Ultrastructural study mitochondria in the spinal cord of transgenic mice with a G93A mutant SOD1 gene

Shoichi Sasaki, Hitoshi Warita, Tetsuro Murakami, Koji Abe, Makoto Iwata

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

The purpose of this study was to examine mitochondrial changes in the spinal cord of transgenic mice of a relatively low transgenic copy number (gene copy 10) expressing a G93A mutant human Cu/Zn superoxide dismutase (SOD1) that were generated in our own laboratories by electron and immunoelectron microscopy from presymptomatic to symptomatic stages. Age-matched nontransgenic mice served as controls at each stage. Ultrastructurally, at the early presymptomatic stage, many mitochondria in large myelinated axons exhibited swelling with an increased number of cristae, and bore small vacuoles in the matrix, cristae or both, in the anterior root exit zone, anterior root, and in the neuropils of the ventral portion of the anterior horn. At the late presymptomatic stage, vacuoles of various sizes (including large ones) were observed in the same regions as in the previous stage. The intermembrane space of mitochondria was also vacuolated. In mitochondria with advanced vacuolation, the vacuolar space was filled with a granular or amorphous substance. At the symptomatic stage, mitochondrial vacuolation seen in the late presymptomatic stage persisted, although to a lesser extent. These vacuolated mitochondria were predominantly seen in the axons, but not in the somata of normal-looking neurons or dendrites at any stage, which differs from that described in other reports. Nontransgenic littermates occasionally exhibited vacuolar changes in the axons of anterior horns. However, they were smaller both in size and number than those in transgenic mice. By immunoelectron microscopy using an immunogold labeling method, at the presymptomatic and symptomatic stages both SOD1 and ubiquitin determinants were localized in vacuolated mitochondria, particularly in the granular or amorphous substance of large vacuoles, but were not detected in most normal-appearing mitochondria. The SOD1-immunoreactive mitochondria were exclusively observed in the axons, and not in proximal dendrites or somata. These findings suggest that the toxicity of mutant SOD1 directly affects mitochondria in the axons and increases with the disease progression. Thus, the mutant SOD1 toxicity might disrupt axonal transport of substrates needed for neuronal viability, leading to motor neuron degeneration. The localization of both ubiquitin and SOD1 in vacuolated mitochondria indicates that protein degradation by ubiquitin-proteasomal system may be also disrupted by several pathomechanisms, such as decreased processing of ubiquitinated proteins due to impairment of mitochondrial function or of proteasomal function, both of which are caused by mutant SOD1. Moreover, giant mitochondrial vacuoles occupying almost the entire axonal caliber could be another contributing factor in motor neuron degeneration, in that they could physically block axonal transport.

Original languageEnglish
Pages (from-to)461-474
Number of pages14
JournalActa Neuropathologica
Volume107
Issue number5
DOIs
Publication statusPublished - May 2004

Fingerprint

Transgenic Mice
Spinal Cord
Mitochondria
Axons
Genes
Vacuoles
Ubiquitin
Nerve Degeneration
Axonal Transport
Gene Dosage
Immunoelectron Microscopy
Carisoprodol
Motor Neurons
Horns
Dendrites
Ubiquitinated Proteins
Neuropil
Proteolysis
Disease Progression
Electron Microscopy

Keywords

  • Amyotrophic lateral sclerosis
  • G93A transgenic mice
  • Mitochondria
  • SOD1 mutation
  • Vacuolation

ASJC Scopus subject areas

  • Clinical Neurology
  • Pathology and Forensic Medicine
  • Neuroscience(all)

Cite this

Ultrastructural study mitochondria in the spinal cord of transgenic mice with a G93A mutant SOD1 gene. / Sasaki, Shoichi; Warita, Hitoshi; Murakami, Tetsuro; Abe, Koji; Iwata, Makoto.

In: Acta Neuropathologica, Vol. 107, No. 5, 05.2004, p. 461-474.

