CD49a expression and induction of cytotoxicity on human tissue-resident CD8+ T cells is controlled by RUNX2 and RUNX3 transcription factor activity [ATAC-seq]. CD49a expression and induction of cytotoxicity on human tissue-resident CD8+ T cells is controlled by RUNX2 and RUNX3 transcription factor activity [ATAC-seq]

CD49a marks highly cytotoxic epidermal tissue-resident memory (TRM)-cells, but their molecular circuitry and relationships to circulating populations are poorly defined. We demonstrate enrichment of RUNX family transcription factor binding motifs in human epidermal CD8+CD103+CD49a+ TRM-cells, paralleled by high RUNX2 and RUNX3 protein expression. Clonal overlap between epidermal CD8+CD103+CD49a+ TRM-cells and circulating memory CD8+CD45RA–CD62L+ T-cells identified a reservoir of circulating cells with potential to seed cytotoxic TRM-cells in new sites. Upon IL-15 and TGF-β stimulation, subsets of circulating CD8+CD45RA–CD62L+ T-cells acquired CD49a expression and cytotoxic transcriptional profiles in a RUNX2 and RUNX3 dependent manner. In contrast, knock-out of RUNX3, but not RUNX2, prevented CD103 expression. In melanoma, high RUNX2, but not RUNX3, transcription correlated with a cytotoxic CD8+CD103+CD49a+ TRM cell signature and overall patient survival. Together, our results indicate that combined RUNX2 and RUNX3 activity promotes the differentiation of cytotoxic CD8+CD103+CD49a+ TRM-cells, providing immunosurveillance of infected and malignant cells. Overall design: CD69+ CD8 T cells from the dermis (CD103-CD49a- and CD103+CD49a-) and epidermis (CD103+CD49a- and CD103+CD49a+) of 4 healthy donors were FACS sorted and directly used for Omni ATAC-seq. **Submitter declares that raw data were not submitted due to patient privacy concerns**