This research was supported in part by the Intramural Research Program of the NIH, NIDCD to M.H. (DC000088)

All animal experiments and procedures were performed according to protocols approved by the Animal Care and Use Committee of the National Institute of Neurological Diseases and Stroke and the National Institute on Deafness and Other Communication Disorders, National Institutes of Health. All experimental protocols were approved by the Animal Care and Use Committee of the National Institute of Neurological Diseases and Stroke and the National Institute on Deafness and Other Communication Disorders, National Institutes of Health. All methods were carried out in accordance with relevant guidelines and regulations of the Animal Care and Use Committee of the National Institute of Neurological Diseases and Stroke and the National Institute on Deafness and Other Communication Disorders, National Institutes of Health.
1. Animal euthanasia
<ol>
	<li>Use C57BL/6J or Kcnj10-ZsGreen transgenic mice, postnatal day 30+ (P30+), that weigh between 15-20 g.</li>
	<li>Euthanize an adult mouse (age P30 or older) using an approved protocol (here CO2 asphyxiation). Perform decapitation as a secondary step. 
	NOTE: If immunostaining, some antibodies may have background signal due to nonspecific binding to blood in the capillaries of the SV. Cardiac perfusion with fixative can address this issue by removing blood from the capillaries of the SV. However, most antibodies can achieve good results without this method, and it will not be covered in this protocol.</li>
</ol>
2. Exposing bony labyrinth
<ol>
	<li>Clean the mouse by spraying with 70% ethanol and wiping with a paper towel. Pay particular attention to the head region to reduce the risk of contamination. Remove the skin from the skull by pulling the skin toward the nose.</li>
	<li>Using sharp scissors, split the skull along the midsagittal plane to separate the left and right portions.</li>
	<li>Remove the brain from the skull to expose the bony labyrinth.</li>
</ol>
3. Inner ear extraction
<ol>
	<li>Identify the inner ear within the temporal bone (Figure 2A) and scrape away the cranial nerves using #55 forceps. 
	NOTE: The user should stabilize the specimen with their nondominant hand using a second set of #55 forceps. Different areas of the specimen may be grabbed with the stabilizing forceps throughout the dissection if critical areas of the specimen are avoided (e.g., do not crush the cochlea).</li>
	<li>Using #55 forceps, dissect out the bulla and capsule, detaching them from surrounding bone. Remove any remaining soft tissue from the inner ear surface.</li>
	<li>Transfer the specimen to a clear tissue culture dish containing 1x cold PBS (phosphate-buffered saline), pH 7.4, and place under a dissection scope (Figure 2B).</li>
</ol>
4. SV dissection
NOTE: With practice, it is possible to dissect the SV as one long piece resembling a ribbon. The SV is fragile, so if it breaks into pieces, these may be stored together. Alternatively, these can be stored in separately labeled wells according to their turn (e.g., basal, middle, apical).
<ol>
	<li>If the dissection scope light sources can be moved, place one light above the dish and the second light source from the side, parallel to the dissecting surface. This allows for a better contrast of the tissue under the cochlear bone.</li>
	<li>Using #55 forceps, hold the specimen by the vestibular portion with the cochlea facing up.</li>
	<li>Using #55 forceps, pierce through the cochlear bone at the apex. 
	NOTE: #5 forceps are thicker than #55 and may be used for breaking bone, but the increase in size/strength sacrifices the fineness of the forceps and the ability to manipulate small tissues. Consider using forceps made with a material such as inox or dumostar to avoid damage that may occur to more delicate forceps. Avoid pushing the forceps too deep under the bone to avoid damaging the SV.</li>
