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Vitellogenin Gene Expression in Male Fathead Minnow as an Indicator of Exposure to Endocrine Disrupting Chemicals (EDCs) in an Aquatic Environment
Objective:
To develop molecular tools for monitoring fish exposures to EDCs implicated in feminization of male fish around the world and in USA, that are present in surface waters, effluents from sewage treatment plants and sediments.
Approach:
In recent years feminization of male fish has been detected in Europe, UK, Japan, and USA. This response in male fish has been linked to their exposure to female hormones such as 17-?-estradiol and estrone, the synthetic hormone 17?-ethynylestradiol and chemicals that mimic estrogens (e.g., nonylphenols, octylphenols and their ethoxilates) that are present in an aquatic environment. It is believed that the majority of these EDCs reach aquatic environments via effluents of sewage treatment plants. Vitellogenin (Vg) is an egg yolk precursor protein expressed only in female fish and is normally dormant in male fish. However, when male fish are exposed to estrogenic EDCs the Vg gene is expressed in a dose dependent manner. Hence, Vg gene expression in male fish has been used as a molecular marker of exposure to estrogenic EDCs.- Vg gene expression is quantitated by reverse transcription quantitative polymerase chain reaction (RT-QPCR). We are conducting exposure monitoring studies by caging male fathead minnow in environmental waters and sampling at different time points.
- We are collecting stream, sediment and effluent samples and shipping them back to our laboratory for exposures with male fathead minnows or fry for 24 or 48 hours.
- After these exposures we determine the level of Vg gene transcription in fathead minnow using standardized real-time QPCR methods. The estrogenic potency (estrogenic equivalents) of these exposures can be estimated by comparing male fish exposed in the laboratory with known concentrations of 17-?-estradiol or 17?-ethynylestradiol as positive control.
Why This Research Is Needed:
This research will provide data to determine concentrations of bio-available EDCs (e.g., natural estrogenic hormones, synthetic estrogenic hormones, nonylphenols and their ethoxilates) present in effluents, stream, lake, and in sediments. This in turn helps State and local Government agencies to assess sewage treatment plant efficacies in removing EDCs and potential impacts to receiving waters.
EERD Experience:
Currently, EERD/NERL/Cincinnati is focused in screening surface waters, effluents from sewage treatment plants and sediment elutriates for the bio-availability of estrogen EDCs using Vg gene expression as an indicator of exposure in fathead minnows.
Expected Outputs/Outcomes:
Regions, States, Tribes and risk assessors will possess easily manipulated tools to quantify estrogenicity present in the Nation's aquatic ecosystems and drinking water.
Partners: EERD/NERL-Cincinnati, NRMRL-Cincinnati, Regions, States
Contact: T.V. Reddy (reddy.tirumuru@epa.gov) | James Lazorchak (lazorchak.jim@epa.gov) | David Lattier (lattier.david@epa.gov) (Cincinnati, OH)