We would like to thank all members of the Keller and Magie Labs at Quinnipiac University for helpful suggestions. In particular, we would like to thank Barron L. Lincoln II for development of this injury assay within the Keller Lab. We would also like to thank Quinnipiac University College of Arts and Science Grant-In-Aid awarded to L.C. Keller.

1. Preparation of Reagents and Equipment
<ol>
	<li>Prepare 1x Dissection Buffer (70 mM NaCl, 5 mM KCl, 0.02 mM CaCl2, 20 mM MgCl2, 10 mM NaHCO3, 115 mM sucrose, 5 mM trehalose, 5 mM HEPES;&#160;pH 7.2).</li>
	<li>Prepare 1x Phosphate-Buffered Saline (PBS).</li>
	<li>Prepare 1x PBT using 1x PBS with 0.01% Triton X-100.</li>
	<li>Prepare fruit juice agar plates.14 Briefly, mix 30 g agar in 700 mL of H2O and autoclave. Dissolve 0.5 g of methyl paraben in 10 mL of ethanol and add solution to 300 mL of fruit juice concentrate (grape or apple). Mix concentrate into autoclaved agar solution and pour into the lids of 10 mm x 35 mm Petri dishes. 
	NOTE: Grape agar power premix can also be purchased from various companies (see Tabls of Materials).</li>
	<li>Obtain size 5 forceps that allow one to mechanically injure the larvae.</li>
	<li>Use standard Drosophila CO2 based anesthesia apparatus.</li>
</ol>
2. Selecting Drosophila Larvae
<ol>
	<li>Take a vial or bottle of Drosophila containing wandering third instar larvae that have been cultured at 25 &#176;C.</li>
	<li>Select ten individual 2nd or 3rd&#160;instar larvae based on appearance. Third instar larvae can be identified by the appearance of anterior branched spiracles, while second instar larvae are smaller and have more club-like anterior spiracles. 
	NOTE: Larval stages can also be identified by timing. At 25 &#176;C, second instar larvae appear approximately 48 h after hatching, and third instar larvae molt approximately 24 h later. If interested in examining neurodegeneration at the NMJ, second instar larvae need to be injured.</li>
</ol>
3. Preparing Drosophila Larvae for Mechanical Injury
<ol>
	<li>Carefully pick individual larvae up by forceps or a paintbrush, being cautious not to compress it in anyway.</li>
	<li>Directly place ten larvae into glass dish containing cold 1X PBS or dissection buffer to remove any food debris and to decelerate larval motility.</li>
</ol>
4. Mechanical Injury and Treatment of Drosophila Larvae
<ol>
	<li>Place each individual larva onto a CO2 anesthetizing apparatus.</li>
	<li>Under a dissecting microscope, carefully roll each larva onto their dorsal side in order to visualize the segmental nerves through the cuticle.</li>
	<li>Position size 5 forceps approximately 1/2 to 2/3 way down the length of the larva starting at the mouth hooks. Once positioned, pinch approximately 1/3 of the ventral cuticle containing the segmental nerves with size 5 forceps.
	<ol>
		<li>To ensure that larval segmental nerves are injured, apply sufficient force to crush the segmental nerves but leave the cuticle intact. To determine the correct amount of force, crush 10 larvae and ensure the death rate after 5 h is under 50%.</li>
	</ol>
	</li>
	<li>After injury, carefully transfer larvae to a fruit juice agar plate containing approximately 0.5 g of yeast paste. Place each larva so its anterior end is on the yeast paste, for continued feeding despite disrupted motility. 
	NOTE: To ensure that larval segmental nerves have been injured, disrupted larval motility can be observed after transfer to the agar plate. Injured larva are effectively paralyzed posterior to the site of injury, but can still move their mouth hooks and feed. A high death rate of animals after injury is common so it is best to injure 20-50% more animals than is necessary for an experiment.</li>
	<li>Place agar plates containing yeast paste and 10 injured larvae into the bottom of an empty 100 x 15 mm petri dish. Cover this petri plate, now containing the injured larvae on an agar plate with a moist paper towel, ensuring that the paper towel does not touch the larvae or the agar plates. Place this Petri dish into a larger air-tight container, at RT.</li>
	<li>Retrieve larvae for dissection after specified periods (6, 12, or 24 h) post-injury. 
	NOTE: To examine immediate effects of injury on the axonal cytoskeleton, larvae can be dissected directly after injury. To examine axonal transport defects, larvae can be dissected approximately 6 h after injury. About 12 h after injury a build-up of ubiquitinated proteins can be observed, and 24 h after injury, degeneration of motor neurons at the NMJ can be observed.</li>
</ol>
5. Analysis of Neurodegeneration at the NMJ
<ol>
	<li>Dissect Drosophila larval NMJ as described previously.15,16 Briefly, pin larvae onto a Sylgard plate, cut along the dorsal surface, and fillet with pins in a drop of dissection buffer to expose the body wall musculature. Fix larvae in either 4% paraformaldehyde (PFA) or Bouin&#39;s Solution depending on the antibodies used to visualize neurons and muscle. 
	NOTE: PFA fixation should be used if fluorescent protein tags, such as Green Fluorescent Protein (GFP) is to be visualized as Bouin&#39;s fixative can be too harsh.</li>
	<li>Perform immunofluorescence, which has been described previously11,13,16, to simultaneously mark presynaptic motor neurons and adjacent postsynaptic (SSR) muscle folds. Visualize presynaptic membranes and axons with fluorescently conjugated horseradish peroxidase (HRP) (1:300)17 and active zones can be stained using an anti-Bruchpilot (Brp) antibody (nc82; 1:100; Developmental Studies Hybridoma Bank). Simultaneously label post-synaptic muscles with an anti-Dics Large (Dlg) antibody (1:10,000).18</li>
	<li>Perform an established assay for quantifying neurodegeneration at the NMJ as described previously.8,9,10,11,12,13,14 Briefly, simultaneously visualize individual NMJs for both pre- and post-synaptic compartments. Any boutons labeled with postsynaptic markers but not presynaptic markers indicate sites of neurodegeneration (Figure 1). The average number of boutons per NMJ as well as the average number of NMJs per animal can be quantified.</li>
</ol>

