| 1. |
- Yang, W., et al.
(författare)
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Enhancing Hematopoiesis from Murine Embryonic Stem Cells through MLL1-Induced Activation of a Rac/Rho/Integrin Signaling Axis
- 2020
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Ingår i: Stem Cell Reports. - : Elsevier BV. - 2213-6711. ; 14:2, s. 285-299
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Tidskriftsartikel (refereegranskat)abstract
- The Mixed Lineage Leukemia (MLL1, KMT2A) gene is critical for development and maintenance of hematopoietic stem cells (HSCs), however, whether this protein is limiting for HSC development is unknown due to lack of physiologic model systems. Here, we develop an MLL1-inducible embryonic stem cell (ESC) system and show that induction of wild-type MLL1 during ESC differentiation selectively increases hematopoietic potential from a transitional c-Kit(+)/Cd41(+) population in the embryoid body and also at sites of hematopoiesis in embryos. Single-cell sequencing analysis illustrates inherent heterogeneity of the c-Kit(+)/Cd41(+) population and demonstrates that MLL1 induction shifts its composition toward multilineage hematopoietic identities. Surprisingly, this does not occur through increasing Hox or other canonical MLL1 targets but through an enhanced Rac/Rho/integrin signaling state, which increases responsiveness to Vla4 ligands and enhances hematopoietic commitment. Together, our data implicate a Rac/Rho/integrin signaling axis in the endothelial to hematopoietic transition and demonstrate that MLL1 actives this axis.
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| 2. |
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| 3. |
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| 4. |
- Bhattacharya, D, et al.
(författare)
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Rapid lymphocyte reconstitution of unconditioned immunodeficient mice with non-self-renewing multipotent hematopoietic progenitors
- 2006
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Ingår i: Cell Cycle. - 1551-4005. ; 5:11, s. 1135-1139
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Tidskriftsartikel (refereegranskat)abstract
- The replacement of abnormal hematopoietic stem cells (HSCs) with normal transplanted HSCs can correct a wide range of hematologic disorders. Here, we provide evidence that transplantation of more differentiated progenitor cells can be used to more rapidly correct lymphoid deficiencies in unconditioned immunocompromised mice. Transplantation of flk2+ multipotent progenitors led to robust B and T cell reconstitution that was maintained for at least 16 weeks. Antigenic challenge at 16 weeks post-transplantation revealed that reconstituted lymphocytes maintained a functional repertoire. In contrast to the persistent lymphocytic engraftment, myeloid chimerism was lost by 12 weeks post-transplantation consistent with the fact that flk2+ progenitors are non-self-renewing. Thus, while more differentiated progenitors are capable of rescuing lymphoid deficiencies, transplantation of HSCs must be used for the correction of non-lymphoid disorders, and, we propose, very long-term immune reconstitution. Based on recent evidence, we discuss novel strategies to achieve the replacement of abnormal HSCs without the use of cytotoxic conditioning regimens.
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| 5. |
- Jaako, P., et al.
(författare)
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Induction of the 5S RNP-Mdm2-p53 ribosomal stress pathway delays the initiation but fails to eradicate established murine acute myeloid leukemia
- 2017
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Ingår i: Leukemia. - : NATURE PUBLISHING GROUP. - 0887-6924 .- 1476-5551. ; 31:1, s. 213-221
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Tidskriftsartikel (refereegranskat)abstract
- Mutations resulting in constitutive activation of signaling pathways that regulate ribosome biogenesis are among the most common genetic events in acute myeloid leukemia (AML). However, whether ribosome biogenesis presents as a therapeutic target to treat AML remains unexplored. Perturbations in ribosome biogenesis trigger the 5S ribonucleoprotein particle (RNP)-Mdm2-p53 ribosomal stress pathway, and induction of this pathway has been shown to have therapeutic efficacy in Myc-driven lymphoma. In the current study we address the physiological and therapeutic role of the 5S RNP-Mdm2-p53 pathway in AML. By utilizing mice that have defective ribosome biogenesis due to downregulation of ribosomal protein S19 (Rps19), we demonstrate that induction of the 5S RNP-Mdm2-p53 pathway significantly delays the initiation of AML. However, even a severe Rps19 deficiency that normally results in acute bone marrow failure has no consistent efficacy on already established disease. Finally, by using mice that harbor a mutation in the Mdm2 gene disrupting its binding to 5S RNP, we show that loss of the 5S RNP-Mdm2-p53 pathway is dispensable for development of AML. Our study suggests that induction of the 5S RNP-Mdm2-p53 ribosomal stress pathway holds limited potential as a single-agent therapy in the treatment of AML.
