Molecular genetical analysis of human mitochondrial tRNA abnormality.

我们报告了在临床上和病理上定义为Leigh综合征（LS）的四代家族的形态学，生化和分子遗传学发现，该家族在线粒体tRNALeu （UUR）基因的核苷酸位置3243 （A3242G）上有a到g的转变。症状并不局限于中枢神经系统和肌肉：最严重的特征是LS合并心肌病（CM），其他严重的特征是线粒体肌病、脑病、乳酸酸中毒和卒中样发作（MELAS）或非胰岛素依赖型糖尿病（NIDDM），较轻的特征是肌肉无力、易疲劳和身材矮小，没有危及生命的症状。一个3岁的软瘫婴儿在10岁时死于心力衰竭。肌肉活组织检查病理上显示红纤维（RRF），分散的细胞色素c氧化酶（COX）阴性纤维和强烈的SDH反应血管（ssv），生化上显示复合物I + IV缺乏。线粒体DNA （mtDNA）分析显示，在骨骼肌、肝脏、心脏、肾脏和大脑等各种组织中，这种突变的比例很高（约为90%）。肌肉单纤维PCR分析显示，RRF-COX阴性肌纤维突变百分率为95.6(]SY.+-。[)1.7，平均值为(]SY.+-。[)SD)显著高于RRF-COX阳性纤维（91.6(]SY.+- .[)2.9）和非RRF-COX阳性纤维（89.2(]SY.+- .[)3.3）。上述结果表明，LS表型是氧化磷酸化（OXPHOS）基因严重缺陷的最终常见结果。2)我们报告一例Leigh病患者线粒体tRNALeu （UUR）基因发生A3243G突变。肌肉中的RNA分析显示，含有16S rRNA序列的多顺反子RNA前体RNA 19、tRNALeu （UUR）和ND1的稳态水平持续增加。上述发现提示异常RNA加工可能在具有该突变的人类疾病的发病机制中起重要作用。3)为了解线粒体tRNALeu （UUR）基因突变在糖尿病儿童中的流行情况，我们在日本筛选了115例发病年龄在15岁以下的糖尿病患者。115例患者中，胰岛素依赖型糖尿病（IDDM） 92例，非胰岛素依赖型糖尿病（NIDDM） 21例，糖耐量异常2例。所有患者均未出现感音神经性听力损失的迹象，没有身材矮小，也没有其他提示线粒体疾病的症状。1例IDDM患者在线粒体tRNALeu （UUR）基因（A3243G） 3243位发现A到G置换，但该突变在该家族中未表现出母系遗传。在我们的研究中，A3242G突变在这些糖尿病儿童中的患病率为0.89%，表明该突变是儿童糖尿病病因的重要因素。少

We report the morphological, biochemical, and molecular genetic findings in a four-generation family with clinically and pathologically defined Leigh syndrome (LS) having an A-to-G transition at the nucleotide position 3243 (A3242G) in the mitochondrial tRNALeu (UUR) gene. The symptoms were not restricted to the CNS and muscle : the most severe features being LS with cardiomyopathy (CM), other severe features being mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) or non-insulin dependent diabetes mellitus (NIDDM), and milder features being muscle weakness, easy fatiguability and short stature without life-threatening symptoms. A 3-yewr-old floppy infant was died at the age of 10 years by cardiac failure. A muscle biopsy had revealed ragged-red fibers (RRF), scattered cytochrome c oxidase (COX) negative fibers and strongly SDH reactive vessels (SSVs), pathologically, and complex I plus IV deficiency, biochemically. Mitochondrial DNA (mtDNA) analys … More is in various tissues-including skeletal muscle, liver, heart, kidney and brain-showed a high percentage (>90%) of this mutation. Single fiber PCR analysis of muscle revealed that the percentage of mutation in muscle fibers with RRF-COX nagative (95.6(]SY.+-。[)1.7, mean(]SY.+-。[)SD) was significantly higher than that in fibers with RRF-COX positive (91.6(]SY.+-。[)2.9), and that with the non-RRF-COX positive (89.2(]SY.+-。[)3.3). The above findings suggested that the LS phenotype was a final common outcome for severe defect in the oxidative phosphorylation (OXPHOS) genes. 2) We report a patient with Leigh disease Having an A3243G mutation in the mitochondrial tRNALeu (UUR) gene. RNA analysis in muscle had shown a consistent increase in the steady state levels of RNA 19, polycistronic RNA precursor containing sequence for 16S rRNA,tRNALeu (UUR) and ND1. The above findings suggested that abnormal RNA processing may play an important role in the pathogenesis of human disease having this mutation.3) To investigate the prevalence of mitochondrial tRNALeu (UUR) gene mutation in diabetic children, we screened 115 diabetic patients in Japan, whose age at onset was under 15 years. Among 115 patients, 92 were diagnosed with insulin dependent diabetes mellitus (IDDM), 21 with non-insulin dependent diabetes mellitus (NIDDM), and 2 with abnormal glucose intolerance. All patients showed no sign of sensorineural hearing loss, no short stature, and no other symptom suggesting any mitochandrial disease. One IDDM patient was found to have an A to G substitution at position 3243 of mitochondrial tRNALeu (UUR) gene (A3243G), however this mutation did not demonstrate maternal inheritance in this family. In our study, the prevalence of the A3242G mutation among these diabetic children was 0.89%, suggesting that this mutation was a significant factor in the etiology of diabetes mellitus in children. Less