Salmon eggshell protein expression: A marker for environmental estrogens

A liver complementary DNA expression library from Atlantic salmon (Salmo sa lar) pretreated with estradiol-17 beta (E-2) was constructed and screened w ith antibodies raised against salmon eggshell (zona radiata) proteins. Two clones, SalZr2_19 and SalZr2_23 were sequenced and shown to encode proteins of approximately 50 kDa. SalZr2_23 contains 12 octamer Sequence LPQR/KPA/V Q repeats also found in SalZr2_19, but only twice. Alignment reveals that t he two salmon sequences are similar to piscine zona radiate proteins and ma mmalian zona pellucida proteins. Several transcripts ranging from 2.3 to 12 kb appeared in liver extracts of E-2-treated fish. Juvenile fish treated w ith E-2 or 4-nonylphenol showed strong induction of zona radiata protein. T he use of egg envelope transcriptional and translational induction in male or juvenile fish as a biological marker of environmental estrogens is discu ssed.