A deafness-associated tRNAHis mutation alters the mitochondrial function, ROS production and membrane potential

Area of Science:

• Molecular Genetics
• Mitochondrial Biology
• Auditory Science

Background:

• Deafness can be caused by mutations in mitochondrial DNA (mtDNA).
• Mitochondrial tRNAs (mt-tRNAs) are crucial for protein synthesis within mitochondria.
• Specific mt-tRNA mutations can disrupt mitochondrial function and lead to disease.

Purpose of the Study:

• To investigate the molecular genetic mechanism of the deafness-associated mitochondrial tRNAHis m.12201T>C mutation.
• To understand how this mutation affects tRNAHis structure, function, and mitochondrial translation.
• To elucidate the downstream consequences of this mutation on cellular respiration and ATP production.

Main Methods:

• Utilized cybrid models by transferring mitochondria from a patient's cell line into mtDNA-less cells.
• Assessed tRNAHis levels, conformation (electrophoretic mobility), and aminoacylation status.
• Quantified levels of mtDNA-encoded polypeptides, ATP production, membrane potential, and reactive oxygen species (ROS).

Main Results:

• The m.12201T>C mutation destabilized tRNAHis structure and reduced its steady-state levels by ~70%.
• Despite altered conformation, aminoacylation of tRNAHis increased by ~60%.
• Mutant cells showed significant reductions in mtDNA-encoded polypeptides (~46% average), impaired respiratory capacity, decreased ATP levels, and increased ROS production.

Conclusions:

• The mitochondrial tRNAHis m.12201T>C mutation disrupts tRNA structure and function, leading to impaired mitochondrial translation.
• These molecular defects result in mitochondrial dysfunction, including reduced respiratory capacity and ATP synthesis.
• The study provides evidence linking this specific mitochondrial tRNAHis mutation to the pathogenesis of deafness.