a, Schematic of strategy used to generate Clucre-ERT2 knockin mouse line (top; also see Methods). Clucre-ERT2/+;Rosa26lsl-tdTomato/+ mice (ClutdTomato) treated with or without TAM, and analysed at 2 and 6 dpi, as indicated, were stained using smFISH to simultaneously detect tdTomato and endogenous Clu mRNA transcripts (bottom left), or analysed by immunofluorescence at 6 dpi in non-TAM treated mice (bottom right). Note that tdTomato and Clu strongly overlap in TAM-treated mice whereas no tdTomato is detected without TAM (n = 2 mice). b, Representative images showing tdTomato expression detected in the indicated intestinal epithelia of ClutdTomato reporter mice in the presence or absence of irradiation (n = 2 independent experiments with similar results), that were treated with TAM at 1 dpi and analysed at 6 dpi. Scale bars, 35 μm (a); 70 μm (b).