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Krause Neto W, Silva W, Oliveira T, Vilas Boas A, Ciena A, Caperuto ÉC, Gama EF. Ladder-based resistance training with the progression of training load altered the tibial nerve ultrastructure and muscle fiber area without altering the morphology of the postsynaptic compartment. Front Physiol 2024; 15:1371839. [PMID: 38694209 PMCID: PMC11061484 DOI: 10.3389/fphys.2024.1371839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 04/02/2024] [Indexed: 05/04/2024] Open
Abstract
Scientific evidence regarding the effect of different ladder-based resistance training (LRT) protocols on the morphology of the neuromuscular system is scarce. Therefore, the present study aimed to compare the morphological response induced by different LRT protocols in the ultrastructure of the tibial nerve and morphology of the motor endplate and muscle fibers of the soleus and plantaris muscles of young adult Wistar rats. Rats were divided into groups: sedentary control (control, n = 9), a predetermined number of climbs and progressive submaximal intensity (fixed, n = 9), high-intensity and high-volume pyramidal system with a predetermined number of climbs (Pyramid, n = 9) and lrt with a high-intensity pyramidal system to exhaustion (failure, n = 9). myelinated fibers and myelin sheath thickness were statistically larger in pyramid, fixed, and failure. myelinated axons were statistically larger in pyramid than in control. schwann cell nuclei were statistically larger in pyramid, fixed, and failure. microtubules and neurofilaments were greater in pyramid than in control. morphological analysis of the postsynaptic component of the plantar and soleus muscles did not indicate any significant difference. for plantaris, the type i myofibers were statistically larger in the pyramid and fixed compared to control. the pyramid, fixed, and failure groups for type ii myofibers had larger csa than control. for soleus, the type i myofibers were statistically larger in the pyramid than in control. pyramid and fixed had larger csa for type ii myofibers than control and failure. the pyramid and fixed groups showed greater mass progression delta than the failure. We concluded that the LRT protocols with greater volume and progression of accumulated mass elicit more significant changes in the ultrastructure of the tibial nerve and muscle hypertrophy without endplate changes.
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Affiliation(s)
- Walter Krause Neto
- Department of Morphology and Genetics, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Wellington Silva
- Depatment of Physical Education, Laboratory of Human Movement, Universidade São Judas Tadeu, São Paulo, Brazil
| | - Tony Oliveira
- Depatment of Physical Education, Laboratory of Human Movement, Universidade São Judas Tadeu, São Paulo, Brazil
| | - Alan Vilas Boas
- Depatment of Physical Education, Laboratory of Human Movement, Universidade São Judas Tadeu, São Paulo, Brazil
| | - Adriano Ciena
- Department of Physical Education, Laboratory of Morphology and Physical Activity, Universidade Estadual Paulista Júlio de Mesquita Filho, São Paulo, Brazil
| | - Érico Chagas Caperuto
- Depatment of Physical Education, Laboratory of Human Movement, Universidade São Judas Tadeu, São Paulo, Brazil
| | - Eliane Florencio Gama
- Department of Morphology and Genetics, Universidade Federal de São Paulo, São Paulo, Brazil
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Fenn JD, Li Y, Julien JP, Jung P, Brown A. The Mobility of Neurofilaments in Mature Myelinated Axons of Adult Mice. eNeuro 2023; 10:ENEURO.0029-23.2023. [PMID: 36882311 PMCID: PMC10035772 DOI: 10.1523/eneuro.0029-23.2023] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 02/20/2023] [Accepted: 02/26/2023] [Indexed: 03/09/2023] Open
Abstract
Studies in cultured neurons have shown that neurofilaments are cargoes of axonal transport that move rapidly but intermittently along microtubule tracks. However, the extent to which axonal neurofilaments move in vivo has been controversial. Some researchers have proposed that most axonally transported neurofilaments are deposited into a persistently stationary network and that only a small proportion of axonal neurofilaments are transported in mature axons. Here we use the fluorescence photoactivation pulse-escape technique to test this hypothesis in intact peripheral nerves of adult male hThy1-paGFP-NFM mice, which express low levels of mouse neurofilament protein M tagged with photoactivatable GFP. Neurofilaments were photoactivated in short segments of large, myelinated axons, and the mobility of these fluorescently tagged polymers was determined by analyzing the kinetics of their departure. Our results show that >80% of the fluorescence departed the window within 3 h after activation, indicating a highly mobile neurofilament population. The movement was blocked by glycolytic inhibitors, confirming that it was an active transport process. Thus, we find no evidence for a substantial stationary neurofilament population. By extrapolation of the decay kinetics, we predict that 99% of the neurofilaments would have exited the activation window after 10 h. These data support a dynamic view of the neuronal cytoskeleton in which neurofilaments cycle repeatedly between moving and pausing states throughout their journey along the axon, even in mature myelinated axons. The filaments spend a large proportion of their time pausing, but on a timescale of hours, most of them move.
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Affiliation(s)
- J Daniel Fenn
- Department of Neuroscience, The Ohio State University, Columbus, Ohio 43210
- Medical Scientist Training Program, The Ohio State University, Columbus, Ohio 43210
| | - Yinyun Li
- Quantitative Biology Institute and Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701
| | - Jean-Pierre Julien
- CERVO Brain Research Centre, Department of Psychiatry and Neuroscience, Laval University, Quebec, Quebec G1J 2G3, Canada
| | - Peter Jung
- Quantitative Biology Institute and Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701
| | - Anthony Brown
- Department of Neuroscience, The Ohio State University, Columbus, Ohio 43210
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Krause Neto W, Gama EF, Silva WDA, de Oliveira TVA, Vilas Boas AEDS, Ciena AP, Anaruma CA, Caperuto ÉC. The sciatic and radial nerves seem to adapt similarly to different ladder-based resistance training protocols. Exp Brain Res 2022; 240:887-896. [DOI: 10.1007/s00221-021-06295-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 12/16/2021] [Indexed: 11/25/2022]
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Neto WK, Gama EF, de Assis Silva W, de Oliveira TVA, Dos Santos Vilas Boas AE, Ciena AP, Anaruma CA, Caperuto ÉC. Ladder-based resistance training elicited similar ultrastructural adjustments in forelimb and hindlimb peripheral nerves of young adult Wistar rats. Exp Brain Res 2021; 239:2583-2592. [PMID: 34191117 DOI: 10.1007/s00221-021-06156-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 06/19/2021] [Indexed: 12/22/2022]
Abstract
To analyze the morphological response induced by high-volume, high-intensity ladder-based resistance training (LRT) on the ultrastructure of the radial (forelimb) and sciatic (hindlimb) nerves of adults Wistar rats. Twenty rats were equally distributed into groups: sedentary (SED) and LRT. After the rodents were subjected to the maximum load (ML) carrying test, the LRT group performed 6-8 progressive climbs (2 × 50% ML, 2 × 75% ML, 2 × 100% ML, and 2 × 100% ML + 30 g) three times per week. After 8 weeks, the radial and sciatic nerves were removed and prepared for transmission electron microscopy. In the radial nerve, myelinated axons cross-sectional area (CSA), unmyelinated axons CSA, myelin sheath thickness, and Schwann cells nuclei area were statistically larger in the LRT group than SED (p < 0.05). Also, the number of microtubules and neurofilaments per field were statistically higher in the LRT group than in SED (p < 0.01). For sciatic nerve, myelinated fibers CSA, unmyelinated axons CSA, myelin sheath thickness, Schwann cells nuclei area, and the number of neurofilaments per field were statistically larger in the LRT group compared to the SED group (p < 0.05). LRT with high-volume and high-intensity effectively induce similar changes in adult Wistar rats' radial and sciatic nerves' ultrastructure.
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Affiliation(s)
- Walter Krause Neto
- Department of Physical Education, Laboratory of Morphoquantitative Studies and Immunohistochemistry, São Judas Tadeu University, Rua Taquari, 546-Mooca Unit, P. O. Box 03166-000, São Paulo, SP, Brazil.
| | - Eliane Florencio Gama
- Department of Morphology, Faculty of Medical Sciences, Santa Casa de São Paulo, São Paulo, SP, Brazil
| | - Wellington de Assis Silva
- Department of Physical Education, Laboratory of Morphoquantitative Studies and Immunohistochemistry, São Judas Tadeu University, Rua Taquari, 546-Mooca Unit, P. O. Box 03166-000, São Paulo, SP, Brazil
| | - Tony Vinicius Apolinário de Oliveira
- Department of Physical Education, Laboratory of Morphoquantitative Studies and Immunohistochemistry, São Judas Tadeu University, Rua Taquari, 546-Mooca Unit, P. O. Box 03166-000, São Paulo, SP, Brazil
| | - Alan Esaú Dos Santos Vilas Boas
- Department of Physical Education, Laboratory of Morphoquantitative Studies and Immunohistochemistry, São Judas Tadeu University, Rua Taquari, 546-Mooca Unit, P. O. Box 03166-000, São Paulo, SP, Brazil
| | - Adriano Polican Ciena
- Department of Physical Education, Laboratory of Morphology and Physical Activity, São Paulo State University "Júlio de Mesquita Filho", Rio Claro, SP, Brazil
| | - Carlos Alberto Anaruma
- Department of Physical Education, Laboratory of Morphology and Physical Activity, São Paulo State University "Júlio de Mesquita Filho", Rio Claro, SP, Brazil
| | - Érico Chagas Caperuto
- Depatment of Physical Education, Laboratory of Human Movement, São Judas Tadeu University, São Paulo, SP, Brazil
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Kounakis K, Tavernarakis N. The Cytoskeleton as a Modulator of Aging and Neurodegeneration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1178:227-245. [PMID: 31493230 DOI: 10.1007/978-3-030-25650-0_12] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The cytoskeleton consists of filamentous protein polymers that form organized structures, contributing to a multitude of cell life aspects. It includes three types of polymers: the actin microfilaments, the microtubules and the intermediate filaments. Decades of research have implicated the cytoskeleton in processes that regulate cellular and organismal aging, as well as neurodegeneration associated with injury or neurodegenerative disease, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, Amyotrophic Lateral Sclerosis, or Charcot Marie Tooth disease. Here, we provide a brief overview of cytoskeletal structure and function, and discuss experimental evidence linking cytoskeletal function and dynamics with aging and neurodegeneration.
