This work was supported by grants from the Israel Science foundation (ISF, 561/11) and the European Research Council (ERC, 309377).

<ol>
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N., Greensmith, L., Schiavo, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+imaging+of+axonal+transport+in+murine+motor+and+sensory+neurons.">In vivo imaging of axonal transport in murine motor and sensory neurons.</a> Journal of Neuroscience Methods. 257, 26-33 (2016).</li><li>Mandal, A., Drerup, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Axonal+Transport+and+Mitochondrial+Function+in+Neurons.">Axonal Transport and Mitochondrial Function in Neurons.</a> Frontiers in Cellular Neuroscience. 13, 373 (2019).</li><li>Magran&#233;, J., Cortez, C., Gan, W. B., Manfredi, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abnormal+mitochondrial+transport+and+morphology+are+common+pathological+denominators+in+SOD1+and+TDP43+ALS+mouse+models.">Abnormal mitochondrial transport and morphology are common pathological denominators in SOD1 and TDP43 ALS mouse models.</a> Human Molecular Genetics. 23, 1413-1424 (2014).</li><li>Anderson, R. G. W., Orci, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+view+of+acidic+intracellular+compartments.">A view of acidic intracellular compartments.</a> Journal of Cell Biology. 106, 539-543 (1988).</li><li>Kiral, F. R., Kohrs, F. E., Jin, E. J., Hiesinger, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rab+GTPases+and+Membrane+Trafficking+in+Neurodegeneration.">Rab GTPases and Membrane Trafficking in Neurodegeneration.</a> Current Biology. 28, R471-R486 (2018).</li><li>Ya-Cheng Liao, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+Granules+Hitchhike+on+Lysosomes+for+Long-Distance+Transport,+Using+Annexin+A11+as+a+Molecular+Tether.">RNA Granules Hitchhike on Lysosomes for Long-Distance Transport, Using Annexin A11 as a Molecular Tether.</a> Cell. 179, 147-164 (2019).</li><li>Gluska, S., Chein, M., Rotem, N., Ionescu, A., Perlson, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracking+Quantum-Dot+labeled+neurotropic+factors+transport+along+primary+neuronal+axons+in+compartmental+microfluidic+chambers.">Tracking Quantum-Dot labeled neurotropic factors transport along primary neuronal axons in compartmental microfluidic chambers.</a> Methods in Cell Biology. 131, 365-387 (2016).</li><li>Gershoni-Emek, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localization+of+RNAi+Machinery+to+Axonal+Branch+Points+and+Growth+Cones+Is+Facilitated+by+Mitochondria+and+Is+Disrupted+in+ALS.">Localization of RNAi Machinery to Axonal Branch Points and Growth Cones Is Facilitated by Mitochondria and Is Disrupted in ALS.</a> Frontiers in Molecular Neuroscience. 11, 311 (2018).</li><li>Neto, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compartmentalized+Microfluidic+Platforms:+The+Unrivaled+Breakthrough+of+In+Vitro+Tools+for+Neurobiological+Research.">Compartmentalized Microfluidic Platforms: The Unrivaled Breakthrough of In Vitro Tools for Neurobiological Research.</a> Journal of Neuroscience. 36 (46), 11573-11584 (2016).</li><li>Ionescu, A., Zahavi, E. E., Gradus, T., Ben-Yaakov, K., Perlson, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compartmental+microfluidic+system+for+studying+muscle-neuron+communication+and+neuromuscular+junction+maintenance.">Compartmental microfluidic system for studying muscle-neuron communication and neuromuscular junction maintenance.</a> European Journal of Cell Biology. 95, 69-88 (2016).</li><li>Zahavi, E. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+compartmentalized+microfluidic+neuromuscular+co-culture+system+reveals+spatial+aspects+of+GDNF+functions.">A compartmentalized microfluidic neuromuscular co-culture system reveals spatial aspects of GDNF functions.</a> Journal of Cell Science. 128, 1241-1252 (2015).</li><li>Altman, T., Geller, D., Kleeblatt, E., Gradus-Perry, T., Perlson, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+in+vitro+compartmental+system+underlines+the+contribution+of+mitochondrial+immobility+to+the+ATP+supply+in+the+NMJ.">An in vitro compartmental system underlines the contribution of mitochondrial immobility to the ATP supply in the NMJ.</a> Journal of Cell Science. 132 (23), (2019).</li><li>Schaller, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+combinatorial+screening+identifies+neurotrophic+factors+for+selective+classes+of+motor+neurons.">Novel combinatorial screening identifies neurotrophic factors for selective classes of motor neurons.</a> Proceedings of the National Academy of Sciences USA. 114, E2486-E2493 (2017).</li><li>Ionescu, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+the+Sigma-1+Receptor+via+Pridopidine+Ameliorates+Central+Features+of+ALS+Pathology+in+a+SOD1G93A+Model.">Targeting the Sigma-1 Receptor via Pridopidine Ameliorates Central Features of ALS Pathology in a SOD1G93A Model.</a> Cell Death &amp; Disease. 10 (3), 210 (2019).</li><li>Zahavi, E. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+compartmentalized+microfluidic+neuromuscular+coculture+system+reveals+spatial+aspects+of+GDNF+functions.">A compartmentalized microfluidic neuromuscular coculture system reveals spatial aspects of GDNF functions.</a> Journal of Cell Science. 128, 1241-1252 (2015).</li><li>Maimon, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mir126-5p+downregulation+facilitates+axon+degeneration+and+nmj+disruption+via+a+non-cell-autonomous+mechanism+in+ALS.">Mir126-5p downregulation facilitates axon degeneration and nmj disruption via a non-cell-autonomous mechanism in ALS.</a> Journal of Neuroscience. 38, 5478-5494 (2018).</li></ol>

