GSE120451
Mitochondrial complex III is essential for regulatory T cell suppressive function. [DNA methylation/RRBS]
Regulatory T cells (Treg cells), a distinct subset of CD4+ T cells, are necessary for the maintenance of immune self-tolerance and homeostasis. Recent studies have demonstrated that Treg cells display a unique metabolic profile characterized by an increase in mitochondrial metabolism relative to other CD4+ effector subsets. Furthermore, the Treg cell lineage-defining transcription factor, Foxp3, has been shown to promote respiration; however, it remains unknown whether the mitochondrial respiratory chain is required for Treg cell suppressive capacity, stability, and survival. Here we report that Treg cell-specific ablation of mitochondrial respiratory chain complex III results in the development of a fatal inflammatory disease early in life, without impacting Treg cell number. Mice lacking complex III specifically in Treg cells displayed a loss of Treg cell suppressive capacity without altering Treg cell proliferation and survival. Treg cells deficient in complex III display decreased expression of genes associated with Treg function while maintaining stable FOXP3 expression. Complex III-null Treg cells displayed increased DNA methylation at the loci of differentially down-regulated genes without a global increase in DNA methylation. Loss of complex III in Treg cells resulted in buildup of the metabolites 2-hydroxyglutarate (2-HG) and succinate that can function as inhibitors of a-ketoglutarate (a-KG)-dependent dioxygenase reactions such as the ten-eleven translocation (TET) family of DNA demethylases. Thus, Treg cells require mitochondrial respiration to maintain immune regulatory gene expression and suppressive function. Overall design: Each experiment contains either WT controls animals compared to KO animals, or untreated controls compared to treated conditions.