Probability of Mitochondrial DNA heteroplasmy in different tissues from European populations.

Mitochondrial DNA (mtDNA) heteroplasmy complicates genetic analyses due to its variability across individuals and tissues. We analyzed over 400 Spanish blood samples and integrated published Massively Parallel Sequencing (MPS) data from ten additional European tissues. Heteroplasmy was tissue-specific, with skeletal muscle, kidney, and liver showing the highest levels, while the intestines, skin, and cerebellum had the lowest. Blood uniquely displayed more heteroplasmies in coding than non-coding regions. Several conserved positions not previously described as hotspots showed high frequencies. These results establish the first comprehensive tissue-specific heteroplasmic profile of the complete mitochondrial genome in a European population, improving the interpretation of mtDNA variation in forensic and biomedical contexts.