The Role of Mel18 Overlaps with BMI1 In the Self-Renewal of Human Hematopoietic Stem Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2619-2619
Author(s):  
Yasmin Reyal ◽  
Dominique Bonnet
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Cord Blood ◽  
Conflicts Of Interest ◽  
Expression Patterns ◽  
Polycomb Group ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Starting Point

Abstract Abstract 2619 Complex mechanisms regulate the ability of hematopoietic stem cells (HSCs) to self-renew, some of which may be exploited by leukemic stem cells. BMI1, a member of the polycomb group (PcG) proteins is known to be a positive regulator of this process, largely by repressing the p16/INK4a locus. However the role of other PcG proteins is unclear. We initially screened HSCs and progenitor populations from umbilical cord blood (CB), for the expression patterns of a number of PcG genes. Levels of expression were heterogeneous, indicating that there may be different roles for different PcG in HSCs versus progenitors. As a starting point we have focused on Mel18 (PCGF2) as it has been suggested in murine hematopoiesis that it acts to counteract BMI1. Lineage negative CB cells were transduced with lentiviral vectors expressing shRNA against Mel18, BMI1 and a control sequence. Specific knockdown by these constructs was confirmed at the RNA level to be at least 80% for both genes and was verified at the protein level by Western blot. Our data indicates that knockdown of Mel18 impairs the proliferation of primitive cord blood cells in both stromal-dependent and -independent culture, in a similar manner to BMI1. Furthermore Mel18 deficiency impedes both primary and secondary colony formation of all myeloid lineages in methylcellulose. These findings have been confirmed in vivo with significant reduction in engraftment of CB lineage negative cells in NOD/SCID mice at twelve weeks. We are investigating whether over expression of Mel18 can rescue BMI1 deficient cells to establish if these homologous genes have redundant functions. The data so far suggests that BMI1 is not unique in its role in HSC self - renewal, and Mel18 may share overlapping functions. This highlights a possible difference between human and murine hematopoiesis. Moreover it is likely that other members of the PcG family are also important in human HSCs. It will be of interest to investigate whether like BMI1, they are also implicated in the maintenance of the leukemic stem cell. Disclosures: No relevant conflicts of interest to declare.

Tumor Suppressor Role of HIF-1alpha in Leukemia-Initiating Cells in Flt3-ITD-Induced Myeloproliferative Neoplasm

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3578-3578
Author(s):  
Talia Velasco ◽  
Jörg Cammenga
Keyword(s):  
Stem Cells ◽  
Tumor Suppressor ◽  
Hematopoietic Stem Cells ◽  
Myeloid Leukemia ◽  
Conflicts Of Interest ◽  
Myeloproliferative Neoplasm ◽  
Molecular Response ◽  
Self Renewal ◽  
Hematopoietic Stem

Abstract Hypoxia-induced signalling is a major regulator in normal and malignant hematopoiesis. The transcription factor HIF-1alpha plays a crucial role in the quiescence and self-renewal of hematopoietic stem cells as well as leukemia-initiating cells (LICs) of acute myeloid leukemia and chronic myeloid leukemia. Better understanding of the requirement of the molecular response to hypoxia in LICs could lead to new therapies targeting this pathway. We have therefore investigated the effect of HIF-1alpha loss on the phenotype and biology of FLT3-ITD induced myeloproliferative neoplasm (MPN). Using a combined transgenic mouse model (Mx1-Cre; Hif-1alphafl/fl; Flt3ITD/+) we showed that deletion of HIF-1alpha leads to a more severe MPN phenotype reflected by higher numbers of white blood cells and myeloid cells in peripheral blood, as well as a more severe splenomegaly. Loss of long-term hematopoietic stem cells (LT-HSCs: Lin- Sca1+ cKit+ CD48- CD150+) and increased number of lineage-restricted progenitors (Lin- Sca1+ cKit+ CD48+ CD150-) were the most pronounced effects on a cellular level upon the loss of HIF-1alpha. The proliferative effect of the HIF-1alpha loss was cell intrinsic and not at the expense of the ability of the LICs to self-renew because the disease was transplantable into secondary recipients recapitulating the same phenotype. Mice transplanted with FLT3-ITD induced MPN lacking HIF-1alpha succumbed to their disease (average survival of 35 weeks after transplant), while animals transplanted with MPN with wild-type HIF-1alpha suffered from MPN but did not die in the observation period of 60 weeks. These findings are in contrary to what has been previously described for the role of HIF-1alpha in leukemia initiating cells and lead us to propose that HIF-1alpha could act as a tumor suppressor gene, inhibiting proliferation in myeloid malignancies. Our results provide evidence that targeting HIF-1alpha can lead to disease progression of MPN while not affecting self-renewal of LICs. Disclosures No relevant conflicts of interest to declare.

