Two Lysines in the Forkhead Domain of Foxp3 are Key to T Regulatory Cell Function
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ABSTRACT: The forkhead transcription factor, Foxp3, is pivotal to the development and function of CD4+CD25+ T regulatory (Treg) cells that limit autoimmunity and maintain immune homeostasis. Previous data indicated that many of the functions of Foxp3 are controlled by the acetylation of several lysines within the forkhead domain. We now show that mutation of each of two lysines within the forkhead domain of Foxp3, lysine at position 382 (K17) and lysine at position 393 (K18), impaired Treg suppressive function in vivo and in vitro. Lysine mutations also decreased Treg expression of multiple functionally important Foxp3-regulated genes, and inhibited the promoter remodeling of target genes (CTLA-4 and IL-2) without affecting Foxp3 expression level. These data point to the need for a further understanding of the effects of various post-translational modifications on Foxp3 function. Our studies also provide a rationale for developing small molecule inhibitors of such post-translational modifications so as to regulate Foxp3+ Treg function clinically. RNA from three independent samples from magnetically separated CD4+CD25- T-effector cells transduced with EV, WT-Fopx3, Foxp3-K17R or Foxp3-K18R
Project description:The forkhead transcription factor, Foxp3, is pivotal to the development and function of CD4+CD25+ T regulatory (Treg) cells that limit autoimmunity and maintain immune homeostasis. Previous data indicated that many of the functions of Foxp3 are controlled by the acetylation of several lysines within the forkhead domain. We now show that mutation of each of two lysines within the forkhead domain of Foxp3, lysine at position 382 (K17) and lysine at position 393 (K18), impaired Treg suppressive function in vivo and in vitro. Lysine mutations also decreased Treg expression of multiple functionally important Foxp3-regulated genes, and inhibited the promoter remodeling of target genes (CTLA-4 and IL-2) without affecting Foxp3 expression level. These data point to the need for a further understanding of the effects of various post-translational modifications on Foxp3 function. Our studies also provide a rationale for developing small molecule inhibitors of such post-translational modifications so as to regulate Foxp3+ Treg function clinically.
Project description:Regulatory T cells (Treg) contribute to the crucial immunological processes of self-tolerance and immune homeostasis. However, the mechanisms underlying Treg function and cell fate decisions to differentiate between Treg and conventional T cells (Tconv) remain to be fully elucidated, especially at the histone modification level. Covalent modifications of histones establish and maintain chromatin structure, and regulate gene transcription events by facilitating access to cis-elements by trans-acting factors during mammalian development and cellular differentiation. We aimed to investigate the role of the methylation form of histone modification as related to Treg function and phenotype. High-resolution maps of the genome-wide distribution of monomethylated histone H3 lysine 4, H3K4me1, and the trimethylated form H3K4me3 were generated for human activated conventional CD4+CD25+FOXP3- T cells (aTconv) and CD4+CD25+FOXP3+ regulatory T cells (Treg) by sequencing using the Solexa 1G Genetic Analyzer. We found 2115 H3K4me3 regions corresponding to proximal promoter regions; the genes associated with these regions in Treg cells included the crucial transcription factor forkhead box P3 (FOXP3) and the chemokine receptor CCR7. We also identified 41024 Treg cell type-specific H3K4me1 regions. The majority of the H3K4me1 regions differing between the Treg and aTconv cells were located at promoter-distal sites, some of which were selected and consolidated to further examine enhancer activity in in vitro reporter gene assays. The findings from our study provide a comprehensive genome-wide dataset of lineage-specific H3K4me1 and H3K4me3 patterns in Treg and aTconv cells, which may control the differentiation decision, lineage commitment and cell type-specific gene regulation. This basic principle is likely not confined to the two closely-related T cell populations, but may apply generally to somatic cell lineages in adult organisms. Genome-wide distribution of monomethylated histone H3 lysine 4, H3K4me1, and the trimethylated form H3K4me3 in human activated conventional CD4+CD25+FOXP3- T cells (aTconv) and CD4+CD25+FOXP3+ regulatory T cells (Treg) (5 samples in total)
Project description:The forkhead transcription factor Foxp3 is essential for the development of CD4+CD25+ regulatory T (Treg) cells and prevention of autoimmunity, but how it controls the Treg gene expression program is not understood. We describe here genome-wide location and expression data that identify Foxp3 target genes and report that many Foxp3 target genes are key modulators of T cell activation and function. Remarkably, the predominant effect of Foxp3 binding is to suppress the activation of target genes upon T cell stimulation. Foxp3 suppression of its targets appears to be crucial for the normal function of Treg cells because overactive variants of some target genes are known to be associated with autoimmune disease.
