A targeting vector was designed with a splice acceptor site followed by a loxP-flanked neomycin resistance cassette fused to a polyadenylation signal. This was followed by (from 5' to 3') an FRT site, a FLAG-tagged mouse cDNA, and an internal ribosome entry site (IRES) fused to a nuclear localization signal and an mCherry sequence, and a second FRT site. (J:239441)