title: Rapid identification of a novel complex I MT-ND3 m.10134C>A mutation in a Leigh syndrome patient.
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.
authors.affiliation: Queensland Centre for Medical Genomics, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia.
authors.forename: David K
authors.initials: DK
authors.lastname: Miller
authors.affiliation: 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.
authors.forename: Minal J
authors.initials: MJ
authors.lastname: Menezes
authors.affiliation: Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia.
authors.forename: Cas
authors.initials: C
authors.lastname: Simons
authors.affiliation: Genetic Metabolic Disorders Research Unit, Kids Research Institute, Children's Hospital at Westmead, Sydney, Westmead New South Wales, Australia.
authors.forename: Lisa G
authors.initials: LG
authors.lastname: Riley
authors.affiliation: 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.
authors.forename: Sandra T
authors.initials: ST
authors.lastname: Cooper
authors.affiliation: Queensland Centre for Medical Genomics, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia.
authors.forename: Sean M
authors.initials: SM
authors.lastname: Grimmond
authors.affiliation: 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.
authors.forename: David R
authors.initials: DR
authors.lastname: Thorburn
authors.affiliation: 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.
authors.forename: John
authors.initials: J
authors.lastname: Christodoulou
authors.affiliation: 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.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Taft
mesh_terms: D019943:Amino Acid Substitution; D001921:Brain / Q000473:pathology; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000235:genetics*; D042967:Electron Transport Complex I / Q000235:genetics* / Q000378:metabolism; D059472:Exome / Q000235:genetics; D005260:Female; D050259:Genes, Mitochondrial; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007888:Leigh Disease / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D010375:Pedigree; D020641:Polymorphism, Single Nucleotide
chemical_list: D004272:DNA, Mitochondrial; D050505:Mutant Proteins; D042967:Electron Transport Complex I; C114961:MT-ND3 protein, human