A NOVEL MITOCHONDRIAL-DNA POINT MUTATION IN THE TRNA(ILE) GENE IS ASSOCIATED WITH PROGRESSIVE EXTERNAL OPHTALMOPLEGIA

We report a new mutation, a T --> C transition at nt.4285 in the mitoc hondrial tRNA(Ile) gene, in a sporadic case of progressive external op htalmoplegia (PEO) and ragged-red fibers (RRF). The mutation, involvin g 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 i mportance of performing mtDNA studies in PEO patients preferentially o n muscle rather than blood, which could give false negative results. O ther mutations in the tRNA(Ile) gene associated with different phenoty pes have been previously reported. Thus, tRNA(Ile) gene is confirmed t o be another ''hot spot'' region for mtDNA mutations. (C) 1996 Academi c Press, Inc.