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Modern humans originated on the continent of Africa more than 300,000 years ago, and subsequent generations migrated across the land, with groups intermarrying or splitting apart. Sometime around 80,000 years ago, a small number of descendants left the continent and radiated around the globe, taking with them just a subset of the genes and genetic variation that their ancestors had developed.
Yet genetic studies are now dominated by that subset, according to a new article in Cell.
As of last year, 78 percent of the people included in the most prominent form of genomic research — genome-wide association studies (GWAS) — were of European ancestry. But worldwide, Europeans and their descendents make up just 12 percent of the population.
According to the researchers, heavily biased genetic databases could — and do — lead scientists and doctors to diagnose conditions or prescribe treatments that might be relevant to people with European genes, but not for people from other racial backgrounds.
“If we don’t include ethnically diverse populations, we are potentially going to be exacerbating health inequalities,” said Sarah Tishkoff, study coauthor and a human geneticist at the University of Pennsylvania.
Any two humans in the world share about 99.9 percent of their DNA with one another, but that 0.1 percent of variation is incredibly important. That variation can be just single replacements here and there in the four-letter code of a person’s genetic material, and can make the difference between a gene that works to encode healthy proteins, and a gene that fails and makes a person sick.
Genetics interact with other factors, like diet, activity and access to resources, all of which determine a person’s health. And health treatments that don’t take the variations of genetically diverse populations into account can cause problems.
Just a few tiny changes in the genetic code can have large effects on the effectiveness of a drug like the blood-thinner warfarin, and therefore the amount of medication that will be effective and safe for a patient.
But those changes are only well-studied in Europeans, the researchers argue. Algorithms that help doctors prescribe the right amount of warfarin for an individual patient work fairly well for people with European genes, but are far less accurate for African Americans.
In one study of 274 African American patients, one of those genotype-guided algorithms consistently prescribed too much medication, resulting in a high risk of uncontrolled bleeding.
Without better data and tailoring to more gene variations, prescriptions designed to help patients, in the end, could hurt them instead.
The lack of genetic diversity is “a social injustice, and a missed scientific opportunity,” said Esteban Burchard, who is a physician and epidemiologist at the University of California, San Francisco, and was not involved in the new paper. “But it’s not surprising.”
In his own research, Burchard sees similar disparities in studies of Americans in Puerto Rico. When he proposes research on minorities, he said, committees and funding organizations ask how that research will generalize to the white population. “They never ask the other way around.”
Biased genetic databases are also missing out on research into human genetic variation that could actually benefit everyone, the study’s researchers said.
Populations of humans acquire distinct genetic mutations over time, through selection or genetic drift. The more of these genes that we can study, the more likely we are to discover ones that are particularly useful for understanding how a disease works, or how a treatment for a disease might be created.
One genetic mutation found through studying people of African descent, for example, quickly became a prime target for helping scientists understand how some cholesterol is regulated in the body.
“It’s a beautiful example where a rare mutation is suppressing a gene,” said University of Pennsylvania geneticist Giorgio Sirugo, who also contributed to the paper.
Once researchers figured out why that suppression of that gene lowered cholesterol, they were able to create treatments to mimic the effect, leading to drugs that could work for people of any racial background.
It’s no accident that there is a disparity in the people represented in genetic studies.
It’s partially convenience, the researchers said. When studies are mostly performed in the U.S. or Europe, researchers are likely to use the racial majority where they live.
The human reference genome, for example — the result of the $2.7 billion Human Genome Project — was constructed from samples taken in Buffalo, New York, an area with predominantly European ancestry. Its limitations are becoming more and more clear.
Also, even when studies branch out from institutions in the U.S. and Europe, they may be faced with challenges in finding medical equipment and facilities that will be precise and reliable for quality genetic research. In rural areas of developing countries, researchers may not have access to reliable electricity, let alone microscopes, refrigerators or more sophisticated laboratory equipment.
But it’s also based in historical trauma. Minority populations have been faced with serious medical abuses, like the infamous Tuskegee Study in which hundreds of black men with syphilis were observed by doctors but left to die of the disease untreated. For black communities in America, trust in medical institutions is still marred by those injustices.
In light of that history, “this has to be done right. Ultimately, [the people who participate] should be the ones to benefit from the information we gain,” Tishkoff said.
Meanwhile, Burchard said, it’s a tense climate in research and politics when it comes to talking about race at all.
While race cannot and does not divide humans into biologically distinct populations, it is a useful proxy for genetic and social patterns for researchers studying public health, Burchard said.
And yet conversations about race, diversity and social justice are increasingly polarized even within the scientific community.
“All of our work focuses on racial differences, but this is the first time in my career at UCSF that I’ve been nervous about giving a talk,” Burchard said.
Although the National Institutes of Health are working toward closing the genetic research disparity, at least for minority populations in the U.S., the researchers maintain that there is a lot of work to do. Most of that work involves funding studies that investigate the genetics of scientifically underrepresented people around the globe.
“By not including diversity we are missing out on great opportunities to make novel discoveries and to be more inclusive of world populations,” Burchard said.
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