PDF(Pubmed)
Abstract：
BACKGROUND: MT-ATP6 is a mitochondrial gene which encodes for the intramembrane subunit 6 (or A) of the mitochondrial ATP synthase, also known asl complex V, which is involved in the last step of oxidative phosphorylation to produce cellular ATP through aerobic metabolism. Although classically associated with the NARP syndrome, recent evidence highlights an important role of MT-ATP6 pathogenic variants in complicated adult-onset ataxias.
METHODS: We describe two unrelated patients with adult-onset cerebellar ataxia associated with severe optic atrophy and mild cognitive impairment. Whole mitochondrial DNA sequencing was performed in both patients. We employed patients\' primary fibroblasts and cytoplasmic hybrids (cybrids), generated from patients-derived cells, to assess the activity of respiratory chain complexes, oxygen consumption rate (OCR), ATP production and mitochondrial membrane potential.
RESULTS: In both patients, we identified the same novel m.8777 T > C variant in MT-ATP6 with variable heteroplasmy level in different tissues. We identifed an additional heteroplasmic novel variant in MT-ATP6, m.8879G > T, in the patients with the most severe phenotype. A significant reduction in complex V activity, OCR and ATP production was observed in cybrid clones homoplasmic for the m.8777 T > C variant, while no functional defect was detected in m.8879G > T homoplasmic clones. In addition, fibroblasts with high heteroplasmic levelsof m.8777 T > C variant showed hyperpolarization of mitochondrial membranes.
CONCLUSIONS: We describe a novel pathogenic mtDNA variant in MT-ATP6 associated with adult-onset ataxia, reinforcing the value of mtDNA screening within the diagnostic workflow of selected patients with late onset ataxias.
METHODS: We describe two unrelated patients with adult-onset cerebellar ataxia associated with severe optic atrophy and mild cognitive impairment. Whole mitochondrial DNA sequencing was performed in both patients. We employed patients\' primary fibroblasts and cytoplasmic hybrids (cybrids), generated from patients-derived cells, to assess the activity of respiratory chain complexes, oxygen consumption rate (OCR), ATP production and mitochondrial membrane potential.
RESULTS: In both patients, we identified the same novel m.8777 T > C variant in MT-ATP6 with variable heteroplasmy level in different tissues. We identifed an additional heteroplasmic novel variant in MT-ATP6, m.8879G > T, in the patients with the most severe phenotype. A significant reduction in complex V activity, OCR and ATP production was observed in cybrid clones homoplasmic for the m.8777 T > C variant, while no functional defect was detected in m.8879G > T homoplasmic clones. In addition, fibroblasts with high heteroplasmic levelsof m.8777 T > C variant showed hyperpolarization of mitochondrial membranes.
CONCLUSIONS: We describe a novel pathogenic mtDNA variant in MT-ATP6 associated with adult-onset ataxia, reinforcing the value of mtDNA screening within the diagnostic workflow of selected patients with late onset ataxias.
摘要：
背景：MT-ATP6是一种线粒体基因，编码线粒体ATP合酶的膜内亚基6（或A），也被称为asl复杂V，参与氧化磷酸化的最后一步，通过有氧代谢产生细胞ATP。虽然传统上与NARP综合征相关，最近的证据强调MT-ATP6致病变异体在复杂的成人发作性共济失调中的重要作用.
方法：我们描述了两名成人发病小脑共济失调并伴有严重视神经萎缩和轻度认知障碍的无关患者。在两个患者中进行完整线粒体DNA测序。我们采用了患者的原代成纤维细胞和胞质杂种（cybrids），从患者来源的细胞产生，为了评估呼吸链复合物的活性，耗氧率（OCR），ATP产生和线粒体膜电位。
结果：在两个患者中，我们在MT-ATP6中鉴定了相同的新型m.8777T>C变体，在不同组织中具有可变的异质体水平。我们在MT-ATP6中鉴定了一个额外的异质新变体，m.8879G>T，在表型最严重的患者中。复合物V活性显著降低，在m.8777T>C变体的同质杂种克隆中观察到OCR和ATP的产生，而在m.8879G>T同质克隆中未检测到功能缺陷。此外,具有m.8777T>C变体的高异质水平的成纤维细胞显示线粒体膜超极化。
结论：我们描述了与成人共济失调相关的MT-ATP6中一种新的致病性mtDNA变异体，在选定的晚发性共济失调患者的诊断工作流程中加强mtDNA筛查的价值。
方法：我们描述了两名成人发病小脑共济失调并伴有严重视神经萎缩和轻度认知障碍的无关患者。在两个患者中进行完整线粒体DNA测序。我们采用了患者的原代成纤维细胞和胞质杂种（cybrids），从患者来源的细胞产生，为了评估呼吸链复合物的活性，耗氧率（OCR），ATP产生和线粒体膜电位。
结果：在两个患者中，我们在MT-ATP6中鉴定了相同的新型m.8777T>C变体，在不同组织中具有可变的异质体水平。我们在MT-ATP6中鉴定了一个额外的异质新变体，m.8879G>T，在表型最严重的患者中。复合物V活性显著降低，在m.8777T>C变体的同质杂种克隆中观察到OCR和ATP的产生，而在m.8879G>T同质克隆中未检测到功能缺陷。此外,具有m.8777T>C变体的高异质水平的成纤维细胞显示线粒体膜超极化。
结论：我们描述了与成人共济失调相关的MT-ATP6中一种新的致病性mtDNA变异体，在选定的晚发性共济失调患者的诊断工作流程中加强mtDNA筛查的价值。
