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Project description:CD4 and CD8 T cells are vital components of the immune system. We found that histone deacetylase 3 (HDAC3) is critical for the development of CD4 T cells, as HDAC3-deficient DP thymocytes generate only CD8SP thymocytes in mice. In the absence of HDAC3, MHC Class II-restricted OT-II thymocytes are redirected to the CD8 cytotoxic lineage, which occurs with accelerated kinetics. Analysis of histone acetylation and RNA-seq reveals that HDAC3-deficient DP thymocytes are biased towards the CD8 lineage prior to positive selection. Commitment to the CD4 or CD8 lineage is determined by whether persistent TCR signaling or cytokine signaling predominates, respectively. Despite elevated IL-21R/γc/STAT5 signaling in HDAC3-deficient DP thymocytes, blocking IL-21R does not restore CD4 lineage commitment. Instead, HDAC3 binds directly to CD8-lineage promoting genes. Thus, HDAC3 is required to restrain CD8-lineage genes in DP thymocytes for the generation of CD4 T cells.
| S-EPMC6338460 | biostudies-literature
Project description:HDAC3 restrains CD8-lineage genes to maintain a bi-potential state in CD4+CD8+ thymocytes for CD4-lineage commitment
| PRJNA431302 | ENA
Project description:Type I invariant NKT cells (iNKT cells) are a subset of alphabeta T cells characterized by the expression of an invariant alpha-chain variable region 14-alpha-chain joining region 18 (V(alpha)14J(alpha)18) T cell antigen receptor (TCR) alpha-chain. The iNKT cells derive from CD4(+)CD8(+) double-positive (DP) thymocytes, and their generation requires a long half-life of DP thymocytes to allow V(alpha)14-J(alpha)18 rearrangements, expression of glycolipid-loaded CD1d on DP thymocytes, and signaling through the signaling-activation molecule SLAM-adaptor SAP pathway. Here we show that the transcription factor c-Myb has a central role in priming DP thymocytes to enter the iNKT lineage by simultaneously regulating CD1d expression, the half-life of DP cells and expression of SLAMF1, SLAMF6 and SAP.
| S-EPMC2857587 | biostudies-literature
Project description:Genetic variation in the major histocompatibility complex (MHC) affects CD4∶CD8 lineage commitment and MHC expression. However, the contribution of specific genes in this gene-dense region has not yet been resolved. Nor has it been established whether the same genes regulate MHC expression and T cell selection. Here, we assessed the impact of natural genetic variation on MHC expression and CD4∶CD8 lineage commitment using two genetic models in the rat. First, we mapped Quantitative Trait Loci (QTLs) associated with variation in MHC class I and II protein expression and the CD4∶CD8 T cell ratio in outbred Heterogeneous Stock rats. We identified 10 QTLs across the genome and found that QTLs for the individual traits colocalized within a region spanning the MHC. To identify the genes underlying these overlapping QTLs, we generated a large panel of MHC-recombinant congenic strains, and refined the QTLs to two adjacent intervals of ∼0.25 Mb in the MHC-I and II regions, respectively. An interaction between these intervals affected MHC class I expression as well as negative selection and lineage commitment of CD8 single-positive (SP) thymocytes. We mapped this effect to the transporter associated with antigen processing 2 (Tap2) in the MHC-II region and the classical MHC class I gene(s) (RT1-A) in the MHC-I region. This interaction was revealed by a recombination between RT1-A and Tap2, which occurred in 0.2% of the rats. Variants of Tap2 have previously been shown to influence the antigenicity of MHC class I molecules by altering the MHC class I ligandome. Our results show that a restricted peptide repertoire on MHC class I molecules leads to reduced negative selection of CD8SP cells. To our knowledge, this is the first study showing how a recombination between natural alleles of genes in the MHC influences lineage commitment of T cells.
| S-EPMC3930506 | biostudies-literature
Project description:The CD4(+)CD8(+) (double positive, DP) stage of thymic development is thought to be the earliest period that generates natural Foxp3(+) regulatory T (Treg) cells important for the prevention of autoimmunity. However, we found that most Foxp3(+) DP cells identified by routine flow cytometry represent doublets comprised of Foxp3(-) DP and Foxp3(+) CD4(+)CD8(-) (CD4SP) cells. This was determined using analysis of flow cytometric height and width parameters, postsort contaminants, and thymocyte mixing studies. Temporal analysis of Treg cell development arising from bone marrow precursors in neonatal bone marrow chimeras suggested that Foxp3(+) DP cells are not a major percentage of Foxp3(+) thymocytes, and it supported the notion that most Treg cell development occurred at the immature HSA(high) CD4SP stage. Thus, these data demonstrate that the frequency of Foxp3(+) cells generated at the DP stage is much smaller than previously recognized, suggesting that additional thymocyte maturation may be required to facilitate efficient induction of Foxp3.
