Three-dimensional analysis of somatic mitochondrial dynamics in fission-deficient injured motor neurons using FIB/SEM
Three-dimensional analysis of somatic mitochondrial dynamics in fission-deficient injured motor neurons using FIB/SEM
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DOI：
10.1002/cne.24213
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发表时间：
2017-08-01
影响因子：
2.5
通讯作者：
Kiyama, Hiroshi
中科院分区：
文献类型：
--
作者：
Tamada, Hiromi;Kiryu-Seo, Sumiko;Kiyama, Hiroshi
线粒体通过融合和裂变发生形态变化，从而控制其质量，对神经元功能至关重要。在这项研究中，我们使用聚焦离子束/扫描电子显微镜（FIB/SEM）检查了正常、神经损伤和神经损伤加裂变损伤情况下运动神经元线粒体的三维形态，因为FIB/SEM技术是同时显示整个细胞器和细胞器内结构的强大工具。将动力蛋白相关蛋白1 （Drp1）基因固定的小鼠与神经元损伤特异性Cre驱动小鼠（Atf3:BAC Tg小鼠）杂交，允许损伤神经元特异性地消融Drp1。FIB/SEM分析表明，运动神经元体细胞线粒体形态在神经损伤前后均未发生改变。然而，裂变损伤导致体细胞线粒体显著增大，最初诱导了圆形区域和长管状突起的复杂形态，随后导致突起数量减少和圆形区域进一步增大，最终导致无突起的大球状线粒体。异常线粒体表现出几种降解形态：局部或全部嵴塌陷、空泡化和线粒体自噬。这表明线粒体分裂对于维持受损运动神经元的线粒体完整性至关重要，多种形式的线粒体降解可能加速神经元的降解。
Mitochondria undergo morphological changes through fusion and fission for their quality control, which are vital for neuronal function. In this study, we examined three-dimensional morphologies of mitochondria in motor neurons under normal, nerve injured, and nerve injured plus fission-impaired conditions using the focused ion beam/scanning electron microscopy (FIB/SEM), because the FIB/SEM technology is a powerful tool to demonstrate both 3D images of whole organelle and the intra-organellar structure simultaneously. Crossing of dynamin-related protein 1 (Drp1) gene-floxed mice with neuronal injury-specific Cre driver mice, Atf3:BAC Tg mice, allowed for Drp1 ablation specifically in injured neurons. FIB/SEM analysis demonstrated that somatic mitochondrial morphologies in motor neurons were not altered before or after nerve injury. However, the fission impairment resulted in prominent somatic mitochondrial enlargement, which initially induced complex morphologies with round regions and long tubular processes, subsequently causing a decrease in the number of processes and further enlargement of the round regions, which eventually resulted in big spheroidal mitochondria without processes. The abnormal mitochondria exhibited several degradative morphologies: local or total cristae collapse, vacuolization, and mitophagy. These suggest that mitochondrial fission is crucial for maintaining mitochondrial integrity in injured motor neurons, and multiple forms of mitochondria degradation may accelerate neuronal degradation.