An EGFP-IRES-creERT2 cassette was inserted into exon 1 of the gene along with a loxP-flanked neomycin cassette. The neomycin gene was then excised in vivo by crossing with cre-deleter strain. GFP expression is driven by the endogenous promoter. Cre expression is induced in Lgr5 expressing cells by tamoxifen treatment. (J:127123)