Searching for Links Between Race, Genes, and Disease

From diabetes to heart disease, African-Americans have a higher rate of many common ailments compared to European Americans. It’s known as “the Health Gap,” a term used to describe disparities in disease burdens and death rates between America’s minority population and its white population. 

Earlier this month, Boston University geneticists joined with researchers at Howard University to begin the first genome-wide scan of an African-American population, in order to examine what role genes may play in several health problems and risk factors more prevalent among African-Americans, including obesity, hypertension, and diabetes.

Over the next year, the researchers will scan the DNA of about 1,800 African-Americans for 500,000 genetic markers, known as single nucleotide polymorphisms (SNPs), and then look for associations between those genetic differences and the aforementioned medical conditions. Identifying genetic links with diseases could improve identification of people at increased risk, help in the creation of diagnostic tests, and aid the development of targeted new drugs.

Genetically speaking, people around the world are “extremely closely related,” explains Michael Christman, chair of the School of Medicine department of genetics and genomics and a coleader of the project. He estimates that only about 10 percent of SNPs are not evenly distributed among people of different racial and ethnic backgrounds.

“It’s important to look into those 10 percent of variants that are different in order to have genomics benefit African-Americans as a specific population,” says Christman. But, he adds, “it’s also important to explore the other 90 percent that are the same, by doing genomic scans of populations for which there’s good data.”

Indeed, the key to validating the researchers’ results is for scientists scanning the genomes of other populations to find the same associations between specific genetic variants and health conditions. To that end, the BU department of genetics and genomics last month launched GMED, a public searchable database containing the preliminary data from its genome scans of about 1,320 participants in the Framingham Heart Study, a National Heart, Lung, and Blood Institute initiative that has tracked the health of families in Framingham, Mass., since 1948, and that BU has run since 1971. 

So far, one of the BU researchers’ findings, a genetic association with obesity, has been confirmed in scans of other populations. About 200 other genetic associations still await confirmation.

“I think the biggest effect [of discovering new genetic links with disease] will be more intelligent drug design,” says Christman, who notes that much of the reason pharmaceuticals are expensive is that so many of them fail, adding to the cost of development.

The subjects in the African-American genome scan are largely from the Washington, D.C., metropolitan area and have been recruited over the past four years by researchers at Howard University’s National Genome Center, led by geneticist Charles Rotimi, the project’s other coleader. The BU researchers will scan the DNA from the subjects’ blood samples using microarrays that contain microscopic probes to identify SNPs across the thousands of genes that make up the human genome. They expect preliminary results within the next year.

“This project creates an opportunity to begin to understand at a very fundamental level what could be the possible reasons for the variations we see in disease distribution among different populations,” says Rotimi. “How much of these disparities have to do with genes and how much has to do with societal structure, things like poverty and socioeconomic class?”

Christman says that it hasn’t officially been decided whether the associations found in the African-American genome scan will be added to the GMED database. But, he adds, “that would be my hope.”