Conserved non-coding sequence 2 (CNS2) of the Foxp3 genomic locus is essential for the function and stability of regulatory T cells during their activation

Regulatory T (Treg) cells play an indispensable role in immune homeostasis. The development and function of Tregs are dependent on transcriptional factor Foxp3, but how constant expression of Foxp3 is maintained in Tregs is not clear. Here we show that ablation of the conserved non-coding DNA sequence 2 (CNS2) at the Foxp3 locus in mice led to spontaneous lymphoproliferative disease and exacerbation of experimental autoimmune encephalomyelitis (EAE). CNS2 is required for activated Treg cells to maintain elevated Foxp3 expression, which is critical for their suppressor function and lineage stability. Mechanistically, upon TCR stimulation, NFAT binds to both CNS2 and Foxp3 promoter and mediates the interaction between CNS2 and Foxp3 promoter. Our findings demonstrated an essential role for CNS2 in maintaining the stability and function of activated Treg cells and identified NFAT as a key mediator of its function. Overall design: Gene expression was profiled in T regulatory cells (Treg) in WT and CNS2 knockout mice. CNS2 knockout mice lack a conserved non-coding DNA sequence 2 (CNS2) at the Foxp3 locus. Treg cells were further sorted into Foxp3-high and Foxp3-low populations based on the expression level of Foxp3. mRNA was profiled using RNA-Seq (unstranded, polyA+, SE100) in replicate for each condition

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Li X, Liang Y, LeBlanc M, Benner C, Zheng Y