GPI-80 Defines Self-Renewal Ability In Hematopoietic Stem Cells During Human Development

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4839-4839
Author(s):  
Sacha L. Prashad ◽  
Vincenzo Calvanese ◽  
Catherine Yao ◽  
Joshua Kaiser ◽  
Rajkumar Sasidharan ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Human Development ◽  
Conflicts Of Interest ◽  
Fetal Liver ◽  
Surface Protein ◽  
Surface Proteins ◽  
Proliferative Potential ◽  
Self Renewal ◽  
Hematopoietic Stem

Abstract Advances in pluripotent stem cell and reprogramming technologies have provided hope of generating transplantable hematopoietic stem cells (HSC) in culture. However, better understanding of the identity and regulatory mechanisms that define the self-renewing HSC during human development is required. We discovered that the glycophosphatidylinositol-anchored surface protein GPI-80 (Vanin-2), previously implicated in neutrophil diapedesis, distinguishes a functionally distinct subpopulation of human fetal hematopoietic stem and progenitor cells (HSPC) that possess self-renewal ability. CD34+CD90+CD38-GPI80+ HSPCs were the only population that could maintain proliferative potential and undifferentiated state in co-culture on supportive stroma, and displayed engraftment potential in sublethally irradiated NSG mice. GPI-80 expression also enabled tracking of human HSC during development as they migrate across fetal hematopoietic niches, including early fetal liver and bone marrow. Microarray analysis comparing CD34+CD90+CD38-GPI80+ HSPC to their immediate progeny (CD34+CD90+CD38-GPI80-) identified novel candidate self-renewal regulators. Knockdown of GPI80, or the top enriched transcripts encoding surface proteins (ITGAM) or transcription factors (HIF3a) documented the necessity of all three molecules in sustaining human fetal HSC self-renewal. These findings provide new insights to the poorly understood regulation of human HSC development and suggest that human fetal HSCs utilize common mechanisms with leukocytes to enable cell-cell interactions critical for HSC self-renewal. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Smad4 is critical for self-renewal of hematopoietic stem cells

2007 ◽  
Vol 204 (3) ◽  
pp. 467-474 ◽  
Author(s):  
Göran Karlsson ◽  
Ulrika Blank ◽  
Jennifer L. Moody ◽  
Mats Ehinger ◽  
Sofie Singbrant ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
In Vitro Proliferation ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Early Embryonic Lethality

Members of the transforming growth factor β (TGF-β) superfamily of growth factors have been shown to regulate the in vitro proliferation and maintenance of hematopoietic stem cells (HSCs). Working at a common level of convergence for all TGF-β superfamily signals, Smad4 is key in orchestrating these effects. The role of Smad4 in HSC function has remained elusive because of the early embryonic lethality of the conventional knockout. We clarify its role by using an inducible model of Smad4 deletion coupled with transplantation experiments. Remarkably, systemic induction of Smad4 deletion through activation of MxCre was incompatible with survival 4 wk after induction because of anemia and histopathological changes in the colonic mucosa. Isolation of Smad4 deletion to the hematopoietic system via several transplantation approaches demonstrated a role for Smad4 in the maintenance of HSC self-renewal and reconstituting capacity, leaving homing potential, viability, and differentiation intact. Furthermore, the observed down-regulation of notch1 and c-myc in Smad4−/− primitive cells places Smad4 within a network of genes involved in the regulation HSC renewal.

