| 1. |
- Warsi, Sarah, et al.
(författare)
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Schlafen2 is a regulator of quiescence in adult murine hematopoietic stem cells
- 2022
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Ingår i: Haematologica. - : Ferrata Storti Foundation (Haematologica). - 0390-6078 .- 1592-8721. ; 107:12, s. 2884-2896
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Tidskriftsartikel (refereegranskat)abstract
- Even though hematopoietic stem cells (HSC) are characterized by their ability to self-renew and differentiate, they primarily reside in quiescence. Despite the immense importance of this quiescent state, its maintenance and regulation is still incompletely understood. Schlafen2 (Slfn2) is a cytoplasmic protein known to be involved in cell proliferation, differentiation, quiescence, interferon response, and regulation of the immune system. Interestingly, Slfn2 is highly expressed in primitive hematopoietic cells. In order to investigate the role of Slfn2 in the regulation of HSC we have studied HSC function in the elektra mouse model, where the elektra allele of the Slfn2 gene contains a point mutation causing loss of function of the Slfn2 protein. We found that homozygosity for the elektra allele caused a decrease of primitive hematopoietic compartments in murine bone marrow. We further found that transplantation of elektra bone marrow and purified HSC resulted in a significantly reduced regenerative capacity of HSC in competitive transplantation settings. Importantly, we found that a significantly higher fraction of elektra HSC (as compared to wild-type HSC) were actively cycling, suggesting that the mutation in Slfn2 increases HSC proliferation. This additionally caused an increased amount of apoptotic stem and progenitor cells. Taken together, our findings demonstrate that dysregulation of Slfn2 results in a functional deficiency of primitive hematopoietic cells, which is particularly reflected by a drastically impaired ability to reconstitute the hematopoietic system following transplantation and an increase in HSC proliferation. This study thus identifies Slfn2 as a novel and critical regulator of adult HSC and HSC quiescence.
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| 2. |
- Billing, Matilda, et al.
(författare)
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A network including TGFβ/Smad4, Gata2 and p57 regulates proliferation of mouse hematopoietic progenitor cells.
- 2016
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Ingår i: Experimental Hematology. - : Elsevier BV. - 1873-2399 .- 0301-472X. ; 44:5, s. 399-409
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Tidskriftsartikel (refereegranskat)abstract
- Transforming growth factor-β (TGFβ) is a potent inhibitor of hematopoietic stem and progenitor cell proliferation. However, the precise mechanism for this effect is unknown. Here, we have identified the transcription factor Gata2, previously described as an important regulator of hematopoietic stem cell (HSC) function, as an early and direct target gene for TGFβ-induced Smad signaling in hematopoietic progenitor cells. We also report that Gata2 is involved in mediating a significant part of the TGFβ response in primitive hematopoietic cells. Interestingly, the cell cycle regulator and TGFβ signaling effector molecule p57 was found to be upregulated as a secondary response to TGFβ. We observed Gata2 binding upstream of the p57 genomic locus, and importantly loss of Gata2 abolished TGFβ-stimulated induction of p57 as well as the resulting growth arrest of hematopoietic progenitors. Our results connect key molecules involved in HSC self-renewal and reveal a functionally relevant network regulating proliferation of primitive hematopoietic cells.
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| 3. |
- Billing, Matilda, et al.
(författare)
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Signaling via Smad2 and Smad3 is dispensable for adult murine hematopoietic stem cell function in vivo
- 2017
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Ingår i: Experimental Hematology. - : Elsevier BV. - 0301-472X.
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Tidskriftsartikel (refereegranskat)abstract
- Transforming growth factor-β (TGFβ) is a member of a large family of polypeptide growth factors. TGFβ signals mainly through the intracellular proteins Smad2 and Smad3, which are highly similar in amino acid sequence identity. A number of studies have shown that these proteins, dependent on context, have distinct roles in the TGFβ signaling pathway. TGFβ is one of the most potent inhibitors of hematopoietic stem and progenitor cell proliferation in vitro, but its role in hematopoiesis in vivo is still being determined. To circumvent possible redundancies at the receptor level and to address specifically the role of the Smad circuitry downstream of TGFβ and activin in hematopoiesis, we studied the effect of genetically deleting both Smad2 and Smad3 in adult murine hematopoietic cells. Indeed, TGFβ signaling is impaired in vitro in primitive bone marrow (BM) cells of Smad2 and Smad3 single knockout models. However, blood parameters appear normal under steady state and in the transplantation setting. Interestingly, upon deletion of both Smad2 and Smad3 in vivo, mice quickly develop a lethal inflammatory disease, suggesting that activin/TGFβ signaling is crucial for immune cell homeostasis in the adult context. Furthermore, concurrent deletion of Smad2 and Smad3 in BM cells in immune-deficient nude mice did not result in any significant alterations of the hematopoietic system. Our findings suggest that Smad2 and Smad3 function to mediate crucial aspects of the immunoregulatory properties of TGFβ, but are dispensable for any effect that TGFβ has on primitive hematopoietic cells in vivo.
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| 4. |
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| 5. |
- Halvarsson, Camilla, 1985-, et al.
