Name: optimizing sample preparation process for transmission electron microscopy of neuromuscular junctions in drosophila larvae
Uploaded: 2023-09-15T14:00:00
Description: Watch this Scientific Journal Video about Optimizing Sample Preparation Process for Transmission Electron Microscopy of Neuromuscular Junctions in Drosophila Larvae at JoVE.com

This work was supported by Natural Science Foundation of China Grant 32070811, and Southeast University (China) Analysis Test Fund 11240090971. We thank the Laboratory of Electron Microscopy and Center of Morphological Analysis, School of Medicine, Southeast University, Nanjing, China.

NOTE: The transmission electron microscopy sample preparation method used in this article has been reported previously16. It is important to note that the selection of reagents and the adjustment of dosage are necessary depending on the sample. There are many toxic chemical reagents used in the sample preparation process, therefore, the operator needs to take certain protective measures, such as wearing protective clothing and gloves and operating in a fume hood.
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D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+larval+NMJ+dissection.">Drosophila larval NMJ dissection.</a> Journal of Visualized Experiments. (24), e1107 (2009).</li><li>Lovri&#263;, J., 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=Multimodal+imaging+of+chemically+fixed+cells+in+preparation+for+NanoSIMS.">Multimodal imaging of chemically fixed cells in preparation for NanoSIMS.</a> Analytical Chemistry. 88 (17), 8841-8848 (2016).</li><li>Woods, P. S., Ledbetter, M. 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Drosophila larva samples tend to curl up during dehydration, as the samples are thin, making it difficult to accurately locate the neuromuscular junction, thereby increasing the difficulty and workload for the sample preparation. The traditional improvement is to shorten the sample7, but the samples were still curled to different degrees.
In our method, there are two critical steps: first, the samples remain flat throughout the dehydration process due to the re...

An erratum was issued for:&#160;<a href="https://www.jove.com/t/64934">Optimizing Sample Preparation Process for Transmission Electron Microscopy of Neuromuscular Junctions in Drosophila Larvae</a>. The Authors section was updated from:
Gan Guangming1,2 
Sheng Qingyuan3 
Ou Yutong1 
Chen Mei1 
Zhang Chenchen1 
1The School of Medicine, Southeast University, 
2The Key Laboratory of Developmental Genes and Human Disease, Southeast University, 
3The School of Life Science and Technology, Southeast University 
Corresponding Authors:&#160;Gan Guangming
to:
Gan Guangming1,2 
Sheng Qingyuan3 
Ou Yutong1 
Chen Mei3 
Zhang Chenchen1 
1The School of Medicine, Southeast University, 
2The Key Laboratory of Developmental Genes and Human Disease, Southeast University, 
3The School of Life Science and Technology, Southeast University 
Corresponding Authors:&#160;Gan Guangming,&#160;Sheng Qingyuan

An erratum was issued for:&#160;<a href="https://www.jove.com/t/64934">Optimizing Sample Preparation Process for Transmission Electron Microscopy of Neuromuscular Junctions in Drosophila Larvae</a>. The Authors section was updated.

Erratum: Optimizing Sample Preparation Process for Transmission Electron Microscopy of Neuromuscular Junctions in Drosophila Larvae