scholarly journals Microrna 199b Regulates Mouse Hematopoietic Stem Cells Maintenance

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3704-3704
Author(s):  
Aldona A Karaczyn ◽  
Edward Jachimowicz ◽  
Jaspreet S Kohli ◽  
Pradeep Sathyanarayana
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Conflicts Of Interest ◽  
Quiescent State ◽  
Differentiation Potential ◽  
Self Renewal ◽  
Hematopoietic Stem

The preservation of hematopoietic stem cell pool in bone marrow (BM) is crucial for sustained hematopoiesis in adults. Studies assessing adult hematopoietic stem cells functionality had been shown that for example loss of quiescence impairs hematopoietic stem cells maintenance. Although, miR-199b is frequently down-regulated in acute myeloid leukemia, its role in hematopoietic stem cells quiescence, self-renewal and differentiation is poorly understood. Our laboratory investigated the role of miR-199b in hematopoietic stem and progenitor cells (HSPCs) fate using miR-199b-5p global deletion mouse model. Characterization of miR-199b expression pattern among normal HSPC populations revealed that miR-199b is enriched in LT-HSCs and reduced upon myeloablative stress, suggesting its role in HSCs maintenance. Indeed, our results reveal that loss of miR-199b-5p results in imbalance between long-term hematopoietic stem cells (LT-HSCs), short-term hematopoietic stem cells (ST-HSCs) and multipotent progenitors (MMPs) pool. We found that during homeostasis, miR-199b-null HSCs have reduced capacity to maintain quiescent state and exhibit cell-cycle deregulation. Cell cycle analyses showed that attenuation of miR-199b controls HSCs pool, causing defects in G1-S transition of cell cycle, without significant changes in apoptosis. This might be due to increased differentiation of LT-HSCs into MPPs. Indeed, cell differentiation assay in vitro showed that FACS-sorted LT-HSCs (LineagenegSca1posc-Kitpos CD48neg CD150pos) lacking miR-199b have increased differentiation potential into MPP in the presence of early cytokines. In addition, differentiation assays in vitro in FACS-sorted LSK population of 52 weeks old miR-199b KO mice revealed that loss of miR-199b promotes accumulation of GMP-like progenitors but decreases lymphoid differentiation, suggesting that miR199b may regulate age-related pathway. We used non-competitive repopulation studies to show that overall BM donor cellularity was markedly elevated in the absence of miR-199b among HSPCs, committed progenitors and mature myeloid but not lymphoid cell compartments. This may suggest that miR-199b-null LT-HSC render enhanced self-renewal capacity upon regeneration demand yet promoting myeloid reconstitution. Moreover, when we challenged the self-renewal potential of miR-199b-null LT-HSC by a secondary BM transplantation of unfractionated BM cells from primary recipients into secondary hosts, changes in PB reconstitution were dramatic. Gating for HSPCs populations in the BM of secondary recipients in 24 weeks after BMT revealed that levels of LT-HSC were similar between recipients reconstituted with wild-type and miR-199b-KO chimeras, whereas miR-199b-null HSCs contributed relatively more into MPPs. Our data identify that attenuation of miR-199b leads to loss of quiescence and premature differentiation of HSCs. These findings indicate that loss of miR-199b promotes signals that govern differentiation of LT-HSC to MPP leading to accumulation of highly proliferative progenitors during long-term reconstitution. Hematopoietic regeneration via repopulation studies also revealed that miR-199b-deficient HSPCs have a lineage skewing potential toward myeloid lineage or clonal myeloid bias, a hallmark of aging HSCs, implicating a regulatory role for miR-199b in hematopoietic aging. Disclosures No relevant conflicts of interest to declare.

scholarly journals Hematopoietic stem cells fail to regenerate following inflammatory challenge

2020 ◽  
Author(s):  
Ruzhica Bogeska ◽  
Paul Kaschutnig ◽  
Malak Fawaz ◽  
Ana-Matea Mikecin ◽  
Marleen Büchler-Schäff ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Recovery Period ◽  
Cumulative Impact ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Inflammatory Stress ◽  
Kinetics Of

