Identification of novel cytochrome P450 1A genes from five marine mammal species

Marine mammals, being endangered by the chronic exposure of hydrophobic env ironmental contaminants as an asserting result of global pollution, are esp ecially focused as indicators for organochlorine pollution. The use of cont aminant-induced xenobiotic metabolizers, particularly P450 (CYP) 1A, in mar ine mammals can be effective as potential biomarkers of the contaminant exp osure and/or toxic effects. In this study, we identified the first marine m ammalian CYPs. Six novel CYP1A cDNA fragments were cloned from the livers o f marine mammal species, minke whale (Balaenoptera acutorostrata), dall's p orpoise (Phocoenoides dalli), steller sea lion (Eumetopias jubatus), largha seal (Phoca largha), and ribbon seal (Phoca fasciata) by the method of rev erse transcription/polymerase chain reaction (RT/PCR); two distinct fragmen ts were from steller sea lion and one fragment each was obtained from the o ther species. Five of the fragments, one from each species, were classified in the subfamily of CYP1A1, and the other fragment cloned from steller sea lion was designated CYP1A2. Degenerate PCR primers were used to amplify th e fragments from liver cDNAs. The deduced amino acid sequences of these fra gment CYP1As showed identities ranging from 50.0 to 94.3% with other known vertebrate CYPs in the subfamily of CYP1A, including those from fish, chick en, and terrestrial mammals. The isolated fragments were used to construct a molecular phylogeny, along with other vertebrate CYP1A cDNAs cut down in size to the corresponding region of 265 bp in which those newly determined fragments were cloned. This phylogenetic analysis by the maximum parsimony method using the PHYLIP program suggests two distinct evolutional pathways for aquatic mammalian CYP1As, compatible to a conservative taxonomy. Pinnip ed genes are clustered together with dog gene, forming a carnivore group, a nd cetaceans form another branch. Identification of CYP1A genes in marine m ammals will be an introductory step to provide new insights into the metabo lic or toxicological functions of CYP1As in these animals. (C) 2000 Elsevie r Science B.V. All rights reserved.