Abstract
Amyotrophic lateral sclerosis (ALS) is a lethal disease, characterized by progressive death of motor neurons with unknown etiology. Evidence from animal models indicates that neuronal dysfunction precedes the clinical phase of the disease. However, in parallel extensive nerve sprouting and synaptic remodeling as part of a compensatory reinnervation processes and possibly also of motor neurons pathology was demonstrated. Therefore, the weakness in muscle groups will not be clinically apparent until a large proportion of motor units are lost. This motor unit loss and associated muscle function which precedes the death of motor neurons may resemble the “die-back” phenomena. Studies indicated that in the early stages the nerve terminals and motor neuron junctions are partially degraded while the cell bodies in the spinal cord are mostly intact. Treatments to rescue motor neurons according to “dying-forward” model of motor neuron pathology in ALS have shown only limited success in SOD1G93A transgenic mice as well as in humans. If cell body degeneration is late compared with axonal degeneration, early intervention could potentially prevent loss of motor neurons. Therefore, it should be considered, according to the dying back hypothesis, to focus on motor neurons terminals in order to delay or prevent the progressive degradation.
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References
Acsadi G, Anguelov R, Yang H et al (2002) Increased survival and function of SOD1 mice after Glial cell- derived neurotrophic factor gene therapy. Hum Gene Ther 13:1047–1059
Aguilar GJ, Laguna AE, Fergani A et al (2007) Amyotrophic lateral sclerosis: all roads lead to Rome. J Neurochem 101:1153–60
Azzouz M, Ralph GS, Storkebaum E et al (2004) VEGF delivery with retrogradely transported lentivector prolongs survival in mouse ALS model. Nature 429:413–417
Bendotti C, Calvaresi N, Chiveri L et al (2001) Early vacuolization and mitochondrial damage in motor neurons of FALS mice are not associated with apoptosis or with changes in cytochrome oxidase histochemical reactivity. J Neurol Sci 191:25–33
Bruijn L, Miller TM, Cleveland DW (2004) Unraveling the mechanisms involved in motor neuron degeneration in ALS. Annu Rev Neurosci 27:723–749
Coleman MP, Perry VH (2002) Axon pathology in neurological disease: a neglected therapeutic target. Trends Neurosci 25:532–537
Crone SA, Lee KF (2002) The bound leading the bound: target derived receptors act as guidance cues. Neuron 36:333–335
De Winter F, Vo T, Stam FJ et al (2006) The expression of the chemorepellent Semaphorin 3A is selectively induced in terminal Schwann cells of a subset of neuromuscular synapses that display limited anatomical plasticity and enhanced vulnerability in motor neuron disease. Mol Cell Neurosci 32:102–117
Deshpande DM, Kim YS, Martinez T et al (2006) Recovery from paralysis in adult rats using embryonic stem cells. Ann Neurol 60:32–44
Dobrowolny G, Giacinti C, Pelosi L et al (2005) Muscle expression of a local Igf-1 isoform protects motor neurons in an ALS mouse model. J Cell Biol 168:193–199
Durand J, Amendola J, Bories C, Lamotte d’Incamps B (2006) Early abnormalities in transgenic mouse models of amyotrophic lateral sclerosis. J Physiol Paris 99:211–220
Feinberg DM, Preston DC, Shefner JM, Logigian EL (1999) Amplitude dependent slowing of conduction in amyotrophic lateral sclerosis and polyneuropathy. Muscle Nerve 22:1646–1651
Felice KJ (1997) A longitudinal study comparing thenar motor unit number estimates to other quantitative tests in patients with amyotrophic lateral sclerosis. Muscle Nerve 20(2):179–185
Fischer LR, Culver DG, Tennant P et al (2003) Amyotrophic lateral sclerosis is a distal axonopathy: evidence in mice and man. Exp Neurol 185:232–240
Fischer LR, Culver DG, Tennant P et al (2004) Amyotrophic lateral sclerosis is a distal axonopathy: evidance in mice and man. Exp Neurol 185(2):232–240
Frey D, Schneider C, Xu L, Borg J, Spooren W, Caroni P (2000) Early and selective loss of neuromuscular synapse subtypes with low sprouting competence in motoneuron diseases. J Neurosci 20:2534–2542
Fryer HJ, Wolf DH, Knox RJ et al (2000) Brain-derived neurotrophic factor induces excitotoxic sensitivity in cultured embryonic rat spinal motor neurons through activation of the phosphatidylinositol 3-kinase pathway. J Neurochem 74:582–595
Gordon T, Thomas CK, Munson JB, Stein RB (2004) The resilience of the size principle in the organization of motor unit properties in normal and reinnervated adult skeletal muscles. Can J Physiol Pharmacol 89:645–661
Gruzman A, Wood WL, Alpert E et al (2007) Common molecular signature in SOD-1 for both sporadic and familial amyotrophic lateral sclerosis. Proc Natl Acad Sci USA 104:12524–9
Hayworth CR, Gonzales-Lima F (2009) Pre-symptomatic detection of chronic motor deficits genotype prediction in congenic B6.SOD1G93A ALS mouse model. Neuroscience 164:975–85
Hegedus J, Putman CT, Gordon T (2007) Time course of preferential motor unit loss in the SOD1G93A mouse model of amyotrophic lateral sclerosis. Neurobiol Dis 28:154–164
Henneman E, Mendell LM (1981) Functional organization of the motor neuron pool and its inputs in the nervous system: motor control part 1, sect. 1. vol. 2, Brooks, VB (ed). American Physiology Society, Washington, DC. pp 345–442.
