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Tu WY, Xu W, Zhang K, Shen C. Whole-mount staining of neuromuscular junctions in adult mouse diaphragms with a sandwich-like apparatus. J Neurosci Methods 2020; 350:109016. [PMID: 33316317 DOI: 10.1016/j.jneumeth.2020.109016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 11/22/2020] [Accepted: 11/26/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND Investigation of neuromuscular junction (NMJ) morphology by immunochemistry can provide important insights into the physiological and pathological status of neuromuscular disorders. Sectioning and muscle fiber tearing are commonly required to prepare experimentally accessible samples, while muscles that are flat and thin can be investigated with whole-mount immunohistochemistry for a comprehensive overview of the entire innervation pattern. The diaphragm is important for respiratory function and one of the flat muscles frequently used for studying neuromuscular development as well as neuromuscular pathology. Nevertheless, techniques for reliable whole-mount immunolabeling of adult diaphragms are lacking, mainly due to the poor tissue permeability of labeling reagents. An effective approach for researchers to be able to comprehensively visualize and characterize NMJ defects of the adult diaphragm in mouse models is therefore of clear importance. NEW METHOD This protocol demonstrates that the diaphragm can be thinned and spread out under even pressure using two Perspex boards for better whole-mount immunostaining. RESULTS The expanded mouse diaphragm allows the comprehensive assessment of a number of NMJ phenotypes. COMPARISON WITH EXISTING METHODS Most peer-reviewed and online protocols can be applied to the embryonic diaphragm but fail to show the entire innervation pattern in the adult diaphragm. Our method provides a convenient approach and present a clear innervation pattern that increases the reliability of the assessment of NMJ phenotypes in the diaphragm. CONCLUSIONS This simple method for whole-mount immunostaining of the adult diaphragm will allow researchers to perform a detailed analysis of the neuromuscular system in mouse models.
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Affiliation(s)
- Wen-Yo Tu
- Department of Neurobiology, The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China.
| | - Wentao Xu
- Department of Neurobiology, The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China
| | - Kejing Zhang
- Department of Neurobiology, The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China
| | - Chengyong Shen
- Department of Neurobiology, The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China; Department of Neurobiology, Key Laboratory of Medical Neurobiology of Zhejiang Province, School of Medicine, Zhejiang University, Zhejiang, China.
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Fenn JD, Monsma PC, Brown A. Axonal neurofilaments exhibit frequent and complex folding behaviors. Cytoskeleton (Hoboken) 2019; 75:258-280. [PMID: 29683261 DOI: 10.1002/cm.21448] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 03/30/2018] [Accepted: 04/03/2018] [Indexed: 01/19/2023]
Abstract
Neurofilaments are flexible cytoskeletal polymers that are capable of folding and unfolding between their bouts of bidirectional movement along axons. Here we present a detailed characterization of this behavior in cultured neurons using kymograph analysis with approximately 30 ms temporal resolution. We analyzed 781 filaments ranging from 0.6-42 µm in length. We observed complex behaviors including pinch folds, hairpin folds, orientation changes (flips), and occasional severing and annealing events. On average, the filaments spent approximately 40% of their time in some sort of folded configuration. A small proportion of filaments (4%) moved while folded, but most (96%) moved in an outstretched configuration. Collectively, our observations suggest that motors may interact with neurofilaments at multiple points along their length, but preferentially at their ends. In addition, the prevalence of neurofilament folding and the tendency of neurofilaments to straighten out when they move, suggest that an important function of the movement of these polymers in axons may be to maintain them in an outstretched and longitudinally co-aligned configuration. Thus, neurofilament movement may function as much to organize these polymers as to move them, and this could explain why they spend so much time engaged in apparently unproductive bidirectional movement.
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Affiliation(s)
- J Daniel Fenn
- Department of Neuroscience, Ohio State University, Columbus, Ohio, 43210.,Medical Scientist Training Program, Ohio State University, Columbus, Ohio, 43210
| | - Paula C Monsma
- Department of Neuroscience, Ohio State University, Columbus, Ohio, 43210
| | - Anthony Brown
- Department of Neuroscience, Ohio State University, Columbus, Ohio, 43210
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Lee S, Eyer J, Letournel F, Boumil E, Hall G, Shea TB. Neurofilaments form flexible bundles during neuritogenesis in culture and in mature axons in situ. J Neurosci Res 2019; 97:1306-1318. [PMID: 31304612 DOI: 10.1002/jnr.24482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 05/28/2019] [Accepted: 05/29/2019] [Indexed: 11/07/2022]
Abstract
Neurofilaments (NFs) undergo cation-dependent phospho-mediated associations with each other and other cytoskeletal elements that support axonal outgrowth. Progressive NF-NF associations generate a resident, bundled population that undergoes exchange with transporting NFs. We examined the properties of bundled NFs. Bundles did not always display a fully linear profile but curved and twisted at various points along the neurite length. Bundles retracted faster than neurites and retracted bundles did not expand following extraction with Triton, indicating that they coiled passively rather than due to pressure from the cell. Bundles consisted of helically wound NFs, which may provide flexibility necessary for turning of growing axons during pathfinding. Interactions between NFs and other cytoskeletal elements may be disrupted en masse during neurite retraction or regionally during remodeling. It is suggested that bundles within long axons that cannot be fully retracted into the soma could provide maintain proximal support yet still allow more distal flexibility for remodeling and changing direction during pathfinding.