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Affiliation(s)
- Konstantinos Kounakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.,Department of Basic Sciences, Medical School, University of Crete, Heraklion, Greece
| | - Nektarios Tavernarakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece. .,Department of Basic Sciences, Medical School, University of Crete, Heraklion, Greece.
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Increase of neurofilament-H protein in sensory neurons in antiretroviral neuropathy: Evidence for a neuroprotective response mediated by the RNA-binding protein HuD. Pharmacol Res 2016; 111:23-33. [PMID: 27238228 DOI: 10.1016/j.phrs.2016.05.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 05/06/2016] [Accepted: 05/25/2016] [Indexed: 01/31/2023]
Abstract
Nucleoside reverse transcriptase inhibitors (NRTIs) are key components of HIV/AIDS treatment to reduce viral load. However, antiretroviral toxic neuropathy has become a common peripheral neuropathy among HIV/AIDS patients leading to discontinuation of antiretroviral therapy, for which the underlying pathogenesis is uncertain. This study examines the role of neurofilament (NF) proteins in the spinal dorsal horn, DRG and sciatic nerve after NRTI neurotoxicity in mice treated with zalcitabine (2',3'-dideoxycitidine; ddC). ddC administration up-regulated NF-M and pNF-H proteins with no effect on NF-L. The increase of pNF-H levels was counteracted by the silencing of HuD, an RNA binding protein involved in neuronal development and differentiation. Sciatic nerve sections of ddC exposed mice showed an increased axonal caliber, concomitantly to a pNF-H up-regulation. Both events were prevented by HuD silencing. pNF-H and HuD colocalize in DRG and spinal dorsal horn axons. However, the capability of HuD to bind NF mRNA was not demonstrated, indicating the presence of an indirect mechanism of control of NF expression by HuD. RNA immunoprecipitation experiments showed the capability of HuD to bind the BDNF mRNA and the administration of an anti-BDNF antibody prevented pNF-H increase. These data indicate the presence of a HuD - BDNF - NF-H pathway activated as a regenerative response to the axonal damage induced by ddC treatment to counteract the antiretroviral neurotoxicity. Since analgesics clinically used to treat neuropathic pain are ineffective on antiretroviral neuropathy, a neuroregenerative strategy might represent a new therapeutic opportunity to counteract neurotoxicity and avoid discontinuation or abandon of NRTI therapy.
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Gordon T. Nerve Regeneration: Understanding Biology and Its Influence on Return of Function After Nerve Transfers. Hand Clin 2016; 32:103-17. [PMID: 27094884 DOI: 10.1016/j.hcl.2015.12.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Poor functional outcomes are frequent after peripheral nerve injuries despite the regenerative support of Schwann cells. Motoneurons and, to a lesser extent, sensory neurons survive the injuries but outgrowth of axons across the injury site is slow. The neuronal regenerative capacity and the support of regenerating axons by the chronically denervated Schwann cells progressively declines with time and distance of the injury from the denervated targets. Strategies, including brief low-frequency electrical stimulation that accelerates target reinnervation and functional recovery, and the insertion of cross-bridges between a donor nerve and a recipient denervated nerve stump, are effective in promoting functional outcomes after complete and incomplete injuries.
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Affiliation(s)
- Tessa Gordon
- Division of Plastic Reconstructive Surgery, Department of Surgery, 06.9706 Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay Street, Toronto, Ontario M5G 0A4, Canada.
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Pesaresi M, Soon-Shiong R, French L, Kaplan DR, Miller FD, Paus T. Axon diameter and axonal transport: In vivo and in vitro effects of androgens. Neuroimage 2015; 115:191-201. [PMID: 25956809 DOI: 10.1016/j.neuroimage.2015.04.048] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 04/23/2015] [Accepted: 04/24/2015] [Indexed: 01/05/2023] Open
Abstract
Testosterone is a sex hormone involved in brain maturation via multiple molecular mechanisms. Previous human studies described age-related changes in the overall volume and structural properties of white matter during male puberty. Based on this work, we have proposed that testosterone may induce a radial growth of the axon and, possibly, modulate axonal transport. In order to determine whether this is the case we have used two different experimental approaches. With electron microscopy, we have evaluated sex differences in the structural properties of axons in the corpus callosum (splenium) of young rats, and tested consequences of castration carried out after weaning. Then we examined in vitro the effect of the non-aromatizable androgen Mibolerone on the structure and bidirectional transport of wheat-germ agglutinin vesicles in the axons of cultured sympathetic neurons. With electron microscopy, we found robust sex differences in axonal diameter (males>females) and g ratio (males>females). Removal of endogenous testosterone by castration was associated with lower axon diameter and lower g ratio in castrated (vs. intact) males. In vitro, Mibolerone influenced the axonal transport in a time- and dose-dependent manner, and increased the axon caliber as compared with vehicle-treated neurons. These findings are consistent with the role of testosterone in shaping the axon by regulating its radial growth, as predicted by the initial human studies.
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Affiliation(s)
- M Pesaresi
- Rotman Research Institute, University of Toronto, 3560 Bathurst Street, Toronto, Ontario M6A 2E1, Canada
| | - R Soon-Shiong
- Rotman Research Institute, University of Toronto, 3560 Bathurst Street, Toronto, Ontario M6A 2E1, Canada
| | - L French
- Rotman Research Institute, University of Toronto, 3560 Bathurst Street, Toronto, Ontario M6A 2E1, Canada
| | - D R Kaplan
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - F D Miller
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - T Paus
- Rotman Research Institute, University of Toronto, 3560 Bathurst Street, Toronto, Ontario M6A 2E1, Canada.
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Abstract
Axons in the vertebrate nervous system only expand beyond ∼ 1 μm in diameter if they become myelinated. This expansion is due in large part to the accumulation of space-filling cytoskeletal polymers called neurofilaments, which are cargoes of axonal transport. One possible mechanism for this accumulation is a decrease in the rate of neurofilament transport. To test this hypothesis, we used a fluorescence photoactivation pulse-escape technique to compare the kinetics of neurofilament transport in contiguous myelinated and unmyelinated segments of axons in long-term myelinating cocultures established from the dorsal root ganglia of embryonic rats. The myelinated segments contained more neurofilaments and had a larger cross-sectional area than the contiguous unmyelinated segments, and this correlated with a local slowing of neurofilament transport. By computational modeling of the pulse-escape kinetics, we found that this slowing of neurofilament transport could be explained by an increase in the proportion of the time that the neurofilaments spent pausing and that this increase in pausing was sufficient to explain the observed neurofilament accumulation. Thus we propose that myelinating cells can regulate the neurofilament content and morphology of axons locally by modulating the kinetics of neurofilament transport.
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Abstract
The pseudounipolar sensory neurons of the dorsal root ganglia (DRG) give rise to peripheral branches that convert thermal, mechanical, and chemical stimuli into electrical signals that are transmitted via central branches to the spinal cord. These neurons express unique combinations of tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) Na(+) channels that contribute to the resting membrane potential, action potential threshold, and regulate neuronal firing frequency. The small-diameter neurons (<25 μm) isolated from the DRG represent the cell bodies of C-fiber nociceptors that express both TTX-S and TTX-R Na(+) currents. The large-diameter neurons (>35 μm) are typically low-threshold A-fibers that predominately express TTX-S Na(+) currents. Peripheral nerve damage, inflammation, and metabolic diseases alter the expression and function of these Na(+) channels leading to increases in neuronal excitability and pain. The Na(+) channels expressed in these neurons are the target of intracellular signaling cascades that regulate the trafficking, cell surface expression, and gating properties of these channels. Post-translational regulation of Na(+) channels by protein kinases (PKA, PKC, MAPK) alter the expression and function of the channels. Injury-induced changes in these signaling pathways have been linked to sensory neuron hyperexcitability and pain. This review examines the signaling pathways and regulatory mechanisms that modulate the voltage-gated Na(+) channels of sensory neurons.