<ol>
	<li>Bier, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophilia,+the+golden+bug,+emerges+as+a+tool+for+human+genetics.">Drosophilia, the golden bug, emerges as a tool for human genetics.</a> Nat. Rev. Genet. 6 (1), 9-23 (2005).</li><li>Ugur, B., Chen, K., Bellen, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+tools+and+assays+for+the+study+of+human+diseases.">Drosophila tools and assays for the study of human diseases.</a> Dis Model Mech. 9 (3), 235-244 (2016).</li><li>McGurk, L., Berson, A., Bonini, N. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+as+an+in+vivo+model+for+human+neurodegenerative+disease.">Drosophila as an in vivo model for human neurodegenerative disease.</a> Genetics. 201 (2), 377-402 (2015).</li><li>Shin, J. E., Cho, Y., Beirowski, B., Milbrandt, J., Cavalli, V., DiAntonio, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual+leucine+zipper+kinase+is+required+for+retrograde+injury+signaling+and+axonal+regeneration.">Dual leucine zipper kinase is required for retrograde injury signaling and axonal regeneration.</a> Neuron. 74 (6), 1015-1022 (2012).</li><li>Xiong, X., Wang, X., Ewanek, R., Bhat, P., Diantonio, A., Collins, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+turnover+of+the+Wallenda/DLK+kinase+regulates+a+retrograde+response+to+axonal+injury.">Protein turnover of the Wallenda/DLK kinase regulates a retrograde response to axonal injury.</a> J Cell Biol. 191 (1), 211-223 (2010).</li><li>Xiong, X., Collins, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+conditioning+lesion+protects+axons+from+degeneration+via+the+Wallenda/DLK+MAP+kinase+signaling+cascade.">A conditioning lesion protects axons from degeneration via the Wallenda/DLK MAP kinase signaling cascade.</a> J Neurosci. 32 (2), 610-615 (2012).</li><li>Mishra, B., Ghannad-Rezaie, M., Li, J., Wang, X., Hao, Y., Ye, B., Chronis, N., Collins, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+microfluidics+chips+for+live+imaging+and+study+of+injury+responses+in+Drosophila+larvae.">Using microfluidics chips for live imaging and study of injury responses in Drosophila larvae.</a> J Vis Exp. (84), e50998 (2014).</li><li>Eaton, B. A., Fetter, R. D., Davis, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynactic+is+necessary+for+synapse+stabilization.">Dynactic is necessary for synapse stabilization.</a> Neuron. 34 (5), 729-741 (2002).</li><li>Eaton, B. A., Davis, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LIM+Kinase1+controls+synaptic+stability+downstream+of+the+type+II+BMP+receptor.">LIM Kinase1 controls synaptic stability downstream of the type II BMP receptor.</a> Neuron. 47 (5), 695-708 (2005).</li><li>Pielage, J., Fetter, R. D., Davis, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Presynaptic+spectrin+is+essential+for+synapse+stabilization.">Presynaptic spectrin is essential for synapse stabilization.</a> Curr Biol. 15 (10), 918-928 (2005).</li><li>Pielage, J., Cheng, L., Fetter, R. D., Carlton, P. M., Sedat, J. W., Davis, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+presynaptic+giant+Ankyrin+stabilizes+the+NMJ+through+regulation+or+presynaptic+microtubules+and+transsynaptic+cell+adhesion.">A presynaptic giant Ankyrin stabilizes the NMJ through regulation or presynaptic microtubules and transsynaptic cell adhesion.</a> Neuron. 58 (2), 195-209 (2008).</li><li>Massaro, C. M., Pielage, J., Davis, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+mechanisms+that+enhance+synapse+stability+despite+persistent+disruption+of+the+spectrin/ankryin/microtubule+cytoskeleton.">Molecular mechanisms that enhance synapse stability despite persistent disruption of the spectrin/ankryin/microtubule cytoskeleton.</a> J Cell Biol. 187 (1), 101-117 (2009).</li><li>Lincoln, B. L., Alabsi, S. H., Frendo, N., Freund, R., Keller, L. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+neuronal+injury+follows+a+temporal+sequence+of+cellular+events+leading+to+degeneration+at+the+neuromuscular+junction.">Drosophila neuronal injury follows a temporal sequence of cellular events leading to degeneration at the neuromuscular junction.</a> J Exp Neurosci. 9, 1-9 (2015).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+apple+juice-agar+plates.">Drosophila apple juice-agar plates.</a> Cold Spring Harb Protoc. , (2011).</li><li>Brent, J. R., Werner, K. M., McCabe, B. 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+immunohistochemistry.">Drosophila larval NMJ immunohistochemistry.</a> J Vis Exp. (25), (2009).</li><li>Smith, R., Taylor, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissection+and+imaging+of+active+zones+in+the+Drosophila+neuromuscular+junction.">Dissection and imaging of active zones in the Drosophila neuromuscular junction.</a> J Vis Exp. (50), (2011).</li><li>Jan, L., Jan, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antibodies+to+horseradish+peroxidase+as+specific+neuronal+markers+in+Drosophila+and+in+grasshopper+embryos.">Antibodies to horseradish peroxidase as specific neuronal markers in Drosophila and in grasshopper embryos.</a> Proc. Natl. Acad. Sci. 79 (8), 2700-2704 (1982).</li><li>Lahey, T., Gorczyca, M., Jia, X., Budnik, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Drosophila+tumor+suppressor+gene+dlg+is+required+for+normal+synaptic+bouton+structure.">The Drosophila tumor suppressor gene dlg is required for normal synaptic bouton structure.</a> Neuron. 13 (4), 823-835 (1994).</li></ol>

