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Most of the mutations causing deficiency of the pyruvate dehydrogenase (PDH) complex are in the X-linked E1 alpha gene. We have developed a rapid screening method for the detection of mutations in this gene using reverse transcription of total RNA, polymerase chain reaction amplification of the whole coding region of the gene and single-strand conformation polymorphism (SSCP) analysis. With this method, we studied eight patients with a PDH complex deficiency, using cultured fibroblasts. In all patients, aberrant SSCP patterns were found and, after sequencing of the corresponding fragments, we were able to identify six new mutations and two mutations already described previously. The mutations are point mutations leading to amino acid substitutions (5) and direct repeat insertions (3). The presence of the mutations was confirmed in genomic fibroblast DNA. The 4 female patients were shown to carry both a normal and a mutated E1 alpha gene.

Various abnormalities in mitochondrial enzyme activities have been found, e.g. in myopathies. In only a restricted number of patients these disturbances can be demonstrated in fibroblasts. This restriction is caused by two facts: 1 some defects, found in muscle tissue, are not expressed in cultured fibroblasts and 2 some mitochondrial enzyme activities are hardly measurable in fibroblasts. Recently, chorionic villi have become important for detecting aberrations in, among others, enzyme activities. Using chorionic villi instead of amnion cells fixes the moment of antenatal diagnosis at an earlier tine. In the case of mitochondrial myopathies it is furthermore important that some enzyme activities can be measured in chorionic villi which can not be determined in fibroblasts. Among them are various oxidoreductases of the respiratory chain. Activity of cytochrome oxidase, pyruvate dehydrogenase complex and citrate synthase can be determined in both chorionic villi and fibroblasts. Control values (in mU/mg protein;mean± SD)in chorionic villi: The possibilities for antenatal diagnosis of mitochondrial myopathies have now clearly been extended.