A targeting construct was designed to replace exon 1 of the Il22 (interleukin 22) gene with a 6 aa linker sequence, a codon improved Cre Recombinase gene (iCre) followed by an SV40 polyadenylation sequence and a FRT-flanked neomycin resistance (neo) cassette. Flp-mediated recombination removed the FRT-flanked neo cassette. (J:220074)