Loss of Foxp3-driven epigenetic modification leads to regulatory T cell insufficiency

Regulatory T cells (Tregs) are responsible for limiting autoimmunity and chronic inflammation. Foxp3 is a transcription factor that acts as a master regulator of Treg development and function. A serendipitous observation led to the realization that a well-characterized Foxp3gfp reporter mouse, which expresses an N-terminal GFP-Foxp3 fusion protein, is a hypomorph that causes profoundly accelerated autoimmune diabetes on a NOD background. Although natural Treg development and in vitro function is not significantly altered in Foxp3gfp NOD and C57BL/6 mice, Treg fitness function in inflammatory environments is perturbed and TGFβ-induced Treg development reduced. Foxp3gfpis unable to interact with the histone acetyltransferase Tip60, the histone deacetylase HDAC7, and the Ikaros family zinc finger 4, Eos, which leads to reduced Foxp3 acetylation and enhanced K48-linked polyubiquitylation. Collectively this leads to an altered transcriptional landscape and reduced Foxp3-mediated gene repression, notably at the hallmark IL-2 promoter. Loss of controlled Foxp3-driven epigenetic modification leads to Treg insufficiency that causes autoimmunity in prone environments. 16 samples overall split between 2 genotypes (wild type and Foxp3 knock in) and two cell types (Tregs and Tconv)