Hu P, Kalb RG (2003) BDNF heightens the sensitivity of motor neurons to excitotoxic insults through activation of TrkB. J Neurochem 84:1421–1430
Ilieva EV, Ayala V, Jové M et al (2007) Oxidative and endoplasmic reticulum stress interplay in sporadic amyotrophic lateral sclerosis. Brain 130:3111–23
Jokic N, Gonzales de Aguilar JL, Pardat PF et al (2005) Nogo expression in muscle correlates with amyotrophic lateral sclerosis severity. Ann Neurol 57:553–556
Kaspar BK, Llado J, Sherkat N, Rothstein JD, Gage FH (2003) Retrograde viral delivery of IGF-1 prolongs survival in a mouse ALS model. Science 301:839–842
Kong J, Xu Z (1998) Massive mitochondrial degeneration in motor neurons triggers the onset of amyotrophic lateral sclerosis in mice expressing a mutant SOD1. J Neuroscience 18:3241–3250
Lambrechts D, Carmeliet P (2006) VEGF in the neurovasculat interface: therapeutic implication for motor neuron disease. Biochim Biophys Acta 1762:1109–1121
LaMonte BH, Wallace KE, Holloway BA et al (2002) Disruption of dynein/dynactin inhibits axonal transport in motor neurons causing late-onset progressive degeneration. Neuron 34:715–727
Lev N, Ickowicz D, Barhum Y, Melamed E, Offen D (2009) DJ-1 changes in G93A-SOD1 transgenic mice: Implications for oxidative stress in ALS. J Mol Neurosci 38:94–102
Li W, Brakefield D, Pan Y, Hunter D, Myckatyn TM, Parsadanian A (2007) Muscle-derived but not centrally derived transgene GDNF is neuroprotective in G93A-SOD1 mouse model of ALS. Exp Neurol 203:457–471
Lu l, Zheng L, Viera L et al (2007) Mutant Cu/Zn- superoxide dismutase associated with amyotrophic lateral sclerosis destabilizes vascular endothelial growth factor mRNA and downregulates its expression. J Neurosci 27:7929–7938
Mohajeri H, Figlewicz D, Bohn M (1999) Intramuscular grafts of myoblasts genetically modified to secrete glial cell line-derived neurotrophic factor prevent motoneuron loss and disease progression in a mouse model of familial amyotrophic lateral sclerosis. Hum Gene Ther 10:1853–1866
Mousavi K, Parrav D, Lasmin B (2004) BDNF rescue myosin heavy chain IIB muscle fibers after neonatal nerve injury. Am J Physiol Cell Physiol 287:C22–9
Musarò A, McCullagh K, Paul A et al (2001) Igf-1 transgene expression sustains hypertrophy and regeneration in senescent skeletal muscle. Nat Genet 27:195–200
Offen D, Barhum Y, Melamed E, Embacher N, Schindler C, Ransmayr G (2009) Spinal cord mRNA profile in patients with ALS: comparison with transgenic mice expressing the human SOD-1 mutant. J Mol Neurosci 38:85–93
Oosthuyse B, Moons L, Storkebaum E et al (2001) Deletion of the hypoxia- response element in the vascular endothelial growth factor promoter causes motor neuron degeneration. Nat Genet 28:131–138
Ozdinler H, Macklis J (2006) IGF-I specifically enhances axon outgrowth of corticospinal motor neurons. Nat Neurosci 9:1371–1381
Park KHJ, Vincent I (2008) Presymptomatic biochemical changes in hind limb muscle of G93A human Cu/Zn superoxide dismutase 1 transgenic mouse model of amyotrophic lateral sclerosis. Biochim Biophys acta 1782:462–468
Parkhouse WS, Cunningham L, Mcfee I et al (2008) Neuromuscular dysfunction in the mutant superoxide dismutase mouse model of amyotrophic lateral sclerosis. Amyotroph Lateral Scler 9:24–34
