Thrombopoietin regulates IEX-1 gene expression through ERK-induced AML1 phosphorylation

Hamelin, Virginie; Letourneux, Claire; Roméo, Paul-Henri; Porteu, Françoise; Gaudry, Muriel

doi:10.1182/blood-2005-07-2953

Cited by 37 publications

(56 citation statements)

References 54 publications

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“…Point mutations that impair AML1 function are frequently found in MDS patients and can affect IEX-1 transcription, as multiple consensus-binding sites for AML1 have been identified in IEX-1 promoter. 36 Finally, IEX-1 is co-ordinately controlled by a dozen of transcriptional factors including NF-κB, p53, c-Myc, Sp1, p300, Ap1, etc., and alteration in any of these transcriptional factors caused by either DNA hypermethylation or mutations could adversely affect IEX-1 expression. 7 Another important finding of the investigation is that a pre-MDS phenotype of IEX-1 KO mice is not detectable by merely examining the numbers of circulating RBCs and platelets, due to extra-and intra-medullary compensation mechanisms.…”

Section: Discussionmentioning

confidence: 99%

Stress-induced hematopoietic failure in the absence of immediate early response gene X-1 (IEX-1, IER3)

et al. 2013

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© F e r r a t a S t o r t i F o u n d a t i o ntributes significantly to MDS pathogenesis in these patients. The present study shows that null mutation of IEX-1 perturbs HSC quiescence and impairs maturation of platelets and red blood cells (RBCs). Upon BM transplantation or non-myeloablative radiation, changes resembling MDS occurred, including thrombocytopenia, a trend toward anemia, and granulocyte dysplasia. These observations underscore an indispensable role for IEX-1 in maintenance of HSC quiescence as well as in multiple differentiation steps along thrombopoiesis and erythropoiesis. IEX-1-deficient mice confer a novel model for investigating how mitochondrial dysfunction may cause MDS and how to prevent or slow down the disease. Methods MiceIEX-1 knockout (KO) mice on mixed 129Sv/C57BL/6 background were generated by gene-targeting deletion in our laboratory, as previously described. 17 The KO mice were bred with wild type (WT) C57BL/6 (B6) for 10 generations to obtain IEX-1 KO B6 mice. WT B6 mice and mice on 129Sv/B6 background were derived from breeding as above and used as controls. Cognate BL/6.SJL-Ptprc a Pep 3 /BoyJ (CD45.1) or PepJ mice were obtained from Jackson Laboratory. All experimental mice and BM donor mice were used at 6-8 weeks of age. Animals were maintained in the pathogen-free animal facilities of Massachusetts General Hospital in compliance with institutional guidelines. All animal studies were approved by the Subcommittee on Research Animal Care of the institute. Extended methods can be found in the Online Supplementary Appendix. Results Perturbation of HSC quiescence in the absence of IEX-1IEX-1 KO mice display no gross developmental defect except for modest hypertension at 2-months of age or older, 17,18 in agreement with its function required primarily in response to stress. Given the significant loss of IEX-1 reported in patients with early stage MDS, 14,16 we examined the status of LSK (Lineage-Sca-1 + c-Kit + ) stem cells in IEX-1 KO mice. Loss of IEX-1 led to a significant decline in the proportion of LSK cells, in comparison with WT mice (0.10±0.07% vs. 0.24±0.06 %; P<0.01) ( Figure 1A). Apparently, the decline contradicted increased cycling of the cells, as shown in Figure 1B and C, in which relatively higher proportions of KO LSK cells entered G1 and G2/S/M cycling phases than WT counterparts, concurrent with a reduced percentage of the cells at a Go or quiescent phase. We thus examined whether the decline was ascribed to increased apoptosis of the cells, because apoptosis in HSCs was abnormally high in many MDS patients. 19 Increased apoptosis of IEX-1 KO over WT BM cells was confirmed by apoptosis-specific terminal deoxynucleotydyl transferase-mediated dUTP nick end labeling or TUNEL (11.6±0.7% vs. 2.2±0.4%; P<0.01), which detected apoptosis at both early and late stages. Early apoptotic marker Annexin V staining further revealed that apoptosis was increased by more than 50% in the BM (6.9±0.5% vs. 4.5±0.3%; P<0.01) ( Figure 1D In spite of a reduced percentage of L...

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Section: Discussionmentioning

confidence: 99%

Stress-induced hematopoietic failure in the absence of immediate early response gene X-1 (IEX-1, IER3)

et al. 2013

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“…37 Removal of TPO from the medium led to a striking decrease in total pErk1/2 levels ( Figure 2A The early gene IEX-1/IER3 was previously found to regulate DNA damage responses upon IR. 32 In addition, we have identified the IEX-1 protein as an Erk substrate involved in TPO-mediated function in megakaryocytes, 24,25 suggesting that it could play a role in TPO/Erk signaling-mediated DNA repair in HSPCs. Compatible with this possibility, the Iex-1 messenger RNA (mRNA) expression pattern follows that of Mpl, increasing greatly in HSC-enriched populations ( Figure 3A).…”

