A Critical Role for the Retinoblastoma Tumor Suppressor Gene in Hematopoietic Stem Cells.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2548-2548
Author(s):  
Hartmut Geiger ◽  
Marie-Dominique Filippi ◽  
Theodosia A. Kalfa ◽  
Deidre Daria
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Function ◽  
Fetal Liver ◽  
Critical Role ◽  
Lymphoid Cells ◽  
Hematopoietic Stem ◽  
Retinoblastoma Tumor Suppressor ◽  
Retinoblastoma Tumor

Abstract The retinoblastoma tumor suppressor protein (RB) plays important roles in the control of the cell cycle, DNA-damage checkpoint, differentiation and apoptosis. It is estimated that RB is dysfunctional/inactivated in up to 40% of human leukemias. Positive as well as inhibitory signals are integrated into the phosphorylation of the RB protein to regulate the G1 to S-phase progression of the cell cycle. Despite the importance of RB in leukemia, the consequences of loss of RB on hematopoietic stem and progenitor cell (HSPC) function in vivo are still not clear and have been controversially discussed. Using Cre-enzyme expression driven by the hematopoietic specific Vav1-promotor, we generated mice that are constitutively deficient in RB (hemRb−/− animals) in HSPCs. HemRb−/− mice showed anemia with an increased number of reticulocytes in PB, consistent with a published role of RB in erythroid differentiation. In addition, the frequency of Mac-1 positive cells in BM was increased to 67% compared to 47% in control animals, whereas the frequency of B220 positive B-lymphoid cells was almost 10-fold reduced, without affecting the T-lymphoid compartment. HemRb−/− mice possessed a 3-fold enlarged spleen with a 5-fold increased number of colony-forming cells (CFCs) and severe extramedullary hematopoiesis, a phenotype also reported for animals transplanted with Rb−/− fetal liver cells. BM of hemRb−/− mice showed an almost 3-fold reduction of HSC frequency, measured by the cobblestone-area forming cell assay (CAFC) assay, but not a decrease in the number of HSCs determined by cell surface staining and flow cytometry. Upon transplantation into NOD/SCID animals or upon competitive transplantation into C57BL/6. CD45.1 animals, HSPCs from hemRb−/− mice contributed 4 to 6-fold less to hematopoiesis. HSPCs from hemRb−/− animals were neither impaired in their ability to home to the BM, nor did they show increased apoptosis. Finally, we detected a significant 4-fold decrease in stem cell function/numbers upon stress caused by 5-FU treatment in hemRB−/− mice compared to control animals. We conclude that upon transplantation/stress, HSPCs from hemRb−/− animals are impaired in their self-renewal function. HemRb−/− animals also showed a 2-fold increase in the frequency of CFCs in peripheral blood. As we detected no increased leukemia incidence in the hemRb−/− animals (now up to 1 year of age), loss of the tumor suppressor RB in hematopoietic cells might be regarded as necessary, but not sufficient for causing early onset leukemia. In summary, loss of RB results in context/localization dependent phenotypes in the hematopoietic hierarchy, influencing stem and progenitor cells in function, localization and differentiation ability.

scholarly journals The retinoblastoma tumor suppressor is a critical intrinsic regulator for hematopoietic stem and progenitor cells under stress

Blood ◽  
2008 ◽  
Vol 111 (4) ◽  
pp. 1894-1902 ◽  
Author(s):  
Deidre Daria ◽  
Marie-Dominique Filippi ◽  
Erik S. Knudsen ◽  
Roberta Faccio ◽  
Zhixiong Li ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Progenitor Cells ◽  
Peripheral Blood ◽  
Progenitor Cell ◽  
Cell Function ◽  
Fold Increase ◽  
Hematopoietic Stem ◽  
Retinoblastoma Tumor Suppressor ◽  
Retinoblastoma Tumor

