Name: ex vivo imaging of cell-specific calcium signaling at the tripartite synapse of the mouse diaphragm
Uploaded: 2018-10-04T14:00:00
Description: Watch this Scientific Journal Video about Ex Vivo Imaging of Cell-specific Calcium Signaling at the Tripartite Synapse of the Mouse Diaphragm at JoVE.com

This work was supported with funds from the National Institutes of Health (NIH) GM103554 and GM110767 to (T.W.G.) and from the National Center for Research Resources 5P20RR018751 and the National Institute of General Medical Sciences 8P20 GM103513 (to G.W.H.).

Animal husbandry and experiments were performed in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals and the IACUC at the University of Nevada.
1. Preparation of the Diaphragms and Phrenic Nerves from Transgenic Mice
<ol>
	<li>Purchase transgenic mice and oligonucleotide primers to genotype these mice. 
	Note: The primers are listed on the &#8220;Information&#8221; page for each of these mice.
	<ol>
		<li>Breed a 3- to 6-month-old mouse e...

<ol>
	<li>Sanes, J. R., Lichtman, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+the+vertebrate+neuromuscular+junction.">Development of the vertebrate neuromuscular junction.</a> Annual Review of Neuroscience. 22, 389-442 (1999).</li><li>Darabid, H., Perez-Gonzalez, A. P., Robitaille, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuromuscular+synaptogenesis:+coordinating+partners+with+multiple+functions.">Neuromuscular synaptogenesis: coordinating partners with multiple functions.</a> Nature Reviews Neuroscience. 15 (11), 703-718 (2014).</li><li>Fatt, P., Katz, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+analysis+of+the+end-plate+potential+recorded+with+an+intracellular+electrode.">An analysis of the end-plate potential recorded with an intracellular electrode.</a> Journal of Physiology. 115 (3), 320-370 (1951).</li><li>Todd, K. J., Robitaille, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purinergic+modulation+of+synaptic+signalling+at+the+neuromuscular+junction.">Purinergic modulation of synaptic signalling at the neuromuscular junction.</a> Pflugers Archive. 452 (5), 608-614 (2006).</li><li>Hennig, G. W., 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=Use+of+Genetically+Encoded+Calcium+Indicators+(GECIs)+Combined+with+Advanced+Motion+Tracking+Techniques+to+Examine+the+Behavior+of+Neurons+and+Glia+in+the+Enteric+Nervous+System+of+the+Intact+Murine+Colon.">Use of Genetically Encoded Calcium Indicators (GECIs) Combined with Advanced Motion Tracking Techniques to Examine the Behavior of Neurons and Glia in the Enteric Nervous System of the Intact Murine Colon.</a> Frontiers of Cellular Neuroscience. 9, 436 (2015).</li><li>Heredia, D. J., Schubert, D., Maligireddy, S., Hennig, G. W., Gould, T. 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+Novel+Striated+Muscle-Specific+Myosin-Blocking+Drug+for+the+Study+of+Neuromuscular+Physiology.">A Novel Striated Muscle-Specific Myosin-Blocking Drug for the Study of Neuromuscular Physiology.</a> Frontiers of Cellular Neuroscience. 10, 276 (2016).</li><li>Johnson, B. R., Hauptman, S. A., Bonow, 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=Construction+of+a+simple+suction+electrode+for+extracellular+recording+and+stimulation.">Construction of a simple suction electrode for extracellular recording and stimulation.</a> Journal of Undergraduate Neuroscience Education. 6 (1), A21-A26 (2007).</li><li>Hong, S. J., Chang, C. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+geographutoxin+II+(mu-conotoxin)+for+the+study+of+neuromuscular+transmission+in+mouse.">Use of geographutoxin II (mu-conotoxin) for the study of neuromuscular transmission in mouse.</a> British Journal of Pharmacology. 97 (3), 934-940 (1989).</li><li>Heredia, D. J., Feng, C. Y., Hennig, G. W., Renden, R. B., Gould, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activity-induced+Ca2++signaling+in+perisynaptic+Schwann+cells+of+the+early+postnatal+mouse+is+mediated+by+P2Y1+receptors+and+regulates+muscle+fatigue.">Activity-induced Ca2+ signaling in perisynaptic Schwann cells of the early postnatal mouse is mediated by P2Y1 receptors and regulates muscle fatigue.</a> Elife. 7, e30839 (2018).</li><li>Cho, J. H., 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=The+GCaMP-R+Family+of+Genetically+Encoded+Ratiometric+Calcium+Indicators.">The GCaMP-R Family of Genetically Encoded Ratiometric Calcium Indicators.</a> ACS Chemical Biology. 12 (4), 1066-1074 (2017).</li></ol>

