One complaint leveled against genome studies is that they don’t survey a broad enough swath of humankind. Though many projects have searched DNA collected from people of European descent -- hoping to ferret out which changes in what parts of the genome are linked to this disease or that -- fewer have investigated the genomes of other ethnic groups.
In 2011, Stanford University geneticist and MacArthur “genius” grant recipient Carlos Bustamante discussed such disparities in genetic research with The Times, saying that about 96% of the participants in medical genomics studies were of European descent.
If other ethnic groups with different genetic backgrounds go unstudied, Bustamante said, they’ll be less likely to benefit from medical advances emerging from the work.
“The rest of the world is being left behind,” he said, “and we view that as problematic.”
In Tuesday’s Journal of the American Medical Assn., a group of researchers reported on a study that should help expand the field: a new analysis of genes in African Americans that are associated with late-onset Alzheimer’s disease.
By and large, the work, which looked at DNA data collected from nearly 6,000 African Americans, implicated the same regions of the genome as past studies of people of European descent had.
As in the past research, variations in a gene known as APOE were most strongly linked to developing Alzheimer’s in the test subjects.
Several other genes already known to be linked to Alzheimer’s also showed up in the new analysis, but one, ABCA7, had a particularly strong link: Study subjects who had changes in that location were 1.8 times more likely to have Alzheimer’s disease than people without the changes. The effect was about 60% stronger in the African Americans than it had been in subjects of European descent, the team reported.
Further studies will be needed to confirm the link between ABCA7 and late-onset Alzheimer’s in African-Americans, the researchers said. But if the association is validated, they wrote, it may help scientists better understand the biology of Alzheimer’s disease and could “have major implications for developing targets for genetic testing, prevention and treatment.”
The incidence of Alzheimer’s is higher among African Americans than it is among people of European descent living in the same communities.
When might the discovery start aiding Alzheimer’s patients directly? It’s hard to say, UC San Francisco geneticist Dr. Robert Nussbaum said in an accompanying editorial.
“How useful is having this information? Here the answer is not so clear,” he wrote. “When it comes to personal genomics, clinical utility remains in the eye of the beholder.”