Nr4a1 and Nr4a3 reporter mice are differentially sensitive to T cell receptor signal strength and duration

Nr4a receptors are activated by T cell receptor (TCR) signalling and play key roles in T cell differentiation. Which TCR signalling pathways regulate Nr4a receptors and their sensitivities to TCR signal strength and duration remains unclear. Utilising Nr4a1/Nur77-GFP and Nr4a3-Tocky mice, we elucidate the signalling pathways governing Nr4a receptor expression. We reveal that Nr4a1-3 are Src family kinase-dependent. Moreover, Nr4a2 and Nr4a3 are attenuated by calcineurin inhibitors and bind NFAT1, highlighting a necessary and sufficient role for NFAT in the control of Nr4a2 and Nr4a3, but redundancy for Nr4a1. Nr4a1-GFP is activated by tonic and cognate signals during T cell development, whilst Nr4a3-Tocky requires cognate peptide:MHC interactions for expression. Compared to Nr4a3-Tocky, Nr4a1-GFP is approximately 2-3-fold more sensitive to TCR signalling and is detectable by shorter periods of TCR signalling. These findings suggest that TCR signal duration maybe an underappreciated aspect influencing the developmental fate of T cells in vivo.