Early-onset Parkinson disease caused by a mutation in CHCHD2 and mitochondrial dysfunction

Area of Science:

• Genetics
• Neuroscience
• Mitochondrial Biology

Background:

• Early-onset Parkinson disease (PD) presents before age 50, often with a genetic component.
• The genetic underpinnings of recessive early-onset PD remain incompletely understood.
• Mitochondrial dysfunction is increasingly implicated in neurodegenerative disorders.

Purpose of the Study:

• To identify the specific gene(s) responsible for an early-onset Parkinson disease (PD) phenotype.
• To elucidate the molecular mechanisms and cellular defects caused by the identified genetic mutation.

Main Methods:

• Whole-exome sequencing was employed to identify candidate genes.
• Functional genomics, fluorescence microscopy, and cell/mitochondrial biology assays were utilized.
• Analysis of patient-derived fibroblasts was performed to assess molecular defects.

Main Results:

• A homozygous variant in the *CHCHD2* gene was identified in a patient with early-onset PD.
• *CHCHD2* encodes a mitochondrial protein; its mutation led to mitochondrial fragmentation.
• The mutation impaired oxidative phosphorylation (complexes I and IV), increased reactive oxygen species, and elevated metabolic rate.

Conclusions:

• The *CHCHD2* gene is implicated in the pathogenesis of recessive early-onset Parkinson disease.
• This study expands the known roles of mitochondrial proteins in PD.
• CHCHD2 mutations represent a novel genetic factor contributing to Parkinson disease.