| 1. |
- Anderson, Kristina, et al.
(författare)
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Ectopic expression of PAX5 promotes maintenance of biphenotypic myeloid progenitors coexpressing myeloid and B-cell lineage-associated genes
- 2007
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 109:9, s. 3697-3705
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Tidskriftsartikel (refereegranskat)abstract
- The transcription factor PAX5 is a critical regulator of B-cell commitment and development. Although normally not expressed in myeloid progenitors, PAX5 has recently been shown to be frequently expressed in myeloid malignancies and to suppress expression of myeloid differentiation genes, compatible with an effect on the differentiation or maintenance of myeloid progenitors. However, previous studies in which PAX5 was ectopically expressed in normal myeloid progenitors in vivo and in vitro provided conflicting results as to the effect of PAX5 on myeloid development. Herein, we demonstrate that on ectopic expression of PAX5 in bone marrow multipotent stem/progenitor cells, cells with a biphenotypic B220+GR-1/MAC-1+ phenotype are produced. These remain cytokine-dependent, but unlike control-transduced cells they sustain long-term generation of myeloid progenitors in vitro and remain capable of myeloid differentiation. Notably, PAX5+B220+GR-1/MAC- 1+ myeloid progenitors coexpress, at the single-cell level, myeloid genes and otherwise B-cell-specific PAX5 target genes. These findings establish that ectopic expression of PAX5 introduces extensive self-renewal properties in otherwise short-lived myeloid progenitors. Along with the established ectopic expression of PAX5 in acute myeloid leukemia, this motivates a careful investigation of the potential involvement of ectopic PAX5 expression in myeloid and biphenotypic leukemias. © 2007 by The American Society of Hematology.
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| 2. |
- Bratengeier, Cornelia, 1983-
(författare)
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Mechanisms of mechanically induced Osteoclastogenesis : in a novel in vitro model for bone implant loosening
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Total joint arthroplasty is the primary intervention in the treatment of end-stage osteoarthritis. Despite the high success rate, in some patients, the replacement will fail during their lifetime requiring a revision of the implant. These revisions are strenuous for the patient and costly for health care. Joint replacement at a younger age, in combination with a more active lifestyle, increases the need for an early revision of the joint prosthesis. The main reason for revision surgeries is aseptic loosening, a condition where the prosthesis is loosening due to bone degradation at the peri-prosthetic interface in the absence of infections. The most well-established pathological mechanism for aseptic loosening is related to wear particles, generated from different parts of the prosthesis that will trigger bone degradation and bone loss. In addition, early micromotions of the prosthesis and resulting local pressurized fluid flow in the peri-prosthetic interface (supraphysiological loading) have also been identified as a cause for aseptic loosening. However, it remains unknown what cells are the primary responders to supraphysiological loading, and what underlying physical, cellular and molecular mechanism that triggers osteoclast differentiation and osteolysis.In this thesis, we intended to shed light on three currently unknown aspects of mechanical loading-induced peri-prosthetic osteolysis, leading to aseptic loosening of orthopedic prostheses: (1)Which cells are the primary responder to supraphysiological loading? (2)What characteristics of the mechanical stimulus induce an osteo-protective or osteo-destructive response? (3)Which cellular mechano-sensing mechanisms are involved in an osteo-destructive response?We successfully implemented supraphysiological mechanical loading, mimicking the periprosthetic pressurized fluid flow around a loosening implant, in an in vitro model for bone implant loosening. Using this model, we uncovered the involvement of mesenchymal stem cells and myeloid progenitor cells (monocytes) in mechanical loading-induced peri-prosthetic osteolysis. Applying supraphysiological loading on cells from patients undergoing primary hip arthroplasty, successfully validated the in vitro model for the use of cells of human origin. We further identified in murine myeloid progenitor cells that a combination of high loading amplitude (3.0±0.2Pa), prolonged active loading duration per cycle (duty cycle 22%-50%), and rapid alterations in minimum/maximum values of the loading profile (square wave) is necessary to induce an osteo-destructive response. Further, the loading-induced ATP release and subsequent activation of the P2X7 receptor was essential for the release of soluble factors modulating osteoclastogenesis.In conclusion, we expect that the proposed new in vitro model is a helpful tool to further advance the knowledge in aseptic loosening, by uncovering the mechanoresponsive cellular mechanism to supraphysiological mechanical loading. The identification of the respondent cells in mechanical loading-induced prosthetic loosening gives the opportunity to deliver targeted treatment strategies. Furthermore, identifying the physical parameters that define the shift towards an osteo-destructive response emphasizes the importance of the prosthetic design and surgical technique to reduce mechanical loading-induced bone degradation around a prosthesis.
