Nakamura M, Nakano S, Goto Y, Ozawa M, Nagahama Y, Fukuyama H, Akiguchi I, Kaji R, Kimura J
Department of Neurology, Kyoto University Hospital, Japan.
Biochem Biophys Res Commun. 1995 Sep 5;214(1):86-93. doi: 10.1006/bbrc.1995.2260.
We found a new point mutation in the mitochondrial tRNA(Ser(UCN)) gene in a family with MERRF/MELAS overlap syndrome by screening for heteroplasmy by means of chemical cleavage of mismatch (CCM). Our strategy was based on the previous observations that most pathogenic mtDNA mutations in mitochondrial encephalomyopathies are heteroplasmic, whereas almost all neutral mitochondrial polymorphisms are homoplasmic. CCM followed by nucleotide sequencing of the corresponding region of the mitochondrial genome revealed a heteroplasmic mutation at nt 7512 in the tRNA(Ser(UCN)) gene. The 7512 (T to C) mutation disrupts a highly conserved base pair in the acceptor stem, and this mutation was not found in any of 120 normal controls, or in 43 patients with mitochondrial diseases. The proportion of the mutant mtDNA was 93% in muscle, 76 and 87% in the blood of the patients. A family member without apparent neuromuscular symptoms carried less mutant mtDNA. These findings support the view that this mutation is pathogenic in this family. Detection of heteroplasmy by CCM is an efficient means of screening pathogenic mtDNA point mutations.
我们通过错配化学切割法（CCM）筛选异质性，在一个患有肌阵挛性癫痫伴破碎红纤维/线粒体脑肌病伴乳酸血症和卒中样发作（MERRF/MELAS）重叠综合征的家族中发现了线粒体tRNA(Ser(UCN))基因的一个新的点突变。我们的策略基于先前的观察结果，即线粒体脑肌病中大多数致病性线粒体DNA（mtDNA）突变是异质性的，而几乎所有中性线粒体多态性是同质性的。CCM之后对线粒体基因组相应区域进行核苷酸测序，发现在tRNA(Ser(UCN))基因的nt 7512处存在异质性突变。7512（T到C）突变破坏了受体茎中一个高度保守的碱基对，在120名正常对照者以及43名线粒体疾病患者中均未发现此突变。患者肌肉中突变型mtDNA的比例为93%，血液中为76%和87%。一名没有明显神经肌肉症状的家族成员携带的突变型mtDNA较少。这些发现支持了这一突变在该家族中具有致病性的观点。通过CCM检测异质性是筛选致病性mtDNA点突变的有效方法。
