scholarly journals The transcriptional program controlled by the stem cell leukemia gene Scl/Tal1 during early embryonic hematopoietic development

Blood ◽  
2009 ◽  
Vol 113 (22) ◽  
pp. 5456-5465 ◽  
Author(s):  
Nicola K. Wilson ◽  
Diego Miranda-Saavedra ◽  
Sarah Kinston ◽  
Nicolas Bonadies ◽  
Samuel D. Foster ◽  
...  

The basic helix-loop-helix transcription factor Scl/Tal1 controls the development and subsequent differentiation of hematopoietic stem cells (HSCs). However, because few Scl target genes have been validated to date, the underlying mechanisms have remained largely unknown. In this study, we have used ChIP-Seq technology (coupling chromatin immunoprecipitation with deep sequencing) to generate a genome-wide catalog of Scl-binding events in a stem/progenitor cell line, followed by validation using primary fetal liver cells and comprehensive transgenic mouse assays. Transgenic analysis provided in vivo validation of multiple new direct Scl target genes and allowed us to reconstruct an in vivo validated network consisting of 17 factors and their respective regulatory elements. By coupling ChIP-Seq in model cell lines with in vivo transgenic validation and sophisticated bioinformatic analysis, we have identified a widely applicable strategy for the reconstruction of stem cell regulatory networks in which biologic material is otherwise limiting. Moreover, in addition to revealing multiple previously unrecognized links to known HSC regulators, as well as novel links to genes not previously implicated in HSC function, comprehensive transgenic analysis of regulatory elements provided substantial new insights into the transcriptional control of several important hematopoietic regulators, including Cbfa2t3h/Eto2, Cebpe, Nfe2, Zfpm1/Fog1, Erg, Mafk, Gfi1b, and Myb.

2010 ◽  
Vol 30 (15) ◽  
pp. 3853-3863 ◽  
Author(s):  
Nicola K. Wilson ◽  
Richard T. Timms ◽  
Sarah J. Kinston ◽  
Yi-Han Cheng ◽  
S. Helen Oram ◽  
...  

ABSTRACT The growth factor independence 1 (Gfi1) gene was originally discovered in the hematopoietic system, where it functions as a key regulator of stem cell homeostasis, as well as neutrophil and T-cell development. Outside the blood system, Gfi1 is essential for inner-ear hair and intestinal secretory cell differentiation. To understand the regulatory hierarchies within which Gfi1 operates to control these diverse biological functions, we used a combination of comparative genomics, locus-wide chromatin immunoprecipitation assays, functional validation in cell lines, and extensive transgenic mouse assays to identify and characterize the complete ensemble of Gfi1 regulatory elements. This concerted effort identified five distinct regulatory elements spread over 100kb each driving expression in transgenic mice to a subdomain of endogenous Gfi1. Detailed characterization of an enhancer 35 kb upstream of Gfi1 demonstrated activity in the dorsal aorta region and fetal liver in transgenic mice, which was bound by key stem cell transcription factors Scl/Tal1, PU.1/Sfpi1, Runx1, Erg, Meis1, and Gata2. Taken together, our results reveal the regulatory regions responsible for Gfi1 expression and importantly establish that Gfi1 expression at the sites of hematopoietic stem cell (HSC) emergence is controlled by key HSC regulators, thus integrating Gfi1 into the wider HSC regulatory networks.


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1387-1387
Author(s):  
Hong Qian ◽  
Sten Eirik W. Jacobsen ◽  
Marja Ekblom

