A unique epigenetic circuitry defines CD8 T cell stemness shared across chronic diseases 2330201

Abstract Introduction In autoimmunity and chronic infection, both settings of persistent (self or foreign) antigen, immune responses are sustained by stem-like CD8 T cells, which self-renew and give rise to differentiated progeny. However, if and how T stemness is epigenetically encoded, which transcription factor(s) regulate the stem-T cells, and whether the stem-T cell state is disease-specific or shared across diseases, is currently not known. Methods We used clinically relevant models of autoimmune type 1 diabetes (T1D) and chronic infection and conducted serial T cell transplantation studies in vivo, combined with single cell paired RNA- and ATAC-sequencing on antigen-specific T cells. We developed CRISPR/Cas9-mediated gene-editing approaches in primary T cells as well as CUT&RUN studies, identifying a novel hierarchy of transcription factors regulating stem T cell identity and function. Results We discovered that a small subset of stem-T cells (TSC) express lymphoid enhancer-binding factor 1 (LEF1), a member of the TCF/LEF TF family. Paired single cell transcriptomic and epigenomic analyses reveal that the LEF1+ TSC harbor a unique epigenetically encoded molecular state enriched in genes and pathways characteristic of embryonic and adult (somatic) stem cells (e.g. neural stem cells). Strikingly, we found that TSC in chronic infection harbor a LEF1+ TSC pool sharing the core stemness epigenetic and molecular program observed in autoimmune LEF1+ TSC. Loss- and gain-of-function studies in both autoimmune T1D and chronic infection confirmed the critical role of LEF1 in maintaining T cell stemness. CUT&RUN analyses provide clues as to how LEF1 instructs the epigenetically encoded program of stem-T cells. Conclusion Here we reveal novel insights into the molecular circuitries of CD8 T cell stemness and differentiation. We discover LEF1 as the master regulator defining T cell stemness and identify novel targets for therapeutic intervention. Funding Source NIH R01AI173249, JDRF SRA-2023-1410-S-B, MSKCC Basic Research Innovation Award, The Hearst Foundation Topic Categories Lymphocyte Differentiation and Peripheral Maintenance (LYM)