Marked decrease of mitochondrial DNA with multiple deletions in a patient with familial mitochondrial myopathy.

Muscle mitochondrial DNA (mtDNA) from a patient with mitochondrial myopathy was examined by Southern blotting. Her family history suggests autosomal dominant inheritance of this disorder. In contrast to other cases of this myopathy that are associated with a compensatory increase of mitochondria, in this patient, the content of mtDNA was markedly decreased (15% of controls), whereas protein of the ATP synthase beta-subunit was not decreased appreciably as judged by Western blotting. In addition, the mitochondrial DNA had multiple deletions, which were located between the replication origins of the heavy strand and light strand.