The mtDNA mutation spectrum of the progeroid Polg mutator mouse includes abundant control region multimers

Area of Science:

• Mitochondrial biology
• Genetics
• Aging research

Background:

• Polg mtDNA mutator mice are key models for studying aging and acquired mtDNA mutations.
• The exact cause of the progeroid phenotype and mtDNA mutation spectrum in these mice is unclear.
• Disrupted polymerase-gamma function's impact on mtDNA mutation accumulation requires further investigation.

Purpose of the Study:

• To elucidate the mtDNA mutation spectrum induced by disrupted polymerase-gamma function.
• To characterize the structural integrity of mtDNA in Polg mutator mice.
• To introduce and validate a novel sequencing approach for mtDNA analysis.

Main Methods:

• Development of "Mito-seq," a novel next-generation sequencing approach.
• Application of Mito-seq to enriched, native mtDNA from Polg mutator mice and controls.
• Analysis of mtDNA single nucleotide variants and structural abnormalities.

Main Results:

• A significant increase (at least two orders of magnitude) in mtDNA single nucleotide variants was observed in Polg mutator mice.
• No evidence of canonical mtDNA deletions was found.
• Multimers of the mtDNA control region (CRMs) with heterogeneous breakpoints were identified in brain and heart tissues.

Conclusions:

• Disruption of polymerase-gamma function leads to a dramatic increase in mtDNA single nucleotide variants.
• mtDNA control region multimers (CRMs) are a consequence of impaired polymerase-gamma exonuclease activity.
• Polymerase-gamma's 3'-5' exonuclease activity is essential for maintaining mtDNA integrity.