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| 3. |
- Dias, Sheila, et al.
(författare)
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E2A Proteins Promote Development of Lymphoid-Primed Multipotent Progenitors
- 2008
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Ingår i: Immunity. - : Elsevier BV. - 1074-7613 .- 1097-4180. ; 29:2, s. 217-227
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Tidskriftsartikel (refereegranskat)abstract
- The first lymphoid-restricted progeny of hematopoietic stem cells (HSCs) are lymphoid-primed multipotent progenitors (LMPPs), which have little erythromyeloid potential but retain lymphoid, granulocyte, and macrophage differentiation capacity. Despite recent advances in the identification of LMPPs, the transcription factors essential for their generation remain to be identified. Here, we demonstrated that the E2A transcription factors were required for proper development of LMPPs. Within HSCs and LMPPs, E2A proteins primed expression of a subset of lymphoid-associated genes and prevented expression of genes that are not normally prevalent in these cells, including HSC-associated and nonlymphoid genes. E2A proteins also restricted proliferation of HSCs, MPPs, and LMPPs and antagonized differentiation of LMPPs toward the myeloid fate. Our results reveal that E2A proteins play a critical role in supporting lymphoid specification from HSCs and that the reduced generation of LMPPs underlies the severe lymphocyte deficiencies observed in E2A-deficient mice. © 2008 Elsevier Inc. All rights reserved.
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| 4. |
- Dolinska, Monika, et al.
(författare)
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Characterization of Bone Marrow Niche in Chronic Myeloid Leukemia Patients Identifies CXCL14 as a New Therapeutic Option
- 2023
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 142:1, s. 73-89
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Tidskriftsartikel (refereegranskat)abstract
- Although tyrosine kinase inhibitors (TKIs) are effective in treating chronic myeloid leukemia (CML), they often fail to eradicate the leukemia-initiating stem cells (LSCs), causing disease persistence and relapse. Evidence indicates that LSC persistence may be because of bone marrow (BM) niche protection; however, little is known about the underlying mechanisms. Herein, we molecularly and functionally characterize BM niches in patients with CML at diagnosis and reveal the altered niche composition and function in these patients. Long-term culture initiating cell assay showed that the mesenchymal stem cells from patients with CML displayed an enhanced supporting capacity for normal and CML BM CD34+CD38- cells. Molecularly, RNA sequencing detected dysregulated cytokine and growth factor expression in the BM cellular niches of patients with CML. Among them, CXCL14 was lost in the BM cellular niches in contrast to its expression in healthy BM. Restoring CXCL14 significantly inhibited CML LSC maintenance and enhanced their response to imatinib in vitro, and CML engraftment in vivo in NSG-SGM3 mice. Importantly, CXCL14 treatment dramatically inhibited CML engraftment in patient-derived xenografted NSG-SGM3 mice, even to a greater degree than imatinib, and this inhibition persisted in patients with suboptimal TKI response. Mechanistically, CXCL14 upregulated inflammatory cytokine signaling but downregulated mTOR signaling and oxidative phosphorylation in CML LSCs. Together, we have discovered a suppressive role of CXCL14 in CML LSC growth. CXCL14 might offer a treatment option targeting CML LSCs.
