Black Genes Matter
Researchers seek to include more African Americans in gene studies to improve health care.
Photo by Pat Mazzera
If black lives matter, so do black genes. Genes can influence how likely we are to get sick and how we’re diagnosed and treated. Much of what doctors know about the full set of genes we each have—our genome—is based on studies of white people. Now scientists are finding out that the genes of black people may hold clues to some important medical mysteries.
One of those mysteries is why African-American children get asthma more often than others. And when they inhale asthma medicine, they don’t always get the same quick relief that white kids get. They end up fighting for air, struggling to breathe.
“They can’t speak. They have trouble getting enough air in,” said Dr. Sam Lu, an Oakland pediatrician who sees kids at a mobile asthma clinic run by the Prescott-Joseph Center in West Oakland.
Part of the reason is that the genetic causes of asthma are different in blacks—and that affects how drugs work. But most genetic studies haven’t included enough African Americans to see this.
“We are far more likely to be hospitalized, to die more often,” said Dr. Michael Lenoir, an Oakland pediatrician. “There are so few African Americans in these studies that we don’t have any clue over the long haul of how well these medicines are going to work.
“It’s not just asthma,” he added. “It’s every chronic disease.”
Less than 4 percent of the participants in human gene studies are African Americans or Latin Americans. The studies are filled overwhelmingly with white patients, according to an analysis from the University of Washington published in October in the journal Nature.
The personal gene-testing company 23andMe announced recently that it will try to change that. Based in Mountain View, 23andMe plans to expand its database of gene samples to include the genomes of almost 1,000 African Americans. The data will be available for free to other researchers. That will make it easier for them to study black genes.
“23andMe has a tremendous opportunity to help address this disparity,” said Adam Auton, a geneticist and senior scientist at 23andMe.
Photo courtesy of Prescott-Joseph Center
Expanding genetic studies to more African Americans could solve some long-standing puzzles. Why are black children twice as likely to get asthma as white children, 13 percent vs. 7 percent?
And once they get asthma, why are African-American kids hospitalized for asthma three times more often than any other ethnic group in Alameda County and the United States as a whole?
Environmental factors like air pollution don’t explain it all. In Oakland, black kids living side by side with Hispanics had a 37 percent higher risk of asthma in one study.
With swift treatment, asthma attacks can usually be cut short. The most common “rescue” asthma drug is albuterol, a mist that’s inhaled. “It opens up airways,” said Dr. Esteban Burchard, a lung specialist at the University of California at San Francisco who has done groundbreaking genetic studies of asthma. Most kids get immediate relief.
But it turns out that the drug may not work as well in African-American (and Puerto Rican) kids. “When these kids go for their inhaler, they don’t get the same bang for their buck,” said Burchard. It’s a cruel irony that those with the highest rates of asthma attack also have the lowest response to the medicine.
Even worse, one study found longer-acting asthma drugs can cause serious medical complications—including deaths—eight times more often in blacks than in others, Burchard said.
He is doing studies on the genetics of asthma in black and other children that may show why drugs work differently in them. His colleague Marquitta White, a researcher on his team at UCSF, found that 95 percent of the genetic markers for asthma identified so far are found in whites—and not in blacks.
That could explain why black kids aren’t responding as well to drugs that work in white children. Genes can influence how the body breaks down medicine. That breakdown, or metabolism, drives how effective the medicine is against illness. It can also influence whether the drug causes dangerous side effects.
“We see real-life consequences of these mess-ups,” said Burchard. That’s what pushed him to obtain federal funding for a major study on the full gene set—the genome—in minority children. He thinks the project announced by 23andMe may help, too.
23andMe has data on gene snippets from tens of thousands of African Americans among its 1 million customers. But the personal gene-testing company wants to go deeper into the genetic samples, like Burchard, to identify the genome, which contains far more useful information. (See “Getting the Whole Story” below.)
Asthma isn’t the only illness that may affect African Americans differently because of genetics. The list is long and includes heart failure and breast cancer.
Burchard is pumped up about the potential for the studies from his lab, and 23andMe, to improve health by understanding African-American genetics.
“It’ll make a dent,” he said.
Getting the Whole Story from Genes
The gene samples that 23andMe usually collects from customers are snippets of a person’s gene set, rather than the whole set or genome. While the snippets are thought to show important parts of a gene (the “genotype”) for a particular condition, they don’t tell the whole story.
Think of genotypes as the letters contained in a story about each person’s health. A genotype sample shows a word with parts of some letters missing. Scientists must guess to fill in the blanks.
“You probably think you know what that word is from the context. But that’s a poor substitute for actually being able to read the whole word or the whole sentence,” said Adam Auton, senior scientist at 23andMe.
The genome is the whole sentence, showing all the letters and words. Scientists say the best way to understand how genes influence our health is to spell out (or “sequence”) the whole genome.
“We don’t generally do whole-genome sequencing because it’s much, much more expensive,” Auton said. But the company received a federal grant last fall to sequence the genomes of 925 African Americans—with the promise that the data will be made available to other scientists for free.
Published online on March 14, 2017 8:00 a.m.