This work was supported by a National Health &#38; Medical Research Centre (NHMRC) project grant to R.M.

All experimental procedures described here complied with the Animal Care and Ethics Committee of UNSW Australia and were performed in accordance with the National Health and Medical Research Council of Australia regulations for animal experimentation. All procedures in this protocol should be performed in accordance with the requirement of the relevant Animal Care and Ethics Committee.
1. Acetylcholinesterase Histochemical Staining
<ol>
	<li>Prepare the Acetylcholinesterase reaction mixture
	<ol>
		<li>Add 290 mg of Acetylthiocholine iodide to 200 ml of 0.1 M phosphate buffer (PB). Mix with a magnetic stirrer at 900 rpm.</li>
		<li>Add 600 mg of glycine under continuous stirring.</li>
		<li>Slowly add 420 mg of copper sulphate to the reaction mixture under continuous stirring until the product is completely dissolved.</li>
	</ol>
	</li>
	<li>Remove the skin on the animal carcass (obtained through tissue sharing) by making incisions into the skin of a perfused rat or mouse, grasping the skin from the neck area and pulling it past its feet. Ensure that the fascia covering each muscle is either removed or significantly perforated to ensure ample exposure of the muscle fibres to the reaction solution.</li>
	<li>Immerse the entire body or limb of interest into the reaction mixture and incubate O/N&#160;at 4&#160;&#176;C.</li>
	<li>Wash the carcass for 2 min in distilled water. Note: At this stage, the muscles exhibit a blue coloration and the motor end plates (MEPs) can be seen as white dots.</li>
	<li>Expose the carcass to a 10% ammonium sulphide solution for 3-5 sec. 
	Note: The muscle fibres will rapidly turn brown and the MEPs will be observable as black speckled dots. If the reaction occurs too quickly, and the muscle fibres are stained too dark to distinguish between the MEPs and the muscle fibres try using lower concentrations of ammonium sulphide solution (e.g., 5%). The reaction time to get the optimal contrast between the MEPs and the muscle fibres varies from one sample to the other. Therefore it is difficult to define the exact exposure time to the reagent. The reaction should be closely monitored and stopped when the contrast is deemed adequate.</li>
	<li>Wash the carcass two times, with agitation&#160;in distilled water and&#160;gently pat the carcass dry.</li>
	<li>Photograph both the lateral and medial aspects of the limb, ensuring that the MEPs for all the muscles of interest are captured.</li>
</ol>
2. Intramuscular Injections at the Motor End Plates
<ol>
	<li>Pull glass micropipettes with a micropipette puller (the use of graded micropipettes with plungers is recommended). With the help of a dissecting microscope, break the tips of the micropipettes with a pair of forceps such that the internal diameter of the lumen of the micropipette is approximately 0.5 mm.</li>
	<li>Ensure that all surgical instruments used are freshly autoclaved and that the surgical area is sterile.</li>
	<li>Fill the micropipettes with Fluoro-Gold (5% in distilled water).</li>
	<li>Induce anaesthetise in the animal in an induction chamber with Isofluorane (4% in O2). Check for righting reflex and ensure its absence before removing it from the induction chamber. Secure a nose cone over the snout of the rat and deliver Isofluorane (2% in O2) for maintenance of anaesthesia. Pinch the animal&#8217;s toes and gently touch the animal&#8217;s eye to ensure that both the pedal withdrawal and the corneal reflexes are absent. Note: A mixture of ketamine and xylazil can also be used (80&#160;and 10 mg/kg respectively, delivered intraperitoneally). Ketamine is a Schedule 8 (&#8220;Controlled&#8221;) drug and necessary protocols associated with the purchase, use, storage and disposal of the drug will have to be adhered to.</li>
	<li>Apply eye lubricant to prevent drying of the eyes during the course of the procedure.</li>
	<li>Shave the targeted limb and use gauze to wipe the shaved area with three alternating scrubs of chlorhexidine and 70% alcohol.&#160;&#160;Transfer the animal to the surgical area.</li>
	<li>Place the animal on a clean underpad and position it appropriately to ensure good access to the targeted muscle(s).</li>
	<li>Use a pair of forceps with tooth grips to lift the skin over the targeted muscle away from the underlying musculature and make an incision in the skin with surgical scissors. Ensure that the incision is large enough to completely expose the muscle(s) of interest. Ensure that there is minimal disruption to the fascia.</li>
	<li>Use the MEP photographs to mentally transpose the location and shape of the MEP region onto the muscle(s). 
	Note: A fine felt marker could assist to reproduce the MEP region from the photograph onto the muscle(s) of interest.</li>
	<li>Perform multiple injections along the full length of the MEP region (for Fluoro-Gold, 3 to 4 injections of 1-2 &#181;l each should be sufficient). Gently wipe the muscle(s) to remove any seepage.</li>
	<li>Bring the two ends of the incised skin close together with blunt forceps and close the wound with surgical clips. Infiltrate 0.1 ml Bupivacaine (0.5% in water) (or other local anaesthetics) along the entire span of the wound.</li>
	<li>Turn the anaesthetic machine off and monitor the animal until it has is fully recovered from anaesthesia.</li>