The authors have nothing to disclose.

The neuronal mechanical injury described earlier and demonstrated here can be used to induce injury/stress in the segmental nerves of Drosophila larvae.4,5,6,14 This experimental technique has been employed previously to dissect the temporal sequence of events leading to neurodegeneration, as well as to examine transcriptional changes in the motor neuron cell bodies post injury.5,14 Additionally, this technique has been described in conjunction with microfluidics chips in order to observe and study axonal degeneration and regeneration in Drosophila larvae.7 Limitations of this technique include death of the larvae due to puncturing of the cuticle during introduction of the injury. However, a large number of larvae can be crushed in a short period of time to overcome a high larval death rate. A modification that we have included is the injury of 2nd instar or early 3rd instar larvae, which is critical to visualize motor neuron degeneration at the NMJ, which occurs 24 h post injury.
Here, we demonstrate that neuronal mechanical injury can be utilized to study motor neuron degeneration at the NMJ. We use an established method to quantify neurodegeneration that takes advantage of the fact that neurons and their associated proteins degenerate more rapidly than the adjacent muscle.8,9,10,11,12,13,14 To observe and quantify neurodegeneration, it is critical that the NMJ be simultaneously stained for both pre- and postsynaptic markers. Here, we demonstrate the use of the active zone marker Brp and the postsynaptic marker Dlg, however, there are a plethora of other pre- and postsynaptic markers available that may be utilized to study neurodegeneration at the NMJ. Additionally, fluorescently-tagged molecules of one&#39;s choosing may be employed to study their effects during the neurodegenerative process. There are more complicated methods to study degeneration after axonal injury, such as microfluidics7, however our method has several advantages: 1) it is very inexpensive, 2) most Drosophila labs already have the necessary equipment, and 3) the tissue is fixed so conventional fluorescence microscopy can be used to quantify neurodegenerative events post injury.
We envision that this protocol may be adapted to examine a wide-range of cellular and molecular mechanisms related to neurodegeneration after injury. In particular, these methods could be used to examine the behavior of any fluorescently-tagged protein before and after neuronal injury and motor neuron degeneration and regeneration.