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Affiliation(s)
- Mohamed Chahine
- Centre de recherche, Institut en santé mentale de Québec, Local F-6539, 2601, chemin de la Canardière, QC City, QC, Canada, G1J 2G3,
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Cai J, Zhang YP, Shields LBE, Zhang ZZ, Liu N, Xu XM, Feng SQ, Shields CB. Correlation between electrophysiological properties, morphological maturation, and olig gene changes during postnatal motor tract development. Dev Neurobiol 2013; 73:713-22. [PMID: 23696057 DOI: 10.1002/dneu.22094] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 05/13/2013] [Accepted: 05/14/2013] [Indexed: 11/05/2022]
Abstract
This study investigated electrophysiological and histological changes as well as alterations of myelin relevant proteins of descending motor tracts in rat pups. Motor-evoked potentials (MEPs) represent descending conducting responses following stimulation of the motor cortex to responses being elicited from the lower extremities. MEP responses were recorded biweekly from postnatal (PN) week 1 to week 9 (adult). MEP latencies in PN week 1 rats averaged 23.7 ms and became shorter during early maturation, stabilizing at 6.6 ms at PN week 4. During maturation, the conduction velocity (CV) increased from 2.8 ± 0.2 at PN week 1 to 35.2 ± 3.1 mm/ms at PN week 8. Histology of the spinal cord and sciatic nerves revealed progressive axonal myelination. Expression of the oligodendrocyte precursor markers PDGFRα and NG2 were downregulated in spinal cords, and myelin-relevant proteins such as GalC, CNP, and MBP increased during maturation. Oligodendrocyte-lineage markers Olig2 and MOG, expressed in myelinated oligodendrocytes, peaked at PN week 3 and were downregulated thereafter. A similar expression pattern was observed in neurofilament M/H subunits that were extensively phosphorylated in adult spinal cords but not in neonatal spinal cords, suggesting an increase in axon diameter and myelin formation. Ultrastructural morphology in the ventrolateral funiculus (VLF) showed axon myelination of the VLF axons (99.3%) at PN week 2, while 44.6% were sheathed at PN week 1. Increased axon diameter and myelin thickness in the VLF and sciatic nerves were highly correlated to the CV (rs > 0.95). This suggests that MEPs could be a predicator of morphological maturity of myelinated axons in descending motor tracts.
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Affiliation(s)
- Jun Cai
- Departments of Pediatrics and Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA
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Wakeling EN, Joussemet B, Costiou P, Fanuel D, Moullier P, Barkats M, Fyfe JC. Failure of lower motor neuron radial outgrowth precedes retrograde degeneration in a feline model of spinal muscular atrophy. J Comp Neurol 2012; 520:1737-50. [PMID: 22120001 DOI: 10.1002/cne.23010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Feline spinal muscular atrophy (SMA) is a fully penetrant, autosomal recessive lower motor neuron disease in domestic cats that clinically resembles human SMA Type III. A whole genome linkage scan identified a ∼140-kb deletion that abrogates expression of LIX1, a novel SMA candidate gene of unknown function. To characterize the progression of feline SMA, we assessed pathological changes in muscle and spinal cord from 3 days of age to beyond onset of clinical signs. Electromyographic (EMG) analysis indicating denervation occurred between 10 and 12 weeks, with the first neurological signs occurring at the same time. Compound motor action potential (CMAP) amplitudes were significantly reduced in the soleus and extensor carpi radialis muscles at 8-11 weeks. Quadriceps femoris muscle fibers from affected cats appeared smaller at 10 weeks; by 12 weeks atrophic fibers were more prevalent than in age-matched controls. In affected cats, significant loss of L5 ventral root axons was observed at 12 weeks. By 21 weeks of age, affected cats had 40% fewer L5 motor axons than normal. There was no significant difference in total L5 soma number, even at 21 weeks; thus degeneration begins distal to the cell body and proceeds retrogradely. Morphometric analysis of L5 ventral roots and horns revealed that 4 weeks prior to axon loss, motor axons in affected cats failed to undergo radial enlargement, suggesting a role for the putative disease gene LIX1 in radial growth of axons.
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Affiliation(s)
- Erin N Wakeling
- Genetics Program, Michigan State University East Lansing, Michigan 48824, USA.
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Neurofilament heavy chain expression reveals a unique parasagittal stripe topography in the mouse cerebellum. THE CEREBELLUM 2012; 10:409-21. [PMID: 20127431 DOI: 10.1007/s12311-010-0156-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Despite the general uniformity in cellular composition of the adult cerebellum (Cb), the expression of proteins such as ZebrinII/AldolaseC and the small heat shock protein HSP25 reveal striking patterns of parasagittal Purkinje cell (PC) stripes. Based on differences in the stripe configuration within subsets of lobules, the Cb can be further divided into four anterior-posterior transverse zones: anterior zone (AZ) = lobules I-V, central zone (CZ) = lobules VI-VII, posterior zone (PZ) = lobules VIII and anterior IX, and the nodular zone (NZ) = lobules posterior IX-X. Here we used whole-mount and tissue section immunohistochemistry to show that neurofilament heavy chain (NFH) expression alone divides all lobules of the mouse Cb into a complex series of parasagittal stripes of PCs. We revealed that the striped pattern of NFH in the vermis of the AZ and PZ was complementary to ZebrinII and phospholipase C ß3 (PLCß3), and corresponded to phospholipase C ß4 (PLCß4). In the CZ and NZ the stripe pattern of NFH was complementary to HSP25 and corresponded to PLCß3. The boundaries of the NFH stripes were not always sharply delineated. Instead, a gradual decrease in NFH expression was observed toward the edges of particular stripes, resulting in domains comprised of overlapping expression patterns. Furthermore, the terminal field distributions of mossy and climbing fibers had a complex but consistent topographical alignment with NFH stripes. In summary, NFH expression reveals an exquisite level of Cb stripe complexity that respects the transverse zone divisions and delineates an intricately patterned target field for Cb afferents.
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Ho C, O'Leary ME. Single-cell analysis of sodium channel expression in dorsal root ganglion neurons. Mol Cell Neurosci 2011; 46:159-66. [PMID: 20816971 PMCID: PMC3005531 DOI: 10.1016/j.mcn.2010.08.017] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/19/2010] [Accepted: 08/26/2010] [Indexed: 01/08/2023] Open
Abstract
Sensory neurons of the dorsal root ganglia (DRG) express multiple voltage-gated sodium (Na) channels that substantially differ in gating kinetics and pharmacology. Small-diameter (<25 μm) neurons isolated from the rat DRG express a combination of fast tetrodotoxin-sensitive (TTX-S) and slow TTX-resistant (TTX-R) Na currents while large-diameter neurons (>30 μm) predominately express fast TTX-S Na current. Na channel expression was further investigated using single-cell RT-PCR to measure the transcripts present in individually harvested DRG neurons. Consistent with cellular electrophysiology, the small neurons expressed transcripts encoding for both TTX-S (Nav1.1, Nav1.2, Nav1.6, and Nav1.7) and TTX-R (Nav1.8 and Nav1.9) Na channels. Nav1.7, Nav1.8 and Nav1.9 were the predominant Na channels expressed in the small neurons. The large neurons highly expressed TTX-S isoforms (Nav1.1, Nav1.6, and Nav1.7) while TTX-R channels were present at comparatively low levels. A unique subpopulation of the large neurons was identified that expressed TTX-R Na current and high levels of Nav1.8 transcript. DRG neurons also displayed substantial differences in the expression of neurofilaments (NF200, peripherin) and Necl-1, a neuronal adhesion molecule involved in myelination. The preferential expression of NF200 and Necl-1 suggests that large-diameter neurons give rise to thick myelinated axons. Small-diameter neurons expressed peripherin, but reduced levels of NF200 and Necl-1, a pattern more consistent with thin unmyelinated axons. Single-cell analysis of Na channel transcripts indicates that TTX-S and TTX-R Na channels are differentially expressed in large myelinated (Nav1.1, Nav1.6, and Nav1.7) and small unmyelinated (Nav1.7, Nav1.8, and Nav1.9) sensory neurons.
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Affiliation(s)
- Cojen Ho
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust Street, JAH 265, Philadelphia, PA 19107, USA
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Rostrocaudal analysis of corpus callosum demyelination and axon damage across disease stages refines diffusion tensor imaging correlations with pathological features. J Neuropathol Exp Neurol 2010; 69:704-16. [PMID: 20535036 DOI: 10.1097/nen.0b013e3181e3de90] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Noninvasive assessment of the progression of axon damage is important for evaluating disease progression and developing neuroprotective interventions in multiple sclerosis patients. We examined the cellular responses correlated with diffusion tensor imaging-derived axial (lambda(parallel)) and radial (lambda(perpendicular)) diffusivity values throughout acute (4 weeks) and chronic (12 weeks) stages of demyelination and after 6 weeks of recovery using the cuprizone demyelination of the corpus callosum model in C57BL/6 and Thy1-YFP-16 mice. The rostrocaudal progression of pathological alterations in the corpus callosum enabled spatially and temporally defined correlations of pathological features with diffusion tensor imaging measurements. During acute demyelination, microglial/macrophage activation was most extensive and axons exhibited swellings, neurofilament dephosphorylation, and reduced diameters. Axial diffusivity values decreased in the acute phase but did not correlate with axonal atrophy during chronic demyelination. In contrast, radial diffusivity increased with the progression of demyelination but did not correlate with myelin loss or astrogliosis. Unlike other animal models with progressive neurodegeneration and axon loss, the acute axon damage did not progress to discontinuity or loss of axons even after a period of chronic demyelination. Correlations of reversible axon pathology, demyelination, microglia/macrophage activation, and astrogliosis with regional axial and radial diffusivity measurements will facilitate the clinical application of diffusion tensor imaging in multiple sclerosis patients.
