Identify gene expression signatures in the niche cells (CD45 negative) during proliferation of Hematopoietic stem cells (LSK)
ABSTRACT: To further identify gene expression signatures in the niche cells (CD45 negative) during proliferation of Hematopoietic stem cells (LSK), we employed mice whole genome (60K) microarray expression profiling as a discovery platform to identify the up-regulated and down-regulated genes of the niche. [Samples A-D] In this experiment a physiological stress model was created where the recipient mice were subjected to sub lethal radiation (700 CGy) following a transplantation of 30,000 LSK cells (HSCs). Bone marrow cells were isolated on day 0 (before transplantation) and day 10 (post transplantation of 30,000 LSK cells when maximum proliferation of HSCs was observed). Donor HSCs was sorted by FACS following RNA isolation and cDNA synthesis followed by single color global gene expression analysis. Agilent one-color experiment,Organism:Mouse, Agilent Whole Genome Mouse 8x60k (AMADID: 26986) , Labeling kit: Agilent Quick-Amp labeling Kit (p/n5190-0442)
Project description:To further identify gene expression signatures in the niche cells (CD45 negative) during proliferation of Hematopoietic stem cells (LSK), we employed mice whole genome (60K) microarray expression profiling as a discovery platform to identify the up-regulated and down-regulated genes of the niche. [Samples A-D] In this experiment a physiological stress model was created where the recipient mice were subjected to sub lethal radiation (700 CGy) following a transplantation of 30,000 LSK cells (HSCs). Bone marrow cells were isolated on day 0 (before transplantation) and day 10 (post transplantation of 30,000 LSK cells when maximum proliferation of HSCs was observed). Donor HSCs was sorted by FACS following RNA isolation and cDNA synthesis followed by single color global gene expression analysis. Agilent one-color experiment,Organism:Mouse, Agilent Whole Genome Mouse 8x60k (AMADID: 26986) , Labeling kit: Agilent Quick-Amp labeling Kit (p/n5190-0442)
Project description:The transcription factor SOX17 is expressed by fetal, but not adult hematoipoietic stem cells (HSCs), and is required for the maintenance of fetal and neonatal, but not adult, HSCs. In the current study we show that ectopic expression of Sox17 in adult HSCs and transiently reconstituting multipotent progenitors was sufficient to confer increased self-renewal potential and the expression of fetal HSC genes including fetal HSC surface markers. To assess the mechanisms by which ectopic Sox17 expression in adult hematopoietic progenitors increased self-renewal potential and conferred fetal HSC properties, we compared the gene expression profiles of E16.5 fetal liver HSCs, young adult bone marrow HSCs, young adult bone marrow CD48+LSK cells, and Sox17-expressing CD48+LSK cells isolated from mice that had been transplanted with MSCV-Sox17-infected bone marrow cells 12 weeks earlier. Total RNA (~5ng) was isolated from 3 independent, freshly isolated aliquots of 10,000 E16.5 fetal liver HSCs, 10,000 fetal liver CD48+LSK cells, 10,000 adult bone marrow HSCs, 10,000 adult bone marrow CD48+LSK cells, 10,000 Sox17-expressing CD48+LSK cells isolated from primary recipients 12 weeks after transplantation of MSCV-Sox17-infected bone marrow cells. Purified RNA was reverse transcribed and amplified using the WT-Ovation™ Pico RNA Amplification system (NuGEN Technologies) following the manufacturer’s instructions. Sense strand cDNA was generated using WT-Ovation™ Exon Module (NuGEN), then fragmented and labeled using the FL-Ovation™ cDNA Biotin Module V2 (NuGEN). 2.5µg of labeled cDNA were hybridized to Affymetrix Mouse Gene ST 1.0 microarrays.
