Project description:Promiscuous gene expression (pGE) of numerous self-antigens in thymic epithelial cells (TEC) enables the elimination of self-reactive T cells. The autoimmune regulator (Aire) is the only known molecular determinant driving pGE in the thymus but the existence of Aire-independent mechanisms has been inferred. Here, we analyzed the poly(A)+ transcriptome of TEC populations by RNA-sequencing (RNA-seq) in order to reveal differential features of Aire-induced vs. –independent pGE. We report an unanticipated effect of Aire deletion on the proliferation and differentiation of cortical TEC. Moreover, the RNA-seq data reveal the breath of Aire-induced and –independent pGE in medullary TEC (mTEC) subsets and the extent of thymic peripheral tissue representation. The results suggest that Aire-induced promiscuously expressed transcripts affect several functions with far reaching biological consequences in mTEC. High-throughput characterization of TEC transcriptomes will enable progress in understanding TEC biology and the establishment of self-tolerance. The mRNA profiles of cTEC, mTEClo and mTEChi from 6-8 week-old wild type (WT) and Aire-/- (KO) mice were generated by RNA-sequencing using Illumina HiSeq2000.
Project description:We show that thymic epithelial cells in the medulla (mTECs) that present self-antigens (self-Ags) to developing thymocytes for establishing immunological self-tolerance also express CTLA-4 if Aire, loss of which is responsible for the hereditary autoimmunity, is nonfunctional. Upon binding with its ligand, CD80 and CD86, expressed on thymic DCs, CTLA-4/ligand complex was internalized by Aire-deficient mTECs. This attenuated the ability of DCs to provide costimulatory signals and to present self-Ags, resulting in the reduced production of Tregs.
Project description:The aim of this study is to analyze the transcriptional effects of Aire deficiency in the thymus, using the Affymetrix MoGene platform to analyze variation in exon usage MECs were isolated from 4-6 wk-old WT or Aire KO ((B6xNOD)F1 background) mice. Three WT and three Aire-KO mice taken individually were used.
Project description:Aire in medullary thymic epithelial cells plays an essential role in the negative selection through expression of broad arrays of tissue-restricted antigens. We asked whether Aire could also activate the expression of tissue-restricted antigens in cortical thymic epithelial cells. We established a semi-knockin strain of NOD-background mice expressing Aire under control of the promoter of β5t, a thymoproteasome expressed exclusively in the cortex. We extracted RNA from cortical thymic epithelial cells ectopically expressing Aire and hybridization was performed on Affymetrix. microarrays.
Project description:Aire in medullary thymic epithelial cells plays an essential role in the negative selection through expression of broad arrays of tissue-restricted antigens. We asked whether Aire could also activate the expression of tissue-restricted antigens in cortical thymic epithelial cells.
Project description:Promiscuous gene expression (pGE) of numerous self-antigens in thymic epithelial cells (TEC) enables the elimination of self-reactive T cells. The autoimmune regulator (Aire) is the only known molecular determinant driving pGE in the thymus but the existence of Aire-independent mechanisms has been inferred. Here, we analyzed the poly(A)+ transcriptome of TEC populations by RNA-sequencing (RNA-seq) in order to reveal differential features of Aire-induced vs. –independent pGE. We report an unanticipated effect of Aire deletion on the proliferation and differentiation of cortical TEC. Moreover, the RNA-seq data reveal the breath of Aire-induced and –independent pGE in medullary TEC (mTEC) subsets and the extent of thymic peripheral tissue representation. The results suggest that Aire-induced promiscuously expressed transcripts affect several functions with far reaching biological consequences in mTEC. High-throughput characterization of TEC transcriptomes will enable progress in understanding TEC biology and the establishment of self-tolerance.
Project description:To investigate the role of Aire in thymic selection, we examined the cellular requirements for generation of ovalbumin (OVA)-specific CD4 and CD8 T cells in mice expressing OVA under the control of the rat insulin promoter (RIP). Aire-deficiency reduced the number of mature single positive (SP) OVA-specific CD4+ or CD8+ T cells in the thymus, independent of OVA expression. Importantly, it also contributed in two way to OVA-dependent negative selection depending on the T cell type. Aire-dependent negative selection of OVA-specific CD8 T cells correlated with Aire-regulated expression of OVA. By contrast, for OVA-specific CD4 T cells, Aire affected tolerance induction by a mechanism that operated independent of the level of OVA expression, controlling access of antigen presenting cells to mTEC-expressed OVA. This study supports the view that one mechanism by which Aire controls thymic negative selection is by regulating the indirect presentation of mTEC-derived antigens by thymic dendritic cells. It also indicates that mTEC can mediate tolerance by direct presentation of Aireregulated antigens to both CD4 and CD8 T cells. Total RNA was extracted from medullary thymic epithelial cells isolated from wildtype and Aire-deficient C57BL/6 mice for comparison of gene expression profiles.