People from Mexico Show Vast Genetic Diversity

The genetic diversity of the Mexican population is so vast that two people of Mexican descent can be as genetically different from each other as a European and a Chinese person. That's the finding of researchers from UC San Francisco, Stanford, and the Mexican National Institute of Genomic Medicine. It's considered the first, large-scale analysis of its kind,  and the study could change the way health care is delivered to Mexican-Americans. It helps drive forward the move toward personalized medicine.

KQED News anchor Mina Kim spoke with UCSF Professor Esteban Burchard, one of the co-authors of the study, during a Thursday evening newscast. Burchard described that because of "historical factors, geographical factors, linguistic factors," the researchers identified that indigenous populations in Mexico are genetically distinct. The genetic ancestry mirrors the geography of Mexico."

Researchers looked at contemporary Mexican populations of mestizos, people of mixed European and indigenous blood, and were able to "precisely trace back their genetic ancestry to particular indigenous groups or tribes," Burchard said. "It has tremendous implications for medicine. From there we used a simple case of lung measurements, where we measured the size of (a person's) lungs, and we demonstrated that the type of Native American ancestry you have determined the size of your lungs."

This information can influence the way a doctor might treat a patient with a specific illness, and the findings are relevant far beyond Mexico. Burchard said that the methods the team used, and the findings, are generalizable globally. Part of the impetus for the study was to diversify genetic research itself. Burchard noted that "96 percent of contemporary modern-day genetic studies have been done in populations of European origin or European Americans."

"That means a vast swath of the world population are not deriving the benefits of the Human Genome Project," Burchard told Kim. "That's important because we know that rates or prevalence of disease vary by race and even response to medications vary by race. By understanding the genetic underpinnings of that, we can better develop medications and therapies precisely for Mina Kim and not for all Asians."

The ultimate goal, Burchard said, is to better understand global populations, "so that we can advance precision medicine worldwide." Burchard talked about his desire to move beyond race or ethnicity "and get down to what is the gene particularly for MIna Kim and avoid the fact that 'Esteban, you're racially mixed,' or 'Mina, you're Asian'. I would like to find out for a particular gene that causes a disease, what are the mutations that are driving that disease and how do we fix it? Because we have drugs that work for different mutations."

But researchers not involved in the study urged caution in focusing so closely on a genetic basis for a disease. In interviews with the Los Angeles Times, some noted that a focus on genetics might mask more critical socioeconomic or environmental factors driving diseae.

From the Times:

The suggestion that differences in DNA are responsible for observed differences in lung capacity “is an enormous leap,” said UC Berkeley sociologist Troy Duster, who has written extensively on the intersection of race, biology and public policy.

Lundy Braun, an Africana studies professor at Brown University who studies the intersection of race and medicine, said medicine’s focus on genetics may be overshadowing other avenues of research.

“The effects of social class on lung function have been largely ignored in favor of the focus on race and ethnic difference,” she said.