GSE202871
Tracking regulatory T cell development in the thymus using scRNA-Seq/TCR-Seq
Recent studies have demonstrated that mature regulatory T cells ( Tregs) develop in the thymus via two pathways involving distinct Treg progenitors (TregP) - CD25+FOXP3- (CD25+ TregP) and CD25-FOXP3lo (FOXP3lo TregP) Treg progenitors. To examine this process in more detail we carried out single-cell RNA-Seq and TCR-Seq on sorted CD4+CD8+ double-positive (DP) thymocytes, CD4+ Ssingle -positive (CD4SP)P thymocytes, CD25+ TregP, FOXP3lo TregP, mature CD25+FOXP3+ Tregs and recirculating/long-term resident Tregs (RT-Tregs). Sorted populations were individually hashtagged and then combined into one scRNA-Seq/TCR-Seq library before sequencing and subsequent analysis. We found that both CD25+ TregP and FOXP3lo TregP arise via an initial agonist activated state that gives rise to a second transitional stage before differentiating into mature Tregs. Using both scRNA-Seq and bulk RNA-Seq on sorted thymocyte subsets we demonstrate that CD25+Foxp3- TregP are significantly enriched for Il2 production, suggesting that they are the major source of IL-2 needed to convert TregP into mature Tregs. Using TCR-Seq we found that several TCRs were clearly biased in favor of the conventional or Treg lineages, but that a large fraction of TCRs were found in both these lineages. Finally, we found that recirculating/resident Tregs in the thymus are not monomorphic, but are composed of multiple distinct subsets and that these RT-Tregs express the most diverse TCR repertoire of all CD4SP thymcocytes. Thus, our studies define multiple stages of Treg differentiation within the thymus, and serve as a resource for future studies on CD4+ thymocyte development and Treg differentiation. Overall design: This data is derived from cells sorted in a single experiment with samples from 3 biological replicates.