) and its receptor MPL play crucial roles in hematopoietic stem cell (HSC) function and platelet production. However, the precise effects of TPO/MPL signaling on HSC regulation in different hematopoietic niches remain unclear. Here, we investigated the effects of TPO/MPL ablation on marrow and splenic hematopoiesis in TPO-/- and MPL-/- mice during aging. Despite severe thrombocytopenia, TPO-/- and MPL-/- mice did not develop marrow failure during a 2-year follow-up. Marrow and splenic HSCs exhibited different responses to TPO/MPL ablation and exogenous TPO treatment. Splenic niche cells compensated for marrow HSC loss in TPO-/- and MPL-/- mice by upregulating CXCL12 levels. These findings provide new insights into the complex regulation of HSCs by TPO/MPL and reveal a previously unknown link between TPO and CXCL12, two key growth factors for HSC maintenance. Understanding the distinct regulatory mechanisms between marrow and spleen hematopoiesis will help develop novel therapeutic approaches for hematopoietic disorders.
2023-12-16 | GSE249912 | GEO
Project description:Biologic characterization of SB-559457 (SB), a non-peptidyl hydrazone class of thrombopoietin receptor (Mpl) agonist, revealed toxicity towards human leukemia cells. Anti-proliferative effects followed by significant, non-apoptotic, cell death within 72 hours occurred in 24/26 AML, 0/6 ALL, and 3/6 CML patient samples exposed to SB, but not recombinant human thrombopoietin (rhTpo), in liquid suspension culture. Further investigation revealed increased phosphorylation of p70S6/S6 kinases in SB, but not in rhTpo, treated cells. Expression profiling of cells exposed to SB vs rhTpo revealed statistically significant, ~2-fold changes in GAPDH and REDD1 gene expression, confirmed by QRT-PCR. These genes, induced in energy or hypoxia stressed cells, have been implicated in cell death pathways, and may provide important clues to the mechanism of SB induced, leukemic cell death. These results suggest that nonpeptidyl, hydrazone class Mpl agonists may be clinically useful anti-leukemic agents by virtue of their combined thrombopoietic and anti-leukemic effects. Experiment Overall Design: Primary cells collected from 5 patients with acute myeloid leukemia (AML) were stimulated stimulated with MPL receptor agonist (SB559457) or recombinant human Tpo (rhTpo) for 6 hours. Next, RNA was isolated from these cells. RNA was used for gene profile analyis to compare genes regulated in AML cells by SB559457 verus rhTpo. For each sample half of the cells were stimulated with Mpl agonist and half with rhTpo.
2009-11-10 | E-GEOD-18673 | biostudies-arrayexpress
Project description:Notch signaling regulates cell-fate decisions in several developmental processes and cell functions. However, a role for Notch in hepatic thrombopoietin (TPO) production remains unclear. We noted thrombocytopenia in mice with hepatic Notch1 deficiency, and so investigated TPO production and other features of platelets in these mice. We found that the liver ultrastructure and hepatocyte function were comparable between control mice and Notch1-deficient mice. However, the Notch1-deficient mice had significantly lower plasma TPO and hepatic TPO mRNA levels, concomitant with lower numbers of platelets and impaired megakaryocyte differentiation and maturation, which were rescued by addition of exogenous TPO. Additionally, JAK2/STAT3 phosphorylation was significantly inhibited in Notch1-deficient hepatocytes, consistent with the RNA-seq analysis. JAK2/STAT3 phosphorylation and TPO production was also impaired in cultured Notch1-deficient hepatocytes after treatment with desialylated platelets. Consistently, hepatocyte-specific Notch1 deletion inhibited JAK2/STAT3 phosphorylation and hepatic TPO production induced by administration of desialylated platelets in vivo. Interestingly, Notch1 deficiency downregulated the expression of HES5 but not HES1. Moreover, desialylated platelets promoted the binding of HES5 to JAK2/STAT3, leading to JAK2/STAT3 phosphorylation and pathway activation in hepatocytes. Hepatocyte Ashwell-Morell receptor (AMR) (asialoglycoprotein receptor 1, ASGR1) physically associates with Notch1 and inhibition of AMR impaired Notch1 signaling activation and hepatic TPO production. Furthermore, blockage of Dll4 on desialylated platelets inhibited hepatocyte Notch1 activation and HES5 expression, JAK2/STAT3 phosphorylation and subsequent TPO production. In conclusion, our study identifies a novel regulatory role of Notch1 in hepatic TPO production, indicating that it might be a target for modulating TPO level.
2024-04-12 | GSE250529 | GEO
Project description: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 internalisation and degradation. 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. Total RNA obtained from bone marrow Lineage- Sca-1+ c-Kit+ cells of mice that were mutant or knocked out for Myb, p300 or Mpl were compared to wild type samples. We have found that HSCs from MybPlt4/Plt4 and p300Plt6/Plt6 mice show altered expression of TPO-responsive genes, suggesting that TPO starvation is an important factor in the hematopoietic phenotypes observed in these mice .
2011-01-31 | E-TABM-1050 | biostudies-arrayexpress