The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron Tomography
Axonal varicosities or swellings are enlarged structures along axon shafts and profoundly affect action potential propagation and synaptic transmission. These structures, which are defined by morphology, are highly heterogeneous and often investigated concerning their roles in neuropathology, but wh...
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MDPI AG
2022-08-01
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| author | Di Ma Binbin Deng Chao Sun David W. McComb Chen Gu |
| author_facet | Di Ma Binbin Deng Chao Sun David W. McComb Chen Gu |
| author_sort | Di Ma |
| collection | DOAJ |
| description | Axonal varicosities or swellings are enlarged structures along axon shafts and profoundly affect action potential propagation and synaptic transmission. These structures, which are defined by morphology, are highly heterogeneous and often investigated concerning their roles in neuropathology, but why they are present in the normal brain remains unknown. Combining confocal microscopy and cryo-electron tomography (Cryo-ET) with in vivo and in vitro systems, we report that non-uniform mechanical interactions with the microenvironment can lead to 10-fold diameter differences within an axon of the central nervous system (CNS). In the brains of adult Thy1-YFP transgenic mice, individual axons in the cortex displayed significantly higher diameter variation than those in the corpus callosum. When being cultured on lacey carbon film-coated electron microscopy (EM) grids, CNS axons formed varicosities exclusively in holes and without microtubule (MT) breakage, and they contained mitochondria, multivesicular bodies (MVBs), and/or vesicles, similar to the axonal varicosities induced by mild fluid puffing. Moreover, enlarged axon branch points often contain MT free ends leading to the minor branch. When the axons were fasciculated by mimicking in vivo axonal bundles, their varicosity levels reduced. Taken together, our results have revealed the extrinsic regulation of the three-dimensional ultrastructures of central axons by the mechanical microenvironment under physiological conditions. |
| first_indexed | 2024-03-09T09:59:36Z |
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| institution | Directory Open Access Journal |
| issn | 2073-4409 |
| language | English |
| last_indexed | 2024-03-09T09:59:36Z |
| publishDate | 2022-08-01 |
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| spelling | doaj.art-8642e2f737b74badb5e2f4e1070332692023-12-01T23:33:27ZengMDPI AGCells2073-44092022-08-011116253310.3390/cells11162533The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron TomographyDi Ma0Binbin Deng1Chao Sun2David W. McComb3Chen Gu4Ohio State Biochemistry Graduate Program, The Ohio State University, Columbus, OH 43210, USACenter for Electron Microscopy and Analysis, The Ohio State University, Columbus, OH 43210, USADepartment of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210, USACenter for Electron Microscopy and Analysis, The Ohio State University, Columbus, OH 43210, USAOhio State Biochemistry Graduate Program, The Ohio State University, Columbus, OH 43210, USAAxonal varicosities or swellings are enlarged structures along axon shafts and profoundly affect action potential propagation and synaptic transmission. These structures, which are defined by morphology, are highly heterogeneous and often investigated concerning their roles in neuropathology, but why they are present in the normal brain remains unknown. Combining confocal microscopy and cryo-electron tomography (Cryo-ET) with in vivo and in vitro systems, we report that non-uniform mechanical interactions with the microenvironment can lead to 10-fold diameter differences within an axon of the central nervous system (CNS). In the brains of adult Thy1-YFP transgenic mice, individual axons in the cortex displayed significantly higher diameter variation than those in the corpus callosum. When being cultured on lacey carbon film-coated electron microscopy (EM) grids, CNS axons formed varicosities exclusively in holes and without microtubule (MT) breakage, and they contained mitochondria, multivesicular bodies (MVBs), and/or vesicles, similar to the axonal varicosities induced by mild fluid puffing. Moreover, enlarged axon branch points often contain MT free ends leading to the minor branch. When the axons were fasciculated by mimicking in vivo axonal bundles, their varicosity levels reduced. Taken together, our results have revealed the extrinsic regulation of the three-dimensional ultrastructures of central axons by the mechanical microenvironment under physiological conditions.https://www.mdpi.com/2073-4409/11/16/2533axonal varicositycryo-electron tomography (Cryo-ET)primary neuron culturemicrotubule (MT)mitochondriamultivesicular body (MVB) |
| spellingShingle | Di Ma Binbin Deng Chao Sun David W. McComb Chen Gu The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron Tomography Cells axonal varicosity cryo-electron tomography (Cryo-ET) primary neuron culture microtubule (MT) mitochondria multivesicular body (MVB) |
| title | The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron Tomography |
| title_full | The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron Tomography |
| title_fullStr | The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron Tomography |
| title_full_unstemmed | The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron Tomography |
| title_short | The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron Tomography |
| title_sort | mechanical microenvironment regulates axon diameters visualized by cryo electron tomography |
| topic | axonal varicosity cryo-electron tomography (Cryo-ET) primary neuron culture microtubule (MT) mitochondria multivesicular body (MVB) |
| url | https://www.mdpi.com/2073-4409/11/16/2533 |
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