	<li>Wait for 14 days between administration of intra-muscular injections and the perfusion of the animals.</li>
</ol>
3. Perfusions
<ol>
	<li>Administer a lethal dose of pentobarbitone sodium solution (e.g. Lethabarb; 150 mg/kg) to the animal by intraperitoneal injection.
	<ol>
		<li>Closely monitor the animal until a deep level of anaesthesia is reached, as confirmed by the absence of the pedal withdrawal and the corneal reflexes.</li>
	</ol>
	</li>
	<li>Position the animal on its back on a dissecting board placed over a perfusion sink.</li>
	<li>Use a pair of forceps with tooth grips to lift the skin covering the base of the sternum. Make a small skin incision with a pair of strong surgical scissors immediately below the sternum and then use the forceps to grip the xiphoid cartilage of the sternum. While holding the xiphoid cartilage, enlarge the incision on both sides of the chest cavity, from the sternum to the armpits.</li>
	<li>Cut the diaphragm to expose the heart.
	<ol>
		<li>Inject 0.ml of heparin directly into the apex of the heart to prevent coagulation of the blood.</li>
		<li>Cut the apex to allow the insertion of a cannula into the left ventricle, and then quickly clamp the cannula in place with the aid of a haemostat.</li>
		<li>Make an incision in the right atrium with a pair of fine scissors and immediately start the peristaltic pump. Perfuse with 0.1 M PB until the liquid flowing out of the atrium is nearly free of blood and the color of the liver becomes light brown. Then, perfuse with a solution of paraformaldehyde (4% in 0.1 M PB) until the entire body of the animal becomes rigid.</li>
	</ol>
	</li>
</ol>
4. Cervical Spinal Cord Dissection and Preparation for Histology
<ol>
	<li>Lay the animal carcass on its abdomen.</li>
	<li>Cut the skin at the body&#8217;s midline with a scalpel and reflect it from the base of the skull to the level of the iliac bone.</li>
	<li>Cut through and reflect the paravertebral muscles to expose the dorsal aspect of the vertebral column.</li>
	<li>Identify the bony spinous process of Atlas, the second cervical segment (i.e., C2), and remove it with a pair of surgical rongeurs or forceps to locate the corresponding underlying dorsal root.
	<ol>
		<li>Identify the right C2 root by coloring it with a permanent felt marker.</li>
		<li>Remove the next vertebrae one by one and mark the right dorsal roots with alternating colors (i.e., C2, C4, C6, and C8 can be colored in green and C3, C5, C7, T1 can be colored in blue).</li>
	</ol>
	</li>
	<li>Use a small surgical needle (e.g., 30 G gauge needle) to gently pierce through the dura covering the lower end of the spinal cord. With the bevel of the needle facing up, lift the dura away from the cord while moving the needle rostrally to make a longitudinal slit.
	<ol>
		<li>Reflect the dura.</li>
	</ol>
	</li>
	<li>Cut the spinal cord transversally into one- or two-segment blocks with a new scalpel blade.
	<ol>
		<li>Leave the spinal cord segments in situ and, for each block, carefully make a small fiducial mark on the left side of each block with the scalpel blade half way between two adjacent roots. Ensure that the fiducial mark is deep enough through the tissue as to be visible from the ventral aspect of the blocks. Make the fiducial mark at an angle of approximately 45&#176;, pointing either anteriorly or posteriorly with respect to animal anatomy, to aid in the orientation of the tissue segment following dissection.</li>
	</ol>
	</li>
	<li>Collect the individual blocks into small, clearly labelled bottles containing a solution of paraformaldehyde (4% in 0.1 M PB) and leave at RT O/N.</li>
	<li>Transfer the blocks into clean, clearly labelled bottles containing a solution of sucrose (30% in 0.1 M PB) and keep at 4 &#176;C for at least two days.</li>
	<li>Place the segments in cryo-moulds and covered them with tissue freezing medium. For longitudinal histological preparation, orient the blocks with the dorsal aspect facing up and use the fiducial mark to orient the block in the cryo-moulds.</li>
	<li>Freeze the cryo-moulds at -20&#160;&#176;C and cut with a cryostat in 50 &#181;m-thick sections. Note: The sections can be directly mounted on adhesion microscope slides and left to dry O/N. Alternatively, the sections can be floated in 48-well plates filled with 0.1 M PB and subsequently mounted using the fiducial mark to orient the tissue sections on the slides.</li>
</ol>
5. Lumbar Spinal Cord Dissection and Preparation for Histology
<ol>
	<li>Lay the animal carcass on it&#8217;s back.</li>
	<li>Perform a midline incision along the abdomen of the animal and remove the viscera. Dissect out the muscles of the posterior abdominal wall to expose the ventral aspect of the vertebral column.</li>
	<li>Locate the short caudal-most rib and its adjoining T13 vertebra where the T13 ventral root exits the bone.
	<ol>
		<li>Consecutively remove one by one the two or three vertebrae rostral to T13 (i.e., T12, T11 and, if needed, T10) with fine surgical rongeurs to follow the T13 ventral root until its point of entry in the ventral aspect of the ventral cord and mark it with a permanent felt marker.</li>
		<li>From this point on, repeat the same procedure to identify the location of the ventral root entry points for L1, L2, L3, L4, L5, L6 and S1, coloring them with alternating colors.</li>
	</ol>
	</li>
	<li>Follow the same procedure as described in Section 4.5-4.10 for lumbar spinal cord dissection.</li>
</ol>

