This work was funded by the Deutsche Forschungsgemeinschaft DFG (Exc257, SFB958).

NOTE: All animal procedures were handled at the Charit&#233; or University Clinic Jena in accord with German Animal Care laws avoiding any undue suffering of animals.
1. Preparing Solutions and Dissection Workplace
<ol>
	<li>Solutions 
	NOTE: Prepare the following solutions before starting dissection of the epithelium.
	<ol>
		<li>Solutions for the dissection procedure:
		<ol>
			<li>Prepare Ringer&#8217;s solution (pH 7.4) with concentrations of 140 mM NaCl, 5 mM KCl, 10 mM HEPES, 2 mM CaCl2, 1 mM MgCl2, and 10 mM glucose.</li>
			<li>Prepare a PBS-/- solution (pH 7.4) with concentrations of 2.68 mM KCl, 1.47 mM KH2PO4, 136 mM NaCl, and 8.1 mM Na2HPO4.</li>
			<li>Prepare a fixative solution (pH 7.2) with concentrations of 1x PBS-/-, 0.2 mM CaCl2, 4% sucrose, and 4% paraformaldehyde. Sucrose in the fixative solution improves cryosectioning and pick-up of cryosections. Store at -20 &#176;C.</li>
		</ol>
		</li>
		<li>Solutions for the staining procedure
		<ol>
			<li>Prepare a PBS+/+ solution with concentrations of 1x PBS-/-, 0.48 mM MgCl2, 0.9 mM CaCl2.</li>
			<li>Prepare a PBST+/+ solution with concentrations of 1x PBS+/+ and 0.1% Triton X-100.</li>
			<li>Prepare a blocking solution with concentrations of 1x PBST+/+ and 1% gelatine.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Workplace
	<ol>
		<li>For the dissection workplace, use a dissecting microscope with bright illumination, as well as a liquid-blocker pen.</li>
		<li>Prepare a petri dish, filled with Ringer&#8217;s solution, and adhesive glass slides.</li>
		<li>Obtain the following surgical instruments: a pair of surgical scissors with one sharp and one blunt tip, a pair of spring scissors with straight tip shape, two forceps with fine curved tip shape and a razor blade (Figure 1A).</li>
	</ol>
	</li>
</ol>
2. Preparation of the Nasal Septum
<ol>
	<li>House animals in approved cages with regular access to food and water and appropriate day/night cycle.</li>
	<li>Perform anesthesia in a closed receptacle containing gauze soaked with 100% isoflurane and monitor analgesia by testing rear foot reflexes. Since cervical dislocation can cause blood in nasal cavities, directly decapitate anesthetized mice.</li>
	<li>Remove the skin to expose the bone of the entire skull and nose, and wipe away the remaining blood and tissue thoroughly using a paper towel. Remove the lower jaw and the front teeth.</li>
	<li>Incise the dorsal bone of the nose bilaterally in 1-2 mm distance parallel to the suture line to separate one side of the septum (medially) from the maxilla (laterally). Split the nose with a single cut. If bone remnants and turbinates are still attached to the septum, remove these carefully to expose the septum completely without touching it.</li>
	<li>Remove the dorsal nasal bone by sliding the fine curved tip of a forceps along the dorsal side of the septum, between septum and nasal bone. Apply slight pressure on the bone, push it up and remove it.</li>
	<li>To provide access to the two septal tissues, one from each cavity, carefully remove the maxilla of the other side of the head. When preparing older animals (P &#62; 28), remove the tip of the frontal bone covering the olfactory bulbs.</li>
	<li>Identify the olfactory epithelium by its slightly yellow color (Figure 1B). The bordering respiratory epithelium is white and shows movement of motile cilia that can be seen under the dissecting microscope. Cut along the border between olfactory and respiratory epithelium with a pair of fine spring scissors.</li>
	<li>Extend the cut and separate the septum from the ventral connection to the vomer bone. Then cut along the border between the septum and the lamina cribrosa of the Os ethmoidale. The septum is now completely isolated from all connections to the head. Use the cutting positions shown in Figure 1C.</li>
</ol>
3. Isolation of the Olfactory Epithelium for Immunostaining
<ol>
	<li>Place an adhesive glass slide in the petri dish filled with Ringer&#8217;s solution. Place it onto the edge of the petri dish, so that one half of the glass lies in the Ringer&#8217;s solution (Figure 1A).</li>
	<li>Use a forceps to carefully transfer the ethmoid bone with the olfactory epithelium to the petri dish. Lift it without grabbing it with the forceps tips.</li>
	<li>Grab the perpendicular plate of the ethmoid bone with one forceps and use a second one to carefully remove the epithelium from one side of the septum. Slide the curved tip between the perpendicular plate and epithelium to peel the epithelium off.</li>
	<li>Be always sure to identify the ciliary side, in case the epithelium flips in the Ringer&#8217;s solution. If the epithelium flips, it is hardly possible to identify the ciliary side afterwards. Mostly, the epithelium rolls up with the ciliary surface inside.</li>
	<li>Compare the enrolled tissue shape with the cutting positions shown in Figure 1C. Grab the epithelium at a position at the border and pull it onto the glass slide. Do not touch the ciliary side with the forceps to avoid lesions of the tissue.</li>
	<li>Turn the septum and repeat the procedure with the epithelium from the other side.</li>
	<li>Dry the glass slide around both pieces of olfactory epithelium with a paper towel and encircle the tissue with a liquid-blocker pen.</li>
	<li>Fix the tissue with 150&#160;&#181;l fixative solution for 10 min at RT. Concerning cilia stability and integrity, use short fixation times for a variety of tested antibodies. Within these 10 min&#160;cilia are fixed, but probably not the whole epithelium tissue. Thus, immediate visualize with the microscope subsequent to the staining procedure. However, fixative times might vary for individual antibodies.</li>
</ol>
4. Staining Protocol
NOTE: Handle the tissue very carefully to preserve ciliary structures of the olfactory sensory neurons. Remove solutions by pipetting. Do not drop any solutions directly onto the epithelium, as mechanical forces could disrupt the fine cilia. Perform all steps at RT if not stated otherwise.
<ol>
	<li>Remove the fixative solution and wash 2 times with PBS+/+.</li>
	<li>Incubate the epithelium for at least 1 hr with blocking solution.</li>
	<li>Prepare primary antibody solution by dissolving the antibody in blocking solution (1:200 for the antibodies used in this study) and centrifuge for 5 min at full speed to remove any precipitates.</li>
	<li>Incubate the epithelium with antibody solution in a humid chamber at 4 &#176;C O/N.</li>
	<li>Wash epithelium with PBS+/+ for 5 min at least 3 times.</li>
	<li>Prepare secondary antibody solution by dissolving the antibody in blocking solution (1:500) and centrifuge for 5 min at full speed.</li>
	<li>Incubate the epithelium with secondary antibody solution for 1 hr in a dark chamber.</li>
	<li>Wash epithelium with PBS+/+ for 5 min at least 3 times.</li>
	<li>Remove the liquid-blocker with a razor blade or paper towel. Wash the epithelium with distilled water for 5 s.</li>
	<li>Preserve the tissue in antifade mounting reagent. 
	NOTE: Background fluorescence increases rapidly within days; microscopical analysis not later than 2 days after embedding in mounting medium is therefore recommended. Special care has to be taken not to squeeze the tissue when searching the correct focal plane, since it can severely damage the preparation. Due to out-of-focus fluorescence, further investigation with confocal microscopy is recommended.</li>
</ol>