The authors declare no conflict of interest.

In this protocol, we describe a system to track axonal transport of mitochondria and acidic compartments in motor neurons. This simplified in vitro platform allows precise control, monitoring, and manipulation of subcellular neuronal compartments, enabling experimental analysis of motor neuron local functions. This protocol can be useful for studying MN diseases such as ALS, to focus on understanding the underlying mechanism of axonal transport dysfunction in the disease10,<sup class="x...

MNs are highly polarized cells with long axons, reaching up to one meter long in adult humans. This phenomenon creates a critical challenge for the maintenance of MN connectivity and function. Consequently, MNs depend on proper transport of information, organelles, and materials along the axons from their cell body to the synapse and back. Various cellular components, such as proteins, RNA, and organelles are shuttled regularly through the axons. Mitochondria are important organelles that are routinely transported in MNs. Mitochondria are essential for proper activity and function of MNs, responsible for ATP provision, calcium buffering, and signaling processes1,2. The axonal transport of mitochondria is a well-studied process3,4. Interestingly, defects in mitochondrial transport were reported to be involved in several neurodegenerative diseases and specifically in MN diseases5. Acidic compartments serve as another example for intrinsic organelles that move along MN axons. Acidic compartments include lysosomes, endosomes, trans-Golgi apparatus, and certain secretory vesicles6. Defects in the axonal transport of acidic compartments were found in several neurodegenerative diseases as well7, and recent papers highlight their importance in MN diseases8.
To efficiently study axonal transport, microfluidic chambers that separate somatic and axonal compartments are frequently used9,10. The two significant advantages of the microfluidic system, and the compartmentalization and the isolation of axons, render it ideal for the study of subcellular processes11. The spatial separation between the neuronal cell bodies and axons can be used to manipulate the extracellular environments of different neuronal compartments (e.g., axons vs. soma). Biochemical, neuronal growth/degeneration, and immunofluorescence assays all benefit from this platform. MFCs can also assist in studying cell-to-cell communication by coculturing neurons with other cell types, such as skeletal muscles12,13,14.
Here, we describe a simple yet precise protocol for monitoring mitochondria and acidic compartment transport in motor neurons. We further show the use of this method by comparing the relative percentage of retrograde and anterograde moving organelles, as well as the distribution of transport velocity.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>35mm Fluodish &#8211; glass bottom dish</td>
			<td>World Precision Instruments WPI</td>
			<td>FD35-100</td>
			<td></td>
		</tr>
		<tr>
			<td>50mm Fluodish &#8211; glass bottom dish</td>
			<td>World Precision Instruments WPI</td>
			<td>FD5040-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Andor iXon DU-897 EMCCD camera</td>
			<td>Andor</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ARA-C (Cytosine &#946;-D-arabinofuranoside)</td>
			<td>Sigma-Aldrich</td>
			<td>C1768</td>
			<td>stock of 2mM in filtered DDW</td>
		</tr>
		<tr>
			<td>B-27 Supplement (50X)</td>
			<td>Thermo Fisher</td>
			<td>17504044</td>
			<td></td>
		</tr>
		<tr>
			<td>BDNF</td>
			<td>Alomone Labs</td>
			<td>B-250</td>
			<td>Dilute to 10 &#181;g/mL in filtered ddw with 0.01% BSA)</td>
		</tr>
		<tr>
			<td>Biopsy punch 1.25mm</td>
			<td>World Precision Instruments WPI</td>
			<td>504530</td>
			<td>For preperation of large MFC</td>
		</tr>
		<tr>
			<td>Biopsy punch 6mm</td>
			<td>World Precision Instruments WPI</td>
			<td>504533</td>