AbstractHematopoietic stem cells (HSCs) are canonically defined by their capacity to maintain the HSC pool via self-renewal divisions. However, accumulating evidence suggests that HSC function is instead preserved by sustaining long-term quiescence. Here, we study the kinetics of HSC recovery in mice, following an inflammatory challenge that induces HSCs to exit dormancy. Repeated inflammatory challenge resulted in a progressive depletion of functional HSCs, with no sign of later recovery. Underlying this observation, label retention experiments demonstrated that self-renewal divisions were absent or extremely rare during challenge, as well as during any subsequent recovery period. While depletion of functional HSCs held no immediate consequences, young mice exposed to inflammatory challenge developed blood and bone marrow hypocellularity in old age, similar to elderly humans. The progressive, irreversible attrition of HSC function demonstrates that discreet instances of inflammatory stress can have an irreversible and therefore cumulative impact on HSC function, even when separated by several months. These findings have important implications for our understanding of the role of inflammation as a mediator of dysfunctional tissue maintenance and regeneration during ageing.

scholarly journals Mitochondria in the maintenance of hematopoietic stem cells: new perspectives and opportunities

Blood ◽  
2019 ◽  
Vol 133 (18) ◽  
pp. 1943-1952 ◽  
Author(s):  
Marie-Dominique Filippi ◽  
Saghi Ghaffari
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Blood Cells ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Hematopoietic System ◽  
Cellular Energy ◽  
Cell Pool ◽  
Stem Cell Pool

Abstract The hematopoietic system produces new blood cells throughout life. Mature blood cells all derived from a pool of rare long-lived hematopoietic stem cells (HSCs) that are mostly quiescent but occasionally divide and self-renew to maintain the stem cell pool and to insure the continuous replenishment of blood cells. Mitochondria have recently emerged as critical not only for HSC differentiation and commitment but also for HSC homeostasis. Mitochondria are dynamic organelles that orchestrate a number of fundamental metabolic and signaling processes, producing most of the cellular energy via oxidative phosphorylation. HSCs have a relatively high amount of mitochondria that are mostly inactive. Here, we review recent advances in our understanding of the role of mitochondria in HSC homeostasis and discuss, among other topics, how mitochondrial dynamism and quality control might be implicated in HSC fate, self-renewal, and regenerative potential.

scholarly journals Mitochondrial Role in Stemness and Differentiation of Hematopoietic Stem Cells

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Luena Papa ◽  
Mansour Djedaini ◽  
Ronald Hoffman
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Energy Production ◽  
Ex Vivo ◽  
Mitochondrial Activity ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Hypoxic Environment

Quiescent and self-renewing hematopoietic stem cells (HSCs) rely on glycolysis rather than on mitochondrial oxidative phosphorylation (OxPHOS) for energy production. HSC reliance on glycolysis is considered an adaptation to the hypoxic environment of the bone marrow (BM) and reflects the low energetic demands of HSCs. Metabolic rewiring from glycolysis to mitochondrial-based energy generation accompanies HSC differentiation and lineage commitment. Recent evidence, however, highlights that alterations in mitochondrial metabolism and activity are not simply passive consequences but active drivers of HSC fate decisions. Modulation of mitochondrial activity and metabolism is therefore critical for maintaining the self-renewal potential of primitive HSCs and might be beneficial for ex vivo expansion of transplantable HSCs. In this review, we emphasize recent advances in the emerging role of mitochondria in hematopoiesis, cellular reprograming, and HSC fate decisions.

