WASHINGTON, Feb. 21 (UPI) -- The most detailed study yet compiled of how genes vary throughout the human family tree could speed efforts by medical researchers to treat ailments such as heart disease and mental illness.
The research also could even open doors to medical treatments personalized for each patient, experts told United Press International.
"You can take treatments that don't work so well on everyone, and identify which people they work best on and which patterns of (genetic) variation they have," said David Cox, chief scientific officer at Perlegen Sciences Inc. in Mountain View, Calif. "Based on that genetic barcode, you have information for more individualized and potentially more effective treatments of patients."
Cox and colleagues presented their findings at the American Association for the Advancement of Science annual meeting.
"For instance," he said, "if you have information on which specific gene variants work with a particular anti-hypertensive drug, you can determine which drugs work best for you."
Researchers probing the human genome have found that people are 99.99 percent similar across the globe. Nevertheless, there are differences among individuals relative to single letters in their genetic code -- the sequences of DNA that define genes. These minute variations, known as single nucleotide polymorphisms -- SNPs, pronounced "snips," for short -- help define a wide range of complex traits, such as eye color, height and body type.
Until recently, scientists had only scratched the surface looking for gene variations in humans.
Now Perlegen is working with the International Computer Science Institute in Berkeley, Calif., and the University of California, San Diego, to describe nearly 1.6 million SNPs observed in 71 unrelated people of African-American, Chinese-American and European-American descent.
SNPs tend to be inherited together in patterns called haplotypes, which can continue unchanged for thousands of years. The researchers estimate at least 7 million common SNPs exist in the human genome, but they think the 1.6 million they have inspected represent most of the variants among those 7 million.
The job of scientists now is to see what SNP patterns are linked to traits such as diseases.
"You can anticipate in the next year or so studies exploring this," Cox said.
There is a lot of "excitement regarding this work in the public health sector," said Dr. Lawrence Lesko, director of the Food and Drug Administration's Office of Clinical Pharmacology and Biopharmaceutics.
"This can help us understand the variability between populations in propensity of a disease, the development of that disease over time and response ... to therapy," Lesko told UPI. "For instance, why is the response rate of (the lung cancer drug) Iressa high in Japanese subjects but low in the United States? We've been using very crude measures of distinguishing one patient from another based on sex, age and race. Now we might have an approach that looks more at the mechanisms."
The most common SNPs are found across all populations and likely date back to the origin of humans in Africa. Others could prove specific to certain populations.
The researchers emphasized, however, their data do not point to any genetic basis for race. The patterns of variation more closely resemble gradients and cut across what people call races, Cox said.
"Pick any pattern of SNPs and you are equally likely to find it in people of different races," he explained.
The question of race-based biology is a growing concern. Sociologist Troy Duster of New York University pointed to the drug BiDil from NitroMed in Lexington, Mass., which is likely to receive FDA approval this year and has even been called the first racial drug.
BiDil, originally found ineffective in treating heart disease in the general population, later was shown to work well in a three-year trial of 1,050 African-Americans. Extensive research over the past two decades has revealed frequent differences in hypertension and heart disease between Americans of European and African descent.
"If approved by the FDA (the drug already has been approved by the Association of Black Cardiologists) there is a cultural groove we can slip into, giving the social categories of race the imprimatur of legitimacy in the genetic field," Duster told UPI.
"Race has nothing to do with DNA validation -- it's an artificial concept," Cox added.
The international HapMap project, in which Perlegen is participating, is expected later this year to release an even more detailed description of genetic variations, with more than 1 million SNPs from 270 people across Chinese, European, Japanese and Nigerian ancestries.
The project is a collaboration among scientists and funding agencies from Canada, China, Japan, Nigeria, the United Kingdom and the United States.
"Although the work described is clearly exciting to scientists, it is important to state that while personalized medicine is a possibility, it is by no means a certainty," cautioned David Altschuler at Massachusetts General Hospital in Boston, a HapMap Project member.
"While we are certain (that) diseases have a strong genetic component, there's this risk of genetic determinism," Altschuler said.
Not all responses to medications are due to genetics, he added, citing the well-known story about grapefruit juice inhibiting drug response.
That bit of information resulted from clustering of research results because a particular family drank grapefruit juice and therefore it was assumed there was a genetic component. Altschuler cautioned, however, the genetic factor "could be modest."
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Charles Choi covers research and technology for UPI Science News. E-mail: [email protected]
