The targeting vector is designed with (from 5' to 3') a ubiquitously expressed CAG (CMV enhancer/chicken beta-actin) promoter, a floxed STOP cassette (containing polyadenylation [pA] sites), CreV, a woodchuck hepatitis virus post-transcriptional regulatory element (WPRE; to enhance the mRNA transcript stability), a BGH polyA, an attB site, a PGK-Neo cassette with a PGK poly(A), and an attP site. CreV consists of a split, light-inducible Cre, with the N-terminal CreV (NCreV) and C-terminal CreV (CCreV) protein sequences separated by an internal ribosome entry site. PhiC31o-mediated recombination removed the neo cassette. (J:101977)