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Affiliation(s)
- Sangmook Lee
- Laboratory for Neuroscience, Department of Biology Science, UMass Lowell, Lowell, Massachusetts
| | - Joel Eyer
- Institut de Biologie en Santé PBH-IRIS, Universitaire d'Angers, Angers, France
| | | | - Edward Boumil
- Center for Vision Research, SUNY Upstate, Syracuse, New York
| | - Garth Hall
- Laboratory for Neuroscience, Department of Biology Science, UMass Lowell, Lowell, Massachusetts
| | - Thomas B Shea
- Laboratory for Neuroscience, Department of Biology Science, UMass Lowell, Lowell, Massachusetts
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Fenn JD, Johnson CM, Peng J, Jung P, Brown A. Kymograph analysis with high temporal resolution reveals new features of neurofilament transport kinetics. Cytoskeleton (Hoboken) 2017; 75:22-41. [PMID: 28926211 DOI: 10.1002/cm.21411] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 09/08/2017] [Indexed: 12/30/2022]
Abstract
We have used kymograph analysis combined with edge detection and an automated computational algorithm to analyze the axonal transport kinetics of neurofilament polymers in cultured neurons at 30 ms temporal resolution. We generated 301 kymographs from 136 movies and analyzed 726 filaments ranging from 0.6 to 42 µm in length, representing ∼37,000 distinct moving and pausing events. We found that the movement is even more intermittent than previously reported and that the filaments undergo frequent, often transient, reversals which suggest that they can engage simultaneously with both anterograde and retrograde motors. Average anterograde and retrograde bout velocities (0.9 and 1.2 µm s-1 , respectively) were faster than previously reported, with maximum sustained bout velocities of up to 6.6 and 7.8 µm s-1 , respectively. Average run lengths (∼1.1 µm) and run times (∼1.4 s) were in the range reported for molecular motor processivity in vitro, suggesting that the runs could represent the individual processive bouts of the neurofilament motors. Notably, we found no decrease in run velocity, run length or run time with increasing filament length, which suggests that either the drag on the moving filaments is negligible or that longer filaments recruit more motors.
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Affiliation(s)
- J Daniel Fenn
- Department of Neuroscience and Medical Scientist Training Program, Ohio State University, Columbus, Ohio 43210
| | - Christopher M Johnson
- Quantitative Biology Institute and Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701
| | - Juan Peng
- Center for Biostatistics and Department of Biomedical Informatics, Ohio State University, Columbus, Ohio 43210
| | - Peter Jung
- Quantitative Biology Institute and Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701
| | - Anthony Brown
- Department of Neuroscience and Medical Scientist Training Program, Ohio State University, Columbus, Ohio 43210
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Uchida A, Monsma PC, Fenn JD, Brown A. Live-cell imaging of neurofilament transport in cultured neurons. Methods Cell Biol 2015; 131:21-90. [PMID: 26794508 DOI: 10.1016/bs.mcb.2015.07.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
Neurofilaments, which are the intermediate filaments of nerve cells, are space-filling cytoskeletal polymers that contribute to the growth of axonal caliber. In addition to their structural role, neurofilaments are cargos of axonal transport that move along microtubule tracks in a rapid, intermittent, and bidirectional manner. Though they measure just 10nm in diameter, which is well below the diffraction limit of optical microscopes, these polymers can reach 100 μm or more in length and are often packed densely, just tens of nanometers apart. These properties of neurofilaments present unique challenges for studies on their movement. In this article, we describe several live-cell fluorescence imaging strategies that we have developed to image neurofilament transport in axons of cultured neurons on short and long timescales. Together, these methods form a powerful set of complementary tools with which to study the axonal transport of these unique intracellular cargos.
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Affiliation(s)
- Atsuko Uchida
- Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| | - Paula C Monsma
- Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| | - J Daniel Fenn
- Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| | - Anthony Brown
- Department of Neuroscience, The Ohio State University, Columbus, OH, USA
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Laser-Azogui A, Kornreich M, Malka-Gibor E, Beck R. Neurofilament assembly and function during neuronal development. Curr Opin Cell Biol 2015; 32:92-101. [PMID: 25635910 DOI: 10.1016/j.ceb.2015.01.003] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 01/06/2015] [Accepted: 01/09/2015] [Indexed: 02/06/2023]
Abstract
Studies on the assembly of neuronal intermediate filaments (IFs) date back to the early work of Alzheimer. Developing neurons express a series of IF proteins, sequentially, at distinct stages of mammalian cell differentiation. This correlates with altered morphologies during the neuronal development, including axon outgrowth, guidance and conductivity. Importantly, neuronal IFs that fail to properly assemble into a filamentous network are a hallmark of neurodegenerative diseases such as amyotrophic lateral sclerosis, Alzheimer's, and Parkinson's disease. Traditional structural methodologies fail to fully describe neuronal IF assembly, interactions and resulting function due to IFs structural plasticity, particularly in their C-terminal domains. We review here current progress in the field of neuronal-specific IFs, a dominant component affecting the cytoskeletal structure and function of neurons.
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Affiliation(s)
- Adi Laser-Azogui
- The Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Micha Kornreich
- The Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Eti Malka-Gibor
- Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Roy Beck
- The Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel.
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Abstract
The advent of photoactivatable tools has revolutionized imaging of dynamic cellular processes. One such application is to visualize axonal transport-an intricate and dynamic process by which proteins and other macromolecules are conveyed from their sites of synthesis in the cell bodies to their destinations within axons and synapses. High-quality dynamic imaging of axonal transport using photoactivatable vectors can now be routinely performed using epifluorescence microscopes and CCD cameras that are standard in most laboratories, yet this is largely underutilized. Here we describe detailed protocols for imaging cargoes moving in fast and slow axonal transport in axons of cultured hippocampal neurons.
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Affiliation(s)
- Archan Ganguly
- Department of Pathology, University of California, San Diego, 9500 Gilman Drive, BSB 1029, MC0612, La Jolla, CA, 92093, USA,
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