A targeting vector was created with a CMV enhancer/chicken beta-actin core promoter (pCA) upstream of the "MADM TG" cassette. The "MADM TG" cassette used here (ATG-intron-GFPC-terminus) was designed with an ATG start codon, a beta-globin intronic sequence (containing a frt-flanked region of two lox site variants [lox2272 and lox5171] and then a loxP-flanked neomycin resistance gene), the C-terminal portion of a mutant enhanced green fluorescent protein (mut4EGFP second exon; nucleotides 275-735 including stop codon), and an SV40 T-antigen poly(A) signal. This entire construct was subcloned into the pROSA26-PA targeting vector to generate the final targeting construct pROSA26-TG. The pROSA26-TG construct was inserted into the Gt(ROSA)26Sor locus. (J:181830)