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Zebrafish lacking functional DNA polymerase gamma survive to juvenile stage, despite rapid and sustained mitochondrial DNA depletion, altered energetics and growth.

Jennifer J Rahn | Jennifer E Bestman | Krista D Stackley | Sherine S L Chan
Nucleic acids research | 2015

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.

Pubmed ID: 26519465

Research resources used in this publication

None found

Antibodies used in this publication

None found

Associated grants

  • Agency: NIEHS NIH HHS, United States
    Id: R00ES015555
  • Agency: NIGMS NIH HHS, United States
    Id: 8 P20 GM103542-02
  • Agency: NIEHS NIH HHS, United States
    Id: R00 ES015555
  • Agency: NCATS NIH HHS, United States
    Id: UL1 TR000062
  • Agency: NCRR NIH HHS, United States
    Id: UL1 RR029882
  • Agency: NCRR NIH HHS, United States
    Id: P20 RR024485
  • Agency: NCRR NIH HHS, United States
    Id: 5P20RR024485-02
  • Agency: NCRR NIH HHS, United States
    Id: UL1RR029882

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This is a list of tools and resources that we have found mentioned in this publication.


Human DNA Polymerase Gamma Mutation Database (tool)

RRID:SCR_004722

Database that lists all known mutations in the coding region of the POLG gene and describes the associated disease. Human DNA polymerase is composed of two subunits, a 140 kDa catalytic subunit encoded by the POLG on chromosome 15q25, and a 55kDa accessory subunit encoded by the POLG2 gene on chromosome 17q23-24. A number of mutations have been mapped to the gene for the catalytic subunit of DNA polymerase, POLG, and found to be associated with mitochondrial diseases. The nucleotide changes are numbered from the initiation Methionine codon and are based on the cDNA (accession U60325.1) and gene sequence (accession AF497906.1).

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Center for Iron and Heme Disorders at the University of Utah Mutation Generation and Detection Core (tool)

RRID:SCR_015339

Core facility which provides custom TALEN and Crispr-Cas9 DNA nucleases to induce targeted mutations in a genomic region of interest. It also provides hardware, reagents, and expertise for optimizing and performing HRMA for genes of interest.

View all literature mentions