Research output: Contribution to journalArticle

Sasaki, Shoichi ; Warita, Hitoshi ; Murakami, Tetsuro ; Abe, Koji ; Iwata, Makoto. / Ultrastructural study mitochondria in the spinal cord of transgenic mice with a G93A mutant SOD1 gene. In: Acta Neuropathologica. 2004 ; Vol. 107, No. 5. pp. 461-474.
@article{099d45830e2d4ec5bf2c8f251eb89581,
title = "Ultrastructural study mitochondria in the spinal cord of transgenic mice with a G93A mutant SOD1 gene",
abstract = "The purpose of this study was to examine mitochondrial changes in the spinal cord of transgenic mice of a relatively low transgenic copy number (gene copy 10) expressing a G93A mutant human Cu/Zn superoxide dismutase (SOD1) that were generated in our own laboratories by electron and immunoelectron microscopy from presymptomatic to symptomatic stages. Age-matched nontransgenic mice served as controls at each stage. Ultrastructurally, at the early presymptomatic stage, many mitochondria in large myelinated axons exhibited swelling with an increased number of cristae, and bore small vacuoles in the matrix, cristae or both, in the anterior root exit zone, anterior root, and in the neuropils of the ventral portion of the anterior horn. At the late presymptomatic stage, vacuoles of various sizes (including large ones) were observed in the same regions as in the previous stage. The intermembrane space of mitochondria was also vacuolated. In mitochondria with advanced vacuolation, the vacuolar space was filled with a granular or amorphous substance. At the symptomatic stage, mitochondrial vacuolation seen in the late presymptomatic stage persisted, although to a lesser extent. These vacuolated mitochondria were predominantly seen in the axons, but not in the somata of normal-looking neurons or dendrites at any stage, which differs from that described in other reports. Nontransgenic littermates occasionally exhibited vacuolar changes in the axons of anterior horns. However, they were smaller both in size and number than those in transgenic mice. By immunoelectron microscopy using an immunogold labeling method, at the presymptomatic and symptomatic stages both SOD1 and ubiquitin determinants were localized in vacuolated mitochondria, particularly in the granular or amorphous substance of large vacuoles, but were not detected in most normal-appearing mitochondria. The SOD1-immunoreactive mitochondria were exclusively observed in the axons, and not in proximal dendrites or somata. These findings suggest that the toxicity of mutant SOD1 directly affects mitochondria in the axons and increases with the disease progression. Thus, the mutant SOD1 toxicity might disrupt axonal transport of substrates needed for neuronal viability, leading to motor neuron degeneration. The localization of both ubiquitin and SOD1 in vacuolated mitochondria indicates that protein degradation by ubiquitin-proteasomal system may be also disrupted by several pathomechanisms, such as decreased processing of ubiquitinated proteins due to impairment of mitochondrial function or of proteasomal function, both of which are caused by mutant SOD1. Moreover, giant mitochondrial vacuoles occupying almost the entire axonal caliber could be another contributing factor in motor neuron degeneration, in that they could physically block axonal transport.",
keywords = "Amyotrophic lateral sclerosis, G93A transgenic mice, Mitochondria, SOD1 mutation, Vacuolation",
author = "Shoichi Sasaki and Hitoshi Warita and Tetsuro Murakami and Koji Abe and Makoto Iwata",
year = "2004",
month = "5",
doi = "10.1007/s00401-004-0837-z",
language = "English",
volume = "107",
pages = "461--474",
journal = "Acta Neuropathologica",
issn = "0001-6322",
publisher = "Springer Verlag",
number = "5",

}

TY - JOUR

T1 - Ultrastructural study mitochondria in the spinal cord of transgenic mice with a G93A mutant SOD1 gene

