Mitochondrial encephalomyopathy associated with a novel mutation in the mitochondrial tRNA(leu)(UUR) gene (A3243T).
We report a new mutation, an A-->T transition at nt 3243 in the mitochondrial tRNA(leu)(UUR) gene, in a 9-year-old girl who presented with muscle weakness of 3 years duration complicated by rapidly progressive encephalopathy. In muscle, the activity of the mitochondrial respiratory chain complexes I, III, and IV was markedly reduced. The mutation, involving a highly conserved base pair in the dihydrouridine loop, was heteroplasmic in muscle (81.4%), skin (69.3%), and blood (13.8%) and was not present in blood of 50 healthy individuals. The mitochondrial 3243 base is a "hot spot" for mutations; an A-->G transition at this position is found in a high proportion in most MELAS patients. Since the A-->T transition creates a new recognition site for the restriction enzyme TspRI, both ApaI and TspRI should be used to exclude a mutation at nt 3243.
Shaag
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A
Metabolic Disease Unit, Shaare-Zedek Medical Center, Jerusalem, Israel.
Saada
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Steinberg
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Navon
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Elpeleg
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ON
D001483:Base Sequence; D002648:Child; D004262:DNA Restriction Enzymes; D004272:DNA, Mitochondrial / Q000235:genetics; D015252:Deoxyribonucleases, Type II Site-Specific; D004579:Electron Transport; D005260:Female; D006801:Humans; D017241:MELAS Syndrome / Q000175:diagnosis / Q000235:genetics; D008931:Mitochondria, Muscle / Q000378:metabolism; D017237:Mitochondrial Encephalomyopathies / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism; D017354:Point Mutation; D012356:RNA, Transfer, Leu / Q000235:genetics*
D004272:DNA, Mitochondrial; D012356:RNA, Transfer, Leu; D004262:DNA Restriction Enzymes; D015252:Deoxyribonucleases, Type II Site-Specific; C038485:GGGCCC-specific type II deoxyribonucleases