The Methylcytosine Dioxygenase TET2 Regulates CD8⁺ T Cell Memory Differentiation

DNA methylation is one of the major epigenetic mechanisms that control T cell differentiation. The ten-eleven translocation (TET) family of methylcytosine dioxygenases converts 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and other oxidized methylcytosines, intermediates in active DNA demethylation. Here we demonstrate that TET2 regulates CD8⁺ T cell differentiation in vivo following acute viral infection. At steady-state, mice with a T-cell specific deletion of TET2 have intact thymic and peripheral T cell populations. However, following acute viral infection with LCMV-Armstrong, TET2 loss promotes early acquisition of a memory CD8⁺ T cell fate in a cell-intrinsic manner without disrupting antigen-driven cell expansion or effector function. Integration of genome-wide methylation analysis and expression data suggest that TET2 loss leads to hypermethyation of the PRDM1 genomic locus (encoding Blimp-1) and alters the relative expression of Blimp-1 and Bcl-6, two antagonistic transcriptional repressors known to direct CD8⁺ T cell memory differentiation. Together, our data indicate that TET2 is an important regulator of CD8⁺ T cell fate decisions.