			<td>For preperation of small MFC</td>
		</tr>
		<tr>
			<td>Biopsy punch 7mm</td>
			<td>World Precision Instruments WPI</td>
			<td>504534</td>
			<td>For preperation of large MFC</td>
		</tr>
		<tr>
			<td>Bitplane Imaris software - version 8.4.1</td>
			<td>Imaris</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumine (BSA)</td>
			<td>Sigma-Aldrich</td>
			<td>#A3311-100G</td>
			<td>5% w/v in ddw</td>
		</tr>
		<tr>
			<td>Chlorotrimetylsilane</td>
			<td>Sigma-Aldrich</td>
			<td>#386529-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>CNTF</td>
			<td>Alomone Labs</td>
			<td>C-240</td>
			<td>Dilute to 10 &#181;g/mL in filtered ddw with 0.01% BSA)</td>
		</tr>
		<tr>
			<td>Density Gradient Medium - Optiprep</td>
			<td>Sigma-Aldrich</td>
			<td>D1556</td>
			<td></td>
		</tr>
		<tr>
			<td>Deoxyribonuclease I (DNAse) from bovine pancreas</td>
			<td>Sigma-Aldrich</td>
			<td>DN-25</td>
			<td>stock 10mg/mL in neurobasal</td>
		</tr>
		<tr>
			<td>Dow Corning High-vacuum silicone grease</td>
			<td>Sigma-Aldrich</td>
			<td>Z273554-1EA</td>
			<td>For epoxy mold preperation</td>
		</tr>
		<tr>
			<td>DPBS 10X</td>
			<td>Thermo Fisher</td>
			<td>#14200-067</td>
			<td>dilute 1:10 in ddw</td>
		</tr>
		<tr>
			<td>Dumont fine forceps #55 0.05 &#215; 0.02 mm</td>
			<td>F.S.T</td>
			<td>1125520</td>
			<td></td>
		</tr>
		<tr>
			<td>Epoxy Hardener</td>
			<td>Trias Chem S.R.L</td>
			<td>IPE 743</td>
			<td>For epoxy mold preperation</td>
		</tr>
		<tr>
			<td>Epoxy Resin</td>
			<td>Trias Chem S.R.L</td>
			<td>RP 026UV</td>
			<td>For epoxy mold preperation</td>
		</tr>
		<tr>
			<td>FIJI software</td>
			<td>ImageJ</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>GDNF</td>
			<td>Alomone Labs</td>
			<td>G-240</td>
			<td>Dilute to 10 &#181;g/mL in filtered ddw with 0.01% BSA)</td>
		</tr>
		<tr>
			<td>Glutamax 100X</td>
			<td>Thermo Fisher</td>
			<td>#35050-038</td>
			<td></td>
		</tr>
		<tr>
			<td>HB9:GFP mice strain</td>
			<td>Jackson Laboratories</td>
			<td>005029</td>
			<td></td>
		</tr>
		<tr>
			<td>HBSS 10X</td>
			<td>Thermo Fisher</td>
			<td>#14185-045</td>
			<td>Dilute 1:10 in ddw with addition of 1% P/S and filter</td>
		</tr>
		<tr>
			<td>iQ software</td>
			<td>Andor</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Iris scissors, curved, 10 cm</td>
			<td>AS Medizintechnik</td>
			<td>11-441-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Iris scissors, straight, 9 cm</td>
			<td>AS Medizintechnik</td>
			<td>11-440-09</td>
			<td></td>
		</tr>
		<tr>
			<td>Laminin</td>
			<td>Sigma-Aldrich</td>
			<td>#L-2020</td>
			<td></td>
		</tr>
		<tr>
			<td>Leibovitz&#39;s L-15 Medium</td>
			<td>Thermo Fisher</td>
			<td>11415064</td>
			<td></td>
		</tr>
		<tr>
			<td>LysoTracker Red</td>
			<td>Thermo Fisher</td>
			<td>L7528</td>
			<td></td>
		</tr>
		<tr>
			<td>Mitotracker Deep-Red FM</td>
			<td>Thermo Fisher</td>
			<td>M22426</td>
			<td></td>
		</tr>
		<tr>
			<td>Neurobasal medium</td>
			<td>Thermo Fisher</td>
			<td>21103049</td>
			<td></td>
		</tr>
		<tr>
			<td>Nikon Eclipse Ti micorscope</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin (P/S) Solution</td>
			<td>Biological Industries</td>
			<td>03-031-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-L-Ornithin (PLO)</td>
			<td>Sigma-Aldrich</td>
			<td>#P8638</td>
			<td>Dilute 1:1000 in flitered 1X PBS</td>
		</tr>
		<tr>
			<td>Sylgard 184 silicone elastomer kit</td>
			<td>DOW Corning Corporation</td>
			<td>#3097358-1004</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin from bovine pancreas</td>
			<td>Sigma-Aldrich</td>
			<td>T1426</td>
			<td>stock 25 mg/mL in 1XPBS</td>
		</tr>
		<tr>
			<td>Vannas spring microdissection scissors, 3 mm blade</td>
			<td>F.S.T</td>
			<td>15000-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Yokogawa CSU X-1</td>
			<td>Yokogawa</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