Project description:Bone marrow hematopoietic stem cells (HSCs) balance proliferation and differentiation by integrating complex transcriptional and post-translational mechanisms regulated by cell intrinsic and extrinsic factors. We found that transcripts of G(0)/G(1) switch gene 2 (G0S2) are enriched in lineage(-) Sca-1(+) c-kit(+) (LSK) CD150(+) CD48(-) CD41(-) cells, a population highly enriched for quiescent HSCs, whereas G0S2 expression is suppressed in dividing LSK CD150(+) CD48(-) cells. Gain-of-function analyses using retroviral expression vectors in bone marrow cells showed that G0S2 localizes to the mitochondria, endoplasmic reticulum, and early endosomes in hematopoietic cells. Co-transplantation of bone marrow cells transduced with the control or G0S2 retrovirus led to increased chimerism of G0S2-overexpressing cells in femurs, although their contribution to the blood was reduced. This finding was correlated with increased quiescence in G0S2-overexpressing HSCs (LSK CD150(+) CD48(-)) and progenitor cells (LS(-)K). Conversely, silencing of endogenous G0S2 expression in bone marrow cells increased blood chimerism upon transplantation and promoted HSC cell division, supporting an inhibitory role for G0S2 in HSC proliferation. A proteomic study revealed that the hydrophobic domain of G0S2 interacts with a domain of nucleolin that is rich in arginine-glycine-glycine repeats, which results in the retention of nucleolin in the cytosol. We showed that this cytosolic retention of nucleolin occurs in resting, but not proliferating, wild-type LSK CD150(+) CD48(-) cells. Collectively, we propose a novel model of HSC quiescence in which elevated G0S2 expression can sequester nucleolin in the cytosol, precluding its pro-proliferation functions in the nucleolus.
Project description:The transcriptional coactivator Cbp is critical for hematopoietic stem cell (HSC) development. However, its role in adult HSC and the mechanistic detail of Cbp control of HSC function remains unknown. Using conditional deletion of Cbp in the adult HSC compartment, we demonstrate an altered balance between differentiation and self-renewal with gradual loss of phenotypic HSC, differentiation defects in lower compartments and the development of myeloid malignancies. In addition, we demonstrate that Cbp -/- HSCs reconstitute hematopoiesis with lower efficiency than their wild type counterparts and readily exhaust over time when placed under the replicative stress of serial transplantation. Furthermore, we demonstrate abnormal cell cycle (re)entry and apoptosis in HSC which, with preferential differentiation, also contribute to stem cell exhaustion. Finally we demonstrate global transcriptional abnormalities predicted to alter cell cycle control, balanced differentiation and HSC function upon Cbp deletion and link Cbp to a critical HSC transcriptional regulatory network through genome-wide analysis of Cbp binding. Genome-wide gene expression analysis of LSK population after Cbp deletion. The LSK population of bone marrow is enriched for hematopoietic stem cells. Total RNA was extracted from flow-sorted LSK population of bone marrow, 4 weeks after pIpC induced deletion of Cbp. 2 replicates for Cbp wt control, 2 replicates for Cbp Mx.
Project description:Thrombopoietin (Thpo) signals via its receptor Mpl and regulates megakaryopoiesis, hematopoietic stem cell (HSC) maintenance and post-transplant expansion. Mpl expression is tightly controlled and deregulation of Thpo/Mpl-signaling is linked to hematological disorders. Here, we constructed an intracellular-truncated, signaling deficient Mpl protein which is presented on the cell surface (dnMpl). The transplantation of bone marrow cells retrovirally transduced to express dnMpl into wildtype mice induced thrombocytopenia, and a progressive loss of HSC. Functional analysis of the truncated Mpl in vitro and in vivo demonstrated no internalization after Thpo binding and the inhibition of Thpo/Mpl-signaling in wildtype cells due to dominant-negative (dn) effects by receptor competition with wildtype Mpl for Thpo binding. Gene expression analysis was performerd of Lin-Sca1+cKit+ (LSK) cells isolated from mice transplanted with dnMpl transduced BM cells. The gene expression profile supported the exhaustion of HSC due to increased cell cycle progression and identified new and known downstream effectors of Thpo/Mpl-signaling in HSC (namely TIE2, ESAM1 and EPCR detected on the HSC-enriched LSK cell population). In summary, we established a novel way of Thpo/Mpl inhibition in the adult mouse and performed in depth analysis of the phenotype including gene expression profiling. BM cells were flushed from the femurs and tibias of C57Bl/6 donor mice. Lineage-marker negative (lin-) cells were isolated by magnetic cell sorting using lineage-specific antibodies (GR1, CD11b, CD45R/B220, CD3e, TER-119). Prior to viral transduction, lin- BM cells were prestimulated for 24-48h in StemSpan, containing 10 ng/ml murine SCF, 20 ng/ml murine Thpo, 10 ng/ml recombinant human FGF-1, 20 ng/ml murine IGF2, 1% penicillin/streptomycin, 2 mM glutamine. Lin- cells were transduced twice on two following days with an MOI of 10 with retroviral vectors on Retronectin coated and preloaded wells (10 μg/cm2). On day four after isolation, 5x10^5 cells/mouse were intravenously injected into lethally irradiated C57Bl/6 mice (10 Gy). Eight weeks after transplantation Lin-Sca1+cKit+ (LSK) cells were isolated from dnMpl and control transplanted mice by fluorescent activated cell sorting. For each sample, BM of 2-5 mice were pooled. RNA was isolated using RNeasy Micro Kit (Qiagen GmbH, Hilden, Germany). RNA quality was assessed using the Agilent 2100 Bioanalyzer.
