MOLECULAR BASIS OF MITOCHONDRIAL RNA PROCESSING SYSTEM IN DEVELOPMENTAL TISSUES AND IN MITOCHONDRIAL MYOPATHY.

1)为了了解正常人体组织中RNA 19的稳态水平和MELAS患者中RNA 19的实际水平，我们分析了8例正常人的各种人体组织的总RNA，以及4例MELAS-3243点突变的MELAS患者的肌肉活检。正常组织包括骨骼肌、脑、心、肾、肝、子宫和脾。我们还使用rth逆转录酶PCR-RFLP方法分析了肌肉RNA中RNA 19部分点突变的百分比。我们观察到所有4名MELAS患者（比对照组高5 - 8倍）和1名糖原储存病患者（比对照组高3倍）肌肉中RNA 19水平显著升高。患者肌肉中RNA 19的水平在ND 1总信号的20%至35%之间，显著高于对照肌肉（不到ND 1总信号的4%），这与他们线粒体中分析的突变百分比很好地协调。RNA 19在肌肉、心脏、大脑、肾脏、肝脏、脾脏和子宫等各种人体组织中也被识别，分别占其ND 1信号总量的3.5%、11.6%、13.6%、8.4%、4.2%、1.7%和6.5%。在melas肌肉中观察到的RNA 19的积累似乎是tRNALeu（UUR）突变的特异性，并且与melas的发病机制有关。2)我们研究了5例线粒体DNA （mtDNA）中携带A3243G突变但临床表型不同的无亲缘关系患者在单个肌纤维水平上的突变百分比。1例患者有临床和病理定义的Leigh综合征（LS）， 2例表现为线粒体肌病、脑病、乳酸酸中毒和卒中样发作（MELAS）， 1例表现为进行性眼外麻痹（PEO）， 1例表现为线粒体糖尿病（MDM）。LS患者肌肉中的突变负荷更大（92%），即使在非粗糙红纤维（RRF）中也超过80%，并且RRF的比例也最高。MELAS患者的突变水平和RRF比例较低，PEO和MDM患者的这两个参数更低。这些结果证实了突变负荷和突变在不同细胞和组织中的空间分布的差异是导致疾病表型表达差异的原因。少

1)In order to know the steady-state levels of RNA 19 in normal human tissues and the actual levels of it in MELAS patients, we analyzed the total RNA from various human tissues from 8 normal individuals, and biopsied muscles from 4 MELAS patients having MELAS-3243 point mutation. Normal tissues include skeletal muscle, brain, heart, kidney, liver, uterus, and spleen. We also analyzed the percentage of point mutation in RNA 19 fraction in RNAs from muscles, using rTth reverse transcriptase PCR-RFLP methods. We observed significantly increased levels of RNA 19 in muscles from all 4 MELAS patients (5 - 8 times more than that of the control) and from one patient having glycogen storage disease (3 times more than that of the control). The level of RNA 19 in the patient muscles ranged from 20 to 35% of total ND 1 signal is significantly higher than that of the control muscle (less than 4% of total ND I signal), which is well harmonized with the percentage of mutation analysed in their mitoch … More ondrial DNA from muscles. The RNA 19 is also recognized in various human tissues including muscle, heart, brain, kidney, liver, spleen and uterus, ranging 3.5%, 11.6%, 13 6%, 8.4%, 4.2%, 1.7% and 6.5% of their total ND 1 signal, respectively. This accumulation of RNA 19 observed in MELAS-muscle seems to be specific for the tRNALeu(UUR) mutation and related to the pathogenetic mechanism of MELAS.2)Five unrelated patients harboring the A3243G mutation in the mitochondrial DNA (mtDNA) but presenting with different clinical phenotype were studied for their percentage of mutation at the single muscle fiber levels. One patient had a clinically and pathologically defined Leigh syndrome (LS), two showed mitochondrial myopathy, encephalopathy, lactic acidosis and stroke like episodes (MELAS), another showed progressive external ophthalmoplegia (PEO), and the other showed mitochondrial diabetes mellitus (MDM). The mutation load was greater in the muscle from the patient with LS (92%), who showed more than 80% even in the non-ragged red fibers (RRF) and also presented the highest proportion of RRF.The patients with MELAS had lower mutation levels as well as lower proportion of RRF, and these two parameters were even lower in the PEO and MDM patients. These results confirm the concept that differences in the mutation load and in the spatial distribution of the mutation among different cells and tissues are responsible for the differences in phenotypical expression of the disease. Less