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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=Disruption+of+the+type+III+adenylyl+cyclase+gene+leads+to+peripheral+and+behavioral+anosmia+in+transgenic+mice.">Disruption of the type III adenylyl cyclase gene leads to peripheral and behavioral anosmia in transgenic mice.</a> Neuron. 27 (3), 487-497 (2000).</li><li>Belluscio, L., Gold, G. H., Nemes, A., Axel, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mice+deficient+in+G(olf)+are+anosmic.">Mice deficient in G(olf) are anosmic.</a> Neuron. 20 (1), 69-81 (1998).</li><li>Brunet, L. J., Gold, G. 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W., Bradley, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+of+the+excitatory+Cl-+response+in+mouse+olfactory+receptor+neurons.">Mechanism of the excitatory Cl- response in mouse olfactory receptor neurons.</a> Neuron. 45 (4), 553-561 (2005).</li><li>Hengl, 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=Molecular+components+of+signal+amplification+in+olfactory+sensory+cilia.">Molecular components of signal amplification in olfactory sensory cilia.</a> Proceedings of the National Academy of Sciences of the United States of America. 107 (13), 6052-6057 (2010).</li><li>Smith, D. W., Thach, S., Marshall, E. L., Mendoza, M. G., Kleene, S. 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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrastructural+aspects+of+olfactory+signaling.">Ultrastructural aspects of olfactory signaling.</a> Chemical Senses. 22 (3), 295-311 (1997).</li><li>Serizawa, 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=A+neuronal+identity+code+for+the+odorant+receptor-specific+and+activity-dependent+axon+sorting.">A neuronal identity code for the odorant receptor-specific and activity-dependent axon sorting.</a> Cell. 127 (5), 1057-1069 (2006).</li><li>Baumgart, 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=Scaffolding+by+MUPP1+regulates+odorant-mediated+signaling+in+olfactory+sensory+neurons.">Scaffolding by MUPP1 regulates odorant-mediated signaling in olfactory sensory neurons.</a> Journal Of Cell Science. 127 (11), 2518-2527 (2014).</li><li>Strotmann, J., Wanner, I., Krieger, J., Raming, K., Breer, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+odorant+receptors+in+spatially+restricted+subsets+of+chemosensory+neurones.">Expression of odorant receptors in spatially restricted subsets of chemosensory neurones.</a> Neuroreport. 3 (12), 1053-1056 (1992).</li><li>Jenkins, P. 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The authors have nothing to disclose.

