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Interviewees: John Novembre, UCLA & Carlos Bustamante, Cornell University
Where You’re From Is In Your Genes
By Heather Mayer
Up until now, a DNA sample could probably tell which continent your ancestors came from. Now a new genetic map could pinpoint a person’s geographic origins within a couple of hundred miles. Biostatisticians John Novembre of UCLA, and Carlos Bustamante and his team at Cornell University, used DNA data from thousands of people across Europe to create the map, which was recently published in the journal Nature.
“I almost fell off my chair when I saw the result,” Bustamante explains. “It was just so stunning that you could take this DNA data — you had no idea where these individuals came from — and smack in the middle was Switzerland, to the south was Italy, to the west was the Iberian peninsula; it was just completely stunning.”
After creating the map, the researchers showed they could use it to locate the origin of an unknown DNA sample, within certain limits.
“We can take DNA of an individual of unknown ancestry and answer the question of what their ancestry is,’ says Novembre. “So we can place them on a map even if we don’t know where they’re from.”
Genes, Drugs and Diseases
The genetic map of Europe was actually a byproduct of research Novembre and Bustamante were conducting for a pharmaceutical company. The researchers were working with GlaxoSmithKline, which had asked them to check and analyze a genetic database to study adverse drug reactions. This database catalogued gene chip data including hundreds of thousands of miniscule genetic differences called SNP’s among people from all over Europe.
GlaxoSmithKline was motivated to perform this study, which collected DNA from thousands of Europeans, to “develop a resource that could be used in our research to understand the genetics of drug response and for the study of adverse drug reactions in particular,” Matthew Nelson of GSK, a co-author of the paper, writes in an e-mail.
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According to Nelson, the study explains, “Population poses a well-recognized challenge for disease-association studies. The results obtained here reinforce that the geographic distribution of a sample is important to consider when evaluating genome-wide association studies.”
Statisticians Novembre and Bustamante plotted the DNA differences with software that didn’t know anything about the map of Europe, using distance to represent the amount of variation. The result matched the map of Europe.
“I was really expecting [to see these results] on one level, but I didn’t expect at all to see the resolution, especially the way you sort of see what looks like the Iberian Peninsula, the Italian Peninsula, the British isles projecting out. It’s quite surprising how nice the resolution is,” Novembre says.
Global Genetic Mapping
This discovery promises to help researchers design better genetic studies of diseases and drug responses, and to teach us more about peoples’ ancestral heritage.
“It would be exciting to look at variations around the whole world and look at many different populations,” Novembre says. “That’s what I’m most excited to see — is this kind of sampling within Europe expanded to a global scale.”
However, there are limitations to this first genetic map because the DNA samples used were from people whose grandparents came from the same country. So right now, if a person has a mixed heritage, for example, their mother comes from Spain and their father comes from France, the map would place this person in Italy, explains Novembre.
“But at the same time, it’s current, ongoing research for us to design an algorithm that will be able to do that, and I think we can do that,” he says.
Bustamante and Novembre have confidence they can take this genetic mapping to a global scale, which will help design better studies of genetics, drugs and diseases, as well as making ancestral research much more accurate.
“I think there are many applications we can envision of this technology, one of which would be to try to understand something about the ancestry of a sample and one of them would be forensics,” Bustamante says. “We’d love to be able to take a DNA test and try to understand, perhaps, do we have French royalty or do we trace our lineages back to Aristotle, and can we find that out with a drop of blood?”
This research was published in Nature advance online publication August 31, 2008 and was funded by: the Giorgi-Cavaglieri Foundation, the Swiss National Science Foundation, US National Science Foundation, US National Institutes of Health and GlaxoSmithKline.
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