|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.
|Source:||Nucleic acids research 43(21): 10338-52 (Journal)|
|Registered Authors:||Chan, Sherine, Rahn, Jennifer, Stackley, Krista|
|PubMed:||26519465 Full text @ Nucleic Acids Res.|
Rahn, J.J., Bestman, J.E., Stackley, K.D., Chan, S.S. (2015) Zebrafish lacking functional DNA polymerase gamma survive to juvenile stage, despite rapid and sustained mitochondrial DNA depletion, altered energetics and growth. Nucleic acids research. 43(21):10338-52.
ABSTRACTDNA 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.