Two mitochondrial DNA polymorphisms modulate cardiolipin binding and lead to synthetic lethality

Area of Science:

• Genetics
• Mitochondrial Biology
• Molecular Biology

Background:

• Genetic screens are crucial for understanding nuclear gene interactions and phenotypes.
• Studying mitochondrial gene interactions and their phenotypic consequences has been limited by a lack of mapping tools for polymorphisms.

Purpose of the Study:

• To develop and apply tools for genetic interaction screens in animal mitochondrial DNA.
• To identify specific mitochondrial DNA polymorphisms that influence phenotypes associated with mitochondrial mutations.

Main Methods:

• Utilized a previously established toolkit in Drosophila to generate over 300 recombinant mitochondrial genomes.
• Mapped a naturally occurring polymorphism at cytochrome c oxidase III residue 109 (CoIII¹⁰⁹).
• Conducted lipidomics profiling, biochemical assays, and phenotypic analyses.

Main Results:

• Identified a CoIII¹⁰⁹ polymorphism that fully rescues lethality and defects caused by a cytochrome c oxidase I (CoI^T300I) mutation.
• Demonstrated that the CoIII¹⁰⁹ polymorphism modulates cardiolipin binding, preventing Complex IV instability.
• Showcased the feasibility of genetic interaction screens within animal mitochondrial DNA.

Conclusions:

• Established a method for genetic interaction screens in mitochondrial DNA.
• Unraveled complex intra-genomic interactions influencing mitochondrial DNA disorders and disease expression.
• Highlighted the role of specific polymorphisms in mitigating mitochondrial dysfunction.