	<li>Using #55 forceps, scrape along the apical turn (Figure 2C), applying gentle force to break away small pieces of the outer bone layer. Gently lift the bone and detach it from the lateral wall. 
	NOTE: It may be helpful to think about this dissection as &#34;removing everything away from the SV&#34;, rather than &#34;dissecting the SV out of the cochlea&#34;.</li>
	<li>Continue using #55 forceps to remove cochlear bone pieces from the apical and middle turns (Figure 2D,E). Gently pushing down the lateral wall, pry and remove bone wall pieces toward the middle turn to expose the lateral wall of the apical and middle turns.</li>
	<li>Continuing using #55 forceps, gently push the apical turn lateral wall aside to expose the spiral ganglion. Detach the lateral wall of apical and middle turns from the spiral ganglion along the outer hair cell layer. Remove pieces of spiral ganglion from inside the cochlea. 
	NOTE: #55 forceps are smaller and provide an advantage when manipulating small and delicate tissues. Extra care should be taken to avoid bending or damaging them.</li>
	<li>To have better access to the lateral wall of the basal turn, detach the cochlea from the vestibular portion of the temporal bone using #55 forceps. Put the #55 forceps into the round and oval window and push down toward the vestibule. The cochlea will detach. Remove the vestibular portion of the inner ear.</li>
	<li>Continuing using #55 forceps, now remove pieces of basal cochlear bone, starting from the middle turn area. Gently push the lateral wall layer under the bone to detach it.</li>
	<li>Remove the farthest basal part of the lateral wall by prying and gently pulling the tissue. The bone in this region may be too thick to be removed without damaging the soft tissue below.</li>
	<li>Now, with the basal part of the lateral wall detached, separate as much of the lateral wall from the cochlea as possible. This can be done by tracing the #55 forceps along the lateral wall. Gently brush the forceps between the bone and the remaining lateral wall. This can be done all the way to the apex in one piece if the user is experienced. Move the lateral wall to fresh PBS. 
	NOTE: Although larger pieces of SV may be easier to image, given the delicate nature of the tissues, smaller pieces can be taken (Figure 2F,G), and depending on the size, can also work for imaging.</li>
	<li>Use #55 forceps to lay the lateral wall flat. The SV should be visible as a darker layer of tissue on the internal side of the lateral wall. 
	NOTE: Users may find, particularly closer to the apical end, that some of the SV tissue incidentally detaches from the lateral wall throughout the dissection.</li>
	<li>Gently pry the SV layer to detach it from the lateral wall at its basal end (Figure 2H). Gently push aside the detached SV and move the forceps further toward the apical end of the lateral wall, detaching the SV as one long ribbon if possible (Figure 2I). Do not squeeze the SV with forceps to pull it. If the tissue is too fragile to be grabbed, it can alternatively be collected using a tissue scoop, such as a chalazion curette. 
	NOTE: Moving the SV should always be done under light microscopy to ensure it is not lost. Always be careful when grabbing using forceps due to the risk of damage. Users may find that using chalazion curette mitigates the risk of damage to SV tissue. For single-nucleus sequencing, proceed to section 5. For SV immunostaining, proceed to section 7.</li>
</ol>
5. SV single-nucleus suspension
NOTE: This protocol is adapted for SV tissue specifically from a published manufacturer&#39;s single-nucleus suspension protocol. Platforms from different manufacturers may be used31. Given platform-specific variation, it is recommended to review the manufacturer-specific protocol provided with the equipment. To achieve optimal results for sNuc-Seq and minimize RNA degradation, the faster the tissue dissection the better (recommended within 15-20 min from euthanasia). It may be helpful to euthanize one animal at a time and only when ready to dissect. Having multiple people simultaneously work on the dissections can also eliminate degradation time (e.g., one lab personnel working on the left ear while another works on right ear).