Neuronal degeneration occurs during normal development and can be caused by the natural aging process, injury, stress, or disease states. Drosophila melanogaster, the common fruit fly, provides a simple and powerful model organism to study neurodegeneration due to the remarkable similarities in the molecular mechanisms that drive the degeneration of neurons. These similarities are highlighted by the fact that approximately 70% of disease-associated human genes have a Drosophila homolog.1 Additionally, numerous assays and technological tools to study human neurodegenerative diseases have been developed and utilized in Drosophila.2,3 Within Drosophila, the neuromuscular junction (NMJ) allows for analysis of both cellular and electrophysiological properties and has proven to be an important system to study neuromuscular disease due to the visible neuron-muscle connections.2 In this study, we describe an in vivo neuron injury assay in Drosophila larvae which allows for the reproducible injury of segmental nerves. This motoneuron injury results in a temporal sequence of cellular events resulting in neurodegeneration at the NMJ 24 h&#160;post injury. The ability to reproducibly injury motoneurons resulting in neurodegeneration has diverse applications such as identifying specific genes required for the degenerative process, the dissection of transcriptional responses to neuronal injury, and the analysis of protective signaling cascades.4,5,6 This method has also been used in combination with microfluidics to study neuronal degeneration and regeneration in live animals.7
We utilize an established quantitative assay to examine motor neuron degeneration at the Drosophila NMJ after mechanical injury. This assay is based on the fact that loss of presynaptic membrane and proteins precedes the disassembly of the subsynaptic reticulum (SSR) characterized by the postsynaptic muscle membrane folds.8,9,10,11,12,13 This assay allows for the quantification of &#34;synaptic footprints&#34; where the pre-synaptic neuron has lost connection to the adjacent postsynaptic muscle. The degenerative process has been shown to be progressive throughout larval development12 and cannot be accounted for by altered synapse development or sprouting.8,9,10,11,12 The advantage of using mechanical injury over preexisting mutations is that it allows for dissection of the temporal sequence of cellular events leading up to neurodegeneration at the NMJ.13

<table><tbody><tr><td>Micro-dissecting scissors</td><td>Fine Science Tools</td><td>15000-08</td><td></td></tr><tr><td>Dumont #3 Forceps</td><td>Fine Science Tools</td><td>11231-30</td><td>Some people prefer size 3, while others prefer size 5</td></tr><tr><td>Dumont #5 Forceps</td><td>Fine Science Tools</td><td>11251-30</td><td>Some people prefer size 3, while others prefer size 5</td></tr><tr><td>CO&lt;sub&gt;2&lt;/sub&gt; Air Tank</td><td>Tech Air</td><td>UN 1013</td><td>Various tank sizes can be purchased</td></tr><tr><td>CO&lt;sub&gt;2&lt;/sub&gt; Anesthetizing Apparatus</td><td>Genesee Scientific</td><td>59-114</td><td></td></tr><tr><td>Stainless-steel pins, size 0.1</td><td>Fine Science Tools</td><td>26002-10</td><td></td></tr><tr><td>SylGard 184 Silicone Elastomer, Base and Curing Agent</td><td>Dow Corning</td><td>3097358-1004</td><td>To pour dissecting plates</td></tr><tr><td>Bouin&#039;s Solution</td><td>Sigma</td><td>HT 10132-1L</td><td>Antibodies should be tested for their efficiency in Bouin&#039;s and PFA</td></tr><tr><td>4% Paraformaldehyde (PFA) in Phosphate-Buffered Saline (PBS)</td><td>Affymetrix</td><td>FLY-8030-20</td><td>Antibodies should be tested for their efficiency in Bouin&#039;s and PFA</td></tr><tr><td>Dissecting Stereo MIcroscope</td><td>AmScope</td><td>SM-1BZ</td><td></td></tr><tr><td>Light Source</td><td>AmScope</td><td>HL150-AY-220V</td><td></td></tr><tr><td>anti- nc82 antibody</td><td>Developmental Studies Hybridoma Bank</td><td>nc82-s</td><td></td></tr><tr><td>anti-discs large antibody</td><td>Developmental Studies Hybridoma Bank</td><td>AF3</td><td></td></tr><tr><td>Alexa Fluor anti-horseradish peroxidase</td><td>Jackson Immunoresearch</td><td>123-545-021; 123-585-021; 123-605-021</td><td>One can you Alexa Fluor&amp;reg; 488, 594 or 647</td></tr><tr><td>Flystuff Grape Juice Agar Premix</td><td>Genesee Scientific</td><td>47-102</td><td></td></tr><tr><td>Microscope slides</td><td>Genesee Scientific</td><td>29-101</td><td></td></tr><tr><td>Glass Coverslips</td><td>Fisher Scientific</td><td>12-545-87</td><td></td></tr><tr><td>Thermo Scientific Nalgene Utility Box</td><td>Fisher Scientific</td><td>03-484C</td><td>Used to create humid chamber for larval recovery</td></tr></tbody></table>

a simple neuronal mechanical injury methodology to study drosophila motor neuron degeneration