Electron microscopy is one of the most ideal methods for studying the ultrastructure of biological materials that can visually and accurately demonstrate the internal structure of cells at the nanoscale level1. However, due to the complexity of the sample preparation process and the high cost, electron microscopy is not as popular as light microscopy. Recent advancements in electron microscopy techniques have led to significant improvements in image quality, coinciding with a remarkable reduction in the associated workload. Consequently, electron microscopy has assumed an important role in advancing scientific knowledge in diverse fields2.
Drosophila is an excellent animal model for performing genetic manipulations to precisely control the spatial and temporal expression of target genes3. Besides, Drosophila has the advantages of a short growth period and easy rearing compared to mammalian models; therefore, Drosophila is widely used in morphology research4,5.
In Drosophila larvae, neuromuscular junction (NMJ) boutons are widely distributed in the muscles6,7, and immunostaining of NMJ can easily provide information on synapse quantity and morphology8,9 . The NMJ boutons located in the 6th/7th muscles of the A2 and A3 segments are well suited for quantitative and morphological research using light microscopy. This is because of their size and abundance10,11. Therefore, Drosophila larvae NMJs are considered a useful model for neuroscience research12. 
However, it is challenging to observe the NMJ bouton ultrastructure by the TEM. Since the scan window of transmission electron microscopy is narrow, it is hard to position the widely distributed NMJ boutons13. The other reason is that the Drosophila body wall is susceptible to curling during the alcohol dehydration step of the sample preparation protocol7.
Traditional studies have usually chosen boutons between the 6th and 7th muscles of the A2 and A3 segments as sample materials because of their abundance and size14,15. The 6th and 7th muscles of the A2 and A3 segments are bigger than the other muscles and contain more boutons. However, when samples were prepared for electron microscopy, fixed samples tended to become thin and prone to curling, thereby leading to improper positioning of the 6th and 7th muscles of the A2 and A3 segments.
We hereby report a new processing procedure that is more effective in preventing the curling of the samples compared to the traditional method of sample preparation7,16, by allowing the samples to stay flat during the subsequent dehydration, thereby facilitating better positioning of the Drosophila larval neuromuscular junctions.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1,2-Epoxypropane</td>
			<td>SHANGHAI LING FENG CHEMICAL REAGENT CO., LTD</td>
			<td>JYJ 037-2015</td>
			<td>Penetrating Agent</td>
		</tr>
		<tr>
			<td>Drosophila Stocks</td>
			<td>Bloomington</td>
			<td>none</td>
			<td>The wild-type control Drosophila strains used in this research were all W1118, and were reared according to standard culture methods</td>
		</tr>
		<tr>
			<td>Flat-bottomed glass test tubes</td>
			<td>Haimen Chenxing Experimental equipment Company&#160;</td>
			<td>none</td>
			<td>Flat-bottomed glass test tubes(bottle)with sponge plug(or bottle stopper)</td>
		</tr>
		<tr>
			<td>K4M cross-linker</td>
			<td>&#160;Agar Scientific</td>
			<td>Cat# 1924B</td>
			<td>The embedding resins are based on a highly cross-linked acrylate and methacrylate formula&#160;</td>
		</tr>
		<tr>
			<td>K4M resin (monomer B)</td>
			<td>&#160;Agar Scientific</td>
			<td>Lot# 631557</td>
			<td>Resin Monomer</td>
		</tr>
		<tr>
			<td>Polyvinyl film</td>
			<td>Haimen Chenxing Experimental equipment Company&#160;</td>
			<td>none</td>
			<td>Transparent polyethylene film is the best , thickness of about 0.2mm</td>
		</tr>
		<tr>
			<td>SPI Chem DDSA</td>
			<td>SPI</td>
			<td>SpI#02827-AF</td>
			<td>Dodecenyl Succinic Anhydride</td>
		</tr>
		<tr>
			<td>SPI-Chem DMP-30 Epoxy</td>
			<td>SPI</td>
			<td>02823-DA</td>
			<td>Accelerator</td>
		</tr>
		<tr>
			<td>SPI-Chem NMA</td>
			<td>SPI</td>
			<td>SpI#02828-AF</td>
			<td>Hardner for Epoxy</td>
		</tr>
		<tr>
			<td>SPI-PON 812 Epoxy</td>
			<td>SPI</td>
			<td>SPI#0259-AB</td>
			<td>Resin Monomer</td>
		</tr>
		<tr>
			<td>Steel mesh&#160;</td>
			<td>Yuhuiyuan Gardening Store(online)</td>
			<td>none</td>
			<td>Copper or stainless steel net</td>
		</tr>
		<tr>
			<td>Transmission electron microscopy</td>
			<td>Hitachi H-7650</td>
			<td>11416692</td>
			<td>All grids (on which samples were gathered) were stained with lead citrate and observed under a transmission electron microscopy.</td>
		</tr>
		<tr>
			<td>Ultrathin microtome</td>
			<td>Leica UC7 ultrathin microtome</td>
			<td>595915</td>
			<td>All sectioning operations are carried out on a Leica UC7 ultrathin microtome using a diamond knife</td>
		</tr>
	</tbody>
</table>

optimizing sample preparation process for transmission electron microscopy of neuromuscular junctions in drosophila larvae