axonal transport of organelles in motor neuron cultures using microfluidic chambers system

Motor neurons (MNs) are highly polarized cells with very long axons. Axonal transport is a crucial mechanism for MN health, contributing to neuronal growth, development, and survival. We describe a detailed method for the use of microfluidic chambers (MFCs) for tracking axonal transport of fluorescently labeled organelles in MN axons. This method is rapid, relatively inexpensive, and allows for the monitoring of intracellular cues in space and time. We describe a step by step protocol for: 1) Fabrication of polydimethylsiloxane (PDMS) MFCs; 2) Plating of ventral spinal cord explants and MN dissociated culture in MFCs; 3) Labeling of mitochondria and acidic compartments followed by live confocal imagining; 4) Manual and semiautomated axonal transport analysis. Lastly, we demonstrate a difference in the transport of mitochondria and acidic compartments of HB9::GFP ventral spinal cord explant axons as a proof of the system validity. Altogether, this protocol provides an efficient tool for studying the axonal transport of various axonal components, as well as a simplified manual for MFC usage to help discover spatial experimental possibilities.

Following the described protocol, mouse embryonic HB9::GFP spinal cord explants were cultured in MFC (Figure 4A). Explants were grown for 7 days, when axons fully crossed into the distal compartment. Mitotracker Deep Red and Lysotracker Red dyes were added to the distal and proximal compartments in order to label the mitochondria and acidic compartments (Figure 4C). Axons in the distal grooves we...

Watch this Scientific Journal Video about Axonal Transport of Organelles in Motor Neuron Cultures using Microfluidic Chambers System at JoVE.com

Axonal Transport of Organelles in Motor Neuron Cultures using Microfluidic Chambers System

Axonal transport is a crucial mechanism for motor neuron health. In this protocol we provide a detailed method for tracking the axonal transport of acidic compartments and mitochondria in motor neuron axons using microfluidic chambers.

Motor neurons (MNs) are highly polarized cells with very long axons. Axonal transport is a crucial mechanism for MN health, contributing to neuronal ...

axonal-transport-organelles-motor-neuron-cultures-using-microfluidic

Research

JoVE Journal

Neuroscience

9.9K Views.  Tel Aviv University. Axonal transport is a crucial mechanism for motor neuron health. In this protocol we provide a detailed method for tracking the axonal transport of acidic compartments and mitochondria in motor neuron axons using microfluidic chambers.

Video: Axonal Transport of Organelles in Motor Neuron Cultures using Microfluidic Chambers System

Paired Patch Clamp Recordings from Motor-neuron and Target Skeletal Muscle in Zebrafish

Larval zebrafish represent the first vertebrate model system to allow simultaneous patch clamp recording from a spinal motor-neuron and target muscle. This is a direct consequence of the accessibility to both cell types and ability to visually distinguish the single segmental CaP motor-neuron on the basis of morphology and location. This video demonstrates the microscopic methods used to identify a CaP motor-neuron and target muscle cells as well as the methodologies for recording from each cell type. Identification of the CaP motor-neuron type is confirmed by either dye filling or by the biophysical features such as action potential waveform and cell input resistance. Motor-neuron recordings routinely last for one hour permitting long-term recordings from multiple different target muscle cells. Control over the motor-neuron firing pattern enables measurements of the frequency-dependence of synaptic transmission at the neuromuscular junction. Owing to a large quantal size and the low noise provided by whole cell voltage clamp, all of the unitary events can be resolved in muscle. This feature permits study of basic synaptic properties such as release properties, vesicle recycling, as well as synaptic depression and facilitation. The advantages offered by this in vivo preparation eclipse previous neuromuscular model systems studied wherein the motor-neurons are usually stimulated by extracellular electrodes and the muscles are too large for whole cell patch clamp. The zebrafish preparation is amenable to combining electrophysiological analysis with a wide range of approaches including transgenic lines, morpholino knockdown, pharmacological intervention and in vivo imaging. These approaches, coupled with the growing number of neuromuscular disease models provided by mutant lines of zebrafish, open the door for new understanding of human neuromuscular disorders.