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| 5. |
- Halvarsson, Camilla, 1985-
(författare)
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Hypoxia inducible factor 1 alpha : dependent and independent regulation of hematopoietic stem cells and leukemia
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis has studied the role of low oxygen levels, or hypoxia, in hematopoietic stem cells (HSCs) and how, at the molecular level, it regulates stem cell maintenance and protects against oxidative stress induced by reactive oxygen species (ROS). HSCs reside within the bone marrow in specific niches created by a unique vascularized environment, which is suggested to be hypoxic and crucial for HSCs by maintaining a quiescent state of cell cycle and by redirecting metabolism away from the mitochondria to glycolysis. The niches are also believed to limit the production of ROS, which could damage DNA and disrupt the stem cell features. The hypoxia-responsive protein hypoxia-inducible factor 1 alpha (HIF-1α) is a major regulator of the hypoxic cell response in HSCs as well as in leukemic stem cells. Both these cells are thought to reside in the bone marrow where they are protected from stress and chemotherapy by niche cells and hypoxia.The thesis demonstrates that pyruvate dehydrogenase kinase 1 regulates a metabolic shift to glycolysis, and maintains the engraftment potential of both HSCs and multipotent progenitors upon transplantation. Furthermore, we wanted to determine whether HIF-1α or other signaling pathways are involved in protecting HSCs from ROS-induced cell death. Overexpression, silencing or a knockout mouse model of Hif-1α could not identify HIF-1α as important for protecting HSCs from oxidative stress-induced cell death through inhibition of synthesis of the antioxidant glutathione. Gene expression analysis instead identified the transcription factor nuclear factor kappa B (NF-κB) as induced by hypoxia. By studying NF- κB signaling we found increased NF-κB activity in cells cultured in hypoxia compared to normoxia. Suppression of inhibitor of kappa B indicated a putative role of NF-κB signaling in hypoxia-induced protection against oxidative stress. The findings show that hypoxia-induced protection to elevated levels of ROS upon glutathione depletion seems to be attributed to activation of the NF-κB signaling pathway independently of HIF-1α.To address the question whether hypoxic in vitro cultures support maintenance and promote HSC expansion we performed a limited dilution-transplantation assay. Our data indicate that hypoxic cultures maintain more long-term-reconstituting HSCs than normoxia, but this could not be confirmed statistically. Finally, we wanted to study the mechanisms by which hypoxia protect against chemotherapy. We could demonstrate that hypoxic culture protects leukemic cell lines against apoptosis induced by chemotherapy or inhibitors used for treatment of leukemia. This multidrug resistance seems to be mediated by ATP-binding cassette transporter genes, which are upregulated by hypoxia and whose inhibition has been shown to increase chemosensitivity. In addition, HIF-1α was upregulated in the leukemic cell lines in hypoxia and its inhibition increased the sensitivity to chemotherapy, indicating a role in inducing chemotherapy resistance.Conclusively, the results presented in this thesis stress the importance of hypoxia in regulating metabolism, oxidative-stress response and maintenance of both HSCs as well as leukemic cells, especially through the critical transcription factors HIF-1α and NF-κB and their target genes.
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| 6. |
- Hansson, Frida, et al.
(författare)
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Exit of pediatric pre-B acute lymphoblastic leukaemia cells from the bone marrow to the peripheral blood is not associated with cell maturation or alterations in gene expression
- 2008
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Ingår i: Molecular Cancer. - : Springer Science and Business Media LLC. - 1476-4598. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Background: Childhood pre-B acute lymphoblastic leukemia (ALL) is a bone marrow (BM) derived disease, which often disseminates out of the BM cavity, where malignant cells to a variable degree can be found circulating in the peripheral blood (PB). Normal pre-B cells are absolutely dependent on BM stroma for survival and differentiation. It is not known whether transformed pre-B ALL cells retain any of this dependence, which possibly could impact on drug sensitivity or MRD measurements. Results: Pre-B ALL cells, highly purified by a novel method using surface expression of CD19 and immunoglobulin light chains, from BM and PB show a very high degree of similarity in gene expression patterns, with differential expression of vascular endothelial growth factor (VEGF) as a notable exception. In addition, the cell sorting procedure revealed that in 2 out of five investigated patients, a significant fraction of the malignant cells had matured beyond the pre-B cell stage. Conclusion: The transition of ALL cells from the BM into the circulation does not demand, or result in, major changes of gene expression pattern. This might indicate an independence of BM stroma on the part of transformed pre-B cells, which contrasts with that of their normal counterparts. © 2008 Hansson et al, licensee BioMed Central Ltd.
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| 7. |
- Jensen, Christina, et al.
