Genes express dissatisfaction with environment. (Risk Assessment).

In an even newer use for a hot new biotech tool, environmental scientists are using gene expression signatures to monitor, chart, and predict how common toxicants affect the genes of animals living in polluted ecosystems. In gene expression signatures, the activity of genes is analyzed to determine how contaminants change their function. Developmental neurobiologist Charles Ide, director of the Environmental Institute at Western Michigan University in Kalamazoo, and neuroscientist Anna Jelaso, an assistant professor also at that institute, have used such signatures to show that tadpoles exposed to polychlorinated biphenyls (PCBs) undergo changes in gene expression that predict impending health problems.

The tadpoles were exposed to Aroclor 1254, a PCB mixture once used by the electrical power industry, at levels reflecting PCB concentrations contaminating sediments and animal tissues in the Kalamazoo River and other waterways. The scientists then measured expression of several key genes involved in neurologic function, apoptosis, endocrine function, cell cycle regulation, cell structure, and metabolism.

They found that tadpoles exposed to the highest concentration of Aroclor 1254 quickly developed symptoms of toxicity, and the majority died. In addition, the activity of most of the analyzed genes dropped significantly. Tadpoles exposed to the lowest concentration of Aroclor 1254 showed similar but less severe drops in gene expression, and no obvious health abnormalities. However, with prolonged exposure even to low doses of Aroclor 1254, adverse health effects and death occurred. The findings will be published in an upcoming issue of Environmental and Molecular Mutagenesis.

This proof-of-concept experiment shows that changes in gene expression correlate with health effects, says Ide, and may indicate impending health effects long before damage becomes apparent. The method appears applicable to fish, birds, and other creatures living in polluted ecosystems.

The current system for monitoring the risk of PCB damage involves collecting water, sediment, and biologic tissue samples, analyzing them for PCBs, then using risk numbers derived from the scientific literature on species that may not even live in the ecosystem under study. "It's better to make decisions using data on species actually exposed in a given environment," says Brian von Gunten, a biologist and Superfund site manager for the Michigan Department of Environmental Quality in Lansing. He foresees the technology being useful for pinpointing areas where PCBs are especially bioavailable, prioritizing areas to be cleaned up, and monitoring the recovery of the ecosystem over time, with less need for collecting species from an ecosystem that has already been devastated by pollution.

Gene expression signatures are predicted to revolutionize human health as well. "This is what medicine will be in ten years," says Ide, and "we're applying the same technology to ecosystem health."