The modified BAC (which has a GFP gene inserted at the ATG of Fezf2) used in the Tg(Fezf2-EGFP)CO61Gsat allele was further modified by replacing Fezf2 non-exonic enhancer 4 (E4; Rr19), downstream of the gene, with an FRT site flanked neomycin resistance gene cassette. The neo cassette was removed through subsequent flp-mediated recombination. (J:186632)