Darker skin is linked to fewer mtDNA variants from sun exposure

In six older men, researchers analyzed somatic mitochondrial DNA variants from paired skin biopsies taken from photoexposed forearms and photoprotected buttocks. The participants included three Black African and three White Northern European men. Targeted sequencing identified 21 high-confidence somatic variants. Photoexposed light skin possessed six-fold more variants than dark skin and showed a broader spectrum of variant types, including insertions, deletions, and dinucleotide substitutions. Light skin was enriched for C>T transitions and CC>TT substitutions, which are signatures of chronic ultraviolet radiation. These variants affected multiple oxidative phosphorylation genes and frequently reached moderate-to-high heteroplasmy. Conversely, dark skin displayed a more restricted profile dominated by a recurrent T414G substitution, with predominantly low-impact variants and substantially lower heteroplasmy overall.