Gfi1 as a Regulator of Hematopoietic Differentiation.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. sci-16-sci-16
Author(s):  
H. Leighton Grimes ◽  
Chinavenmeni S. Velu ◽  
Shane Horman ◽  
Aditya Chaubey ◽  
Tristan Bourdeau ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
Target Genes ◽  
Cell Transformation ◽  
Bone Marrow Failure ◽  
Leukemia Virus ◽  
Dominant Negative ◽  
Insertion Mutagenesis ◽  
Loss Of Function ◽  
Mutant Proteins

Abstract Growth Factor Independent-1 (Gfi1) is a transcriptional repressor originally identified as a target of Moloney leukemia virus insertion mutagenesis. Gfi1 potently collaborates with Myc and Pim oncogenes to mediate T cell transformation. Retroviral insertions which activate Gfi1 are among the most frequent events in MoMLV-induced T cell, but not myeloid, leukemias. Orthologous proteins in Drosophila (Senseless) and C.elegans (Pag-3) are key regulators of developmental decisions. Gfi1−/− mice display lymphopenia, neutropenia, and abnormally proliferative HSC and progenitors which eventually lead to bone marrow failure. Humans with bone marrow failure syndromes, such as Severe Congenital Neutropenia or Non-Immune Chronic Idiopathic Neutropenia of Adults, display mutations in GFI1, which produce dominant negative acting GFI1 proteins. The SCN-associated GFI1N382S mutant proteins derepress a subset of GFI1 target genes, including CSF1 and CSF1R, to block granulopoeisis. Normally, Gfi1 antagonizes monopoiesis mediated by Pu.1, Egr1, Egr2, and Nab2. Thus, Gfi1 loss of function may impair granulopoiesis by failing to successfully repress monopoeitic differentiation. GFI1 dysfunction may also underlie Specific Granule Deficiency. GFI1 is able to synergize with C/EBP transcription factors to activate genes, such as neutrophil collagenase. Gfi1 may, therefore, enhance granulopoietic differentiation through C/EBP factors. Though great progress has been made in understanding Gfi1 biological and biochemical functions, we are only beginning to understand the role of Gfi1 in integrating hematopoietic transcriptional programming. We find that Gfi1 signaling controls both the differentiation and transformation of myeloid progenitors through an evolutionarily conserved transcriptional and post-transcriptional network.

scholarly journals Loss of the homologous recombination generad51leads to Fanconi anemia-like symptoms in zebrafish

2017 ◽  
Vol 114 (22) ◽  
pp. E4452-E4461 ◽  
Author(s):  
Jan Gregor Botthof ◽  
Ewa Bielczyk-Maczyńska ◽  
Lauren Ferreira ◽  
Ana Cvejic
Keyword(s):  
Bone Marrow ◽  
Homologous Recombination ◽  
Fanconi Anemia ◽  
Bone Marrow Failure ◽  
Marrow Cell ◽  
Tumor Development ◽  
Dominant Negative ◽  
Loss Of Function ◽  
Hematopoietic Stem ◽  
Inflammatory Stress

RAD51 is an indispensable homologous recombination protein, necessary for strand invasion and crossing over. It has recently been designated as a Fanconi anemia (FA) gene, following the discovery of two patients carrying dominant-negative mutations. FA is a hereditary DNA-repair disorder characterized by various congenital abnormalities, progressive bone marrow failure, and cancer predisposition. In this report, we describe a viable vertebrate model ofRAD51loss. Zebrafishrad51loss-of-function mutants developed key features of FA, including hypocellular kidney marrow, sensitivity to cross-linking agents, and decreased size. We show that some of these symptoms stem from both decreased proliferation and increased apoptosis of embryonic hematopoietic stem and progenitor cells. Comutation ofp53was able to rescue the hematopoietic defects seen in the single mutants, but led to tumor development. We further demonstrate that prolonged inflammatory stress can exacerbate the hematological impairment, leading to an additional decrease in kidney marrow cell numbers. These findings strengthen the assignment ofRAD51as a Fanconi gene and provide more evidence for the notion that aberrant p53 signaling during embryogenesis leads to the hematological defects seen later in life in FA. Further research on this zebrafish FA model will lead to a deeper understanding of the molecular basis of bone marrow failure in FA and the cellular role of RAD51.