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Shen H, Barry DM, Garcia ML. Distal to proximal development of peripheral nerves requires the expression of neurofilament heavy. Neuroscience 2010; 170:16-21. [PMID: 20633607 DOI: 10.1016/j.neuroscience.2010.07.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Revised: 07/02/2010] [Accepted: 07/07/2010] [Indexed: 01/15/2023]
Abstract
At the initiation of radial growth, neurofilaments are likely to consist primarily of neurofilament light and medium as neurofilament heavy expression is developmentally delayed. To better understand the role of neurofilament heavy in structuring axons, axonal diameter and neurofilament organization were measured in proximal and distal segments of the sciatic nerve and along the entire length of the phrenic nerve. Deletion of neurofilament heavy reduced axonal diameters and neurofilament number in proximal nerve segments. However, neurofilament spacing was greater in proximal versus distal phrenic nerve segments. Taken together, these results suggest that loss of neurofilament heavy reduces radial growth in proximal axonal segments by reducing the accumulation of neurofilaments. As neurofilament heavy expression is developmentally delayed, these results suggest that without neurofilament heavy, the neurofilament network is established in a distal to proximal gradient perhaps to allow distal axonal segments to develop prior to proximal segments.
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Affiliation(s)
- H Shen
- C.S. Bond Life Sciences Center, University of Missouri, 1201 Rollins Street, Columbia, MO 65211, USA
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Reid AJ, Welin D, Wiberg M, Terenghi G, Novikov LN. Peripherin and ATF3 genes are differentially regulated in regenerating and non-regenerating primary sensory neurons. Brain Res 2009; 1310:1-7. [PMID: 19913522 DOI: 10.1016/j.brainres.2009.11.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Revised: 10/24/2009] [Accepted: 11/05/2009] [Indexed: 01/10/2023]
Abstract
Peripheral nerve injury leads to deficient recovery of sensation and a causative factor may be that only 50-60% of primary sensory neurons succeed in regenerating axons after primary nerve repair. In this study, an in vivo rat sciatic nerve injury and regeneration model was combined with laser microdissection and quantitative real-time polymerase chain reaction with the aim of examining the gene expression of regenerative molecules in cutaneous and muscular sensory neurons. Recent studies have identified peripherin and ATF-3 molecules as crucial for neurite outgrowth propagation; our novel findings demonstrate a subpopulation of non-regenerating sensory neurons characterized by a failure to upregulate transcription of these molecules and that a greater peripherin mRNA expression in injured cutaneous neurons may potentiate this subpopulation to regenerate more axons than muscle afferent neurons following injury. The gene expression of the structural neurofilament NF-H is found to be significantly downregulated following injury in both sensory subpopulations.
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Affiliation(s)
- Adam J Reid
- Blond McIndoe Research Laboratories, Tissue Injury and Repair Group, University of Manchester, UK.
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20
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Molecular Mechanisms of Axonal Growth. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 621:1-16. [DOI: 10.1007/978-0-387-76715-4_1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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21
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Wu YJ, Tang YF, Xiao ZC, Bao ZM, He BP. NG2 cells response to axonal alteration in the spinal cord white matter in mice with genetic disruption of neurofilament light subunit expression. Mol Neurodegener 2008; 3:18. [PMID: 18957081 PMCID: PMC2584033 DOI: 10.1186/1750-1326-3-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2008] [Accepted: 10/28/2008] [Indexed: 11/25/2022] Open
Abstract
Background Chondroitin sulphate proteoglycan (NG2) expressing cells, morphologically characterized by multi-branched processes and small cell bodies, are the 4th commonest cell population of non-neuronal cell type in the central nervous system (CNS). They can interact with nodes of Ranvier, receive synaptic input, generate action potential and respond to some pathological stimuli, but the function of the cells is still unclear. We assumed the NG2 cells may play an active role in neuropathogenesis and aimed to determine if NG2 cells could sense and response to the alterations in the axonal contents caused by disruption of neurofilament light subunit (NFL) expression. Results In the early neuropathological development stage, our study showed that the diameter of axons of upper motor neurons of NFL-/- mice decreased significantly while the thickness of their myelin sheath increased remarkably. Although there was an obvious morphological distortion in axons with occasionally partial demyelination, no obvious changes in expression of myelin proteins was detected. Parallel to these changes in the axons and their myelination, the processes of NG2 cells were disconnected from the nodes of Ranvier and extended further, suggesting that these cells in the spinal cord white matter could sense the alteration in axonal contents caused by disruption of NFL expression before astrocytic and microglial activation. Conclusion The structural configuration determined by the NFL gene may be important for maintenance of normal morphology of myelinated axons. The NG2 cells might serve as an early sensor for the delivery of information from impaired neurons to the local environment.
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Affiliation(s)
- Ya Jun Wu
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
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Perrot R, Berges R, Bocquet A, Eyer J. Review of the Multiple Aspects of Neurofilament Functions, and their Possible Contribution to Neurodegeneration. Mol Neurobiol 2008; 38:27-65. [DOI: 10.1007/s12035-008-8033-0] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Accepted: 06/14/2008] [Indexed: 10/21/2022]
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Fornaro M, Lee J, Raimondo S, Nicolino S, Geuna S, Giacobini-Robecchi M. Neuronal intermediate filament expression in rat dorsal root ganglia sensory neurons: An in vivo and in vitro study. Neuroscience 2008; 153:1153-63. [DOI: 10.1016/j.neuroscience.2008.02.080] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 02/14/2008] [Accepted: 02/28/2008] [Indexed: 01/17/2023]
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Gordon T, Bambrick L, Orozco R. Comparison of injury and development in the neuromuscular system. CIBA FOUNDATION SYMPOSIUM 2007; 138:210-26. [PMID: 3058429 DOI: 10.1002/9780470513675.ch13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Comparisons of development and regeneration have suggested that axotomized motoneurons and denervated muscles undergo dedifferentiation to an embryonic state with recovery of adult properties after reinnervation. Using electrophysiological and radioligand-binding techniques to monitor axonal size and numbers of extrajunctional acetylcholine receptors in axotomized motoneurons and denervated muscles respectively, we have demonstrated that this dedifferentiation is limited. We suggest that this limited dedifferentiation may be adaptive for survival, regeneration and reinnervation. Correlative physiological and histochemical studies of reinnervated motor units in cat and rat hindlimb muscles show that the processes of regeneration and reinnervation differ in a number of fundamental ways from developmental processes of axonal growth and muscle innervation. Enlargement of motor units after partial nerve injuries does not appear to be limited to the size of the neonatal motor unit as originally suggested but may be influenced by factors operating at the level of axonal branching. Regeneration after complete and partial nerve injuries is a random process in contrast to the specific nature of the innervation of targets during development. Regenerating axons frequently fail to make connections with their original muscles and newly reinnervated motor units contain muscle fibres which formerly belonged to several different motor units. Despite this misdirection of regenerating nerve fibres, neuromuscular plasticity restores neuromuscular properties to the extent that these are appropriate at the single motor unit level for the gradation of force by the orderly recruitment of units during movement.
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Affiliation(s)
- T Gordon
- Department of Pharmacology, University of Alberta, Edmonton, Canada
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Price DL, Koliatsos VE, Wong PC, Pardo CA, Borchelt DR, Lee MK, Cleveland DW, Griffin JW, Hoffman PN, Cork LC, Sisodia SS. Motor neuron disease and model systems: aetiologies, mechanisms and therapies. CIBA FOUNDATION SYMPOSIUM 2007; 196:3-13; discussion 13-7. [PMID: 8866125 DOI: 10.1002/9780470514863.ch2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The phenotypes of many neurological diseases, including motor neuron disease (amyotrophic lateral sclerosis; ALS) and Alzheimer's disease (AD), are determined by the vulnerabilities of populations of nerve cells and the character/ evolution of cellular abnormalities. Because different cell types respond selectively to individual trophic factors, these factors may be useful in ameliorating pathology in cells that express their cognate receptors. To test therapies for ALS and AD, investigators require model systems. Although there are a variety of models of ALS, two models are particularly attractive: transgenic mice that express human superoxide dismutase 1 (SOD-1) mutations linked to familial ALS develop paralysis associated with a gain of adverse property of the mutant SOD; and axotomy of facial axons in neonatal rats, a manipulation that causes retrograde cell degeneration, which can be ameliorated by several trophic factors.
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Affiliation(s)
- D L Price
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2196, USA
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26
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Hoffman PN. Distinct roles of neurofilament and tubulin gene expression in axonal growth. CIBA FOUNDATION SYMPOSIUM 2007; 138:192-204. [PMID: 3058428 DOI: 10.1002/9780470513675.ch12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Tubulin and the neurofilament (NF) proteins, which are major constituents of the axonal cytoskeleton, play distinct roles in longitudinal and radial growth of axons. The predominantly longitudinal growth of axons in developing neurons correlates with relatively high levels of expression for a particular tubulin gene, encoding the class II beta tubulin isotype, whereas levels of gene expression for two other beta tubulin isotypes (classes I and IV) are comparable in developing and maturing neurons. Gene expression for the 68 kDa NF protein (NF68) is low during longitudinal growth. Conversely, relatively high levels of gene expression for NF68 and low levels for class II beta tubulin in maturing neurons correlate with the radial growth of axons. The developmental pattern of gene expression is recapitulated during axonal regeneration. Expression of the class II beta tubulin isotype correlates with the outgrowth (elongation) of regenerating sprouts.
