Single muscle fiber analysis of myoclonus epilepsy with ragged-red fibers

Muscle Nerve. 1998 Apr;21(4):490-7. doi: 10.1002/(sici)1097-4598(199804)21:4<490::aid-mus7>;2-4.


We examined two muscle biopsy specimens from a proband and her mother with myoclonus epilepsy with ragged-red fibers (MERRF), both obtained at an interval of about 10 years, using histochemistry, in situ hybridization, and single-fiber polymerase chain reaction. Total (wild-type and mutant) mitochondrial DNAs (mtDNAs) were greatly increased in ragged-red fibers (RRF) over non-RRF in all muscle specimens analyzed. The proportion of mutant mtDNA was also significantly higher in RRF than in non-RRF. By comparing the first and second muscle biopsied specimens in each patient, we found that while the proportion of RRF, cytochrome coxidase deficient fibers, and mutant DNA in muscle changed over a 10-year period, the proportion of wild-type and mutant mtDNAs in RRF and in non-RRF was similar between the two specimens. These results suggest that the ratio of wild-type to mutant mtDNAs in RRF and non-RRF in MERRF is at a steady state level in each muscle fiber, without replicative advantage of mutant mtDNA.

Publication types

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

MeSH terms

  • Adult
  • DNA, Mitochondrial / genetics
  • DNA, Mitochondrial / metabolism
  • Female
  • Histocytochemistry
  • Humans
  • In Situ Hybridization
  • MERRF Syndrome / genetics
  • MERRF Syndrome / metabolism*
  • Middle Aged
  • Mitochondria, Muscle / metabolism
  • Muscle Fibers, Fast-Twitch / metabolism*
  • Muscle, Skeletal / metabolism*
  • Mutation
  • Polymerase Chain Reaction


  • DNA, Mitochondrial