Biomarkers are an important tool used by toxicologists and environmental scientists, to study environmental exposures of plants and animals to potentially toxic compounds. Many of the methods for studying gene expression and enzyme activity, attributed to biotech and biomedical research, are also applicable to environmental studies. I am privileged to be able to attend the SETAC North America conference in New Orleans (LA) this week. While on the lookout for new information on ecological risk assessments, I've also come across a number of examples of how genetic methods are being applied to bioindicator discovery.
In one example, quantitative reverse-transcriptase (RT) PCR was used to study Vitellogenin (Vg) gene expression in male fathead minnows exposed to estrogenic substances. Vg is an egg-yolk precursor protein usually only expressed in female fish. The gene is dormant in males, but is expressed when they have been exposed to estrogenic compounds (chemicals that mimic the effects of the hormone estrogen). Reddy et al., of the US EPA, purified total RNA from the minnows and subjected the samples to reverse transcription using a retrovirus reverse transcriptase enzyme, producing cDNA, which was then quantified by PCR. Vg gene expression was altered at concentrations below routine laboratory detection limits, for three of the four compounds tested. Therefore, measurements of Vg might provide a good biomarker of exposure to estrogenic compounds, where chemical analysis is not sensitive enough.
Source: Reddy, TV et al. Induction of vitellogenin gene expression in adult male fathead minnows for select estrogens in 48-hr continuous addition and daily renewal exposures. Presented at SETAC NA, New Orleans, Nov. 2009.