The retinoblastoma tumor suppressor protein (RB) plays important roles in the control of the cell division cycle. It is estimated that RB is dysfunctional/inactivated in up to 40% of human leukemias. The consequences of loss of RB on hematopoietic stem and progenitor cell (HSPC) function in vivo are incompletely understood. Here, we report that mice genetically deficient in Rb in all hematopoietic cells (Vav-Cre Rb knockout [KO] animals) showed altered contribution of distinct hematopoietic cell lineages to peripheral blood, bone marrow, and spleen; significantly increased extramedullary hematopoiesis in the spleen; and a 2-fold increase in the frequency of hematopoietic progenitor cells in peripheral blood. Upon competitive transplantation, HSPCs from Vav-Cre Rb KO mice contributed with an at least 4- to 6-fold less efficiency to hematopoiesis compared with control cells. HSPCs deficient in Rb presented with impaired cell-cycle exit upon stress-induced proliferation, which correlated with impaired function. In summary, Rb is critical for hematopoietic stem and progenitor cell function, localization, and differentiation.

scholarly journals Retinoblastoma Tumor Suppressor: Analyses of Dynamic Behavior in Living Cells Reveal Multiple Modes of Regulation

2003 ◽  
Vol 23 (22) ◽  
pp. 8172-8188 ◽  
Author(s):  
Steven P. Angus ◽  
David A. Solomon ◽  
Lioba Kuschel ◽  
Robert F. Hennigan ◽  
Erik S. Knudsen
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Dynamic Behavior ◽  
Transcriptional Repression ◽  
Fluorescent Protein ◽  
Dynamic Equilibrium ◽  
Living Cells ◽  
Retinoblastoma Tumor Suppressor ◽  
Retinoblastoma Tumor

ABSTRACT The retinoblastoma tumor suppressor, RB, assembles multiprotein complexes to mediate cell cycle inhibition. Although many RB binding partners have been suggested to underlie these functions, the validity of these interactions on the behavior of RB complexes in living cells has not been investigated. Here, we studied the dynamic behavior of RB by using green fluorescent protein-RB fusion proteins. Although these proteins were universally nuclear, phosphorylation or oncoprotein binding mediated their active exclusion from the nucleolus. In vivo imaging approaches revealed that RB exists in dynamic equilibrium between a highly mobile and a slower diffusing species, and genetic lesions associated with tumorigenesis increased the fraction of RB in a highly mobile state. The RB complexes dictating cell cycle arrest were surprisingly dynamic and harbored a relatively short residence time on chromatin. In contrast, this rapid exchange was attenuated in cells that are hypersensitive to RB, suggesting that responsiveness may inversely correlate with mobility. The stability of RB dynamics within the cell was additionally modified by the presence and function of critical corepressors. Last, the RB-assembled complexes present in living cells were primarily associated with E2F binding sites in chromatin. In contrast to RB, E2F1 consistently maintained a stable association with E2F sites regardless of cell type. Together, these results elucidate the kinetic framework of RB tumor suppressor action in transcriptional repression and cell cycle regulation.

Relationship between the loss of the retinoblastoma tumor suppressor and radiosensitivity.

2011 ◽  
Vol 29 (7_suppl) ◽  
pp. 34-34 ◽  
Author(s):  
R. B. Den ◽  
S. Ciment ◽  
A. Sharma ◽  
H. Mellert ◽  
S. Mc-Mahon ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Cell Cycle ◽  
Dna Damage ◽  
Tumor Suppressor ◽  
Ionizing Radiation ◽  
Cell Survival ◽  
Retinoblastoma Tumor Suppressor ◽  
Clonogenic Cell ◽  
Retinoblastoma Tumor

