Molecular pathomechanisms and cell-type-specific disease phenotypes of MELAS caused by mutant mitochondrial tRNA(Trp)

Acta Neuropathol Commun. 2015 Aug 22:3:52. doi: 10.1186/s40478-015-0227-x.

Abstract

Introduction: Numerous pathogenic mutations responsible for mitochondrial diseases have been identified in mitochondrial DNA (mtDNA)-encoded tRNA genes. In most cases, however, the detailed molecular pathomechanisms and cellular pathophysiology of these mtDNA mutations -how such genetic defects determine the variation and the severity of clinical symptoms in affected individuals- remain unclear. To investigate the molecular pathomechanisms and to realize in vitro recapitulation of mitochondrial diseases, intracellular mutant mtDNA proportions must always be considered.

Results: We found a disease-causative mutation, m.5541C>T heteroplasmy in MT-TW gene, in a patient exhibiting mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with multiple organ involvement. We identified the intrinsic molecular pathomechanisms of m.5541C>T. This mutation firstly disturbed the translation machinery of mitochondrial tRNA(Trp) and induced mitochondrial respiratory dysfunction, followed by severely injured mitochondrial homeostasis. We also demonstrated cell-type-specific disease phenotypes using patient-derived induced pluripotent stem cells (iPSCs) carrying ~100 % mutant m.5541C>T. Significant loss of terminally differentiated iPSC-derived neurons, but not their stem/progenitor cells, was detected most likely due to serious mitochondrial dysfunction triggered by m.5541C>T; in contrast, m.5541C>T did not apparently affect skeletal muscle development.

Conclusions: Our iPSC-based disease models would be widely available for understanding the "definite" genotype-phenotype relationship of affected tissues and organs in various mitochondrial diseases caused by heteroplasmic mtDNA mutations, as well as for further drug discovery applications.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Brain / pathology
  • Cell Differentiation / drug effects
  • Cell Differentiation / genetics
  • Cells, Cultured
  • Child
  • Citrate (si)-Synthase / metabolism
  • DNA Mutational Analysis
  • DNA, Mitochondrial / genetics
  • DNA, Mitochondrial / metabolism
  • Humans
  • Induced Pluripotent Stem Cells / drug effects
  • Induced Pluripotent Stem Cells / physiology
  • MELAS Syndrome / genetics*
  • MELAS Syndrome / pathology*
  • Male
  • Membrane Potentials / genetics
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism
  • Mutation / genetics*
  • Myoblasts / metabolism
  • Neurons / physiology
  • RNA, Messenger / metabolism
  • RNA, Transfer, Trp / genetics*
  • Transcription Factors / metabolism

Substances

  • DNA, Mitochondrial
  • Mitochondrial Proteins
  • RNA, Messenger
  • RNA, Transfer, Trp
  • Transcription Factors
  • Adenosine Triphosphate
  • Citrate (si)-Synthase