REGULATION OF THE CYP1A1 PROMOTER IN TRANSGENIC MICE - AN EXQUISITELYSENSITIVE ON-OFF SYSTEM FOR CELL-SPECIFIC GENE-REGULATION

Mammalian cytochrome P-450s in the CYP1A gene family catalyse the oxid ation of a wide range of drugs and foreign compounds resulting in thei r excretion, These enzymes are highly inducible by a range of compound s, including polycyclic aromatic hydrocarbons such as 3-methylcholanth rene (3-MC) and dioxins, Analysis of the CYP1A1 promoter has identifie d dioxin responsive enhancer elements which mediate the induction resp onse, In order to evaluate this promoter as an in vivo regulatable exp ression system and to gain further insights into the tissue specific r egulation of this gene, an 8.5 kb genomic fragment of the rat CYP1A1 p romoter was cloned upstream of the lacZ reporter gene, This construct was used to generate transgenic mice and three independent lines were expanded for further study, The regulation of beta-galactosidase expre ssion was determined in mock and 3-MC-treated mice in an extensive ran ge of tissues, In untreated animals no transgene expression was detect able over non-transgenic controls. Treatment with 3-MC caused a profou nd increase in transgene expression (>1,000-fold) in many tissues incl uding liver, adrenal, kidney and intestine, Inducible transgene expres sion was also detectable in many of the other tissues including the sp leen, lung, pancreas and the reproductive organs, Although the absolut e levels of induction varied, no significant differences in the patter n of transgene expression were observed between the three different tr ansgenic mouse lines, In addition, the pattern of transgene expression correlated closely with the reported regulation of CYP1A1 protein, Th ese results indicate that the CYP1A1 promoter can drive expression of heterologous genes in a truly on/off manner in a variety of tissues an d cell types which will allow the expression of other proteins to be c ontrolled in vivo. This reporter system also provides a model for esta blishing the environmental and hormonal factors regulating the express ion of the CYP1A1 gene.