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Thymic deletion in B10 430B

ABSTRACT: Microarray analysis of thymic deletion in the B10 mouse strain The gene expression patterns of thymocytes at the pre-selection stage and undergoing positive selection or negative selection were compared in the C57BL/10-H2k (B10k) strain. In order to sort thymocytes homogenously undergoing positive selection the 3A9 TCRHEL transgenic was used, which directs thymocyte development towards a MHC class II-restricted HEL-reactive lineage. To sort thymocytes homogenously undergoing negative selection, the 3A9 TCRHEL transgenic was crossed to the insHEL transgenic, which expresses HEL under the control of the insulin promoter in the thymic stroma, leading to efficient negative selection at the early single positive (CD4+CD8low) stage. To prepare the samples, thymic cell suspensions from female 6-8 week old B10k mice, either 3A9 TCRHEL or 3A9 TCRHEL x insHEL transgenics, were stained with CD4-FITC, CD69-PE, CD8-PerCP, and 1G12 supernatant (which recognises the 3A9 TCRHEL complex) followed by anti-IgG1-APC, and sorted. Pre-selection cells (from both transgenics) were defined as CD4+CD8+CD69-1G12low. Cells undergoing positive selection (from 3A9 TCRHEL transgenics) or negative selection (from 3A9 TCRHEL x insHEL transgenics) were defined as CD4+CD8lowCD69+1G12high. Keywords: repeat

ORGANISM(S): Mus musculus

PROVIDER: GSE9700 | GEO | 2008/11/01

SECONDARY ACCESSION(S): PRJNA103603

REPOSITORIES: GEO

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Project description:Background. T cells in the thymus undergo opposing positive and negative selection processes so that the only T cells entering circulation are those bearing a T cell receptor (TCR) with a low affinity for self. The mechanism differentiating negative from positive selection is poorly understood, despite the fact that inherited defects in negative selection underlie organ-specific autoimmune disease in AIRE-deficient people and the non obese diabetic (NOD) mouse strain. Results. Here we use homogeneous populations of T cells undergoing either positive or negative selection in vivo together with genome-wide transcription profiling on microarrays to identify the gene expression differences underlying negative selection to an Aire-dependent organ-specific antigen, including the upregulation of a genomic cluster in the cytogenetic band 2F. Analysis of defective negative selection in the autoimmune-prone NOD strain demonstrates a global impairment in the induction of the negative selection response gene set, but little difference in positive selection response genes. Combining expression differences with genetic linkage data we identify differentially expressed candidate genes including Bim, Bnip3, Smox, Pdrg1, Id1, Pdcd1, Ly6c, Pdia3, Trim30 and Trim12. Conclusions. The data provide a molecular map of the negative selection response in vivo, and by analysis of deviations from this pathway in the autoimmune susceptible NOD strain, suggest that susceptibility arises from small expression differences in genes acting at multiple points in the pathway between the TCR and cell death. Experiment Overall Design: Analysis of two thymic populations - early single positive thymocytes (CD4+CD8lowCD69+TCRhi) and early double positive thymocytes (CD4+CD8+CD69-TCRlow). Samples purified from the 3A9 TCR transgenic (TCR) to characterise positive selection and the 3A9 TCR x insHEL double transgenic (Dbl) to characterise negative selection towards an Aire-dependent organ-specific antigen. Both the non autoimmune C57BL10.H2k (B10) and autoimmune Non obese diabetic (NOD) strains were analysed in this method. Three biological replicates were used for each of these eight different groups.

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.

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Thymic deletion in B10 430B

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