Identification of Single Human Hematopoietic Stem Cells Capable of Long-Term Multilineage Engraftment and Self-Renewal.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 816-816
Author(s):  
Faiyaz Notta ◽  
Sergei Doulatov ◽  
John E. Dick
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Cord Blood ◽  
Conflicts Of Interest ◽  
Single Cells ◽  
Human Cord Blood ◽  
Hematopoietic Stem ◽  
Human Hscs ◽  
Insight Into

Abstract Abstract 816 A fundamental tenet that has guided our insight into the biology of hematopoietic stem cells (HSCs) over the past 50 years is the principle that an HSC can only be assayed by functional repopulation of an irradiated host1. In its strictest definition, only a HSC can provide long-term reconstitution of all the major lineages following single cell transplantation. However, the existing strategies for human HSC isolation lack quantitation and do not submit to this rigorous standard, thus precluding further biological analysis. Here, we report the prospective and quantitative analysis of human cord blood (CB) HSCs transplanted into female NOD/SCID/IL-2Rgcnull mice. We identify integrin a6 (CD49f) as a novel marker of cord blood (CB) HSCs and report that single Lin-CD34+CD38-CD90+CD45RA-RholoCD49fhi cells can reconstitute myeloid, B-, and T-cell lineages for 18 weeks. 5 of 29 mice transplanted with single cells gave rise to human cells indicating that approximately 20% of cells in this fraction are HSCs. This advance finally enables utilization of near-homogeneous populations of human HSCs to gain insight into their biology and to harness them for stem cell-based therapeutics. Disclosures: No relevant conflicts of interest to declare.

Evidence That High-Mobility Group A2 (Hmga2) Expression Contributes to the Ontogeny-Dependent Properties of Fetal Hematopoietic Stem Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2634-2634
Author(s):  
Michael R. Copley ◽  
David G. Kent ◽  
Claudia Benz ◽  
Keegan M. Rowe ◽  
Stefan H. Woehrer ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Conflicts Of Interest ◽  
Fetal Liver ◽  
Rapid Expansion ◽  
High Expression ◽  
Primary Host ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Renewal Program

Abstract Abstract 2634 Fetal and early neonatal hematopoietic stem cells (HSCs) are distinct from their adult counterparts by their rapid turnover and expansion rates in vivo. However, the mechanisms underlying the regulation of these properties are poorly understood. In previous studies using serial limiting-dilution competitive repopulating transplant assays, our lab has shown that the rapid expansion phenotype of fetal HSCs is at least partially intrinsically determined since significantly more daughter HSCs are produced from fetal as compared to adult HSCs when similar numbers are transplanted into the same type of irradiated adult host. Additionally, we have observed a conversion of fetal HSCs to the adult regeneration phenotype that occurs within six weeks of transplantation in the primary host. To facilitate a comparison of highly-purified subsets of fetal and adult HSCs identified by an identical phenotype, we adopted the use of the CD45+EPCR+CD150+CD48− (E-SLAM) phenotype which we found gave HSC purities of 20–50% for hematopoietic tissues from early fetal to aged adulthood. We then used comparative gene expression analysis to identify candidate regulators of the fetal HSC high self-renewal program. This gave 20 candidate genes whose transcript levels were measured by quantitative real time PCR in E-SLAM cells isolated from E14.5 fetal liver (FL) and adult bone marrow (ABM). Of these genes only Hmga2 and Smarcc1 showed significant differences (p<.05) in expression between fetal and adult HSCs and only Hmga2 maintained this differential expression when the same cells were stimulated to divide for 48 hrs in vitro. To test the hypothesis that high expression of Hmga2 is a necessary and sufficient factor in determining the fetal HSC self-renewal program, purified adult E-SLAM HSCs were transduced with Hmga2-overexpressing or control lentiviruses and the kinetics of transduced vs untransduced hematopoietic cells in a congenic serial-transplantation model were then analyzed. Interestingly, when BM cells from the primary repopulated mice (transplanted 6-weeks earlier) were injected into secondary animals and the peripheral blood was analyzed for donor-type %Y/GFP chimerism, the Hmga2-overexpressing cells were observed to have a competititve advantage and exhibited an ∼6-fold expansion relative to the untransduced cells. In contrast, the control virus-infected BM cells were found to be equally competitive. These findings support the hypothesis that high expression of Hmga2 may be a critical mediator of the high self-renewal phenotype of fetal HSCs. Disclosures: No relevant conflicts of interest to declare.

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