The degeneration of neurons occurs during normal development and in response to injury, stress, and disease. The cellular hallmarks of neuronal degeneration are remarkably similar in humans and invertebrates as are the molecular mechanisms that drive these processes. The fruit fly, Drosophila melanogaster, provides a powerful yet simple genetic model organism to study the cellular complexities of neurodegenerative diseases. In fact, approximately 70% of disease-associated human genes have a Drosophila homolog and a plethora of tools and assays have been described using flies to study human neurodegenerative diseases. More specifically the neuromuscular junction (NMJ) in Drosophila has proven to be an effective system to study neuromuscular diseases because of the ability to analyze the structural connections between the neuron and the muscle. Here, we report on an in vivo motor neuron injury assay in Drosophila, which reproducibly induces neurodegeneration at the NMJ by 24 h. Using this methodology, we have described a temporal sequence of cellular events resulting in motor neuron degeneration. The injury method has diverse applications and has also been utilized to identify specific genes required for neurodegeneration and to dissect transcriptional responses to neuronal injury.

Using the procedure presented here, we have demonstrated that mechanical neuronal injury allows for temporal dissection of neurodegenerative events.14,18 The sequence of events has been previously characterized and begins with an immediate disruption of the cytoskeleton, followed by axonal trafficking defects, an accumulation of ubiquitinated proteins, and subsequent neurodegeneration 24 h post-injury. Prior to injury, WT NMJs show the presynaptic active zone marker Brp in apposition to the postsynaptic marker Dlg throughout the entire NMJ (Figure 1A). Mechanical injury of segmental nerves can induce moderate to severe neurodegeneration in which boutons stained with Dlg now lack the presynaptic active zone protein Brp (Figure 1B). Any bouton that is stained with Dlg but lacks Brp staining is considered a &#34;synaptic footprint&#34; and can be counted and quantified as a neurodegenerative event. Both the frequency and severity of the neurodegenerative phenotype can be quantified as described previously.11
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56128/56128fig1.jpg" /> 
Figure 1: Mechanical neuronal injury induces neurodegeneration at the NMJ of muscle 6/7. (A) Uninjured NMJs show the pre-synaptic active zone marker, Brp (green) in apposition with the postsynaptic marker, Dlg (red) throughout the entire NMJ. (B) Neuronal mechanical injury induces neurodegeneration indicated by Dlg stained boutons (red) with the loss of Brp. Arrowheads indicate individual sites of neurodegeneration. Scale bar = 10 &#181;m. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56128/56128fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about A Simple Neuronal Mechanical Injury Methodology to Study Drosophila Motor Neuron Degeneration at JoVE.com

A Simple Neuronal Mechanical Injury Methodology to Study Drosophila Motor Neuron Degeneration

Here we describe a simple and widely accessible method to injure segmental nerves in Drosophila larvae to visualize and quantify neurodegeneration of motor neurons at the neuromuscular junction (NMJ) of third instar larvae.

A Simple Neuronal Mechanical Injury Methodology to Study Drosophila Motor Neuron Degeneration

The degeneration of neurons occurs during normal development and in response to injury, stress, and disease. The cellular hallmarks of neuronal ...

a-simple-neuronal-mechanical-injury-methodology-to-study-drosophila

Nanyang Technological University

Research

JoVE Journal

Neuroscience

5.5K Views.  Quinnipiac University.  Hier beschrijven we een eenvoudige en breed toegankelijke methode om segmentale zenuwen in Drosophila larven te beschadigen om neurodegeneratie van motorische neuronen bij de neuromusculaire verbinding (NMJ) van derde instar larven te visualiseren en te kwantificeren. 

