A construct containing the Scre gene driven by the CAG promoter was inserted into the intron of the Gt(ROSA)26Sor locus via homologous recombination in Wit 9 ES cells. SCre/SloxP is a site-specific recombination system that was derived from plasmid 1 of Shewanella sp. ANA-3. SCre is a recombinase that recognizes its own specific target sites (SloxP).