The missing diversity in human epigenomic studies

June 9, 2022

Recent research has highlighted a lack of diversity in genomics, an interdisciplinary field that focuses on the structure, function, evolution, mapping and editing of the genome — an organism’s complete set of DNA.

Less attention, however, has been given to understanding diversity in the field of epigenomics, which studies modifications to the genetic material of a cell known as the epigenome.

In a new study published in Nature Genetics, researchers show that epigenomic studies also underrepresent diverse populations, which undermines scientists’ ability to understand the causes and risks of disease in different groups of people.

Dr. Nora Franceschini

Nora Franceschini, MD, MPH, FAHA, a professor of epidemiology at the UNC-Chapel Hill Gillings School of Global Public Health, and Charles Breeze, PhD, with the National Cancer Institute, worked with two co-authors to propose solutions to this problem.

“Information regarding the race or ethnicity of International Human Epigenome Consortium (IHEC) samples highlights disparities, the researchers report. “Of the 5,048 publicly available experiments with race or ethnicity information, 87.1% were labelled as European; 9.3% were reported as African, African American or Black; 1.7% were of Asian ancestry, and the remaining 1.9% were of other ancestries.”

The full extent to which ancestry affects epigenetic modifications is unknown. Improving the diversity of research datasets is critical, though, because evidence has already shown there can be significant epigenomic variation between populations, particularly when it comes to DNA methylation.

“We anticipate that more associations between genotype, DNA methylation and ancestry may be uncovered in the future, which could potentially help explain population disparities in disease risk,” the co-authors state. “In short, the role of ancestry-related DNA sequence variants in driving epigenetic variation needs to be explored further.”

“It will be really important to generate more epigenetic data in diverse populations to better understand the scope of the differences across populations and their impact on disease risk,” Franceschini notes. “We need to know if epigenetic differences are driven by genotypes or lifetime harmful exposures that vary in different populations.”

“Our results show that diversity in epigenomics is not increasing, but actually decreasing over time,” Breeze adds. “This is surprising, especially as our analysis includes recent years (up to 2021). Genomics consortia should focus on increasing diversity now in order to avoid exacerbating health disparities, given that epigenomics affects how we interpret genetic variants.”

Contact the UNC Gillings School of Global Public Health communications team at sphcomm@unc.edu.