Rapid identification of a novel complex I MT-ND3 m.10134C>A mutation in a Leigh syndrome patient

  • PLoS One. 2014 Aug 12;9(8):e104879. doi: 10.1371/journal.pone.0104879.
David K Miller  1 ,  Minal J Menezes  2 ,  Cas Simons  3 ,  Lisa G Riley  4 ,  Sandra T Cooper  5 ,  Sean M Grimmond  1 ,  David R Thorburn  6 ,  John Christodoulou  7 ,  Ryan J Taft  8
Affiliations
  • 1. Queensland Centre for Medical Genomics, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia.
  • 2. Genetic Metabolic Disorders Research Unit, Kids Research Institute, Children's Hospital at Westmead, Sydney, Westmead New South Wales, Australia; Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, Camperdown New South Wales, Australia.
  • 3. Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia.
  • 4. Genetic Metabolic Disorders Research Unit, Kids Research Institute, Children's Hospital at Westmead, Sydney, Westmead New South Wales, Australia.
  • 5. Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, Camperdown New South Wales, Australia; Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, Sydney, New South Wales, Australia.
  • 6. Murdoch Childrens Research Institute and Victorian Clinical Genetics Services, Royal Children's Hospital, Flemington Road, Parkville, Melbourne, Victoria, Australia; Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia.
  • 7. Genetic Metabolic Disorders Research Unit, Kids Research Institute, Children's Hospital at Westmead, Sydney, Westmead New South Wales, Australia; Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, Camperdown New South Wales, Australia; Discipline of Genetic Medicine, Sydney Medical School, University of Sydney, Camperdown, New South Wales, Australia.
  • 8. Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia; Departments of Integrative Systems Biology and Pediatrics, George Washington University School of Medicine, Washington, D.C., United States of America.
PMID: 25118196 DOI: 10.1371/journal.pone.0104879
Abstract

Leigh syndrome (LS) is a rare progressive multi-system neurodegenerative disorder, the genetics of which is frequently difficult to resolve. Rapid determination of the genetic etiology of LS in a 5-year-old girl facilitated inclusion in Edison Pharmaceutical's phase 2B clinical trial of EPI-743. SNP-arrays and high-coverage whole exome Sequencing were performed on the proband, both parents and three unaffected siblings. Subsequent multi-tissue targeted high-depth mitochondrial Sequencing was performed using custom long-range PCR amplicons. Tissue-specific mutant load was also assessed by qPCR. Complex I was interrogated by spectrophotometric enzyme assays and Western Blot. No putatively causal mutations were identified in nuclear-encoded genes. Analysis of low-coverage off-target mitochondrial reads revealed a previously unreported mitochondrial mutation in the proband in MT-ND3 (m.10134C>A, p.Q26K), a Complex I mitochondrial gene previously associated with LS. Targeted investigations demonstrated that this mutation was 1% heteroplasmic in the mother's blood and homoplasmic in the proband's blood, fibroblasts, liver and muscle. Enzyme assays revealed decreased Complex I activity. The identification of this novel LS MT-ND3 variant, the genomics of which was accomplished in less than 3.5 weeks, indicates that rapid genomic approaches may prove useful in time-sensitive cases with an unresolved genetic diagnosis.