<ol>
	<li>If the SV tissue will be used for sNuc-Seq, place the tissue in chilled lysis buffer (10 mM Tris-HCl, 10 mM NaCl, 3 mM MgCl2, 0.005% nonidet P40 in nuclease free water). 
	NOTE: If sequencing is to be done immediately following dissection, continue the protocol. If it is desired to pause the protocol, SV preservation is possible by placing the SV into RNAlater. Store overnight at 4 &#176;C, then flash freeze in liquid nitrogen and store at -80 &#176;C until ready to use. When ready to use, thaw and wash twice in PBS for 5 min each, then proceed with homogenization (step 5.2).</li>
	<li>Homogenize the tissue in a 2 mL dounce homogenizer with 10-20 strokes on ice. 
	NOTE: The glass cylinder will manually contact the bottom of the glass tube, fragmenting the SV. The SV is delicate, so 20 strokes usually achieves successful homogenization.</li>
	<li>Lyse the tissue on ice for 25 min. 
	NOTE: The lysis time varies according to the tissue type. A 25 min lysis in SV tissue may achieve a low cell viability (less than 4%), but the time may be adapted if the cell viability is too high (step 5.8).</li>
	<li>Filter through a 30 &#181;m filter and spin the filtrate at 500 x g for 5 min at 4 &#176;C.</li>
	<li>Remove the supernatant and resuspend the cell pellet in 1 mL of nuclei wash and resuspension buffer (1x PBS, 1% bovine serum albumin [BSA], 0.2U/&#181;L RNase inhibitor).</li>
	<li>Filter the cells through a 10 &#181;m filter and centrifuge at 500 x g for 5 min at 4 &#176;C.</li>
	<li>Remove the supernatant and resuspend in 50 &#181;L of nuclei wash and resuspension buffer.</li>
	<li>Count the nuclei using a cell counter and trypan blue staining. Dilute 5 &#181;L of the cell suspension into 50 &#181;L of 1x PBS for cell counting; The viability should be minimal (3%-4%) at this point. If the viability is found to be higher, adapt the protocol for step 5.3 (lysis) and standardize the lysis time to ensure adequate lysis of the cells. 
	NOTE: A high cell viability in a single nucleus preparation means there are more intact cells than desired, and that additional digestion may be required.</li>
	<li>Load the sample with the desired nuclear density onto the manufacturer&#39;s apparatus/chip (see manufacturers guide). Single-nuclei captures are now ready. 
	&#8203;NOTE: From one adult mouse SV, 50 &#181;L of the suspension at a concentration of 150,000 nuclei/mL is usually achieved.</li>
</ol>
6. SV single-nucleus sequencing
<ol>
	<li>Send the samples to the core facility for sequencing. 
	NOTE: This part of the protocol follows the general steps of (1) gel beads-in emulsion (GEM) generation and barcoding, (2) post-GEM-RT cleanup and cDNA amplification, and (3) 3&#39; gene expression library construction. The remainder of the sNuc-Seq protocol is relatively lengthy, and it is recommended that readers use their manufacturer-specific protocol. The manufacturer guide will likely describe steps with specific details and accompanying images. There may also be &#39;how-to&#39; videos on the manufacturer website. Datasets generated may be represented in a dimensional reduced fashion, such as a uniform manifold approximation and projection (UMAP; Figure 3). Many labs utilize a sequencing core that may perform this protocol for users.</li>
</ol>
7. SV immunostaining and tissue mounting
<ol>
	<li>If the tissue will be used for immunostaining, transfer it to a 24-well plate, submerged in 200 &#181;L of 4% paraformaldehyde (PFA) in 1x PBS, and incubate for 20 min at room temperature. 