Video: A Simple Neuronal Mechanical Injury Methodology to Study Drosophila Motor Neuron Degeneration

Using Microfluidics Chips for Live Imaging and Study of Injury Responses in Drosophila Larvae

Live imaging is an important technique for studying cell biological processes, however this can be challenging in live animals. The translucent cuticle of the Drosophila larva makes it an attractive model organism for live imaging studies. However, an important challenge for live imaging techniques is to noninvasively immobilize and position an animal on the microscope. This protocol presents a simple and easy to use method for immobilizing and imaging Drosophila larvae on a polydimethylsiloxane (PDMS) microfluidic device, which we call the 'larva chip'. The larva chip is comprised of a snug-fitting PDMS microchamber that is attached to a thin glass coverslip, which, upon application of a vacuum via a syringe, immobilizes the animal and brings ventral structures such as the nerve cord, segmental nerves, and body wall muscles, within close proximity to the coverslip. This allows for high-resolution imaging, and importantly, avoids the use of anesthetics and chemicals, which facilitates the study of a broad range of physiological processes. Since larvae recover easily from the immobilization, they can be readily subjected to multiple imaging sessions. This allows for longitudinal studies over time courses ranging from hours to days. This protocol describes step-by-step how to prepare the chip and how to utilize the chip for live imaging of neuronal events in 3rd instar larvae. These events include the rapid transport of organelles in axons, calcium responses to injury, and time-lapse studies of the trafficking of photo-convertible proteins over long distances and time scales. Another application of the chip is to study regenerative and degenerative responses to axonal injury, so the second part of this protocol describes a new and simple procedure for injuring axons within peripheral nerves by a segmental nerve crush.

Using Microfluidics Chips for Live Imaging and Study of Injury Responses in Drosophila Larvae

Drosophila larvae are an attractive model system for live imaging due to their translucent cuticle and powerful genetics. This protocol describes how to utilize a single-layer PDMS device, called the &#39;larva chip&#39; for live imaging of cellular processes within neurons of 3rd instar Drosophila larvae.

Live imaging is an important technique for studying cell biological processes, however this can be challenging in live animals. The translucent cuticle of ...

Bioengineering

An Injury Paradigm to Investigate Central Nervous System Repair in Drosophila

An experimental method has been developed to investigate the cellular responses to central nervous system (CNS) injury using the fruit-fly Drosophila. Understanding repair and regeneration in animals is a key question in biology. The damaged human CNS does not regenerate, and understanding how to promote the regeneration is one of main goals of medical neuroscience. The powerful genetic toolkit of Drosophila can be used to tackle the problem of CNS regeneration.
A lesion to the CNS ventral nerve cord (VNC, equivalent to the vertebrate spinal cord) is applied manually with a tungsten needle. The VNC can subsequently be filmed in time-lapse using laser scanning confocal microscopy for up to 24 hr to follow the development of the lesion over time. Alternatively, it can be cultured, then fixed and stained using immunofluorescence to visualize neuron and glial cells with confocal microscopy. Using appropriate markers, changes in cell morphology and cell state as a result of injury can be visualized. With ImageJ and purposely developed plug-ins, quantitative and statistical analyses can be carried out to measure changes in wound size over time and the effects of injury in cell proliferation and cell death. These methods allow the analysis of large sample sizes. They can be combined with the powerful genetics of Drosophila to investigate the molecular mechanisms underlying CNS regeneration and repair.

An Injury Paradigm to Investigate Central Nervous System Repair in Drosophila

An injury paradigm using the Drosophila larval ventral nerve cord to investigate central nervous system regeneration and repair is described. Stabbing followed by laser scanning confocal microscopy in time-lapse and fixed specimens, combined with quantitative analysis with purposefully developed software and genetics, are used to investigate the molecular mechanisms of CNS regeneration and repair.

An experimental method has been developed to investigate the cellular responses to central nervous system (CNS) injury using the fruit-fly Drosophila. ...

Retrograde Tracing of Drosophila Embryonic Motor Neurons Using Lipophilic Fluorescent Dyes

We describe a technique for retrograde labeling of motor neurons in Drosophila. We use an oil-dissolved lipophilic dye and deliver a small droplet to an embryonic fillet preparation by a microinjector. Each motor neuron whose membrane is contacted by the droplet can then be rapidly labeled. Individual motor neurons are continuously labeled, enabling fine structural details to be clearly visualized. Given that lipophilic dyes come in various colors, the technique also provides a means to get adjacent neurons labeled in multicolor. This tracing technique is therefore useful for studying neuronal morphogenesis and synaptic connectivity in the motor neuron system of Drosophila.

Retrograde Tracing of Drosophila Embryonic Motor Neurons Using Lipophilic Fluorescent Dyes

We describe a method for retrograde tracing of the Drosophila embryonic motor neurons using lipophilic fluorescent dyes.

We describe a technique for retrograde labeling of motor neurons in Drosophila. We use an oil-dissolved lipophilic dye and deliver a small droplet to an ...