34 Background: Prostate cancer is the most frequently diagnosed malignancy and the second leading cause of cancer death in U.S. men. The retinoblastoma tumor suppressor protein, RB, plays a critical role in cell cycle regulation. Loss of RB has been observed in 25–30% of prostate cancers and is correlated with increasing tumor stage and grade. The clinical consequences of RB loss are unknown. We have previously shown that RB loss results in a castrate resistant phenotype. We hypothesized that RB loss would downregulate the G1-S cell cycle arrest normally induced by irradiation, inhibit DNA repair, and subsequently sensitize cells to mitotic catastrophe. Methods: Experimental work was performed with multiple isogenic prostate cancer cell lines (hormone sensitive: LNCaP and LAP-C4 cells and hormone resistant C42 cells; stable knockdown of RB using shRNA). Gamma H2AX assays were used to quantitate DNA damage and PARP cleavage and Caspase 3 were used to quantitate apoptosis. FACS analysis with BrdU was used to assess the cell cycle. Cell survival was measured using the clonogenic cell survival assay. In vivo work was performed in nude mice with tumor xenografts. Results: We observed that loss of RB increased radioresponsiveness in both transient and clonogenic cell survival assays in all cell lines (p<0.05). Cell death was not mediated through increased apoptosis, however, there was increased cell cycling despite the presence of DNA damage in the RB knockdown cells. In vivo xenografts of the RB deficient tumors exhibited diminished tumor mass, lower PSA kinetics and decreased tumor growth after treatment with single fraction of ionizing radiation in comparison to RB intact tumors (p<0.05). Conclusions: Loss of RB results in a differential response to ionizing radiation. Isogenic cells with RB knockdown are more sensitive to DNA damage and result in reduced cell survival. RB status is integral to determining which therapeutic modality should be employed in the management of prostate cancer. No significant financial relationships to disclose.

scholarly journals The Corepressor mSin3a Interacts with the Proline-Rich Domain of p53 and Protects p53 from Proteasome-Mediated Degradation

2001 ◽  
Vol 21 (12) ◽  
pp. 3974-3985 ◽  
Author(s):  
Jack T. Zilfou ◽  
William H. Hoffman ◽  
Michael Sank ◽  
Donna L. George ◽  
Maureen Murphy
Keyword(s):  
Tumor Suppressor ◽  
Binding Domain ◽  
Protein Stabilization ◽  
Independent Manner ◽  
Retinoblastoma Tumor Suppressor Protein ◽  
Rich Domain ◽  
Retinoblastoma Tumor Suppressor ◽  
Retinoblastoma Tumor ◽  
Sin3 Complex

ABSTRACT While the transactivation function of the tumor suppressor p53 is well understood, less is known about the transrepression functions of this protein. We have previously shown that p53 interacts with the corepressor protein mSin3a (hereafter designated Sin3) in vivo and that this interaction is critical for the ability of p53 to repress gene expression. In the present study, we demonstrate that expression of Sin3 results in posttranslational stabilization of both exogenous and endogenous p53, due to an inhibition of proteasome-mediated degradation of this protein. Stabilization of p53 by Sin3 requires the Sin3-binding domain, determined here to map to the proline-rich region of p53, from amino acids 61 to 75. The correlation between Sin3 binding and stabilization supports the hypothesis that this domain of p53 may normally be subject to a destabilizing influence. The finding that a synthetic mutant of p53 lacking the Sin3-binding domain has an increased half-life in cells, compared to wild-type p53, supports this premise. Interestingly, unlike retinoblastoma tumor suppressor protein, MDMX, and p14ARF, Sin3 stabilizes p53 in an MDM2-independent manner. The ability of Sin3 to stabilize p53 is consistent with the model whereby these two proteins must exist on a promoter for extended periods, in order for repression to be an effective mechanism of gene regulation. This model is consistent with our data indicating that, unlike the p300-p53 complex, the p53-Sin3 complex is immunologically detectable for prolonged periods following exposure of cells to agents of DNA damage.

