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mtDNA extramitochondrial replication mediates mitochondrial defect effects

Zhaoliang Shan1, Shengnan Li1, Yuxue Gao1

  • 1State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animals for Disease Study, Jiangsu Key Laboratory of Molecular Medicine, Model Animal Research Center, School of Medicine, Nanjing University, Nanjing 210061, China.

Iscience
|February 7, 2024
PubMed

Insights

Scientists discovered a new pathway involving Med8/Tfb4-mtSSB/PolG2/mtDNA-helicase that rescues mitochondrial defects in flies. This pathway amplifies cytosolic mitochondrial DNA, impacting disease and aging.

Area of Science:

  • Mitochondrial biology
  • Genetics
  • Molecular mechanisms of disease

Background:

  • Severe mitochondrial defects are linked to numerous human mitochondrial diseases.
  • The in vivo rescue mechanisms for mitochondrial defects remain poorly understood.

Purpose of the Study:

  • To investigate the in vivo rescue signals for mitochondrial defects.
  • To identify genetic factors that can ameliorate mitochondrial dysfunction.

Main Methods:

  • Established Drosophila melanogaster models with mitochondrial defects by knocking down dMterf4 and dMrps23.
  • Conducted genome-wide RNAi screens to identify rescue genes.
  • Investigated the role of the Med8/Tfb4-mtSSB/PolG2/mtDNA-helicase axis in mitochondrial dysfunction and aging.

Main Results:

  • Knockdown of Med8/Tfb4/mtSSB/PolG2/mtDNA-helicase genes rescued mitochondrial defects caused by dMterf4/dMrps23 knockdown.
  • This axis drives mitochondrial DNA (mtDNA) replication outside mitochondria, amplifying cytosolic mtDNA.
  • Amplified cytosolic mtDNA activates the cGAS-Sting-like IMD pathway, mediating disease effects.
  • The identified axis also contributes to other mitochondrial gene defect-induced dysfunctions and aging in Drosophila.

Conclusions:

  • The Med8/Tfb4-mtSSB/PolG2/mtDNA-helicase axis mediates mitochondrial defect effects by promoting extramitochondrial mtDNA replication.
  • Dysfunction of this axis presents a potential therapeutic target for mitochondrial and age-related diseases.
Keywords:
Biological sciencesMolecular biologyMolecular geneticsMolecular interaction

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