<ol>
	<li>Kaspar, B. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retrograde+Viral+Delivery+of+IGF-1+Prolongs+Survival+in+a+Mouse+ALS+Model.">Retrograde Viral Delivery of IGF-1 Prolongs Survival in a Mouse ALS Model.</a> Science. 301 (5634), (2003).</li><li>Ishiyama, T., Okada, R., Nishibe, H., Mitsumoto, H., Nakayama, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Riluzole+slows+the+progression+of+neuromuscular+dysfunction+in+the+wobbler+mouse+motor+neuron+disease.">Riluzole slows the progression of neuromuscular dysfunction in the wobbler mouse motor neuron disease.</a> Brain Res. 1019 (1-2), 226-236 (2004).</li><li>Turner, B. J., Parkinson, N. J., Davies, K. E., Talbot, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Survival+motor+neuron+deficiency+enhances+progression+in+an+amyotrophic+lateral+sclerosis+mouse+model.">Survival motor neuron deficiency enhances progression in an amyotrophic lateral sclerosis mouse model.</a> Neurobiol Dis. 34 (3), 511-517 (2009).</li><li>Wegorzewska, I., Bell, S., Cairns, N. J., Miller, T. M., Baloh, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TDP-43+mutant+transgenic+mice+develop+features+of+ALS+and+frontotemporal+lobar+degeneration.">TDP-43 mutant transgenic mice develop features of ALS and frontotemporal lobar degeneration.</a> P Natl Acad Sci USA. 106 (44), 18809-18814 (2009).</li><li>Kimura, E., Li, S., Gregorevic, P., Fall, B. M., Chamberlain, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dystrophin+delivery+to+muscles+of+mdx+mice+using+lentiviral+vectors+leads+to+myogenic+progenitor+targeting+and+stable+gene+expression.">Dystrophin delivery to muscles of mdx mice using lentiviral vectors leads to myogenic progenitor targeting and stable gene expression.</a> Mol Ther. 18 (1), 206-213 (2009).</li><li>Van Den Bosch, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+rodent+models+of+amyotrophic+lateral+sclerosis.">Genetic rodent models of amyotrophic lateral sclerosis.</a> J Biomed Biotechnol. 2011 (6), 348765–11 (2011).</li><li>Pratt, S. J. P., Shah, S. B., Ward, C. W., Inacio, M. P., Stains, J. P., Lovering, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+in+vivo+injury+on+the+neuromuscular+junction+in+healthy+and+dystrophic+muscles.">Effects of in vivo injury on the neuromuscular junction in healthy and dystrophic muscles.</a> J Physiol. 591 (Pt 2), 559-570 (2013).</li><li>Garrett, C. 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=DYNC1H1+mutation+alters+transport+kinetics+and+ERK1/2-cFos+signalling+in+a+mouse+model+of+distal+spinal+muscular+atrophy).">DYNC1H1 mutation alters transport kinetics and ERK1/2-cFos signalling in a mouse model of distal spinal muscular atrophy).</a> Brain. 137 (Pt 7), 1883-1893 (2014).</li><li>Bordet, T., 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=Protective+effects+of+cardiotrophin-1+adenoviral+gene+transfer+on+neuromuscular+degeneration+in+transgenic+ALS+mice).">Protective effects of cardiotrophin-1 adenoviral gene transfer on neuromuscular degeneration in transgenic ALS mice).</a> Hum Mol Gen. 10 (18), 1925-1933 (2001).</li><li>Acsadi, G., 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=Increased+survival+and+function+of+SOD1+mice+after+glial+cell-derived+neurotrophic+factor+gene+therapy.">Increased survival and function of SOD1 mice after glial cell-derived neurotrophic factor gene therapy.</a> Hum Gene Ther. 13 (9), 1047-1059 (2002).</li><li>Azzouz, M., 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=VEGF+delivery+with+retrogradely+transported+lentivector+prolongs+survival+in+a+mouse+ALS+model.">VEGF delivery with retrogradely transported lentivector prolongs survival in a mouse ALS model.</a> Nature. 429 (6990), 413-417 (2004).</li><li>Suzuki, M., 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=Direct+muscle+delivery+of+GDNF+with+human+mesenchymal+stem+cells+improves+motor+neuron+survival+and+function+in+a+rat+model+of+familial+ALS.">Direct muscle delivery of GDNF with human mesenchymal stem cells improves motor neuron survival and function in a rat model of familial ALS.</a> Mol Ther. 16 (12), 2002-2010 (2008).</li><li>Benkhelifa-Ziyyat, 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=Intramuscular+scAAV9-SMN+Injection+Mediates+Widespread+Gene+Delivery+to+the+Spinal+Cord+and+Decreases+Disease+Severity+in+SMA+Mice.">Intramuscular scAAV9-SMN Injection Mediates Widespread Gene Delivery to the Spinal Cord and Decreases Disease Severity in SMA Mice.