Association of mitochondrial genetic background with pS65-Ub in Lewy body disease

Mitochondrial dysfunction is a hallmark of neurodegenerative diseases, where respiratory defects and downstream bioenergetic failures arise from impaired mitophagy or the accumulation of damaged mitochondria. Mitophagy is a mitochondrial quality-control pathway in which mitochondria tagged with ubiquitin phosphorylated at Serine 65 (pS65-Ub) are targeted for degradation via the autophagy-lysosome system. We previously identified a significant genome-wide association between apolipoprotein E ε4 [APOE ε4] with pS65-Ub levels in the hippocampus of Lewy body disease (LBD). However, the relationship between genetic background in the mitochondrial genome and the PINK1-PRKN pathway biomarker pS65-Ub remains to be elucidated. In this study, we examined whether mitochondrial DNA (mtDNA) variation contributes to changes in pS65-Ub level in 514 neuropathologically confirmed LBD brains, with replication in an independent cohort of 384 LBD brains. No individual mtDNA haplogroup was significantly associated with pS65-Ub levels after correction for multiple testing (P < 0.005 considered significant); mtDNA haplogroup V exhibited a nominally significant (P < 0.05) association, but this association was not observed in an independent replication series. Our data reveal an overall lack of direct evidence linking mtDNA variations to mitophagy marker pS65-Ub levels in LBD, suggesting that mitochondrial damage is unlikely to be explained by major mtDNA determinants alone and may instead reflect cumulative and multilayered perturbations of mitochondrial function. Single cell analyses combined with larger replication cohorts integrating multi-omics datasets will be essential to validate these findings and to advance the discovery of biomarkers for mitochondrial dysfunction in neurodegeneration.