The en face preparation technique described in this protocol provides a powerful tool for the detailed analysis of the olfactory system. So far, most studies characterizing the localization of signaling proteins use immunostainings of cryosections. They present a good overview of the olfactory epithelium, and protein expression in distinct cell types or regions can be easily identified. However, expression in olfactory cilia is sometimes hard to detect. Even if ciliary localization is obvious, cryosections offer...

The mouse olfactory epithelium in the nasal cavity comprises 6-10 million bipolar olfactory sensory neurons1. Each olfactory neuron chooses one of 1,200 odorant receptor genes for expression. Detection of odorants starts by odorant binding to an olfactory receptor2, which then activates adenylyl cyclase type-III (ACIII)3 via the olfactory specific G protein G&#945;olf4. The resulting rise in cyclic adenosine monophosphate (cAMP) opens a cyclic nucleotide-gated (CNG), nonselective cation channel leading to influx of Ca2+ and Na+, and subsequently Ca2+ influx leads to opening of a Ca2+ activated Cl- channel5,6. The resulting outward Cl- flux is facilitated by a high intracellular Cl- concentration maintained by steady Cl- uptake, likely via the Na+/K+/Cl- cotransporter NKCC1, the Cl-/HCO3- exchanger SLC4A1, and maybe additional yet to be identified transporters6-8.
Bipolar olfactory neurons have single, unbranched axons that project directly to the olfactory bulb, and a dendrite that extends to the surface of the epithelium and ends as a specialized compartment, the dendritic knob. From this knob, 10-30 cilia, which can reach a length of up to 50-60 &#181;m, emanate into the mucus covering the epithelial surface9. Proteins of the canonical signal transduction cascade are mainly localized in the membrane of these cilia. The increased sensory surface of the epithelium amplifies the ability to detect odorants. Due to the density of sensory neurons, cilia extending from neighboring dendritic knobs intermingle. This intermingling results in a random mixture of cilia from different neurons, expressing different types of olfactory receptors, on the surface of the epithelium. The detection and cellular allocation of ciliary proteins which are only present in a subset of sensory neurons is therefore difficult in cryosections. In addition, the precise localization of such proteins along the cilia is barely possible, since cryosections are typically thinner than the average length of the cilia.
To enable investigation of ciliary localization of so far uncharacterized membrane proteins in olfactory neurons, we optimized an en face preparation technique which allows the detailed analysis of protein localization in cilia. Briefly, the mouse is sacrificed and the head split near the midline. Turbinates, nasal, and frontal bones are removed to expose the septum. The septum with the olfactory part of the lining epithelium is loosened by cutting all connections to the nasal cavity. After putting the septum into a petri dish filled with Ringer&#8217;s solution, the epithelium is peeled off und transferred to a coated glass slide. Following a short fixation step, immunostaining procedures can be performed if handling is as gentle as possible to avoid damage of the fragile tissue. We demonstrate the achievable resolution by comparing the staining of two different membrane proteins in olfactory cilia in classical cryosections and in the en face preparation described.

