Project description:Differing from the mouse Foxp3 gene that encodes only one protein product, human FOXP3 encodes two major isoforms through alternative splicing – a longer isoform (FOXP3 FL) containing all the coding exons and the other shorter isoform lacking the amino acids encoded by exon 2 (FOXP3 ΔE2). The two isoforms are naturally expressed in humans yet their differences in controlling regulatory T cell phenotype and functionality remains unclear. Here we show that patients expressing only the shorter isoform failed to maintain self-tolerance and developed IPEX syndrome. Mice with Foxp3 exon 2 deletion developed excessive TFH and GC B cell responses and systemic autoimmune disease with anti-dsDNA and anti-nuclear autoantibody production and immune-complex glomerulonephritis. Regulatory T cells expressing FOXP3 ΔE2 were unstable and sufficient to induce autoimmunity when transferred into Tcrb-deficient mice. Mechanistically, FOXP3 ΔE2 isoform allows increased expression of selected cytokines but decreased expression of a set of Foxp3 positive regulators without altered binding to these gene loci. We demonstrate that exon 2 of FOXP3 is required to maintain Treg stability and immune homeostasis.
Project description:Differing from the mouse Foxp3 gene that encodes only one protein product, human FOXP3 encodes two major isoforms through alternative splicing – a longer isoform (FOXP3 FL) containing all the coding exons and the other shorter isoform lacking the amino acids encoded by exon 2 (FOXP3 ΔE2). The two isoforms are naturally expressed in humans yet their differences in controlling regulatory T cell phenotype and functionality remains unclear. Here we show that patients expressing only the shorter isoform failed to maintain self-tolerance and developed IPEX syndrome. Mice with Foxp3 exon 2 deletion developed excessive TFH and GC B cell responses and systemic autoimmune disease with anti-dsDNA and anti-nuclear autoantibody production and immune-complex glomerulonephritis. Regulatory T cells expressing FOXP3 ΔE2 were unstable and sufficient to induce autoimmunity when transferred into Tcrb-deficient mice. Mechanistically, FOXP3 ΔE2 isoform allows increased expression of selected cytokines but decreased expression of a set of Foxp3 positive regulators without altered binding to these gene loci. We demonstrate that exon 2 of FOXP3 is required to maintain Treg stability and immune homeostasis.
Project description:Regulatory T cells (Treg) have been shown to adopt a catabolic metabolic programme with increased capacity for fatty acid oxidation fuelled oxidative phosphorylation (OXPHOS). The role of Foxp3 in this metabolic shift is poorly understood. Here we show that Foxp3 was sufficient to induce a significant increase in the spare respiratory capacity of the cell, the extra OXPHOS capacity available to a cell to meet increased demands on energy in response to work. Foxp3-expressing cells were enhanced in their ability to utilise palmitate for respiration and, in addition, the activity of electron transport complexes I, II and IV were enhanced following Foxp3 expression. Foxp3 also imparts a selective advantage in ATP generation capacity, one that might be exploited as a source of adenosine for functional immunomodulation. In order to explore possible mechanisms for these differences in metabolism we conducted a quantitative proteomics study to compare the contribution of TGFβ and the transcription factor Foxp3 to the Treg proteome. We used quantitative mass spectrometry to examine differences between proteomes of nuclear and cytoplasmic Foxp3-containing CD4+ T cells from various sources with Foxp3- activated CD4 T cells, as well as Treg from human peripheral blood. Gene set enrichment analysis of our proteomic datasets demonstrated that Foxp3 expression is associated with a significant up regulation of several members of the mitochondrial electron transport chain. Not only does Foxp3 influence genes directly concerned with immune function, but also with the energy generating functions of Treg.