</a> Mol Ther. 21 (2), 282-290 (2013).</li><li>Azzouz, M., Hottinger, A., Paterna, J. C., Zurn, A. D., Aebischer, P., B&#252;eler, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+motoneuron+survival+and+improved+neuromuscular+function+in+transgenic+ALS+mice+after+intraspinal+injection+of+an+adeno-associated+virus+encoding+Bcl-2.">Increased motoneuron survival and improved neuromuscular function in transgenic ALS mice after intraspinal injection of an adeno-associated virus encoding Bcl-2.</a> Hum Mol Gen. 9 (5), (2000).</li><li>Lepore, A. C., Haenggeli, C., 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=Intraparenchymal+spinal+cord+delivery+of+adeno-associated+virus+IGF-1+is+protective+in+the+SOD1G93A+model+of+ALS.">Intraparenchymal spinal cord delivery of adeno-associated virus IGF-1 is protective in the SOD1G93A model of ALS.</a> Brain Res. 1185, 256-265 (2007).</li><li>Schnapp, B. J., Reese, T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynein+is+the+motor+for+retrograde+axonal+transport+of+organelles.">Dynein is the motor for retrograde axonal transport of organelles.</a> Proc Natl Acad Sci USA. 86 (5), 1548-1552 (1989).</li><li>Vale, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Molecular+Motor+Toolbox+for+Intracellular+Transport.">The Molecular Motor Toolbox for Intracellular Transport.</a> Cell. 112 (4), 467-480 (2003).</li><li>Schiavo, G., Fainzilber, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+biology:+Alternative+energy+for+neuronal+motors.">Cell biology: Alternative energy for neuronal motors.</a> Nature. 495 (7440), 178-180 (2013).</li><li>Gracies, J. -. M., Lugassy, M., Weisz, D. J., Vecchio, M., Flanagan, S., Simpson, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Botulinum+Toxin+Dilution+and+Endplate+Targeting+in+Spasticity.+A+Double-Blind+Controlled+Study.">Botulinum Toxin Dilution and Endplate Targeting in Spasticity. A Double-Blind Controlled Study.</a> Arch Phys Med Rehabil. 90 (1), 9-16 (2009).</li><li>Van Campenhout, A., Molenaers, G. <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+the+motor+endplate+zone+in+human+skeletal+muscles+of+the+lower+limb:+anatomical+guidelines+for+injection+with+botulinum+toxin.">Localization of the motor endplate zone in human skeletal muscles of the lower limb: anatomical guidelines for injection with botulinum toxin.</a> Dev Med Child Neurol. 53 (2), 108-119 (2011).</li><li>Tosolini, A. P., Morris, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+characterization+of+the+motor+neuron+columns+supplying+the+rat+forelimb.">Spatial characterization of the motor neuron columns supplying the rat forelimb.</a> Neuroscience. 200, 19-30 (2012).</li><li>Tosolini, A. P., Mohan, R., Morris, R. <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+full+length+of+the+motor+end+plate+regions+in+the+mouse+forelimb+increases+the+uptake+of+fluoro-gold+into+corresponding+spinal+cord+motor+neurons.">Targeting the full length of the motor end plate regions in the mouse forelimb increases the uptake of fluoro-gold into corresponding spinal cord motor neurons.</a> Front Neurol. 4, 58 (2013).</li><li>Mohan, R., Tosolini, A. P., Morris, R. <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+motor+end+plates+in+the+mouse+hindlimb+gives+access+to+a+greater+number+of+spinal+cord+motor+neurons:+an+approach+to+maximize+retrograde+transport.">Targeting the motor end plates in the mouse hindlimb gives access to a greater number of spinal cord motor neurons: an approach to maximize retrograde transport.</a> Neuroscience. 274, 318-330 (2014).</li><li>Baumgartner, B. J., Shine, H. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuroprotection+of+spinal+motoneurons+following+targeted+transduction+with+an+adenoviral+vector+carrying+the+gene+for+glial+cell+line-derived+neurotrophic+factor.">Neuroprotection of spinal motoneurons following targeted transduction with an adenoviral vector carrying the gene for glial cell line-derived neurotrophic factor.</a> Exp Neurol. 153 (1), 102-112 (1998).</li><li>Gransee, H. M., Zhan, W. -. Z., Sieck, G. C., Mantilla, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeted+delivery+of+TrkB+receptor+to+phrenic+motoneurons+enhances+functional+recovery+of+rhythmic+phrenic+activity+after+cervical+spinal+hemisection.">Targeted delivery of TrkB receptor to phrenic motoneurons enhances functional recovery of rhythmic phrenic activity after cervical spinal hemisection.</a> PLoS ONE. 8 (5), e64755 (2013).</li></ol>

