Inserm U1081, CNRS UMR7284, IRCAN, CHU de Nice, Medicine School, Université Côte d'Azur, 28 av de Valombrose, 06107, Nice Cedex 2, France.
Inserm U1065, C3M, Université Côte d'Azur, Nice, France.
Acta Neuropathol. 2019 Jul;138(1):123-145. doi: 10.1007/s00401-019-01988-z. Epub 2019 Mar 14.
Recently, we provided genetic basis showing that mitochondrial dysfunction can trigger motor neuron degeneration, through identification of CHCHD10 encoding a mitochondrial protein. We reported patients, carrying the p.Ser59Leu heterozygous mutation in CHCHD10, from a large family with a mitochondrial myopathy associated with motor neuron disease (MND). Rapidly, our group and others reported CHCHD10 mutations in amyotrophic lateral sclerosis (ALS), frontotemporal dementia-ALS and other neurodegenerative diseases. Here, we generated knock-in (KI) mice, carrying the p.Ser59Leu mutation, that mimic the mitochondrial myopathy with mtDNA instability displayed by the patients from our original family. Before 14 months of age, all KI mice developed a fatal mitochondrial cardiomyopathy associated with enhanced mitophagy. CHCHD10 mice also displayed neuromuscular junction (NMJ) and motor neuron degeneration with hyper-fragmentation of the motor end plate and moderate but significant motor neuron loss in lumbar spinal cord at the end stage of the disease. At this stage, we observed TDP-43 cytoplasmic aggregates in spinal neurons. We also showed that motor neurons differentiated from human iPSC carrying the p.Ser59Leu mutation were much more sensitive to Staurosporine or glutamate-induced caspase activation than control cells. These data confirm that mitochondrial deficiency associated with CHCHD10 mutations can be at the origin of MND. CHCHD10 is highly expressed in the NMJ post-synaptic part. Importantly, the fragmentation of the motor end plate was associated with abnormal CHCHD10 expression that was also observed closed to NMJs which were morphologically normal. Furthermore, we found OXPHOS deficiency in muscle of CHCHD10 mice at 3 months of age in the absence of neuron loss in spinal cord. Our data show that the pathological effects of the p.Ser59Leu mutation target muscle prior to NMJ and motor neurons. They likely lead to OXPHOS deficiency, loss of cristae junctions and destabilization of internal membrane structure within mitochondria at motor end plate of NMJ, impairing neurotransmission. These data are in favor with a key role for muscle in MND associated with CHCHD10 mutations.
最近，我们通过鉴定编码线粒体蛋白的 CHCHD10，提供了线粒体功能障碍可引发运动神经元退行性变的遗传基础。我们报道了一个大型线粒体肌病伴运动神经元病（MND）家系的患者，携带 CHCHD10 上的 p.Ser59Leu 杂合突变。很快，我们小组和其他小组报道了 CHCHD10 突变与肌萎缩侧索硬化症（ALS）、额颞叶痴呆-ALS 和其他神经退行性疾病相关。在这里，我们构建了携带 p.Ser59Leu 突变的敲入（KI）小鼠，模拟了我们原始家系中患者表现出的线粒体肌病和 mtDNA 不稳定性。在 14 个月之前，所有 KI 小鼠均发展为致命的线粒体心肌病，伴有增强的线粒体自噬。CHCHD10 小鼠还表现出神经肌肉接头（NMJ）和运动神经元退行性变，运动终板超片段化，疾病终末期腰椎脊髓中的运动神经元中度但显著丢失。在这个阶段，我们观察到脊髓神经元中的 TDP-43 细胞质聚集物。我们还表明，携带 p.Ser59Leu 突变的人诱导多能干细胞分化的运动神经元对 Staurosporine 或谷氨酸诱导的 caspase 激活比对照细胞更敏感。这些数据证实与 CHCHD10 突变相关的线粒体缺陷可能是 MND 的起源。CHCHD10 在 NMJ 突触后部分高度表达。重要的是，运动终板的碎片化与异常的 CHCHD10 表达有关，这种异常表达也存在于形态正常的 NMJ 附近。此外，我们在 3 个月大的 CHCHD10 小鼠的肌肉中发现 OXPHOS 缺陷，而脊髓中的神经元丢失则不存在。我们的数据表明，p.Ser59Leu 突变的病理效应首先靶向肌肉，然后再靶向 NMJ 和运动神经元。它们可能导致 OXPHOS 缺陷、嵴连接丢失和 NMJ 运动终板线粒体内部膜结构的不稳定，从而损害神经传递。这些数据支持肌肉在 CHCHD10 突变相关的 MND 中起关键作用。
