Article

Murine cardiac mtDNA: effects of transgenic manipulation of nucleoside phosphorylation.

Department of Pathology, Emory University School of Medicine, 101 Woodruff Circle, Atlanta, GA 30322, USA.
Laboratory Investigation (impact factor: 3.64). 01/2009; 89(2):122-30. DOI:10.1038/labinvest.2008.121 pp.122-30
Source: PubMed

ABSTRACT Mitochondrial toxicity results from pyrimidine nucleoside reverse transcriptase inhibitors (NRTIs) for HIV/AIDS. In the heart, this can deplete mitochondrial (mt) DNA and cause cardiac dysfunction (eg, left ventricle hypertrophy, LVH). Four unique transgenic, cardiac-targeted overexpressors (TGs) were generated to determine their individual impact on native mitochondrial biogenesis and effects of NRTI administration on development of mitochondrial toxicity. TGs included cardiac-specific overexpression of native thymidine kinase 2 (TK2), two pathogenic TK2 mutants (H121N and I212N), and a mutant of mtDNA polymerase, pol-gamma (Y955C). Each was treated with antiretrovirals (AZT-HAART, 3 or 10 weeks, zidovudine (AZT) + lamivudine (3TC) + indinavir, or vehicle control). Parameters included left ventricle (LV) performance (echocardiography), LV mtDNA abundance (real-time PCR), and mitochondrial fine structure (electron microscopy, EM) as a function of duration of treatment and presence of TG. mtDNA abundance significantly decreased in Y955C TG, increased in TK2 native and I212N TGs, and was unchanged in H121N TGs at 10 weeks regardless of treatment. Y955C and I212N TGs exhibited LVH during growth irrespective of treatment. Y955C TGs exhibited cardiomyopathy (CM) at 3 and 10 weeks irrespective of treatment, whereas H121N and I212N TGs exhibited CM only after 10 weeks AZT-HAART. EM features were consistent with cardiac dysfunction. mtDNA abundance and cardiac functional changes were related to TG expression of mitochondrially related genes, mutations thereof, and NRTIs.

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    Article: DNA precursor asymmetries in mammalian tissue mitochondria and possible contribution to mutagenesis through reduced replication fidelity.
    Shiwei Song, Zachary F Pursell, William C Copeland, Matthew J Longley, Thomas A Kunkel, Christopher K Mathews
    [show abstract] [hide abstract]
    ABSTRACT: The mutation rate of the mammalian mitochondrial genome is higher than that of the nuclear genome. Because mitochondrial and nuclear deoxyribonucleoside triphosphate (dNTP) pools are physically distinct and because dNTP concentrations influence replication fidelity, we asked whether mitochondrial dNTP pools are asymmetric with respect to each other. We report here that the concentrations of the four dNTPs are not equal in mitochondria isolated from several tissues of both young and old rats. In particular, in most tissues examined, mitochondrial dGTP concentrations are high relative to the other dNTPs. Moreover, in the presence of the biased dNTP concentrations measured in heart and skeletal muscle, the fidelity of DNA synthesis in vitro by normally highly accurate mtDNA polymerase gamma is reduced, with error frequencies increased by as much as 3-fold, due to increased formation of template T.dGTP mismatches that are inefficiently corrected by proofreading. These data, plus some published data on specific mitochondrial mutations seen in human diseases, are consistent with the hypothesis that normal intramitochondrial dNTP pool asymmetries may contribute to spontaneous mutagenesis in the mammalian mitochondrial genome.
    Proceedings of the National Academy of Sciences 05/2005; 102(14):4990-5. · 9.68 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

10 weeks AZT-HAART
 
cardiac dysfunction
 
cardiac functional changes
 
cardiac-specific overexpression
 
cardiac-targeted overexpressors
 
cause cardiac dysfunction
 
I212N TGs exhibited CM
 
I212N TGs exhibited LVH
 
LV mtDNA abundance
 
mitochondrial fine structure
 
mitochondrial toxicity
 
Mitochondrial toxicity results
 
native mitochondrial biogenesis
 
native thymidine kinase 2
 
pathogenic TK2 mutants
 
pyrimidine nucleoside reverse transcriptase inhibitors
 
TG expression
 
TK2 native
 
vehicle control
 
Y955C TGs exhibited cardiomyopathy