<table border="0" cellpadding="0" cellspacing="0" width="629">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:127px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Spring scissors</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">straight tip, multiple suppliers</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Surgical scissors</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">sharp and blunt end, multiple suppliers</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Fine forceps</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">curved tips, Dumont #7, multiple suppliers</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Razor blade</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">extra thin, multiple suppliers</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Binocular with illumination</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">multiple suppliers, Stemi 2000-C, Zeiss</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Petri dish</td>
			<td style="width:127px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">multiple suppliers</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Liquid-blocker pen</td>
			<td style="width:127px;">Science Services</td>
			<td style="width:119px;">N71310</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Polysine coated slides</td>
			<td style="width:127px;">Thermo Scientific</td>
			<td style="width:119px;">J2800AMNZ</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Confocal microscope</td>
			<td style="width:127px;">Leica Microsystems</td>
			<td style="width:119px;">TCS SPE</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">primary antibody Goat anti-Kirrel2</td>
			<td style="width:127px;">R&#38;D Systems</td>
			<td style="width:119px;">AF2930</td>
			<td style="width:167px;">1:200</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">primary antibody Rabbit anti-mOR-EG</td>
			<td style="width:127px;">Baumgart et al., 2014</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">1:200</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">secondary antibodies</td>
			<td style="width:127px;">Life Technologies</td>
			<td style="width:119px;">A21206, A11057</td>
			<td style="width:167px;">1:500</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Mounting medium, ProLong Gold antifade reagent</td>
			<td style="width:127px;">Life Technologies</td>
			<td style="width:119px;">P36930</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Paraformaldehyde</td>
			<td style="width:127px;">Sigma</td>
			<td align="right" style="width:119px;">441244</td>
			<td style="width:167px;">toxic, work under fume hood</td>
		</tr>
	</tbody>
</table>

whole mount labeling of cilia in the main olfactory system of mice

The mouse olfactory system comprises 6-10 million olfactory sensory neurons in the epithelium lining the nasal cavity. Olfactory neurons extend a single dendrite to the surface of the epithelium, ending in a structure called dendritic knob. Cilia emanate from this knob into the mucus covering the epithelial surface. The proteins of the olfactory signal transduction cascade are mainly localized in the ciliary membrane, being in direct contact with volatile substances in the environment. For a detailed understanding of olfactory signal transduction, one important aspect is the exact morphological analysis of signaling protein distribution. Using light microscopical approaches in conventional cryosections, protein localization in olfactory cilia is difficult to determine due to the density of ciliary structures. To overcome this problem, we optimized an approach for whole mount labeling of cilia, leading to improved visualization of their morphology and the distribution of signaling proteins. We demonstrate the power of this approach by comparing whole mount and conventional cryosection labeling of Kirrel2. This axon-guidance adhesion molecule is known to localize in a subset of sensory neurons and their axons in an activity-dependent manner. Whole mount cilia labeling revealed an additional and novel picture of the localization of this protein.

Olfactory epithelium en face preparations can be used to investigate localization of proteins in the cilia of sensory neurons, allowing the detailed investigation of proteins whose localization is unclear after analysis of cryosections. This problem can be exemplified in the case of the staining for Kin of IRRE-like protein 2 (Kirrel2). Kirrel2 (also called Neph3) is a member of the immunoglobulin (Ig) superfamily of membrane proteins and functions as a homophilic adhesion protein. It was shown to play a role in...

Watch this Scientific Journal Video about Whole Mount Labeling of Cilia in the Main Olfactory System of Mice at JoVE.com

Whole Mount Labeling of Cilia in the Main Olfactory System of Mice

Cilia of olfactory sensory neurons contain proteins of the signal transduction cascade, but a detailed spatial analysis of their distribution is difficult in cryosections. We describe here an optimized approach for whole mount labeling and en face visualization of ciliary proteins.

