Down-regulation of Tet2 prevents TSDR demethylation in IL2 deficient regulatory T cells
Introduction
Forkhead box P3+ (Foxp3+) Treg cells are a dedicated cell population that maintains immune tolerance and prevents autoimmune diseases [1], [2]. Since Treg cells regulate immune responses usually in a Foxp3-dependent manner [3], [4], the stability of Foxp3 is critical. Indeed, T cells whose Foxp3 was shut down have been reported to play roles in the development of some inflammatory diseases like diabetes [5] and lethal infection [6]. Stable Foxp3 expression is related to the epigenetic mechanisms, namely DNA demethylation of the conserved non-coding regions in foxp3 locus, called Treg cell specific demethylation region (TSDR) [7], [8]. In Treg cells with demethylated TSDR, Foxp3 protein binds to the demethylated TSDR and enhances its own expression, which induces the positive feedback loop [9]. However, the detail mechanism of TSDR demethylation is unknown.
Interleukin-2 (IL2) plays dual and often opposing roles in immune responses, contributing to both the generation of effector T cells and the maintenance of Foxp3+ Treg cells [10], [11]. Many studies indicate that IL2 provides essential signals for Tregs in at least 3 different levels: thymic development [12], [13], competitive fitness [14], [15] and Foxp3 stability [16], [17], [18], [19]. Here, we studied TSDR demethylation in IL2 deficient Treg cells and found that IL2 and epigenetic changes in foxp3 locus are closely related, which, as a result, helps Treg cells to express Foxp3 stably.
Section snippets
Mice
CD45.1 congenic (B6.SJL-Ptprca Pepcb/BoyJ), IL2 deficient (B6.129P2-Il2tm1Hor/J, Il2−/−), Foxp3-GFP transgenic (Foxp3 bicistronic reporter mice expressing EGFP: B6.Cg-Foxp3tm2Tch/J), Bcl2 transgenic (B6.Cg-Tg(BCL2)25Wehi/J, hBcl-2TG), Lck-Cre transgenic (B6.Cg-Tg(Lck-cre)548Jxm/J), and floxed Tet2 transgenic (B6;129S-Tet2tm1.1Iaai/J, Tet2fl/fl) mice were obtained from The Jackson Laboratory (Bar Harbor, ME). Il2−/− mice were crossed to Foxp3-GFP transgenic mice to identify Treg cells (GFP+) and
IL2 plays essential roles in TSDR demethylation
While the suppressive function of Il2−/− peripheral Treg (pTreg) cells [22] was examined, we accidentally found that many Il2−/− pTreg cells lost Foxp3 expression (data not shown). These results led us to study the role of IL2 in Foxp3 stability and TSDR demethylation. WT pTreg cells (GFP+CD25+ and GFP+CD25−) and naïve T cells (GFP−CD25−) were FACS-sorted and used for the analysis of TSDR. The purified cells were also cultured with recombinant IL2 (rIL2) and anti-CD3 plus anti-CD28 mAbs
Disclosures
The authors have no conflicting financial interests.
Acknowledgments
We thank Guoliang Xu for Tet2 expression vector; Hyun-Ah Lee (Central laboratory Kangwon National University, Korea) for cell sorting; Eunbyeol Cheon for genotyping; Divya Chandrasekharan Nair for editing. This work was supported by the National Research Foundation of Korea (NRF-2007-0052254, NRF-2013R1A1A2059821) and Hallym University (HRF-201211-016).
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2020, Life SciencesCitation Excerpt :In physiological condition, the relationship between Tet2 and Foxp3 TSDR methylation had been studied. Down-regulation of Tet2 could prevent TSDR demethylation in Il2 deficient Treg cells, and over-expression of Tet2 restored TSDR demethylation [44]. Tet1 and Tet2 deletion led to hypermethylation of Foxp3 promoter and TSDR, impaired Treg cell differentiation and function, and disturbed immune homeostasis [28].
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2019, Journal of Molecular BiologyCitation Excerpt :Only in Treg cells is complete demethylation actively catalyzed by methylcytosine dioxygenases of the ten–eleven translocation (Tet) family [13,20–22]. This mechanism appears to be guided by IL-2 and is implemented with stage-dependent kinetics during tTreg differentiation [21,22]. Of the 14 CpG residues within the region, CpGs 9, 12, 13, and 14 are demethylated early and are located in the downstream half of the region indicating an initiation function for the epigenetic opening of the TSDR within this part [22] (Fig. 1a).
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