The Drosophila neuromuscular junction (NMJ) has emerged as a valuable model system in the field of neuroscience. The application of confocal microscopy at the Drosophila NMJ enables researchers to acquire synaptic information, encompassing both quantitative data on synapse abundance and detailed insights into their morphology. However, the diffuse distribution and limited visual range of the TEM present challenges for the ultrastructural analysis. This study introduces an innovative and efficient sample preparation method that surpasses the conventional approach. The procedure begins by placing a metal mesh at the base of a flat-bottomed bottle or test tube, followed by positioning fixed larvae samples onto the mesh. An additional mesh is placed over the samples, ensuring that they are positioned between the two meshes. The fixed samples are thoroughly dehydrated and infiltrated before proceeding with the embedding procedure. Then embedding of the samples in epoxy resin is performed in a flat sheet manner, which allows for the preparation of muscles for positioning and sectioning. Benefiting from these steps, all the muscles of Drosophila larvae can be visualized under light microscopy, therey facilitating subsequent positioning and sectioning. Excess resin is removed after locating the 6th and 7th muscles of body segments A2 and A3. Serial ultra-thin sectioning of the 6th or 7th muscle is performed.

The Drosophila larva body wall is composed of 30 identifiable muscle fibers arranged in a regular pattern and looks like a thin slice after dissection and fixation21(Figure 1A). The sample remains flat during the dehydration process due to the presence of the metal meshes (Figure 1B, C). The larval body muscle is buried in a thin plate made of epoxy resin (Figure 1D-...

Watch this Scientific Journal Video about Optimizing Sample Preparation Process for Transmission Electron Microscopy of Neuromuscular Junctions in Drosophila Larvae at JoVE.com

Optimizing Sample Preparation Process for Transmission Electron Microscopy of Neuromuscular Junctions in Drosophila Larvae

This report provides a new sample preparation procedure for visualizing neuromuscular junctions in Drosophila Larvae. This method is more effective in preventing the curling of the samples compared to the traditional method and is particularly useful for Drosophila neuromuscular junction ultrastructural analysis.

Optimizing Sample Preparation Process for Transmission Electron Microscopy of Neuromuscular Junctions in Drosophila Larvae

The Drosophila neuromuscular junction (NMJ) has emerged as a valuable model system in the field of neuroscience. The application of confocal microscopy at ...

The diffused distribution and limited visual range of the TEM present challenges for the infrastructural analysis. This protocol presents an innovative and efficient sample preparation method that surpasses the conventional approach. This advanced method of TEM sample preparation is more effective in preventing the curling of the samples compared to the traditional method by allowing the samples to stay flat during the subsequent dehydration.The selection of reagents, and adjustment of dosage must be necessary depending on the sample type. There are many toxic chemical reagents used in the sample preparation process. Demonstrating the procedure will be Sheng Qingyuan, a master student from Dr.Gan Guangming's laboratory.To begin, dissect the wandering late third instar Drosophila larvae in Jan solution, and obtain the entire body wall per the standard procedures. Fix the larval body wall with the fixative in the dissection chamber overnight at four degrees Celsius. The next day, transfer the larval body wall from the dissection chamber to a 1.5 milliliter centrifuge tube, and rinse it several times with sodium cacodylate buffer.Fix the larval body wall in 1%osmium tetroxide for two hours. After fixation, wash the samples several times with distilled water. Add 2%saturated urinal acetate solution into the tube to stain the PHI neuromuscular junction.And after two hours, rinse the samples with deionized water. Next using scissors, cut two round pieces of metal mesh of pore size 270 microns. Place the metal mesh at the base of a flat bottomed bottle.Then place the fixed larvae on the mesh, followed by placing another mesh. Dehydrate the samples in an increasing ethanol concentration for 20 minutes each at four degrees Celsius. Then rinse the samples twice with propylene oxide at room temperature for five minutes each.Next, place the samples in a propylene oxide and epoxy resin solution, followed by pure epoxy resin for two hours at room temperature. For embedding, cut a polyethylene film into a big square and a small, hollow rectangular support. Glue the small square with the big square.Add sufficient epoxy resin at the center of the big square. Then turn on the stereoscope, and place the samples in the pre-positioned epoxy resin with the muscle side facing upwards. Add several drops of epoxy resin onto the samples, and cover them with polyethylene film.Place the samples for polymerization at increasing temperatures for 24 hours each. After polymerization, using a sharp blade, remove the excess parts of the larval body while retaining a trapezoid, including the A2 and A3 segment. Remove the trapezoid from the remaining larval body wall, and attach it to the resin-filled capsule with AB glue.Under a light microscope, confirm the position of the sixth and seventh muscles of the A2 and A3 segments, maintaining the tangent plane parallel to the sixth muscle. Then cut away one-fifth of the sample along the two sides of the A3 segment. Using a microtome, prepare an ultra thin section of the sample starting from the sixth muscle.After sectioning, attach as many slices as possible to each copper mesh. Use a transmission electron microscope to observe the samples. Among Lowicryl K4M resin and epoxy resin, Lowicryl K4M resin provided sharper and more easily observable results of the Drosophila body muscles.Confocal imaging demonstrated enhanced visualization of the neuromuscular junction between the sixth and seventh muscles. Transmission electron microscopy revealed bead-like neuromuscular junctions, offering improved synaptic structure information. The samples remained flat throughout the dehydration process due to the restriction of the metal meshes.Besides, the samples were polymerized between the plastic products, preventing the samples from folding. In the future, the TEM sample preparation method can be applied to brain and ventral nerve cord neuropil, thereby improving the potential of ultrastructural research.

