ZFIN ID: ZDB-PUB-151101-7
Zebrafish lacking functional DNA polymerase gamma survive to juvenile stage, despite rapid and sustained mitochondrial DNA depletion, altered energetics and growth
Rahn, J.J., Bestman, J.E., Stackley, K.D., Chan, S.S.
Date: 2015
Source: Nucleic acids research   43(21): 10338-52 (Journal)
Registered Authors: Chan, Sherine, Rahn, Jennifer, Stackley, Krista
Keywords: none
MeSH Terms:
  • Adenosine Triphosphate/metabolism
  • Animal Fins/physiology
  • Animals
  • DNA, Mitochondrial/analysis*
  • DNA-Directed DNA Polymerase/chemistry
  • DNA-Directed DNA Polymerase/genetics*
  • DNA-Directed DNA Polymerase/metabolism
  • Genetic Engineering
  • Glycolysis
  • Models, Animal
  • Mutation
  • Oxygen Consumption
  • Regeneration
  • Survival Analysis
  • Zebrafish/genetics*
  • Zebrafish/growth & development
  • Zebrafish Proteins/chemistry
  • Zebrafish Proteins/genetics*
  • Zebrafish Proteins/metabolism
PubMed: 26519465 Full text @ Nucleic Acids Res.
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ABSTRACT
DNA polymerase gamma (POLG) is essential for replication and repair of mitochondrial DNA (mtDNA). Mutations in POLG cause mtDNA instability and a diverse range of poorly understood human diseases. Here, we created a unique Polg animal model, by modifying polg within the critical and highly conserved polymerase domain in zebrafish. polg(+/-) offspring were indistinguishable from WT siblings in multiple phenotypic and biochemical measures. However, polg(-/-) mutants developed severe mtDNA depletion by one week post-fertilization (wpf), developed slowly and had regenerative defects, yet surprisingly survived up to 4 wpf. An in vivo mtDNA polymerase activity assay utilizing ethidium bromide (EtBr) to deplete mtDNA, showed that polg(+/-) and WT zebrafish fully recover mtDNA content two weeks post-EtBr removal. EtBr further reduced already low levels of mtDNA in polg(-/-) animals, but mtDNA content did not recover following release from EtBr. Despite significantly decreased respiration that corresponded with tissue-specific levels of mtDNA, polg(-/-) animals had WT levels of ATP and no increase in lactate. This zebrafish model of mitochondrial disease now provides unique opportunities for studying mtDNA instability from multiple angles, as polg(-/-) mutants can survive to juvenile stage, rather than lose viability in embryogenesis as seen in Polg mutant mice.
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