(författare)
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Permissive roles of hematopoietin and cytokine tyrosine kinase receptors in early T-cell development
- 2008
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 111:4, s. 2083-2090
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Tidskriftsartikel (refereegranskat)abstract
- Although several cytokines have been demonstrated to be critical regulators of development of multiple blood cell lineages, it remains disputed to what degree they act through instructive or permissive mechanisms. Signaling through the FMS-like tyrosine kinase 3 (FLT3) receptor and the hematopoietin IL-7 receptor alpha (IL-7Ralpha) has been demonstrated to be of critical importance for sustained thymopoiesis. Signaling triggered by IL-7 and thymic stromal lymphopoietin (TSLP) is dependent on IL-7Ralpha, and both ligands have been implicated in T-cell development. However, we demonstrate that, whereas thymopoiesis is abolished in adult mice doubly deficient in IL-7 and FLT3 ligand (FLT3L), TSLP does not play a key role in IL-7-independent or FLT3L-independent T lymphopoiesis. Furthermore, whereas previous studies implicated that the role of other cytokine tyrosine kinase receptors in T lymphopoiesis might not involve permissive actions, we demonstrate that ectopic expression of BCL2 is sufficient not only to partially correct the T-cell phenotype of Flt3l(-/-) mice but also to rescue the virtually complete loss of all discernable stages of early T lymphopoiesis in Flt3l(-/-)Il7r(-/-) mice. These findings implicate a permissive role of cytokine receptors of the hematopoietin and tyrosine kinase families in early T lymphopoiesis.
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| 8. |
- Jimenez, Maria A, et al.
(författare)
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Critical role for Ebf1 and Ebf2 in the adipogenic transcriptional cascade
- 2007
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Ingår i: Molecular and Cellular Biology. - 0270-7306 .- 1098-5549. ; 27:2, s. 743-757
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Tidskriftsartikel (refereegranskat)abstract
- The Ebf (O/E) family of helix-loop-helix transcription factors plays a significant role in B lymphocyte and neuronal development. The three primary members of this family, Ebf1, 2, and 3, are all expressed in adipocytes, and Ebf1 promotes adipogenesis when overexpressed in NIH 3T3 fibroblasts. Here we report that these three proteins have adipogenic potential in multiple cellular models and that peroxisome proliferator-activated receptor (PPAR) is required for this effect, at least in part due to direct activation of the PPAR1 promoter by Ebf1. Ebf1 also directly binds to and activates the C/EBP promoter, which exerts positive feedback on C/EBP expression. Despite this, C/EBP is dispensable for the adipogenic action of Ebf proteins. Ebf1 itself is induced by C/EBPß and , which bind and activate its promoter. Reduction of Ebf1 and Ebf2 proteins by specific short hairpin RNA blocks differentiation of 3T3-L1 cells, suggesting a critical role for these factors and the absence of functional redundancy between members of this family. Altogether, these data place Ebf1 within the known transcriptional cascade of adipogenesis and suggest critical roles for Ebf1 and Ebf2.
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| 9. |
- Lagergren, Anna, et al.
(författare)
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The Cxcl12, Periostin, and Ccl9 genes are direct targets for early B-cell factor in OP-9 stroma cells
- 2007
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 282:19, s. 14454-14462
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Tidskriftsartikel (refereegranskat)abstract
- The development of blood cells from hematopoietic stem cells in the bone marrow is dependent on communication with bone marrow stroma cells, making these cells central for the appropriate regulation of hematopoiesis. To identify transcription factors that may play a role in gene regulation in stroma cells, we performed comparative gene expression analysis of fibroblastic NIH3T3 cells, unable to support hematopoiesis in vitro, and OP-9 stroma cells, highly efficient in this regard. These experiments revealed that transcription factors of the early B cell factor (EBF) family were highly expressed in OP-9 cells as compared with the NIH3T3 cells. To identify potential targets genes for EBF proteins in stroma cells, we overexpressed EBF in fibroblasts and analyzed the pattern of induced genes by microarray analysis. This revealed that EBF was able to up-regulate expression of among others the Cxcl12, Ccl9, and Periostin genes. The identification of relevant promoters revealed that they all contained functional EBF binding sites able to interact with EBF in OP-9 cells. Furthermore, ectopic expression of a dominant negative EBF protein or antisense EBF-1 RNA in OP-9 stroma cells resulted in reduced expression of these target genes. These data suggest that EBF proteins might have dual roles in hematopoiesis acting both as intrinsic regulators of B-lymphopoiesis and as regulators of genes in bone marrow stroma cells. © 2007 by The American Society for Biochemistry and Molecular Biology, Inc.
