Characterization of early pathogenesis in the SOD1G93A mouse model of ALS: part II, results and discussion

Authors

  • Sharon Vinsant,

    1. Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina
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  • Carol Mansfield,

    1. Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina
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  • Ramon Jimenez-Moreno,

    1. Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina
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  • Victoria Del Gaizo Moore,

    1. Department of Chemistry, Elon University, Elon, North Carolina
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  • Masaaki Yoshikawa,

    1. Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina
    Current affiliation:
    1. Division of Anatomical Science, Department of Functional Morphology, Nihon University School of Medicine, Itabashi, Tokyo, Japan
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  • Thomas G. Hampton,

    1. Mouse Specifics, Boston, Massachusetts
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  • David Prevette,

    1. Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina
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  • James Caress,

    1. Department of Neurology and the ALS Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina
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  • Ronald W. Oppenheim,

    1. Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina
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  • Carol Milligan

    Corresponding author
    • Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina
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Correspondence

Carol Milligan, Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157. Tel: 336-716-0499; Fax: 336-716-4534; E-mail: milligan@wfubmc.edu

Abstract

Pathological events are well characterized in amyotrophic lateral sclerosis (ALS) mouse models, but review of the literature fails to identify a specific initiating event that precipitates disease pathology. There is now growing consensus in the field that axon and synapses are first cellular sites of degeneration, but controversy exists over whether axon and synapse loss is initiated autonomously at those sites or by pathology in the cell body, in nonneuronal cells or even in nonmotoneurons (MNs). Previous studies have identified pathological events in the mutant superoxide dismutase 1 (SOD1) models involving spinal cord, peripheral axons, neuromuscular junctions (NMJs), or muscle; however, few studies have systematically examined pathogenesis at multiple sites in the same study. We have performed ultrastructural examination of both central and peripheral components of the neuromuscular system in the SOD1G93A mouse model of ALS. Twenty percent of MNs undergo degeneration by P60, but NMJ innervation in fast fatigable muscles is reduced by 40% by P30. Gait alterations and muscle weakness were also found at P30. There was no change in axonal transport prior to initial NMJ denervation. Mitochondrial morphological changes are observed at P7 and become more prominent with disease progression. At P30 there was a significant decrease in excitatory axo-dendritic and axo-somatic synapses with an increase in C-type axo-somatic synapses. Our study examined early pathology in both peripheral and central neuromuscular system. The muscle denervation is associated with functional motor deficits and begins during the first postnatal month in SOD1G93A mice. Physiological dysfunction and pathology in the mitochondria of synapses and MN soma and dendrites occur, and disease onset in these animals begins more than 2 months earlier than originally thought. This information may be valuable for designing preclinical trials that are more likely to impact disease onset and progression.

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