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Harnessing the HGP for Public Health.

The enormous amount of genetic data from the Human Genome Project (HGP) has benefited researchers studying gene-environment interactions, but also presents challenges in experimental design, data management, and the ethical, legal, and social implications of gene-environment research. These challenges were the topic of the symposium "The Human Genome Project and Public Health: Gene-Environment Interactions," part of the 2004 annual meeting of the American Association for the Advancement of Science in Seattle, Washington.

Presenters discussed strategies in help researchers decide where in concentrate their research dollars and energy among the more than 7.2 million genetic variations and single-nucleotide polymorphisms (SNPs) cataloged by the HGP. One strategy is to focus on genes that are linked by function in pathways, said Deborah Nickerson, a professor in the University of Washington (UW) Department of Genome Sciences. She discussed progress on SNP discovery in gene pathways for the Environmental Genome Project, especially the development of new algorithms to explore associations between SNPs in human genes and environmental exposures. One program--Hotspotter, developed by UW assistant statistics professor Matthew Stephens--helps researchers explore recombination in human genes over time, a history that affects SNP associations in the human genome.

Focusing on genes involved in key cellular processes such as DNA repair is critical, according to symposium co-organizer David Eaton, director of the NIEHS-UW Center for Ecogenetics and Environmental Health, Every day, each cell in the human body withstands 10,000-20,000 oxidative assaults to DNA, and the vast majority are repaired. Increased understanding of how this DNA repair happens and other critical biochemical pathways can lead to better methods for disease prevention and more effective drugs with fewer side effects, said Eaton.

Better understanding of gene-environment interactions can also lead to more accurate dosing of existing medications. This is especially crucial for powerful drugs where the margin between effective and toxic doses is narrow, said Kenneth Thummel, associate dean for research and new initiatives of the UW School of Pharmacy. One example is warfarin, an anti-coagulant used to prevent recurrent myocardial infarction and other thromboembolic events. Variations in a single gene (CYP2C9) can cause some people to be five times as sensitive to the drug and make them susceptible to overdosing, which can cause severe internal bleeding. According to Thummel, genetic testing could be cost-effective if it could replace some of the blood tests now used to monitor warfarin dosing--especially if it reduces hospitalizations by determining which patients need lower doses of the drug and closer monitoring. Other recent research may lead to improved dosing for the immunosuppressants cyclosporine and tactolimus, which can cause kidney damage and failure.

Susceptibility to heart disease has also been linked to numerous genes, including APOE. Steve Humphries, a professor of cardiovascular genetics at University College London Medical School, reported that variants of APOE are well known to raise or lower blood levels of low-density lipoprotein ("bad") cholesterol, but only have a significant impact on an individual's risk of heart disease when the person smokes. Smoking increases the risk of heart disease of people with any of three common APOE variants, but the risk is greatest (about threefold) among carriers of the [epsilon] 4 variant, which is found in about 25% of the population. Humphries and colleagues are working with a smoking cessation clinic in London to determine whether smokers will be motivated to quit if they learn that they have a high genetic risk of disease.

One possible complication is that information about APOE4 status could lead to fatalism rather than a determination to quit smoking, said symposium co-organizer Wylie Burke, chair of the UW Department of Medical History and Ethics. The issue is further complicated by the fact that the APOE4 polymorphism has also been linked to a higher risk of Alzheimer disease. People may view death by heart disease as a blessing compared to contracting Alzheimer disease, for which there is as yet no cure and no clear-cut means of prevention. Therefore, knowing one's own APOE4 status could decrease, rather than increase, a person's motivation to quit smoking. In addition, according to Burke, focusing on genetic susceptibility to smoking-related disease may draw attention from more important environmental factors, such as advertising, that encourage people of all genotypes to begin smoking in the first place.

Many other findings in gene-environment interactions raise similar ethical, legal, and social issues about whether society should focus on labeling individuals as susceptible to a given disease or simply reduce environmental exposures for everyone. "We need to be very careful to create the right environment in this era of rapidly accumulating genetic information," said Burke. "An overemphasis on the effects of genes relative to the effects of the environment can lead to oversimplification of the problem and distract attention from needed environmental change."
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Title Annotation:Toxicogenomics
Author:Freeman, Kris
Publication:Environmental Health Perspectives
Date:May 15, 2004
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