(A) Representative ATAC sequencing tracks across the Tbx21 locus of NKp46+ ILC3s (Shih et al., 2016). The Tbx21 promoter and enhancer regions are highlighted in red (Yang et al., 2007). ATAC sequencing tracks were visualized using the WashU browser from the Cistrome project (Mei et al., 2017). (B) Positioning of putative Maf response elements (MARE) within the Tbx21 promoter and enhancer (highlighted in blue). Depicted sequences represent selected regions of the Tbx21 promoter and enhancer. Mutated sequences are shown in lower lines in red. (C) Schematic representation of plasmids containing the Tbx21 promoter/enhancer linked to the firefly luciferase reporter gene (Luc). Blue dots indicate MARE sites within the Tbx21 promoter and enhancer region. (D) Relative luciferase activity (RLU) of different reporter constructs driven by the Tbx21 promoter alone or in combination with an enhancer sequence compared to a promoterless (w/o) control vector (pGL3 basic) (n = 3, mean ± SEM, *p<0.05, ***p<0.001). (E) Analysis of c-Maf-dependent suppression of luciferase activity. The MARE sites within the Tbx21 promoter or the Tbx21 promoter and enhancer were mutated in the Tbx21 enhancer/promoter construct. Comparison of RLU between unmutated and mutated Tbx21 enhancer/promoter constructs upon c-Maf overexpression (n = 3, mean ± SEM, ***p<0.001). All reporter assay data are pooled from three independent experiments. (F) Expression of c-Maf by siLP CCR6- ILC3s from T-bet-deficient (T-bet-/-) and -sufficient (T-bet+/+) mice. Representative flow cytometric profiles are shown on the left; graph on the right shows quantification of c-Maf gMFI (n = 4, mean ± SEM, ***p<0.001). (G–H) Sort-purified siLP NKp46+ CCR6- ILC3s from RorcCre R26EYFP mice were cultured in vitro for 36 hr in the presence of IL-7/SCF (w/o) or IL-7/SCF plus indicated cytokines. Subsequently, Maf expression was measured by qPCR (n = 4, mean ± SEM, *p<0.05, **p<0.01, ***p<0.001). In one condition the NF-κb inhibitor BMS-345541 (BMS) was added at 1 μM to the culture. Data are pooled from two independent experiments each with two replicate wells. (I) Sort-purified siLP NKp46+ CCR6- ILC3s from RorcCre R26EYFP mice were cultured in the presence of IL-7/SCF on OP9 or OP9-DLL1 stromal cells as indicated. After 12 days, cells were analysed by flow cytometry for the cell surface expression of NKp46. Representative contour plots are shown on the left (pregated on CCR6- ILC3s); graph on the right shows quantification of the frequency of NKp46+ cell among CCR6- ILC3s (n = 10, mean ± SEM, ***p<0.001). Data are pooled from two independent experiments with 4 to 6 replicate wells. (J) Expression of c-Maf by NKp46+ CCR6- ILC3s cultured on OP9 or OP9-DLL1 cells. Representative histogram is shown left; graph on the right shows quantification of c-Maf gMFI (n = 10, mean ± SEM, ***p<0.001). All statistical differences were tested using an unpaired Students’ t-test (two-tailed).