Analysis of the trinucleotide CAG repeat from the human mitochondrial DNA polymerase gene in healthy and diseased individuals

Anja Rovio, Valeria Tiranti, Amy L. Bednarz, Anu Suomalainen, Johannes N. Spelbrink, Nicolas Lecrenier, Atle Melberg, Massimo Zeviani, Joanna Poulton, Françoise Foury, Howard T. Jacobs

Research output: Contribution to journalArticlepeer-review


The human nuclear gene (POLG) for the catalytic subunit of mitochondrial DNA polymerase (DNA polymerase γ) contains a trinucleotide CAG microsatellite repeat within the coding sequence. We have investigated the frequency of different repeat-length alleles in populations of diseased and healthy individuals. The predominant allele of 10 CAG repeats was found at a very similar frequency (approximately 88%) in both Finnish and ethnically mixed population samples, with homozygosity close to the equilibrium prediction. Other alleles of between 5 and 13 repeat units were detected, but no larger, expanded alleles were found. A series of 51 British myotonic dystrophy patients showed no significant variation from controls, indicating an absence of generalised CAG repeat instability. Patients with a variety of molecular lesions in mtDNA, including sporadic, clonal deletions, maternally inherited point mutations, autosomally transmitted mtDNA depletion and autosomal dominant multiple deletions showed no differences in POLG trinucleotide repeat-length distribution from controls. These findings rule out POLG repeat expansion as a common pathogenic mechanism in disorders characterised by mitochondrial genome instability.

Original languageEnglish
Pages (from-to)140-146
Number of pages7
JournalEuropean Journal of Human Genetics
Issue number2
Publication statusPublished - Feb 1999


  • Deletions
  • DNA polymerase
  • Microsatellite
  • Mitochondrial DNA
  • Mitochondrial myopathy
  • Myotonic dystrophy
  • Polyglutamine tract
  • Progressive external ophthalmoplegia
  • Trinucleotide repeat

ASJC Scopus subject areas

  • Genetics(clinical)


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