Recombinase mediated cassette exchange (RMCE) replaced the fragment between FRT and the third loxP which contained lacZ , neomycin and exon 2 sequences located in intron 1 of the Gdf15 allele with the following - an FRT site, En2 splice acceptor, P2A, nuclear GFP, F2A, cre/ERT2, polyA and a rox-flanked puromycin resistance cassette followed by a loxP site. (J:101977, J:294071)