The targeting vector is designed with (from 5' to 3') a ubiquitously expressed CMV-IE enhancer/chicken beta-actin/rabbit beta-globin hybrid promoter (from pCAGGS), loxP-flanked stop cassette, murine lymphoid enhancer binding factor 1 (Lef1) cDNA, a membrane bound T2-Green Fluorescent Protein (T2-mGFP), and a neomycin resistance (neo) cassette inserted into the Gt(ROSA)26Sor locus. (J:101977)