The authors declare that they have no competing financial interests.

Intramuscular targeting and subsequent retrograde transfer of therapeutic transgenes to the corresponding &#945; motor neurons for the experimental treatment of neuromuscular condition is not a new strategy. For instance, this delivery method has been used to delay neuromuscular degeneration at different stages of the ALS progression in SOD1 mice and rats 1,9-12 as well as in mice with SMA 13. Whilst promising, the efficacy of these gene therapy scenarios has been limited. In this regard, we propose...

The loss of control of voluntary movement that results from neurological conditions such as motor neuron disease and spinal- as well as Duchenne muscular atrophy is a debilitating condition that has high and long lasting impact on the every day life of affected individuals. Over the last decade, research efforts aiming to stop or at least delay the deleterious effects of these neuromuscular diseases has been a priority for many clinicians and scientist around the world. In this regard, the recent generation of animal models that mimic these neuromuscular diseases has been instrumental in obtaining fundamental insights into the physiological mechanisms underlying the development and progression of these conditions 1-13. Treatment of these neuromuscular disease requires direct access to the spinal cord and can be achieved by spinal cord injections 14,15. Recent advances in gene therapy have also targeted the striated muscles of the upper and lower limbs to shuttle therapeutic genes to the corresponding &#945; motor neurons that are located within the ventral horn of the spinal cord 1,9-13. However, this once promising strategy has failed to improve the outcome of these neurological conditions. While it is fair to conclude that these poor outcomes could be, at least partly, be attributable to the low efficacy of these protective genes, one cannot exclude the low efficacy of these gene delivery methods.
Motor end plates (MEPs) are specialized regions of the skeletal myofibres that are indented by the axon terminals of large peripheral motor fibres originating from &#945; motor neurons. Together, the peripheral nerve fibre endings and the MEPs form the neuromuscular junction, i.e., the site where synaptic impulses are triggered by the anterograde release of the neurotransmitter, acetylcholine. Importantly, the relationship between peripheral nerve fibres and the MEPs is bi-directional, although different motors are responsible for the transport of molecules and organelles towards as well as away from the neuron somata 16-18. In light of these anatomical considerations, MEPs appear to be the targets of choice for the delivery and subsequent retrograde transport of genetic material to the corresponding motor neurons. In this context, it is not surprising that the success of motor neuron transduction greatly depends on the distance between the intramuscular injection of viral vectors and the muscle&#8217;s MEPs 19-20. Surprisingly, however, the exact location of the MEP zones on the myofibres of the laboratory rat and mouse, the two species of choice to model neuromuscular diseases, were not available until recently.
We have produced comprehensive maps of the MEP region for several forelimb muscles in the rat and the mouse 21-22. More recently, we have shown the details of the organization of the MEP region for several muscles of the mouse hindlimb 23 and we are currently analysing the features of the MEPs on the rat hindlimb. In our hands, intramuscular injections of retrograde tracers directed to the entire MEP zones in these muscles gave rise to more labelled motor neurons that are spanning more spinal cord segments than previously reported. Here we present the protocol that has been developed over the last few years to reveal the location of the MEPs on the external surface as well as throughout the depth of hindlimb and forelimb muscles in both the mouse and the rat.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Fluoro-Gold</td>
			<td>Fluorochrome, LLC</td>
			<td>Nil</td>
			<td>Diluted to 5%</td>
		</tr>
		<tr>
			<td>Drummond PCR Micropipets 1-10&#181;l</td>
			<td>Drummond Scientific</td>
			<td>5-000-1001-X10</td>
			<td>accompanied with plungers</td>
		</tr>
		<tr>
			<td>Acetylthiocholine Iodide</td>
			<td>Sigma Life Science</td>
			<td>A5751-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>Copper(II) Sulfate Anhydrous</td>
			<td>Sigma-Aldrich</td>
			<td>61230-500G-F</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue-Tek O.C.T Compound</td>
			<td>Sakura Finetek</td>
			<td>25608-930</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Ajax Finechem</td>
			<td>1083-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextran, Tetramethylrhodamine and biotin</td>
			<td>Life Technologies</td>
			<td>D-3312</td>
			<td>Diliuted in distilled water</td>
		</tr>
		<tr>
			<td>Isothesia</td>
			<td>Provet</td>
			<td>ISOF00</td>
			<td>1000mg/g Isoflurane inhalation vapour</td>
		</tr>
		<tr>
			<td>Autoclip 9mm Wound Clips</td>
			<td>Texas Scientific Instruments, LLC</td>
			<td align="right">205016</td>
			<td></td>
		</tr>
		<tr>
			<td>Lethabarb Enthanasia Injection</td>
			<td>Virbac (Australia) Pty Ltd.</td>
			<td>LETHA450</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde Solution</td>
			<td>Ajax Finechem</td>
			<td>A809-2.5L PL</td>
			<td></td>
		</tr>
		<tr>
			<td>SuperFrost Plus glass slides</td>
			<td>Menzel-Glaser</td>
			<td>J1800AMNZ</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium Sulphide</td>
			<td>Sigma-Aldrich</td>
			<td>A1952</td>
			<td>Diluted to 10%</td>
		</tr>
		<tr>
			<td>Marcain Spinal 0.5% (Bupivacaine hydrochloride)</td>
			<td>Astrazenca</td>
			<td></td>
			<td>Diluted to 0.25%</td>
		</tr>
	</tbody>
</table>

intramuscular injections along the motor end plates: a minimally invasive approach to shuttle tracers directly into motor neurons

Diseases affecting the integrity of spinal cord motor neurons are amongst the most debilitating neurological conditions. Over the last decades, the development of several animal models of these neuromuscular disorders has provided the scientific community with different therapeutic scenarios aimed at delaying or reversing the progression of these conditions. By taking advantage of the retrograde machinery of neurons, one of these approaches has been to target skeletal muscles in order to shuttle therapeutic genes into corresponding spinal cord motor neurons. Although once promising, the success of such gene delivery approach has been hampered by the sub-optimal number of transduced motor neurons it has so far shown to yield. Motor end plates (MEPs) are highly specialized regions on the skeletal musculature that are in direct synaptic contact to the spinal cord &#945; motor neurons. In this regard, it is important to note that, so far, the efforts to retrogradely transfer genes into motor neurons were made without reference to the location of the MEP region in the targeted muscles. Here, we describe a simple protocol 1) to reveal the exact location of the MEPs on the surface of skeletal muscles and 2) to use this information to guide the intramuscular delivery and subsequent optimal retrograde transport of retrograde tracers into motor neurons. We hope to utilize the results from these tracing experiments in further studies into investigating retrograde transport of therapeutic genes to spinal cord motor neurons through the targeting of MEPs.