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Affiliation(s)
- P N Hoffman
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
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Price DL, Cork LC, Struble RG, Kitt CA, Walker LC, Powers RE, Whitehouse PJ, Griffin JW. Dysfunction and death of neurons in human degenerative neurological diseases and in animal models. CIBA FOUNDATION SYMPOSIUM 2007; 126:30-48. [PMID: 3556088 DOI: 10.1002/9780470513422.ch3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The human neurological disorders--amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and Alzheimer's disease (AD)--share certain features: they occur in later stages of adult life; are slowly progressive; and involve specific groups of nerve cells. Different clinical syndromes result from dysfunction and death of these specific groups of neurons. In ALS, patients are weak due to disease of motor neurons in the spinal cord. The clinical features of PD, e.g. slow movements, tremor and rigidity, are attributed, in part, to degeneration of dopaminergic neurons of the substantia nigra. Impairments of cognition and memory in AD result from disease of neurons in a number of regions, including brainstem, basal forebrain, amygdala, hippocampus, and neocortex. In each of these diseases, affected neurons exhibit abnormalities of the neuronal cytoskeleton: in ALS, neurofilaments accumulate and distend proximal motor axons; in PD, nigral perikarya show Lewy bodies-intracytoplasmic inclusions containing neurofilament antigens; in AD, neurons develop neurofibrillary tangles, Hirano bodies, granulovacuolar degeneration and filament-filled neurites in plaques. Certain features of ALS, PD and AD are recapitulated in animal models, three of which are described in this review. Hereditary canine spinal muscular atrophy (HCSMA), a dominantly inherited motor neuron disease, shows many clinical and pathological features in common with ALS, including weakness, muscle atrophy, neurofilamentous swellings of proximal axons, impaired transport of neurofilament proteins, and degeneration of motor neurons. In primates, intoxication with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces a parkinsonian syndrome due to injury of nigral dopaminergic neurons and associated denervation of the striatum. Finally, aged macaques exhibit memory deficits, and their cerebral cortices show senile plaques and filament-filled neurites derived from a variety of transmitter-specific populations of nerve cells. In human diseases, the causes and mechanisms leading to dysfunction and death of nerve cells are unknown. Investigators have begun using a variety of techniques derived from neurobiology to study animal models in an effort to clarify the mechanisms, evolutions, and consequences of structural-chemical abnormalities occurring in different neuronal systems implicated in human disease. Understanding such processes in these models should provide important new insights into the pathogeneses of similar processes occurring in ALS, PD and AD.
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SAHENK ZARIFE. Abnormal Schwann Cell-Axon Interactions in CMT Neuropathies: The Effects of Mutant Schwann Cells on the Axonal Cytoskeleton and Regeneration-Associated Myelination. Ann N Y Acad Sci 2006; 883:415-426. [DOI: 10.1111/j.1749-6632.1999.tb08602.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Corrêa CL, da Silva SF, Lowe J, Tortelote GG, Einicker-Lamas M, Martinez AMB, Allodi S. Identification of a neurofilament-like protein in the protocerebral tract of the crab Ucides cordatus. Cell Tissue Res 2004; 318:609-15. [PMID: 15480795 DOI: 10.1007/s00441-004-0992-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2004] [Accepted: 09/06/2004] [Indexed: 11/28/2022]
Abstract
Neurofilaments (NFs) have not been observed in crustaceans using conventional electron microscopy, and intermediate filaments have never been described in crustaceans and other arthropods by immunocytochemistry. Since polypeptides, labeled by the NN18-clone antibody, were revealed on microtubule side-arms of crayfish, we have tested, in this study, whether proteins similar to mammalian NFs are present in the protocerebral tract (PCT) of the crab Ucides cordatus. We used immunohistochemistry for light microscopy with monoclonal antibodies against three different NF subunits, high (NF-H), medium (NF-M), and light (NF-L). Labeling was observed with the NN18-clone, which recognizes NF-M. In order to confirm the results obtained with the immunohistochemical reactions, Western blotting, using the three primary antibodies, was performed and the presence of NF-M was confirmed. The NN18-clone monoclonal antibody recognized a protein of approximately 160 kDa, similar to the mammalian NF-M protein, but NF-L and NF-H were not recognized. Conventional transmission electron microscopy was used to observe the ultrastructural components of the axons and immunoelectron microscopy was used to show the distribution of the NF-M-like polypeptides along cytoskeletal elements of the PCT. Our results agree with previous studies on crustacean NF proteins that have reported negative immunoreactions against NF-H and NF-L subunits and positive immunoreactions against the mammalian NF-M subunit. However, the protein previously referred to as P600 and recognized by the NN18-clone, has a very high molecular weight, thus, being different from mammalian NF-M subunit and from the protein revealed now in our study.
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Affiliation(s)
- Clynton Lourenço Corrêa
- Departamento de Histologia e Embriologia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, 21941-590, Rio de Janeiro, Brazil
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Abstract
Intermediate filaments, actin-containing microfilaments and microtubules are the three main cytoskeletal systems of vertebrate and many invertebrate cells. Although these systems are composed of distinctly different proteins, they are in constant and intimate communication with one another. Understanding the molecular basis of this cytoskeletal crosstalk is essential for determining the mechanisms that underlie many cell-biological phenomena. Recent studies have revealed that intermediate filaments and their associated proteins are important components in mediating this crosstalk.
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Affiliation(s)
- Lynne Chang
- Feinberg School of Medicine, Northwestern University, Department of Cell and Molecular Biology, 303 East Chicago Avenue, Chicago, Illinois 60611, USA.
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Helfand BT, Chang L, Goldman RD. Intermediate filaments are dynamic and motile elements of cellular architecture. J Cell Sci 2004; 117:133-41. [PMID: 14676269 DOI: 10.1242/jcs.00936] [Citation(s) in RCA: 196] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Recent evidence showing that intermediate filaments (IFs) are dynamic, motile elements of the cytoskeletal repertoire of vertebrate cells has overturned the long-standing view that they simply form static 'space filling' cytoplasmic networks. In fact, many types of IF are now known to engage in a remarkable array of movements that are closely associated with their assembly, disassembly and subcellular organization. Some of these motile properties are intrinsic to IFs and others are attributable to molecular crosstalk with either microtubules or actin-containing microfilaments. This crosstalk is, to a large extent, mediated by molecular motors, including conventional kinesin and cytoplasmic dynein. These motors are responsible for the high-speed delivery of nonfilamentous IF precursors and short filaments to specific regions of the cytoplasm, where they assemble into long IFs. Interestingly, the patterns and speeds of IF movements vary in different cell types and even within different regions of the same cell. These differences in motility may be related to their interactions with different types of molecular motor and/or other factors, such as IF-associated proteins.
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Affiliation(s)
- Brian T Helfand
- Feinberg School of Medicine, Northwestern University, Department of Cell and Molecular Biology, 303 E. Chicago Avenue, Chicago, IL 60611, USA
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Helfand BT, Mendez MG, Pugh J, Delsert C, Goldman RD. A role for intermediate filaments in determining and maintaining the shape of nerve cells. Mol Biol Cell 2003; 14:5069-81. [PMID: 14595112 PMCID: PMC284808 DOI: 10.1091/mbc.e03-06-0376] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
To date, the functions of most neural intermediate filament (IF) proteins have remained elusive. Peripherin is a type III intermediate filament (IF) protein that is expressed in developing and in differentiated neurons of the peripheral and enteric nervous systems. It is also the major IF protein expressed in PC12 cells, a widely used model for studies of peripheral neurons. Dramatic increases in peripherin expression have been shown to coincide with the initiation and outgrowth of axons during development and regeneration, suggesting that peripherin plays an important role in axon formation. Recently, small interfering RNAs (siRNA) have provided efficient ways to deplete specific proteins within mammalian cells. In this study, it has been found that peripherin-siRNA depletes peripherin and inhibits the initiation, extension, and maintenance of neurites in PC12 cells. Furthermore, the results of these experiments demonstrate that peripherin IF are critical determinants of the overall shape and architecture of neurons.
