Supplementary Figure 7: Assessment of the effect of 5FU treatment on Notch1-expressing cells.
a, Schematic of 5FU and tamoxifen (Tam) treatment schedule. Notch1CreER;R26tdTomato mice were dosed three times with Tam to lineage-trace Notch1-expressing cells and their descendants in steady state and during recovery from 5FU injury. b, Immunostaining for tdTomato (red) in control (left) and 5FU-treated (right two panels) mice analyzed 5 days and 21 days after the Tam induction. Scale bar,100 µm. c, Schematic of mechanical injury schedule. d, The distal portion of the incisor of Notch1CreER;R26mTmG mice was mechanically severed and the proximal region grown under the kidney capsule of a host mouse to lineage-trace Notch1-expressing cells and their descendants in steady state and during recovery from mechanical injury. Intact incisors were used as control. Bottom panel: Confocal images of control (left) and injured (right) mice analyzed 10 days after the treatment. Cells that underwent Cre recombination were permanently labeled with membrane GFP (mG). Very few cells reached the ameloblast layer in control (yellow arrowheads), while numerous traced cells reached the ameloblast layer during recovery from mechanical injury (yellow arrowheads). Scale bars,100 µm. e, TUNEL (red) and GFP (mG;green) staining revealed high levels of apoptotic cell death in the SI region of the incisor epithelium of Notch1CreER; RosaDTA/+ 2 days after TAM induction. Scale bar,100 µm. f, Schematic of the hierarchy of the three cell classes during homeostasis and injury repair. Actively cycling IEE cells (blue) generate both the enamel-producing ameloblasts (grey) and the adjacent non-ameloblast epithelial cells (orange). During injury repair, additional progenitors enter cell cycle, and SI cells are converted to become ameloblasts.
