Altered mitochondrial function in fibroblasts containing MELAS or MERRF mitochondrial DNA mutations
Altered mitochondrial function in fibroblasts containing MELAS or MERRF mitochondrial DNA mutations
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DOI：
10.1042/bj3180401
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发表时间：
1996-09-01
影响因子：
4.1
通讯作者：
Murphy, MP
中科院分区：
文献类型：
--
作者：
James, AM;Wei, YH;Murphy, MP
许多人类疾病都是由遗传性线粒体DNA突变引起的。其中两种疾病，MELAS（线粒体肌病、脑病、乳酸酸中毒和中风样发作）和MERRF（肌阵挛性癫痫和破碎红纤维），通常是由线粒体DNA编码的tRNA基因的点突变引起的。在这里，我们报告这些突变如何影响原代成纤维细胞培养物中的线粒体功能，这些细胞培养物是从一名MELAS患者和一名MERRF患者建立的，MELAS患者在tRNA（Leu（UUR））基因的核苷酸3243处含有A至G突变，MERRF患者在tRNA（Lys）基因的核苷酸8344处含有A至G突变。线粒体膜电位和呼吸速率显着降低毛地黄皂苷透化MELAS和MERRF成纤维细胞呼吸谷氨酸/苹果酸。在完整的MELAS和MERRF成纤维细胞中发现了线粒体膜电位的类似降低。这些细胞的线粒体含量，估计通过体视学分析的电子显微照片和测量的线粒体标记酶，是类似的控制，MELAS和MERRF细胞。因此，在培养的成纤维细胞中，线粒体tRNA基因的突变导致生物能量不合格的线粒体的组装，而不是其数量的改变。然而，MELAS和MERRF细胞中次级溶酶体和残留体占据的细胞体积大于对照细胞，表明这些细胞中线粒体降解增加。此外，含有线粒体DNA突变的成纤维细胞比对照成纤维细胞大3-4倍。这些研究结果的线粒体疾病的病理学的影响进行了讨论。
A number of human diseases are caused by inherited mitochondrial DNA mutations. Two of these diseases, MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) and MERRF (myoclonic epilepsy and ragged-red fibres), are commonly caused by point mutations to tRNA genes encoded by mitochondrial DNA. Here we report on how these mutations affect mitochondrial function in primary fibroblast cultures established from a MELAS patient containing an A to G mutation at nucleotide 3243 in the tRNA(Leu(UUR)) gene and a MERRF patient containing an A to G mutation at nucleotide 8344 in the tRNA(Lys) gene. Both mitochondrial membrane potential and respiration rate were significantly decreased in digitonin-permeabilized MELAS and MERRF fibroblasts respiring on glutamate/malate. A similar decrease in mitochondrial membrane potential was found in intact MELAS and MERRF fibroblasts. The mitochondrial content of these cells, estimated by stereological analysis of electron micrographs and from measurement of mitochondrial marker enzymes, was similar in control, MELAS and MERRF cells. Therefore, in cultured fibroblasts, mutation of mitochondrial tRNA genes leads to assembly of bioenergetically incompetent mitochondria, not to an alteration in their amount. However, the cell volume occupied by secondary lysosomes and residual bodies in the MELAS and MERRF cells was greater than in control cells, suggesting increased mitochondrial degradation in these cells. In addition, fibroblasts containing mitochondrial DNA mutations were 3-4-fold larger than control fibroblasts. The implications of these findings for the pathology of mitochondrial diseases are discussed.