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Affiliation(s)
- Brian T Helfand
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
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Walbeehm ET, Dudok van Heel EBM, Kuypers PDL, Terenghi G, Hovius SER. Nerve compound action current (NCAC) measurements and morphometric analysis in the proximal segment after nerve transection and repair in a rabbit model. J Peripher Nerv Syst 2003; 8:108-15. [PMID: 12795715 DOI: 10.1046/j.1529-8027.2003.03014.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the evaluation of nerve regeneration using magneto-neurography (MNG), the proximal segment showed a reproducible decrease in peak-peak amplitude of the nerve compound action current's (NCAC) of 60%. To explain these changes, morphometry of myelinated axons in the proximal segment is compared to the MNG signals. A standardised nerve transection and reconstruction was performed in rabbits. NCACs were measured approximately 5 cm proximal to the lesion from operated and control nerves after 12 weeks. Histological samples were taken from the same area of the nerve where the NCACs were obtained. Results showed a decrease of the peak-peak amplitude of the NCAC of 57% compared to the control. Conduction velocity decreased 15% (not significant). Morphometry elicited a decrease in larger (10-15 microm) axons (284 +/- 134 vs 82 +/- 55) and an increase in smaller (2-5 microm) axons (1445 +/- 360 vs 1921 +/- 393). A strong correlation existed between the decrease in amplitude and the decrease in larger axons (0.85). Peak-peak amplitude varies approximately with the square of the diameter axon. Therefore, because peak-peak amplitude is mainly dependent on the larger-diameter axons, the decrease in peak-peak amplitude of the NCACs may be explained by a decrease in numbers of 10-15-microm axons.
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Affiliation(s)
- Erik T Walbeehm
- Department of Plastic and Reconstructive Surgery, Ee 1591, UHR Dijkzigt and Erasmus University Rotterdam, Dr Molewaterplein 50, PO Box 1738, 3000 Dr Rotterdam, The Netherlands.
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Marques SA, Taffarel M, Blanco Martinez AM. Participation of neurofilament proteins in axonal dark degeneration of rat's optic nerves. Brain Res 2003; 969:1-13. [PMID: 12676359 DOI: 10.1016/s0006-8993(02)03834-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Neurofilaments (NF) are neuronal intermediate filaments formed by three different subunits: high (NF-H), medium (NF-M) and light (NF-L). They are responsible for the determination and maintenance of axon caliber. Accumulation of NF or their immunoreactive products are components of several neurodegenerative disease lesions, such as neurofibrillary tangles, Lewy bodies and the spheroids of amyotrophic lateral sclerosis. Also, cytoskeletal breakdown is one of the first ultrastructural changes occurring after nerve crush or section. In the present study, Wistar rats were subjected to bilateral enucleation to induce Wallerian degeneration of optic nerve fibers and perfused 24 h, 48 h and 1 week later. Optic nerve segments were processed for electron microscopy (EM), light microscopy immunofluorescence (LM) and immunoelectronmicroscopy (IEM) for NF subunit detection. LM for NF of control nerves showed a slightly different pattern and intensity for each subunit, with more intense staining of NF-M and NF-H and less intense staining of NF-L. This reaction did not change considerably at 48 h, but was severely reduced 1 week after enucleation. Results of EM showed fibers in: (1) partial cytoskeleton degeneration or (2) watery degeneration or (3) dark degeneration. The number of dark degenerating axons was statistically higher at the latest time-interval studied. Neurofilament clumping areas and dark degenerating axons showed positive immunostaining for the three neurofilaments subunits when examined by IEM. These results suggest that dark degenerating axons develop from areas of neurofilament aggregation. We may also conclude that NF proteins participate in the process of axonal dark degeneration.
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Affiliation(s)
- Suelen Adriani Marques
- Departamento de Histologia e Embriologia, Bloco F, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Av. Brig. Trompowsky s/n, 21941-540 RJ, Rio de Janeiro, Brazil
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Abstract
Increasing evidence indicates that insulin-like growth factor-I (IGF-I) has an important role in oligodendrocyte development. In this study, we examined myelination during postnatal development in IGF-I knock-out (KO) mice by assessing myelin staining, the expression of myelin basic protein (MBP) and proteolipid protein (PLP), two major myelin-specific proteins, and the number of oligodendrocytes and their precursors. For comparison, we also measured the expression of median subunit of the neuron-specific intermediate filament, M-neurofilament (M-NF), to obtain an index of the effects of IGF-I deficiency on neurons. We found that myelin staining, MBP and PLP expression, and the percentage of oligodendrocytes and their precursors are significantly reduced in all brain regions of developing IGF-I KO mice but are similar to controls in adult IGF-I KO mice. In contrast, the abundance of M-NF was decreased in both the developing and adult brain of IGF-I KO mice. We also found that IGF-II protein abundance is increased in the brains of IGF-I KO mice. Our data indicate, therefore, that myelination during early development is altered in the absence of IGF-I by mechanisms that involve a reduction in oligodendrocyte proliferation and development. Although neuronal actions cannot be excluded in the myelin normalization, the reduced axonal growth suggested by the reduced M-NF expression makes a role for neuronal factors less compelling. These data suggest that IGF-I plays a significant role in myelination during normal early development and that IGF-II can compensate in part for IGF-I actions on myelination.
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López JMA, Alvarez J. The Microtubular Pattern Changes at the Spinal Cord-Root Junction and Reverts at the Root-Peripheral Nerve Junction in Sensory and Motor Fibres of the Rat. Eur J Neurosci 2002; 2:873-878. [PMID: 12106094 DOI: 10.1111/j.1460-9568.1990.tb00398.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the rat, we studied the microtubular content of central nervous system (CNS) axons (pyramidal tract, dorsal funiculus, and intracord domain of motor axons), of radicular axons (ventral and dorsal roots), and of peripheral axons (sural and lateral gastrocnemius nerves). The microtubular density had an inverse relationship with the size of the axon. Within the CNS, values ranged from over 120 microtubules/microm2 for axons smaller than 0.1 microm2 of the pyramidal tract and dorsal funiculus to 24 for 3-microm motor axons (area, 7 microm2) in their spinal cord domain. Peripheral nerve and CNS axons of the same size had comparable microtubular densities. In contrast, the microtubular density of dorsal and ventral root axons was one half that of CNS or peripheral nerve axons of equal calibre. Considered along the axon, the microtubular density of motor and sensory fibres is high in the CNS domain, low in the root, and high again in the peripheral nerve domain. These observations are inconsistent with the notion that the cytoskeleton moves coherently away from the perikaryon. We conclude that the axonal microtubular content accords with the calibre of the fibre and with the anatomical region where it courses. We propose that axonal microtubules are regulated by local cues.
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Affiliation(s)
- José Manuel A. López
- Unidad de Neurobiología Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica, Casilla 114-D, Santiago, Chile
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Yin Q, Kemp GJ, Yu LG, Wagstaff SC, Frostick SP. Expression of Schwann cell-specific proteins and low-molecular-weight neurofilament protein during regeneration of sciatic nerve treated with neurotrophin-4. Neuroscience 2001; 105:779-83. [PMID: 11516841 DOI: 10.1016/s0306-4522(01)00216-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Neurotrophin-4 acts as a potent survival factor for subpopulations of motoneurons. To investigate its effect on Schwann cell sheath and axonal proteins during peripheral nerve regeneration, sciatic nerves in adult rats were transected and repaired, and fibrin glue containing neurotrophin-4 injected around the repair site. At 5, 15, 30 and 60 days after repair, 5-mm nerve segments distal to the repair were collected, and western blotting was used to measure myelin-associated glycoprotein, myelin basic protein and low-molecular-weight neurofilament protein. In control groups these dramatically declined at 5 and 15 days then increased from 30 and 60 days. However, in the neurotrophin-4 group there was a significant increase (to several times basal values) in myelin-associated glycoprotein and myelin basic protein at 5-15 days. The relatively small increases (<7%) in Schwann cell numbers suggest that this is mainly due to increased synthesis per cell. The neurotrophin-4 group also showed a small but significant increase at 15 days in low-molecular-weight neurofilament protein, which however remained much lower than basal. We conclude that neurotrophin-4 regulates the expression of myelin-associated glycoprotein, myelin basic protein, and to a lesser extent low-molecular-weight neurofilament protein, during peripheral nerve regeneration.
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Affiliation(s)
- Q Yin
- Department of Musculoskeletal Science, University of Liverpool, UK.
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38
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Sheykholeslami K, Kaga K, Mizutani M. Auditory nerve fiber differences in the normal and neurofilament deficient Japanese quail. Hear Res 2001; 159:117-24. [PMID: 11520639 DOI: 10.1016/s0378-5955(01)00326-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A primary axonal disease affecting the central and peripheral nervous system was discovered in a mutant strain of the Japanese quail, named quiver (Quv). We have previously demonstrated altered auditory evoked potentials in the neurofilament (NF) deficient quail. In this current study we attempt to find relationships between the auditory evoked potential results and the histo-pathological abnormalities of the auditory neurons. No abnormalities in the external auditory meatus and tympanic cavity were observed in either Quv or control quails and the ganglion cell bodies and their nuclei appeared normal by light microscopy. The myelin staining pattern was found to be similar in both strains with hematoxylin and eosin and Klüver-Barrera staining. The frequency histograms of fiber and axonal diameters of myelinated fibers showed an unimodal pattern in both strains. In Quv quails myelinated fibers and their axoplasm were smaller in diameter than in controls resulting in smaller neural tissue mass. In electron microscopic observation the axons of the Quv quail were composed of mitochondria and microtubules and smooth endoplasmic reticuli. In Quv quail electron micrographs of cochlear nerve myelinated fibers NFs were not seen in the axons and the neuronal cell bodies. Our current findings indicate that the previously reported reduction of conduction velocity of auditory evoked potentials may be due to smaller fiber and/or axonal diameter. The g-ratio, myelin thickness and fiber circularity were found to be the same for both strains. In conclusion, loss of axonal cytoskeletal elements (NFs) correlates well with our electrophysiological findings. Reduced conduction velocity and severely distorted auditory evoked potentials in NF deficient quails seem to be primarily due to axonal hypotrophy.