Bone marrow failure due to T-cell large granular lymphocytic leukemia in a patient with essential thrombocythemia

2011 ◽  
Vol 35 (2) ◽  
pp. 278-282 ◽  
Author(s):  
Senthamil R. Selvan ◽  
Patrick F. Sheehy ◽  
F. Scott Heinemann ◽  
Selvagambeer Anbuganapathi
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
Essential Thrombocythemia ◽  
Bone Marrow Failure ◽  
Lymphocytic Leukemia ◽  
Large Granular Lymphocytic Leukemia

scholarly journals miR-22-3p Negatively Affects Tumor Progression in T-Cell Acute Lymphoblastic Leukemia

Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1726
Author(s):  
Valentina Saccomani ◽  
Angela Grassi ◽  
Erich Piovan ◽  
Deborah Bongiovanni ◽  
Ludovica Di Martino ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Target Genes ◽  
Cell Transformation ◽  
Lymphoblastic Leukemia ◽  
T Cell Development ◽  
Cell Acute Lymphoblastic Leukemia ◽  
Notch1 Signaling Pathway

T-cell acute lymphoblastic leukemia (T-ALL) is a rare, aggressive disease arising from T-cell precursors. NOTCH1 plays an important role both in T-cell development and leukemia progression, and more than 60% of human T-ALLs harbor mutations in components of the NOTCH1 signaling pathway, leading to deregulated cell growth and contributing to cell transformation. Besides multiple NOTCH1 target genes, microRNAs have also been shown to regulate T-ALL initiation and progression. Using an established mouse model of T-ALL induced by NOTCH1 activation, we identified several microRNAs downstream of NOTCH1 activation. In particular, we found that NOTCH1 inhibition can induce miR-22-3p in NOTCH1-dependent tumors and that this regulation is also conserved in human samples. Importantly, miR-22-3p overexpression in T-ALL cells can inhibit colony formation in vitro and leukemia progression in vivo. In addition, miR-22-3p was found to be downregulated in T-ALL specimens, both T-ALL cell lines and primary samples, relative to immature T-cells. Our results suggest that miR-22-3p is a functionally relevant microRNA in T-ALL whose modulation can be exploited for therapeutic purposes to inhibit T-ALL progression.

scholarly journals p30 protein: a critical regulator of HTLV-1 viral latency and host immunity

Retrovirology ◽  
2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Ramona Moles ◽  
Sarkis Sarkis ◽  
Veronica Galli ◽  
Maria Omsland ◽  
Damian F. J. Purcell ◽  
...  
Keyword(s):  
T Cell ◽  
Viral Infection ◽  
Cell Transformation ◽  
Leukemia Virus ◽  
Single Point ◽  
Protein A ◽  
Indigenous Communities ◽  
Fine Tuning ◽  
Single Point Mutation ◽  
Subtype C

AbstractThe extraordinarily high prevalence of HTLV-1 subtype C (HTLV-1C) in some isolated indigenous communities in Oceania and the severity of the health conditions associated with the virus impress the great need for basic and translational research to prevent and treat HTLV-1 infection. The genome of the virus’s most common subtype, HTLV-1A, encodes structural, enzymatic, and regulatory proteins that contribute to viral persistence and pathogenesis. Among these is the p30 protein encoded by the doubly spliced Tax-orf II mRNA, a nuclear/nucleolar protein with both transcriptional and post-transcriptional activity. The p30 protein inhibits the productive replication cycle via nuclear retention of the mRNA that encodes for both the viral transcriptional trans-activator Tax, and the Rex proteins that regulate the transport of incompletely spliced viral mRNA to the cytoplasm. In myeloid cells, p30 inhibits the PU-1 transcription factor that regulates interferon expression and is a critical mediator of innate and adaptive immunity. Furthermore, p30 alters gene expression, cell cycle progression, and DNA damage responses in T-cells, raising the hypothesis that p30 may directly contribute to T cell transformation. By fine-tuning viral expression while also inhibiting host innate responses, p30 is likely essential for viral infection and persistence. This concept is supported by the finding that macaques, a natural host for the closely genetically related simian T-cell leukemia virus 1 (STLV-1), exposed to an HTLV-1 knockout for p30 expression by a single point mutation do not became infected unless reversion and selection of the wild type HTLV-1 genotype occurs. All together, these data suggest that inhibition of p30 may help to curb and eventually eradicate viral infection by exposing infected cells to an effective host immune response.

