A targeting vector was designed with a GFP fused to the ATG in exon 2 by a 5-amino acid linker, GGSGG. A PGK neo was included in intron 2 and was subsequently removed by crossing with Tg(EIIa-cre)C5379Lmgd mice. Western blot of heterozygotes demonstrated that expression of the GFP-GR fusion protein is equal to that of the endogenous protein. (J:98328)