Abstract Homing of transplanted hematopoietic stem cells (HSC) in the bone marrow (BM) is a prerequisite for establishment of hematopoiesis following transplantation. However, although multiple adhesive interactions of HSCs with BM microenviroment are thought to critically influence their homing and subsequently their engraftment, the molecular pathways that control the homing of transplanted HSCs, in particular, of fetal HSCs are still not well understood. In experimental mouse stem cell transplantation models, several integrins have been shown to be involved in the homing and engraftment of both adult and fetal stem and progenitor cells in BM. We have previously found that integrin a6 mediates human hematopoietic stem and progenitor cell adhesion to and migration on its specific ligands, laminin-8 and laminin-10/11 in vitro (Gu et al, Blood, 2003; 101:877). Furthermore, integrin a6 is required for adult mouse HSC homing to BM in vivo (Qian et al., Abstract American Society of Hematology, Blood 2004 ). We have now found that the integrin a6 chain like in adult HSC is ubiquitously (>99%) expressed also in fetal liver hematopoietic stem and progenitor cells (lin−Sca-1+c-Kit+, LSK ). In vitro, fetal liver LSK cells adhere to laminin-10/11 and laminin-8 in an integrin a6b1 receptor-dependent manner, as shown by function blocking monoclonal antibodies. We have now used a function blocking monoclonal antibody (GoH3) against integrin a6 to analyse the role of the integrin a6 receptor for the in vivo homing of fetal liver hematopoietic stem and progenitor cells to BM. The integrin a6 antibody inhibited homing of fetal liver progenitors (CFU-C) into BM of lethally irradiated recipients. The number of homed CFU-C in BM was reduced by about 40% as compared to the cells incubated with an isotype matched control antibody. To study homing of long-term repopulating stem cells, BM cells were first incubated with anti-integrin alpha 6 or anti-integrin alpha 4 or control antibody, and then injected intravenously into lethally irradiated primary recipients. After three hours, BM cells of the primary recipients were analysed by competitive repopulation assay in secondary recipients. Blood analysis up to 16 weeks after transplantation showed that no reduction of stem cell reconstitution from integrin a6 antibody treated cells as compared to cells treated with control antibody. In accordance with this, fetal liver HSC from integrin a6 gene deleted embryos did not show any impairment of homing and engraftment in BM as compared to normal littermates. These results suggest that integrin a6 plays an important developmentally regulated role for homing of distinct hematopoietic stem and progenitor cell populations in vivo.


Blood ◽  
1999 ◽  
Vol 93 (1) ◽  
pp. 80-86 ◽  
Author(s):  
Shai Erlich ◽  
Silvia R.P. Miranda ◽  
Jan W.M. Visser ◽  
Arie Dagan ◽  
Shimon Gatt ◽  
...  

Abstract The general utility of a novel, fluorescence-based procedure for assessing gene transfer and expression has been demonstrated using hematopoietic stem and progenitor cells. Lineage-depleted hematopoietic cells were isolated from the bone marrow or fetal livers of acid sphingomyelinase–deficient mice, and retrovirally transduced with amphotropic or ecotropic vectors encoding a normal acid sphingomyelinase (ASM) cDNA. Anti–c-Kit antibodies were then used to label stem- and progenitor-enriched cell populations, and the Bodipy fluorescence was analyzed in each group after incubation with a Bodipy-conjugated sphingomyelin. Only cells expressing the functional ASM (ie, transduced) could degrade the sphingomyelin, thereby reducing their Bodipy fluorescence as compared with nontransduced cells. The usefulness of this procedure for the in vitro assessment of gene transfer into hematopoietic stem cells was evaluated, as well as its ability to provide an enrichment of transduced stem cells in vivo. To show the value of this method for in vitro analysis, the effects of retroviral transduction using ecotropic versus amphotropic vectors, various growth factor combinations, and adult bone marrow versus fetal liver stem cells were assessed. The results of these studies confirmed the fact that ecotropic vectors were much more efficient at transducing murine stem cells than amphotropic vectors, and that among the three most commonly used growth factors (stem cell factor [SCF] and interleukins 3 and 6 [IL-3 and IL-6]), SCF had the most significant effect on the transduction of stem cells, whereas IL-6 had the most significant effect on progenitor cells. In addition, it was determined that fetal liver stem cells were only approximately twofold more “transducible” than stem cells from adult bone marrow. Transplantation of Bodipy-selected bone marrow cells into lethally irradiated mice showed that the number of spleen colony-forming units that were positive for the retroviral vector (as determined by polymerase chain reaction) was 76%, as compared with 32% in animals that were transplanted with cells that were nonselected. The methods described within this manuscript are particularly useful for evaluating hematopoietic stem cell gene transfer in vivo because the marker gene used in the procedure (ASM) encodes a naturally occurring mammalian enzyme that has no known adverse effects, and the fluorescent compound used for selection (Bodipy sphingomyelin) is removed from the cells before transplantation.


Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 559-559
Author(s):  
Joachim R. Gothert ◽  
Sonja E. Gustin ◽  
Mark A. Hall ◽  
Anthony R. Green ◽  
Berthold Gottgens ◽  
...  

