Lkb1 maintains T<sub>reg</sub> cell lineage identity.

Wu, Di; Luo, Yuechen; Guo, Wei; Niu, Qing; Xue, Ting; Yang, Fei; Sun, Xiaolei; Chen, Song et al. · Nat Commun · 2017

basic_science · Level V

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Abstract

Regulatory T (T<sub>reg</sub>) cells are a distinct T-cell lineage characterized by sustained Foxp3 expression and potent suppressor function, but the upstream dominant factors that preserve T<sub>reg</sub> lineage-specific features are mostly unknown. Here, we show that Lkb1 maintains T<sub>reg</sub> cell lineage identity by stabilizing Foxp3 expression and enforcing suppressor function. Upon T-cell receptor (TCR) stimulation Lkb1 protein expression is upregulated in T<sub>reg</sub> cells but not in conventional T cells. Mice with T<sub>reg</sub> cell-specific deletion of Lkb1 develop a fatal early-onset autoimmune disease, with no Foxp3 expression in most T<sub>reg</sub> cells. Lkb1 stabilizes Foxp3 expression by preventing STAT4-mediated methylation of the conserved noncoding sequence 2 (CNS2) in the Foxp3 locus. Independent of maintaining Foxp3 expression, Lkb1 programs the expression of a wide spectrum of immunosuppressive genes, through mechanisms involving the augmentation of TGF-β signalling. These findings identify a critical function of Lkb1 in maintaining T<sub>reg</sub> cell lineage identity.

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