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JoVE Journal

Neuroscience

Focussed Ion Beam Milling and Scanning Electron Microscopy of Brain Tissue

This protocol describes how biological samples, like brain tissue, can be imaged in three dimensions using the focussed ion beam/scanning electron microscope (FIB/SEM). The samples are fixed with aldehydes, heavy metal stained using osmium tetroxide and uranyl acetate. They are then dehydrated with alcohol and infiltrated with resin, which is then hardened. Using a light microscope and ultramicrotome with glass knives, a small block containing the region interest close to the surface is made. The block is then placed inside the FIB/SEM, and the ion beam used to roughly mill a vertical face along one side of the block, close to this region. Using backscattered electrons to image the underlying structures, a smaller face is then milled with a finer ion beam and the surface scrutinised more closely to determine the exact area of the face to be imaged and milled. The parameters of the microscope are then set so that the face is repeatedly milled and imaged so that serial images are collected through a volume of the block. The image stack will typically contain isotropic voxels with dimenions as small a 4 nm in each direction. This image quality in any imaging plane enables the user to analyse cell ultrastructure at any viewing angle within the image stack.

This protocol describes how resin embedded brain tissue can be prepared and imaged in the three dimensions in the focussed ion beam, scanning electron microscope.

This protocol describes how biological samples, like brain tissue, can be imaged in three dimensions using the focussed ion beam/scanning electron ...

Visualization of Proprioceptors in Drosophila Larvae and Pupae

Proprioception is the ability to sense the motion, or position, of body parts by responding to stimuli arising within the body. In fruitflies and other insects proprioception is provided by specialized sensory organs termed chordotonal organs (ChOs) 2. Like many other organs in Drosophila, ChOs develop twice during the life cycle of the fly. First, the larval ChOs develop during embryogenesis. Then, the adult ChOs start to develop in the larval imaginal discs and continue to differentiate during metamorphosis.
The development of larval ChOs during embryogenesis has been studied extensively 10,11,13,15,16. The centerpiece of each ChO is a sensory unit composed of a neuron and a scolopale cell. The sensory unit is stretched between two types of accessory cells that attach to the cuticle via specialized epidermal attachment cells 1,9,14. When a fly larva moves, the relative displacement of the epidermal attachment cells leads to stretching of the sensory unit and consequent opening of specific transient receptor potential vanilloid (TRPV) channels at the outer segment of the dendrite 8,12. The elicited signal is then transferred to the locomotor central pattern generator circuit in the central nervous system.
Multiple ChOs have been described in the adult fly 7. These are located near the joints of the adult fly appendages (legs, wings and halters) and in the thorax and abdomen. In addition, several hundreds of ChOs collectively form the Johnston's organ in the adult antenna that transduce acoustic to mechanical energy 3,5,17,4.
In contrast to the extensive knowledge about the development of ChOs in embryonic stages, very little is known about the morphology of these organs during larval stages. Moreover, with the exception of femoral ChOs 18 and Johnston's organ, our knowledge about the development and structure of ChOs in the adult fly is very fragmentary.
Here we describe a method for staining and visualizing ChOs in third instar larvae and pupae. This method can be applied together with genetic tools to better characterize the morphology and understand the development of the various ChOs in the fly.

