Identification of a novel MT-ND3 variant and restoring mitochondrial function by allotopic expression of MT-ND3 gene

Mitochondrion. 2024 May:76:101858. doi: 10.1016/j.mito.2024.101858. Epub 2024 Mar 2.

Abstract

Mitochondrial diseases are caused by nuclear, or mitochondrial DNA (mtDNA) variants and related co-factors. Here, we report a novel m.10197G > C variant in MT-ND3 in a patient, and two other patients with m.10191 T > C. MT-ND3 variants are known to cause Leigh syndrome or mitochondrial complex I deficiency. We performed the functional analyses of the novel m.10197G > C variant that significantly lowered MT-ND3 protein levels, causing complex I assembly and activity deficiency, and reduction of ATP synthesis. We adapted a previously described re-engineering technique of delivering mitochondrial genes into mitochondria through codon optimization for nuclear expression and translation by cytoplasmic ribosomes to rescue defects arising from the MT-ND3 variants. We constructed mitochondrial targeting sequences along with the codon-optimized MT-ND3 and imported them into the mitochondria. To achieve the goal, we imported codon-optimized MT-ND3 into mitochondria in three patients with m.10197G > C and m.10191 T > C missense variants in the MT-ND3. Nuclear expression of the MT-ND3 gene partially restored protein levels, complex I deficiency, and significant improvement of ATP production indicating a functional rescue of the mutant phenotype. The codon-optimized nuclear expression of mitochondrial protein and import inside the mitochondria can supplement the requirements for ATP in energy-deficient mitochondrial disease patients.

Keywords: Allotopic expression; Codon-optimization; Leigh Syndrome; MT-ND3; Mitochondrial DNA.

Publication types

  • Research Support, Non-U.S. Gov't
  • Case Reports

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Electron Transport Complex I* / deficiency
  • Electron Transport Complex I* / genetics
  • Electron Transport Complex I* / metabolism
  • Female
  • Humans
  • Leigh Disease / genetics
  • Leigh Disease / metabolism
  • Male
  • Mitochondria* / genetics
  • Mitochondria* / metabolism
  • Mitochondrial Diseases* / genetics
  • Mitochondrial Diseases* / metabolism
  • Mutation, Missense

Substances

  • MT-ND3 protein, human
  • Electron Transport Complex I
  • Adenosine Triphosphate

Supplementary concepts

  • Mitochondrial complex I deficiency