Differential gene expression in mummichogs (Fundulus heteroclitus) following treatment with pyrene: comparison to a creosote contaminated site

Mummichogs, Fundulus heteroclitus, an estuarine fish with a relatively small home range found along the eastern coast of the United States are well-suited to monitoring contaminant effects, including those of polycyclic aromatic hydrocarbons (PAHs). One of the common PAHs in estruaries is pyrene. We report here on efforts to develop multiple biomarkers of pyrene exposure in this species. Adult male mummichogs were exposed in the laboratory to the weak aryl hydrocarbon receptor (AhR) agonist pyrene at 0, 30, or 50 μg/L in 7-day static renewal exposures. The RNA was extracted from livers and alterations in mRNA expression were assessed by subtractive hybridization and differential display in order to produce multiple biomarkers of pyrene exposure. Genes demonstrating differential expression were confirmed by quantitative-PCR (Q-PCR) and include cytochrome P-450 1A (CYP1A), a putative hepatocyte growth factor activator, a X-ray inducible retrotransposon, and several expressed sequenced tags (ESTs). Some of these genes represent new biomarkers of pyrene exposure and potential biomarkers of PAH exposure. Therefore, similar changes were investigated at a Superfund site in Charleston, SC. Mummichogs from a creosote contaminated site and from a reference site (North Inlet National Estuarine Research Reserve near Georgetown, SC) were trapped, RNA extracted from the livers, and Q-PCR performed. Many of the genes differentially expressed following pyrene exposure were not altered at the creosote contaminated site in comparison to the reference site. However, CYP1A and an EST were induced. CYP1A induction at Diesel Creek indicates that this population of fish does not demonstrate refractory CYP1A phenotypes observed at several sites with high levels of AhR agonists. Ultimately, we anticipate that the use of multiple biomarkers of PAH exposure will provide useful information on the potential effects of toxicants.