Larval zebrafish represent the first vertebrate model system to allow simultaneous patch clamp recording from a spinal motor-neuron and target skeletal muscle. This video demonstrates the microscopic methods used to identify a segmental CaP motor-neuron and target muscle cells as well as the methodologies for recording from each cell type.

Larval zebrafish represent the first vertebrate model system to allow simultaneous patch clamp recording from a spinal motor-neuron and target muscle.  ...

Derivation of Enriched Oligodendrocyte Cultures and Oligodendrocyte/Neuron Myelinating Co-cultures from Post-natal Murine Tissues

Identifying the molecular mechanisms underlying OL development is not only critical to furthering our knowledge of OL biology, but also has implications for understanding the pathogenesis of demyelinating diseases such as Multiple Sclerosis (MS). Cellular development is commonly studied with primary cell culture models. Primary cell culture facilitates the evaluation of a given cell type by providing a controlled environment, free of the extraneous variables that are present in vivo. While OL cultures derived from rats have provided a vast amount of insight into OL biology, similar efforts at establishing OL cultures from mice has been met with major obstacles. Developing methods to culture murine primary OLs is imperative in order to take advantage of the available transgenic mouse lines. 
Multiple methods for extraction of OPCs from rodent tissue have been described, ranging from neurosphere derivation, differential adhesion purification and immunopurification 1-3. While many methods offer success, most require extensive culture times and/or costly equipment/reagents. To circumvent this, purifying OPCs from murine tissue with an adaptation of the method originally described by McCarthy &amp; 
de Vellis 2 is preferred. This method involves physically separating OPCs from a mixed glial culture derived from neonatal rodent cortices. The result is a purified OPC population that can be differentiated into an OL-enriched culture. This approach is appealing due to its relatively short culture time and the unnecessary requirement for growth factors or immunopanning antibodies. 
While exploring the mechanisms of OL development in a purified culture is informative, it does not provide the most physiologically relevant environment for assessing myelin sheath formation. Co-culturing OLs with neurons would lend insight into the molecular underpinnings regulating OL-mediated myelination of axons. For many OL/neuron co-culture studies, dorsal root ganglion neurons (DRGNs) have proven to be the neuron type of choice. They are ideal for co-culture with OLs due to their ease of extraction, minimal amount of contaminating cells, and formation of dense neurite beds. While studies using rat/mouse myelinating xenocultures have been published 4-6, a method for the derivation of such OL/DRGN myelinating co-cultures from post-natal murine tissue has not been described. Here we present detailed methods on how to effectively produce such cultures, along with examples of expected results. These methods are useful for addressing questions relevant to OL development/myelinating function, and are useful tools in the field of neuroscience.

This article describes methods to derive enriched populations of murine oligodendrocyte precursor cells (OPCs) in primary culture, which differentiate to produce mature oligodendrocytes (OLs). In addition, this report describes techniques to produce murine myelinating co-cultures by seeding mouse OPCs onto a neurite bed of mouse dorsal root ganglion neurons (DRGNs).

Identifying the molecular mechanisms underlying OL development is not only critical to furthering our knowledge of OL biology, but also has implications ...

Imaging Analysis of Neuron to Glia Interaction in Microfluidic Culture Platform (MCP)-based Neuronal Axon and Glia Co-culture System

