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Hum Mol Genet. 1994 Jan;3(1):13-9.

Distribution of wild-type and common deletion forms of mtDNA in normal and respiration-deficient muscle fibers from patients with mitochondrial myopathy.

Author information

  • 1H. Houston Merritt Clinical Research Center for Muscular Dystrophy, Columbia University, New York, NY 10032.

Erratum in

  • Hum Mol Genet 1994 Apr;3(4):687.


We studied the cellular distribution of both deleted (delta) and wild-type (wt) mitochondrial DNAs (mtDNAs) in 'normal' and respiration-deficient muscle fibers from four patients with mitochondrial myopathy. PCR-based methods were used to quantitate both relative and absolute amounts of delta- and wt-mtDNAs in microdissected fiber segments. Although delta-mtDNAs were present in normal fibers (31% +/- 26), their percentages were much higher in affected fibers (95% +/- 2). Absolute levels of delta-mtDNA were also increased in affected fibers, whereas levels of wt-mtDNA were significantly reduced in these fibers. These results indicate that a threshold ratio of delta-/wt-mtDNA must be achieved before an impairment of respiration is observed in muscle. Moreover, the marked reduction in wt-mtDNA observed in affected fibers suggests that absolute amounts of mtDNA may play a role in the pathogenesis of mitochondrial myopathies.

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