Extended Data Fig. 10: Dct-CreER^T2 mice enable the specific targeting of McSCs in hair follicles, allowing the controlled induction of invasive melanoma.

a, Experimental scheme for tracing of McSC-lineage cells. b, Distribution of GFP⁺ cells in the dorsal skin of Dct-CreER^T2; Rosa-H2B-GFP^KI/+ or Tyr-CreER^T2; Rosa-H2B-GFP^KI/+ mice at 4 weeks post-TAM injection. GFP⁺ cells in the dermis of Tyr-CreER^T2; Rosa-H2B-GFP^KI/+ mice are indicated by a yellow arrowhead. Scale Bar = 60 μm. c, Distribution of GFP⁺ cells in hair follicles of Dct-H2B-GFP KI mice at telogen and anagen. GFP⁺ cells in the bulge represent McSCs. Scale Bars = 60 μm. d, The percentage of GFP⁺ cells located in the dorsal skin of Tyr-CreER^T2; Rosa-H2B-GFP^KI/+ mice (Tyr promoter) and of Dct-H2B-GFP KI mice (Dct promoter). A total of 388 GFP+ cells and 269 GFP+ cells were counted for the Tyr promoter (n=2) and Dct promoter (n=3), respectively (biological independent experiments). e, Distribution of tdTomato⁺ cells in hair follicles of Dct-CreER^T2; Rosa-tdTomato mice. Arrowheads indicate tdTomato⁺/KIT⁺ cells in the hair follicle. Scale Bars = 20 μm. f, Tyr-CreER^T2; Braf^V600E; Pten^fx/fx mice were depilated and injected with TAM for 3 consecutive days. Macroscopic view of Tyr-CreER^T2; Braf^V600E; Pten^fx/fx mice at 1 month after the 1st TAM injection. Expansion of GFP⁺ melanocytic lineages in the dermis of the mice was visualized using the Dct-H2B-GFP transgene. g, Macroscopic views of the dorsal skin of WT and of Dct-CreER^T2; Braf^V600E; Pten^fx/fx (DBP) mice at the indicated time points post-onset TAM injection. One-half of the dorsal skin was depilated. Yellow arrows indicate dome-like unpigmented nodules that mimic human Nodular-type melanomas. Graphs showing the quantification of melanomas (shown by yellow arrows) on the dorsal skin at 4 weeks (WT; n=20, DBP; n=11, biological independent experiments) and at 8 weeks (WT; n=8, DBP; n=6, biological independent experiments). Data are presented as means ± SEM. Mann-Whitney’s U-tests. h, Dct-H2B-GFP mice or Rosa-tdTomato mice were used to trace the fate of McSC-lineage cells. Immunohistological analysis of the dorsal skin of Dct-H2B-GFP and of DBP mice at the indicated time points post-onset TAM injection. The two panels of DBP mice at 4 weeks post-onset TAM injection show different hair follicles of the same skin. Scale Bars = 100 μm. i, Macroscopic images of lymph nodes (LN).

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