Expression and regulation of lincRNAs during T cell development and differentiation
Although lincRNAs are implicated in regulating gene expression in various tissues, little is known about lincRNA transcriptomes in the T cell lineages. Here we identify 1,524 lincRNAs in 42 T cell samples from early T cell progenitors to terminally differentiated T helper subsets. Our analysis revealed highly dynamic and cell-specific expression patterns of lincRNAs during T cell differentiation. Importantly, these lincRNAs are located in genomic regions enriched for protein-coding genes with immune-regulatory functions.  Many of these transcripts are bound and regulated by the key T cell transcription factors, T-bet, GATA3, STAT4 and STAT6. We demonstrate that the lincRNA LincR-Ccr2-5''AS, together with GATA3, is an essential component of a regulatory circuit in Th2-specific gene expression. Overall design: To obtain comprehensive profiles of lincRNA expression during the development and differentiation of T cell lineages, we purified CD4-CD8 double negative (DN) cells (DN1, DN2, DN3 and DN4), double positive (DP) cells (CD4+CD8+CD3low and CD4+CD8intCD69+), single positive (SP) CD4 and CD8 cells, and thymic-derived regulatory T cells (tTreg) from thymi of C57BL/6 mice. Additionally, we obtained Th1, Th2, Th17 and iTreg cells by in vitro differentiation of naïve CD4 T cells for a various length of time in culture (4 hrs, 8 hrs, 12 hrs, 24 hrs, 48 hrs, 72 hrs, 1 week, 2weeks). Total and/or polyadenylated RNAs from these cells was analyzed using RNA-Seq. To understand the regulation of lincRNAs by T cell master regulator T-bet, we compared the transcriptiomes between T-bet deficient Th1 cells and control Th1 cells. We did similar experiments and data analysis for STAT4 (Th1), GATA3 (Th2) and STAT6 (Th2). Finally, to address the funcation of a Th2-specifically expressed lincRNA, lincR-Ccr2-5''AS, we compared the transcriptomes between lincR-Ccr2-5''AS knockdown Th2 cells and control Th2 cells.