Scientists at the U.S. National Institute of Environmental Health Sciences (NIEHS) in North Carolina have measured the different types of DNA changes that occur in skin cells and found that skin shielded from the sun can still accumulate DNA changes from UV light.
The research, which was published online ahead of print in PLOS Genetics (Jan. 14, 2021), also found that while mutations from ultraviolet (UV) light is common, Black individuals have lower levels of UV damage compared to White people.
Led by Dr. Dmitry Gordenin, the head of the Mechanism of Genome Dynamics at the NIEHS, researchers quantified the amounts of each type of genomic changes by sequencing the genomes of skin cells donated from 21 Black and White individuals, ranging in age from 25 to 79 years.
The investigators discovered that the total amount of genomic changes from metabolic by-products accumulates as a person gets older, while the amount of genomic changes caused by UV damage is unrelated to a person's age. Additionally, the researchers showed that genomic changes from UV light are common, even in skin cells typically shielded from the sun, but the changes were less prevalent in Black donors compared to white donors.
The researchers note the DNA in skin cells undergo damage from sources inside and outside the body, leading to genomic changes such as mutations that may lead to cancer. UV light is a major source of these mutations, but by-products of cellular metabolism—such as free radicals, and DNA copying errors that occur during cell division—also cause genomic changes.
These mutation-causing mechanisms are well known, but previously, researchers were unable to accurately measure the relative contributions from each source, according to the study’s authors.
Dr. Gordenin and his team suspect that Black individuals may be better protected from UV light due to higher levels of melanin. Supporting this idea is the fact that Black people have much lower rates of skin cancer compared to White people.
"The new study provides an accurate estimate of the genomic changes that occur in skin cells due to different types of DNA damage and establishes the normal range of somatic genomic changes across a wide range of ages and different races, providing a baseline for future research,” the study’s authors wrote.