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Investigating genes regulated by mir-155 in a mouse macrophage cell line

ABSTRACT: Mammalian microRNAs (miRNAs) are emerging as key regulators of the development and function of the immune system. Here, we report a strong but transient induction of miR-155 in mouse bone marrow after injection of bacterial lipopolysaccharide (LPS) correlated with granulocyte/monocyte (GM) expansion. Demonstrating the sufficiency of miR-155 to drive GM expansion, enforced expression in mouse bone marrow cells caused GM proliferation in a manner reminiscent of LPS treatment. However, the mir-155-induced GM populations displayed pathological features characteristic of myeloid neoplasia. Extending possible relevance to human disease, miR-155 was overexpressed in the bone marrow of patients with acute myeloid leukemia (AML). Furthermore, miR-155 repressed a subset of genes implicated in hematopoietic development and disease. These data implicate miR-155 as a contributor to physiological GM expansion during inflammation and to certain pathological features associated with AML, emphasizing the importance of proper miR-155 regulation in developing myeloid cells during times of inflammatory stress. Keywords: genetic modification

ORGANISM(S): Mus musculus

PROVIDER: GSE10467 | GEO | 2008/03/24

SECONDARY ACCESSION(S): PRJNA108027

REPOSITORIES: GEO

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Project description:To investigate the pathological effect of miR-126 on the progression of acute myeloid leukemia (AML) induced by AML1-ETO9a (AE9a), we conducted a series of mouse bone marrow transplantation (BMT) assays with the following groups: AE9a (primary donor cells were wild-type mouse bone marrow progenitor (i.e., lineage negative; Lin-) cells retrovirally transduced with MSCV-PIG-AE9a), AE9a+miR-126 (primary donor cells were wild-type mouse bone marrow progenitor (i.e., Lin-) cells retrovirally transduced with MSCV-PIG-AE9a-miR-126), and miR-126KO+AE9a (primary donor cells were miR-126 knockout mouse bone marrow progenitor (i.e., Lin-) cells retrovirally transduced with MSCV-PIG-AE9a), along with a control group (primary donor cells were wild-type mouse bone marrow progenitor (i.e., Lin-) cells retrovirally transduced with MSCV-PIG empty vector). The control group was only used in the primary and secondary BMT assays, whereas the three leukemic groups including AE9a, AE9a+miR-126 and miR-126KO+AE9a were used in four passages (i.e., primary, secondary, tertiary and quaternary) of BMT assays. Then, gene expression profiling was conducted with bone marrow samples collected from different groups to decipher the molecular mechanisms underlying miR-126 effects on leukemia initiation and progression and maintenance and self-renewal of leukemia stem/initiating cells. A total of 39 mouse bone marrow samples including 36 mouse AML samples with AE9a, AE9a+miR-126, and miR-126KO+AE9a collected from the 1st, 2nd, 3rd and 4th passages of BMT recipient mice (3 mice for each group in each passage), along with 3 normal controls from the 1st passage of BMT, were analyzed by use of Affymetrix GeneChip Mouse Gene 2.0 ST Array (Affymetirx, Santa Clara, CA). For each sample, the CD45.1+ cells (i.e., transplanted donor cells) were sorted with flow cytometry from whole BM cells collected from BMT recipient mice at the end stage. Then total RNA was isolated by use of miRNeasy extraction kit (Qiagen, Valencia, CA).

Project description:Toll-like receptor (TLR)-induced maturation of dendritic cells (DCs) leads to the production of proinflammatory cytokines as well as the upregulation of various molecules involved in T cell activation. These are believed to be the critical events that account for the induction of the adaptive immune response. Here, we have examined the role of micro-RNA-155 (miR-155) in DC function and the induction of immunity. Using a model where the transfer of self-antigen-pulsed, TLR-matured DCs can induce a functional CD8 T cell response and autoimmunity, we find that DCs lacking miR-155 have an impaired ability to break immune tolerance. Importantly, transfer of self- antigen-pulsed DCs overexpressing miR-155 was sufficient to break tolerance in the absence of TLR stimuli. Although these unstimulated DCs induced T cell function in vivo, there was no evidence for the upregulation of costimulatory ligands or cytokine secretion. Further analysis showed that miR-155 influenced the level of the phosphatase SHIP1 in DCs, and that the lack of SHIP1 in DCs was sufficient to break T cell tolerance in vivo, again in the absence of TLR induced DC maturation. Our study demonstrates that the overexpression of miR-155 in DCs is a critical event that is alone sufficient to break self tolerance and promote a CD8-mediated autoimmune response in vivo. This process is independent of the induction of conventional DC maturation markers, indicating that miR-155 regulation of SHIP represents a unique axis that regulates DC function in vivo. Dendritic cell culture: Bone marrow was flushed from tibias and femurs of mice with HBSS. Bone marrow cells were cultured at 2x106 cells/ml in 10 ml non-tissue culture treated dishes in RPMI 1640 containing 10% LPS-free FBS, Penicillin:streptomycin glutamine 2-mercaptoethanol (cRPMI), with 40ng/ml murine GM-CSF (Peprotech). On day 3 of cultures 10ml of fresh media was added also containing 40ng/ml GM-CSF. On days 6 and 8, 10ml of media was removed and centrifuged to collect cells, which were resuspended in 10ml fresh media containing GM-CSF and were added back to dishes. Non-adherent cells were isolated on day 9. DCs were plated in 24-well plates at 2x106 cells/ml in 1ml of cRPMI with or without the class B CpG ODN1826 (ACGT DNA Technologies corporation, Toronto, ON, Canada) at 10?M final concentration overnight. Array analysis of mi-RNA expression: BMDCs from WT mice were either stimulated with CpG or left in media alone overnight. Whole RNA was isolated using mirVana miRNA isolation kit following the manufacturers instructions. RNA samples were labeled and hybridized to Agilent mouse miRNA 8x15K arrays (Agilent). Data was generated from 8 individual samples (4 unstimulated and 4 CpG-treated).

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Investigating genes regulated by mir-155 in a mouse macrophage cell line

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