C57bl 6 tg actb egfp 1osb j

Wild-type mice (C57BL/6, Charles River Laboratories, Wilmington, MA) or mice expressing green fluorescent protein (GFP, C57BL/6-Tg(Actb-EGFP)1Osb/J, Jackson Laboratory, Bar Harbor, ME) were used in the study. Intestinal muscularis was isolated from 3 to 7-day-old mice. Intestinal crypts were isolated from 6-week-old mice. All animal studies were approved by Animal Research Committee and Office of Animal Research Oversight at University of California Los Angeles (UCLA) as protocol number 2005–169 or by Stanford University Institutional Animal Care and Use Committee A3213-01. All efforts were made to minimize animal pain and suffering. For human studies, de-identified healthy small intestine tissues from discarded surgical samples of infant, teenager or adult patients were obtained through the Department of Pathology Translational Pathology Core Laboratory at UCLA. Fourteen to 18-week-old fetal bowels were obtained upon the written informed consent from each patient. All human studies were approved by UCLA Institutional Review Board.

C57BL/6 Rac2^−/− mice were provided by Dr. Durden (Moores Cancer Center, University of California, San Diego) and C57BL/6 Ctns^−/− mice were provided by Dr. Antignac (Inserm U983, Paris, France). Enhanced green fluorescent protein (eGFP; C57BL/6-Tg(ACTB-EGFP)1Osb/j) and DsRed (B6.Cg-Tg(CAG-DsRed*MST)1Nagy/J) transgenic mice were purchased from The Jackson Laboratory (Bar Harbor, ME). Ctns^−/− mice were cross-bred to both DsRed and GFP to produce Ctns^−/− strains constitutively expressing either DsRed or GFP reporter genes as previously described^{14 (link),16 (link)}. All strains and mouse procedures were approved by the University of California, San Diego (UCSD) in accordance with the guidelines set forth by the Institutional Animal Care and Use Committee (Protocol ID S12288).