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| 6. |
- Morcos, M. N. F., et al.
(författare)
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Continuous mitotic activity of primitive hematopoietic stem cells in adult mice
- 2020
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 217:6
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Tidskriftsartikel (refereegranskat)abstract
- The proliferative activity of aging hematopoietic stem cells (HSCs) is controversially discussed. Inducible fluorescent histone 2B fusion protein (H2B-FP) transgenic mice are important tools for tracking the mitotic history of murine HSCs in label dilution experiments. A recent study proposed that primitive HSCs symmetrically divide only four times to then enter permanent quiescence. We observed that background fluorescence due to leaky H2B-FP expression, occurring in all H2B-FP transgenes independent of label induction, accumulated with age in HSCs with high repopulation potential. We argue that this background had been misinterpreted as stable retention of induced label. We found cell division-independent half-lives of H2B-FPs to be short, which had led to overestimation of HSC divisional activity. Our data do not support abrupt entry of HSCs into permanent quiescence or sudden loss of regeneration potential after four divisions, but show that primitive HSCs of adult mice continue to cycle rarely.
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| 7. |
- 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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| 8. |
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| 9. |
- Säwen, Petter, et al.
(författare)
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Murine HSCs contribute actively to native hematopoiesis but with reduced differentiation capacity upon aging
- 2018
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Ingår i: Elife. - 2050-084X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- A hallmark of adult hematopoiesis is the continuous replacement of blood cells with limited lifespans. While active hematopoietic stem cell (HSC) contribution to multilineage hematopoiesis is the foundation of clinical HSC transplantation, recent reports have questioned the physiological contribution of HSCs to normal/steady-state adult hematopoiesis. Here, we use inducible lineage tracing from genetically marked adult HSCs and reveal robust HSC-derived multilineage hematopoiesis. This commences via defined progenitor cells, but varies substantially in between different hematopoietic lineages. By contrast, adult HSC contribution to hematopoietic cells with proposed fetal origins is neglible. Finally, we establish that the HSC contribution to multilineage hematopoiesis declines with increasing age. Therefore, while HSCs are active contributors to native adult hematopoiesis, it appears that the numerical increase of HSCs is a physiologically relevant compensatory mechanism to account for their reduced differentiation capacity with age.
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| 10. |
- Takahashi, M., et al.
(författare)
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Reconciling Flux Experiments for Quantitative Modeling of Normal and Malignant Hematopoietic Stem/Progenitor Dynamics
- 2021
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Ingår i: Stem Cell Reports. - : Elsevier BV. - 2213-6711. ; 16:4, s. 741-753
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Tidskriftsartikel (refereegranskat)abstract
- Hematopoiesis serves as a paradigm for how homeostasis is maintained within hierarchically organized cell populations. However, important questions remain as to the contribution of hematopoietic stem cells (HSCs) toward maintaining steady state hematopoiesis. A number of in vivo lineage labeling and propagation studies have given rise to contradictory interpretations, leaving key properties of stem cell function unresolved. Using processed flow cytometry data coupled with a biology-driven modeling approach, we show that in vivo flux experiments that come from different laboratories can all be reconciled into a single unifying model, even though they had previously been interpreted as being contradictory. We infer from comparative analysis that different transgenic models display distinct labeling efficiencies across a heterogeneous HSC pool, which we validate by marker gene expression associated with HSC function. Finally, we show how the unified model of HSC differentiation can be used to simulate clonal expansion in the early stages of leukemogenesis. © 2021 The Authors
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