A targeting vector was designed to replace the stop codon of the endogenous keratin 17 (Krt17) gene with (from 5' to 3') a viral 2A oligopeptide (to mediate ribosomal skipping), cre recombinase, another 2A oligopeptide, the cerulean variant of green fluorescent protein (GFP), and a bovine polyadenylation sequence. This sequence was followed by a frt-flanked neomycin (neo) resistance cassette. This construct was electroporated into C57BL/6NTac derived JM8A3 embryonic stem (ES) cells. (J:187143)