Mutations in the Mitochondrial methionyl-tRNA Synthetase Cause a Neurodegenerative Phenotype in Flies and a Recessive Ataxia (ARSAL) in Humans

PLoS Biol. 2012;10(3):e1001288. doi: 10.1371/journal.pbio.1001288. Epub 2012 Mar 20.

Abstract

An increasing number of genes required for mitochondrial biogenesis, dynamics, or function have been found to be mutated in metabolic disorders and neurological diseases such as Leigh Syndrome. In a forward genetic screen to identify genes required for neuronal function and survival in Drosophila photoreceptor neurons, we have identified mutations in the mitochondrial methionyl-tRNA synthetase, Aats-met, the homologue of human MARS2. The fly mutants exhibit age-dependent degeneration of photoreceptors, shortened lifespan, and reduced cell proliferation in epithelial tissues. We further observed that these mutants display defects in oxidative phosphorylation, increased Reactive Oxygen Species (ROS), and an upregulated mitochondrial Unfolded Protein Response. With the aid of this knowledge, we identified MARS2 to be mutated in Autosomal Recessive Spastic Ataxia with Leukoencephalopathy (ARSAL) patients. We uncovered complex rearrangements in the MARS2 gene in all ARSAL patients. Analysis of patient cells revealed decreased levels of MARS2 protein and a reduced rate of mitochondrial protein synthesis. Patient cells also exhibited reduced Complex I activity, increased ROS, and a slower cell proliferation rate, similar to Drosophila Aats-met mutants.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Ataxia / genetics*
  • Ataxia / metabolism
  • Cell Proliferation
  • Child
  • Child, Preschool
  • Drosophila / enzymology
  • Drosophila / genetics
  • Drosophila / physiology*
  • Drosophila Proteins / genetics*
  • Drosophila Proteins / metabolism
  • Electron Transport
  • Electroretinography / methods
  • Female
  • Gene Expression Regulation, Enzymologic
  • HEK293 Cells
  • Humans
  • Leukoencephalopathies / genetics
  • Leukoencephalopathies / metabolism
  • Longevity
  • Male
  • Methionine-tRNA Ligase / genetics*
  • Methionine-tRNA Ligase / metabolism
  • Middle Aged
  • Mitochondria / enzymology*
  • Mitochondria / genetics
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism
  • Muscles / metabolism
  • Muscles / physiopathology
  • Mutation
  • Neurodegenerative Diseases / genetics*
  • Neurodegenerative Diseases / metabolism
  • Oxidative Phosphorylation
  • Pedigree
  • Phenotype
  • Photoreceptor Cells / metabolism
  • Photoreceptor Cells / pathology
  • Reactive Oxygen Species / metabolism
  • Retina / metabolism
  • Retina / pathology
  • Unfolded Protein Response
  • Young Adult

Substances

  • Drosophila Proteins
  • Mitochondrial Proteins
  • Reactive Oxygen Species
  • Methionine-tRNA Ligase