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Neuromuscul Disord. 2010 Mar;20(3):204-6. doi: 10.1016/j.nmd.2010.01.006. Epub 2010 Feb 10.

A novel mutation in the tRNAIle gene (MTTI) affecting the variable loop in a patient with chronic progressive external ophthalmoplegia (CPEO).

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Department of Neurology, Columbia University Medical Center, New York, NY 10032, USA.


We describe a 62-year-old woman with chronic progressive external ophthalmoplegia (CPEO), multiple lipomas, diabetes mellitus, and a novel mitochondrial DNA (mtDNA) mutation at nucleotide 4302 (4302A>G) of the tRNA(Ile) gene (MTTI). This is the first mutation at position 44 in the variable loop (V loop) of any mitochondrial tRNA. The muscle biopsy revealed 10% ragged-red/ragged-blue fibers and 25% cytochrome c oxidase (COX)-deficient fibers. No deletions or duplications were detected by Southern blot analysis. The 4302A>G transition was present only in the patient's muscle and single-fiber analysis revealed significantly higher levels of the mutation in COX-deficient than in normal fibers. Like tRNA(Leu(UUR)), tRNA(Ile) appears to be a "hot spot" for mtDNA mutations causing CPEO.

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