Npy^{tm1(rtTA,tetO-cre/EGFP)Snby}

The coding exons of the Npy gene were replaced with a cassette consisting of the reverse tetracycline transactivator (rtTA) gene, the EGFP gene in the opposite orientation, a neo selection cassette and cre recombinase controlled by the tetracycline responsive element (TRE; tetO), also in the opposite orientation to the Npy promoter. The stop codon of cre and the ATG initiation codon of EGFP were engineered to contain loxP sites in the same orientation so that cre mediated excision of the floxed region (including neo) would result in production of a cre/EGFP fusion product. Treatment with doxycycline activates the rtTA gene product, allowing transcription of the adjoining gene, which in turn excises the floxed segment. (J:162000)