Unknown,Transcriptomics,Genomics,Proteomics

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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)

ORGANISM(S): Mus musculus

SUBMITTER: Genotypic technology

PROVIDER: E-GEOD-75294 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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: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 Affymetrixâ¢ platform. As a control, profiling was also performed with LSK cells expressing unmodified constitutively active HOXB4 (HOXB4const) Â± 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.

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Identify gene expression signatures in the niche cells (CD45 negative) during proliferation of Hematopoietic stem cells (LSK)

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