High GATA-2 expression inhibits human hematopoietic stem and progenitor cell function by effects on cell cycle

Blood ◽  
2009 ◽  
Vol 113 (12) ◽  
pp. 2661-2672 ◽  
Author(s):  
Alex J. Tipping ◽  
Cristina Pina ◽  
Anders Castor ◽  
Dengli Hong ◽  
Neil P. Rodrigues ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cord Blood ◽  
Cell Function ◽  
Ki 67 ◽  
Human Cord Blood ◽  
Hematopoietic Stem ◽  
Cord Blood Cells ◽  
Low Efficiency

Abstract Evidence suggests the transcription factor GATA-2 is a critical regulator of murine hematopoietic stem cells. Here, we explore the relation between GATA-2 and cell proliferation and show that inducing GATA-2 increases quiescence (G0 residency) of murine and human hematopoietic cells. In human cord blood, quiescent fractions (CD34+CD38−HoechstloPyronin Ylo) express more GATA-2 than cycling counterparts. Enforcing GATA-2 expression increased quiescence of cord blood cells, reducing proliferation and performance in long-term culture-initiating cell and colony-forming cell (CFC) assays. Gene expression analysis places GATA-2 upstream of the quiescence regulator MEF, but enforcing MEF expression does not prevent GATA-2–conferred quiescence, suggesting additional regulators are involved. Although known quiescence regulators p21CIP1 and p27KIP1 do not appear to be responsible, enforcing GATA-2 reduced expression of regulators of cell cycle such as CCND3, CDK4, and CDK6. Enforcing GATA-2 inhibited human hematopoiesis in vivo: cells with highest exogenous expression (GATA-2hi) failed to contribute to hematopoiesis in nonobese diabetic–severe combined immunodeficient (NOD-SCID) mice, whereas GATA-2lo cells contributed with delayed kinetics and low efficiency, with reduced expression of Ki-67. Thus, GATA-2 activity inhibits cell cycle in vitro and in vivo, highlighting GATA-2 as a molecular entry point into the transcriptional program regulating quiescence in human hematopoietic stem and progenitor cells.

Hoxb4-deficient mice undergo normal hematopoietic development but exhibit a mild proliferation defect in hematopoietic stem cells

Blood ◽  
2004 ◽  
Vol 103 (11) ◽  
pp. 4126-4133 ◽  
Author(s):  
Ann C. M. Brun ◽  
Jon Mar Björnsson ◽  
Mattias Magnusson ◽  
Nina Larsson ◽  
Per Leveén ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Hox Genes ◽  
Fetal Liver ◽  
Severe Combined Immunodeficiency ◽  
Hematopoietic Stem ◽  
Cell Counts ◽  
Mild Reduction

Abstract Enforced expression of Hoxb4 dramatically increases the regeneration of murine hematopoietic stem cells (HSCs) after transplantation and enhances the repopulation ability of human severe combined immunodeficiency (SCID) repopulating cells. Therefore, we asked what physiologic role Hoxb4 has in hematopoiesis. A novel mouse model lacking the entire Hoxb4 gene exhibits significantly reduced cellularity in spleen and bone marrow (BM) and a subtle reduction in red blood cell counts and hemoglobin values. A mild reduction was observed in the numbers of primitive progenitors and stem cells in adult BM and fetal liver, whereas lineage distribution was normal. Although the cell cycle kinetics of primitive progenitors was normal during endogenous hematopoiesis, defects in proliferative responses of BM Lin- Sca1+ c-kit+ stem and progenitor cells were observed in culture and in vivo after the transplantation of BM and fetal liver HSCs. Quantitative analysis of mRNA from fetal liver revealed that a deficiency of Hoxb4 alone changed the expression levels of several other Hox genes and of genes involved in cell cycle regulation. In summary, the deficiency of Hoxb4 leads to hypocellularity in hematopoietic organs and impaired proliferative capacity. However, Hoxb4 is not required for the generation of HSCs or the maintenance of steady state hematopoiesis.

