The cDNA encoding a fusion of an EGFP protein with the L10 (large subunit ribosomal protein L10) was inserted into a vector downstream of a floxed 'STOP' cassette and a neomycin selection marker and upstream of a polyadenylation signal. Homologous recombination in ES cells inserted this sequence into the first intron of Eef1a1. Cre-mediated recombination of this allele results in expression of the EGFPL10 protein. (J:206002)