Project description:CD4+CD25+FOXP3+ human regulatory T cells (Treg) are essential for self-tolerance and immune homeostasis. Here, we generated genome-wide maps of poised and active enhancer elements marked by histone H3 lysine 4 monomethylation and histone H3 lysine 27 acetylation for CD4+CD25highCD45RA+ naive and CD4+CD25highCD45RA- memory Treg and their CD25- conventional T cell (Tconv) counterparts after in vitro expansion . In addition we generated genome-wide maps of the transcription factors STAT5, FOXP3, RUNX1 and ETS1 in expanded CD4+CD25highCD45RA+ Treg- and CD4+CD25- Tconv to elucidate their role in cell type-specific gene regulation. ChIP-seq of 2 histone marks and transcription factors ETS1, STAT5, FOXP3 and RUNX1 in expanded T cell subpopulations
Project description:Regulatory T (Treg) cells are involved in self tolerance, immune homeostasis, prevention of autoimmunity, and suppression of immunity to pathogens or tumours. The forkhead transcription factor FOXP3 is essential for Treg cell development and function as mutations in FOXP3 cause severe autoimmunity in mice and humans. However, the FOXP3-dependent molecular mechanisms leading to this severe phenotype are not well understood. Here we introduce the chromatin remodelling enzyme SATB1 (special AT-rich sequence-binding protein-1) as an important target gene of FOXP3. So far, SATB1 has been associated with normal thymic T-cell development, peripheral T-cell homeostasis, TH1/TH2 polarization, and reprogramming of gene expression. In natural and induced murine and human FOXP3+ Treg cells SATB1 expression is significantly reduced. While there is no differential epigenetic regulation of the SATB1 locus between Treg and Teffector cells, FOXP3 reduces SATB1 expression directly as a transcriptional repressor at the SATB1 locus and indirectly via miR-155 induction, which specifically binds to the 3’UTR of the SATB1 mRNA. Reduced SATB1 expression in FOXP3+ cells achieved either by overexpression or induction of FOXP3 is linked to significant reduction in TH1 and TH2 cytokines, while loss of FOXP3 function either by knock down or genetic mutation leads to significant upregulation of SATB1 and subsequent cytokine production. Alltogether, these findings demonstrate that reduced SATB1 expression in Treg cells is necessary for maintenance of a Treg-cell phenotype in vitro and in vivo and places SATB1-mediated T cell-specific modulation of global chromatin remodelling central during the decision process between effector and regulatory T-cell function. Gene expression profiling of freshly isolated CD4+ T cells, separated into CD25 negative and positive subpopulations, from three different donors. FOXP3 is stably and constitutively expressed at a high level in CD4+CD25+ regulatory T cells and at a low level in CD4+CD25- cells.
Project description:Regulatory T (Treg) cells, whose differentiation and function are controlled by transcription factor Foxp3, express high amounts of a closely related family member Foxp1, which is also expressed in quiescent naive T cells. Here we explored Foxp1 function in Treg cells. We found that a large number of Foxp3-bound genomic sites in Treg cells were occupied by Foxp1 in both Treg and conventional T cells. In Treg cells, Foxp1 markedly increased Foxp3 binding to these sites, which were enriched for canonic forkhead and Ets binding motifs. Foxp1 deficiency in Treg cells resulted in their impaired function and competitive fitness associated with markedly reduced CD25 expression and interleukin-2 (IL-2) responsiveness, diminished CTLA-4 and increased SATB1 expression. The characteristic patterns of CD25, Foxp3, and CTLA-4 expression in Treg cells were rescued, at least in part, upon strong IL-2 signaling. Our studies suggest that in addition to the Foxp1-mediated regulation of quiescence that is common to Treg and conventional T cells, Foxp1 has an essential non-redundant function in Treg cells by enforcing Foxp3-mediated regulation of gene expression and enabling efficient IL-2 signaling in these cells.
