R26r eyfp

All the experiments were approved by the ethical committee from the university and conform with regulatory standards (LA1230406, project 666N). Mice were bred and maintained under pathogen-free conditions in a certified animal facility in accordance with the European guidelines. Adult (8-week-old) wild-type CD1 mice or Krt8-YFP knock-in mice (18 (link)) were used for sequencing and histology. Krt5-CreER^T2 knock-in mice (the Jackson Laboratory, stock no. 029155; RRID:IMSR_JAX:029155) were crossed with R26R-EYFP (the Jackson Laboratory, stock no. 006148; RRID:IMSR_JAX:006148) to generate Krt5-CreERT2:R26R-EYFP (K5:RYFP) mice. For lineage tracing experiments, 10 or 0.25 mg of TAM resuspended in sunflower oil was injected intraperitoneally to 8-week-old K5:RYFP mice, and the expression of the YFP was analyzed in esophagi up to 4 weeks after TAM administration. In all the experiments, littermates of the same sex were randomly assigned to experimental groups.

Development and genotyping information for mouse lines Sftpc^CreERT2, Fgfr2^fl/fl (Jackson Laboratory stock # 007569), R26R^EYFP (Jackson Laboratory stock # 007903), Ai14(RCL-tdT)-D (R26R^tdTomato) (Jackson Laboratory stock # 007914), and Ect2^fl/fl have been previously described (Chapman et al., 2011 (link); Madisen et al., 2010 (link); Windmueller et al., 2020 (link); Yu et al., 2003 (link)). Fgfr2^fl/fl, R26R^tdTomato, and R26R^EYFP mouse lines were purchased from the Jackson Laboratory. All mice were maintained on a mixed background (C57BL/6 and CD1). No obvious defects were observed in heterozygous mice, so Sftpc^CreERT2;Fgfr2^fl/+;R26R^EYFP and Sftpc^CreERT2;Ect2^fl/+;R26R^EYFP littermates were used as controls for all experiments except for the organoid experiments in Figure 4 where Sftpc^CreERT2;R26R^tdTomato mice were used and the adult one month or longer influenza experiments in Figures 5C–5I,6B, and 6D–6I where Sftpc^CreERT2;R26R^EYFP mice, including littermates, were used. Experiments were all performed with a minimum of n = 3 mice per condition of mixed gender, and unless otherwise stated each dot on a graph represents one mouse. All procedures for animal experiments were performed under the guidance of the University of Pennsylvania Institutional Animal Care and Use Committee.