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Kidney Week

Abstract: PO2225

Kidney-Specific Landscape of Aging Mitochondrial DNA Mutations by Duplex Sequencing

Session Information

Category: Pathology and Lab Medicine

  • 1601 Pathology and Lab Medicine: Basic

Authors

  • Sweetwyne, Mariya T., University of Washington School of Medicine, Seattle, Washington, United States
  • Sanchez-Contreras, Monica Y., University of Washington School of Medicine, Seattle, Washington, United States
  • Tsantilas, Kristine A., University of Washington School of Medicine, Seattle, Washington, United States
  • Whitson, Jeremy A., University of Washington School of Medicine, Seattle, Washington, United States
  • Campbell, Matthew D., University of Washington School of Medicine, Seattle, Washington, United States
  • Marcinek, David J., University of Washington School of Medicine, Seattle, Washington, United States
  • Rabinovitch, Peter S., University of Washington School of Medicine, Seattle, Washington, United States
  • Kennedy, Scott R., University of Washington School of Medicine, Seattle, Washington, United States
Background

Accumulation of mutations in the mitochondrial genome (mtDNA) is a potential mechanism of aging in the mitochondrial rich kidney, where mtDNA damage also increases with diabetes, CKD and AKI. Accurately detecting low level somatic mtDNA mutations within the cellular complexity of the kidney was previously confounded by variable levels of mtDNA heteroplasmy. Using ultra-sensitive Duplex Sequencing (DS), a modified next-gen sequencing (NGS) technique, we decreased the error rate relative to conventional NGS by >104x, allowing us to accurately characterize mtDNA mutation patterns unique to the aging kidney relative to other organs.

Methods

We compared mtDNA mutations in kidneys from cohorts of aged (26-m.o.) and young (5-m.o.) NIA C57Bl/6j mice to multiple organs with high mitochondrial content (heart, eye, liver, skeletal muscle and brain). In both ages, kidney carried the highest burden of mtDNA point mutations. Mutation spectrum analysis showed that mtDNA point mutations in the kidney increased significantly with age and were primarily G>A/C>T, indicative of polymerase error (2.5x10-5p > 0.0001 relative to all other tissues) with G>T/C>A mutations, indicative of oxidative damage, the second most common type. Aged kidneys were further separated into glomeruli or tubule-rich whole cortex fractions to determine regional mutation burden.

Results

Glomeruli had ~25% fewer total mtDNA mutations (p= 0.002) and specifically ~80% fewer oxidative lesions (G>T/C>A, G>C/C>G, p= 0.02). Furthermore, differential accumulation of mtDNA mutation between kidney fractions does not appear to be randomly distributed across the genome but is instead gene-specific as demonstrated by significantly reduced mutations in glomeruli of mt-rRNA gene mtRnr1 but not mtRnr2, and of Complex IV gene mt-Co2, but not mt-Co1 or 3. Finally, we sequenced kidneys from aged mice treated systemically for 8 weeks with SS-31, a mitochondrial therapeutic peptide that reduces oxidative stress in the kidney, and found that mutations stemming from oxidation, but not polymerase error, were significantly reduced.

Conclusion

These data suggest that renal mtDNA mutation is cell specific and that even in old age, accumulation of some mutations is tractable with therapeutic intervention.

Funding

  • Other NIH Support