| S-EPMC2912293 | biostudies-literature
Project description:Poly-(ADP-ribose) polymerase-2 (PARP-2) belongs to a large family of enzymes that synthesize and transfer ADP-ribose polymers to acceptor proteins, modifying their functional properties. PARP-2-deficient (Parp-2-/-) cells, similar to Parp-1-/- cells, are sensitive to both ionizing radiation and alkylating agents. Here we show that inactivation of mouse Parp-2, but not Parp-1, produced a two-fold reduction in CD4+CD8+ double-positive (DP) thymocytes associated with decreased DP cell survival. Microarray analyses revealed increased expression of the proapoptotic Bcl-2 family member Noxa in Parp-2-/- DP thymocytes compared to littermate controls. In addition, DP thymocytes from Parp-2-/- have a reduced expression of T-cell receptor (TCR)alpha and a skewed repertoire of TCRalpha toward the 5' Jalpha segments. Our results show that in the absence of PARP-2, the survival of DP thymocytes undergoing TCRalpha recombination is compromised despite normal amounts of Bcl-xL. These data suggest a novel role for PARP-2 as an important mediator of T-cell survival during thymopoiesis by preventing the activation of DNA damage-dependent apoptotic response during the multiple rounds of TCRalpha rearrangements preceding a positively selected TCR.
| S-EPMC1570435 | biostudies-literature
Project description:Physiological stress resulting from infections, trauma, surgery, alcoholism, malnutrition, and/or pregnancy results in a substantial depletion of immature CD4(+)CD8(+) thymocytes. We previously identified 18 distinct stress-responsive microRNAs (miRs) in the thymus upon systemic stress induced by lipopolysaccharide (LPS) or the synthetic glucocorticoid, dexamethasone (Dex). MiRs are short, non-coding RNAs that play critical roles in the immune system by targeting diverse mRNAs, suggesting that their modulation in the thymus in response to stress could impact thymopoiesis. MiR-181d is one such stress-responsive miR, exhibiting a 15-fold down-regulation in expression. We utilized both transgenic and gene-targeting approaches to study the impact of miR-181d on thymopoiesis under normal and stress conditions. The over-expression of miR-181d in developing thymocytes reduced the total number of immature CD4(+)CD8(+) thymocytes. LPS or Dex injections caused a 4-fold greater loss of these cells when compared with the wild type controls. A knockout mouse was developed to selectively eliminate miR-181d, leaving the closely spaced and contiguous family member miR-181c intact. The targeted elimination of just miR-181d resulted in a thymus stress-responsiveness similar to wild-type mice. These experiments suggest that one or more of three other miR-181 family members have overlapping or compensatory functions. Gene expression comparisons of thymocytes from the wild type versus transgenic mice indicated that miR-181d targets a number of stress, metabolic, and signaling pathways. These findings demonstrate that selected miRs enhance stress-mediated thymic involution in vivo.
| S-EPMC3887031 | biostudies-literature
Project description:Memory T cells can be divided into central memory T cell (T(CM) cell) and effector memory T cell (T(EM) cell) subsets based on homing characteristics and effector functions. Whether T(EM) and T(CM) cells represent interconnected or distinct lineages is unclear, although the present paradigm suggests that T(EM) and T(CM) cells follow a linear differentiation pathway from naive T cells to effector T cells to T(EM) cells to T(CM) cells. We show here that naive T cell precursor frequency profoundly influenced the pathway along which CD8+ memory T cells developed. At low precursor frequency, those T(EM) cells generated represented a stable cell lineage that failed to further differentiate into T(CM) cells. These findings do not adhere to the present dogma regarding memory T cell generation and provide a means for identifying factors controlling memory T cell lineage commitment.
| S-EPMC2849311 | biostudies-literature
Project description:The CD4 versus CD8 lineage specification of thymocytes is linked to coreceptor expression. The transcription factor MAZR has been identified as an important regulator of Cd8 expression. Here we show that variegated CD8 expression by loss of Cd8 enhancers was reverted in MAZR-deficient mice, which confirms that MAZR negatively regulates the Cd8 loci during the transition to the double-positive (DP) stage. Moreover, loss of MAZR led to partial redirection of major histocompatibility complex (MHC) class I-restricted thymocytes into CD4(+) helper-like T cells, which correlated with derepression of Th-POK, a central transcription factor for helper-lineage development. MAZR bound the silencer of the gene encoding Th-POK, which indicated direct regulation of this locus by MAZR. Thus, MAZR is part of the transcription factor network that regulates the CD8 lineage differentiation of DP thymocytes.
| S-EPMC3365445 | biostudies-literature
Project description:Expression of Rag1 and Rag2 is tightly regulated in developing T cells to mediate TCR gene assembly. Here we have investigated the molecular mechanisms governing the assembly and disassembly of a transcriptionally active RAG locus chromatin hub in CD4+CD8+ thymocytes. Rag1 and Rag2 gene expression in CD4+CD8+ thymocytes depends on Rag1 and Rag2 promoter activation by a distant antisilencer element (ASE). We identify GATA3 and E2A as critical regulators of the ASE, and Runx1 and E2A as critical regulators of the Rag1 promoter. We reveal hierarchical assembly of a transcriptionally active chromatin hub containing the ASE and RAG promoters, with Rag2 recruitment and expression dependent on assembly of a functional ASE-Rag1 framework. Finally, we show that signal-dependent down-regulation of RAG gene expression in CD4+CD8+ thymocytes depends on Ikaros and occurs with disassembly of the RAG locus chromatin hub. Our results provide important new insights into the molecular mechanisms that orchestrate RAG gene expression in developing T cells.
| S-EPMC6314527 | biostudies-literature