title: Molecular diagnosis in mitochondrial complex I deficiency using exome sequencing.
abstract: BACKGROUND
  Next generation sequencing has become the core technology for gene discovery in rare inherited disorders. However, the interpretation of the numerous sequence variants identified remains challenging. We assessed the application of exome sequencing for diagnostics in complex I deficiency, a disease with vast genetic heterogeneity.
  
  
  METHODS
  Ten unrelated individuals with complex I deficiency were selected for exome sequencing and sequential bioinformatic filtering. Cellular rescue experiments were performed to verify pathogenicity of novel disease alleles.
  
  
  RESULTS
  The first filter criterion was 'Presence of known pathogenic complex I deficiency variants'. This revealed homozygous mutations in NDUFS3 and ACAD9 in two individuals. A second criterion was 'Presence of two novel potentially pathogenic variants in a structural gene of complex I', which discovered rare variants in NDUFS8 in two unrelated individuals and in NDUFB3 in a third. Expression of wild-type cDNA in mutant cell lines rescued complex I activity and assembly, thus providing a functional validation of their pathogenicity. Using the third criterion 'Presence of two potentially pathogenic variants in a gene encoding a mitochondrial protein', loss-of-function mutations in MTFMT were discovered in two patients. In three patients the molecular genetic correlate remained unclear and follow-up analysis is ongoing.
  
  
  CONCLUSIONS
  Appropriate in silico filtering of exome sequencing data, coupled with functional validation of new disease alleles, is effective in rapidly identifying disease-causative variants in known and new complex I associated disease genes.
authors.affiliation: Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany.
authors.forename: Tobias B
authors.initials: TB
authors.lastname: Haack
authors.forename: Birgit
authors.initials: B
authors.lastname: Haberberger
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Frisch
authors.forename: Thomas
authors.initials: T
authors.lastname: Wieland
authors.forename: Arcangela
authors.initials: A
authors.lastname: Iuso
authors.forename: Matteo
authors.initials: M
authors.lastname: Gorza
authors.forename: Valentina
authors.initials: V
authors.lastname: Strecker
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Graf
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Mayr
authors.forename: Ulrike
authors.initials: U
authors.lastname: Herberg
authors.forename: Julia B
authors.initials: JB
authors.lastname: Hennermann
authors.forename: Thomas
authors.initials: T
authors.lastname: Klopstock
authors.forename: Klaus A
authors.initials: KA
authors.lastname: Kuhn
authors.forename: Uwe
authors.initials: U
authors.lastname: Ahting
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sperl
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Wilichowski
authors.forename: Georg F
authors.initials: GF
authors.lastname: Hoffmann
authors.forename: Marketa
authors.initials: M
authors.lastname: Tesarova
authors.forename: Hana
authors.initials: H
authors.lastname: Hansikova
authors.forename: Jiri
authors.initials: J
authors.lastname: Zeman
authors.forename: Barbara
authors.initials: B
authors.lastname: Plecko
authors.forename: Massimo
authors.initials: M
authors.lastname: Zeviani
authors.forename: Ilka
authors.initials: I
authors.lastname: Wittig
authors.forename: Tim M
authors.initials: TM
authors.lastname: Strom
authors.forename: Markus
authors.initials: M
authors.lastname: Schuelke
authors.forename: Peter
authors.initials: P
authors.lastname: Freisinger
authors.forename: Thomas
authors.initials: T
authors.lastname: Meitinger
authors.forename: Holger
authors.initials: H
authors.lastname: Prokisch
mesh_terms: D019943:Amino Acid Substitution; D042967:Electron Transport Complex I / Q000172:deficiency / Q000235:genetics; D059472:Exome; D015870:Gene Expression; D006801:Humans; D028361:Mitochondrial Diseases / Q000175:diagnosis* / Q000235:genetics*; D009154:Mutation; D009245:NADH Dehydrogenase / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: C113982:NDUFS8 protein, human; D009245:NADH Dehydrogenase; D042967:Electron Transport Complex I