title: The identification of mitochondrial DNA variants in glioblastoma multiforme.
abstract: BACKGROUND
  Mitochondrial DNA (mtDNA) encodes key proteins of the electron transfer chain (ETC), which produces ATP through oxidative phosphorylation (OXPHOS) and is essential for cells to perform specialised functions. Tumor-initiating cells use aerobic glycolysis, a combination of glycolysis and low levels of OXPHOS, to promote rapid cell proliferation and tumor growth. Glioblastoma multiforme (GBM) is an aggressively malignant brain tumor and mitochondria have been proposed to play a vital role in GBM tumorigenesis.
  
  
  RESULTS
  Using next generation sequencing and high resolution melt analysis, we identified a large number of mtDNA variants within coding and non-coding regions of GBM cell lines and predicted their disease-causing potential through in silico modeling. The frequency of variants was greatest in the D-loop and origin of light strand replication in non-coding regions. ND6 was the most susceptible coding gene to mutation whilst ND4 had the highest frequency of mutation. Both genes encode subunits of complex I of the ETC. These variants were not detected in unaffected brain samples and many have not been previously reported. Depletion of HSR-GBM1 cells to varying degrees of their mtDNA followed by transplantation into immunedeficient mice resulted in the repopulation of the same variants during tumorigenesis. Likewise, de novo variants identified in other GBM cell lines were also incorporated. Nevertheless, ND4 and ND6 were still the most affected genes. We confirmed the presence of these variants in high grade gliomas.
  
  
  CONCLUSIONS
  These novel variants contribute to GBM by rendering the ETC. partially dysfunctional. This restricts metabolism to anaerobic glycolysis and promotes cell proliferation.
authors.forename: Ka Yu
authors.initials: KY
authors.lastname: Yeung
authors.forename: Adam
authors.initials: A
authors.lastname: Dickinson
authors.forename: Jacqueline F
authors.initials: JF
authors.lastname: Donoghue
authors.forename: Galina
authors.initials: G
authors.lastname: Polekhina
authors.forename: Stefan J
authors.initials: SJ
authors.lastname: White
authors.forename: Dimitris K
authors.initials: DK
authors.lastname: Grammatopoulos
authors.forename: Matthew
authors.initials: M
authors.lastname: McKenzie
authors.forename: Terrance G
authors.initials: TG
authors.lastname: Johns
authors.affiliation: Mitochondrial Genetics Group, Centre for Genetic Diseases, Monash Institute of Medical Research, Monash University, 27-31 Wright Street, Clayton, Victoria 3168, Australia. justin.stjohn@monash.edu.
authors.forename: Justin C
authors.initials: JC
authors.lastname: St John
mesh_terms: D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D001921:Brain; D001932:Brain Neoplasms / Q000235:genetics* / Q000473:pathology*; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology; D014644:Genetic Variation / Q000235:genetics*; D005909:Glioblastoma / Q000235:genetics* / Q000473:pathology*; D006019:Glycolysis / Q000187:drug effects; D064593:Heterografts; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D051379:Mice; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D058953:Neural Stem Cells / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects; D016047:Zalcitabine / Q000494:pharmacology
chemical_list: D000963:Antimetabolites; D004272:DNA, Mitochondrial; D016047:Zalcitabine; D025261:Mitochondrial Proton-Translocating ATPases