Cargando…

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...

Descripción completa

Detalles Bibliográficos
Autores principales: Ma, Di, Deng, Binbin, Sun, Chao, McComb, David W., Gu, Chen
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
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
_version_ 1784774090886742016
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
work_keys_str_mv AT madi themechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography
AT dengbinbin themechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography
AT sunchao themechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography
AT mccombdavidw themechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography
AT guchen themechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography
AT madi mechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography
AT dengbinbin mechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography
AT sunchao mechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography
AT mccombdavidw mechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography
AT guchen mechanicalmicroenvironmentregulatesaxondiametersvisualizedbycryoelectrontomography