2.1. Animals

C57BL/6J mice (Stock #000664) and Shh^{tm2(cre/ERT2)Cjt}/J mice (Stock #005623) (Harfe et al., 2004) were purchased from Jackson Laboratory (Bar Harbor, ME). Ctnnb1^{tm1Mmt/tm1Mmt} mice (Harada et al., 1999) were from Makoto Mark Taketo (Kyoto University, Japan). Mice were housed in polysulfone cages containing corn cob bedding and maintained on a 12 h light and dark cycle at 25±5 °C and 20–50% relative humidity. Feed (Diet 2019 for males and Diet 7002 for pregnant females, Harlan Teklad, Madison, WI, USA) and water were available ad libitum. All procedures were approved by the University of Wisconsin Animal Care and Use Committee and conducted in accordance with the NIH Guide for the Care and Use of Laboratory Animals. To obtain timed-pregnant dams, females were paired overnight with males and the next morning was considered 0 days post coitus (dpc). Mice harboring the dominant stable Ctnnb1 gain-of-function (iGOF) allele in UGS epithelium (Shh^creERT2/+; Ctnnb1 ^{tm1Mmt/tm1Mmt}) and genotypic control mice (Shh^+/+; Ctnnb1^{tm1Mmt/tm1Mmt}) were generated as described previously (Mehta et al., 2013). Dams were euthanized by CO₂ asphyxiation for embryo collection.