	NOTE: It is helpful to perform all liquid removal, washing, and immunostaining underneath a microscope. Visualization while pipetting the tissue will ensure it is not accidently lost during liquid removal. The volumes of the antibodies and washes may be adjusted as long as the volume is large enough to submerge the SV tissue within the solution.</li>
	<li>After the fixation step, remove the PFA by performing two short washes in 1x PBS (approximately 500 &#181;L) at 4 &#176;C for 5 min each on an orbital shaker at low (30-50) RPM. If storing, the tissue can be stored in 1x PBS at 4 &#176;C.</li>
	<li>Remove the PBS and permeabilize and block for a minimum of 1 h at room temperature in approximately 300 &#181;L of PBS-T solution (0.05 Tween20 in 1x PBS with 10% fetal bovine serum). 
	NOTE: Primary and secondary antibodies should be diluted in this blocking solution.</li>
	<li>Stain the tissue with primary antibody according to the specifications of the particular antibody used, usually overnight at 4 &#176;C . Remove the remaining PBS and add the diluted primary antibody. 
	NOTE: The dilution should be chosen based on the manufacturer suggestions, published data, previous experience, etc. Usually, the first concentration to test is a 1:100-200 dilution. For the example presented in this paper, the GS-IB4 and DAPI antibodies were each diluted at 1:200. If staining for more than one protein, multiple primary antibodies can be combined into the same solution, as long as each primary antibody has a different host to avoid cross reactivity of secondary antibodies.</li>
	<li>Wash the primary antibody off the tissue using approximately 500 &#181;L of 1x PBS twice for 10 min each on an orbital shaker at low RPM. 
	NOTE: Continue to ensure that the SV tissue is submerged in the solution, and not stuck on the side of the well.</li>
	<li>Stain with a secondary antibody according to the specifications of the particular antibody used, usually for 2 h at room temperature on an orbital shaker at low RPM. Cover the 24-well plate so the fluorescently tagged secondary antibody is protected from light. 
	NOTE: If more than one secondary antibody is needed, combine the secondary antibodies into the same solution. Ensure to avoid cross labeling.</li>
	<li>Wash the secondary antibody off the tissue using approximately 500 &#181;L of 1x PBS four times for 5 min each on an orbital shaker at low RPM. Keep the 24-well plate covered to protect it from light.</li>
	<li>Prepare the larger microslide (75 mm x 25 mm) by placing two small streaks of glue along the 25 mm axis, just smaller than the 18 mm x 18 mm smaller glass coverslip. Place one drop of mounting reagent (approximately 50 &#181;L) in between the glue streaks. 
	NOTE: The glue creates a small amount of vertical space so that when the second coverslip is placed on top, the SV tissue sample can safely exist, but continue to remain in place. While the stria thickness is 30-40 microns, squeezing the tissue between the glass surfaces should be avoided to preserve morphology. Alternatively, clear tape may also be used.</li>
	<li>Using #55 forceps, grab as little tissue as possible on one end of the SV and transfer from the PBS to the drop of mounting reagent on the larger microslide (75 mm x 25 mm). Place one end of a smaller glass coverslip (18 mm x 18 mm) on the slide where one streak of glue was placed and gently release to avoid creating air bubbles. The coverslip will fall to the other glue streak and will cover the SV tissue.</li>
	<li>Seal the mount by dabbing a drop of transparent nail polish on each corner of the mount. Label the specimen accordingly on the glass coverslip away from the visualization field. It is now ready for confocal microscopy (Figure 4).</li>
	<li>Visualize the SV tissue using a dissection microscope to ensure it is laying flat and not near any air bubbles. If the SV tissue is not oriented correctly, the user can attempt to push out air bubbles or carefully remove the smaller glass coverslip and reposition the SV. This must be done gently to avoid breaking the glass coverslips.</li>
</ol>