The mouse olfactory system comprises 6-10 million olfactory sensory neurons in the epithelium lining the nasal cavity. Olfactory neurons extend a single ...

whole-mount-labeling-of-cilia-in-the-main-olfactory-system-of-mice

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Neuroscience

11.0K Views.  Universitaetsklinikum Jena. Cilia of olfactory sensory neurons contain proteins of the signal transduction cascade, but a detailed spatial analysis of their distribution is difficult in cryosections. We describe here an optimized approach for whole mount labeling and en face visualization of ciliary proteins.

Video: Whole Mount Labeling of Cilia in the Main Olfactory System of Mice

Visualization of the Embryonic Nervous System in Whole-mount Drosophila Embryos

The Drosophila embryo is an attractive model system for investigating the cellular and molecular basis of neuronal development. Here we describe the procedure for the visualization of Drosophila embryonic nervous system using antibodies to neuronal proteins. Since the entire embryonic peripheral nervous and central nervous systems are well characterized at the level of individual cells (Dambly-Chaudi&egrave;re et al., 1986; Bodmer et al., 1987; Bodmer et al., 1989), any aberrations to these systems can be easily identified using antibodies to different neuronal proteins. The developing embryos are collected at certain times to ensure that the embryos are in the proper developmental stages for visualization. After collection, the outer layers of the embryo, the chorion membrane and the vitelline envelope that surrounds the embryo, are removed before fixation. Embryos are then incubated with neuronal antibodies and visualized using fluorescently labeled secondary antibodies. Embryos at stages 12-17 are visualized to access the embryonic nervous system. At stage 12 the CNS germ band starts shortening and by stage 15 the definitive pattern of the commissure has been achieved. By stage 17 the CNS contracts and the PNS is fully developed (Campos-Ortega et al. 1985). Thus changes in the pattern of the PNS and CNS can be easily observed during these developmental stages.

Visualization of the Embryonic Nervous System in Whole-mount Drosophila Embryos

We describe the procedure to prepare staged Drosophila embryos for the visualization of the embryonic nervous system during embryogenesis.

The Drosophila embryo is an attractive model system for investigating the cellular and molecular basis of neuronal development. Here we describe the ...

Flash Photolysis of Caged Compounds in the Cilia of Olfactory Sensory  Neurons

Photolysis of caged compounds allows the production of rapid and localized increases in the concentration of various physiologically active compounds1. Caged compounds are molecules made physiologically inactive by a chemical cage that can be broken by a flash of ultraviolet light. Here, we show how to obtain patch-clamp recordings combined with photolysis of caged compounds for the study of olfactory transduction in dissociated mouse olfactory sensory neurons. The process of olfactory transduction (Figure 1) takes place in the cilia of olfactory sensory neurons, where odorant binding to receptors leads to the increase of cAMP that opens cyclic nucleotide-gated (CNG) channels2. Ca entry through CNG channels activates Ca-activated Cl channels. We show how to dissociate neurons from the mouse olfactory epithelium3 and how to activate CNG channels or Ca-activated Cl channels by photolysis of caged cAMP4 or caged Ca5. We use a flash lamp6,7 to apply ultraviolet flashes to the ciliary region to uncage cAMP or Ca while patch-clamp recordings are taken to measure the current in the whole-cell voltage-clamp configuration8-11.

Photolysis of caged compounds allows the production of rapid and localized increases in the concentration of various physiologically active compounds. Here, we show how to obtain patch-clamp recordings combined with photolysis of caged cAMP or caged Ca for the study of olfactory transduction in dissociated mouse olfactory sensory neurons.

Photolysis of caged compounds allows the production of rapid and localized increases in the concentration of various physiologically active compounds1. ...

