An EGFP/icre sequence was inserted into exon 1, replacing the endogenous ATG with the translational start site of the EGFP/icre, yet preserving the last 10 bp of the splice-donor site of exon 1. A FRT flanked neo was inserted downstream to replace parts of exon 2 and exons 3-8. Transient FLP expression excised the neo. Southern blot and multiplex PCR confirmed recombination in heterozygous mice. Immunoblot of FLCs demonstrated green fluorescence in heterozygous and homozygous embryos, with homozygotes showing a 2-fold increase in fluorescence intensity compared to heterozygotes. (J:92235)