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| 10. |
- Magnusson, Mattias, et al.
(författare)
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HOXA10 is a critical regulator for hematopoietic stem cells and erythroid/megakaryocyte development
- 2007
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 109:9, s. 3687-3696
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Tidskriftsartikel (refereegranskat)abstract
- The Homeobox (Hox) transcription factors are important regulators of normal and malignant hematopoiesis because they control proliferation, differentiation, and self-renewal of hematopoietic cells at different levels of the hematopoietic hierarchy. In transgenic mice we show that the expression of HOXA10 is tightly regulated by doxycycline. Intermediate concentrations of HOXA10 induced a 15-fold increase in the repopulating capacity of hematopoietic stem cells (HSCs) after 13 days of in vitro culture. Notably, the proliferation induction of HSC by HOXA10 was dependent on the HOXA10 concentration, because high levels of HOXA10 had no effect on HSC proliferation. Furthermore, high levels of HOXA10 blocked erythroid and megakaryocyte development, demonstrating that tight regulation of HOXA10 is critical for normal development of the erythroid and megakaryocytic lineages. The HOXA10-mediated effects on hematopoietic cells were associated with altered expression of genes that govern stem-cell self-renewal and lineage commitment (eg, hepatic leukemia factor [HlF], Dickkopf-1 [Dkk-1], growth factor independent-1 [Gfi-1], and Gata-1). Interestingly, binding sites for HOXA10 were found in HLF, Dkk-1, and Gata-1, and Dkk-1 and Gfi-1 were transcriptionally activated by HOXA10. These findings reveal novel molecular pathways that act downstream of HOXA10 and identify HOXA10 as a master regulator of postnatal hematopoietic development.
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| 11. |
- Månsson, Robert, et al.
(författare)
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B-lineage commitment prior to surface expression of B220 and CD19 on hematopoietic progenitor cells
- 2008
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 112:4, s. 1048-1055
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Tidskriftsartikel (refereegranskat)abstract
- Commitment of hematopoietic progenitor cells to B-lymphoid cell fate has been suggested to coincide with the development of PAX5-expressing B220 +CD19+ pro-B cells. We have used a transgenic reporter mouse, expressing human CD25 under the control of the B-lineage- restricted IgII1 (λ5) promoter to investigate the lineage potential of early progenitor cells in the bone marrow. This strategy allowed us to identify a reporter expressing LIN-B220- CD19-CD127 +FLT3+ SCA1lowKITlow population that displays a lack of myeloid and a 90% reduction in in vitro T-cell potential compared with its reporter-negative counterpart. Gene expression analysis demonstrated that these lineage-restricted cells express B- lineage-associated genes to levels comparable with that observed in pro-B cells. These data suggest that B-lineage commitment can occur before the expression of B220 and CD19. © 2008 by The American Society of Hematology.
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| 12. |
- Månsson, Robert, et al.
(författare)
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Molecular evidence for hierarchical transcriptional lineage priming in fetal and adult stem cells and multipotent progenitors
- 2007
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Ingår i: Immunity. - : Elsevier BV. - 1074-7613 .- 1097-4180. ; 26:4, s. 407-419
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies implicated the existence of adult lymphoid-primed multipotent progenitors (LMPPs) with little or no megakaryocyte-erythroid potential, questioning common myeloid and lymphoid progenitors as obligate intermediates in hematopoietic stem cell (HSC) lineage commitment. However, the existence of LMPPs remains contentious. Herein, global and single-cell analyses revealed a hierarchical organization of transcriptional lineage programs, with downregulation of megakaryocyte-erythroid genes from HSCs to LMPPs, sustained granulocyte-monocyte priming, and upregulation of common lymphoid (but not B and T cell-specific) genes. These biological and molecular relationships, implicating almost mutual exclusion of megakaryocyte-erythroid and lymphoid pathways, are established already in fetal hematopoiesis, as evidenced by existence of LMPPs in fetal liver. The identification of LMPPs and hierarchically ordered transcriptional activation and downregulation of distinct lineage programs is compatible with a model for HSC lineage commitment in which the probability for undergoing different lineage commitment fates changes gradually when progressing from HSCs to LMPPs.
