The targeting vector used for homologous recombination was generated by BAC recombineering. A tamoxifen-inducible cre (cre/ERT2) sequence, SV40 polyA signal, and an Frt-flanked PGK-neo cassette were targeted to the endogenous ATG site of Lrig1. Chimeras were crossed with Flpe-expressing animals to remove the neo from the germline. (J:186084)