scholarly journals Functions of E2A-HEB Heterodimers in T-Cell Development Revealed by a Dominant Negative Mutation of HEB

2000 ◽  
Vol 20 (18) ◽  
pp. 6677-6685 ◽  
Author(s):  
Robert J. Barndt ◽  
Meifang Dai ◽  
Yuan Zhuang
Keyword(s):  
T Cell ◽  
Target Genes ◽  
T Cell Development ◽  
Cell Lineage ◽  
Cell Receptor ◽  
Cell Development ◽  
Dominant Negative ◽  
Helix Loop Helix ◽  
Dominant Negative Mutation ◽  
Bhlh Proteins

ABSTRACT Lymphocyte development and differentiation are regulated by the basic helix-loop-helix (bHLH) transcription factors encoded by theE2A and HEB genes. These bHLH proteins bind to E-box enhancers in the form of homodimers or heterodimers and, consequently, activate transcription of the target genes. E2A homodimers are the predominant bHLH proteins present in B-lineage cells and are shown genetically to play critical roles in B-cell development. E2A-HEB heterodimers, the major bHLH dimers found in thymocyte extracts, are thought to play a similar role in T-cell development. However, disruption of either the E2A or HEBgene led to only partial blocks in T-cell development. The exact role of E2A-HEB heterodimers and possibly the E2A and HEB homodimers in T-cell development cannot be distinguished in simple disruption analysis due to a functional compensation from the residual bHLH homodimers. To further define the function of E2A-HEB heterodimers, we generated and analyzed a dominant negative allele of HEB, which produces a physiological amount of HEB proteins capable of forming nonfunctional heterodimers with E2A proteins. Mice carrying this mutation show a stronger and earlier block in T-cell development than HEB complete knockout mice. The developmental block is specific to the α/β T-cell lineage at a stage before the completion of V(D)J recombination at the TCRβ gene locus. This defect is intrinsic to the T-cell lineage and cannot be rescued by expression of a functional T-cell receptor transgene. These results indicate that E2A-HEB heterodimers play obligatory roles both before and after TCRβ gene rearrangement during the α/β lineage T-cell development.

scholarly journals STAT3 mutations indicate the presence of subclinical T-cell clones in a subset of aplastic anemia and myelodysplastic syndrome patients

Blood ◽  
2013 ◽  
Vol 122 (14) ◽  
pp. 2453-2459 ◽  
Author(s):  
Andres Jerez ◽  
Michael J. Clemente ◽  
Hideki Makishima ◽  
Hanna Rajala ◽  
Ines Gómez-Seguí ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Myelodysplastic Syndrome ◽  
Aplastic Anemia ◽  
Somatic Mutation ◽  
Bone Marrow Failure ◽  
Cell Clones ◽  
Key Points ◽  
Stat3 Mutations

Key PointsSTAT3+ T cells are found not only in detected concomitant LGL-BMFs, but in cases in which an LGL expansion was not suspected. Transformation via acquisition of a somatic mutation in T cells may be a mechanism of immune, mainly hypoplastic, bone marrow failure.

scholarly journals Identification of a new common provirus integration site in gross passage A murine leukemia virus-induced mouse thymoma DNA.

