The transgenic construct contained a bidirectional tTA/rtTA responsive promoter derived from the human cytomegalovirus promoter IE and flanked by sequence encoding luciferase and cre recombinase. Efficient cre mediated recombination, unaffected by position effect variegation, was demonstrated in hepatocytes. Transcription of in both directions was shown to be activated by rtTA in the presence of doxycycline. Transgene insertion is on chromosome 6C1 flanked by genes coding for the
vomeronasal receptors V1rc14 and V1rc15 (K.Schonig, pers. commun.)