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Genetic and transcriptome analyses of early T-cell checkpoint failure and leukemia initiation in Rag1-deficient NOD mice

ABSTRACT: Both immunodeficient and wild type NOD mice exhibit defects in control of early T-cell development in the thymus. We show that Rag1-deficient NOD mice fail to enforce both the b-selection checkpoint and an earlier T-cell commitment checkpoint, based on genome-wide genetic and transcriptome analyses. A major QTL peak for the checkpoint breakthrough phenotype mapped to the diabetes susceptibility Idd9/11 region, as confirmed by congenic mouse analysis. Genome-wide RNA deep-sequencing revealed two classes of differences between NOD and B6 Rag1-deficient thymocytes: first, effects of genetic background prior to breakthrough, and second, effects of the breakthrough itself. These genotypes differentially express numerous signal transduction genes, prominently tyrosine kinase and actin-binding genes, some located within QTL regions. Emerging NOD breakthrough cells depart from the expected DN3 phenotype by expressing many stem cell-associated proto-oncogenes, such as Lmo2, Hhex, Lyl1, and Kit which are normally repressed earlier, and by illegitimate activation of post-b-selection genes like Cd2, Cd5, and Cd4. Co-expression of stem cell and T-cell genes persists in thymic lymphoma cells that emerge with high penetrance in these mice. These results imply that NOD thymocytes have defects that can collapse regulatory boundaries at two early T-cell checkpoints, which may predispose them to leukemia and autoimmunity.

ORGANISM(S): Mus musculus

PROVIDER: GSE40688 | GEO | 2013/03/07

SECONDARY ACCESSION(S): PRJNA174611

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.

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Genetic and transcriptome analyses of early T-cell checkpoint failure and leukemia initiation in Rag1-deficient NOD mice

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