1987 ◽  
Vol 7 (1) ◽  
pp. 512-522 ◽  
Author(s):  
R Villemur ◽  
Y Monczak ◽  
E Rassart ◽  
C Kozak ◽  
P Jolicoeur
Keyword(s):  
T Cell ◽  
Murine Leukemia Virus ◽  
Cell Transformation ◽  
Integration Site ◽  
Leukemia Virus ◽  
Tumor Development ◽  
Mouse Strains ◽  
Mouse Tumor ◽  
Provirus Integration ◽  
Murine Leukemia

The Gross passage A murine leukemia virus (MuLV) induced T-cell leukemia of clonal (or oligoclonal) origin in inoculated mice. To study the role of the integrated proviruses in these tumor cells, we cloned several newly integrated proviruses (with their flanking cellular sequences) from a single tumor in procaryotic vectors. With each of the five clones obtained, a probe was prepared from the cellular sequences flanking the provirus. With one such probe (SS8), we screened several Gross passage A MuLV-induced SIM.S mouse tumor DNAs and found that, in 11 of 40 tumors, a provirus was integrated into a common region designated Gin-1. A 26-kilobase-pair sequence of Gin-1 was cloned from two lambda libraries, and a restriction map was derived. All proviruses were integrated as a cluster in the same orientation within a 5-kilobase-pair region of Gin-1, and most of them had a recombinant structure of the mink cell focus-forming virus type. The frequency of Gin-1 occupancy by provirus was much lower in thymoma induced by other strains of MuLV in other mouse strains. Using somatic-cell hybrid DNAs, we mapped Gin-1 on mouse chromosome 19. Gin-1 was not homologous to 16 known oncogenes and was distinct from the other common regions for provirus integration previously described. Therefore, Gin-1 appears to represent a new common provirus integration region. The integration of a provirus within Gin-1 might be an important event leading to T-cell transformation, and the Gin-1 region might harbor sequences which are involved in tumor development.

SAP (SH2D1A), the Immunomodulator Deficient in X-Linked Lymphoproliferative Syndrome (XLP), Is Profoundly Decreased in Aplastic Anemia: An Immunologic Link between Constitutional and Acquired Bone Marrow Failure.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1141-1141
Author(s):  
Elena E. Solomou ◽  
Valeria Visconte ◽  
Federica Gibellini ◽  
Neal S. Young
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Aplastic Anemia ◽  
T Cell Activation ◽  
Cell Activation ◽  
Bone Marrow Failure ◽  
Protein Levels ◽  
Ifn Γ ◽  
Th1 Polarization

Abstract Ligation of the signaling lymphocyte activation molecule (SLAM), a member of the immunoglobulin superfamily expressed in T and B cells, results in T cell activation and Th1 cytokine production. SAP is a small cytoplasmic protein expressed in T- and NK cells that controls the activation signals mediated by SLAM. On T cell activation, SAP binds to Fyn kinase; Fyn is activated and phosphorylates tyrosine residues on SLAM; phosphorylation results in the formation of a complex that selectively down-regulates co-stimulatory signals in activated T cells, resulting in inhibition of IFN-γ production. Thus SAP acts as a natural suppressor of SLAM-mediated T cell activation, and, in the absence of SAP, T cells are constitutively activated and overproduce IFN-γ. Mutations in the SAP gene lead to abnormal T cell activation and enhanced Th1 cytokine production in mouse models and in humans: about half of patients with X-linked lympoproliferative disease (XLP) have functionally disabling SAP mutations. Acquired aplastic anemia (AA) is a bone marrow failure syndrome in which hematopoietic cell destruction is effected by cytotoxic T cells and type 1 cytokines. We have recently shown that T cells from patients with AA have increased protein levels of T-bet, resulting in IFN-γ overproduction (Solomou EE et al, Blood2006; 107:3983). IFN-γ inhibits hematopoietic stem cell proliferation and induces Fas-mediated apoptosis; stem cell depletion results in marrow hypoplasia and peripheral blood pancytopenia. We examined SAP expression as an explanation for aberrant T cell activation and extreme Th1 polarization. SAP protein expression on immunoblot was very low to absent in unstimulated T cells from 16 of 20 AA patients examined, as compared to normal levels of expression in equivalent numbers of healthy donors (p<0.001). No significant differences were detected in Fyn and SLAM protein levels between AA and controls. SAP mRNA levels were also significantly decreased in T cells from those AA patients with low SAP protein levels, as determined by RT-PCR. Peripheral blood DNA samples from 18 patients with AA were analyzed for SAP mutations: three novel intronic mutations, not present in controls, were identified among 7 unrelated patients: one mutation was in the promoter region of SAP (position 106, C to T; 3 patients), and two mutations in the intron-exon junction between exons 1 and 2 (position 38975, C toT; 3 patients) and 3 and 4 (position 62771, C to A; 1 patient). IFN-γ, as measured by ELISA, in three patients with undetectable SAP protein levels was significantly increased compared to healthy controls (n=5, p<0.001). Increased IFN-γ levels and Th1 polarization in AA can in part be explained by functional SAP deficiency. SAP-deficient T cells in AA would be unable to block co-stimulatory signals, leading to an activated T cell phenotype and ultimately hematopoietic cell destruction and bone marrow failure. The SAP-deficient phenotype in T cells from patients with aplastic anemia may be secondary to subtle genetic alteration in the gene’s regulation (abnormal promoter binding sites or epigenetic modulation due to mutations in introns) or as yet unidentified aberrant upstream pathways (Ets-1 and Ets-2, the transcription factors that regulate SAP expression).