Developmental Biology

Mass Histology to Quantify Neurodegeneration in Drosophila

Progressive neurodegenerative diseases like Alzheimer&#39;s disease (AD) or Parkinson&#39;s disease (PD) are an increasing threat to human health worldwide. Although mammalian models have provided important insights into the underlying mechanisms of pathogenicity, the complexity of mammalian systems together with their high costs are limiting their use. Therefore, the simple but well-established Drosophila model-system&#160;provides an alternative for investigating the molecular pathways that are affected in these diseases. Besides behavioral deficits, neurodegenerative diseases are characterized by histological phenotypes such as neuronal death and axonopathy. To quantify neuronal degeneration and to determine how it is affected by genetic and environmental factors, we use a histological approach that is based on measuring the vacuoles in adult fly brains. To minimize the effects of systematic error and to directly compare sections from control and experimental flies in one preparation, we use the &#39;collar&#39; method for paraffin sections. Neurodegeneration is then assessed by measuring the size and/or number of vacuoles that have developed in the fly brain. This can either be done by focusing on a specific region of interest or by analyzing the entire brain by obtaining serial sections that span the complete head. Therefore, this method allows one to measure not only severe degeneration but also relatively mild phenotypes that are only detectable in a few sections, as occurs during normal aging.

Mass Histology to Quantify Neurodegeneration in Drosophila

Drosophila is widely used as a model system to study neurodegeneration. This protocol describes a method by which degeneration, as determined by vacuole formation in the brain, can be quantified. It also minimizes effects due to the experimental procedure by processing and sectioning control and experimental flies as one sample.

Progressive neurodegenerative diseases like Alzheimer&#39;s disease (AD) or Parkinson&#39;s disease (PD) are an increasing threat to human health ...

A Drosophila In Vivo Injury Model for Studying Neuroregeneration in the Peripheral and Central Nervous System

The regrowth capacity of damaged neurons governs neuroregeneration and functional recovery after nervous system trauma. Over the past few decades, various intrinsic and extrinsic inhibitory factors involved in the restriction of axon regeneration have been identified. However, simply removing these inhibitory cues is insufficient for successful regeneration, indicating the existence of additional regulatory machinery. Drosophila melanogaster, the fruit fly, shares evolutionarily conserved genes and signaling pathways with vertebrates, including humans. Combining the powerful genetic toolbox of flies with two-photon laser axotomy/dendriotomy, we describe here the Drosophila sensory neuron &#8211; dendritic arborization (da) neuron injury model as a platform for systematically screening for novel regeneration regulators. Briefly, this paradigm includes a) the preparation of larvae, b) lesion induction to dendrite(s) or axon(s) using a two-photon laser, c) live confocal imaging post-injury and d) data analysis. Our model enables highly reproducible injury of single labeled neurons, axons, and dendrites of well-defined neuronal subtypes, in both the peripheral and central nervous system.

A Drosophila In Vivo Injury Model for Studying Neuroregeneration in the Peripheral and Central Nervous System

Here, we present a protocol using the Drosophila sensory neuron - dendritic arborization (da) neuron injury model, which combines in vivo live imaging, two-photon laser axotomy/dendriotomy, and the powerful fly genetic toolbox, as a platform for screening potential promoters and inhibitors of neuroregeneration.

The regrowth capacity of damaged neurons governs neuroregeneration and functional recovery after nervous system trauma. Over the past few decades, various ...

Medicine

Morphological and Functional Evaluation of Axons and their Synapses during Axon Death in Drosophila melanogaster

Axon degeneration is a shared feature in neurodegenerative disease and when nervous systems are challenged by mechanical or chemical forces. However, our understanding of the molecular mechanisms underlying axon degeneration remains limited. Injury-induced axon degeneration serves as a simple model to study how severed axons execute their own disassembly (axon death). Over recent years, an evolutionarily conserved axon death signaling cascade has been identified from flies to mammals, which is required for the separated axon to degenerate after injury. Conversely, attenuated axon death signaling results in morphological and functional preservation of severed axons and their synapses. Here, we present three simple and recently developed protocols that allow for the observation of axonal morphology, or axonal and synaptic function of severed axons that have been cut-off from the neuronal cell body, in the fruit fly Drosophila. Morphology can be observed in the wing, where a partial injury results in axon death side-by-side of uninjured control axons within the same nerve bundle. Alternatively, axonal morphology can also be observed in the brain, where the whole nerve bundle undergoes axon death triggered by antennal ablation. Functional preservation of severed axons and their synapses can be assessed by a simple optogenetic approach coupled with a post-synaptic grooming behavior. We present examples using a highwire loss-of-function mutation and by over-expressing dnmnat, both capable of delaying axon death for weeks to months. Importantly, these protocols can be used beyond injury; they facilitate the characterization of neuronal maintenance factors, axonal transport, and axonal mitochondria.

