Salmon Eggshell Protein Expression: A Marker for Environmental Estrogens

Area of Science:

• * Molecular biology
• * Endocrinology
• * Environmental toxicology

Background:

• * Estradiol-17beta (E2) is a key estrogen influencing reproductive processes in fish.
• * Zona radiata proteins (ZRPs) are crucial components of the egg envelope in vertebrates.
• * Environmental estrogens can disrupt endocrine systems in aquatic organisms.

Purpose of the Study:

• * To identify and characterize salmon zona radiata proteins (SZRPs) induced by estradiol-17beta (E2).
• * To investigate the potential of SZRP gene expression as a biomarker for environmental estrogens.
• * To compare salmon ZRPs with their mammalian counterparts.

Main Methods:

• * Construction and screening of a liver complementary DNA (cDNA) expression library from E2-pretreated Atlantic salmon (Salmo salar).
• * Sequencing and analysis of selected cDNA clones (SalZr2_19 and SalZr2_23).
• * Analysis of liver extracts and gene expression in juvenile fish treated with E2 or 4-nonylphenol.

Main Results:

• * Two cDNA clones, SalZr2_19 and SalZr2_23, encoding approximately 50 kDa proteins were identified.
• * These clones contain repetitive sequences and show similarity to piscine and mammalian zona proteins.
• * E2 treatment induced multiple transcripts (2.3–12 kb) in liver, and juvenile fish exposed to E2 or 4-nonylphenol exhibited strong SZRP induction.

Conclusions:

• * Novel salmon zona radiata proteins have been identified and characterized.
• * The transcriptional and translational induction of SZRPs in juvenile or male fish can serve as a sensitive biomarker for environmental estrogens.
• * This finding has implications for monitoring endocrine disruption in aquatic environments.