A Microrna Feed-Forward Loop Amplifies GFI1N382S Transcriptional Reprogramming In Severe Congenital Neutropenia

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2239-2239
Author(s):  
Chinavenmeni Subramani Velu ◽  
Avedis Kazanjian ◽  
Clemencia Colmenares ◽  
H. Leighton Grimes
Keyword(s):  
Bone Marrow ◽  
Target Genes ◽  
Bone Marrow Cells ◽  
Transcriptional Repressor ◽  
Dominant Negative ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia ◽  
Feed Forward ◽  
Marrow Cells ◽  
Myeloid Progenitors

Abstract Abstract 2239 The Growth factor independent -1 (Gfi1) transcriptional repressor regulates both hematopoietic stem cell self renewal and myeloid differentiation. Humans with severe congenital neutropenia (SCN) display mutations in GFI1 that generate dominant negative acting proteins. Moreover, GFI1-mutant SCN patients and Gfi1-/- mice display a unique accumulation of myeloid progenitors. Recently we showed that Gfi1 regulation of HoxA9, Pbx1 and Meis1 underlies these phenomena, in that the Gfi1-Hox transcriptional circuit controls the accumulation of myeloid progenitors in vivo. We have also shown that Gfi1 regulates miR-21 during myelopoiesis, and that miR-21 is deregulated by Gfi1N382S expression. Our new data link these concepts by demonstrating that forced expression of miR-21 in bone marrow cells results in the accumulation of myeloid progenitors in transplant recipients. Moreover, miR-21 directly targets the Ski oncoprotein, and Ski-/- bone marrow cells show an accumulation of myeloid progenitors. Thus, Gfi1-/-, miR-21 overexpressing-, and Ski-/- myeloid progenitors accumulate in the marrow. Strikingly, Ski is dramatically reduced in miR-21 overexpressing Lin- bone marrow cells. Nearly undetectable Ski expression in Gfi1-/- bone marrow cells can be completely rescued by antagonizing miR-21 activity. Since Ski is a corepressor and Gfi1 is a transcriptional repressor, we next tested whether the two proteins physically interact. Indeed, endogenous Ski and Gfi1 can be coimmunoprecipitated. Synthetic Ski and Gfi1 proteins reveal that the interaction is mediated through Ski carboxy-terminal and Gfi1 zinc-finger domains. Chromatin immunoprecipitation reveals Ski and Gfi1 co-occupy several Gfi1 target genes (including HoxA9), which are derepressed upon Gfi1 or Ski knockdown. However, while Gfi1 binds and regulates the miR-21 gene, Ski is not bound to the miR-21 gene, and Ski knockdown has no effect upon miR-21 levels. Thus, the data point to a novel feed-forward transcriptional circuit. Gfi1N382S deregulation of miR-21 amplifies the dominant-negative effect of Gfi1N382S through miR-21 targeting of Ski, leading to further derepression of Gfi1-Ski target genes. Disclosures: No relevant conflicts of interest to declare.

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