Visualization of Proprioceptors in Drosophila Larvae and Pupae

A method to immunostain and visualize chordotonal organs in larvae and pupae of Drosophila melanogaster is described.

Proprioception is the ability to sense the motion, or position, of body parts by responding to stimuli arising within the body. In fruitflies and other ...

Appetitive Associative Olfactory Learning in Drosophila Larvae

In the following we describe the methodological details of appetitive associative olfactory learning in Drosophila larvae. The setup, in combination with genetic interference, provides a handle to analyze the neuronal and molecular fundamentals of specifically associative learning in a simple larval brain.
Organisms can use past experience to adjust present behavior. Such acquisition of behavioral potential can be defined as learning, and the physical bases of these potentials as memory traces1-4. Neuroscientists try to understand how these processes are organized in terms of molecular and neuronal changes in the brain by using a variety of methods in model organisms ranging from insects to vertebrates5,6. For such endeavors it is helpful to use model systems that are simple and experimentally accessible. The Drosophila larva has turned out to satisfy these demands based on the availability of robust behavioral assays, the existence of a variety of transgenic techniques and the elementary organization of the nervous system comprising only about 10,000 neurons (albeit with some concessions: cognitive limitations, few behavioral options, and richness of experience questionable)7-10.
Drosophila larvae can form associations between odors and appetitive gustatory reinforcement like sugar11-14. In a standard assay, established in the lab of B. Gerber, animals receive a two-odor reciprocal training: A first group of larvae is exposed to an odor A together with a gustatory reinforcer (sugar reward) and is subsequently exposed to an odor B without reinforcement 9. Meanwhile a second group of larvae receives reciprocal training while experiencing odor A without reinforcement and subsequently being exposed to odor B with reinforcement (sugar reward). In the following both groups are tested for their preference between the two odors. Relatively higher preferences for the rewarded odor reflect associative learning - presented as a performance index (PI). The conclusion regarding the associative nature of the performance index is compelling, because apart from the contingency between odors and tastants, other parameters, such as odor and reward exposure, passage of time and handling do not differ between the two groups9.

Appetitive Associative Olfactory Learning in Drosophila Larvae

Drosophila larvae are able to associate odor stimuli with gustatory reward. Here we describe a simple behavioral paradigm that allows the analysis of appetitive associative olfactory learning.

In the following we describe the methodological  details of appetitive associative olfactory learning in Drosophila larvae. The setup, in combination with ...

Preparation of Non-human Primate Brain Tissue for Pre-embedding Immunohistochemistry and Electron Microscopy

Despite all the technological advances at the light microscopy&#160;level, electron microscopy remains the only tool in neuroscience to examine and characterize ultrastructural and morphological details of neurons, such as synaptic contacts. Good preservation of brain tissue for electron microscopy can be obtained by rigorous cryo-fixation methods, but these techniques are rather costly and limit the use of immunolabeling, which is crucial to understand the connectivity of identified neuronal systems. Freeze-substitution methods have been developed to allow the combination of cryo-fixation with immunolabeling. However, the reproducibility of these methodological approaches usually relies on costly freezing devices. Moreover, achieving reliable results with this technique is very time-consuming and skill-challenging. Hence, the traditional chemically fixed brain, particularly with acrolein fixative, remains a time-efficient and low-cost method to combine electron microscopy with immunohistochemistry. Here, we provide a reliable experimental protocol using chemical acrolein fixation that leads to the preservation of primate brain tissue and is compatible with pre-embedding immunohistochemistry and transmission electron microscopic examination.

Here, we provide an easy, low-cost, and time-efficient protocol to chemically fix primate brain tissue with acrolein fixative, allowing for long-term preservation that is compatible with pre-embedding immunohistochemistry for transmission electron microscopy.

Despite all the technological advances at the light microscopy&#160;level, electron microscopy remains the only tool in neuroscience to examine and ...

