Mutant mitochondrial DNA (mtDNA)

Mutant mitochondrial DNA (mtDNA) refers to pathogenic alterations in the 16,569 base pair circular genome located within the mitochondria, which is essential for oxidative phosphorylation and energy production (Gorman et al., 2016). Because cells contain hundreds to thousands of copies of mtDNA, mutations often exist in a state of heteroplasmy, where mutant and wild-type genomes coexist; clinical symptoms typically manifest only when the mutant load exceeds a critical threshold (Pikrell et al., 2016). These mutations are primary drivers of mitochondrial diseases such as MELAS and LHON, and are increasingly implicated in aging and neurodegeneration (Wallace, 2012). Therapeutic strategies focus on "heteroplasmy shifting," using targeted nucleases like Mito-TALENs or Mito-ZFNs to selectively degrade mutant genomes, thereby allowing wild-type mtDNA to repopulate the cell (Gammage et al., 2018). Emerging base editing technologies, such as DdCBE, offer the potential to correct specific point mutations without inducing double-strand breaks (Mok et al., 2020). Pharmacological agents like Elamipretide or Idebenone are also used to mitigate the downstream effects of mtDNA mutations on the respiratory chain (Karaa et al., 2018). Challenges in targeting mtDNA include the physical barriers of the double mitochondrial membrane and the need for high-efficiency delivery to post-mitotic tissues like the brain and muscle (Russell et al., 2020).

Other names

Pathogenic mitochondrial DNAHeteroplasmic mitochondrial DNA mutationsMitochondrial genome variantsmtDNA mutations

Heteroplasmy shifting via selective degradation of mutant mtDNA to allow wild-type expansion, mitochondrial base editing for direct sequence correction, and pharmacological stabilization of the mitochondrial membrane or bypass of respiratory chain defects.