Gt(ROSA)26Sor^{tm2(CAG-Dsred2/EGFP)Luo}

A construct containing the CMV beta-actin enhancer/promoter, SV40 poly(A) signal, and encoding the N-terminal part of Dsred2 (red fluorescent protein) and C-terminal part of EGFP which are separated by a beta-globin intron containing a loxP-flanked neomycin resistance gene, was knocked into ES cells at the ROSA26 locus. No protein is expressed from the chimeric locus in absence of Cre-mediated recombination because the coding sequences are interrupted by the intron in different reading frames. After recombination with the reciprocal mutation at the same locus carried by another mouse line, which restores the reading frames of EGFP and RFP, RNA splicing will remove the remaining single loxP sites, resulting in functional protein expression. (J:98961)