title: Tissue-specific splicing of an Ndufs6 gene-trap insertion generates a mitochondrial complex I deficiency-specific cardiomyopathy.
abstract: Mitochondrial complex I (CI) deficiency is the most common mitochondrial enzyme defect in humans. Treatment of mitochondrial disorders is currently inadequate, emphasizing the need for experimental models. In humans, mutations in the NDUFS6 gene, encoding a CI subunit, cause severe CI deficiency and neonatal death. In this study, we generated a CI-deficient mouse model by knockdown of the Ndufs6 gene using a gene-trap embryonic stem cell line. Ndufs6(gt/gt) mice have essentially complete knockout of the Ndufs6 subunit in heart, resulting in marked CI deficiency. Small amounts of wild-type Ndufs6 mRNA are present in other tissues, apparently due to tissue-specific mRNA splicing, resulting in milder CI defects. Ndufs6(gt/gt) mice are born healthy, attain normal weight and maturity, and are fertile. However, after 4 mo in males and 8 mo in females, Ndufs6(gt/gt) mice are at increased risk of cardiac failure and death. Before overt heart failure, Ndufs6(gt/gt) hearts show decreased ATP synthesis, accumulation of hydroxyacylcarnitine, but not reactive oxygen species (ROS). Ndufs6(gt/gt) mice develop biventricular enlargement by 1 mo, most pronounced in males, with scattered fibrosis and abnormal mitochondrial but normal myofibrillar ultrastructure. Ndufs6(gt/gt) isolated working heart preparations show markedly reduced left ventricular systolic function, cardiac output, and functional work capacity. This reduced energetic and functional capacity is consistent with a known susceptibility of individuals with mitochondrial cardiomyopathy to metabolic crises precipitated by stresses. This model of CI deficiency will facilitate studies of pathogenesis, modifier genes, and testing of therapeutic approaches.
authors.affiliation: Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, VIC 3052, Australia.
authors.forename: Bi-Xia
authors.initials: BX
authors.lastname: Ke
authors.forename: Salvatore
authors.initials: S
authors.lastname: Pepe
authors.forename: David R
authors.initials: DR
authors.lastname: Grubb
authors.forename: Jasper C
authors.initials: JC
authors.lastname: Komen
authors.forename: Adrienne
authors.initials: A
authors.lastname: Laskowski
authors.forename: Felicity A
authors.initials: FA
authors.lastname: Rodda
authors.forename: Belinda M
authors.initials: BM
authors.lastname: Hardman
authors.forename: James J
authors.initials: JJ
authors.lastname: Pitt
authors.forename: Michael T
authors.initials: MT
authors.lastname: Ryan
authors.forename: Michael
authors.initials: M
authors.lastname: Lazarou
authors.forename: Jane
authors.initials: J
authors.lastname: Koleff
authors.forename: Michael M H
authors.initials: MM
authors.lastname: Cheung
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Smolich
authors.forename: David R
authors.initials: DR
authors.lastname: Thorburn
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D009202:Cardiomyopathies / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D002331:Carnitine / Q000031:analogs & derivatives / Q000378:metabolism; D002460:Cell Line; D042967:Electron Transport Complex I / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D006321:Heart / Q000503:physiopathology; D006801:Humans; D066298:In Vitro Techniques; D053208:Kaplan-Meier Estimate; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D028361:Mitochondrial Diseases / Q000235:genetics* / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009206:Myocardium / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D009245:NADH Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D012326:RNA Splicing; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C116917:acylcarnitine; D000255:Adenosine Triphosphate; D009245:NADH Dehydrogenase; D042967:Electron Transport Complex I; D002331:Carnitine