Genetic Lineage Tracing of Gastroesophageal Tissues

All animal procedures were approved by the national legal and institutional authorities (Landesamt fur Gesundheit and Soziales (LaGaSo), Berlin, Germany, G 0026/17) at the Max Planck Institute for Infection Biology, Berlin, Germany. Wild-type C57BL/6 female mice were from Jackson Laboratory. Krt5-CreERT2; Rosa26-tdTomato and Krt8-CreERT2; Rosa26-tdTomato strains were generated as described in^{14 (link)}. Axin2CreERT2^{77 (link)} mice were bred to Rosa-tdTomato mice^{78 (link)} to generate Axin2-CreERT2; Rosa26-tdTomato mice. Cre was induced by administering tamoxifen (Sigma, T5648) intraperitoneally (0.25 mg/g body weight in 50 μl corn oil) (Sigma, C8267) at week 4 for two consecutive days. Mice were euthanized at 14–20 weeks, and the gastroesophageal tissue was removed for further analysis. The stomach isolated from the postnatal mice or embryonic days 13, 16, and 19 were used for organoid culture or fixed with 4% PFA (Sigma, 441244) for 1 h at RT. Experiments were performed in at least three biological replicates per condition. The animals were housed in autoclaved micro-isolator cages, where they had access to sterile drinking water and chow ad libitum. Mice were bred within the animal care facility, maintaining a 12 h light/12 h dark cycle, and ensuring a controlled environment with a temperature of 22.5 ± 2.5 °C and humidity at 50 ± 5%.