Early-onset liver mtDNA depletion and late-onset proteinuric nephropathy in Mpv17 knockout mice. Hum Mol Genet

Unit of Molecular Neurogenetics - Pierfranco and Luisa Mariani Center for the Study of Mitochondrial Disorders in Children, IRCCS Foundation Neurological Institute C. Besta, Milan, Italy.
Human Molecular Genetics (Impact Factor: 6.68). 10/2008; 18(1):12-26. DOI: 10.1093/hmg/ddn309
Source: PubMed

ABSTRACT In humans, MPV17 mutations are responsible for severe mitochondrial depletion syndrome, mainly affecting the liver and the nervous system. To gain insight into physiopathology of MPV17-related disease, we investigated an available Mpv17 knockout animal model. We found severe mtDNA depletion in liver and, albeit to a lesser extent, in skeletal muscle, whereas hardly any depletion was detected in brain and kidney, up to 1 year after birth. Mouse embryonic fibroblasts did show mtDNA depletion, but only after several culturing passages, or in a serumless culturing medium. In spite of severe mtDNA depletion, only moderate decrease in respiratory chain enzymatic activities, and mild cytoarchitectural alterations, were observed in the Mpv17(-/-) livers, but neither cirrhosis nor failure ever occurred in this organ at any age. The mtDNA transcription rate was markedly increased in liver, which could contribute to compensate the severe mtDNA depletion. This phenomenon was associated with specific downregulation of Mterf1, a negative modulator of mtDNA transcription. The most relevant clinical features involved skin, inner ear and kidney. The coat of the Mpv17(-/-) mice turned gray early in adulthood, and 18-month or older mice developed focal segmental glomerulosclerosis (FSGS) with massive proteinuria. Concomitant degeneration of cochlear sensory epithelia was reported as well. These symptoms were associated with significantly shorter lifespan. Coincidental with the onset of FSGS, there was hardly any mtDNA left in the glomerular tufts. These results demonstrate that Mpv17 controls mtDNA copy number by a highly tissue- and possibly cytotype-specific mechanism.

