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Impairment of organ-specific T cell negative selection by diabetes susceptibility genes: analysis by mRNA profiling

ABSTRACT: 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. Keywords: Murine

ORGANISM(S): Mus musculus

PROVIDER: GSE3997 | GEO | 2006/12/30

SECONDARY ACCESSION(S): PRJNA94273

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:Down syndrome (DS) patients frequently develop organ-specific autoimmune disorders, particularly endocrinopathies and coeliac disease, as well as an increased susceptibility to mucosal candidiasis. These clinical features resemble APECED (autoimmune-polyendocrinopathy-candidiasis-ectodermal-dystrophy), a monogenic condition due to mutations in the AIRE gene, located on 21q22.3 and already described as down-regulated in 21 trisomy. Here we investigated AIRE expression and global gene expression profiles in surgically removed thymuses from 14 DS infants and children with congenital heart defects and from 42 age-matched individuals with cardiac defect as an isolated malformation. Immunohistochemistry revealed significantly reduced AIRE expression in DS thymuses (70.48M-BM-149.59 positive cells/mm2 in DS X 154.70M-BM-161.16 in controls, p<0.0001). qPCR confirmed the lower expression of AIRE in DS thymuses. Global thymic RNA profiles from DS patients and controls revealed 407 genes significantly hypoexpressed in DS. Network transcriptional analysis showed that hypoexpressed genes are related to biological processes such as antigen processing and presentation of endogenous antigen (ERAP2, CD1D), negative (PRDX2) and positive (CD3D, CD74) thymic T-cell selection and homeostasis of number of cells (PRDX2). Altogether these findings may explain the high prevalence of autoimmune phenomena in DS patients. Moreover, our data are in accordance with previous findings of thymic abnormal development in DS patients, characterized by lymphocyte depletion, diminution of the cortex, and loss of corticomedullary demarcation. Global gene profiles indicate that in DS patients, the trisomic imbalance probably leads to thymic hypofunction. In conclusion, lower AIRE expression and the impairment of other crucial pathways for central tolerance could well explain the high prevalence of organ-specific autoimmune disorders in DS. Among the 14 DS infants and 42 age-matched individuals with cardiac defect, only 4 from each group provided enough biological material (thymus fragments) for isolation of high-quality RNA to perform array analysis. Eight thymic samples were analyzed: C1, C2, C3 and C4 are controls, and D1, D2, D3 and D4 are from patients with Down syndrome.

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Impairment of organ-specific T cell negative selection by diabetes susceptibility genes: analysis by mRNA profiling

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