title: Mitochondrial genome linearization is a causative factor for cardiomyopathy in mice and Drosophila.
abstract: OBJECTIVE
  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.
  
  
  RESULTS
  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.
  
  
  METHODS
  This is the first description of mitochondrial genome linearization as a causative factor in cardiomyopathy.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Internal Medicine, Center for Pharmacogenomics, Washington University School of Medicine , St. Louis, Missouri.
authors.forename: Yun
authors.initials: Y
authors.lastname: Chen
authors.forename: Megan
authors.initials: M
authors.lastname: Sparks
authors.forename: Poonam
authors.initials: P
authors.lastname: Bhandari
authors.forename: Scot J
authors.initials: SJ
authors.lastname: Matkovich
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Dorn
mesh_terms: D000818:Animals; D009202:Cardiomyopathies / Q000235:genetics* / Q000473:pathology; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage / Q000235:genetics*; D004261:DNA Replication / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics*; D029721:Drosophila Proteins / Q000172:deficiency / Q000235:genetics; D004331:Drosophila melanogaster / Q000235:genetics; D054629:Genome, Mitochondrial / Q000235:genetics*; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics; D051379:Mice; D008929:Mitochondria, Heart / Q000235:genetics*; D032383:Myocytes, Cardiac / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000235:genetics; D000099202:PTEN-Induced Putative Kinase
chemical_list: D004272:DNA, Mitochondrial; D029721:Drosophila Proteins; D008565:Membrane Proteins; D017346:Protein Serine-Threonine Kinases; D044767:Ubiquitin-Protein Ligases; C527117:Marf protein, Drosophila; C534484:PINK1 protein, Drosophila; D000099202:PTEN-Induced Putative Kinase; C487430:park protein, Drosophila
references.citation: Hum Mol Genet. 2012 Nov 15;21(22):4817-26
references.pmid: 22859504
references.citation: PLoS One. 2012;7(9):e44296
references.pmid: 22957060
references.citation: Circ Res. 2010 May 14;106(9):1459-67
references.pmid: 20360248
references.citation: Circ Res. 2011 Jan 7;108(1):12-7
references.pmid: 21148429
references.citation: Biochim Biophys Acta. 2013 Jan;1833(1):233-41
references.pmid: 22450031
references.citation: J Clin Invest. 2013 Mar;123(3):951-7
references.pmid: 23454757
references.citation: Circ Res. 2010 Oct 15;107(8):1032-40
references.pmid: 20705924
references.citation: Am J Hum Genet. 1998 Apr;62(4):745-51
references.pmid: 9529371
references.citation: Cell Metab. 2010 Dec 1;12(6):675-82
references.pmid: 21109200
references.citation: Aging Cell. 2013 Aug;12(4):728-31
references.pmid: 23742009
references.citation: Science. 2008 Jul 25;321(5888):575-7
references.pmid: 18653897
references.citation: Circ Res. 2012 Sep 14;111(7):863-75
references.pmid: 22777004
references.citation: Gene. 2000 Apr 4;246(1-2):37-48
references.pmid: 10767525
references.citation: Mol Cell. 2010 Sep 24;39(6):851-61
references.pmid: 20864033
references.citation: Circ Res. 2011 Dec 9;109(12):1327-31
references.pmid: 22052916
references.citation: Proc Natl Acad Sci U S A. 2010 May 18;107(20):9035-42
references.pmid: 20418503
references.citation: Genome Biol. 2009;10(3):R25
references.pmid: 19261174
references.citation: Circ Res. 2003 Jun 13;92(11):1171-5
references.pmid: 12805233
references.citation: Nat Genet. 2001 Jul;28(3):272-5
references.pmid: 11431699
references.citation: J Cell Biol. 2003 Jan 20;160(2):189-200
references.pmid: 12527753
references.citation: Proc Natl Acad Sci U S A. 1979 Apr;76(4):1967-71
references.pmid: 109836
references.citation: Annu Rev Genet. 2012;46:265-87
references.pmid: 22934639
references.citation: Science. 2012 Aug 31;337(6098):1062-5
references.pmid: 22936770
references.citation: Cell. 2007 Aug 10;130(3):548-62
references.pmid: 17693261
references.citation: Proc Natl Acad Sci U S A. 2012 Apr 3;109(14):5523-8
references.pmid: 22427360
references.citation: Biochem J. 2003 Mar 15;370(Pt 3):751-62
references.pmid: 12467494
references.citation: Hum Mol Genet. 2012 Nov 15;21(22):4827-35
references.pmid: 22914740
references.citation: Aging Cell. 2010 Aug;9(4):536-44
references.pmid: 20456298
references.citation: Science. 2013 Apr 26;340(6131):471-5
references.pmid: 23620051
references.citation: PLoS Genet. 2011 Mar;7(3):e1002028
references.pmid: 21455489
references.citation: Cell Metab. 2010 Dec 1;12(6):633-42
references.pmid: 21109195
references.citation: Nat Rev Genet. 2005 May;6(5):389-402
references.pmid: 15861210
references.citation: Biochim Biophys Acta. 2010 Jun-Jul;1797(6-7):1086-98
references.pmid: 20056105
references.citation: Bioinformatics. 2009 Sep 1;25(17):2283-5
references.pmid: 19542151
references.citation: Antioxid Redox Signal. 2011 May 15;14(10):1939-51
references.pmid: 21128700
references.citation: Evolution. 1987 Jul;41(4):854-863
references.pmid: 28564361
references.citation: Cell. 2010 Apr 16;141(2):280-9
references.pmid: 20403324
references.citation: Nature. 2011 Feb 17;470(7334):342-3
references.pmid: 21307852
references.citation: Genes Dev. 2004 Feb 15;18(4):357-68
references.pmid: 15004004