Genetic tracing of thymic T cell differentiation

• Published in: The Journal of immunology (1950) Vol. 210; no. 1_Supplement; pp. 219 - 219.05
• Main Authors: Jiang, Menglin, Keith, Julia, Zong, Xinying, Hao, Xiaolei, Li, Yichao, Bai, Lu, He, Minghong, Guy, Cliff, Li, Jun, Huang, Wenjun, Cheng, Yong, Feng, Yongqiang
• Format: Journal Article
• Language: English
• Published: 01-05-2023
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.210.Supp.219.05

Abstract
Thymic T cell differentiation is controlled by stereotyped processes that remain obscure. Here we develop a novel mouse genetic tool to trace thymic T cells during T cell antigen receptor (TCR) rearrangement. Briefly, we insert inducible CreER into the Rag1 locus that is transiently expressed at early thymic T cell differentiation. In the presence of Rosa reporters, Rag1-CreER mice enable us to irreversibly label T cells between the double negative (DN) and double positive (DP) stages upon acute tamoxifen treatment. In the physiological setting and absence of the perturbations historically used to investigate thymic T cell differentiation, our genetic tracing in combination with flow cytometric measurement of cell fates and functional states maps the kinetics, stoichiometry, and cell fate determination of thymic T cells. We further integrate genetic tracing experiments with unbiased single cell RNA sequencing, TCR sequencing, and the expression of cell surface markers, linking thymic T cell differentiation stages to dynamic gene expression. In particular, we show that regulatory T cells acquire CD73 expression over time as a potential consequence of persistent TCR signaling and expression of lineage determinant Foxp3, marking a maturation process during lineage commitment and functional adaptation. Taken together, our integrated genetic tracing of thymic T cells resolves complex differentiation processes coupled with the alterations of gene expression, selection, and cell fate determination. Our results also serve as a foundation for further exploration of the thymic T cell states, developmental pathways, drivers, and modulators involved in these crucial biological processes.
R21 AI146614