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Affiliation(s)
- K Sheykholeslami
- Department of Otolaryngology, University of Tokyo, Tokyo 113-0033, Japan.
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39
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Gordon T, Rafuse VF. Size of myelinated nerve fibres is not increased by expansion of the peripheral field in cats. J Physiol 2001; 532:835-49. [PMID: 11313450 PMCID: PMC2278581 DOI: 10.1111/j.1469-7793.2001.0835e.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
This study tests the hypothesis that target size regulates the size of myelinated sensory and motor fibres in peripheral nerves. Cat medial gastrocnemius (MG) muscles were partially denervated and the size of the remaining nerve fibres that sprouted was examined 6.4 +/- 0.9 months later to determine whether nerve fibre size increased with target size. Electrophysiological and morphometric analyses were used to quantify myelinated nerve fibre size. Charge measurements from dorsal and ventral roots were used to electrophysiologically quantify the relative number of cut nerve fibres and the average size of the remaining intact sensory and motor nerve fibres. Medial gastrocnemius muscle and motor unit forces provided indirect measurements of the increase in target size. Conduction velocities and amplitude of unitary action potentials of motor nerve fibres innervating single motor units were also measured after partial denervation. Electrophysiological measurements of nerve fibre size and morphometric measurements of outer fibre perimeters and fibre areas concurred and demonstrated that myelinated nerve fibres supplying partially denervated MG muscles did not increase in size in parallel with the increase in the target size. Thus, unlike non-myelinated nerve fibres, the size of myelinated nerve fibres does not increase as target size increases. Retrograde control of size in non-myelinated but not in myelinated nerve fibres demonstrates differences in plasticity of neurons in the somatic and autonomic nervous systems.
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Affiliation(s)
- T Gordon
- Department of Pharmacology, Division of Neuroscience, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
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40
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Hall GF, Chu B, Lee S, Liu Y, Yao J. The single neurofilament subunit of the lamprey forms filaments and regulates axonal caliber and neuronal size in vivo. CELL MOTILITY AND THE CYTOSKELETON 2000; 46:166-82. [PMID: 10913964 DOI: 10.1002/1097-0169(200007)46:3<166::aid-cm2>3.0.co;2-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Neurofilaments (NFs) are composed of a heteropolymer of three related subunits in mammalian neurons, where they are a major component of the cytoskeleton in large neurons and are thought to regulate axonal diameter. NFs in the lamprey, while ultrastructurally and functionally indistinguishable from mammalian NFs, are polymers of a single subunit protein, NF180. In this study, we use the simplicity of lamprey NFs and the accessibility of the lamprey central nervous system (CNS) to examine the effects of overproducing NFs in an identified giant neuron in vivo, and thus to elucidate the role of NFs in regulating neuronal size and axonal caliber in the vertebrate CNS. We show that overexpression of NF180 tagged with a variant of Green Fluorescent Protein (EYFP) in identified lamprey neurons (ABCs) and in human neuroblastoma (NB2a) cells results in the assembly of exogenous NF180 into ultrastructurally normal NFs that are tightly packed and unphosphorylated. These accumulate in the somata of NB2a cells and produce somatic swelling by 3 days post-transfection. NF180 overexpression in lamprey ABCs in vivo causes exogenous NFs to accumulate in ABC axons, somata, and dendrites, and induces a significant increase in axonal diameter without increasing axonal NF packing density. Overexpression of EYFP alone has none of these effects. We conclude that NF180 normally plays a critical role in determining axonal caliber in ABCs and may influence neuronal size in situations where NFs accumulate in the soma, such as after axonal injury.
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Affiliation(s)
- G F Hall
- Center for Cellular Neuroscience and Neurodegeneration Research, Department of Biological Sciences, University of Massachusetts, Lowell 02115, USA.
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41
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Axonal transport of microtubule-associated protein 1B (MAP1B) in the sciatic nerve of adult rat: distinct transport rates of different isoforms. J Neurosci 2000. [PMID: 10704485 DOI: 10.1523/jneurosci.20-06-02112.2000] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cytoskeletal proteins are axonally transported with slow components a and b (SCa and SCb). In peripheral nerves, the transport velocity of SCa, which includes neurofilaments and tubulin, is 1-2 mm/d, whereas SCb, which includes actin, tubulin, and numerous soluble proteins, moves as a heterogeneous wave at 2-4 mm/d. We have shown that two isoforms of microtubule-associated protein 1B (MAP1B), which can be separated on SDS polyacrylamide gels on the basis of differences in their phosphorylation states (band I and band II), were transported at two different rates. All of band I MAP1B moved as a coherent wave at a velocity of 7-9 mm/d, distinct from slow axonal transport components SCa and SCb. Several other proteins were detected within the component that moved at the velocity of 7-9 mm/d, including the leading wave of tubulin and actin. The properties of this component define a distinct fraction of the slow axonal transport that we suggest to term slow component c (SCc). The relatively fast transport of the phosphorylated MAP1B isoform at 7-9 mm/d may account for the high concentration of phosphorylated MAP1B in the distal end of growing axons. In contrast to band I MAP1B, the transport profile of band II was complex and contained components moving with SCa and SCb and a leading edge at SCc. Thus, MAP1B isoforms in different phosphorylation states move with distinct components of slow axonal transport, possibly because of differences in their abilities to associate with other proteins.
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42
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Ma D, Himes BT, Shea TB, Fischer I. Axonal transport of microtubule-associated protein 1B (MAP1B) in the sciatic nerve of adult rat: distinct transport rates of different isoforms. J Neurosci 2000; 20:2112-20. [PMID: 10704485 PMCID: PMC6772501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
Cytoskeletal proteins are axonally transported with slow components a and b (SCa and SCb). In peripheral nerves, the transport velocity of SCa, which includes neurofilaments and tubulin, is 1-2 mm/d, whereas SCb, which includes actin, tubulin, and numerous soluble proteins, moves as a heterogeneous wave at 2-4 mm/d. We have shown that two isoforms of microtubule-associated protein 1B (MAP1B), which can be separated on SDS polyacrylamide gels on the basis of differences in their phosphorylation states (band I and band II), were transported at two different rates. All of band I MAP1B moved as a coherent wave at a velocity of 7-9 mm/d, distinct from slow axonal transport components SCa and SCb. Several other proteins were detected within the component that moved at the velocity of 7-9 mm/d, including the leading wave of tubulin and actin. The properties of this component define a distinct fraction of the slow axonal transport that we suggest to term slow component c (SCc). The relatively fast transport of the phosphorylated MAP1B isoform at 7-9 mm/d may account for the high concentration of phosphorylated MAP1B in the distal end of growing axons. In contrast to band I MAP1B, the transport profile of band II was complex and contained components moving with SCa and SCb and a leading edge at SCc. Thus, MAP1B isoforms in different phosphorylation states move with distinct components of slow axonal transport, possibly because of differences in their abilities to associate with other proteins.
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Affiliation(s)
- D Ma
- Department of Neurobiology and Anatomy, MCP Hahnemann University, Philadelphia, Pennsylvania 19129, USA
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43
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Vaidya VA, Terwilliger RZ, Duman RS. Alterations in heavy and light neurofilament proteins in hippocampus following chronic ECS administration. Synapse 2000; 35:137-43. [PMID: 10611639 DOI: 10.1002/(sici)1098-2396(200002)35:2<137::aid-syn6>3.0.co;2-f] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Chronic administration of electroconvulsive seizures (ECS), one of the most effective treatments for depression, induces sprouting of the mossy fibers in the hippocampus. This sprouting requires chronic ECS administration and appears to occur in the absence of hilar neuronal loss. Dynamic regulation of cytoarchitecture plays a vital role in such profound alterations of neuronal morphology. In particular, alterations in the neurofilament protein subunits have been implicated in neurite sprouting, neuronal regeneration, and growth. The present study was carried out to determine the influence of chronic ECS administration on the neurofilament subunits and other molecular markers of neuronal plasticity. Chronic ECS administration decreases the level of phosphorylated heavy neurofilament subunit (NF-H). In addition, the total level of the light neurofilament subunit (NF-L) but not the medium neurofilament subunit (NF-M) is decreased following chronic ECS treatment. Other cytoskeletal proteins, including actin, microtubule-associated protein (MAP-2), and tau, are not influenced by chronic ECS administration. Expression of the growth-associated protein (F1/GAP-43) also remains unchanged following chronic ECS treatment. The changes observed in neurofilaments may be part of the cytoskeletal remodeling that contributes to the mossy fiber sprouting induced by chronic ECS treatment.