Novel Assay for Cold Nociception in Drosophila Larvae

How organisms sense and respond to noxious temperatures is still poorly understood. Further, the mechanisms underlying sensitization of the sensory machinery, such as in patients experiencing peripheral neuropathy or injury-induced sensitization, are not well characterized. The genetically tractable Drosophila model has been used to study the cells and genes required for noxious heat detection, which has yielded multiple conserved genes of interest. Little is known however about the cells and receptors important for noxious cold sensing. Although, Drosophila does not survive prolonged exposure to cold temperatures (&#8804;10 &#186;C), and will avoid cool, preferring warmer temperatures in behavioral preference assays, how they sense and possibly avoid noxious cold stimuli has only recently been investigated.
Here we describe and characterize the first noxious cold (&#8804;10 &#186;C) behavioral assay in Drosophila. Using this tool and assay, we show an investigator how to qualitatively and quantitatively assess cold nociceptive behaviors. This can be done under normal/healthy culture conditions, or presumably in the context of disease, injury or sensitization. Further, this assay can be applied to larvae selected for desired genotypes, which might impact thermosensation, pain, or nociceptive sensitization. Given that pain is a highly conserved process, using this assay to further study&#160;thermal nociception will likely glean important understanding of pain processes in other species, including vertebrates.

Novel Assay for Cold Nociception in Drosophila Larvae

Here we demonstrate a novel assay to study cold nociception in Drosophila larvae. This assay utilizes a custom-built Peltier probe capable of applying a focal noxious cold stimulus and results in quantifiable cold-specific behaviors. This technique will allow further cellular and molecular dissection of cold nociception.

How organisms sense and respond to noxious temperatures is still poorly understood. Further, the mechanisms underlying sensitization of the sensory ...

Levator Auris Longus Preparation for Examination of Mammalian Neuromuscular Transmission Under Voltage Clamp Conditions

This protocol describes a technique to record synaptic transmission from the neuromuscular junction under current-clamp and voltage-clamp conditions. An ex vivo preparation of the levator auris longus (LAL) is used because it is a thin muscle that provides easy visualization of the neuromuscular junction for microelectrode impalement at the motor endplate. This method allows for the recording of spontaneous miniature endplate potentials and currents (mEPPs and mEPCs), nerve-evoked endplate potentials and currents (EPPs and EPCs), as well as the membrane properties of the motor endplate. Results obtained from this method include the quantal content (QC), number of vesicle release sites (n), probability of vesicle release (prel), synaptic facilitation and depression, as well as the muscle membrane time constant (&#964;m) and input resistance. Application of this technique to mouse models of human disease can highlight key pathologies in disease states and help identify novel treatment strategies. By fully voltage-clamping a single synapse, this method provides one of the most detailed analyses of synaptic transmission currently available.

Levator Auris Longus Preparation for Examination of Mammalian Neuromuscular Transmission Under Voltage Clamp Conditions

The protocol described in this paper uses the mouse levator auris longus (LAL) muscle to record spontaneous and nerve-evoked postsynaptic potentials (current-clamp) and currents (voltage-clamp) at the neuromuscular junction. Use of this technique can provide key insights into mechanisms of synaptic transmission under normal and disease conditions.

This protocol describes a technique to record synaptic transmission from the neuromuscular junction under current-clamp and voltage-clamp conditions. An ...

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 ...

Characterization of Neuromuscular Junctions in Mice by Combined Confocal and Super-Resolution Microscopy

Neuromuscular junctions (NMJs) are highly specialized synapses between lower motor neurons and skeletal muscle fibers that play an essential role in the transmission of molecules from the nervous system to voluntary muscles, leading to contraction. They are affected in many human diseases, including inherited neuromuscular disorders such as Duchenne muscular dystrophy (DMD), congenital myasthenic syndromes (CMS), spinal muscular atrophy (SMA), and amyotrophic lateral sclerosis (ALS). Therefore, monitoring the morphology of neuromuscular junctions and their alterations in disease mouse models represents a valuable tool for pathological studies and preclinical assessment of therapeutic approaches. Here, methods for labeling and analyzing the three-dimensional (3D) morphology of the pre- and postsynaptic parts of motor endplates from murine teased muscle fibers are described. The procedures to prepare samples and measure NMJ volume, area, tortuosity and axon terminal morphology/occupancy by confocal imaging, and the distance between postsynaptic junctional folds and acetylcholine receptor (AChR) stripe width by super-resolution stimulated emission depletion (STED) microscopy are detailed. Alterations in these NMJ parameters are illustrated in mutant mice affected by SMA and CMS.

