Unknown,Transcriptomics,Genomics,Proteomics

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The chromatin-modifying enzyme Ezh2 is a CD28-dependent molecule critical for the maintenance of Treg identity

ABSTRACT: Regulatory T cells (Tregs) are essential for maintaining proper immune homeostasis. Extracellular signals (e.g. TCR, CD28, IL-2R) are necessary for the generation and maintenance of Tregs, but how these signals are integrated to control the gene expression patterns of Tregs is less clear. Here we show that the epigenetic regulator, Ezh2, was induced by CD28 costimulation and Ezh2 activity was elevated in Tregs as compared to conventional CD4+ T cells. Deletion of Ezh2 in mouse Tregs led to a progressive autoimmune disease because Tregs were compromised after activation, losing proper control of essential Treg lineage genes and adopting a gene expression pattern similar to Foxp3-deficient ‘Tregs.’ Lineage-tracing of Ezh2-deficient Tregs in vivo confirmed that the cells were destabilized selectively in activated Treg populations, which led to a significant loss of Tregs in non-lymphoid tissues. These studies reveal an essential role for Ezh2 in the maintenance of Treg “identity” during cellular activation and differentiation. RNAseq of sorted populations of CD62Lhi or CD62Llo Tregs for both Ezh2-HET (Foxp3YFP-Cre/Foxp3WT;Ezh2fl/+ female mice) and Ezh2-KO (Foxp3YFP-Cre/Foxp3WT;Ezh2fl/fl female mice) were generated, in triplicate for each condition, using Illumina HiSeq 2500 single-end 50bp sequencing platform.

ORGANISM(S): Mus musculus

SUBMITTER: GAURAV CHOPRA

PROVIDER: E-GEOD-58998 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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The chromatin-modifying enzyme Ezh2 is critical for the maintenance of regulatory T cell identity after activation.

DuPage Michel M Chopra Gaurav G Quiros Jason J Rosenthal Wendy L WL Morar Malika M MM Holohan Dan D Zhang Ruan R Turka Laurence L Marson Alexander A Bluestone Jeffrey A JA

Immunity 20150210 2

Regulatory T cells (Treg cells) are required for immune homeostasis. Chromatin remodeling is essential for establishing diverse cellular identities, but how the epigenetic program in Treg cells is maintained throughout the dynamic activation process remains unclear. Here we have shown that CD28 co-stimulation, an extracellular cue intrinsically required for Treg cell maintenance, induced the chromatin-modifying enzyme, Ezh2. Treg-specific ablation of Ezh2 resulted in spontaneous autoimmunity wit ...[more]

PMID: 25680271

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Project description:The mechanistic target of rapamycin (mTOR) pathway integrates diverse environmental inputs, including immune signals and metabolic cues, to direct T cell fate decisions1. Activation of mTOR, comprised of mTORC1 and mTORC2 complexes, delivers an obligatory signal for proper activation and differentiation of effector CD4+ T cells2,3, whereas in the regulatory T cell (Treg) compartment, the Akt-mTOR axis is widely acknowledged as a crucial negative regulator of Treg de novo differentiation4-8 and population expansion9. However, whether mTOR signaling affects the homeostasis and function of Tregs remains largely unexplored. Here we show that mTORC1 signaling is a pivotal positive determinant of Treg function. Tregs have elevated steady-state mTORC1 activity compared to naïve T cells. Signals via T cell receptor (TCR) and IL-2 provide major inputs for mTORC1 activation, which in turn programs suppressive function of Tregs. Disruption of mTORC1 through Treg-specific deletion of the essential component Raptor leads to a profound loss of Treg suppressive activity in vivo and development of a fatal early-onset inflammatory disorder. Mechanistically, Raptor/mTORC1 signaling in Tregs promotes cholesterol/lipid metabolism, with the mevalonate pathway particularly important for coordinating Treg proliferation and upregulation of suppressive molecules CTLA-4 and ICOS to establish Treg functional competency. In contrast, mTORC1 does not directly impact the expression of Foxp3 or anti- and pro-inflammatory cytokines in Tregs, suggesting a non-conventional mechanism for Treg functional regulation. Lastly, we provide evidence that mTORC1 maintains Treg function partly through inhibiting the mTORC2 pathway. Our results demonstrate that mTORC1 acts as a fundamental ‘rheostat’ in Tregs to link immunological signals from TCR and IL-2 to lipogenic pathways and functional fitness, and highlight a central role of metabolic programming of Treg suppressive activity in immune homeostasis and tolerance. We used microarrays to explore the gene expression profiles differentially expressed in regulatory T-cells from wild-type and CD4(cre) x Raptor(fl/fl) mice