DiI-Labeling of DRG Neurons to Study Axonal Branching in a Whole Mount Preparation of Mouse Embryonic Spinal Cord

Here we present a technique to label the trajectories of small groups of DRG neurons into the embryonic spinal cord by diffusive staining using the lipophilic tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)1. The comparison of axonal pathways of wild-type with those of mouse lines in which genes are mutated allows testing for a functional role of candidate proteins in the control of axonal branching which is an essential mechanism in the wiring of the nervous system. Axonal branching enables an individual neuron to connect with multiple targets, thereby providing the physical basis for the parallel processing of information. Ramifications at intermediate target regions of axonal growth may be distinguished from terminal arborization. Furthermore, different modes of axonal branch formation may be classified depending on whether branching results from the activities of the growth cone (splitting or delayed branching) or from the budding of collaterals from the axon shaft in a process called interstitial branching2 (Fig. 1).
The central projections of neurons from the DRG offer a useful experimental system to study both types of axonal branching: when their afferent axons reach the dorsal root entry zone (DREZ) of the spinal cord between embryonic days 10 to 13 (E10 - E13) they display a stereotyped pattern of T- or Y-shaped bifurcation. The two resulting daughter axons then proceed in rostral or caudal directions, respectively, at the dorsolateral margin of the cord and only after a waiting period collaterals sprout from these stem axons to penetrate the gray matter (interstitial branching) and project to relay neurons in specific laminae of the spinal cord where they further arborize (terminal branching)3. DiI tracings have revealed growth cones at the dorsal root entry zone of the spinal cord that appeared to be in the process of splitting suggesting that bifurcation is caused by splitting of the growth cone itself4 (Fig. 2), however, other options have been discussed as well5.
This video demonstrates first how to dissect the spinal cord of E12.5 mice leaving the DRG attached. Following fixation of the specimen tiny amounts of DiI are applied to DRG using glass needles pulled from capillary tubes. After an incubation step, the labeled spinal cord is mounted as an inverted open-book preparation to analyze individual axons using fluorescence microscopy.

The stereotyped projections of sensory afferents into the rodent spinal cord offer an easily accessible experimental system to study axonal branching through the tracing of single axons.

Here we  present a technique to label the trajectories of small groups of DRG neurons  into the embryonic spinal cord by diffusive staining using the ...

Labeling of Single Cells in the Central Nervous System of Drosophila melanogaster

In this article we describe how to individually label neurons in the embryonic CNS of Drosophila melanogaster by juxtacellular injection of the lipophilic fluorescent membrane marker DiI. This method allows the visualization of neuronal cell morphology in great detail. It is possible to label any cell in the CNS: cell bodies of target neurons are visualized under DIC optics or by expression of a fluorescent genetic marker such as GFP. After labeling, the DiI can be transformed into a permanent brown stain by photoconversion to allow visualization of cell morphology with transmitted light and DIC optics. Alternatively, the DiI-labeled cells can be observed directly with confocal microscopy, enabling genetically introduced fluorescent reporter proteins to be colocalised. The technique can be used in any animal, irrespective of genotype, making it possible to analyze mutant phenotypes at single cell resolution.

Labeling of Single Cells in the Central Nervous System of Drosophila melanogaster

We present a technique for labeling single neurons in the central nervous system (CNS) of Drosophila embryos, which allows the analysis of neuronal morphology by either transmitted light or confocal microscopy.

In this  article we describe how to individually label neurons in the embryonic CNS of Drosophila melanogaster by juxtacellular injection of the ...

Whole Mount Immunofluorescent Staining of the Neonatal Mouse Retina to Investigate Angiogenesis In vivo

Angiogenesis is the complex process of new blood vessel formation defined by the sprouting of new blood vessels from a pre-existing vessel network. Angiogenesis plays a key role not only in normal development of organs and tissues, but also in many diseases in which blood vessel formation is dysregulated, such as cancer, blindness and ischemic diseases. In adult life, blood vessels are generally quiescent so angiogenesis is an important target for novel drug development to try and regulate new vessel formation specifically in disease. In order to better understand angiogenesis and to develop appropriate strategies to regulate it, models are required that accurately reflect the different biological steps that are involved. The mouse neonatal retina provides an excellent model of angiogenesis because arteries, veins and capillaries develop to form a vascular plexus during the first week after birth. This model also has the advantage of having a two-dimensional (2D) structure making analysis straightforward compared with the complex 3D anatomy of other vascular networks. By analyzing the retinal vascular plexus at different times after birth, it is possible to observe the various stages of angiogenesis under the microscope. This article demonstrates a straightforward procedure for analyzing the vasculature of a mouse retina using fluorescent staining with isolectin and vascular specific antibodies.