Project description:In this study we demonstrate that Tgif1 has a role in HSCs maintenance, self-renewal and quiescence. RNA sequencing data of LSK cells (HSCs enriched cell population) from Tgif1-/- and wild type mice implicates that multiple pathways involved in HSC quiescence and self-renewal are disturbed in Tgif1 deficient mice. RNA expression profiles of wild type (WT) and Tgif1-/- LSK cells were generated by RNA sequencing, in triplicate, using Illumina HiSeq 2000.
Project description:The mammalian target of rapamycin (mTOR) is an important regulator of hematopoietic stem cell (HSC) self-renewal and its overactivation contributes to HSC premature exhaustion in part via induction of HSC senescence. Inhibition of mTOR with rapamycin has the potential to promote long-term hematopoiesis of ex vivo expanded HSCs to facilitate the clinical application of HSC transplantation for various hematologic diseases.A well-established ex vivo expansion system for mouse bone marrow HSCs was used to investigate whether inhibition of overactivated mTOR with rapamycin can promote long-term hematopoiesis of ex vivo expanded HSCs and to elucidate the mechanisms of action of rapamycin.HSC-enriched mouse bone marrow LSK cells exhibited a time-dependent activation of mTOR after ex vivo expansion in a serum-free medium supplemented with stem cell factor, thrombopoietin, and Flt3 ligand. The overactivation of mTOR was associated with induction of senescence but not apoptosis in LSK cells and a significant reduction in the ability of HSCs to produce long-term hematopoietic reconstitution. Inhibition of overactivated mTOR with rapamycin promoted ex vivo expansion and long-term hematopoietic reconstitution of HSCs. The increase in long-term hematopoiesis of expanded HSCs is likely attributable in part to rapamycin-mediated up-regulation of Bmi1 and down-regulation of p16, which prevent HSCs from undergoing senescence during ex vivo expansion.These findings suggest that mTOR plays an important role in the regulation of HSC self-renewal in vitro and inhibition of mTOR hyperactivation with rapamycin may represent a novel approach to promote ex vivo expansion and their long-term hematopoietic reconstitution of HSCs.
