Differential Regulation of Mitochondrial and Autophagy Markers in a Mouse Model of Cardioskeletal Myopathy

Abstract

Objective: Mitochondrial translation defects are a major cause of cardioskeletal myopathies, yet how mitochondrial biogenesis and autophagic turnover diverge between striated muscles in vivo remains unclear.Material and Methods: Using a heart- and skeletal muscle–specific mitochondrial aspartyl-tRNA synthetase (DARS2) knockout mouse model, mitochondrial protein markers (TOM20, VDAC) and biogenesis-associated transcripts (Tfam, Pgc-1α) were compared between the heart and quadriceps, and autophagy markers (LC3B-I/II and P62/SQSTM1) were assessed at baseline and following colchicine administration.Results: Knockout hearts displayed strong biogenesis-associated remodeling; in contrast, quadriceps displayed no induction of these markers. Steady-state autophagy markers in knockout hearts demonstrated reduced LC3B-II (and LC3B-II/I ratio) alongside marked P62 accumulation, which is consistent with impaired autophagic degradation/cargo clearance. Notably, colchicine did not elicit the expected LC3B-II accumulation in the heart, complicating straightforward flux interpretation in the cardiomyopathic context. In the quadriceps, colchicine robustly increased LC3B-II levels and the LC3B-II/LC3B-I ratio in both control and knockout muscles, indicating measurable autophagic response and supporting the technical feasibility of colchicine-based flux assays in this tissue.Conclusion: Together, these findings reveal pronounced tissue divergence in mitochondrial remodeling in DARS2-related cardioskeletal myopathy and underscore caution when interpreting colchicine-based autophagy flux assays in heart versus skeletal muscle.