It’s been two decades since the Human Genome Project first unveiled a rough draft of our genetic instruction book. The promise of that medical moon shot was that doctors would soon be able to look at an individual’s DNA and prescribe the right medicines for that person’s illness or even prevent certain diseases. That promise, known as precision medicine, has yet to be fulfilled in any widespread way. True, researchers are getting clues about some genetic variants linked to certain conditions and some that affect how drugs work in the body. But many of those advances have benefited just one group: people whose ancestral roots stem from Europe. In other words, white people.
Instead of a truly human genome that represents everyone, “what we have is essentially a European genome,” says Constance Hilliard, an evolutionary historian at the University of North Texas in Denton. “That data doesn’t work for anybody apart from people of European ancestry.” She’s talking about more than the Human Genome Project’s reference genome. That database is just one of many that researchers are using to develop precision medicine strategies. Often those genetic databases draw on data mainly from white participants. But race isn’t the issue. The problem is that collectively, those data add up to a catalog of genetic variants that don’t represent the full range of human genetic diversity.
When people of African, Asian, Native American or Pacific Island ancestry get a DNA test to determine if they inherited a variant that may cause cancer or if a particular drug will work for them, they’re often left with more questions than answers. The results often reveal “variants of uncertain significance,” leaving doctors with too little useful information. This happens less often for people of European descent. That disparity could change if genetics included a more diverse group of participants, researchers agree (SN: 9/17/16, p. 8).
One solution is to make customized reference genomes for populations whose members die from cancer or heart disease at higher rates than other groups, for example, or who face other worse health outcomes, Hilliard suggests. And the more specific the better. For instance, African Americans who descended from enslaved people have geographic and ecological origins as well as evolutionary and social histories distinct from those of recent African immigrants to the United States. Those histories have left stamps in the DNA that can make a difference in people’s health today. The same goes for Indigenous people from various parts of the world and Latino people from Mexico versus the Caribbean or Central or South America. Researchers have made efforts to boost diversity among participants in genetic studies, but there is still a long way to go. How to involve more people of diverse backgrounds which goes beyond race and ethnicity to include geographic, social and economic diversity in genetic research is fraught with thorny ethical questions.
What is diversity in genetics?
Recruiting people from all over the world to participate in genetic research might seem like the way to increase diversity, but that’s a fallacy, Hilliard says. If you really want genetic diversity, look to Africa, she says. Humans originated in Africa, and the continent is home to the most genetically diverse people in the world. Ancestors of Europeans, Asians, Native Americans and Pacific Islanders carry only part of that diversity, so sequencing genomes from geographically dispersed people won’t capture the full range of variants. But sequencing genomes of 3 million people in Africa could accomplish that task, medical geneticist Ambroise Wonkam of the University of Cape Town in South Africa proposed February 10 in Nature
Wonkam is a leader in H3Africa, or Human Heredity and Health in Africa. That project has cataloged genetic diversity in sub-Saharan Africa by deciphering the genomes of 426 people representing 50 groups on the continent. The team found more than 3 million genetic variants that had never been seen before, the researchers reported October 28 in Nature. “What we found is that populations that are not well represented in current databases are where we got the most bang for the buck; you see so much more variation there,” says Neil Hanchard, a geneticist and physician at Baylor College of Medicine in Houston.
What’s more, groups living side by side can be genetically distinct. For instance, the Berom of Nigeria, a large ethnic population of about 2 million people, has a genetic profile more similar to East African groups than to neighboring West African groups. In many genetic studies, scientists use another large Nigerian group, the Yoruba, “as the go-to for Africa. But that’s probably not representative of Nigeria, let alone Africa,” Hanchard says.
That’s why Hilliard argues for separate reference genomes or similar tools for groups with health problems that may be linked to their genetic and localized geographic ancestry. For West Africa, for example, this might mean different reference datasets for groups from the coast and those from more inland regions, the birthplace of many African Americans’ ancestors.
Courtesy of https://www.sciencenews.org/article/genetics-race-dna-databases-reference-genome-too-white By Tina Hesman Saey