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Author Notes:

e-mail: jjkohle@emory.edu

Subject:

Research Funding:

National Heart, Lung, and Blood Institute : NHLBI

National Institute of Diabetes and Digestive and Kidney Diseases : NIDDK

Keywords:

  • Cardiomyopathy
  • Murine model
  • mtDNA
  • NRTI
  • Toxicity

Cardiac-Targeted Transgenic Mutant Mitochondrial Enzymes

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Journal Title:

Cardiovascular Toxicology

Volume:

Volume 8, Number 2

Publisher:

, Pages 57-69

Type of Work:

Article | Post-print: After Peer Review

Abstract:

Mitochondrial (mt) DNA biogenesis is critical to cardiac contractility. DNA polymerase gamma (pol γ) replicates mtDNA, whereas thymidine kinase 2 (TK2) monophosphorylates pyrimidines intramitochondrially. Point mutations in POLG and TK2 result in clinical diseases associated with mtDNA depletion and organ dysfunction. Pyrimidine analogs (NRTIs) inhibit Pol γ and mtDNA replication. Cardiac “dominant negative” murine transgenes (TGs; Pol γ Y955G, and TK2 H121N or I212N) defined the role of each in the heart. mtDNA abundance, histopathological features, histochemistry, mitochondrial protein abundance, morphometry, and echocardiography were determined for TGs in “2 × 2” studies with or without pyrimidine analogs. Cardiac mtDNA abundance decreased in Y955C TGs (∼50%) but increased in H121N and I212N TGs (20-70%). Succinate dehydrogenase (SDH) increased in hearts of all mutants. Ultrastructural changes occurred in Y955C and H121N TGs. Histopathology demonstrated hypertrophy in H121N, LV dilation in I212N, and both hypertrophy and dilation in Y955C TGs. Antiretrovirals increased LV mass (≈50%) for all three TGs which combined with dilation indicates cardiomyopathy. Taken together, these studies demonstrate three manifestations of cardiac dysfunction that depend on the nature of the specific mutation and antiretroviral treatment. Mutations in genes for mtDNA biogenesis increase risk for defective mtDNA replication, leading to LV hypertrophy.

Copyright information:

© Humana Press 2008

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