Whole Mount Immunofluorescent Staining of the Neonatal Mouse Retina to Investigate Angiogenesis In vivo

The neonatal murine retina provides a well characterized physiological model of angiogenesis, which permits investigations of the roles of different genes or drugs that modulate angiogenesis in an in vivo context. Immunofluorescent staining to accurately visualize the vascular plexus is pivotal to the success of these types of studies.

Angiogenesis  is the complex process of new blood vessel formation defined by the sprouting  of new blood vessels from a pre-existing vessel network. ...

Dissection of the Transversus Abdominis Muscle for Whole-mount Neuromuscular Junction Analysis

Analysis of neuromuscular junction morphology can give important insight into the physiological status of a given motor neuron. Analysis of thin flat muscles can offer significant advantage over traditionally used thicker muscles, such as those from the hind limb (e.g. gastrocnemius). Thin muscles allow for comprehensive overview of the entire innervation pattern for a given muscle, which in turn permits identification of selectively vulnerable pools of motor neurons. These muscles also allow analysis of parameters such as motor unit size, axonal branching, and terminal/nodal sprouting. A common obstacle in using such muscles is gaining the technical expertise to dissect them. In this video, we detail the protocol for dissecting the transversus abdominis (TVA) muscle from young mice and performing immunofluorescence to visualize axons and neuromuscular junctions (NMJs). We demonstrate that this technique gives a complete overview of the innervation pattern of the TVA muscle&#160;and can be used to investigate NMJ pathology in a mouse model of the childhood motor neuron disease, spinal muscular atrophy.

Dissection of the Transversus Abdominis Muscle for Whole-mount Neuromuscular Junction Analysis

In this video we demonstrate a protocol for dissection of the transversus abdominis muscle of the mouse and use immunofluorescence and microscopy to visualize neuromuscular junctions.

Analysis of neuromuscular junction morphology can give important insight into the physiological status of a given motor neuron. Analysis of thin flat ...

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

Odorant molecules bind to their target receptors in a precise and coordinated manner. Each receptor recognizes a specific signal and relays this information to the brain. As such, determining how olfactory information is transferred to the brain, modifying both perception and behavior, merits investigation. Interestingly, there is emerging evidence that cellular transduction and transcriptional factors are involved in the diversification of olfactory receptor neuron. Here we provide a robust whole mount immunological labeling method to assay in vivo olfactory receptor neuron organization. Using this method, we identified all olfactory receptor neurons with anti-ELAV antibody, a known pan-neural marker and Or49a-mCD8::GFP, an olfactory receptor neuron specifically expressed in Nba neuron using anti-GFP antibody.

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

Herein we describe the process of whole mount immunostaining of Drosophila antennae, which enables us to better understand the molecular mechanisms involved in the diversification of olfactory receptor neurons (ORN)s.

Odorant molecules bind to their target receptors in a precise and coordinated manner. Each receptor recognizes a specific signal and relays this ...

Live Imaging of the Ependymal Cilia in the Lateral Ventricles of the Mouse Brain

Multiciliated ependymal cells line the ventricles in the adult brain. Abnormal function or structure of ependymal cilia is associated with various neurological deficits. The current ex vivo live imaging of motile ependymal cilia technique allows for a detailed study of ciliary dynamics following several steps. These steps include: mice euthanasia with carbon dioxide according to protocols of The University of Toledo&#8217;s Institutional Animal Care and Use Committee (IACUC); craniectomy followed by brain removal and sagittal brain dissection with a vibratome or sharp blade to obtain very thin sections through the brain lateral ventricles, where the ependymal cilia can be visualized. Incubation of the brain&#8217;s slices in a customized glass-bottom plate containing Dulbecco&#8217;s Modified Eagle&#8217;s Medium (DMEM)/High-Glucose at 37 &#176;C in the presence of 95%/5% O2/CO2 mixture is essential to keep the tissue alive during the experiment. A video of the cilia beating is then recorded using a high-resolution differential interference contrast microscope. The video is then analyzed frame by frame to calculate the ciliary beating frequency. This allows distinct classification of the ependymal cells into three categories or types based on their ciliary beating frequency and angle. Furthermore, this technique allows the use of high-speed fluorescence imaging analysis to characterize the unique intracellular calcium oscillation properties of ependymal cells as well as the effect of pharmacological agents on the calcium oscillations and the ciliary beating frequency. In addition, this technique is suitable for immunofluorescence imaging for ciliary structure and ciliary protein localization studies. This is particularly important in disease diagnosis and phenotype studies. The main limitation of the technique is attributed to the decrease in live motile cilia movement as the brain tissue starts to die.