Project description:HOXB4 mediates expansion of adult and embryo-derived hematopoietic stem cells (HSCs) when expressed ectopically. To define the underlying molecular mechanisms, we performed gene expression profiling in combination with subsequent functional analysis using enriched adult HSCs expressing inducible HOXB4. A substantial number of the identified HOXB4 target genes are involved in signaling pathways important for controlling self-renewal, maintenance and differentiation of stem cells. Functional assays performed on selected pathways confirmed the biological coherence of the array results. HOXB4 activity protected adult HSCs from the detrimental effects mediated by the proinflammatory cytokine TNF-alpha. Furthermore, we demonstrate that HOXB4 activity and FGF-signaling are intertwined. HOXB4-mediated expansion of adult HSCs was enhanced by specific and complete inhibition of FGF-receptors. Based on our results we propose that HOXB4 governs pivotal cell-intrinsic pathways involved in the regulation of cell cycle, differentiation and apoptosis. Our results strongly suggest that HOXB4 modulates the response of HSCs to multiple extrinsic signals in a concerted manner, thereby shifting the balance towards stem cell self-renewal. Experiment Overall Design: To understand the mechanisms of HOXB4 activity, we wished to identify target genes of HOXB4 in adult hematopoietic stem and progenitor cells (HSC/HPCs). We thus transduced murine HSC/HPCs with a retroviral vector that co-expresses EGFP and a tamoxifen-inducible form of HOXB4 (HOXB4-ER). Upon addition of 4-hydroxytamoxifen (TMX), the HOXB4-ER fusion protein translocates from the cytoplasm to the nucleus, consequently being capable of modulating gene expression. Transduced cell populations were expanded for 14 days in the presence of TMX. Thereafter, HOXB4-ER+LSK (GFP+ , lineage negative, Sca1+, ckit+) cells were flow cytometrically isolated and cultivated either with or without TMX for 1 or 4 hours. Inactivation of HOXB4 activity by TMX withdrawal was intended to mimic the naturally occurring down-regulation of HOXB4 in differentiating stem cells. RNA was prepared after the aforementioned times and the transcriptional profiles of HOXB4-ER+LSK +/- TMX analyzed using the Affymetrix™ platform. As a control, profiling was also performed with LSK cells expressing unmodified constitutively active HOXB4 (HOXB4const) ± TMX, to exclude changes in gene expression due to unknown effects of tamoxifen itself. RNAs from adult LSK cells were processed for use on Affymetrix GeneChips Mouse Genome 430 2.0. All quality parameters for the arrays were confirmed to be in the recommended range.
Project description:A balanced pool of hematopoietic stem cells (HSCs) in bone marrow is tightly regulated, and this regulation is disturbed in hematopoietic malignancies such as chronic myeloid leukemia (CML). The underlying mechanisms are largely unknown. Here we show that the Lin(-)Sca-1(+)c-Kit(-) (LSK(-)) cell population derived from HSC-containing Lin(-)Sca-1(+)c-Kit(+) (LSK) cells has significantly higher numbers of apoptotic cells. Depletion of LSK cells by radiation or the cytotoxic chemical 5-fluorouracil results in an expansion of the LSK(-) population. In contrast, the LSK(-) population is reduced in CML mice, and depletion of leukemia stem cells (LSCs; BCR-ABL-expressing HSCs) by deleting Alox5 or by inhibiting heat shock protein 90 causes an increase in this LSK(-) population. The transition of LSK to LSK(-) cells is controlled by the Icsbp gene and its downstream gene Lyn, and regulation of this cellular transition is critical for the survival of normal LSK cells and LSCs. These results indicate a potential function of the LSK(-) cells in the regulation of LSK cells and LSCs.
Project description:Exposure to total body irradiation (TBI) induces not only acute hematopoietic radiation syndrome but also long-term or residual bone marrow (BM) injury. This residual BM injury is mainly attributed to permanent damage to hematopoietic stem cells (HSCs), including impaired self-renewal, decreased long-term repopulating capacity, and myeloid skewing. These HSC defects were associated with significant increases in production of reactive oxygen species (ROS), expression of p16(Ink4a) (p16) and Arf mRNA, and senescence-associated ?-galacotosidase (SA-?-gal) activity, but not with telomere shortening or increased apoptosis, suggesting that TBI induces residual BM injury via induction of HSC premature senescence. This suggestion is supported by the finding that SA-?-gal(+) HSC-enriched LSK cells showed more pronounced defects in clonogenic activity in vitro and long-term engraftment after transplantation than SA-?-gal(-) LSK cells isolated from irradiated mice. However, genetic deletion of p16 and/or Arf had no effect on TBI-induced residual BM suppression and HSC senescence, because HSCs from irradiated p16 and/or Arf knockout (KO) mice exhibited changes similar to those seen in HSCs from wild-type mice after exposure to TBI. These findings provide important new insights into the mechanism by which TBI causes long-term BM suppression (eg, via induction of premature senescence of HSCs in a p16-Arf-independent manner).