ENZYMOLOGICAL VERSUS DNA INVESTIGATIONS IN MITOCHONDRIAL (ENCEPHALO-)MYOPATHIES

The molecular basis of most types of deficiency in mitochondrial energy metabolism is still unknown. Application of newly developed DNA technology to the relatively small mtDNA molecule with known base sequence has resulted in the detection of deletions, duplications and point mutations in many patients (Zeviani and Antozzi 1992). However, the relatively large group of patients with disturbance in the respiratory chain has not yet been characterized at the DNA level. Thirteen proteins of the oxidative phosphorylation system are encoded by mitochondrial DNA (mtDNA), which also encodes for the ribosomal and transfer RNA of the organelle. The nuclear genome encodes for the other mitochondrial proteins and regulates the biogenesis of mitochondria (Attardi and Schatz 1988). In the present study we describe the results of mtDNA analysis in 66 patients with clinical symptoms and/or clinical-chemical abnormalities making them suspected of suffering from a mitochondrial (encephalo-)myopathy (Trijbels et al 1988), and whose muscle has been examined biochemically. The added value of the mtDNA studies is evaluated.