A novel mitochondrial DNA point mutation in the tRNAIIe gene is associated with progressive external ophtalmoplegia

We report a new mutation, a T → C transition at nt.4285 in the mitochondrial tRNAIle gene, in a sporadic case of progressive external ophtalmoplegia (PEO) and ragged-red fibers (RRF). The mutation, involving a highly conserved base-pair in the anticodon stem, was detected in high percentages (91%) in muscle, but not in blood. It has never been reported in literature in normal subjects and it was not found in any of 80 controls studied in our laboratory. The absence of the mutation in leukocytes in this case with pure muscle involvement confirms the importance of performing mtDNA studies in PEO patients preferentially on muscle rather than blood, which could give false negative results. Other mutations in the tRNAIle gene associated with different phenotypes have been previously reported. Thus, tRNAIle gene is confirmed to be another "hot spot" region for mtDNA mutations. © 1996 Academic Press, Inc.