Essential Role for Rbm15 (Ott1) in the Maintenance of Hematopoietic Stem Cell Function and Cell Cycle Control.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1223-1223
Author(s):  
Chao Niu ◽  
Jiwang Zhang ◽  
Stephan W. Morris
Keyword(s):  
Cell Cycle ◽  
Cell Function ◽  
Critical Role ◽  
White Blood Cells ◽  
Conditional Knockout ◽  
Brdu Incorporation ◽  
Fusion Partner ◽  
Ki 67 ◽  
Hematopoietic Stem ◽  
Marrow Cells

Abstract RBM15 is the 5′ fusion partner in RBM15-MKL1 (aka OTT1-MAL), a putative oncoprotein in non-Down syndrome infants and children with acute megakaryoblastic leukemia (FAB-M7) containing t(1;22). RBM15 belongs to the “spen” family, which is characterized by the presence of three RNA recognition motifs and a spen paralog and ortholog C-terminal (SPOC) domain. RBM15-homologous Drosophila proteins are involved in regulation of a variety of signaling cascades including MAPK, Wnt, Notch, cyclin E and Hox pathways, but the normal functions of mammalian RBM15 remain largely uncharacterized. We determined that Rbm15 is highly expressed in hematopoietic stem cells (HSCs) as well as T-lineage cells. To study Rbm15 specifically in the regulation of HSC function, we generated Rbm15 conditional knockout mice using the Cre-LoxP system to overcome embryonic death observed with a conventional knockout. Using an inducible Mx1-Cre transgenic line, we conditionally deleted Rbm15 (deletion efficiency ∼96–100%) in HSCs. Both the percentage and absolute number of long-term HSCs (Lin-Sca1+ckit+/Flk2-) were increased in Rbm15-deleted (Rbm15lx/lx;Mx1-Cre+) mice (0.23 ± 0.02% of total nucleated marrow cells [TNMC], 2.3-fold higher) compared to matched littermate controls (Rbm15lx/lx;Mx1-Cre-) (0.10 ± 0.01% TNMC) (P<0.0001, n=18 mice per group). By contrast, total white blood cells (WBCs) were significantly decreased in the peripheral blood (PB) of Rbm15-deleted animals compared to controls (Rbm15-deleted: 5.33 ± 0.40 × 103/uL, Rbm15-intact: 10.26 ± 0.49 × 103/uL; P <0.0001, n=31 per group). Functional analysis of Rbm15-deleted HSCs by competitive repopulation showed these cells to be markedly impaired in their reconstitution of hematopoiesis in lethally-irradiated recipient mice, with only 9.73 ± 2.32% donor-derived cells in the PB of transplanted animals compared to a 47.52 ± 7.26% contribution by donor cells from littermate controls (P=0.00015; n=10 mice per group; 1:1 ratio of donor:wild-type competitor marrow). The serial transplantation ability of Rbm15-deleted HSCs was also severely decreased, with a decline in their engraftment and contribution to the blood of recipient mice noted beginning with the 3rd round of transplantation, culminating in essentially complete failure to engraft in the 4th round (wild-type donor-derived PB cells in 4th round ∼60.95% vs. ∼2.71% Rbm15-deleted donor-derived PB cells; P=0.00003). These defects in HSC function may be due in part to altered HSC cell cycle status in the absence of Rbm15. For example, in representative experiments using Ki-67/Hoechst 33342 and BrdU/7AAD staining, 24.1% and 19.3% of Rbm15-deleted HSCs were found to be in G1 and G2/M phases, respectively - a marked increase compared to Rbm15-intact controls (8.3% and 4.3%, respectively); furthermore, Rbm15-deleted HSCs exhibited significantly less BrdU incorporation (6.8%) compared to control HSCs (27.1%) in in vivo labeling studies. Consistent with these altered cell cycle parameters, hematopoiesis in Rbm15-deleted mice recovered significantly more slowly than controls following 5-FU exposure, with only half the number of total nucleated marrow cells at day 9 and half the number of mature PB WBCs at day 12 following 5-FU as compared to Rbm15-intact littermates (p=0.003, n=3 per group). Collectively, these data demonstrate a critical role for Rbm15 in maintaining HSC integrity and suggest a yet-to-be fully elucidated function for Rbm15 in modulating HSC cell cycle kinetics.