Morphological and Functional Evaluation of Axons and their Synapses during Axon Death in Drosophila melanogaster

Here, we provide protocols to perform three simple injury-induced axon degeneration (axon death) assays in Drosophila melanogaster to evaluate the morphological and functional preservation of severed axons and their synapses.

Axon degeneration is a shared feature in neurodegenerative disease and when nervous systems are challenged by mechanical or chemical forces. However, our ...

Visualizing Synaptic Degeneration in Adult Drosophila in Association with Neurodegeneration

Drosophila serves as a useful model for assessing synaptic structure and function associated with neurodegenerative diseases. While much work has focused on neuromuscular junctions (NMJs) in Drosophila larvae, assessing synaptic integrity in adult Drosophila has received much less attention. Here we provide a straightforward method for dissection of the dorsal longitudinal muscles (DLMs), which are required for flight ability. In addition to flight as a behavioral readout, this dissection allows for the both DLM synapses and muscle tissue to be amenable to structural analysis using fluorescently labeled antibodies for synaptic markers or proteins of interest. This protocol allows for the evaluation of the structural integrity of synapses in adult Drosophila during aging to model the progressive, age-dependent nature of most neurodegenerative diseases.

Visualizing Synaptic Degeneration in Adult Drosophila in Association with Neurodegeneration

The goal of this procedure is to dissect the dorsal longitudinal muscle (DLM) tissue to assess the structural integrity of DLM neuromuscular junctions (NMJs) in neurodegenerative disease models using Drosophila melanogaster.

Drosophila serves as a useful model for assessing synaptic structure and function associated with neurodegenerative diseases. While much work has focused ...

Assessing the Structural Integrity of the Dorsal Longitudinal Muscle Neuromuscular Junctions in Drosophila

Source: Sidisky, J. M., et al. <a href="https://app-jove-com.remotexs.ntu.edu.sg/v/61363">Visualizing Synaptic Degeneration in Adult Drosophila in Association with Neurodegeneration.</a> J. Vis. Exp. (2020).
This video demonstrates a protocol for assessing the structural integrity of neuromuscular junctions in the dorsal longitudinal muscles of Drosophila. The procedure involves staining neurons and muscles with two distinct antibodies and comparing fluorescence patterns between mutant and wild-type flies. A reduction in neuronal staining in mutant flies indicates neurodegeneration, while the muscle structure remains intact.

1. Flash freezing and thorax bisection

	Before beginning the bisections, fill a Dewar flask with liquid nitrogen wearing proper cryo-protective gloves ...

JoVE Encyclopedia of Experiments

Neuropathology

Neuromuscular Disorders

Two-Photon Laser-Induced Neural Injury: A Method to Observe Axon Degeneration and Regeneration in Drosophila Larvae

Source: Li, D., et al. <a href="https://www-jove-com.remotexs.ntu.edu.sg/video/57557/" target="_blank">A Drosophila In Vivo Injury Model for Studying Neuroregeneration in the Peripheral and Central Nervous System</a>. J. Vis. Exp. (2018).
This video describes two-photon laser ablation of axons in a Drosophila melanogaster larva and an example protocol to induce injury and image the injury site.

Source: Li, D., et al. A Drosophila In Vivo Injury Model for Studying Neuroregeneration in the Peripheral and Central Nervous System. J. Vis. Exp. 
...

Biology

Drosophila melanogaster (fruit fly)

Larva

Mechanically Injuring Drosophila Larvae Segmental Nerves to Induce Neurodegeneration

Source: Danella, E. B., et al. <a href="https://app-jove-com.remotexs.ntu.edu.sg/v/56128">A Simple Neuronal Mechanical Injury Methodology to Study Drosophila Motor Neuron Degeneration.</a> J. Vis. Exp. (2017).
The video demonstrates inducing neurodegeneration in Drosophila larva segmental nerves via mechanical injury. The ventral cuticle of anesthetized larvae is pinched using forceps to cause injury to the segmental nerves. The injured larvae are maintained with food, allowing the injury to cause degeneration of the motor neurons in the nerves, causing disruption of their neuromuscular junctions (NMJs).

1. Preparation of Reagents and Equipment 

	Prepare 1x Dissection Buffer (70 mM NaCl, 5 mM KCl, 0.02 mM CaCl2, 20 mM MgCl2, 10 mM NaHCO3, 115 mM sucrose, ...

A Simple Neuronal Mechanical Injury Methodology to Study Drosophila Motor Neuron Degeneration

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