Fine mapping of randomly distributed multiple deletions of mitochondrial DNA in a case of chronic progressive external ophthalmoplegia.

Multiple deletions of mitochondrial DNA have been detected by Southern blotting in the skeletal muscle of a 42-year-old woman with chronic progressive external ophthalmoplegia. A PCR method, using several combinations of primers covering the whole mtDNA as well as sequence analysis, disclosed the wide spectrum of these multiple deletions differing in size, location and sequence at the breakpoint junction. Most involved the major region between the two replication origins. However, three deletions affected the minor region and lacked either the light strand origin of replication or the heavy strand promoter. These data suggest an impairment of mtDNA replication leading to illegitimate recombination and extensive damage of mtDNA.