Distinct Runx1 isoforms induce alternative effector CD8 T cell states 4364

Description The Runt-family of transcription factors (TFs) are all expressed in effector CD8 T cells. Runx3 is the most studied due to its perturbation phenotype that results in the failure to establish cytotoxicity, and the loss of the memory precursor and tissue-resident memory compartment. In contrast, Runx1 and Runx2 perturbation leads to minimal effects on KLRG1 by CD127 phenotypes. However, single cell RNA sequencing of day 8 P14 TCR-transgenic CD8 T cells responding to acute LCMV-Armstrong revealed distinct expression patterns of all three Runt TFs across Leiden clusters, notably high Runx1 expression in terminal effectors. We cloned Runx1 from cDNA and identified two distinct isoforms which differed by the inclusion of the 192-bp exon 6 which encodes a conserved Ets1-interaction domain. Enforced expression of full length Runx1 (Runx1-FL) generated higher numbers of KLRG1- CD127+ memory precursors at day 8 in an Ets1-dependent manner, that was distinct from Runx3 overexpression which favored KLRG1+ CD127+ double positive effectors. Enforced expression of Runx1 lacking exon 6 (Runx1-ΔE6) resulted in five-fold more accumulation of all effector phenotypes that significantly contracted at day 15 and remained predominantly KLRG1+ CD127-. These results show that Runx1 isoforms play a role in specifying CD8 effector and memory differentiation. Funding Sources NIAID P01 AI145815 to M. Pipkin; AHA 24PRE1191318 to D. Albao Topic Categories Lymphocyte Differentiation and Peripheral Maintenance (LYM)