Heteroplasmic mutant load differences in mitochondrial DNA-associated Leigh syndrome

  • Ji-Hoon Na
    Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea
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  • Young-Mock Lee
    Correspondence: Young-Mock Lee, MD, PhD, Department of Pediatrics, Yonsei University College of Medicine, Gangnam Severance Hospital, 211 Eonju-ro, Gangnam-gu, Seoul 135-720, Korea. Phone: +82-2-2019-3354, Fax: +82-2-2019-4881.
    Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea

    Epilepsy Research Institute, Yonsei University College of Medicine, Seoul, Korea
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      • Mutant load varies significantly in patients with mtDNA-associated Leigh Syndrome
      • MT-ATP6, MT-ND3, and MT-ND5 are the most common mutations
      • MT-ATP6 had a significantly higher mutant load than that of MT-ND3 and MT-ND5
      • Distribution of the heteroplasmic mutant load depends on the mutated gene



      Mitochondrial DNA (mtDNA)-associated Leigh syndrome is influenced by mutant pathogenicity and corresponding heteroplasmic loads; however, the manner in which heteroplasmic mutant load affects patient phenotypes and the relationship between mutant types and heteroplasmic mutant loads remain unknown.


      We aimed to investigate the distribution of the mutant load of different mtDNA mutations in a single-center cohort.


      We used next-generation sequencing to confirm mtDNA mutations in 31 patients with Leigh syndrome. Subsequently, we counted the number of mtDNA reads to quantitatively analyze the heteroplasmic mutant load and categorize the patients according to the mtDNA mutations they harbored. Confirmed cases of mtDNA-associated Leigh syndrome were classified according to the mutations observed in 6 genes and 10 nucleotides.


      Of the 31 patients with Leigh syndrome, 27 harbored known pathogenic mutations. We discovered that MT-ATP6 was the most commonly mutated gene (n = 13 patients), followed by MT-ND3 (n = 7) and MT-ND5 (n = 4). MT-ATP6 had a significantly higher mutant load than MT-ND3 and MT-ND5 (p < 0.001, each). By contrast, MT-ND5 had a significantly lower mutant load than MT-ND3 (p = 0.007). Notably, the mutation loads varied significantly among patients carrying the MT-ATP6, MT-ND3, and MT-ND5 mutations.


      Our study illustrated the heteroplasmic diversity and phenotypic expression threshold of mutated mitochondrial genes in mtDNA-associated Leigh syndrome. The results provide promising insights into the genotype–phenotype correlation in mtDNA-associated Leigh syndrome that are expected to guide the development of tailored treatments for Leigh syndrome.


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