A COMMON MITOCHONDRIAL-DNA MUTATION IN THE TRANSFER RNALYS OF PATIENTS WITH MYOCLONUS EPILEPSY ASSOCIATED WITH RAGGED-RED FIBERS

  • 1 January 1990
    • journal article
    • research article
    • Vol. 21  (5) , 789-796
Abstract
Nucleotide sequence analyses of muscle mitochondrial DNA (mtDNA) from a patient with myoclonus epilepsy associated with ragged-red fibers (MERRF) revealed 33 single base substitutions, including 23 in coding regions for mitochondrial polypeptides and 10 in non-coding regions, as compared with the normal human mtDNA sequence. Three substitutions, in COI, ND4, and Cytb, would result in amino acid substitutions, which are conserved among species. Of three patients with MERRF, all had an identical A to G base substitution only at nucleotide position 8344 in the t-RNALys region. The substitution was not found in 15 controls. Various degrees of the combined enzymic defects in the oxidative phosphorylation system of mitochondria were found in the MERRF patients. The defects could be explained by altered function or processing of the mutant t-RNALys. This mutation in the t-RNALys is the most probable cause of MERRF.