Pasterkamp RJ, Giger RJ (2009) Semaphorin function in neural plasticity and disease. Curr Opin Neurobil 19:263–274
Pun S, Santos AF, Saxena S, Xu L, Caroni P (2006) Selective vulnerability and pruning of phasic motoneuron axons in motoneuron disease alleviated by CNTF. Nat Neurosci 9:408–419
Rabinovsky ED, Gelir E, Gelir S et al (2003) Targeted expression of IGF-1 transgene to skeletal muscle accelerates muscle and motor neuron regeneration. FASEB J 17:53–55
Rotestein JD, Jin L, Dykes-Hoberg M, Kunel RW (1993) Chronic inhibition of gloutamate uptake produces a model of slow neurotoxicity. Proc Natl Acad Sci USA 90:6591–6595
Sagot Y, Vejsada R, Kato A (1997) Clinical and molecular aspects of motoneuron diseases: animal models, neurotrophic factors and Bcl-2 oncoprotein. Trends Pharmacol Sci 18:330–337
Sakowski SA, Schuyler AD, Feldman EL (2009) Insulin-like growth factor-I for the treatment of amyotrophic lateral sclerosis. Amyotroph Lateral Scler 10:63–73
Schmidt ERE, Pasterkamp RJ, Van den Berg LH (2009) Axon guidance proteins: novel therapeutic targets for ALS? Prog Neurobiol 88:286–301
Séverine B, Velde CV, Cleveland DW (2006) ALS: a disease of motor neurons and their nonneuronal neighbors. Neuron 52:39–59
Shaw PJ (2005) Molecular and cellular pathways of neurodegeneration in motor neuron disease. J Neurol Neurosurgery Psychiatry 76:1046–1057
Siklos L, Engelhardt J, Harati Y, Smith RG, Joo F, Appel SH (1996) Ultrastructural evidence for altered calcium in motornerve terminals in amyotrophic lateral sclerosis. Ann Neurol 39:203–216
Storkebaum E, Lambrechts D, Dewerchin M et al (2005) Treatment of motoneuron degeneration by intracerbroventricular delivery of VEGF in a rat model of ALS. Nat Neurosci 8:85–92
Turner BJ, Talbot K (2008) Transgenics, toxicity and therapeutics in rodent models of mutant SOD-1-mediated familial ALS. Prog Neurobiol 85:94–134
Wang Y, Mao XO, Xie L et al (2007) Vascular endothelial growth factor overexpression delays neurodegeneraion and prolongs survival in amyotrophic lateral sclerosis mice. J Neurosci 27:304–307
Williamson TL, Cleveland DW (1999) Slowing of axonal transport is a very early event in the toxicity of ALS- linked SOD1 mutant to motor neurons. Nat Neurosci 2:50–56
Zhang B, Tu P, Abtahian F, Trojanowski JQ, Lee TM (1997) Neurofilaments and orthograde transport are reduced in ventral root axons of transgenic mice that express human SOD1 with a G93A mutation. J Cell Biol 139:1307–1315
Zheng C, Skold MK, Li J, Nennesmo I, Fadeel B, Henter JI (2007) VEGF reduces astryogliosis and preserves neuromuscular junctions in ALS transgenic mice. Biochem Biophys Res Commun 363:989–993
Acknowledgments
This work was performed by Michal Dadon in partial fulfillment of the requirements for a Ph.D. degree. This work was supported, in part, by The Devora Eleonora Kirshman Fund for Research of Parkinson’s Disease, Tel Aviv University and by the Norma and Alan Aufzein Chair of Research of Parkinson’s Disease.
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Dadon-Nachum, M., Melamed, E. & Offen, D. The “Dying-Back” Phenomenon of Motor Neurons in ALS. J Mol Neurosci 43, 470–477 (2011). https://doi.org/10.1007/s12031-010-9467-1
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DOI: https://doi.org/10.1007/s12031-010-9467-1
Keywords
- Amyotrophic lateral sclerosis
- Motor neuron
- Dying back