Intergenerational and organ-specific alterations in mitochondrial DNA copy number following preconception irradiation

Ionizing radiation, a potent inducer of redox stress, perturbs both nuclear and mitochondrial genomes, yet how such stress shapes mitochondrial inheritance across generations remains unclear. In this study, we examined intergenerational and organ-specific mitochondrial responses to parental X-ray irradiation in mice. Eight-week-old male and female C57BL/6N mice were exposed to 2 Gy of single whole-body X-ray irradiation before mating, generating paternal-, maternal-, and dual-irradiated lineages. In the parents, peripheral blood-derived mitochondrial DNA copy number (mtDNAcn) transiently increased one day after exposure, consistent with a rapid mitochondrial response to redox stress. In newborn offspring, mtDNAcn displayed clear organ- and parent-of-origin specificity: brain mtDNAcn decreased in paternal- and dual-irradiation lineages, heart mtDNAcn remained unchanged, and liver mtDNAcn showed the most pronounced depletion across all irradiated lineages. No significant inter-organ correlations in mtDNAcn were observed. All irradiated lineages exhibited increased body weight and increased liver weight at birth, with a significant positive association between these traits. Liver weight was negatively associated with hepatic mtDNAcn. Multiple regression analysis further showed that maternal pre-exposure mtDNAcn and offspring hepatic mtDNAcn independently predicted neonatal liver weight. Taken together, these findings demonstrate that preconception irradiation induces acute mitochondrial responses in parents and is associated with intergenerational, organ-specific mtDNAcn dysregulation that manifests as offspring birth outcomes. Parental irradiation perturbs organ-specific mitochondrial genome regulation and predisposes the next generation to altered growth-related traits.