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Affiliation(s)
- V A Vaidya
- Laboratory of Molecular Psychiatry, Departments of Psychiatry and Pharmacology, Yale University School of Medicine, Connecticut Mental Health Center, New Haven, Connecticut 06508, USA
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44
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Elder GA, Friedrich VL, Margita A, Lazzarini RA. Age-related atrophy of motor axons in mice deficient in the mid-sized neurofilament subunit. J Cell Biol 1999; 146:181-92. [PMID: 10402469 PMCID: PMC2199745 DOI: 10.1083/jcb.146.1.181] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/1998] [Accepted: 06/03/1999] [Indexed: 11/29/2022] Open
Abstract
Neurofilaments are central determinants of the diameter of myelinated axons. It is less clear whether neurofilaments serve other functional roles such as maintaining the structural integrity of axons over time. Here we show that an age-dependent axonal atrophy develops in the lumbar ventral roots of mice with a null mutation in the mid-sized neurofilament subunit (NF-M) but not in animals with a null mutation in the heavy neurofilament subunit (NF-H). Mice with null mutations in both genes develop atrophy in ventral and dorsal roots as well as a hind limb paralysis with aging. The atrophic process is not accompanied by significant axonal loss or anterior horn cell pathology. In the NF-M-null mutant atrophic ventral root, axons show an age-related depletion of neurofilaments and an increased ratio of microtubules/neurofilaments. By contrast, the preserved dorsal root axons of NF-M-null mutant animals do not show a similar depletion of neurofilaments. Thus, the lack of an NF-M subunit renders some axons selectively vulnerable to an age-dependent atrophic process. These studies argue that neurofilaments are necessary for the structural maintenance of some populations of axons during aging and that the NF-M subunit is especially critical.
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Affiliation(s)
- Gregory A. Elder
- Department of Psychiatry, Mount Sinai School of Medicine, New York, NY 10029
| | - Victor L. Friedrich
- Brookdale Center for Developmental and Molecular Biology, Mount Sinai School of Medicine, New York, NY 10029
| | - Alla Margita
- Department of Psychiatry, Mount Sinai School of Medicine, New York, NY 10029
| | - Robert A. Lazzarini
- Brookdale Center for Developmental and Molecular Biology, Mount Sinai School of Medicine, New York, NY 10029
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45
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Schumacher PA, Eubanks JH, Fehlings MG. Increased calpain I-mediated proteolysis, and preferential loss of dephosphorylated NF200, following traumatic spinal cord injury. Neuroscience 1999; 91:733-44. [PMID: 10366029 DOI: 10.1016/s0306-4522(98)00552-1] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the hypothesis that the Ca2+-activated protease calpain is involved in the pathophysiology of spinal cord injury, and is linked to the proteolytic degradation of cytoskeletal proteins. We report here that levels of calpain I (mu-calpain)-mediated spectrin breakdown products are increased by 15 min post-injury, with peak levels reached by 2 h post-injury. The dephosphorylated form of the neurofilament protein NF200 is substantially lost over the same time-period. A 35-g compressive injury was applied to the midthoracic rat spinal cord for 1 min, and animals were killed at 15 min, 1, 2, 4, 8, 16, and 24 h post-injury. Calpain I-mediated spectrin breakdown products accumulated post-injury, with peak levels reached at 2 h. Secondly, we have demonstrated a progressive loss of the 200,000 mol. wt neurofilament protein NF200, a cytoskeletal calpain substrate, which began within 1-2 h post-injury. Densitometric analyses confirmed that loss of NF200 is a substrate-specific phenomenon, since (i) dephosphorylated NF200 was preferentially lost while phosphorylated NF200 was relatively spared, and (ii) actin, which is not a substrate for calpain, was relatively spared following spinal cord injury. Finally, we demonstrated calpain I-mediated spectrin breakdown within NF200-positive neuronal processes post-injury. We conclude that the accumulation of spectrin breakdown products is temporally and spatially correlated with loss of dephosphorylated NF200 after spinal cord injury.
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Affiliation(s)
- P A Schumacher
- Playfair Neuroscience Unit and The Toronto Hospital Research Institute, University of Toronto, The Toronto Hospital, Ontario, Canada
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46
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McIlwain DL, Hoke VB. Magnitude, laterality, and uniformity of swelling in axotomized spinal motoneurons: lack of evidence for influence by the distal stump. Exp Neurol 1999; 157:161-8. [PMID: 10222119 DOI: 10.1006/exnr.1999.7051] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Injury to frog lumbar motor axons produces a coordinated, allometric enlargement of the nucleolus, nucleus, and cell body of the injured neuron. The mechanisms by which swelling is initiated and sustained are not known. In this study, we have sought evidence for a role of the severed distal stump in the magnitude, laterality, and uniformity of the swelling response in frog spinal motoneurons. We find that swelling of motoneuron nucleoli, nuclei, and perikarya after unilateral spinal nerve transection is exclusively ipsilateral and uniform among motoneurons of different sizes. Removal of the severed distal stump does not affect the magnitude, unilaterality, or uniformity of the swelling responses. Thus, the distal stump appears to play no role in initiating swelling following spinal nerve transection.
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Affiliation(s)
- D L McIlwain
- Curriculum in Neurobiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
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47
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Mi R, Shi X, Liu S, Zhou C, Wang J, Fan M. Expression of neurofilament gene in spinal motoneurons during neural regeneration. CHINESE SCIENCE BULLETIN-CHINESE 1999. [DOI: 10.1007/bf02896279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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48
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Williamson TL, Cleveland DW. Slowing of axonal transport is a very early event in the toxicity of ALS-linked SOD1 mutants to motor neurons. Nat Neurosci 1999; 2:50-6. [PMID: 10195180 DOI: 10.1038/4553] [Citation(s) in RCA: 434] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Mutations in copper/zinc superoxide dismutase 1 (SOD1), primary causes of human amyotrophic lateral sclerosis (ALS), provoke motor neuron death through an unidentified toxic property. The known neurofilament-dependent slowing of axonal transport, combined with the prominent misaccumulation of neurofilaments in ALS, suggests that an important aspect of toxicity may arise from damage to transport. Here we verify this hypothesis for two SOD1 mutations linked to familial ALS. Reduced transport of selective cargoes of slow transport, especially tubulin, arises months before neurodegeneration. For one mutant, this represents the earliest detectable abnormality. Thus, damage to the cargoes or machinery of slow transport is an early feature of toxicity mediated by mutant SOD1.
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Affiliation(s)
- T L Williamson
- Ludwig Institute for Cancer Research, University of California, San Diego, La Jolla 92093, USA
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49
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Elder GA, Friedrich VL, Kang C, Bosco P, Gourov A, Tu PH, Zhang B, Lee VM, Lazzarini RA. Requirement of heavy neurofilament subunit in the development of axons with large calibers. J Cell Biol 1998; 143:195-205. [PMID: 9763431 PMCID: PMC2132822 DOI: 10.1083/jcb.143.1.195] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/1998] [Revised: 08/05/1998] [Indexed: 12/02/2022] Open
Abstract
Neurofilaments (NFs) are prominent components of large myelinated axons. Previous studies have suggested that NF number as well as the phosphorylation state of the COOH-terminal tail of the heavy neurofilament (NF-H) subunit are major determinants of axonal caliber. We created NF-H knockout mice to assess the contribution of NF-H to the development of axon size as well as its effect on the amounts of low and mid-sized NF subunits (NF-L and NF-M respectively). Surprisingly, we found that NF-L levels were reduced only slightly whereas NF-M and tubulin proteins were unchanged in NF-H-null mice. However, the calibers of both large and small diameter myelinated axons were diminished in NF-H-null mice despite the fact that these mice showed only a slight decrease in NF density and that filaments in the mutant were most frequently spaced at the same interfilament distance found in control. Significantly, large diameter axons failed to develop in both the central and peripheral nervous systems. These results demonstrate directly that unlike losing the NF-L or NF-M subunits, loss of NF-H has only a slight effect on NF number in axons. Yet NF-H plays a major role in the development of large diameter axons.
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Affiliation(s)
- G A Elder
- Department of Psychiatry, Mount Sinai School of Medicine, New York, New York 10029, USA
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50
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Borchelt DR, Wong PC, Becher MW, Pardo CA, Lee MK, Xu ZS, Thinakaran G, Jenkins NA, Copeland NG, Sisodia SS, Cleveland DW, Price DL, Hoffman PN. Axonal transport of mutant superoxide dismutase 1 and focal axonal abnormalities in the proximal axons of transgenic mice. Neurobiol Dis 1998; 5:27-35. [PMID: 9702785 DOI: 10.1006/nbdi.1998.0178] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Superoxide dismutase 1 (SOD1), a ubiquitously expressed enzyme, detoxifies superoxide radicals and participates in copper homeostasis. Mutations in this enzyme have been linked to a subset of autosomal dominant cases of familial amyotrophic lateral sclerosis (FALS), a disorder characterized by selective degeneration of motor neurons. Transgenic mice expressing FALS mutant human (Hu) SOD1 at high levels develop a motor neuron disease, indicating that mutant Hu SOD1 gains properties that are particularly toxic to motor neurons. In this report, we demonstrate that transgenic mice expressing Hu SOD1 with the G37R FALS mutation, but not mice expressing wild-type enzyme, develop focal increases in immunoreactivity in the proximal axons of spinal motor neurons. This SOD1 immunoreactivity and immunoreactivity to hypophosphorylated neurofilament H epitopes are found adjacent to small vacuoles in axons. Using metabolic radiolabeling methods, we show that mutant G37R HuSOD1 as well as endogenous mouse SOD1 are transported anterograde in slow component b in motor and sensory axons of the sciatic nerve. Together, these findings suggest that anterogradely transported mutant SOD1 may act locally to damage motor axons.
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Affiliation(s)
- D R Borchelt
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
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