Grantee Research Project Results
Differential Gene Expression in Fundulus heteroclitus Due to the Environmental Metal, Hexavalent ChromiumEPA Grant Number: U916207
Title: Differential Gene Expression in Fundulus heteroclitus Due to the Environmental Metal, Hexavalent Chromium
Investigators: Roling, Jonathan A.
Institution: University of Texas at El Paso
EPA Project Officer: Just, Theodore J.
Project Period: January 1, 2003 through January 1, 2006
Project Amount: $88,436
RFA: Minority Academic Institutions (MAI) Fellowships for Graduate Environmental Study (2003)
Research Category: Ecological Indicators/Assessment/Restoration , Academic Fellowships , Fellowship - Environmental Science
Changes in gene expression are useful biomarkers that can provide information about the health of an organism, its ability to adapt to its surroundings, and specific pathways or effects of toxicants. Furthermore, gene expression can be used to monitor an organism's exposure to a toxicant, provide an early warning that an ecosystem is exposed to harmful chemicals, or indicate whether remediation of a polluted area is successful. The objective of this research project is to build a microarray to be used as a reliable biomarker of exposure and effect for hexavalent chromium in the abundant estuarine minnow, Fundulus heteroclitus. The long-term objective is to create an array that can be used to indicate potential exposure effects of chromium (and in the future, other chemicals) to Fundulus to monitor the health and recovery of our nation's estuaries.Approach:
Chromium is discharged during steel production, and it is the dominant toxicant found at several metal-contaminated estuarine Superfund sites around the United States, including Shipyard Creek in Charleston, SC, and Seavey Island in Kittery, ME. Laboratory experiments will be performed to determine differential gene expression caused by only hexavalent chromium. First, 1-month growth studies will be performed with juveniles according to U.S. Environmental Protection Agency protocols, and a no-observed-effect concentration (NOEC) and a lowest observed-effect concentration (LOEC) will be determined. Adults then will be exposed to Cr(VI) for 7 days at the NOEC, the LOEC, and an environmentally relevant level. Preliminary experiments indicate that adults probably will be exposed to 100, 300, and 600 µg/L Cr(VI) as CrO3. Subtractive hybridization will be performed between controls and each of the three groups to isolate sequences differentially expressed by Cr(VI). Fundulus will be collected at Shipyard Creek and North Inlet (a reference site), and subtractive hybridization will be performed to determine changes in gene expression at the Superfund site. Significant differences may occur because of genetic variation or chronic acclimation compared to 7 days of laboratory exposure; therefore, North Inlet Fundulus will be transported to Shipyard Creek for 7-day cage studies, and subtractive hybridization will be performed. This experiment should help bridge the gap between field studies and laboratory studies. The differentially expressed sequences isolated during the subtractive hybridization from the caged studies, the field studies, and the laboratory studies will be used to create a microarray. The microarray will be used to confirm differential expression in the laboratory and then will be used in the field and cage studies to determine whether similar genes are altered in these studies as in the laboratory studies. Furthermore, I hope to correlate changes in gene expression to exposure levels and body burdens of Cr(VI) in the field-caught and laboratory-exposed Fundulus. By identifying epigenetic responses in F. heteroclitus caused by Cr(VI), monitoring estuarine systems for bioavailable toxicant can be assessed without tedious analytical procedures that do not reflect bioavailability or valency.Supplemental Keywords:
fellowship, Fundulus heteroclitus, differential gene expression, chromium, biomarkers, estuarine systems, toxicants, microarray, metal-contaminated estuarine sites, bioavailability.