Project description:The transcription factor FoxP3 partakes dominantly in the specification and function of FoxP3+ CD4+ T regulatory cells (Tregs), but is neither strictly necessary nor sufficient to determine the characteristic Treg transcriptional signature. Computational network inference and experimental testing assessed the contribution of several other transcription factors (TFs). Enforced expression of Helios or Xbp1 elicited specific signatures, but Eos, Irf4, Satb1, Lef1 and Gata1 elicited exactly the same outcome, synergizing with FoxP3 to activate most of the Treg signature, including key TFs, and enhancing FoxP3 occupancy at its genomic targets. Conversely, the Treg signature was robust to inactivation of any single cofactor. A redundant genetic switch thus locks-in the Treg phenotype, a model which accounts for several aspects of Treg physiology, differentiation and stability. To study the impact of deficiency of candidate FoxP3 cofactors (Xbp1, Eos, Gata1) on the expression of the Treg transcriptional signature, gene expression profiles were generated from purified splenic CD4+CD25hi Tregs of these mutant or knockout mice and their wildtype littermates.
Project description:CD4+ regulatory T cells (Tregs) are key mediators of immunological tolerance and promising effector cells for immuno-suppressive adoptive cellular therapy to fight autoimmunity and chronic inflammation. Their functional stability is critical for their clinical utility and has been correlated to the demethylated state of the TSDR/CNS2 enhancer element in the Treg lineage transcription factor FOXP3. However, proof for a causal contribution of the TSDR de-methylation to FOXP3 stability and Treg induction is so far lacking. We here established a powerful transient-transfection CRISPR-Cas9-based epigenetic-editing method for the selective de-methylation of the TSDR within the endogenous chromatin environment of a living cell. The induced de-methylated state was stable over weeks in clonal T cell proliferation cultures even after expression of the editing complex had ceased. Epigenetic editing of the TSDR resulted in FOXP3 expression, even in its physiological isoform distribution, proving a causal role for the de-methylated TSDR in FOXP3 regulation. However, successful FOXP3 induction was not associated with a switch towards a functional Treg phenotype, in contrast to what has been reported from FOXP3 overexpression approaches. Thus, TSDR de-methylation is required, but not sufficient for a stable Treg phenotype induction. Therefore, targeted demethylation of the TSDR may be a critical addition to published in vitro Treg induction protocols which so far lack FOXP3 stability.
Project description:Regulatory T (Treg) cells are characterized by the forkhead transcription factor FOXP3. Mutations in FOXP3 cause autoimmunity in mice and humans. Here, Treg cells as well as conventional T cells were isolated from B-CLL patients and analyzed by global gene expression analysis in order to identify biological differences in Treg cells of CLL patients.
Project description:Natural CD4+FOXP3+ regulatory T (Treg) cells constitute a unique T-cell lineage that plays a pivotal role in maintaining immune homeostasis and immune tolerance. Recent studies provide evidence for the heterogeneity and plasticity of the Treg cell lineage. However, the fate of human Treg cells after loss of FOXP3 expression and the underlying epigenetic mechanisms remain to be fully elucidated. Here, we compared gene expression profiles and histone methylation status on two histone H3 lysine residues (H3K4me3 and H3K27me3) of expanded FOXP3+ and corresponding FOXP3-losing Treg cells. DGE assay showed that human Treg cells down-regulated Treg signature genes, whereas up-regulated a set of Th lineages-associated genes, especially for Th2, such as GATA3, GFI1 and IL13, after in vitro expansion. Furthermore, we found that reprogramming of Treg cells was associated with histone modifications, as shown by decreased abundance of permissive H3K4me3 within down-regulated Treg signature genes, such as FOXP3, CTLA4 and LRRC32 loci, although with no significant changes in H3K27me3 modification. Thus, our results indicate that human Treg cells could convert into a Th-like cells upon in vitro expansion, displaying a gene expression signature dominated by Th2 lineage associated genes, and the histone methylation might contribute to such conversion. mRNA profiles of in-vitro-expanded FOXP3+ Treg and FOXP3-losing Treg cells generated by deep sequencing.