scholarly journals RBP1 Recruits the mSIN3-Histone Deacetylase Complex to the Pocket of Retinoblastoma Tumor Suppressor Family Proteins Found in Limited Discrete Regions of the Nucleus at Growth Arrest

2001 ◽  
Vol 21 (8) ◽  
pp. 2918-2932 ◽  
Author(s):  
Albert Lai ◽  
Brian K. Kennedy ◽  
David A. Barbie ◽  
Nicholas R. Bertos ◽  
Xiang Jiao Yang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Histone Deacetylase ◽  
Family Members ◽  
Growth Stimulation ◽  
Stable Complex ◽  
Induce Cell Cycle Arrest ◽  
Retinoblastoma Tumor Suppressor ◽  
Retinoblastoma Tumor ◽  
Class I Hdacs

ABSTRACT Retinoblastoma (RB) tumor suppressor family pocket proteins induce cell cycle arrest by repressing transcription of E2F-regulated genes through both histone deacetylase (HDAC)-dependent and -independent mechanisms. In this study we have identified a stable complex that accounts for the recruitment of both repression activities to the pocket. One component of this complex is RBP1, a known pocket-binding protein that exhibits both HDAC-dependent and -independent repression functions. RB family proteins were shown to associate via the pocket with previously identified mSIN3-SAP30-HDAC complexes containing exclusively class I HDACs. Such enzymes do not interact directly with RB family proteins but rather utilize RBP1 to target the pocket. This mechanism was shown to account for the majority of RB-associated HDAC activity. We also show that in quiescent normal human cells this entire RBP1-mSIN3-SAP30-HDAC complex colocalizes with both RB family members and E2F4 in a limited number of discrete regions of the nucleus that in other studies have been shown to represent the initial origins of DNA replication following growth stimulation. These results suggest that RB family members, at least in part, drive exit from the cell cycle by recruitment of this HDAC complex via RBP1 to repress transcription from E2F-dependent promoters and possibly to alter chromatin structure at DNA origins.

scholarly journals Extracellular vesicles of stromal origin target and support hematopoietic stem and progenitor cells

2017 ◽  
Vol 216 (7) ◽  
pp. 2217-2230 ◽  
Author(s):  
Gregoire Stik ◽  
Simon Crequit ◽  
Laurence Petit ◽  
Jennifer Durant ◽  
Pierre Charbord ◽  
...  
Keyword(s):  
Gene Expression ◽  
Progenitor Cells ◽  
Extracellular Vesicles ◽  
Ex Vivo ◽  
Fetal Liver ◽  
Critical Role ◽  
Molecular Signature ◽  
Hematopoietic Stem ◽  
Stem And Progenitor Cells

Extracellular vesicles (EVs) have been recently reported as crucial mediators in cell-to-cell communication in development and disease. In this study, we investigate whether mesenchymal stromal cells that constitute a supportive microenvironment for hematopoietic stem and progenitor cells (HSPCs) released EVs that could affect the gene expression and function of HSPCs. By taking advantage of two fetal liver–derived stromal lines with widely differing abilities to maintain HSPCs ex vivo, we demonstrate that stromal EVs play a critical role in the regulation of HSPCs. Both supportive and nonsupportive stromal lines secreted EVs, but only those delivered by the supportive line were taken up by HSPCs ex vivo and in vivo. These EVs harbored a specific molecular signature, modulated the gene expression in HSPCs after uptake, and maintained the survival and clonogenic potential of HSPCs, presumably by preventing apoptosis. In conclusion, our study reveals that EVs are an important component of the HSPC niche, which may have major applications in regenerative medicine.

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