Acetylcholinesterase histochemical staining reveals the location of the motor end plates across the width of the muscles. Figure 1 illustrates the results of such staining performed on a whole rat forelimb. It is suggested to optimise the concentration of the ammonium sulphide solution (e.g., 5-7% instead of 10%) as well as the time the specimen is immersed in the solution if the non-specific background staining on the muscles fibres is too excessive. Figure 2 illustrates a colu...

Watch this Scientific Journal Video about Intramuscular Injections Along the Motor End Plates: A Minimally Invasive Approach to Shuttle Tracers Directly into Motor Neurons at JoVE.com

Intramuscular Injections Along the Motor End Plates: A Minimally Invasive Approach to Shuttle Tracers Directly into Motor Neurons

The efficacy of intramuscular uptake and retrograde transport of molecules to corresponding motor neurons depends on the location of the injection sites with respect to the motor end plates (MEPs). Here, we describe how to locate MEPs on skeletal muscles to optimise retrograde transport of tracers into motor neurons.

Diseases affecting the integrity of spinal cord motor neurons are amongst the most debilitating neurological conditions. Over the last decades, the ...

intramuscular-injections-along-motor-end-plates-minimally-invasive

Research

JoVE Journal

Neuroscience

12.5K Views.  University of New South Wales. The efficacy of intramuscular uptake and retrograde transport of molecules to corresponding motor neurons depends on the location of the injection sites with respect to the motor end plates (MEPs). Here, we describe how to locate MEPs on skeletal muscles to optimise retrograde transport of tracers into motor neurons.

Video: Intramuscular Injections Along the Motor End Plates: A Minimally Invasive Approach to Shuttle Tracers Directly into Motor Neurons

Extracellularly Identifying Motor Neurons for a Muscle Motor Pool in Aplysia californica

In animals with large identified neurons (e.g. mollusks), analysis of motor pools is done using intracellular techniques1,2,3,4. Recently, we developed a technique to extracellularly stimulate and record individual neurons in Aplysia californica5. We now describe a protocol for using this technique to uniquely identify and characterize motor neurons within a motor pool.
This extracellular technique has advantages. First, extracellular electrodes can stimulate and record neurons through the sheath5, so it does not need to be removed. Thus, neurons will be healthier in extracellular experiments than in intracellular ones. Second, if ganglia are rotated by appropriate pinning of the sheath, extracellular electrodes can access neurons on both sides of the ganglion, which makes it easier and more efficient to identify multiple neurons in the same preparation. Third, extracellular electrodes do not need to penetrate cells, and thus can be easily moved back and forth among neurons, causing less damage to them. This is especially useful when one tries to record multiple neurons during repeating motor patterns that may only persist for minutes. Fourth, extracellular electrodes are more flexible than intracellular ones during muscle movements. Intracellular electrodes may pull out and damage neurons during muscle contractions. In contrast, since extracellular electrodes are gently pressed onto the sheath above neurons, they usually stay above the same neuron during muscle contractions, and thus can be used in more intact preparations.
To uniquely identify motor neurons for a motor pool (in particular, the I1/I3 muscle in Aplysia) using extracellular electrodes, one can use features that do not require intracellular measurements as criteria: soma size and location, axonal projection, and muscle innervation4,6,7. For the particular motor pool used to illustrate the technique, we recorded from buccal nerves 2 and 3 to measure axonal projections, and measured the contraction forces of the I1/I3 muscle to determine the pattern of muscle innervation for the individual motor neurons.
We demonstrate the complete process of first identifying motor neurons using muscle innervation, then characterizing their timing during motor patterns, creating a simplified diagnostic method for rapid identification. The simplified and more rapid diagnostic method is superior for more intact preparations, e.g. in the suspended buccal mass preparation8 or in vivo9. This process can also be applied in other motor pools10,11,12 in Aplysia or in other animal systems2,3,13,14.

Extracellularly Identifying Motor Neurons for a Muscle Motor Pool in Aplysia californica

In animals with large identified neurons (e.g. mollusks), analysis of motor pools is done using intracellular techniques1,2,3,4. Recently, we developed a technique to extracellularly stimulate and record individual neurons in Aplysia californica5. We now describe a protocol for using this technique to uniquely identify and characterize motor neurons within a motor pool.

In animals with large  identified neurons (e.g. mollusks), analysis of motor pools is done using  intracellular techniques1,2,3,4. Recently,  we developed ...

Minimally-invasive Technique for Injection into Rat Optic Nerve

The rat optic nerve is a useful model for stem cell regeneration research. Direct injection into the rat optic nerve allows delivery into the central nervous system in a minimally-invasive surgery without bone removal. This technique describes an approach to visualization and direct injection of the optic nerve following minor fascial dissection from the orbital ridge, using a conjunctival traction suture to gently pull the eye down and out. Representative examples of an injected optic nerve show successful injection of dyed beads.