This protocol describes a method for morphometric analysis of neuromuscular junctions by combined confocal and STED microscopy that is used to quantify pathological changes in mouse models of SMA and ColQ-related CMS.

Neuromuscular junctions (NMJs) are highly specialized synapses between lower motor neurons and skeletal muscle fibers that play an essential role in the ...

Viewing Microtubule Networks in &lt;em&gt;Drosophila&lt;/em&gt; Neuromuscular Junctions and Muscle Cells

Using Drosophila Larval Neuromuscular Junction and Muscle Cells to Visualize Microtubule Network

The microtubule network is an essential component of the nervous system. Mutations in many microtubules regulatory proteins are associated with neurodevelopmental disorders and neurological diseases, such as microtubule-associated protein Tau to neurodegenerative diseases, microtubule severing protein Spastin and Katanin 60 cause hereditary spastic paraplegia and neurodevelopmental abnormalities, respectively. Detection of microtubule networks in neurons is advantageous for elucidating the pathogenesis of neurological disorders. However, the small size of neurons and the dense arrangement of axonal microtubule bundles make visualizing the microtubule networks challenging. In this study, we describe a method for dissection of the larval neuromuscular junction and muscle cells, as well as immunostaining of &#945;-tubulin and microtubule-associated protein Futsch to visualize microtubule networks in Drosophila melanogaster. The neuromuscular junction permits us to observe both pre-and post-synaptic microtubules, and the large size of muscle cells in Drosophila larva allows for clear visualization of the microtubule network. Here, by mutating and overexpressing Katanin 60 in Drosophila melanogaster,&#160;and then examining the microtubule networks in the neuromuscular junction and muscle cells, we&#160;accurately reveal the regulatory role of Katanin 60 in neurodevelopment. Therefore, combined with the powerful genetic tools of Drosophila&#160;melanogaster, this protocol greatly facilitates genetic screening and microtubule dynamics analysis for the role of microtubule network regulatory proteins in the nervous system.

Author Spotlight: Understanding Microtubule Network in Drosophila Neuromuscular Junctions 

Here, we present a detailed protocol to visualize the microtubule networks in neuromuscular junctions and muscle cells. Combined with the powerful genetic tools of Drosophila melanogaster, this protocol greatly facilitates genetic screening and microtubule-dynamics analysis for the role of microtubule network regulatory proteins in the nervous system.

The microtubule network is an essential component of the nervous system. Mutations in many microtubules regulatory proteins are associated with ...

SFEMG in Rodents: Assessing NMJ Function in Health and Disease

Stimulated Single Fiber Electromyography (SFEMG) for Assessing Neuromuscular Junction Transmission in Rodent Models

As the final connection between the nervous system and muscle, transmission at the neuromuscular junction (NMJ) is crucial for normal motor function. Single fiber electromyography (SFEMG) is a clinically relevant and sensitive technique that measures single muscle fiber action potential responses during voluntary contractions or nerve stimulations to assess NMJ transmission. The assessment and quantification of NMJ transmission involves two parameters: jitter and blocking. Jitter refers to the variability in timing (latency) between consecutive single-fiber action potentials (SFAPs). Blocking signifies the failure of NMJ transmission to initiate an SFAP response. Although SFEMG is a well-established and sensitive test in clinical settings, its application in preclinical research has been relatively infrequent. This report outlines the steps and criteria employed in performing stimulated SFEMG to quantify jitter and blocking in rodent models. This technique can be used in preclinical and clinical studies to gain insights into NMJ function in the context of health, aging, and disease.

Author Spotlight: Translational Applications of Stimulated SFEMG in Rodent Models

In this study, we demonstrate a refined single fiber electromyography (SFEMG) protocol to allow in vivo measurement of neuromuscular junction (NMJ) transmission in rodent models. A step-by-step approach to the SFEMG technique is described to allow quantification of NMJ transmission variability and failure in rat gastrocnemius muscle.

As the final connection between the nervous system and muscle, transmission at the neuromuscular junction (NMJ) is crucial for normal motor function. ...