Project description:Foxp3, a transcription factor of the forkhead/winged helix family, plays a unique role in the transcriptional control of regulatory CD4+CD25+ T (Treg) cells. The identification of potential target genes associated with the regulatory phenotype and the characterization of combinatorial interactions of transcription factors (TF) in promoter regions in genes regulated by Foxp3 has become important to understand the transcriptional control of Treg cells.
Project description:Regulatory T cells (Treg cells) expressing the forkhead family transcription factor Foxp3 are critical mediators of dominant immune tolerance to self. Most Treg cells constitutively express the high-affinity interleukin 2 (IL-2) receptor alpha-chain (CD25); however, the precise function of IL-2 in Treg cell biology has remained controversial. To directly assess the effect of IL-2 signaling on Treg cell development and function, we analyzed mice containing the Foxp3gfp knock-in allele that were genetically deficient in either IL-2 (Il2-/-) or CD25 (Il2ra-/-). We found that IL-2 signaling was dispensable for the induction of Foxp3 expression in thymocytes from these mice, which indicated that IL-2 signaling does not have a nonredundant function in the development of Treg cells. Unexpectedly, Il2-/- and Il2ra-/- Treg cells were fully able to suppress T cell proliferation in vitro. In contrast, Foxp3 was not expressed in thymocytes or peripheral T cells from Il2rg-/- mice. Gene expression analysis showed that IL-2 signaling was required for maintenance of the expression of genes involved in the regulation of cell growth and metabolism. Thus, IL-2 signaling seems to be critically required for maintaining the homeostasis and competitive fitness of Treg cells in vivo. Experiment Overall Design: We isolated Foxp3+ CD4+ T cells from Il2-/- mice treated with PBS or recombinant IL-2 for gene expression analysis using whole-genome oligonucleotide microarrays. To identify gene expression changes resulting from IL-2 deficiency and subsequent IL-2 stimulation in Treg cells, we directly compared expression profiles with each other and with expression profiles of Foxp3+ CD4+ T cells isolated from wild-type mice.
Project description:CD4+CD25+FOXP3+ human regulatory T cells (Treg) are essential for self-tolerance and immune homeostasis. Here, we generated genome-wide maps of poised and active enhancer elements marked by histone H3 lysine 4 monomethylation and histone H3 lysine 27 acetylation for CD4+CD25highCD45RA+ naive and CD4+CD25highCD45RA- memory Treg and their CD25- conventional T cell (Tconv) counterparts after in vitro expansion . In addition we generated genome-wide maps of the transcription factors STAT5, FOXP3, RUNX1 and ETS1 in expanded CD4+CD25highCD45RA+ Treg- and CD4+CD25- Tconv to elucidate their role in cell type-specific gene regulation.
Project description:The forkhead DNA-binding protein FOXP3 is critical for the development and suppressive function of CD4+CD25+ regulatory T cells (TREG), which play a key role in maintaining self tolerance. Functionally, FOXP3 is capable of repressing transcription of cytokine genes regulated by the Nuclear Factor of Activated T cells (NFAT). Various mechanisms have been proposed by which FOXP3 mediates these effects. Using novel HEK cell lines that inducibly express either wild-type (WT) or mutant FOXP3, we have identified genome-wide expression patterns showing among other features that NFAT2 as an early target of FOXP3-mediated transcriptional repression. Six biological replicates of wild-type induced FOXP3 cell lines and six biological replicates of mutated FOXP3 cell line were studied.