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Spontaneous Mutations in Saccharomyces cerevisiae mtDNA Increase Cell-to-Cell Variation in mtDNA Amount

Elena Yu Potapenko1, Nataliia D Kashko1, Dmitry A Knorre2

  • 1Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119991, Russia.

International Journal of Molecular Sciences
|December 23, 2023
PubMed

Insights

mtDNA deletions disrupt copy number regulation, increasing cell-to-cell variation. Full-length mitochondrial DNA (mtDNA) is crucial for maintaining consistent mtDNA levels within cells.

Area of Science:

  • Cell Biology
  • Genetics
  • Molecular Biology

Background:

  • Eukaryotic cells maintain a specific ratio of mitochondrial DNA (mtDNA) to nuclear DNA (nDNA), suggesting a negative feedback mechanism.
  • Limited experimental data exist regarding the regulation of mtDNA copy number and potential disruptions.
  • mtDNA deletions are known to increase mtDNA abundance, potentially interfering with regulatory mechanisms.

Purpose of the Study:

  • To investigate if mtDNA deletions disrupt the negative feedback loop regulating mtDNA copy number.
  • To determine if mtDNA deletions increase cell-to-cell variance in mtDNA copy numbers.
  • To explore the role of full-length mtDNA in regulating mtDNA copy number homeostasis.

Main Methods:

  • Generation of *Saccharomyces cerevisiae rho* strains with large mtDNA deletions and *rho* strains with depleted mtDNA.
  • Quantification of mtDNA in individual yeast cells using flow cytometry and the DNA-intercalating dye SYTOX green.
  • Analysis of total DNA content and cell-to-cell heterogeneity in different cell cycle phases (G1 and G2/M).

Main Results:

  • *rho* mutations significantly increased both the levels and cell-to-cell heterogeneity of total DNA content in G1 and G2/M yeast cells.
  • The observed increase in DNA content heterogeneity was independent of cell size.
  • Depletion of mtDNA in both *rho* and *rho* strains led to a significant decrease in SYTOX green signal variance.

Conclusions:

  • mtDNA deletions disrupt the regulation of mtDNA copy number, leading to increased heterogeneity.
  • Full-length mtDNA is essential for the negative feedback mechanism that maintains mtDNA copy number homeostasis.
  • *rho* mtDNAs partially escape this regulation, contributing to observed variations in mtDNA levels.
Keywords:
cell cyclecell-to-cell heterogeneitydeletionsgenetic driftmtDNAyeast

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