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    • "), and genes with poorly defined functions related to mtDNA maintenance, including, MPV17 and, interestingly, subunits of the Kreb's cycle enzyme Succinyl-CoA Synthetase, SCS (SUCLG1, SUCLA2) (Suomalainen and Isohanni, 2010). While animal models have been reported for many of these genes (Haraguchi et al., 2002; Kimura et al., 2003; Hance et al., 2005; Tyynismaa et al., 2005; Akman et al., 2008; Martinez-Azorin et al., 2008; Lopez et al., 2009; Viscomi et al., 2009), there is currently no reported animal model for SCS–dependent mtDNA depletion. SCS is the TCA cycle enzyme responsible for the conversion of succinyl-CoA to succinate in the mitochondrial matrix that is coupled to the phosphorylation of GDP or ADP, thereby providing the only " substrate level " phosphorylation in the TCA cycle. "
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    ABSTRACT: Mutations in subunits of Succinyl-CoA Synthetase/Ligase (SCS), a component of the citric acid cycle, are associated with mitochondrial encephalomyopathy, elevation of methylmalonic acid (MMA), and mitochondrial DNA (mtDNA) depletion. While performing a FACS-based retroviral-mediated gene trap mutagenesis screen in mouse embryonic stem (ES) cells for abnormal mitochondrial phenotypes, a gene trap allele of Sucla2 (Sucla2(SAβgeo)) has been isolated in mouse embryonic stem (ES) cells and used to generate transgenic animals. Sucla2 encodes the ADP-specific β subunit isoform of SCS. Sucla2(SAβgeo) homozygotes exhibit recessive lethality, with most mutants dying late in gestation (e18.5). Mutant placenta and embryonic (e17.5) brain, heart and muscle show varying degrees of mtDNA depletion (20-60%), while there is no mtDNA depletion in mutant liver, where the gene is not normally expressed. Elevated levels of MMA are observed in embryonic brain. SCS deficient mouse embryonic fibroblasts (MEFs) demonstrate a 50% reduction in mtDNA content compared to wild type MEFs. The mtDNA depletion results in reduced steady state levels of mtDNA encoded proteins and multiple respiratory chain deficiencies, while mtDNA content can be restored by reintroduction of Sucla2. This mouse model of SCS deficiency and mtDNA depletion promises to provide insights into the pathogenesis of mitochondrial diseases with mtDNA depletion and into the biology of mtDNA maintenance. In addition, this report demonstrates the power of a genetic screen that combines gene trap mutagenesis and FACS analysis in mouse ES cells to identify mitochondrial phenotypes and to develop animal models of mitochondrial dysfunction.
    Disease Models and Mechanisms 11/2013; 7(2). DOI:10.1242/dmm.013466 · 5.54 Impact Factor
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    • "Induction prevents cardiovascular injury via anti-inflammatory effects [37], protects against platelet aggregation, and limits growth of vascular smooth muscle cells [38], effects that could contribute to I-R resistance in vivo. The function of induced Mpv17 is poorly understood, though there is evidence this inner mitochondrial membrane protein may regulate mtDNA copy number and longevity [39]. Tfrc encodes the transferrin receptor, which contributes to iron handling and could facilitate iron-dependent oxidative stress. "
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    ABSTRACT: Opioidergic SLP (sustained ligand-activated preconditioning) induced by 3-5 days of opioid receptor (OR) agonism induces persistent protection against ischemia-reperfusion (I-R) injury in young and aged hearts, and is mechanistically distinct from conventional preconditioning responses. We thus applied unbiased gene-array interrogation to identify molecular effects of SLP in pre- and post-ischemic myocardium. Male C57Bl/6 mice were implanted with 75 mg morphine or placebo pellets for 5 days. Resultant SLP did not modify cardiac function, and markedly reduced dysfunction and injury in perfused hearts subjected to 25 min ischemia/45 min reperfusion. Microarray analysis identified 14 up- and 86 down-regulated genes in normoxic hearts from SLP mice (≥1.3-fold change, FDR≤5%). Induced genes encoded sarcomeric/contractile proteins (Myh7, Mybpc3,Myom2,Des), natriuretic peptides (Nppa,Nppb) and stress-signaling elements (Csda,Ptgds). Highly repressed genes primarily encoded chemokines (Ccl2,Ccl4,Ccl7,Ccl9,Ccl13,Ccl3l3,Cxcl3), cytokines (Il1b,Il6,Tnf) and other proteins involved in inflammation/immunity (C3,Cd74,Cd83, Cd86,Hla-dbq1,Hla-drb1,Saa1,Selp,Serpina3), together with endoplasmic stress proteins (known: Dnajb1,Herpud1,Socs3; putative: Il6, Gadd45g,Rcan1) and transcriptional controllers (Egr2,Egr3, Fos,Hmox1,Nfkbid). Biological themes modified thus related to inflammation/immunity, together with cellular/cardiovascular movement and development. SLP also modified the transcriptional response to I-R (46 genes uniquely altered post-ischemia), which may influence later infarction/remodeling. This included up-regulated determinants of cellular resistance to oxidant (Mgst3,Gstm1,Gstm2) and other forms of stress (Xirp1,Ankrd1,Clu), and repression of stress-response genes (Hspa1a,Hspd1,Hsp90aa,Hsph1,Serpinh1) and Txnip. Protection via SLP is associated with transcriptional repression of inflammation/immunity, up-regulation of sarcomeric elements and natriuretic peptides, and modulation of cell stress, growth and development, while conventional protective molecules are unaltered.
    PLoS ONE 08/2013; 8(8):e72278. DOI:10.1371/journal.pone.0072278 · 3.23 Impact Factor
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    • "Strikingly, mutations in mpv17 in mice and humans lead to severe phenotypes resulting in early lethality of the affected individuals, which contrasts with the viability of the zebrafish tra/mpv17 mutants. Mice carrying an insertion in the mpv17 gene abolishing protein function develop mitochondrial DNA depletion, most prominently in the liver, and late onset glomerulosclerosis, hair graying and neurodegeneration of the peripheral nervous system (Meyer zum Gottesberge et al., 2012; Müller et al., 1997; Viscomi et al., 2009; Weiher et al., 1990). Likewise, several mutations in mpv17 were reported to be associated with mitochondrial DNA depletion syndrome in humans causing death during early childhood (AlSaman et al., 2012; El-Hattab et al., 2010; Navarro-Sastre et al., 2010; Spinazzola et al., 2008; Spinazzola et al., 2006; Wong et al., 2007). "
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    ABSTRACT: In the skin of adult zebrafish, three pigment cell types arrange into alternating horizontal stripes, melanophores in dark stripes, xanthophores in light interstripes and iridophores in both stripes and interstripes. The analysis of mutants and regeneration studies revealed that this pattern depends on interactions between melanophores and xanthophores; however, the role of iridophores in this process is less understood. We describe the adult viable and fertile mutant transparent (tra), which shows a loss or strong reduction of iridophores throughout larval and adult stages. In addition, in adults only the number of melanophores is strongly reduced, and stripes break up into spots. Stripes in the fins are normal. By cell transplantations we show that tra acts cell-autonomously in iridophores, whereas the reduction in melanophores in the body occurs secondarily as a consequence of iridophore loss. We conclude that differentiated iridophores are required for the accumulation and maintenance of melanophores during pigment pattern formation. The tra mutant phenotype is caused by a small deletion in mpv17, an ubiquituously expressed gene whose protein product, like its mammalian and yeast homologs, localizes to mitochondria. Iridophore death might be the result of mitochondrial dysfunction, consistent with the mitochondrial DNA depletion syndrome observed in mammalian mpv17 mutants. The specificity of the tra phenotype is most likely due to redundancy after gene multiplication, making this mutant a valuable model to understand the molecular function of Mpv17 in mitochondria.
    Biology Open 07/2013; 2(7):703-10. DOI:10.1242/bio.20135132 · 2.42 Impact Factor
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