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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...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2022
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9406316/ https://www.ncbi.nlm.nih.gov/pubmed/36010609 http://dx.doi.org/10.3390/cells11162533 |
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author | Ma, Di Deng, Binbin Sun, Chao McComb, David W. Gu, Chen |
author_facet | Ma, Di Deng, Binbin Sun, Chao McComb, David W. Gu, Chen |
author_sort | Ma, Di |
collection | PubMed |
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. |
format | Online Article Text |
id | pubmed-9406316 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2022 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-94063162022-08-26 The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron Tomography Ma, Di Deng, Binbin Sun, Chao McComb, David W. Gu, Chen Cells Article 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. MDPI 2022-08-15 /pmc/articles/PMC9406316/ /pubmed/36010609 http://dx.doi.org/10.3390/cells11162533 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Ma, Di Deng, Binbin Sun, Chao McComb, David W. Gu, Chen The Mechanical Microenvironment Regulates Axon Diameters Visualized by Cryo-Electron Tomography |
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 | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9406316/ https://www.ncbi.nlm.nih.gov/pubmed/36010609 http://dx.doi.org/10.3390/cells11162533 |
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