(författare)
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Putative Role of Nuclear Factor-Kappa B But Not Hypoxia-Inducible Factor-1α in Hypoxia-Dependent Regulation of Oxidative Stress in Hematopoietic Stem and Progenitor Cells
- 2019
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Ingår i: Antioxidants and Redox Signaling. - : Mary Ann Liebert. - 1523-0864 .- 1557-7716. ; 31:3, s. 211-226
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Adaptation to low oxygen of hematopoietic stem cells (HSCs) in the bone marrow has been demonstrated to depend on the activation of hypoxia-inducible factor (HIF)-1α as well as the limited production of reactive oxygen species (ROS). In this study, we aimed at determining whether HIF-1α is involved in protecting HSCs from ROS.Results: Oxidative stress was induced by DL-buthionine-(S,R)-sulfoximine (BSO)-treatment, which increases the mitochondrial ROS level. Hypoxia rescued Lineage-Sca-1+c-kit+ (LSK) cells from BSO-induced apoptosis, whereas cells succumbed to apoptosis in normoxia. Apoptosis in normoxia was inhibited with the antioxidant N-acetyl-L-cysteine or by overexpression of anti-apoptotic BCL-2. Moreover, stabilized expression of oxygen-insensitive HIFs could not protect LSK cells from oxidative stress-induced apoptosis at normoxia, neither could short hairpin RNA to Hif-1α inhibit the protective effects by hypoxia in LSK cells. Likewise, BSO treatment of LSK cells from Hif-1α knockout mice did not suppress the effects seen in hypoxia. Microarray analysis identified the nuclear factor-kappa B (NF-κB) pathway as a pathway induced by hypoxia. By using NF-κB lentiviral construct and DNA-binding assay, we found increased NF-κB activity in cells cultured in hypoxia compared with normoxia. Using an inhibitor against NF-κB activation, we could confirm the involvement of NF-κB signaling as BSO-mediated cell death was significantly increased in hypoxia after adding the inhibitor.Innovation: HIF-1α is not involved in protecting HSCs and progenitors to elevated levels of ROS on glutathione depletion during hypoxic conditions.Conclusion: The study proposes a putative role of NF-κB signaling as a hypoxia-induced regulator in early hematopoietic cells.
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| 6. |
- Karlsson, Göran, et al.
(författare)
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The Tetraspanin CD9 Affords High-Purity Capture of All Murine Hematopoietic Stem Cells
- 2013
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 4:4, s. 642-648
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Tidskriftsartikel (refereegranskat)abstract
- Prospective isolation is critical for understanding the cellular and molecular aspects of stem cell heterogeneity. Here, we identify the cell surface antigen CD9 as a positive marker that provides a simple alternative for hematopoietic stem cell isolation at high purity. Crucially, CD9 affords the capture of all hematopoietic stem cells in murine bone marrow in the absence of contaminating populations that lack authentic stem cell function. Using CD9 as a tool to subdivide hematopoietic stem-cell-containing populations, we provide evidence for heterogeneity at the cellular, functional, and molecular levels.
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| 7. |
- Miharada, Kenichi, et al.
(författare)
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Cripto Regulates Hematopoietic Stem Cells as a Hypoxic-Niche-Related Factor through Cell Surface Receptor GRP78.
- 2011
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Ingår i: Cell Stem Cell. - : Elsevier BV. - 1934-5909. ; 9:4, s. 330-344
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Tidskriftsartikel (refereegranskat)abstract
- Hematopoietic stem cells (HSCs) are maintained in hypoxic niches in endosteal regions of bones. Here we demonstrate that Cripto and its receptor GRP78 are important regulators of HSCs in the niche. Flow cytometry analyses revealed two distinct subpopulations of CD34(-)KSL cells based on the expression of GRP78, and these populations showed different reconstitution potential in transplantation assays. GRP78(+)HSCs mainly reside in the endosteal area, are more hypoxic, and exhibit a lower mitochondrial potential, and their HSC capacity was maintained in vitro by Cripto through induction of higher glycolytic activity. Additionally, HIF-1α KO mice have decreased numbers of GRP78(+)HSCs and reduced expression of Cripto in the endosteal niche. Furthermore, blocking GRP78 induced a movement of HSCs from the endosteal to the central marrow area. These data suggest that Cripto/GRP78 signaling is an important pathway that regulates HSC quiescence and maintains HSCs in hypoxia as an intermediary of HIF-1α.
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| 8. |
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| 9. |
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| 10. |
- Miharada, Kenichi, et al.
(författare)
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Hematopoietic stem cells are regulated by Cripto, as an intermediary of HIF-1α in the hypoxic bone marrow niche.
- 2012
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Ingår i: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923. ; 1266:1, s. 55-62
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Tidskriftsartikel (refereegranskat)abstract
- Cripto has been known as an embryonic stem (ES)- or tumor-related soluble/cell membrane protein. In this study, we demonstrated that Cripto has a role as an important regulatory factor for hematopoietic stem cells (HSCs). Recombinant Cripto sustained the reconstitution ability of HSCs in vitro. Flow cytometry analysis uncovered that GRP78, one of the candidate receptors for Cripto, was expressed on a subset of HSCs and could distinguish dormant/myeloid-biased HSCs and active/lymphoid-biased HSCs. Cripto is expressed in hypoxic endosteal niche cells where GRP78(+) HSCs mainly reside. Proteomics analysis revealed that Cripto-GRP78 binding stimulates glycolytic metabolism-related proteins and results in lower mitochondrial potential in HSCs. Furthermore, conditional knockout mice for HIF-1α, a master regulator of hypoxic responses, showed reduced Cripto expression and decreased GRP78(+) HSCs in the endosteal niche area. Thus, Cripto-GRP78 is a novel HSC regulatory signal mainly working in the hypoxic niche.
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