Intra-mitochondrial Methylation Deficiency Due to Mutations in SLC25A26

Am J Hum Genet. 2015 Nov 5;97(5):761-8. doi: 10.1016/j.ajhg.2015.09.013. Epub 2015 Oct 29.


S-adenosylmethionine (SAM) is the predominant methyl group donor and has a large spectrum of target substrates. As such, it is essential for nearly all biological methylation reactions. SAM is synthesized by methionine adenosyltransferase from methionine and ATP in the cytoplasm and subsequently distributed throughout the different cellular compartments, including mitochondria, where methylation is mostly required for nucleic-acid modifications and respiratory-chain function. We report a syndrome in three families affected by reduced intra-mitochondrial methylation caused by recessive mutations in the gene encoding the only known mitochondrial SAM transporter, SLC25A26. Clinical findings ranged from neonatal mortality resulting from respiratory insufficiency and hydrops to childhood acute episodes of cardiopulmonary failure and slowly progressive muscle weakness. We show that SLC25A26 mutations cause various mitochondrial defects, including those affecting RNA stability, protein modification, mitochondrial translation, and the biosynthesis of CoQ10 and lipoic acid.

Keywords: S-adenosylmethionine; SAM; SLC25A26; methylation; mitochondria; mitochondrial dysfunction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Transport Systems / genetics*
  • Calcium-Binding Proteins / genetics*
  • Child, Preschool
  • DNA Methylation*
  • Female
  • Humans
  • Male
  • Mitochondrial Diseases / genetics*
  • Mitochondrial Diseases / pathology*
  • Molecular Sequence Data
  • Muscle Weakness / genetics*
  • Muscle Weakness / pathology
  • Mutation / genetics*
  • Pedigree
  • Prognosis
  • RNA Stability
  • S-Adenosylmethionine / metabolism*
  • Sequence Homology, Amino Acid
  • Thioctic Acid / metabolism
  • Ubiquinone / analogs & derivatives
  • Ubiquinone / metabolism


  • Amino Acid Transport Systems
  • Calcium-Binding Proteins
  • SLC25A26 protein, human
  • Ubiquinone
  • Thioctic Acid
  • S-Adenosylmethionine
  • coenzyme Q10