The Nuclear Receptor Nr4a1 Controls CD8 T Cell Development Through Transcriptional Suppression of Runx3

The NR4A nuclear receptor family member Nr4a1 is strongly induced in thymocytes undergoing selection, and has been shown to control the development of T(reg) cells; however the role of Nr4a1 in CD8(+) T cells remains undefined. Here we report a novel role for Nr4a1 in regulating the development and frequency of CD8(+) T cells through direct transcriptional control of Runx3. We discovered that Nr4a1 recruits the corepressor, CoREST to suppress Runx3 expression in CD8(+) T cells. Loss of Nr4a1 results in increased Runx3 expression in thymocytes which consequently causes a 2-fold increase in the frequency and total number of intrathymic and peripheral CD8(+) T cells. Our findings establish Nr4a1 as a novel and critical player in the regulation of CD8 T cell development through the direct suppression of Runx3.