Using high-resolution differential interference contrast (DIC) microscopy, an ex vivo observation of the beating of motile ependymal cilia located within the mouse brain ventricles is demonstrated by live-imaging. The technique allows a recording of the unique ciliary beating frequency and beating angle as well as their intracellular calcium oscillation pacing properties.

Multiciliated ependymal cells line the ventricles in the adult brain. Abnormal function or structure of ependymal cilia is associated with various ...

Whole Mount Dissection and Immunofluorescence of the Adult Mouse Cochlea

The organ of Corti, housed in the cochlea of the inner ear, contains mechanosensory hair cells and surrounding supporting cells which are organized in a spiral shape and have a tonotopic gradient for sound detection. The mouse cochlea is approximately 6 mm long and often divided into three turns (apex, middle, and base) for analysis. To investigate cell loss, cell division, or mosaic gene expression, the whole mount or surface preparation of the cochlea is useful. This dissection method allows visualization of all cells within the organ of Corti when combined with immunostaining and confocal microscopy to image cells at different planes in the z-axis. Multiple optical cross-sections can also be obtained from these z-stack images. In addition, the whole mount dissection method can be used for scanning electron microscopy, although a different fixation method is needed. Here, we present a method to isolate the organ of Corti as three intact cochlear turns (apex, middle, and base). This method can be used for mice ranging from one week of age through adulthood and differs from the technique used for neonatal samples where calcification of the cochlea is incomplete. A slightly modified version can be used for dissection of the rat cochlea. We also demonstrate a procedure for immunostaining with fluorescently tagged antibodies.

We present a method to isolate the adult organ of Corti as three intact cochlear turns (apex, middle, and base). We also demonstrate a procedure for immunostaining with fluorescently tagged antibodies. Together these techniques allow the study of hair cells, supporting cells, and other cell types found in the cochlea.

The organ of Corti, housed in the cochlea of the inner ear, contains mechanosensory hair cells and surrounding supporting cells which are organized in a ...

HSV-Mediated Transgene Expression of Chimeric Constructs to Study Behavioral Function of GPCR Heteromers in Mice

The heteromeric receptor complex between 5-HT2A and mGlu2 has been implicated in some of the behavioral phenotypes in mouse models of psychosis1,2. Consequently, investigation of structural details of the interaction between 5-HT2A and mGlu2 affecting schizophrenia-related behaviors represents a powerful translational tool. As previously shown, the head-twitch response (HTR) in mice is elicited by hallucinogenic drugs and this behavioral response is absent in 5-HT2A knockout (KO) mice3,4. Additionally, by conditionally expressing the 5-HT2A receptor only in cortex, it was demonstrated that 5-HT2A receptor-dependent signaling pathways on cortical pyramidal neurons are sufficient to elicit head-twitch behavior in response to hallucinogenic drugs3. Finally, it has been shown that the head-twitch behavioral response induced by the hallucinogens DOI and lysergic acid diethylamide (LSD) is significantly decreased in mGlu2-KO mice5. These findings suggest that mGlu2 is at least in part necessary for the 5-HT2A receptor-dependent psychosis-like behavioral effects induced by LSD-like drugs. However, this does not provide evidence as to whether the 5-HT2A-mGlu2 receptor complex is necessary for this behavioral phenotype. To address this question, herpes simplex virus (HSV) constructs to express either mGlu2 or mGlu2&#916;TM4N (mGlu2/mGlu3 chimeric construct that does not form the 5-HT2A-mGlu2 receptor complex) in the frontal cortex of mGlu2-KO mice were used to examine whether this GPCR heteromeric complex is needed for the behavioral effects induced by LSD-like drugs6.

This article describes how to inject viral vectors into the mouse frontal cortex to test behavioral assays that require GPCR heteromeric formation.

The heteromeric receptor complex between 5-HT2A and mGlu2 has been implicated in some of the behavioral phenotypes in mouse models of psychosis1,2.  ...