Direct injection into the rat optic nerve is useful for regenerative research. We demonstrate a minimally-invasive technique for direct injection into a rat optic nerve that does not involve opening the skull. Using this method, surgical complications are minimized and recovery is more rapid.

The rat optic nerve is a useful model for stem cell regeneration research. Direct injection into the rat optic nerve allows delivery into the central ...

Why Quantification Matters: Characterization of Phenotypes at the Drosophila Larval Neuromuscular Junction

Most studies on morphogenesis rely on qualitative descriptions of how anatomical traits are affected by the disruption of specific genes and genetic pathways. Quantitative descriptions are rarely performed, although genetic manipulations produce a range of phenotypic effects and variations are observed even among individuals within control groups.&#160;Emerging evidence shows that morphology, size and location of organelles play a previously underappreciated, yet fundamental role in cell function and survival. Here we provide step-by-step instructions for performing quantitative analyses of phenotypes at the Drosophila larval neuromuscular junction (NMJ). We use several reliable immuno-histochemical markers combined with bio-imaging techniques and morphometric analyses to examine the effects of genetic mutations on specific cellular processes. In particular, we focus on the quantitative analysis of phenotypes affecting morphology, size and position of nuclei within the striated muscles of Drosophila larvae. The Drosophila larval NMJ is a valuable experimental model to investigate the molecular mechanisms underlying the structure and the function of the neuromuscular system, both in health and disease. However, the methodologies we describe here can be extended to other systems as well.

Why Quantification Matters: Characterization of Phenotypes at the Drosophila Larval Neuromuscular Junction

Morphology, size and location of intracellular organelles are evolutionarily conserved and appear to directly affect their function. Understanding the molecular mechanisms underlying these processes has become an important goal of modern biology. Here we show how these studies can be facilitated by the application of quantitative techniques.

Most studies on morphogenesis rely on qualitative descriptions of how anatomical traits are affected by the disruption of specific genes and genetic ...

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 ...

Endoscopic Endonasal Trans-sphenoidal Approach: Minimally Invasive Surgery for Pituitary Adenomas

Endoscopic endonasal trans-sphenoidal surgery has become the gold standard for the surgical treatment of pituitary adenomas and many other pituitary lesions. Refinements in surgical techniques, technological advancements, and incorporation of neuronavigation have rendered this surgery minimally invasive. The complication rates of this surgery are very low while excellent results are consistently obtained through this approach.
This paper focuses on the step-by-step surgical approach to pituitary adenomas, which is based on personal experience, and details the results obtained with this minimally invasive surgery.

The aim of this paper is to describe the different steps of the endoscopic endonasal approach to the sella turcica.

Endoscopic endonasal trans-sphenoidal surgery has become the gold standard for the surgical treatment of pituitary adenomas and many other pituitary ...

Retrograde Neuroanatomical Tracing of Phrenic Motor Neurons in Mice

Phrenic motor neurons are cervical motor neurons originating from C3 to C6 levels in most mammalian species. Axonal projections converge into phrenic nerves innervating the respiratory diaphragm. In spinal cord slices, phrenic motor neurons cannot be identified from other motor neurons on morphological or biochemical criteria. We provide the description of procedures for visualizing phrenic motor neuron cell bodies in mice, following intrapleural injections of cholera toxin subunit beta (CTB) conjugated to a fluorophore. This fluorescent neuroanatomical tracer has the ability to be caught up at the diaphragm neuromuscular junction, be carried retrogradely along the phrenic axons and reach the phrenic cell bodies. Two methodological approaches of intrapleural CTB delivery are compared: transdiaphragmatic versus transthoracic injections. Both approaches are successful and result in similar number of CTB-labeled phrenic motor neurons. In conclusion, these techniques can be applied to visualize or quantify the phrenic motor neurons in various experimental studies such as those focused on the diaphragm-phrenic circuitry.

Here, we describe a protocol for identifying phrenic motor neurons in mice after intrapleural delivery of fluorophore conjugated cholera toxin subunit beta. Two techniques are compared to inject the pleural cavity: transdiaphragmatic versus transthoracic approaches.

Phrenic motor neurons are cervical motor neurons originating from C3 to C6 levels in most mammalian species. Axonal projections converge into phrenic ...

Conversion of Human Induced Pluripotent Stem Cells (iPSCs) into Functional Spinal and Cranial Motor Neurons Using PiggyBac Vectors

We describe here a method to obtain functional spinal and cranial motor neurons from human induced pluripotent stem cells (iPSCs). Direct conversion into motor neuron is obtained by ectopic expression of alternative modules of transcription factors, namely Ngn2, Isl1 and Lhx3 (NIL) or Ngn2, Isl1 and Phox2a (NIP). NIL and NIP specify, respectively, spinal and cranial motor neuron identity. Our protocol starts with the generation of modified iPSC lines in which NIL or NIP are stably integrated in the genome via a piggyBac transposon vector. Expression of the transgenes is then induced by doxycycline and leads, in 5 days, to the conversion of iPSCs into MN progenitors. Subsequent maturation, for 7 days, leads to homogeneous populations of spinal or cranial MNs. Our method holds several advantages over previous protocols: it is extremely rapid and simplified; it does not require viral infection or further MN isolation; it allows generating different MN subpopulations (spinal and cranial) with a remarkable degree of maturation, as demonstrated by the ability to fire trains of action potentials. Moreover, a large number of motor neurons can be obtained without purification from mixed populations. iPSC-derived spinal and cranial motor neurons can be used for in vitro modeling of Amyotrophic Lateral Sclerosis and other neurodegenerative diseases of the motor neuron. Homogeneous motor neuron populations might represent an important resource for cell type specific drug screenings.