Proper neuron to glia interaction is critical to physiological function of the central nervous system (CNS). This bidirectional communication is sophisticatedly mediated by specific signaling pathways between neuron and glia1,2 . Identification and characterization of these signaling pathways is essential to the understanding of how neuron to glia interaction shapes CNS physiology. Previously, neuron and glia mixed cultures have been widely utilized for testing and characterizing signaling pathways between neuron and glia. What we have learned from these preparations and other in vivo tools, however, has suggested that mutual signaling between neuron and glia often occurred in specific compartments within neurons (i.e., axon, dendrite, or soma)3. This makes it important to develop a new culture system that allows separation of neuronal compartments and specifically examines the interaction between glia and neuronal axons/dendrites. In addition, the conventional mixed culture system is not capable of differentiating the soluble factors and direct membrane contact signals between neuron and glia. Furthermore, the large quantity of neurons and glial cells in the conventional co-culture system lacks the resolution necessary to observe the interaction between a single axon and a glial cell.
	In this study, we describe a novel axon and glia co-culture system with the use of a microfluidic culture platform (MCP). In this co-culture system, neurons and glial cells are cultured in two separate chambers that are connected through multiple central channels. In this microfluidic culture platform, only neuronal processes (especially axons) can enter the glial side through the central channels. In combination with powerful fluorescent protein labeling, this system allows direct examination of signaling pathways between axonal/dendritic and glial interactions, such as axon-mediated transcriptional regulation in glia, glia-mediated receptor trafficking in neuronal terminals, and glia-mediated axon growth. The narrow diameter of the chamber also significantly prohibits the flow of the neuron-enriched medium into the glial chamber, facilitating probing of the direct membrane-protein interaction between axons/dendrites and glial surfaces.

Imaging Analysis of Neuron to Glia Interaction in Microfluidic Culture Platform MCP-based Neuronal Axon and Glia Co-culture System

This study describes the procedures of setting up a novel neuronal axon and (astro)glia co-culture platform. In this co-culture system, manipulation of direct interaction between a single axon (and single glial cell) becomes feasible, allowing mechanistic analysis of the mutual neuron to glial signaling.

Proper  neuron to glia interaction is critical to physiological function of the central  nervous system (CNS). This bidirectional communication is ...

Real-time Imaging of Axonal Transport of Quantum Dot-labeled BDNF in Primary Neurons

BDNF plays an important role in several facets of neuronal survival, differentiation, and function. Structural and functional deficits in axons are increasingly viewed as an early feature of neurodegenerative diseases, including Alzheimer&#8217;s disease (AD) and Huntington&#8217;s disease (HD). As yet unclear is the mechanism(s) by which axonal injury is induced. We reported the development of a novel technique to produce biologically active, monobiotinylated BDNF (mBtBDNF) that can be used to trace axonal transport of BDNF. Quantum dot-labeled BDNF (QD-BDNF) was produced by conjugating quantum dot 655 to mBtBDNF. A microfluidic device was used to isolate axons from neuron cell bodies. Addition of QD-BDNF to the axonal compartment allowed live imaging of BDNF transport in axons. We demonstrated that QD-BDNF moved essentially exclusively retrogradely, with very few pauses, at a moving velocity of around 1.06 &#956;m/sec. This system can be used to investigate mechanisms of disrupted axonal function in AD or HD, as well as other degenerative disorders.

Axonal transport of BDNF, a neurotrophic factor, is critical for the survival and function of several neuronal populations. Some degenerative disorders are marked by disruption of axonal structure and function. We demonstrated the techniques used to examine live trafficking of QD-BDNF in microfluidic chambers using primary neurons.

BDNF plays an important role in several facets of neuronal survival, differentiation, and function. Structural and functional deficits in axons are ...

The Neuromuscular Junction: Measuring Synapse Size, Fragmentation and Changes in Synaptic Protein Density Using Confocal Fluorescence Microscopy

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. Structural changes at the NMJ can result in neurotransmission failure, resulting in weakness, atrophy and even death of the muscle fiber. Many studies have investigated how genetic modifications or disease can alter the structure of the mouse NMJ. Unfortunately, it can be difficult to directly compare findings from these studies because they often employed different parameters and analytical methods. Three protocols are described here. The first uses maximum intensity projection confocal images to measure the area of acetylcholine receptor (AChR)-rich postsynaptic membrane domains at the endplate and the area of synaptic vesicle staining in the overlying presynaptic nerve terminal. The second protocol compares the relative intensities of immunostaining for synaptic proteins in the postsynaptic membrane. The third protocol uses Fluorescence Resonance Energy Transfer (FRET) to detect changes in the packing of postsynaptic AChRs at the endplate. The protocols have been developed and refined over a series of studies. Factors that influence the quality and consistency of results are discussed and normative data are provided for NMJs in healthy young adult mice.

The neuromuscular junction (NMJ) is altered in a variety of conditions that can sometimes culminate in synaptic failure. This report describes fluorescence microscope-based methods to quantify such structural changes.

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. ...