AU - Sasaki, Shoichi

AU - Warita, Hitoshi

AU - Murakami, Tetsuro

AU - Abe, Koji

AU - Iwata, Makoto

PY - 2004/5

Y1 - 2004/5

N2 - The purpose of this study was to examine mitochondrial changes in the spinal cord of transgenic mice of a relatively low transgenic copy number (gene copy 10) expressing a G93A mutant human Cu/Zn superoxide dismutase (SOD1) that were generated in our own laboratories by electron and immunoelectron microscopy from presymptomatic to symptomatic stages. Age-matched nontransgenic mice served as controls at each stage. Ultrastructurally, at the early presymptomatic stage, many mitochondria in large myelinated axons exhibited swelling with an increased number of cristae, and bore small vacuoles in the matrix, cristae or both, in the anterior root exit zone, anterior root, and in the neuropils of the ventral portion of the anterior horn. At the late presymptomatic stage, vacuoles of various sizes (including large ones) were observed in the same regions as in the previous stage. The intermembrane space of mitochondria was also vacuolated. In mitochondria with advanced vacuolation, the vacuolar space was filled with a granular or amorphous substance. At the symptomatic stage, mitochondrial vacuolation seen in the late presymptomatic stage persisted, although to a lesser extent. These vacuolated mitochondria were predominantly seen in the axons, but not in the somata of normal-looking neurons or dendrites at any stage, which differs from that described in other reports. Nontransgenic littermates occasionally exhibited vacuolar changes in the axons of anterior horns. However, they were smaller both in size and number than those in transgenic mice. By immunoelectron microscopy using an immunogold labeling method, at the presymptomatic and symptomatic stages both SOD1 and ubiquitin determinants were localized in vacuolated mitochondria, particularly in the granular or amorphous substance of large vacuoles, but were not detected in most normal-appearing mitochondria. The SOD1-immunoreactive mitochondria were exclusively observed in the axons, and not in proximal dendrites or somata. These findings suggest that the toxicity of mutant SOD1 directly affects mitochondria in the axons and increases with the disease progression. Thus, the mutant SOD1 toxicity might disrupt axonal transport of substrates needed for neuronal viability, leading to motor neuron degeneration. The localization of both ubiquitin and SOD1 in vacuolated mitochondria indicates that protein degradation by ubiquitin-proteasomal system may be also disrupted by several pathomechanisms, such as decreased processing of ubiquitinated proteins due to impairment of mitochondrial function or of proteasomal function, both of which are caused by mutant SOD1. Moreover, giant mitochondrial vacuoles occupying almost the entire axonal caliber could be another contributing factor in motor neuron degeneration, in that they could physically block axonal transport.

AB - The purpose of this study was to examine mitochondrial changes in the spinal cord of transgenic mice of a relatively low transgenic copy number (gene copy 10) expressing a G93A mutant human Cu/Zn superoxide dismutase (SOD1) that were generated in our own laboratories by electron and immunoelectron microscopy from presymptomatic to symptomatic stages. Age-matched nontransgenic mice served as controls at each stage. Ultrastructurally, at the early presymptomatic stage, many mitochondria in large myelinated axons exhibited swelling with an increased number of cristae, and bore small vacuoles in the matrix, cristae or both, in the anterior root exit zone, anterior root, and in the neuropils of the ventral portion of the anterior horn. At the late presymptomatic stage, vacuoles of various sizes (including large ones) were observed in the same regions as in the previous stage. The intermembrane space of mitochondria was also vacuolated. In mitochondria with advanced vacuolation, the vacuolar space was filled with a granular or amorphous substance. At the symptomatic stage, mitochondrial vacuolation seen in the late presymptomatic stage persisted, although to a lesser extent. These vacuolated mitochondria were predominantly seen in the axons, but not in the somata of normal-looking neurons or dendrites at any stage, which differs from that described in other reports. Nontransgenic littermates occasionally exhibited vacuolar changes in the axons of anterior horns. However, they were smaller both in size and number than those in transgenic mice. By immunoelectron microscopy using an immunogold labeling method, at the presymptomatic and symptomatic stages both SOD1 and ubiquitin determinants were localized in vacuolated mitochondria, particularly in the granular or amorphous substance of large vacuoles, but were not detected in most normal-appearing mitochondria. The SOD1-immunoreactive mitochondria were exclusively observed in the axons, and not in proximal dendrites or somata. These findings suggest that the toxicity of mutant SOD1 directly affects mitochondria in the axons and increases with the disease progression. Thus, the mutant SOD1 toxicity might disrupt axonal transport of substrates needed for neuronal viability, leading to motor neuron degeneration. The localization of both ubiquitin and SOD1 in vacuolated mitochondria indicates that protein degradation by ubiquitin-proteasomal system may be also disrupted by several pathomechanisms, such as decreased processing of ubiquitinated proteins due to impairment of mitochondrial function or of proteasomal function, both of which are caused by mutant SOD1. Moreover, giant mitochondrial vacuoles occupying almost the entire axonal caliber could be another contributing factor in motor neuron degeneration, in that they could physically block axonal transport.

KW - Amyotrophic lateral sclerosis

KW - G93A transgenic mice

KW - Mitochondria

KW - SOD1 mutation

KW - Vacuolation

UR - http://www.scopus.com/inward/record.url?scp=2342442179&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=2342442179&partnerID=8YFLogxK

U2 - 10.1007/s00401-004-0837-z

DO - 10.1007/s00401-004-0837-z

M3 - Article

VL - 107

SP - 461

EP - 474

JO - Acta Neuropathologica

JF - Acta Neuropathologica

SN - 0001-6322

IS - 5

ER -