Extended Data Fig. 2: Additional live images of McSC lineage tracing.

(a) Representative example of large tile images showing the pattern of HF distribution at each visit of the same area to guide repeated accurate tracing of the same HF. Z-stack images show GFP signal (K14⁺ epithelium) in Tyr-CreER;Rosa-LSL-tdTomato;K14-rtTA;tetO-H2B-GFP mice. Orange dashed lines mark hair follicle bundles (labeled, B1, B2, B3…). Overlapping patterns were used to identify specific HFs. Shown are representative images, N = 7 mice. (b) Additional examples of Fig. 1c. Z-stack images of three independent examples of HFs from in vivo imaging of Tyr-CreER;Rosa-LSL-tdTomato;K14-rtTA;tetO-H2B-GFP mice imaged as illustrated in Fig. 1b. A single tdTomato-labeled cell within each HF was initially visited at the first telogen stage; then revisited at early anagen, mid/late anagen, catagen and the next telogen (2^nd telogen). Shown are representative examples of Tom⁺ HG McSCs that undergo self-renewal and differentiation (top panels), self-renewal (middle panels) and differentiation (bottom panels). In the middle panels, note that one Tom⁺ cell died at the beginning of catagen, so only 4 Tom⁺ cells are present during catagen stages. Yellow dashed line outlines club hair. Dashed white lines outline epithelial-dermal boundary. HG: hair germ; Bb: bulb; Bg: bulge; ORS^up: upper ORS.