Project description:Differentiation of naïve CD4+ T cells into effector (Th1, Th2 and Th17) and induced regulatory (iTreg) T cells requires lineage-specifying transcription factors and epigenetic modifications that allow appropriate repression or activation of gene transcription. The epigenetic silencing of cytokine genes is associated with the repressive H3K27 trimethylation mark, mediated by Ezh2 or Ezh1 methyltransferase components of the polycomb repressive complex 2 (PRC2). EZH2 over-expression and activating mutations are implicated in tumorigenesis and correlate with poor prognosis in several tumor types 35. This spurred the development of EZH2 inhibitors which, by inducing tumor cell growth arrest and cell death, show therapeutic promise in cancer. A role for Ezh2 in suppressing Th1 and Th2 cytokine production and survival has recently been reported. It is not entirely clear whether Ezh2-PRC2 plays a role in H3K27me3 in cytokine loci in naïve CD4+ T cells and whether H3K27me3 has a non-redundant role in T helper cell lineage differentiation and survival. Here, we investigate the effects of T cell-specific Ezh2 deletion to determine the role that Ezh2-PRC2 plays in regulating the fate of differentiating naïve CD4+ T cells. Loss of Ezh2 altered the expression of 1328 genes in Th0 and 1979 genes in iTreg cells. Gene expression changes were positively correlated in both cell types, indicating that Ezh2 targets similar genes in these cells. As expected, Ifng was one of the genes most increased in expression by following loss of Ezh2. In addition, expression of Tbx21 homolog Eomes, a transcription factor that regulates IFNG production, was also significantly increased. We then performed H3K27me3 ChIP-seq on Ezh2fl/fl and Ezh2fl/fl.CD4Cre Th0 cells. Consistent with cellular phenotype and RNA-seq data, we observed a loss of the H3K27me3 at Eomes, Il4 and Il10 loci . Very low levels of H3K27me3 marks were present at Ifng and Tbx21 loci in differentiated Ezh2fl/fl Th0 cells, suggesting that upon differentiation, upregulation or activation of transcription factors accounts for IFNG overproduction. A significant loss of H3K27me3 was observed >2kb upstream of Gata3 locus , however this did not result in increased transcription . Of the 22381 genes tested for changes in H3K27me3, 1360 showed a statistically significant decrease in Ezh2fl/fl.CD4Cre Th0 cells, compared to wildtype. Furthermore, 404 of these genes also showed a concomitant gain in expression in Ezh2fl/fl.CD4Cre Th0 cells, suggesting that these loci are likely direct Ezh2-PRC2 targets. There are 3 biological replicates each of Ezh2fl/fl.CD4Cre and Ezh2fl/fl in both Th0 and iTreg cells for the RNA-seq experiment. There are 2 biological replicates each of Ezh2fl/fl.CD4Cre and Ezh2fl/fl in Th0 cells for the ChIP-seq experiment.

Dataset Information

The chromatin-modifying enzyme Ezh2 is a CD28-dependent molecule critical for the maintenance of Treg identity

Publications

The chromatin-modifying enzyme Ezh2 is critical for the maintenance of regulatory T cell identity after activation.

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