Project description:The regulation of thymocyte development by RNA-binding proteins (RBPs) is largely unexplored. We identified 642 RBPs in the thymus and focused on Arpp21, which shows selective and dynamic expression in early thymocytes. Arpp21 was downregulated in response to T cell receptor (TCR) and Ca2+ signals. Downregulation required Stim1/Stim2 and CaMK4 expression and involved Arpp21 protein phosphorylation, polyubiquitination and proteasomal degradation. Arpp21 directly bound RNA through its R3H domain, with a preference for uridine-rich motifs, promoting the expression of target mRNAs. Analysis of the Arpp21-bound transcriptome revealed strong interactions with the Rag1 3'-UTR. Arpp21-deficient thymocytes showed reduced Rag1 expression, delayed TCR rearrangement and a less diverse TCR repertoire. This phenotype was recapitulated in Rag1 3'-UTR mutant mice harboring a deletion of the Arpp21 response region. These findings show how thymocyte-specific Arpp21 promotes Rag1 expression to enable TCR repertoire diversity until signals from the TCR terminate Arpp21 and Rag1 activities.
Project description:<p>Diversity and size of the antigen-specific T cell receptor (TCR) repertoire are two critical determinants for successful control of chronic infection. Varicella zoster virus (VZV) that establishes latency during childhood is able to escape control mechanisms, in particular with increasing age. We examined the TCR diversity of VZV-specific CD4 T cells in individuals older than 50 years by studying three identical twin pairs and three unrelated individuals before and after vaccination with live attenuated VZV. While all individuals had a small number of dominant T cell clones, the breadth of the VZV-specific repertoire differed markedly among different individuals. A genetic influence was seen for the sharing of individual TCR sequences from antigen-specific cells, but not for repertoire richness or the selection of clonal dominance. VZV vaccination favored the expansion of infrequent VZV-specific TCRs including those from naïve T cells while leaving dominant T cell clones mostly unaffected.</p>
Project description:While histone H3 lysine 27 trimethylation (H3K27Me3) is associated with gene silencing, whether H3K27Me3 demethylation affects transcription and cell differentiation in vivo has remained elusive. To investigate this, we conditionally inactivated the two H3K27Me3 demethylases, Jmjd3 and Utx, in non-dividing intrathymic CD4+ T cell precursors. We show that both enzymes redundantly promote H3K27Me3 removal at, and expression of, a specific subset of genes involved in terminal thymocyte differentiation, especially S1pr1, encoding a sphingosine-phosphate receptor required for thymocyte egress. Floxed alleles of the genes encoding Utx and Jmjd3 (Kdm6a and Kdm6b, respectively) were deleted in double positive (DP) thymocytes carrying a CD4 Cre transgene. Genome-wide H3K27Me3 ChipSeq was performed on (i) pre-selection (CD69lo) DP thymocytes from wild-type mice carrying an endogenous polyclonal TCR repertoire, (ii) mature (TCRhi CD24lo) CD4 SP thymocytes from wild type (Wt), Jmjd3KO, UtxKO and dKO mice carrying an endogenous polyclonal TCR repertoire and (iii) mature (Va2hi CD24lo) CD4 SP thymocytes from wild type and dKO mice carrying the OTII TCR transgene.
Project description:To investigate specific miRNA expression profiles of Marek's disease virus (MDV)-infected samples, we performed deep sequencing for miRNAs in four small RNA libraries, including MDV-infected tumorous spleen, MD lymphoma from liver, and non-infected spleen and lymphocytes from controls. A total of 7.76x106, 6.36x106, 6.36x106, and 7.60x106 counts were obtained in four libraries, respectively. The sequences were blasted with chicken and MDV genomes and miRBase 16.0 to identify known and novel miRNAs. In total, 187 and 16 known mature miRNAs were identified in the chicken and MDV, respectively. Deep sequencing detected 942 novel chicken miRNA candidates, of which 646 were in tumorous spleen. These results indicate that MDV infection induced new host miRNA candidates and increased diversity of miRNAs. Of 942 miRNA candidates, 276 of 533 were verified by customized microarray, and 17 of them were further confirmed by qPCR.