Age-dependent accumulation of mitochondrial tRNA mutations in mouse kidneys linked to mitochondrial kidney diseases.

Heteroplasmic pathogenic mitochondrial DNA (mtDNA) mutations are key drivers of mitochondrial diseases, yet their tissue-specific and cell-specific accumulation patterns during aging and the mechanistic links to pathology remain poorly understood. In this study, we employed DddA-derived cytosine base editor technology to generate three mouse models harboring distinct pathogenic mitochondrial tRNA mutations. These mutations exhibited age-dependent accumulation in the kidneys, leading to severe kidney defects that well recapitulate human mitochondrial kidney disease. Mitochondrial single-cell assay for transposase-accessible chromatin with sequencing (mtscATAC-seq) revealed unique heteroplasmy dynamics across different kidney cell types: podocytes exhibited a positive selection for mutant mtDNA, whereas tubular epithelial cells displayed neutral drift of mutations during aging. Integrative analyses combining mtscATAC-seq, single-cell RNA sequencing and spatially enhanced resolution omics sequencing further identified molecular changes in high-mutant defective cells, including increased AP-1 family transcription factor activity, tubular epithelial cell proliferation and immune activation, which contribute to disease progression. Our study underscores the importance of kidney function monitoring in patients with mitochondrial disease, particularly in older adults, and establishes robust preclinical models to facilitate the development of therapeutic strategies.