Mitochondrial cytochrome b gene deletion in Kearns-Sayre syndrome associated with a subclinical type of peripheral neuropathy.
Kearns-Sayre syndrome (KSS) is a progressive neuromuscular disease characterized by ophthalmoplegia, cardiac conduction block, and pigmentary retinopathy associated with abnormal mitochondrial structure and function. Usually mitochondrial DNA (mtDNA) deletions have been associated with Kearns-Sayre syndrome and chronic progressive external ophthalmoplegia. Size and position of the deletions differ markedly among these patients. The present study confirms this observation for a patient with KSS by a muscle and nerve biopsy in which we detected a 1.2 kb mtDNA deletion. The location of the deletion, however, is unusual in this case: its position comprises nucleotides 14952 to 15739. The defect is heteroplasmic and concerns the cytochrome b and tRNA genes. Complex I and IV of the respiratory chain were intact in this case, indicating that below a threshold of tRNA formation, the impaired biosynthesis and membrane integration of one respiratory complex may cause the phenotypical appearance of the KSS syndrome associated with a subclinical neuropathy.
Zanssen
S
S
Institut für Biochemie, Universitätsklinikum, RWTH, Aachen, Germany.
Molnar
M
M
Buse
G
G
Schröder
J M
JM
D000328:Adult; D003573:Cytochrome b Group / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000032:analysis; D005260:Female; D017353:Gene Deletion; D006801:Humans; D007625:Kearns-Sayre Syndrome / Q000235:genetics*; D008854:Microscopy, Electron; D008931:Mitochondria, Muscle / Q000201:enzymology* / Q000235:genetics; D010523:Peripheral Nervous System Diseases / Q000235:genetics*
D003573:Cytochrome b Group; D004272:DNA, Mitochondrial