Conversion of Human Induced Pluripotent Stem Cells iPSCs into Functional Spinal and Cranial Motor Neurons Using PiggyBac Vectors

This protocol allows rapid and efficient conversion of induced pluripotent stem cells into motor neurons with a spinal or cranial identity, by ectopic expression of transcription factors from inducible piggyBac vectors.

We describe here a method to obtain functional spinal and cranial motor neurons from human induced pluripotent stem cells (iPSCs). Direct conversion into ...

Non-Invasive Modulation and Robotic Mapping of Motor Cortex in the Developing Brain

Mapping the motor cortex with transcranial magnetic stimulation (TMS) has potential to interrogate motor cortex physiology and plasticity but carries unique challenges in children. Similarly, transcranial direct current stimulation (tDCS) can improve motor learning in adults but has only recently been applied to children. The use of tDCS and emerging techniques like high&#8211;definition tDCS (HD-tDCS) require special methodological considerations in the developing brain. Robotic TMS motor mapping may confer unique advantages for mapping, particularly in the developing brain. Here, we aim to provide a practical, standardized approach for two integrated methods capable of simultaneously exploring motor cortex modulation and motor maps in children. First, we describe a protocol for robotic TMS motor mapping. Individualized, MRI-navigated 12x12 grids centered on the motor cortex guide a robot to administer single-pulse TMS. Mean motor evoked potential (MEP) amplitudes per grid point are used to generate 3D motor maps of individual hand muscles with outcomes including map area, volume, and center of gravity. Tools to measure safety and tolerability of both methods are also included. Second, we describe the application of both tDCS and HD-tDCS to modulate the motor cortex and motor learning. An experimental training paradigm and sample results are described. These methods will advance the application of non-invasive brain stimulation in children.

We demonstrate protocols for the modulation (tDCS, HD-tDCS) and mapping (robotic TMS) of the motor cortex in children.

Mapping the motor cortex with transcranial magnetic stimulation (TMS) has potential to interrogate motor cortex physiology and plasticity but carries ...

3D Kinematic Analysis for the Functional Evaluation in the Rat Model of Sciatic Nerve Crush Injury

Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of sciatic nerve injury rodent models. In this protocol, we describe a novel kinematic analysis method that uses a three-dimensional (3D) motion capture apparatus for functional evaluations using a rat sciatic nerve crush injury model. First, the rat is familiarized with treadmill walking. Markers are then attached to the designated bone landmarks and the rat is made to walk on the treadmill at the desired speed. Meanwhile, the posterior limb movements of the rat are recorded using four cameras. Depending on the software used, marker tracings are created using both automatic and manual modes and the desired data are produced after subtle adjustments. This method of kinematic analysis, which uses a 3D motion capture apparatus, offers numerous advantages, including superior precision and accuracy. Many more parameters can be investigated during the comprehensive functional evaluations. This method has several shortcomings that require consideration: The system is expensive, can be complicated to operate, and may produce data deviations due to skin shifting. Nevertheless, kinematic analysis using a 3D motion capture apparatus is useful for performing functional anterior and posterior limb evaluations. In the future, this method may become increasingly useful for generating accurate assessments of various traumas and diseases.

We introduce a kinematic analysis method that uses a three-dimensional motion capture apparatus containing four cameras and data processing software for performing functional evaluations during fundamental research involving rodent models.

Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of ...

Three-Dimensional Motor Nerve Organoid Generation

A fascicle of axons is one of the major structural motifs observed in the nervous system. Disruption of axon fascicles could cause developmental and neurodegenerative diseases. Although numerous studies of axons have been conducted, our understanding of formation and dysfunction of axon fascicles is still limited due to the lack of robust three-dimensional in vitro models. Here, we describe a step-by-step protocol for the rapid generation of a motor nerve organoid (MNO) from human induced pluripotent stem (iPS) cells in a microfluidic-based tissue culture chip. First, fabrication of chips used for the method is described. From human iPS cells, a motor neuron spheroid (MNS) is formed. Next, the differentiated MNS is transferred into the chip. Thereafter, axons spontaneously grow out of the spheroid and assemble into a fascicle within a microchannel equipped in the chip, which generates an MNO tissue carrying a bundle of axons extended from the spheroid. For the downstream analysis, MNOs can be taken out of the chip to be fixed for morphological analyses or dissected for biochemical analyses, as well as calcium imaging and multi-electrode array recordings. MNOs generated with this protocol can facilitate drug testing and screening and can contribute to understanding of mechanisms underlying development and diseases of axon fascicles.

This protocol provides a comprehensive procedure to fabricate human iPS cell-derived motor nerve organoid through spontaneous assembly of a robust bundle of axons extended from a spheroid in a tissue culture chip.

A fascicle of axons is one of the major structural motifs observed in the nervous system. Disruption of axon fascicles could cause developmental and ...