Customized Genomic Studies Reveal How Genes Influence Health

Two recent studies have used individual genetic data to reveal the powers and limits of the current understanding of how the genome influences human health and what genes can reveal about the ancestry of the people in the U.S. state of New Hampshire.

Published in the September 11, 2009, issue of the American Journal of Human Genetics, Dartmouth University (Hanover, NH, USA) professor Dr. Jason Moore and Vanderbilt University (Nashville, TN, USA) professor Dr. Scott Williams analyzed how personal genetic testing companies are using still-nascent genomic data to evaluate the health of their customers.

People can now buy inexpensive kits, submit a DNA sample (often a swab from the inside of a cheek or a little bit of saliva), and receive data about their susceptibility to a number of gene-influenced ailments, such as prostate cancer, Alzheimer's, or type II diabetes. Drs. Moore and Williams argue that people's knowledge of the human genome and its relationship to human health, while growing rapidly, is still in its infancy.

"The relationship between health and genetics is very complex," said Dr. Moore, professor of genetics and of community and family medicine at Dartmouth Medical School (DMS). "It's often a combination of multiple genes and multiple environmental factors that work together to increase or decrease your risk of disease. I don't think the knowledge base is sufficient to put genetics in the hands of the public quite yet."

The investigators admit that genetic research is progressing, and they cite the example of the discovery of the BRCA1 and BRCA2 genes and their role in breast cancer. However, the authors cautioned that, while there is no question these genes are involved in breast cancer, the underlying processes behind the genetic risk are still being worked out. "There is a perception that these tests can provide answers," stated Dr. Moore. "I used my own genetic material for this study, and my results didn't really tell me anything I didn't know, based on family history."

Drs. Moore and Williams call for refocusing and stepping up the research on gene-to-gene and gene-to-environment interactions. They explained that for quite a while, researchers have focused on single genes and clinical endpoints. The time has come, they noted, to accept rather than ignore the complexity of human traits as they are expressed by the whole genome working in concert. "Although genetic testing for common human diseases is not yet useful, using genetic testing results to reveal an individual's ancestry is increasingly reliable," remarked Dr. Moore. He and Ph.D. candidate Chantel Sloan recently extracted some genetic data for a study that examined the population structure of New Hampshire residents.

Published in the September 2009 issue of PLoS ONE (a journal of the Public Library of Science), this study by Drs. Sloan and Moore and their colleagues analyzed more than 1,000 genetic markers from 864 people in the state of New Hampshire. They discovered six subgroups of people with distinct genetic backgrounds including a group of Finnish and Russian/Polish/Lithuanian ancestry. "I knew that people would be primarily European," remarked Dr. Sloan. "What I didn't expect was the strong connection between genetic structure and people of Eastern European ancestry, which I learned is consistent with New Hampshire census and immigration data from 1870 to 1930."

Dr. Sloan utilized data initially compiled for a cancer study, therefore the genetic markers were cancer susceptibility genes rather than known ancestral genes, and the population being analyzed was not racially or geographically distinct. The study's findings challenge the assumption that large numbers of special genetic markers are needed to discover genetically distinct groups of people.

"This is an example of how personal genetic data can be used to help inform people of their ancestry," concluded Dr. Moore. "Informing people of their future health is still out of reach, though."

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