Assay to Measure Nucleocytoplasmic Transport in Real Time within Motor Neuron-like NSC-34 Cells

Nucleocytoplasmic transport refers to the import and export of large molecules from the cell nucleus. Recently, a number of studies have shown a connection between amyotrophic lateral sclerosis (ALS) and impairments in the nucleocytoplasmic pathway. ALS is a neurodegenerative disease affecting the motor neurons and resulting in paralysis and ultimately in death, within 2-5 years on average. Most cases of ALS are sporadic, lacking any apparent genetic linkage, but 10% are inherited in a dominant manner. Recently, hexanucleotide repeat expansions (HREs) in the chromosome 9 open reading frame 72 (C9orf72) gene were identified as a genetic cause of ALS and frontotemporal dementia (FTD). Importantly, different groups have recently proposed that these mutants affect nucleocytoplasmic transport. These studies have mostly shown the final outcome and manifestations caused by HREs on nucleocytoplasmic transport, but they do not demonstrate nuclear transport dysfunction in real time. As a result, only severe nucleocytoplasmic transport deficiency can be determined, mostly due to high overexpression or exogenous protein insertion. 
This protocol describes a new and very sensitive assay to evaluate and quantify nucleocytoplasmic transport dysfunction in real time. The rate of import of a NLS-NES-GFP protein (shuttle-GFP) can be quantified in real time using fluorescent microscopy. This is performed by using an exportin inhibitor, thus allowing the shuttle GFP only to enter the nucleus. To validate the assay, the C9orf72 HRE translated dipeptide repeats, poly(GR) and poly(PR), which have been previously shown to disrupt nucleocytoplasmic transport, were used. Using the described assay, a 50% decrease in the nuclear import rate was observed compared to the control. Using this system, minute changes in nucleocytoplasmic transport can be examined and the ability of different factors to rescue (even partially) a nucleocytoplasmic transport defect can be determined.

This protocol describes a method to sensitively measure the nucleocytoplasmic transport rate within motor neuron-like NSC-34 cells by quantifying the real-time change in the nuclear import of a NLS-NES-GFP protein.

Nucleocytoplasmic transport refers to the import and export of large molecules from the cell nucleus. Recently, a number of studies have shown a ...

Visualization of the Axonal Projection Pattern of Embryonic Motor Neurons in Drosophila

The establishment of functional neuromuscular circuits relies on precise connections between developing motor axons and target muscles. Motor neurons extend growth cones to navigate along specific pathways by responding to a large number of axon guidance cues that emanate from the surrounding extracellular environment. Growth cone target recognition also plays a critical role in neuromuscular specificity. This work presents a standard immunohistochemistry protocol to visualize motor neuron projections of late stage-16 Drosophila melanogaster embryos. This protocol includes a few key steps, including a genotyping procedure, to sort the desired mutant embryos; an immunostaining procedure, to tag embryos with fasciclin II (FasII) antibody; and a dissection procedure, to generate filleted preparations from fixed embryos. Motor axon projections and muscle patterns in the periphery are much better visualized in flat preparations of filleted embryos than in whole-mount embryos. Therefore, the filleted preparation of fixed embryos stained with FasII antibody provides a powerful tool to characterize the genes required for motor axon pathfinding and target recognition, and it can also be applied to both loss-of-function and gain-of-function genetic screens.

Visualization of the Axonal Projection Pattern of Embryonic Motor Neurons in Drosophila

This work details a standard immunohistochemistry method to visualize motor neuron projections of late stage-16 Drosophila melanogaster embryos. The filleted preparation of fixed embryos stained with FasII antibody provides a powerful tool to characterize the genes required for motor axon pathfinding and target recognition during neural development.

The establishment of functional neuromuscular circuits relies on precise connections between developing motor axons and target muscles. Motor neurons ...

Visualizing and Analyzing Intracellular Transport of Organelles and Other Cargos in Astrocytes

Astrocytes are among the most abundant cell types in the adult brain, where they play key roles in a multiplicity of functions. As a central player in brain homeostasis, astrocytes supply neurons with vital metabolites and buffer extracellular water, ions, and glutamate. An integral component of the &#8220;tri-partite&#8221; synapse, astrocytes are also critical in the formation, pruning, maintenance, and modulation of synapses. To enable these highly interactive functions, astrocytes communicate among themselves and with other glial cells, neurons, the brain vasculature, and the extracellular environment through a multitude of specialized membrane proteins that include cell adhesion molecules, aquaporins, ion channels, neurotransmitter transporters, and gap junction molecules. To support this dynamic flux, astrocytes, like neurons, rely on tightly coordinated and efficient intracellular transport. Unlike neurons,&#160;where intracellular trafficking has been extensively delineated, microtubule-based transport in astrocytes has been less studied. Nonetheless, exo- and endocytic trafficking of cell membrane proteins and intracellular organelle transport orchestrates astrocytes&#8217; normal biology, and these processes are often affected in disease or in response to injury. Here we present a straightforward protocol to culture high quality murine astrocytes, to fluorescently label astrocytic proteins and organelles of interest, and to record their intracellular transport dynamics using time-lapse confocal microscopy. We also demonstrate how to extract and quantify relevant transport parameters from the acquired movies using available image analysis software (i.e., ImageJ/FIJI) plugins.

