R26r lacz mice

Pax7-CreER^tm males (85 (link)) (herein referred to as Pax7^CreER) were crossed to R26R^YFP/YFP females (The Jackson Laboratory, no. 006148) to obtain Pax7^CreER/WT; R26R^YFP/WT males. These breeders were crossed with mdx^5Cv/5Cv or WT female (both in the C57BL6 background, The Jackson Laboratory) to obtain the male experimental animals. TMX (Sigma) was dissolved at 50 mg/ml in 92.5% corn oil/7.5% ethanol, and 5 mg was administrated intraperitoneally to 5-week-old experimental mice twice a week for 2 weeks. For specific experiments, R26R^LacZ mice were used (The Jackson Laboratory, no. 003474). BAT-GAL mice (The Jackson Laboratory, no. 005317) are engineered with copies of the Wnt-inducible TCF/LEF–responsive element driving the expression of β-Gal. Geno-typing was performed with primers listed in table S2.
In chronic studies, mdx5^Cv mice were injected with 300 ng of anti-TGFβ (1D11) or anti-Shigella toxin (control) antibodies on alternate days for 6 months (36 (link)). Purified antibodies were provided by Genzyme (37 (link)). Losartan was administrated for 7 months (0.6 g/liter in drinking water) (35 (link)). Treatments were started at 5 weeks of age. Experiments were done in accordance with protocols approved by the Institutional Animal Care and Use Committee at the Veterinary Medical Unit at the VA Palo Alto Health Care System.

The animal protocol was reviewed and approved by the Columbia University Medical Center Institutional Animal Care and Use Committee (IACUC), and all mice were bred under specific pathogen free (SPF) conditions. INS-GAS mice^{27 (link)} and hGAS mice^{23 (link)} were backcrossed to C57BL6 background. Lgr5-GFP-IRES-CreER knockin mice^{28 (link)} (Lgr5-GFP mice) were provided by Dr Hans Clevers, and mated with hGAS mice and B6.129S4-Gt(ROSA)26Sortm1Sor5/J, referred to as R26rLacZ mice (Jackson Laboratories). CCK2R^−/− mice were purchased from Jackson Laboratories. CCK2R-GFP BAC transgenic mice were purchased from MMRRC (GENSAT project^{29 (link)}). For generation of CCK2R-BAC-CreERT mice, BAC recombination was carried out as described at http://web.ncifcrf.gov/research/brb/recombineeringInformation.aspx using the CreTM-FrtNeoFrt cassette as described previously.^{30 (link)} For lineage tracing experiments, mice were administered 1–6 mg tamoxifen in 200 μL corn oil containing 5–30 mg/mL tamoxifen by oral gavage. The CCK2R antagonist YF476 was a kind gift of Dr Keiji Miyata and Dr Hidenobu Yuki (Astellas Pharma, Tokyo, Japan). The drug was dissolved in PEG 300 at the concentration of 12 mg/mL and intraperitoneally injected twice per week at the dose of 40 mg/kg.^{31 (link)}