Mitoepigenetic Alterations in Early-Onset Parkinson's Disease

Area of Science:

• Epigenetics
• Neuroscience
• Genomics

Background:

• Distinct mitochondrial DNA (mtDNA) methylation and hydroxymethylation patterns are increasingly linked to Parkinson's disease (PD).
• Previous studies focused on specific mtDNA regions, lacked non-CpG context analysis, and faced methodological limitations.
• A comprehensive analysis of the entire mitochondrial genome's epigenetic landscape in early-onset PD (EOPD) is needed.

Purpose of the Study:

• To comprehensively profile global and single-base resolution methylation and hydroxymethylation across the entire mitochondrial genome.
• To investigate these epigenetic modifications in both CpG and non-CpG contexts in blood samples from EOPD patients and controls.
• To evaluate the potential of mtDNA (hydroxy)methylation patterns as blood-based biomarkers for EOPD.

Main Methods:

• Blood samples from 39 EOPD patients and 63 age- and sex-matched controls were analyzed.
• Parallel workflows using bisulfite (BS) and oxidative-bisulfite (oxBS) conversions followed by next-generation sequencing (NGS) were employed.
• Mitochondrial 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) were identified in CpG, CHG, and CHH contexts.

Main Results:

• Global mtDNA methylation was significantly higher in EOPD patients compared to controls in both BS and oxBS statuses (true methylation).
• Analysis at single-base resolution revealed predominantly hypomethylated sites in the D-loop region and CpG context in EOPD patients.
• Significant differences in methylation and hydroxymethylation were observed across all contexts (CpG, CHG, CHH) in EOPD.

Conclusions:

• Comprehensive analysis reveals significant alterations in global and site-specific mtDNA (hydroxy)methylation in EOPD.
• The identified epigenetic patterns in CpG and non-CpG contexts offer novel insights into PD pathogenesis.
• Both global and base-resolution mtDNA (hydroxy)methylation profiles demonstrate potential as reliable blood-based biomarkers for early-onset Parkinson's disease.