Multiple mitochondrial tRNAMLeu[UUR] mutations associated with infantile myopathy

We have identified a cluster of mitochondrial tRNA^LeuUUR], mutations in a severe case of infantile myopathy. There were A to G transitions found at mtDNA positions 3259, 3261, 3266 and 3268. These point mutations change the anticodon arm and the anticodon UAA, normally found in tRNA^LeuUUR], to UGA which is the one of the tRNAs^SerUCN]. This is the first anticodon alteration described in this tRNA. Another swap straight to the anticodon of tRNA^Pro alone was recently described in a less severe case 1]. Until now infantile myopathies have not been attributed to defined mtDNA alterations. This study reports for the first time mtDNA point mutations causing this early onset of a mitochondrial disorder. The apparent homoplasmy of these mutations and especially the location in the anticodon must be considered lethal, if the child would not have been respirated for 5 years from its birth. (Mol Cell Biochem 174: 231–236, 1997)