Here we describe an in vitro live-imaging method to visualize intracellular transport of organelles and trafficking of plasma membrane proteins in murine astrocytes. This protocol also presents an image analysis methodology to determine cargo transport itineraries and kinetics.

Astrocytes are among the most abundant cell types in the adult brain, where they play key roles in a multiplicity of functions. As a central player in ...

Evaluation of Motor Impairment in C. elegans Models of Amyotrophic Lateral Sclerosis

The neurodegenerative disease amyotrophic lateral sclerosis (ALS) features progressive loss of motor neurons accompanied by muscle weakness and motor impairment that worsens with time. While considerable advances have been made in determining genetic drivers of ALS for a subset of patients, the majority of cases have an unknown etiology. Further, the mechanisms underlying motor neuron dysfunction and degeneration are not well understood; therefore, there is an ongoing need to develop and characterize representative models to study these processes. Caenorhabditis elegans can adapt their movement to the physical constraints of their surroundings, with two primary movement paradigms studied in a laboratory environment- crawling on a solid surface and swimming in liquid. These represent a complex interplay between sensation, motor neurons, and muscles. C. elegans models of ALS can exhibit impairment in one or both of these movement paradigms. This protocol describes two sensitive assays for evaluating motility in C. elegans: an optimized radial locomotion assay measuring crawling on a solid surface and an automated method for tracking and analyzing swimming in liquid (thrashing). In addition to the characterization of baseline motor impairment of ALS models, these assays can detect suppression or enhancement of the phenotypes from genetic or small molecule interventions. Thus, these methods have utility for studying ALS&#160;models and any C. elegans strain that exhibits altered motility.

Evaluation of Motor Impairment in C. elegans Models of Amyotrophic Lateral Sclerosis

This protocol describes two sensitive assays for discriminating among mild, moderate, and severe motor impairment in C. elegans models of amyotrophic lateral sclerosis, with general utility for C. elegans strains, with altered motility.

The neurodegenerative disease amyotrophic lateral sclerosis (ALS) features progressive loss of motor neurons accompanied by muscle weakness and motor ...

Generation of Human Motor Units with Functional Neuromuscular Junctions in Microfluidic Devices

Neuromuscular junctions (NMJs) are specialized synapses between the axon of the lower motor neuron and the muscle facilitating the engagement of muscle contraction. In motor neuron disorders, such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA), NMJs degenerate, resulting in muscle atrophy and progressive paralysis. The underlying mechanism of NMJ degeneration is unknown, largely due to the lack of translatable research models. This study aimed to create a versatile and reproducible in vitro model of a human motor unit with functional NMJs. Therefore, human induced pluripotent stem cell (hiPSC)-derived motor neurons and human primary mesoangioblast (MAB)-derived myotubes were co-cultured in commercially available microfluidic devices. The use of fluidically isolated micro-compartments allows for the maintenance of cell-specific microenvironments while permitting cell-to-cell contact through microgrooves. By applying a chemotactic and volumetric gradient, the growth of motor neuron-neurites through the microgrooves promoting myotube interaction and the formation of NMJs were stimulated. These NMJs were identified immunocytochemically through co-localization of motor neuron presynaptic marker synaptophysin (SYP) and postsynaptic acetylcholine receptor (AChR) marker &#945;-bungarotoxin (Btx) on myotubes and characterized morphologically using scanning electron microscopy (SEM). The functionality of the NMJs was confirmed by measuring calcium responses in myotubes upon depolarization of the motor neurons. The motor unit generated using standard microfluidic devices and stem cell technology can aid future research focusing on NMJs in health and disease.

We describe a method to generate human motor units in commercially available microfluidic devices by co-culturing human induced pluripotent stem cell-derived motor neurons with human primary mesoangioblast-derived myotubes resulting in the formation of functionally active neuromuscular junctions.

Neuromuscular junctions (NMJs) are specialized synapses between the axon of the lower motor neuron and the muscle facilitating the engagement of muscle ...