Delgado Thomas, Petralia Ronald S, Freeman David W, Sedlacek Miloslav, Wang Ya-Xian, Brenowitz Stephan D, Sheu Shu-Hsien, Gu Jeffrey W, Kapogiannis Dimitrios, Mattson Mark P, Yao Pamela J
Laboratory of Neurosciences, NIA/NIH, Baltimore, Maryland 21224, USA.
Advanced Imaging Core, NIDCD/NIH, Bethesda, Maryland 20892, USA.
Biol Open. 2019 Aug 1;8(8):bio044834. doi: 10.1242/bio.044834.
Serial-section electron microscopy such as FIB-SEM (focused ion beam scanning electron microscopy) has become an important tool for neuroscientists to trace the trajectories and global architecture of neural circuits in the brain, as well as to visualize the 3D ultrastructure of cellular organelles in neurons. In this study, we examined 3D features of mitochondria in electron microscope images generated from serial sections of four regions of mouse brains: nucleus accumbens (NA), hippocampal CA1, somatosensory cortex and dorsal cochlear nucleus (DCN). We compared mitochondria in the presynaptic terminals to those in the postsynaptic/dendritic compartments, and we focused on the shape and size of mitochondria. A common feature of mitochondria among the four brain regions is that presynaptic mitochondria generally are small and short, and most of them do not extend beyond presynaptic terminals. In contrast, the majority of postsynaptic/dendritic mitochondria are large and many of them spread through significant portions of the dendrites. Comparing among the brain areas, the cerebral cortex and DCN have even larger postsynaptic/dendritic mitochondria than the NA and CA1. Our analysis reveals that mitochondria in neurons are differentially sized and arranged according to their subcellular locations, suggesting a spatial organizing principle of mitochondria at the synapse.
诸如聚焦离子束扫描电子显微镜（FIB-SEM）之类的连续切片电子显微镜已成为神经科学家追踪大脑中神经回路轨迹和整体结构，以及可视化神经元细胞器三维超微结构的重要工具。在本研究中，我们检查了从小鼠大脑四个区域（伏隔核（NA）、海马CA1、躯体感觉皮层和背侧耳蜗核（DCN））的连续切片生成的电子显微镜图像中线粒体的三维特征。我们比较了突触前终末中的线粒体与突触后/树突区室中的线粒体，并着重研究了线粒体的形状和大小。四个脑区线粒体的一个共同特征是，突触前线粒体通常较小且较短，并且大多数不会延伸到突触前终末之外。相比之下，大多数突触后/树突线粒体较大，并且其中许多分布在树突的大部分区域。在脑区之间进行比较时，大脑皮层和DCN的突触后/树突线粒体比NA和CA1的更大。我们的分析表明，神经元中的线粒体根据其亚细胞位置大小不同且排列方式各异，这表明突触处线粒体存在空间组织原则。