Abstract Evidence for the direct lineage relationship between embryonic and adult hematopoietic stem cells (HSCs) in the mouse is primarily indirect. In order to study this relationship in a direct manner we expressed the tamoxifen-inducible Cre-ERT-recombinase under the control of the SCL-stem-cell-enhancer in transgenic mice (HSC-SCL-Cre-ERT). To determine functionality, HSC-SCL-Cre-ERT transgenics were bred with the Cre-reporter-mice ROSA26R and R26R-EYFP. Flow-cytometric and transplantation studies revealed tamoxifen-dependent recombination occurring in more than 90% of adult long-term HSCs, whereas the targeted proportion within mature progenitor populations was significantly lower. Moreover, the transgene was able to irreversibly tag embryonic HSCs on days 10 and 11 of gestation. These cells contributed to bone marrow hematopoiesis five months later. In order to investigate whether the de novo HSC-generation is completed during embryogenesis, HSC-SCL-Cre-ERT marked fetal liver cells were transplanted into adult recipients. Strikingly, the proportion of marked cells within the transplanted and the in vivo-remaining HSC-compartment was not different, implying that no further HSC-generation occurred during late fetal and neonatal stages of development. These data demonstrate for the first time the direct lineage relationship between mid-gestation embryonic and adult HSCs in the mouse. Additionally, the HSC-SCL-Cre-ERT mice will provide a valuable tool to achieve temporally controlled genetic manipulation of HSCs.


Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 857-857
Author(s):  
Gregor B. Adams ◽  
Ian R. Alley ◽  
Karissa T. Chabner ◽  
Ung-il Chung ◽  
Emily S. Marsters ◽  
...  

Abstract During development, hematopoietic stem cells (HSCs) translocate from the fetal liver to the bone marrow, which remains the site of hematopoiesis throughout adulthood. In the bone marrow the HSCs are located at the endosteal surface, where the osteoblasts are a key component of the stem cell niche. The exogenous signals that specifically direct HSCs to the bone marrow have been thought to include stimulation of the chemokine receptor CXCR4 by its cognate ligand stromal derived factor-1α (SDF-1α or CXCL12). However, experiments in which CXCR4−/− fetal liver hematopoietic cells were transplanted into wild-type hosts demonstrated efficient engraftment of the HSCs in the bone marrow. In addition, treatment of HSCs with inhibitors of Gαi-coupled signaling, which blocks transmigration towards SDF-1αin vitro, does not affect bone marrow homing and engraftment in vivo. Therefore, we examined whether Gsα-coupled mechanisms play a key role in the engraftment of the HSCs in the bone marrow environment. Utilizing an inducible-conditional knockout of Gsα, we found that deletion of the gene in hematopoietic bone marrow cells did not affect their ability to perform in the in vitro primitive CFU-C or LTC-IC assay systems. However, Gsα−/− cells were unable to establish effective hematopoiesis in the bone marrow microenvironment in vivo in a competitive repopulation assay (41.1% contribution from wild-type cells versus 1.4% from knockout cells). These effects were not due to an inability of the cells to function in the bone marrow in vivo as deletion of Gsα following establishment of hematopoiesis had no effects on the HSCs. Examining the ability of the HSCs to home to the bone marrow, though, demonstrated that deletion of Gsα resulted in a marked impairment of the ability of the stem cells to localize to the marrow space (approximately 9-fold reduction in the level of primitive cell homing). Furthermore, treatment of BM MNCs with an activator of Gsα augmented the cells homing and thus engraftment potential. These studies demonstrate that Gsα is critical to the localization of HSCs to the bone marrow. Which receptors utilize this pathway in this context remains unknown. However, Gsα represents a previously unrecognized signaling pathway for homing and engraftment of HSCs to bone marrow. Pharmacologic activation of Gsα in HSC ex vivo prior to transplantation offers a potential method for enhancing stem cell engraftment efficiency.


Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 373-373 ◽  
Author(s):  
Chinavenmeni S. Velu ◽  
Sarah Porteous ◽  
Haiming Xu ◽  
Avinash M. Baktula ◽  
Philip Roehrs ◽  
...  

