The transgene is comprised of an 8.0 kb genomic fragment comprising the sequences between 5.6 kb upstream of the Olfr73 start codon, and the PvuII site in the 3 untranslated region. A SacII-NotI site was engineered downstream of the Olfr73 stop codon, into which a IRES-gapEGFP was inserted, which encodes an internal ribosome entry site (IRES) and a fusion protein consisting of the N-terminal 20 amino acids of Gap43 and EGFP. Three lines of mice expressing the transgene in different patterns were generated, TgA, TgB and TgC. (J:117260)