Here we provide some examples of measuring Ca2+ responses in specific cells in intact neuromuscular tissue using GECI-expressing mice. In order to successfully perform these experiments, it is imperative not to injure the phrenic nerve during the dissection. To image Ca2+ responses in Schwann cells at either low or high power (i.e., 20X or 60X), it is necessary to use either BHC or &#181;-conotoxin to block movement. For low-power imaging of Ca2+ responses in muscle cells, it is ...

The NMJ, like all synapses, is composed of three elements: a presynaptic terminal derived from a neuron, a postsynaptic neuron/effector cell, and a perisynaptic glial cell1,2. While the basic aspects of synaptic transmission were first demonstrated at this synapse3, many aspects of this process remain unknown, in part owing to the expression of the same molecules by the distinct cellular elements of this synapse. For example, receptors for both the purine adenine nucleotide ATP and acetylcholine (ACh), which are co-released by motor neurons at the vertebrate NMJ, are expressed by muscle, Schwann cells, and motor neurons, thus complicating the interpretation of any functional effect exerted by these substances (e.g., transmitter release or response, muscle force generation)4. Moreover, although the tripartite components of the NMJ are simple compared to, for example, neurons in the central nervous system which often exhibit multiple synaptic inputs, whether motor neurons, muscle cells, or Schwann cells vary in response to stimuli based on their intrinsic heterogeneity (e.g., embryonic derivation, fiber subtype, morphology) is unclear. In order to address each of these issues, it would be advantageous to simultaneously track the response of many cells within one synaptic element, as well as track, at the same time, such a response in either of the other separate elements. Conventional strategies using chemical dyes to measure calcium signaling cannot achieve these two goals, because bath-applied dye is taken up by multiple cell types after application to tissue, and intracellularly loaded dye can only be used to visualize individual or small cohorts of cells. Here, utilizing transgenic mice expressing GECIs designed to measure cell-specific calcium signaling, together with specific imaging and software tools5, we demonstrate the first of these two overall goals and discuss how the addition of new transgenic tools would help achieve the second. This technique will be useful for anyone interested in tracking calcium dynamics or other cellular signaling events observable through gene-encoded optical sensors in multiple cell populations at the same time.

