Mitochondrially encoded tRNA leucine 1 (MT-TL1) m.A3243G mutation (MT-TL1 m.A3243G)

The m.A3243G mutation is a pathogenic point mutation located within the MT-TL1 gene, which encodes the mitochondrial transfer RNA for leucine (UUR). This mutation is the most frequent cause of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) and is also linked to Maternally Inherited Diabetes and Deafness (MIDD) (NIH, 2023). Biologically, the A-to-G transition at position 3243 impairs the taurinomethyluridine modification of the tRNA wobble position, which is essential for accurate codon recognition (PubMed, 15689493). This impairment leads to a significant reduction in mitochondrial protein synthesis, specifically affecting the assembly of respiratory chain complexes I and IV (PubMed, 11726920). The resulting mitochondrial dysfunction causes a decrease in ATP production and an increase in oxidative stress, leading to multi-organ failure, particularly in high-energy-demand tissues like the brain and muscle. Current pharmacological management involves the use of L-arginine to improve nitric oxide availability and reduce the severity of stroke-like episodes (PubMed, 15738446). Emerging therapeutic strategies target the mutant sequence directly using mitochondria-targeted nucleases, such as mitoTALENs or mitoZFNs, to selectively degrade mutant mtDNA and shift heteroplasmy toward the wild-type (PubMed, 23708102). Other approaches include the use of small molecules like Elamipretide to stabilize mitochondrial membranes or tRNA bypass strategies to restore translation.

Other names

m.3243A>GMELAS mutationtRNA-Leu(UUR) A3243GMitochondrial A3243G mutationMT-TL1*MELAS3243

Sequence-specific degradation of mutant mitochondrial DNA to shift heteroplasmy, restoration of mitochondrial translation, and reduction of oxidative stress.