Restoration of mitochondrial function through activation of hypomodified tRNAs with pathogenic mutations associated...

Area of Science:

• Mitochondrial biology
• Molecular genetics
• Biochemistry

Background:

• Mutations in mitochondrial transfer RNAs (mt-tRNAs) are a common cause of mitochondrial dysfunction.
• Diseases like MELAS and MERRF result from pathogenic point mutations in mtDNA-encoded tRNA genes, leading to hypomodified tRNAs and impaired mitochondrial protein synthesis.
• Previously, a reduction in 5-taurinomethyluridine (τm5U) and 2-thiouridine (τm5s2U) modifications in mutant mt-tRNAs from MELAS and MERRF patients was reported.

Purpose of the Study:

• To investigate the potential of restoring tRNA modifications to reactivate mitochondrial function in MELAS and MERRF patient cells.
• To evaluate the efficacy of MTO1 enzyme overexpression in correcting hypomodified mt-tRNAs and improving mitochondrial activity.

Main Methods:

• Overexpression of MTO1, a τm5U-modifying enzyme, in patient-derived myoblasts.
• Utilizing a novel primer extension method to assess tRNA modification levels.
• Measuring mitochondrial protein synthesis and oxygen consumption rates.

Main Results:

• MTO1 overexpression restored τm5U modification in the MELAS mutant mt-tRNALeu(UUR) to near-normal levels.
• This restoration led to increased mitochondrial protein synthesis and oxygen consumption rates in MELAS patient cells.
• MTO1 expression also successfully restored the τm5s2U modification in the MERRF mutant mt-tRNALys.

Conclusions:

• Restoring essential tRNA modifications, specifically τm5U, can reactivate mitochondrial function in cells affected by MELAS.
• The findings support the potential of MTO1 as a therapeutic target for mitochondrial diseases caused by tRNA mutations.
• This study opens avenues for developing epitranscriptomic therapies for a range of mitochondrial disorders.