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| 13. |
- Nilsson, Lars, et al.
(författare)
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The molecular signature of MDS stem cells supports a stem-cell origin of 5q-myelodysplastic syndromes
- 2007
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 110:8, s. 3005-3014
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Tidskriftsartikel (refereegranskat)abstract
- Global gene expression profiling of highly purified 5q-deleted CD34+CD38–Thy1+ cells in 5q– myelodysplastic syndromes (MDSs) supported that they might originate from and outcompete normal CD34+CD38–Thy1+ hematopoietic stem cells. Few but distinct differences in gene expression distinguished MDS and normal stem cells. Expression of BMI1, encoding a critical regulator of self-renewal, was up-regulated in 5q– stem cells. Whereas multiple previous MDS genetic screens failed to identify altered expression of the gene encoding the myeloid transcription factor CEBPA, stage-specific and extensive down-regulation of CEBPA was specifically observed in MDS progenitors. These studies establish the importance of molecular characterization of distinct stages of cancer stem and progenitor cells to enhance the resolution of stage-specific dysregulated gene expression.
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| 14. |
- Pron, C. J., et al.
(författare)
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Deciphering developmental stages of adult myelopoiesis
- 2008
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Ingår i: Cell Cycle. - 1538-4101 .- 1551-4005. ; 7:6, s. 706-713
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Tidskriftsartikel (refereegranskat)abstract
- The ability to subfractionate minor cellular subsets by multiparameter flow cytometry and to evaluate such cells for functional properties has been used to ascertain lineal relationships and detail developmental hierarchies in the hematopoietic system for more than 20 years. However, steady advances in technology combined with the use of novel cell surface markers continues to redefine the developmental landscape as novel subpopulations are purified and characterized. We recently used such an approach to stage progenitor cell hierarchy involved in myeloid development with the use of two markers, Slamf1 and Endoglin that have recently been shown to be associated with hematopoietic stem cells. Here, we provide additional characterization of these cellular subsets to further refine their developmental potential. Little or no alterations in lineage potential were observed in these subsets when evaluated in a BCL2 transgenic setting or in response to various growth factor combinations, although BCL2 significantly enhanced their in vitro readout. Gene expression patterns of functionally opposing transcription factors that are known to play key roles for the appropriate development into separate myeloid lineages were associated with the functional activity of prospectively isolated subsets. Multiple genes traditionally associated with early lymphopoiesis were observed in early candidate granulocyte/monocyte, but not early megakaryocytic and/or erythroid progenitor cells. When functionally evaluated, such early granulocyte/monocyte precursors displayed a latent lymphoid activity, which was pronounced in subsets bearing high expression of the tyrosine kinase receptor FLT3.
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| 15. |
- Zandi, Sasan, 1976-, et al.
(författare)
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EBF1 is essential for B-lineage priming and establishment of a transcription factor network in common lymphoid progenitors
- 2008
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Ingår i: Journal of Immunology. - 0022-1767 .- 1550-6606. ; 181:5, s. 3364-3372
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Tidskriftsartikel (refereegranskat)abstract
- Development of B-lymphoid cells in the bone marrow is a process under strict control of a hierarchy of transcription factors. To understand the development of a B-lymphoid-restricted functional network of transcription factors, we have investigated the cell autonomous role of the transcription factor EBF1 in early B cell development. This revealed that even though transplanted EBF1-deficient fetal liver cells were able to generate common lymphoid progenitors (CLPs) as well as B220(+)CD43(+)AA4.1(+) candidate precursor B cells, none of these populations showed signs of B lineage priming. The isolated CLPs were able to generate T lymphocytes in vitro supporting the idea that the phenotype of EBF1-deficient mice is restricted to the development of the B lineage. Furthermore, EBF deficient CLPs displayed a reduction in Ig H chain recombination as compared with their wild-type counterpart and essentially lacked transcription of B-lineage-associated genes. Among the genes displaying reduced expression in the EBF1 deficient CLPs were the transcription factors Pax5, Pou2af1 (OcaB), and FoxO1 that all appear to be direct genetic targets for EBF1 because their promoters contained functional binding sites for this factor. This leads us to suggest that EBF1 regulates a transcription factor network crucial for B lineage commitment.
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