👤 Fabienne C Fiesel

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. Show less

The kinase-ligase pair PINK1-PRKN initiates mitophagy by recognizing and selectively tagging worn-out and dysfunctional mitochondria with phosphorylated ubiquitin (pS65-Ub) to facilitate their elimination via autophagy. In human autopsy brains, the number of pS65-Ub positive cells increases with age but is also associated with Lewy body (LB), neurofibrillary tangles (NFT), and senile plaque (SP) burden. Through a recent genome-wide association study, we identified two genetic modifiers of pS65-Ub levels, APOE4 and ZMIZ1 rs6480922. While LB, NFT, and SP pathologies often coexist in Lewy body dementia (LBD), it is unclear how genetic factors and comorbid neuropathologies interact to impact mitophagy in vulnerable brain regions. We therefore measured levels of the age and disease marker pS65-Ub in the hippocampus and amygdala of 371 LBD cases. Significant and independent associations with pS65-Ub levels were observed for each of the three pathologies LB, NFT, and SP in both regions, and the presence of APOE4 significantly strengthened the association between NFT and pS65-Ub in the hippocampus. While no interaction between LB and SP pathologies was observed regarding association with pS65-Ub, a significant interaction between LB and NFT pathologies on pS65-Ub accumulation was found in the amygdala, which was primarily observed in carriers of the minor allele of ZMIZ1 rs6480922. In summary, our study revealed complex interactions between LB pathology, NFT pathology, and genetic mitophagy modifiers in LBD brains, highlighting potential convergent molecular mechanisms underlying α-synuclein- and tau-associated mitophagy alterations. Show less