Stria Vascularis Microdissection for Single-Nucleus Sequencing or Immunostaining

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I., 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=Expression+patterns+of+claudins,+tight+junction+adhesion+molecules,+in+the+inner+ear.">Expression patterns of claudins, tight junction adhesion molecules, in the inner ear.</a> Hearing Research. 187 (1-2), 25-34 (2004).</li><li>Jagger, D. J., Nevill, G., Forge, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+membrane+properties+of+cochlear+root+cells+are+consistent+with+roles+in+potassium+recirculation+and+spatial+buffering.">The membrane properties of cochlear root cells are consistent with roles in potassium recirculation and spatial buffering.</a> Journal of the Association for Research in Otolaryngology. 11 (3), 435-448 (2010).</li><li>Ito, T., Kurata, N., Fukunaga, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue-resident+macrophages+in+the+stria+vascularis.">Tissue-resident macrophages in the stria vascularis.</a> Frontiers in Neurology. 13, 818395 (2022).</li><li>Zhang, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=VEGFA165+gene+therapy+ameliorates+blood-labyrinth+barrier+breakdown+and+hearing+loss.">VEGFA165 gene therapy ameliorates blood-labyrinth barrier breakdown and hearing loss.</a> JCI Insight. 6 (8), e143285 (2021).</li><li>Shi, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathophysiology+of+the+cochlear+intrastrial+fluid-blood+barrier+(review).">Pathophysiology of the cochlear intrastrial fluid-blood barrier (review).</a> Hearing Research. 338, 52-63 (2016).</li><li>Gu, 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=Identification+of+potential+Meniere's+disease+targets+in+the+adult+stria+vascularis.">Identification of potential Meniere's disease targets in the adult stria vascularis.</a> Frontiers in Neurology. 12, 630561 (2021).</li><li>Fischer, J., Ayers, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single+nucleus+RNA-sequencing:+how+it's+done,+applications+and+limitations.">Single nucleus RNA-sequencing: how it's done, applications and limitations.</a> Emerging Topics in Life Sciences. 5 (5), 687-690 (2021).</li><li>Korrapati, 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=Single+cell+and+single+nucleus+RNA-Seq+reveal+cellular+heterogeneity+and+homeostatic+regulatory+networks+in+adult+mouse+stria+vascularis.">Single cell and single nucleus RNA-Seq reveal cellular heterogeneity and homeostatic regulatory networks in adult mouse stria vascularis.</a> Frontiers in Molecular Neuroscience. 12, 316 (2019).</li><li>Pyle, M. P., Hoa, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+single-cell+sequencing+for+the+field+of+otolaryngology:+A+contemporary+review.">Applications of single-cell sequencing for the field of otolaryngology: A contemporary review.</a> Laryngoscope Investigative Otolaryngology. 5 (3), 404-431 (2020).</li><li>Hwang, B., Lee, J. H., Bang, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-cell+RNA+sequencing+technologies+and+bioinformatics+pipelines.">Single-cell RNA sequencing technologies and bioinformatics pipelines.</a> Experimental &amp; Molecular Medicine. 50 (8), 1-14 (2018).</li><li>Shafer, M. E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cross-species+analysis+of+single-cell+transcriptomic+data.">Cross-species analysis of single-cell transcriptomic data.</a> Frontiers in Cell and Developmental Biology. 7, 175 (2019).</li><li>Chen, G., Ning, B., Shi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-cell+RNA-Seq+technologies+and+related+computational+data+analysis.">Single-cell RNA-Seq technologies and related computational data analysis.</a> Frontiers in Genetics. 10, 317 (2019).</li><li>Longo, S. K., Guo, M. G., Ji, A. L., Khavari, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrating+single-cell+and+spatial+transcriptomics+to+elucidate+intercellular+tissue+dynamics.">Integrating single-cell and spatial transcriptomics to elucidate intercellular tissue dynamics.</a> Nature Reviews Genetics. 22 (10), 627-644 (2021).</li><li>Kim, N., Kang, H., Jo, A., Yoo, S. A., Lee, H. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perspectives+on+single-nucleus+RNA+sequencing+in+different+cell+types+and+tissues.">Perspectives on single-nucleus RNA sequencing in different cell types and tissues.</a> Journal of Pathology and Translational Medicine. 57 (1), 52-59 (2023).</li><li>Grindberg, R. V., 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=RNA-sequencing+from+single+nuclei.">RNA-sequencing from single nuclei.</a> Proceedings of the National Academy of Sciences. 110 (49), 19802-19807 (2013).</li><li>Montgomery, S. C., Cox, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole+mount+dissection+and+immunofluorescence+of+the+adult+mouse+cochlea.">Whole mount dissection and immunofluorescence of the adult mouse cochlea.</a> Journal of Visuazlied Experiments. (107), e53561 (2016).</li></ol>

The authors have nothing to disclose.

Prior to the advent of single-cell sequencing, many researchers used bulk tissue analysis, which only made it possible to analyze transcriptomes averaged across cells. In particular, single-cell and sNuc-Seq made it possible to isolate the transcriptome of a single cell or single nucleus, respectively32. In this instance, single-nucleus transcriptomes can be identified for marginal, intermediate, and basal cells, as well as spindle cells30. This enables the investigation of...