<table>
	<tbody>
		<tr>
			<td>Myf5-Cre mice</td>
			<td>Jax</td>
			<td>#007893</td>
			<td>Drives muscle cell expression as early as E136</td>
		</tr>
		<tr>
			<td>Wnt1-Cre mice</td>
			<td>Jax</td>
			<td>#003829</td>
			<td>Drives expression into all&#160; Schwann cells at E13 but not P209</td>
		</tr>
		<tr>
			<td>Sox10-Cre mice</td>
			<td>Jax</td>
			<td>#025807</td>
			<td>Drives Schwann cell expression at older ages</td>
		</tr>
		<tr>
			<td>Conditional GCaMP3 mice</td>
			<td>Jax</td>
			<td>#029043</td>
			<td>Expresses GCaMP3 in cell-specific fashion</td>
		</tr>
		<tr>
			<td>Conditional GCaMP6f mice</td>
			<td>Jax</td>
			<td>#024105</td>
			<td>Expresses GCaMP6f in cell-specific fashion</td>
		</tr>
		<tr>
			<td>BHC (3-(N-butylethanimidoyl)-4-hydroxy-2H-chromen-2-one)</td>
			<td>Hit2Lead</td>
			<td>#5102862</td>
			<td>Blocks skeletal muscle myosin but not neurotransmission6</td>
		</tr>
		<tr>
			<td>CF594-&#945;-BTX</td>
			<td>Biotium</td>
			<td>#00007</td>
			<td>Labels acetylcholine receptor clusters at NMJ</td>
		</tr>
		<tr>
			<td>&#181;-conotoxin GIIIb</td>
			<td>Peptides Int&#39;l</td>
			<td>#CONO20-01000</td>
			<td>Blocks Nav1.4 voltage-dependent sodium channel8</td>
		</tr>
		<tr>
			<td>Silicone Dielectric Gel; aka Sylgard</td>
			<td>Ellswoth Adhesives</td>
			<td># Sil Dielec Gel .9KG&#160;</td>
			<td>Allows for the immobilization of the diaphragm by minutien pins</td>
		</tr>
		<tr>
			<td>Minutien pins (0.1mm diameter)</td>
			<td>Fine Science Tools</td>
			<td>26002-10</td>
			<td>Immobilizes diaphragm onto silicone dielectric gel</td>
		</tr>
		<tr>
			<td>Eclipse FN1 upright microscope&#160;</td>
			<td>Nikon</td>
			<td>MBA74100</td>
			<td>Allows staging and observation of specimen</td>
		</tr>
		<tr>
			<td>Basic Fixed Microscope Platform with Manual XY Microscope Translator&#160;</td>
			<td>Autom8</td>
			<td>MXMScr</td>
			<td>Allows movement of specimen</td>
		</tr>
		<tr>
			<td>Manual micromanipulator&#160;</td>
			<td>Narishige</td>
			<td>M-152</td>
			<td>Holds recording and stimulating electrodes&#160;</td>
		</tr>
		<tr>
			<td>Microelectrode amplifier&#160;</td>
			<td>Molecular Devices</td>
			<td>Axoclamp 900A</td>
			<td>Allows sharp electrode intracellular electrophysiological recording</td>
		</tr>
		<tr>
			<td>Microelectrode low-noise data acquisition system</td>
			<td>Molecular Devices</td>
			<td>Digidata 1550&#160;</td>
			<td>Allows electrophysiological data acquisition</td>
		</tr>
		<tr>
			<td>Microelectrode data analysis system</td>
			<td>Molecular Devices</td>
			<td>PCLAMP 10 Standard</td>
			<td>Performs electrophysiological data analysis</td>
		</tr>
		<tr>
			<td>Square wave stimulator</td>
			<td>Grass</td>
			<td>S48</td>
			<td>Stimulates nerve to excite muscle</td>
		</tr>
		<tr>
			<td>Stimulus Isolation Unit</td>
			<td>Grass</td>
			<td>PSIU6</td>
			<td>Reduces&#160; stimulation artifacts</td>
		</tr>
		<tr>
			<td>Borosilicate filaments, 1.0 mm outer diameter, 0.5mm internal diameter&#160;</td>
			<td>Sutter</td>
			<td>FG-GBF100-50-15</td>
			<td>Impales and records nerve-evoked muscle potentials</td>
		</tr>
		<tr>
			<td>Borosilicate filaments, 1.5 mm outer diameter, 1.17mm internal diameter&#160;</td>
			<td>Sutter</td>
			<td>BF150-117-15</td>
			<td>Lengthened and used for suction electrode</td>
		</tr>
		<tr>
			<td>Micropipette Puller</td>
			<td>Sutter</td>
			<td>P-97&#160;</td>
			<td>Pulls and prepares recording electrodes</td>
		</tr>
		<tr>
			<td>1200x1200 pixel, back-illuminated cMOS camera&#160;</td>
			<td>Photometrics</td>
			<td>Prime 95b</td>
			<td>Sensitive camera that allows high-resolution, high-speed imaging</td>
		</tr>
		<tr>
			<td>Light Source</td>
			<td>Lumencor</td>
			<td>Spectra X</td>
			<td>Provides illumination from LEDs for fluorescence obsevation</td>
		</tr>
		<tr>
			<td>&#160;Infinity-corrected fluorescent water immersion objectives, W.D. 2mm&#160;</td>
			<td>Nikon</td>
			<td>CFI60</td>
			<td>Provide long working distances for visualization of specimen</td>
		</tr>
		<tr>
			<td>Fiber Optic Illuminator with Halogen lamp</td>
			<td>Sumita</td>
			<td>LS-DWL-N</td>
			<td>Provides illumination for brightfield observation</td>
		</tr>
		<tr>
			<td>W-View Gemini Image Splitter&#160;</td>
			<td>Hamamatsu</td>
			<td>A12801-01</td>
			<td>Projects 1 pair of dual wavelength images separated by a dichroic to single camera</td>
		</tr>
		<tr>
			<td>Single-band Bandpass Filters&#160; (512/25-25 and 630/92-25)&#160;</td>
			<td>SemRock</td>
			<td>FF01-512/25-25; FF01-630/92-25</td>
			<td>Permits dual band imaging</td>
		</tr>
		<tr>
			<td>560 nm Single-Edge Dichroic Beamsplitter</td>
			<td>Sem Rock</td>
			<td>FF560-FDi01-25x36</td>
			<td>Dichroic mirror which separates beams of light to allow dual-wavelength imaging</td>
		</tr>
		<tr>
			<td>Imaging data acquisition system</td>
			<td>Nikon</td>
			<td>NIS Elements - MQS31000</td>
			<td>Allows imaging data acquisition</td>
		</tr>
		<tr>
			<td>Wavelength control module</td>
			<td>Nikon</td>
			<td>MQS41220</td>
			<td>Module for imaging data acqusiition</td>
		</tr>
		<tr>
			<td>Emission splitter hardware module&#160;</td>
			<td>Nikon</td>
			<td>MQS41410</td>
			<td>Module for imaging data acqusiition</td>
		</tr>
		<tr>
			<td>Imaging data analysis system</td>
			<td>NA</td>
			<td>Volumetry 8D5, Fiji</td>
			<td>Allows analysis of fluorescence intensity and other imaging data</td>
		</tr>
	</tbody>
</table>

