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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, RESULTS, METHODS. Meshes: Animals, Cardiomyopathies, DNA Breaks, Double-Stranded, DNA Damage, DNA Replication, DNA, Mitochondrial, Drosophila Proteins, Drosophila melanogaster, Genome, Mitochondrial, Membrane Proteins, Mice, Mitochondria, Heart, Myocytes, Cardiac, Protein-Serine-Threonine Kinases, Ubiquitin-Protein Ligases.
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Is mitochondrial genome linearization a causative factor for cardiomyopathy in mice and Drosophila? Context: Mitofusin (Mfn)2 redundantly promotes mitochondrial outer membrane tethering and organelle fusion with Mfn1, and uniquely functions as the mitochondrial receptor for Parkin during PTEN-induced putative kinase 1 (PINK1)-Parkin-mediated mitophagy. Selective deletion of Mfn2 with retention of Mfn1 preserves mitochondrial fusion while rendering damaged mitochondria resistant to normal quality control culling mechanisms. Consequently, neuron and cardiomyocyte-specific Mfn2 gene ablation is associated with accumulation of damaged mitochondria and organ dysfunction. Here, we determined how mitochondrial DNA (mtDNA) damage contributes to cardiomyopathy in Mfn2-deficient hearts. RNA sequencing of Mfn2-deficient hearts revealed increased expression of some nuclear-encoded mitochondrial genes, but mitochondrial-encoded transcripts were not upregulated in parallel and mtDNA content was decreased. Ultra-deep sequencing of mtDNA showed no increase in single nucleotide mutations, but copy number variations representing insertion-deletion (in-del) mutations were induced over time by cardiomyocyte-specific Mfn2 deficiency. Double-strand mtDNA breaks in the form of in-dels were confirmed by polymerase chain reaction, and in the form of linear mitochondrial genomes were identified by southern blot analysis. Linearization of Drosophila cardiomyocyte mtDNA using conditional cardiomyocyte-specific expression of mitochondrial targeted XhoI recapitulated the cardiomyopathy of Mfn2-deficient mouse hearts. This is the first description of mitochondrial genome linearization as a causative factor in cardiomyopathy.
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One of the consequences of interrupting mitochondrial culling by the PINK1-Mfn2-Parkin mechanism is an increase in mtDNA double-stranded breaks, which adversely impact mitochondrial function and DNA replication. Final Decision: yes