Project description:Sustained Ca2+ entry into CD4+CD8+ double-positive thymocytes is required for positive selection. We identified a voltage-gated Na+ channel (VGSC), essential for positive selection of CD4+ T cells. Pharmacological inhibition of VGSC activity inhibited sustained Ca2+ influx induced by positive-selecting ligands and in vitro positive selection of CD4+ but not CD8+ T cells. In vivo shRNA knockdown of Scn5a specifically inhibited positive selection of CD4+ T cells. Ectopic expression of VGSC in peripheral AND CD4+ T cells bestowed the ability to respond to a positively selecting ligand, directly demonstrating VGSC expression was responsible for increased sensitivity. Thus active VGSCs in thymocytes provides a mechanism by which a weak positive selecting signal can induce sustained Ca2+ signals required for CD4+ T cell development. Pre-selected AND DP thymocytes were stimulated with plate bound peptide-loaded I-Ek Ig dimers. Genes were differentially regulated by positive and negative selection signals. The goal of this study is to identify ion-channel related genes critical for thymic positive selection, given the sustained Ca2+ entry into double positive thymocytes is required for positive selection. Total RNA of pre-selected AND thymocytes stimulated with I-Ek Ig dimers loaded with the positively-selecting peptide gp250, the negatively-selecting agonist peptide MCC, or the non-selecting control peptide Hb were used for the transcriptional profiling analysis. We found 28 genes were differentially down-regulated by MCC stimulation but upregulated by gp250 stimulation. One of them, scn4b, was ion-channel related.
Project description:Abstract of publicaton: CD4/CD8 double-positive (DP) thymocytes express the transcriptional repressor Histone Deacetylase 7 (HDAC7), a class IIa HDAC that is exported from the cell nucleus after T cell receptor (TCR) engagement. Through signal-dependent nuclear export, class IIa HDACs such as HDAC7 mediate signal-dependent changes in gene expression that are important to developmental fate decisions in multiple tissues. We report that HDAC7 is exported from the cell nucleus during positive selection in thymocytes, and regulates genes mediating the coupling between TCR engagement and downstream events that determine cell survival. Thymocytes lacking HDAC7 are inefficiently positively selected due to a severely shortened lifespan and exhibit a truncated repertoire of TCR Jalpha segments. The expression of multiple important mediators and modulators of the response to TCR engagement is altered in HDAC7-deficient thymocytes, resulting in increased tonic MAP kinase activity that contributes to the observed loss of viability. Remarkably, the activity of Protein Kinase D, the kinase that mediates nuclear export of HDAC7 in response to TCR signaling, is also increased in HDAC7-deficient thymocytes, suggesting that HDAC7 nuclear export governs a self-sustaining auto-excitatory loop. These experiments add to the understanding of the life/death decision in thymic T cell development, define a novel function for class IIa HDACs, and point to a novel feed-forward mechanism whereby these molecules regulate their own state and mediate stable developmental transitions. Title of manuscript: Nuclear Export of Histone Deacetylase 7 During Thymic Selection Mediates Immune Self-tolerance. abstract of manuscript: Histone Deacetylase 7 (HDAC7) is a TCR signal-dependent regulator of differentiation that is highly expressed in CD4/CD8 double-positive (DP) thymocytes. Here we examine the effect of blocking TCR-dependent nuclear export of HDAC7 during thymic selection, through expression of a signal-resistant mutant of HDAC7 (HDAC7-?P) in thymocytes. We find that HDAC7-?P Transgenic thymocytes exhibit a profound block in negative thymic selection, but can still undergo positive selection, resulting in the escape of autoreactive T cells into the periphery. Gene expression profiling reveals a comprehensive suppression of the negative selection-associated gene expression program in DP thymocytes, associated with a defect in the activation of MAP kinase pathways by TCR signals. The consequence of this block in vivo is a lethal autoimmune syndrome involving the exocrine pancreas and other abdominal organs. These experiments establish a novel molecular model of autoimmunity and cast new light on the relationship between thymic selection and immune self-tolerance. Goal of Microarray experiment: We did these experiments to determine how alteration of the function of HDAC7, a site-specific and signal-dependent repressor of transcription, changes gene expression in CD4/CD8 DP thymocytes.
