The COIN module (L71 loxP site, inverted polyadenylation sequence, inverted EGFP, L66 loxP site and FRT-flanked neo cassette) was inserted after the thirtieth nucleotide of the coding exon. This insertion divides the CpG island. Flp-mediated recombination removed the neo cassette. Cre-mediated recombination restored the orientation of the EGFP to allow for expression. Western blot analysis confirmed a reduction in protein expression in heterozygous samples. (J:191980)