Mammalian genes expressed in Drosophila: a transgenic model for the study of mechanisms of chemical mutagenesis and metabolism.

Mammalian cytochrome P450s provide our first line of defence against the toxic effects of environmental chemicals. Ironically these enzymes also convert some compounds to their ultimate toxic or mutagenic species. Our knowledge of these mammalian enzymes and the role they play in chemical toxicity and mutagenesis has stemmed mostly from in vitro studies. In order to establish the role of specific enzymes in the toxicological response in vivo we have generated transgenic Drosophila which express mammalian cytochrome CYP2B1, which is a member of a large gene family encoding several important drug metabolising enzymes. The gene was fused to a Drosophila promoter which confers expression in the larval fat body. Using the Somatic Mutation And Recombination Test (SMART) we have demonstrated that transgenic larvae expressing the P450 are hypersensitive to the anticancer drug cyclophosphamide, a procarcinogenic substrate which is activated by the enzyme. This work demonstrates the potential of such transgenic Drosophila strains as an in vivo model for studying the role of specific mammalian drug metabolising enzymes in the pathways and metabolic cascades associated with the action of cytotoxic and carcinogenic chemicals, and also the chemical properties of specific classes of mutagen to be determined.