Genome-wide regulatory analysis reveals T-bet controls Th17 lineage differentiation through direct suppression of IRF4. Mus musculus

The complex relationship between Th1 and Th17 cells is incompletely understood. The transcription factor T-bet is best known as the master regulator of Th1 lineage commitment. However, attention is now focused on the repression of alternate T cell subsets mediated by T-bet, particularly the Th17 lineage. Specifically it has recently been suggested that pathogenic Th17 cells express T-bet and are dependent on IL-23. However, T-bet has previously been shown to be a negative regulator of Th17 cells. We have taken an unbiased approach to determine the functional impact of T-bet on Th17 lineage commitment. Genome-wide analysis of functional T-bet binding sites provides an improved understanding of the transcriptional regulation mediated by T-bet, and suggests novel mechanisms by which T-bet regulates T helper cell differentiation. Specifically, we show that T-bet negatively regulates Th17 lineage commitment via direct repression of the transcription factor interferon regulatory factor-4 (IRF4). An in vivo analysis of the pathogenicity of T-bet deficient T cells demonstrated that Th17 responses were augmented in the absence of T-bet, and we have defined a critical temporal window for T-bet function. The interaction of the two key transcription factors T-bet and IRF4 during the determination of T cell fate choice significantly advances our understanding of the mechanisms underlying the development of pathogenic T cells. Overall design: ChIP-seq analysis of T-bet in WT and Tbet -/- mice.

Th1与Th17细胞间的复杂关联迄今尚未完全阐明。转录因子T-bet（T-bet）作为调控Th1细胞谱系定型的核心主控调节因子，其功能早已被学界广泛认知。然而，当前研究焦点正转向T-bet介导的对其他T细胞亚群的抑制效应，尤其是对Th17细胞谱系的调控。
近期有研究指出，致病性Th17细胞可表达T-bet且依赖于白细胞介素-23（IL-23），但此前已有研究证实T-bet是Th17细胞的负向调节因子。本研究采用无偏倚实验策略，以解析T-bet对Th17细胞谱系定型的功能性影响。对功能性T-bet结合位点开展全基因组分析，不仅加深了我们对T-bet介导的转录调控机制的理解，还揭示了T-bet调控辅助性T细胞分化的全新途径。
本研究证实，T-bet可通过直接抑制转录因子干扰素调节因子4（IRF4），负向调控Th17细胞的谱系定型。对T-bet缺陷T细胞的体内致病性分析表明，在T-bet缺失的情况下，Th17细胞应答会显著增强；同时本研究明确了T-bet发挥功能的关键时间窗口。
T-bet与IRF4这两种关键转录因子在T细胞命运决定过程中的相互作用，极大推进了我们对致病性T细胞发育潜在机制的认知。
整体实验设计：对野生型（WT）及T-bet敲除（Tbet -/-）小鼠体内的T-bet进行染色质免疫沉淀测序（ChIP-seq）分析。