The cochlea consists of three fluid filled chambers, the scala vestibuli, scala media, and scala tympani. The scala vestibuli and scala tympani each contain perilymph, which has a high concentration of sodium (138 mM) and a low concentration of potassium (6.8 mM)1. The scala media contains endolymph, which has a high concentration of potassium (154 mM) and a low concentration of sodium (0.91 mM)1,2,3. This difference in ion concentration can be referred to as the endocochlear potential (EP), and is primarily generated by the movement of potassium ions through various ion channels and gap junctions in the stria vascularis (SV) along the lateral wall of the cochlea4,5,6,7,8,9,10,11. The SV is a heterogenous, highly vascularized tissue that lines the medial aspect of the lateral wall of the cochlea and contains three main cell types: marginal, intermediate, and basal cells12 (Figure 1).
Marginal cells are connected by tight junctions to form the most medial surface of the SV. The apical membrane faces the endolymph of the scala media and contributes to potassium ion transport into the endolymph using various channels, including KCNE1/KCNQ1, SLC12A2, and Na+-K+-ATPase (NKA)5,10,13,14. Intermediate cells are pigmented cells that reside between marginal and basal cells and facilitate potassium transport through the SV using KCNJ10 (Kir 4.1)15,16. Basal cells lie in close proximity to the lateral wall of the cochlea and are closely associated with fibrocytes of the spiral ligament to promote potassium recycling from the perilymph12. Pathology of the SV has been implicated in numerous otologic disorders17,18. Mutations in genes expressed in the major SV cell types, such as Kcnq1, Kcne1, Kcnj10, and Cldn11, can cause deafness and SV dysfunction, including the loss of EP19,20,21,22,23. In addition to the three major cell types, there are other less-studied cell types in the SV, such as spindle cells22, root cells12,24, macrophages25, pericytes26, and endothelial cells27, that have incompletely defined roles involving ionic homeostasis and the generation of EP28.
In comparison to bulk RNA-sequencing, single-nuclei RNA-sequencing (sNuc-Seq) provides information about cell heterogeneity, rather than an average of mRNA across a group of cells29, and can be particularly useful when studying the heterogenous SV30. For example, sNuc-Seq has produced transcriptional analysis that suggests there may be a role for spindle and root cells in EP generation, hearing loss, and Meniere&#39;s disease18. Further transcriptional characterization of the various SV cell types can provide us with invaluable information on the pathophysiology underlying different mechanisms and subtypes of SV-related hearing fluctuation and hearing loss. The harvest of these delicate inner ear structures is of paramount importance to optimal tissue analysis.
In this study, the microdissection approach to access and isolate the stria vascularis from the adult mouse cochlea for sNuc-Seq or immunostaining is described. Dissection of the adult mouse SV is required to understand various SV cell types and further characterize their role in hearing.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr >
			<td >10-&#181;m filter (Polyethylenterephthalat)</td>
			<td >PluriSelect</td>
			<td >#43-50010-01</td>
			<td >Filter tissue during sNuc-Seq</td>
		</tr>
		<tr >
			<td >18 x 18 mm cover glass</td>
			<td >Fisher Scientific</td>
			<td >12-541A</td>
			<td >Cover slip to mount SV</td>
		</tr>
		<tr >
			<td >30-&#181;m filter (Polyethylenterephthalat)</td>
			<td >PluriSelect</td>
			<td >#43-50030-03</td>
			<td >Filter tissue during sNuc-Seq</td>
		</tr>
		<tr >
			<td >75 x 25 mm Superfrost Plus/Colorforst Plus Microslide</td>
			<td >Daigger</td>
			<td >EF15978Z</td>
			<td >Microslide to mount SV on</td>
		</tr>
		<tr >
			<td >C57BL/6J Mice</td>
			<td >The Jackson Laboratory</td>
			<td >RRID: IMSR_JAX:000664</td>
