The eGFP-CreERT2 (GCE) fragment with an SV40 poly adenylation site and neomycin resistance cassette were inserted immediately downstream of the translational initiation codon ATG. The knock-in construct removed the coding sequences from exon 1 and placed the GCE gene under the control of the endogenous regulatory sequences. Flp-mediated recombination removed the selection cassette. The EGFP could not be detected by direct fluorescence or anti-GFP antibody staining. (J:229520)