Foxp3+ regulatory T cells (Treg cells) maintain immunological tolerance and their deficiency results in fatal multi-organ autoimmunity. Although heightened T cell receptor (TCR) signaling is critical for the differentiation of Treg cells, the role of TCR signaling in Treg cell function remains largely unknown. Here we demonstrate inducible ablation of the TCR results in Treg cell dysfunction which cannot be attributed to impaired Foxp3 expression, decreased expression of Treg cell signature genes or altered ability to sense and consume interleukin 2. Rather, TCR signaling was required for maintaining the expression of a limited subset of genes comprising 25% of the activated Treg cell transcriptional signature. Our results reveal a critical role for the TCR in Treg cell suppressor capacity.
Continuous requirement for the TCR in regulatory T cell function.
Specimen part
View SamplesDendritic cells (DCs) are critical mediators of host defense against bacteria. The goal of this microarray study was to understand the global transcriptional response of bone marrow-derived dendritic cells (BMDCs) upon exposure to live bacteria, to better understand how DCs orchestrate a host-protective immune response. We found that BMDCs upregulate a number of critical immune-related genes upon exposure to live E. coli. Most notably, the gene encoding hepcidin, a critical regulator of mammalian iron homeostasis, was significantly upregulated in BMDCs upon exposure to live bacteria.
Dendritic cell-derived hepcidin sequesters iron from the microbiota to promote mucosal healing.
Specimen part
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Inflammation-induced repression of chromatin bound by the transcription factor Foxp3 in regulatory T cells.
Specimen part
View SamplesThe transcription factor Foxp3 is indispensable for the ability of regulatory T (Treg) cells to suppress fatal inflammation. Here, we characterized the role of Foxp3 in chromatin remodeling and regulation of gene expression in actively suppressing Treg cells in an inflammatory setting. Although genome-wide Foxp3 occupancy of DNA regulatory elements was similar in resting and in vivo activated Treg cells, Foxp3-bound enhancers were poised for repression only in activated Treg cells. Following activation, Foxp3-bound sites showed reduced chromatin accessibility and selective H3K27 tri-methylation, which was associated with Ezh2 recruitment and downregulation of nearby gene expression. Thus, Foxp3 poises its targets for repression by facilitating formation of repressive chromatin in regulatory T cells upon their activation in response to inflammatory cues.
Inflammation-induced repression of chromatin bound by the transcription factor Foxp3 in regulatory T cells.
Specimen part
View SamplesRNA-Seq analysis of Treg cell subsets isolated from lungs of Il10GFPFoxp3Thy1.1 mice. Thy1.1+ Treg cells were FACS-sorted into IL-10–IL-18R–, IL-10+IL-18R– and IL10–IL-18R+ populations on day 5 following intranasal infection with 0.5 LD50 PR8-OTI influenza virus. Overall design: mRNA profiles of each Thy1.1+ Treg cell population (IL-10–IL-18R–, IL-10+IL-18R– and IL10–IL-18R+) from lungs on day 5 following influenza infection from 5 infected mice, sorted into TRIzol LS reagent.
A Distinct Function of Regulatory T Cells in Tissue Protection.
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View SamplesLarge-scale cancer genomics projects are profiling hundreds of tumors at multiple molecular layers, including copy number, mRNA and miRNA expression, but the mechanistic relationships between these layers are often excluded from computational models. We developed a supervised learning framework for integrating molecular profiles with regulatory sequence information to reveal regulatory programs in cancer, including miRNA-mediated regulation. We applied our approach to 320 glioblastoma profiles and identified key miRNAs and transcription factors as common or subtype-specific drivers of expression changes. We confirmed that predicted gene expression signatures for proneural subtype regulators were consistent with in vivo expression changes in a PDGF-driven mouse model. We tested two predicted proneural drivers, miR-124 and miR-132, both underexpressed in proneural tumors, by overexpression in neurospheres and observed a partial reversal of corresponding tumor expression changes. Computationally dissecting the role of miRNAs in cancer may ultimately lead to small RNA therapeutics tailored to subtype or individual.
Inferring transcriptional and microRNA-mediated regulatory programs in glioblastoma.
Cell line
View SamplesThe transcription factor Foxp3 is indispensible for the differentiation and function of regulatory T cells (Treg cells). To gain insights into the molecular mechanisms of Foxp3 mediated gene expression we purified Foxp3 complexes and explored their composition. Biochemical and mass-spectrometric analyses revealed that Foxp3 forms multi-protein complexes of 400-800 kDa or larger and identified 361 associated proteins ~30% of which are transcription-related. Foxp3 directly regulates expression of a large proportion of the genes encoding its co-factors. Reciprocally, some transcription factor partners of Foxp3 facilitate its expression. Functional analysis of Foxp3 cooperation with one such partner, Gata3, provided further evidence for a network of transcriptional regulation afforded by Foxp3 and its associates to control distinct aspects of Treg cell biology.
Transcription factor Foxp3 and its protein partners form a complex regulatory network.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Foxp3 exploits a pre-existent enhancer landscape for regulatory T cell lineage specification.
Specimen part
View SamplesRegulatory T (Treg) cells, whose identity and function are defined by the transcription factor Foxp3, are indispensable for immune homeostasis. It is unclear whether Foxp3 exerts its Treg lineage specification function through active modification of the chromatin landscape and establishment of new enhancers or by exploiting a pre-existing enhancer landscape. Analysis of the chromatin accessibility of Foxp3-bound enhancers in Treg and Foxp3-negative T cells showed that Foxp3 was bound overwhelmingly to pre-accessible enhancers occupied by its cofactors in precursor cells or a structurally related predecessor. Furthermore, the bulk of Foxp3-bound Treg cell enhancers inaccessible in Foxp3- CD4+ cells became accessible upon T cell receptor activation prior to Foxp3 expression with only a small subset associated with several functionally important genes being exclusively Treg cell-specific. Thus, in a late cellular differentiation process Foxp3 defines Treg cell functionality in an opportunistic manner by largely exploiting the preformed enhancer network instead of establishing a new enhancer landscape.
Foxp3 exploits a pre-existent enhancer landscape for regulatory T cell lineage specification.
Specimen part
View SamplesIron is an essential component of the erythrocyte protein hemoglobin and is crucial to oxygen transport in vertebrates. In the steady state, erythrocyte production is in equilibrium with erythrocyte removal1. In various pathophysiological conditions, erythrocyte life span is severely compromised, which threatens the organism with anemia and iron toxicity 2,3. Here we identify anon-demand mechanism specific to the liver that clears erythrocytes and recycles iron. We showthat Ly-6Chigh monocytes ingest stressed and senescent erythrocytes, accumulate in the liver, and differentiate to ferroportin 1 (FPN1)-expressing macrophages that can deliver iron to hepatocytes. Monocyte-derived FPN1+ Tim-4neg macrophages are transient, reside alongside embryonically-derived Tim-4high Kuppfer cells, and depend on Csf1 and Nrf2. The spleenlikewise recruits iron-loaded Ly-6Chigh monocytes, but they do not differentiate into ironrecycling macrophages due to the suppressive action of Csf2, and are instead shuttled to the livervia coordinated chemotactic cues. Inhibiting this mechanism by preventing monocyte recruitment to the liver leads to kidney failure and liver damage. These observations identify the liver as the primary organ supporting emergency erythrocyte removal and iron recycling, and uncover a mechanism by which the body adapts to fluctuations in erythrocyte integrity.
On-demand erythrocyte disposal and iron recycling requires transient macrophages in the liver.
Specimen part
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