Project description:The aim of this study was to quantify the impact of NOD genetic vatiation on thymic negative selection transcriptional programs. Pre-selected BDC2.5 TCR Tg DP thymocytes from non-selecting B6 and NOD.H2b backgrounds were purified (Dynal CD8 FlowComp), mixed in a 1:1 ratio and stimulated with BDC mimotope-loaded TCRa-/-/NOD splenocytes for indicated periods of time and double sorted by FACS as Thy1.2+Dump-CD4+CD8+; Dump includes CD19, Gr1, CD11b, CD11c, CD49b. Following cell sorting into trizol, RNA was purified, labeled and hybridized to Affymetrix arrays. experiment type: unstimulated versus stimulated BDC/B6.Rag-/- and BDC/NOD.H2b.Rag-/- DP thymocytes
Project description:CD4 CD8 double positive (DP) thymocytes progressively shut down Notch signaling after β-selection allowing progression of the DP program and positive selection of conventional CD4 and CD8 single positive T cells. In contrast, innate CD8+ T cells are selected from DP precursors shortly after β-selection. Here, we investigated whether notch signaling is required for the initiation of the innate T cell developmental program upon TCR engagement. We show that, after β-selection, Notch activation limits progression to late DP cells and favors the development of TCRαβ/CD3 expressing CD8dim early DP progenitors. TCR engagement in these Notch dependent TCRαβ+ early DP precursors does not induce prominent apoptosis, but rather induces T-bet expression by an mTOR-dependent mechanism. Our findings indicate that Notch signaling drives the launch of an innate effector program in response to TCR agonist selection in the thymus.
Project description:Double-positive (DP) thymocytes respond to intrathymic TCR signals by undergoing positive selection and lineage differentiation into single-positive (SP) mature cells. Concomitant with these wellcharacterized events is the acquisition of a mature T cell gene expression program characterized by the induction of effector molecules IL-7Ra, S1P1 and CCR7, but the underlying mechanism remains elusive. We report here that transcription repressor Gfi1 orchestrates the fidelity of DP gene expression program and developmental maturation into SP cells. Loss of Gfi1 resulted in premature induction of effector genes and transcription factors Foxo1 and Klf2 in DP thymocytes, and accumulation of post-selection intermediate populations and accelerated transition into SP cells. Strikingly, partial loss of Foxo1 function, but not restored survival fitness, rectified the dysregulated gene expression and thymocyte maturation in Gfi1-deficient mice. Our results establish Gfi1-Foxo1 axis and the transcriptional circuitry that actively maintain DP identity and shape the proper generation of mature T cells
Project description:Positive selection occurs in the thymic cortex, but critical maturation events occur later in the medulla. We defined the precise stage at which T cells acquire competence to proliferate and emigrate. Transcriptome analysis of late gene changes suggested roles for NF-κB and interferon signaling. Mice lacking the IKK kinase TAK1, showed normal positive selection, but a specific block in functional maturation. NF-κB signaling provided protection from TNF, and was required for proliferation and emigration. Alternatively, the interferon signature was independent of NF-κB, and IFNαR deficient thymocytes showed reduced STAT1 levels and phenotypic abnormality, but were competent to proliferate. Thus, both NF-κB and tonic IFN signals are involved in the final maturation of thymocytes into naïve T cells. Gene expression profile was performed on cells isolated from mouse thymus, including Pre-DP, Post-DP, SM&M1, M2 and Tak1-deficient SM&M1 cells.
Project description:Type 1 NKT cells play a critical role in controlling the strength and character of adaptive and innate immune responses. Their functional characteristics are distinct from conventional T cells, and are induced by a transcriptional program initiated by positive selection on CD4+CD8+ (double positive, DP) thymocytes. Here we examined transcriptional events in four immature thymic NKT cell subsets in a novel Vα14 TCR transgenic strain bearing greatly expanded numbers of CD24+CD44- NKT cells. We used a transcriptional regulatory network approach to map TCR validation to the transition from DP T to DP NKT cells, and positive selection and lineage commitment to the transition from DP NKT to CD4 NKT
Project description:Mouse thymocytes can be classified into four major subsets based on expression of CD4 and CD8 co-receptors. CD4-CD8- (double negative, DN) cells become CD4+CD8+ (double positive, DP) cells following productive T cell receptor (TCR) beta chain rearrangement. A small proportion of DP cells are selected through interaction of clonal TCRalpha/beta and MHC self peptide complex expressed on thymic stromal cells. DP cell expressing MHC class I-restricted TCR become CD4-CD8+ cells, which will finally differentiate into cytotoxic T cells, while MHC class II restricted selection generates CD4+CD8- helper lineage T cells. We used microarrays to identify genes important for thymocyte differentiation and lineage determination by profiling gene expression in different thymocyte subsets.
Project description:Review on the role of Bcl11b in thymus and periphery and impact on diseases RNA was extracted from DP thymocytes of bcl11bf/fCd4cre/tcra-/- and tcra-/- mice. Tcra-/- mice only have preselected DP thymocytes. Such mice were used to determine the role of Bcl11b before selection, considering the defective positive selection in bcl11bf/fcd4cre mice. RNA was isolated and submitted for library generation and microarray analysis to determine expression profile of bcl11b-/- preselected DP thymocytes.