Oleic Acid Availability Preprograms Early Thymocytes for Treg Cell Commitment in the Periphery

The natures of activation signals are essential in determining T cell subset differentiation, however, the properties of T cell subset preference acquired during intrathymic development remain elusive. Here we show that naïve CD4+ T cells generated in the thymic microenvironment lacking SCD1, the enzyme catalyzing oleic acid production, exhibit enhanced Treg cell differentiation and confer on mice the ability to resist EAE. SCD1 deletion in K14+ thymic epithelia recapitulated the enhanced Treg cell differentiation phenotype of SCD1 knockout mice. The dearth of oleic acid permitted Dot1L to increase H3K79me2 level at the Atp2a2 locus of thymocytes at the DN2-DN3 transition stage. Such epigenetic modification persisted to naïve CD4+ T cells and facilitated Atp2a2 expression. Upon TCR activation, Atp2a2 enhanced the activity of calcium-NFAT1-Foxp3 axis to promote naïve CD4+ T cells to differentiate into Treg cells. Therefore, oleic acid availability is critical for preprogramming thymocytes with Treg differentiation propensities in periphery. Chromatin immunoprecipitation DNA-sequencing (ChIP-seq) for histone modification H3K79me2 in in vitro developed DN3 thymocytes with or without SCD1 inhibitor treatment.