Distribution and clinical expression of the tRNA(Lys) mutation in mitochondrial DNA in MERRF syndrome.
The distribution and clinical expression of mutant mtDNA with an A-to-G transition at the 8,344th nucleotide position in the tRNA(Lys) gene were studied in different tissues of the probands and relatives in a Taiwanese family with myoclonic epilepsy with ragged-red fibers (MERRF) syndrome. The proportions of mutant mtDNA were 89% to 95% for muscles and 78% to 99% for blood cells in the symptomatic probands except for one who had no mutant mtDNA in the muscles. In asymptomatic maternal relatives, these were 1% to 80% for muscles and 54% to 78% for blood cells. However, there was a lack of correlation between the clinical severity and the proportion of mutant mtDNA. Furthermore, among the maternal relatives studied, some asymptomatic family members had proportions of mutant mtDNA > 80% in muscles and > 53% in blood cells. Although these findings may suggest a threshold effect of mtDNA in MERRF syndrome, clinical manifestations are difficult to predict from the proportions of mutant mtDNA at the tRNA(Lys) gene only.
Huang
C C
CC
Department of Neurology, Chang Gung Memorial Hospital and Medical College, Taipei, Taiwan, ROC.
Chu
N S
NS
Shih
K D
KD
Pang
C Y
CY
Wei
Y H
YH
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004272:DNA, Mitochondrial / Q000032:analysis / Q000235:genetics*; D005260:Female; D006801:Humans; D017243:MERRF Syndrome / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D012357:RNA, Transfer, Lys / Q000235:genetics*
D004272:DNA, Mitochondrial; D012357:RNA, Transfer, Lys