Section: Tpo Is the Main Activator Of Erks In Hspcsmentioning

confidence: 99%

“…Similar results were found in UT7-Mpl cells (supplemental Figure 3A). 10,25 TPO and IR act additively to induce IEX-1 mRNA and protein expression in UT7-Mpl cells and in CD34…”

Section: Iex-1 and Erk Form A Complex With Dna-pkc That Is Required Fmentioning

confidence: 99%

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Thrombopoietin promotes NHEJ DNA repair in hematopoietic stem cells through specific activation of Erk and NF-κB pathways and their target, IEX-1

Laval

Pawlikowska

Barbieri

et al. 2014

Blood

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Key Points• TPO specifically activates Erk and NF-kB pathways in hematopoietic stem and progenitor cells.• Erk and NF-kB cooperate to trigger their common target, Iex-1, and DNA-PKdependent NHEJ activation in HSPCs upon irradiation.Loss of hematopoietic stem cell (HSC) function and increased risk of developing hematopoietic malignancies are severe and concerning complications of anticancer radiotherapy and chemotherapy. We have previously shown that thrombopoietin (TPO), a critical HSC regulator, ensures HSC chromosomal integrity and function in response to g-irradiation by regulating their DNA-damage response. TPO directly affects the double-strand break (DSB) repair machinery through increased DNA-protein kinase (DNA-PK) phosphorylation and nonhomologous end-joining (NHEJ) repair efficiency and fidelity. This effect is not shared by other HSC growth factors, suggesting that TPO triggers a specific signal in HSCs facilitating DNA-PK activation upon DNA damage. The discovery of these unique signaling pathways will provide a means of enhancing TPO-desirable effects on HSCs and improving the safety of anticancer DNA agents. We show here that TPO specifically triggers Erk and nuclear factor kB (NF-kB) pathways in mouse hematopoietic stem and progenitor cells (HSPCs). Both of these pathways are required for a TPO-mediated increase in DSB repair. They cooperate to induce and activate the early stress-response gene, Iex-1 (ier3), upon DNA damage. Iex-1 forms a complex with pERK and the catalytic subunit of DNA-PK, which is necessary and sufficient to promote TPO-increased DNA-PK activation and NHEJ DSB repair in both mouse and human HSPCs. (Blood. 2014;123(4):509-519)

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“…The defect in the activity of HSCs produced by Mpl -/-AGM underlines an additional specific role of Mpl signaling in the self-renewal/survival of HSCs at the earliest stages of their emergence in the embryo. Of interest, Mpl has possible interactions with Runx1, one of the genes involved in the emergence of definitive HSCs in the AGM region (Teitell and Mikkola, 2006): on the one hand, TPO/Mpl signaling can regulate the activity of Runx1 through the ERK pathway (Hamelin et al, 2006); on the other hand, Runx1 can putatively regulate Mpl expression, as three Runx1 binding sites are present in the promoter region of Mpl (Heller et al, 2005). The FL is the main site of HSC expansion and differentiation; the first HSCs appear in this organ at E11.5 and are likely to come from the AGM and placenta (Mikkola and Orkin, 2006).…”

Section: Research Articlementioning

confidence: 99%

Dual role of Mpl receptor during the establishment of definitive hematopoiesis

et al. 2007

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*Cytokine signaling pathways are important in promoting hematopoietic stem cell (HSC) self-renewal, proliferation and differentiation. Mpl receptor and its ligand, TPO, have been shown to play an essential role in the early steps of adult hematopoiesis. We previously demonstrated that the cytoplasmic domain of Mpl promotes hematopoietic commitment of embryonic stem cells in vitro, and postulated that Mpl could be important in the establishment of definitive hematopoiesis. To answer this question, we investigated the temporal expression of Mpl during mouse development by in situ hybridization. We found Mpl expression in the HSCs clusters emerging in the AGM region, and in the fetal liver (FL) as early as E10.5. Using Mpl -/-mice, the functional relevance of Mpl expression was tested by comparing the hematopoietic progenitor (HP) content, long-term hematopoietic reconstitution (LTR) abilities and HSC content of control and Mpl -/-embryos at different times of development. In the AGM, we observed delayed production of HSCs endowed with normal LTR but presenting a self-renewal defect. During FL development, we detected a decrease in HP and HSC potential associated with a defect in amplification and self-renewal/survival of the lin -AA4.1 + Sca1 + population of HSCs. These results underline the dual role of Mpl in the generation and expansion of HSCs during establishment of definitive hematopoiesis.

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Thrombopoietin regulates IEX-1 gene expression through ERK-induced AML1 phosphorylation

Cited by 37 publications

References 54 publications

Stress-induced hematopoietic failure in the absence of immediate early response gene X-1 (IEX-1, IER3)

Stress-induced hematopoietic failure in the absence of immediate early response gene X-1 (IEX-1, IER3)

Thrombopoietin promotes NHEJ DNA repair in hematopoietic stem cells through specific activation of Erk and NF-κB pathways and their target, IEX-1

Dual role of Mpl receptor during the establishment of definitive hematopoiesis

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