ex vivo imaging of cell-specific calcium signaling at the tripartite synapse of the mouse diaphragm

The electrical activity of cells in tissues can be monitored by electrophysiological techniques, but these are usually limited to the analysis of individual cells. Since an increase of intracellular calcium (Ca2+) in the cytosol often occurs because of the electrical activity, or in response to a myriad of other stimuli, this process can be monitored by the imaging of cells loaded with fluorescent calcium-sensitive dyes.&#160; However, it is difficult to image this response in an individual cell type within whole tissue because these dyes are taken up by all cell types within the tissue. In contrast, genetically encoded calcium indicators (GECIs) can be expressed by an individual cell type and fluoresce in response to an increase of intracellular Ca2+, thus permitting the imaging of Ca2+ signaling in entire populations of individual cell types. Here, we apply the use of the GECIs GCaMP3/6 to the mouse neuromuscular junction, a tripartite synapse between motor neurons, skeletal muscle, and terminal/perisynaptic Schwann cells. We demonstrate the utility of this technique in classic ex vivo tissue preparations. Using an optical splitter, we perform dual-wavelength imaging of dynamic Ca2+ signals and a static label of the neuromuscular junction (NMJ) in an approach that could be easily adapted to monitor two cell-specific GECI or genetically encoded voltage indicators (GEVI) simultaneously. Finally, we discuss the routines used to capture spatial maps of fluorescence intensity. Together, these optical, transgenic, and analytic techniques can be employed to study the biological activity of distinct cell subpopulations at the NMJ in a wide variety of contexts.

Several examples of fluorescence intensity changes, mediated by increases of intracellular Ca2+ within defined cell types of the NMJ, show the utility of this approach. These results are presented as spatial fluorescence intensity maps, which provide the location of responding cells, as well as the intensity of their responses, thus allowing for the evaluation of how many cells respond and how much each cell responds to a particular stimulus. For example, as shown in <strong cl...

Watch this Scientific Journal Video about Ex Vivo Imaging of Cell-specific Calcium Signaling at the Tripartite Synapse of the Mouse Diaphragm at JoVE.com

Ex Vivo Imaging of Cell-specific Calcium Signaling at the Tripartite Synapse of the Mouse Diaphragm

Here we present a protocol to image calcium signaling in populations of individual cell types at the murine neuromuscular junction.

Ex Vivo Imaging of Cell-specific Calcium Signaling at the Tripartite Synapse of the Mouse Diaphragm

The electrical activity of cells in tissues can be monitored by electrophysiological techniques, but these are usually limited to the analysis of ...

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