			<td >General purpose mouse strain that has pigment more easily seen in the intermediate cells of the SV.</td>
		</tr>
		<tr >
			<td >Cell Counter</td>
			<td >Logos Biosystems</td>
			<td >L20001</td>
			<td >Used for cell counting</td>
		</tr>
		<tr >
			<td >Chalizon curette 5&#39;&#39;, size 3 2.5 mm</td>
			<td >Biomedical Research Instruments</td>
			<td >15-1020</td>
			<td >Used to transfer SV</td>
		</tr>
		<tr >
			<td >Chromium Next GEM single Cell 3&#39; GEM Kit v3.1</td>
			<td >Chromium</td>
			<td >PN-1000141</td>
			<td >Generates single cell 3&#39; gene expression libraries</td>
		</tr>
		<tr >
			<td >Clear nail polish</td>
			<td >Fisher Scientific</td>
			<td >NC1849418</td>
			<td >Used for sealing SV mount</td>
		</tr>
		<tr >
			<td >Corning Falcon Standard Tissue Culture Dishes, 24 well</td>
			<td >Corning</td>
			<td >08-772B</td>
			<td >Culture dish used to hold specimen during dissection</td>
		</tr>
		<tr >
			<td >DAPI</td>
			<td >Invitrogen</td>
			<td >D1306, RRID: AB_2629482</td>
			<td >Stain used for nucleus labeling</td>
		</tr>
		<tr >
			<td >Dounce homogenizer</td>
			<td >Sigma-Aldrich</td>
			<td >D8938</td>
			<td >Used to homogenize tissue for sNuc-seq</td>
		</tr>
		<tr >
			<td >Dumont #5 Forceps</td>
			<td >Fine Science Tools</td>
			<td >11252-30</td>
			<td >General forceps for dissection</td>
		</tr>
		<tr >
			<td >Dumont #55 Forceps</td>
			<td >Fine Science Tools</td>
			<td >11255-20</td>
			<td >Forceps with fine tip that makes SV manipulation easier</td>
		</tr>
		<tr >
			<td >Fetal Bovine Serum</td>
			<td >ThermoFisher</td>
			<td >16000044</td>
			<td >Used for steps of sNuc-Seq</td>
		</tr>
		<tr >
			<td >Glue stick</td>
			<td >Fisher Scientific</td>
			<td >NC0691392</td>
			<td >Used for mounting SV</td>
		</tr>
		<tr >
			<td >GS-IB4 Antibody</td>
			<td >Molecular Probes</td>
			<td >I21411, RRID: AB-2314662</td>
			<td >Antibody used for capillary labeling</td>
		</tr>
		<tr >
			<td >KCNJ10-ZsGreen Mice</td>
			<td >n/a</td>
			<td >n/a</td>
			<td >Transgenic mouse that expresses KCNJ10-ZsGreen, partiularly in the intermediate cells of the SV.</td>
		</tr>
		<tr >
			<td >MgCl2</td>
			<td >ThermoFisher</td>
			<td >AM9530G</td>
			<td >Used for steps of sNuc-Seq</td>
		</tr>
		<tr >
			<td >Mounting reagent</td>
			<td >ThermoFisher</td>
			<td >#S36940</td>
			<td >Mounting reagent for SV</td>
		</tr>
		<tr >
			<td >Multiwell 24 well plate</td>
			<td >Corning</td>
			<td >#353047</td>
			<td >Plate used for immunostaining</td>
		</tr>
		<tr >
			<td >NaCl</td>
			<td >ThermoFisher</td>
			<td >AAJ216183</td>
			<td >Used for steps of sNuc-Seq</td>
		</tr>
		<tr >
			<td >Nonidet P40</td>
			<td >Sigma-Aldrich</td>
			<td >9-16-45-9</td>
			<td >Used for steps of sNuc-Seq</td>
		</tr>
		<tr >
			<td >Nuclease free water</td>
			<td >ThermoFisher</td>
			<td >4387936</td>
			<td >Used for steps of sNuc-Seq</td>
		</tr>
		<tr >
			<td >Orbital shaker</td>
			<td >Silent Shake</td>
			<td >SYC-2102A</td>
			<td >Used for steps of immunostaining</td>
		</tr>
		<tr >
			<td >PBS</td>
			<td >ThermoFisher</td>
			<td >J61196.AP</td>
			<td >Used for steps of immunostaining and dissection</td>
		</tr>
		<tr >
			<td >RNA Later</td>
			<td >Invitrogen</td>
			<td >AM7021</td>
			<td >Used for preservation of SV for sNuc-Seq</td>
		</tr>
		<tr >
			<td >Scizzors</td>
			<td >Fine Science Tools</td>
			<td >14058-09</td>
			<td >Used for splitting mouse skull</td>
		</tr>
		<tr >
			<td >Tris-HCl</td>
			<td >Sigma-Aldrich</td>
			<td >15506017</td>
			<td >Used for steps of sNuc-Seq</td>
		</tr>
		<tr >
			<td >Trypan blue stain</td>
			<td >Gibco</td>
			<td >15250061</td>
			<td >Used for cell counting</td>
		</tr>
		<tr >
			<td >Tween20</td>
			<td >ThermoFisher</td>
			<td >AAJ20605AP&#160;</td>
			<td >Used for steps of sNuc-Seq</td>
		</tr>
		<tr >
			<td >Zeiss STEMI SV 11 Apo stereomicroscope</td>
			<td >Zeiss</td>
			<td >n/a</td>
			<td >Microscope used for dissections</td>
		</tr>
	</tbody>
</table>

