Assessing the impact of TET2 and TET3 deletion in TCRa and TCRb expression and repertoire in murine CD4 T cells in physiological and pathological conditions [TCR-SEQ]

TET proteins mediate DNA demethylation by oxidizing 5-methylcytosine to 5-hydroxymethylcytosine (5hmC) and other oxidative derivatives. While we have previously demonstrated a dynamic enrichment of 5hmC during T cell lineage specification, the impact of TET proteins in CD4 cell lineage differentiation remains largely unknown. Here, we discover that TET proteins exert a fundamental role in regulating the differentiation and maturation of the CD4 lineage by controlling the expression of the lineage specifying factor Th-POK, which is encoded by Zbtb7b. We demonstrate that TET proteins mediate DNA demethylation of a proximal enhancer, critical for the stability of Th-POK expression. In addition, TET proteins drive the DNA demethylation of site A at the Zbtb7b locus to facilitate GATA3 binding, an event critical for Th-POK expression and subsequent CD4 maturation. The impaired maturation of Tet2/3 DKO CD4 cells leads to the acquisition of a stemness signature and results in acquisition of malignant traits.