During thymic development, most γδ T cells acquire innate-like characteristics that are critical for their function in tumor surveillance, infectious disease, and tissue repair. The mechanisms, however, that regulate γδ T cell developmental programming remain unclear. Recently, we demonstrated that the SLAM/SAP signaling pathway regulates the development and function of multiple innate-like γδ T cell subsets. Here, we used a single-cell proteogenomics approach to identify SAP-dependent developmental checkpoints and to define the SAP-dependent γδ TCR repertoire in mice. SAP deficiency resulted in both a significant loss of an immature Gzma+Blk+Etv5+Tox2+ γδT17 precursor population and a significant increase in Cd4+Cd8+Rorc+Ptcra+Rag1+ thymic γδ T cells. SAP-dependent diversion of embryonic day 17 thymic γδ T cell clonotypes into the αβ T cell developmental pathway was associated with a decreased frequency of mature clonotypes in neonatal thymus, and an altered γδ TCR repertoire in the periphery. Finally, we identify TRGV4/TRAV13-4(DV7)-expressing T cells as a novel, SAP-dependent Vγ4 γδT1 subset. Together, the data support a model in which SAP-dependent γδ/αβ T cell lineage commitment regulates γδ T cell developmental programming and shapes the γδ TCR repertoire.

γδ T cells have been demonstrated to both promote tumor growth/metastasis and to efficiently kill tumor cells. This dual role of γδ T cells has been attributed to their ability to produce either IL-17 (γδT17) or IFNγ (γδT1), the former being associated with tumor progression and the latter being associated with anti-tumor activity. γδ T cell function is influenced by multiple factors, including the recognition of stress-induced ligands, as well as cytokines and chemokines. However, the specific signals that lead to the selective activation and function of γδT17 or γδT1 subsets in different cancers remains unclear. Here, we explored these questions using a novel inducible mouse model of Kras-driven lung adenocarcinoma with or without a co-mutation in Stk11, a master regulator of metabolic pathways. Preliminary characterization of this model revealed that Kras G12D/Stk11 fl/flmice exhibited significantly greater morbidity than Kras G12Dmice. While lung leukocyte numbers did not differ significantly between Kras G12Dand Kras G12D/Stk11 fl/flmice, we noted a significantly increased frequency of γδT17, but not γδT1, subsets in Kras G12D/Stk11 fl/fllungs. Interestingly, the increased frequency of γδT17 was due to increased Vγ1 and Vγ6, but not Vγ4, γδT17 suggesting a selective expansion of these subsets. To examine a potential role for butyrophilins in these models, we assessed lung butyrophilin gene expression using qPCR. This analysis revealed increased expression of Btnl1, Btnl2, and Btnl9 in Kras G12Dlungs mice as compared to controls. Together, these results suggest that this model has the potential to shed new light on how the interaction of the tumor microenvironment with specific γδ T cell subsets affects disease pathogenesis.