Supplementary Figure 2: Previously reported markers are broadly expressed in the incisor growth region.

RNAscope in situ hybridization in mouse incisor growth region for Sox2 (a), Gli1 (d), Bmi1 (g) and Lrig1 (j); transcripts are visualized as red dots. Enlargements of the boxed insets from the dorsal (green) and ventral (orange) OEE, and the middle portion of the IEE (yellow) regions for each marker are shown on the right. Schematic view of the incisor growth region highlights the expression domains of the above genes. Sox2 (a’), Gli1 (d’) and Bmi1 (g’) are expressed throughout the proximal dental epithelium, including the OEE, IEE and the SR, whereas Lrig1 (j’) is present almost exclusively in the OEE and the OSR adjacent to the OEE. Representative images of RFP (Sox2, Lrig1 and Bmi1) or βgal (Gli1) immunostaining in the incisor growth region of Sox2^CreER;R26^tdTomato (b), Bmi1^CreER;R26^tdTomato (h), Lrig1^CreER;R26^tdTomato (k) and Gli1^CreER;R26^lacZ (e) mice 24 hours (top) or 21 days (bottom) after a single, low-dose tamoxifen injection. The initial labelling of all these markers was consistent with our in situ hybridization results, indicating that the progeny of Sox2, Gli1 and Bmi1 cells may originate from cells in any of the above regions. In contrast, cells labelled with Lrig1 were found exclusively in the OEE and condensed SR. Green, yellow and orange arrowheads in 24 hours chase mark cells in the dorsal, ventral OEE and IEE, respectively. Dashed lines outline incisor epithelium. SPRING plots of the entire control (top right) and of Class 1 after regressing out the cell cycle effect (right bottom), overlaid with gene expression of the above markers (Sox2 (c), Gli1 (f), Bmi1 (i) and Lrig1 (l); Color scale as in Fig. 1g. Scale bars, 100 μm.