Analysis of mitochondrial DNA mutations : point mutations.

Since the first demonstration that mutations of the mitochondrial genome were associated with human disease, more than 100 pathological mitochondrial DNA (mtDNA) defects have been characterized in patients with a broad spectrum of clinical manifestations (1). Single-point mutations, involving either protein-encoding genes or more commonly RNA (rRNA and tRNA) genes, represent a substantial proportion (more than one third) of the pathogenic mtDNA mutations described in the literature, and this number is steadily increasing (2, 3). Although some of the more common mtDNA point mutations can be screened using simple polymerase chain reaction (PCR)-based techniques (e.g., restriction digest analysis), an increasing number of pathological point mutations are identified only when large-scale sequencing of either all 22 tRNA genes or the whole mitochondrial genome is performed (4-7).