BioProject

Regulatory T (Treg) cells characterized by expression of the transcription factor forkhead box P3 (Foxp3) maintain immune homeostasis by suppressing self-destructive immune responses1-4. More...

Regulatory T (Treg) cells characterized by expression of the transcription factor forkhead box P3 (Foxp3) maintain immune homeostasis by suppressing self-destructive immune responses1-4. Foxp3 operates as a late acting differentiation factor controlling Treg cell homeostasis and function5, whereas the early Treg cell lineage commitment is regulated by the Akt kinase and the forkhead box O (Foxo) family of transcription factors6-10. However, whether Foxo proteins act beyond the Treg cell commitment stage to control Treg cell homeostasis and function remains largely unexplored. Here we show that Foxo1 is a pivotal regulator of Treg cell function. Treg cells express high amounts of Foxo1, and display reduced T-cell receptor-induced Akt activation, Foxo1 phosphorylation, and Foxo1 nuclear exclusion. Mice with Treg cell-specific deletion of Foxo1 develop a fatal inflammatory disorder similar in severity to Foxp3-deficient mice, but without the loss of Treg cells. Genome-wide analysis of Foxo1 binding sites reveals ~300 Foxo1-bound target genes, including the proinflammatory cytokine Ifng, that do not appear to be directly regulated by Foxp3. These findings demonstrate that the evolutionarily ancient Akt-Foxo1 signaling module controls a novel genetic program indispensable for Treg cell function. Overall design: Regulatory T cells were FACS sorted in WT mice (2 reps), Foxo1 KO mice (2 reps), mice expressing a constitutively active form of Foxo1 (1 rep), and Foxo1 KO mice expressing constitutively active Foxo1. We identified genes differentially expressed in WT vs. KO mice and assessed whether expression was recovered in the KO in presence of constitutively active Foxo1 Less...