Abstract The Growth factor independent -1 (Gfi1) transcriptional repressor regulates both hematopoietic stem cell (HSC) self renewal and myeloid differentiation. Gfi1 null mice eventually die of HSC exhaustion, and Gfi1−/− HSC are not competitive in transplantation assays. Here we show that Gfi1 is a master regulator of microRNAs and that transcriptional control of a microRNA gene is critical for Gfi1-directed stem cell competitiveness and myelopoiesis. First, we show that the gene encoding miR21 is a direct transcriptional target of Gfi1. Chromatin immunoprecipitation and electrophoretic mobility shift assays reveal Gfi1 binding to specific DNA sequences upstream of the miR21 stem loop. Moreover, the expression of Gfi1 and miR21 is reciprocal in 1) wild type and Gfi1−/− marrow cells, 2) during normal differentiation from common myeloid progenitors (CMP) to granulocyte monocyte progenitors (GMP), and 3) during treatment-induced differentiation of human myeloid leukemia cell lines. Forced expression of Gfi1 lowers miR21 levels in wild type Lin− bone marrow cells and human cancer cell lines. Knockdown of Gfi1 expression with shRNA in human cancer cell lines increases miR21 expression. Moreover, conditional deletion of Gfi1 induces miR21 expression in primary murine hematopoietic cells, including sorted CMP and GMP. Thus, Gfi1 transcriptionally regulates miR21 in both human and murine hematopoietic cells. Interestingly, we find that the Ski oncoprotein/transcriptional corepressor is a direct target of miR-21. Subsequently, Ski is dramatically reduced in Gfi1−/− HSC and in wild type bone marrow Lin− cells forced to express miR21. Gfi1 may repress miR21 to maintain functional competence. Specifically, we find that Ski is a previously undescribed Gfi1 corepressor. Both endogenous Ski and Gfi1 physically interact. Synthetic Ski and Gfi1 proteins reveal that the interaction is both strong and specific. Chromatin immunoprecipitation reveals Ski and Gfi1 occupy several Gfi1 target genes. However, Ski function is critical as a corepressor on only a subset of Gfi1 target genes. To determine the importance of Ski corepression to Gfi1 induced biology, we examined two well established phenotypes of Gfi1 loss of function; HSC competitiveness and myelopoiesis. When Gfi1−/− embryonic stem cells are injected into a wild type blastocyst, they do not participate in hematopoiesis. Similarly, we find that when Ski−/− embryonic stem cells are injected into a blastocyst, they infrequently participate in hematopoeisis. Next, because Ski−/− animals die at or before birth, we examined the fitness of Ski−/− fetal liver HSC. In competitive transplantation assays, Ski−/− fetal liver HSC were significantly impaired in reconstitution compared to congenic wild-type competitor fetal-liver HSC. Moreover, Ski null HSC generated significantly less myeloid progeny. Thus, Ski−/− HSC display a partial phenocopy of Gfi1−/− hematopoiesis. We conclude that Gfi1 directly targets miR21 to control the expression of Ski, a corepressor for Gfi1, and that the Gfi1/Ski complex is critical to regulate a subset of Gfi1 target genes important for HSC fitness and myeloid cell production.


Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1403-1403
Author(s):  
Chinavenmeni S. Velu ◽  
Michael Berk ◽  
Haiming Xu ◽  
Tristan Bourdeau ◽  
Avedis Kazanjian ◽  
...  

Abstract Ski is a corepressor protein originally identified as a retrovirally transduced oncoprotein. Genetic deletion of Ski has revealed essential roles in multiple developmental processes. Suggestion that Ski may play a role in hematopoiesis first came from expression of v-Ski and c-Kit, which induced the continuous in vitro growth of primary avian multipotent progenitors. However, the hematopoietic phenotype of Ski−/− mice has not been described. Here, we show that Ski loss of function results in loss of hematopoietic stem cell (HSC) fitness and abnormal regulation of myeloid progenitor numbers. Fetal liver Ski−/− HSC engraft well in ablated recipients, but are not competitive in engraftment. Moreover, Ski null embryonic stem cells generate many tissues in chimeras, but infrequently participate in hematopoiesis. Thus, Ski null HSC are not competitive in both transplant and chimera settings, indicating a defect in stem cell fitness. Engrafted Ski−/− fetal liver cells generate fewer myeloid lineage cells than wild type littermates, and accumulate granulocytemonocyte progenitors. Growth factor independent -1 (Gfi1) is a transcriptional repressor that controls HSC maintenance and myeloid progenitor differentiation. Gfi1−/− and Ski−/− hematopoietic stem and myeloid progenitor phenotypes are strikingly similar. We find that Ski functions as a corepressor for Gfi1. Both endogenous and synthetic Gfi1 and Ski physically interact in vitro and upon Gfi1 target genes. Knockdown of Gfi1 or Ski results in derepression of these targets. Thus, our results provide a molecular link between the similar HSC and myeloid progenitor phenotypes engendered by Gfi1 or Ski deletion.


Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2430-2430
Author(s):  
Rui Lu ◽  
Ping Wang ◽  
Trevor Parton ◽  
Deyou Zheng ◽  
Gang Greg Wang

Abstract DNA Methyltransferase 3A (DNMT3A) is frequently mutated in various hematopoietic malignancies; however, the underlying oncogenic mechanisms remain elusive. Here, we establish ex vivo and in vivo leukemogenic models recapitulating synergy between a DNMT3A 'hotspot' mutation (i.e., DNMT3AR882H) and kinase activation, which include a leukemia-initiating stem cell (LSC) model. We show that DNMT3AR882H cooperates with constitutively activated RAS (NRAS G12D) in transforming murine hematopoietic stem/progenitor cells (HSPCs) ex vivo and inducing acute leukemias in vivo. Genome-wide transcriptome profiling analysis of these models reveals that DNMT3AR882H potentiates aberrant transactivation of 'stemness' gene expression programs, notably a set of transcription factors Meis1, Hox-A, Mn1 and Mycn. Further examination by ChIP-Seq and enhanced Reduced Representation Bisulfite Sequencing (eRRBS) demonstrate that R882-mutated DNMT3A enzymes directly binds to cis-regulatory elements of these genes and induces focal CpG hypomethylation reminiscent of what was seen in human leukemias bearing DNMT3A R882 mutation. Furthermore, DNMT3AR882H-induced DNA hypomethylation facilitates gene enhancer/promoter activation and recruitment of Dot1l-associated transcription elongation machineries. Lastly, with these established leukemogenic model systems, we also demonstrate profound differences between R882-mutated and wild-type DNMT3A in mediating oncogenic transformation, epigenetic dysregulation and gene mis-regulation. Collectively, these findings not only mechanistically explain clonal and malignant hematopoiesis found associated with DNMT3A mutation but also establish targeting transcription elongation machineries as novel therapeutic avenues for DNMT3A-mutated hematological malignancies. Disclosures No relevant conflicts of interest to declare.


2018 ◽  
Vol 115 (31) ◽  
pp. E7379-E7388 ◽  
Author(s):  
Laura J. Smith ◽  
Jason Wright ◽  
Gabriella Clark ◽  
Taihra Ul-Hasan ◽  
Xiangyang Jin ◽  
...  

The precise correction of genetic mutations at the nucleotide level is an attractive permanent therapeutic strategy for human disease. However, despite significant progress, challenges to efficient and accurate genome editing persist. Here, we report a genome editing platform based upon a class of hematopoietic stem cell (HSC)-derived clade F adeno-associated virus (AAV), which does not require prior nuclease-mediated DNA breaks and functions exclusively through BRCA2-dependent homologous recombination. Genome editing is guided by complementary homology arms and is highly accurate and seamless, with no evidence of on-target mutations, including insertion/deletions or inclusion of AAV inverted terminal repeats. Efficient genome editing was demonstrated at different loci within the human genome, including a safe harbor locus, AAVS1, and the therapeutically relevant IL2RG gene, and at the murine Rosa26 locus. HSC-derived AAV vector (AAVHSC)-mediated genome editing was robust in primary human cells, including CD34+cells, adult liver, hepatic endothelial cells, and myocytes. Importantly, high-efficiency gene editing was achieved in vivo upon a single i.v. injection of AAVHSC editing vectors in mice. Thus, clade F AAV-mediated genome editing represents a promising, highly efficient, precise, single-component approach that enables the development of therapeutic in vivo genome editing for the treatment of a multitude of human gene-based diseases.


JCI Insight ◽  
2020 ◽  
Vol 5 (16) ◽  
Author(s):  
Hongjie Wang ◽  
Aphrodite Georgakopoulou ◽  
Chang Li ◽  
Zhinan Liu ◽  
Sucheol Gil ◽  
...  

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