dissection of adult mouse stria vascularis for single-nucleus sequencing or immunostaining

Endocochlear potential, which is generated by the stria vascularis, is essential to maintain an environment conducive to appropriate hair cell mechanotransduction and ultimately hearing. Pathologies of the stria vascularis can result in a decreased hearing. Dissection of the adult stria vascularis allows for focused single-nucleus capture and subsequent single-nucleus sequencing and immunostaining. These techniques are used to study stria vascularis pathophysiology at the single-cell level. 
Single-nucleus sequencing can be used in the setting of transcriptional analysis of the stria vascularis. Meanwhile, immunostaining continues to be useful in identifying specific populations of cells. Both methods require proper stria vascularis dissection as a prerequisite, which can prove to be technically challenging.

We present a method to isolate the SV to be used for either sNuc-Seq or immunostaining. The relevant anatomy (Figure 1) of the cochlea relative to the SV can help users better understand the organization of the SV and steps of the dissection protocol.
Each step of this microdissection of SV from a P30 mouse is detailed in the associated video, and snapshots of the key steps of this dissection and isolation of SV are presented in Figure 2</stro...

Watch this Scientific Journal Video about Dissection of Adult Mouse Stria Vascularis for Single-Nucleus Sequencing or Immunostaining at JoVE.com

Author Spotlight: Dissection of Adult Mouse Stria Vascularis for Single-Nucleus Sequencing or Immunostaining  

The stria vascularis is vital to the generation of endocochlear potential. Here, we present the dissection of the adult mouse stria vascularis for single-nucleus sequencing or immunostaining.

Dissection of Adult Mouse Stria Vascularis for Single-Nucleus Sequencing or Immunostaining

Endocochlear potential, which is generated by the stria vascularis, is essential to maintain an environment conducive to appropriate hair cell ...

dissection-adult-mouse-stria-vascularis-for-single-nucleus-sequencing

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2.3K Views.  National Institutes of Health. The stria vascularis is vital to the generation of endocochlear potential. Here, we present the dissection of the adult mouse stria vascularis for single-nucleus sequencing or immunostaining.

Video: Author Spotlight: Dissection of Adult Mouse Stria Vascularis for Single-Nucleus Sequencing or Immunostaining  

Dissection of 6.5 dpc Mouse Embryos

Analysis of gene expression patterns during early stages of mammalian embryonic development can provide important clues about gene function, cell-cell interaction and signaling mechanisms that guide embryonic patterning. However, dissection of the mouse embryo from the decidua shortly after implantation can be a challenging procedure, and detailed step-by-step documentation of this process is lacking.

Here we demonstrate how post-implantation (6.5 dpc) embryos are isolated by first dissecting the uterus of a pregnant mouse (detection of the vaginal plug was designated day 0.5 poist coitum) and subsequently dissecting the embryo from maternal decidua. The dissection of Reichert's membrane is described as well as the removal of the ectoplacental cone.

Isolation of postimplantation-stage embryos allows one to study gene patterning and analyze cell-lineage decision making processes during embryonic development, but proper dissection of the early embryo can be challenging. This protocol describes a method for isolating early primitive-streak-stage embryos (~6.5 days post coitum [dpc]).

Analysis of gene expression patterns during early stages of mammalian embryonic development can provide important clues about gene function, cell-cell ...

Gross and Fine Dissection of Inner Ear Sensory Epithelia in Adult Zebrafish (Danio rerio)

Neurosensory epithelia in the inner ear are the crucial structures for hearing and balance functions. Therefore, it is important to understand the cellular and molecular features of the epithelia, which are mainly composed of two types of cells: hair cells (HCs) and supporting cells (SCs). Here we choose to study the inner ear sensory epithelia in adult zebrafish not only because the epithelial structures are highly conserved in all vertebrates studied, but also because the adult zebrafish is able to regenerate HCs, an ability that mammals lose shortly after birth. We use the inner ear of adult zebrafish as a model system to study the mechanisms of inner ear HC regeneration in adult vertebrates that could be helpful for clinical therapy of hearing/balance deficits in human as a result of HC loss.
Here we demonstrate how to do gross and fine dissections of inner ear sensory epithelia in adult zebrafish. The gross dissection removes the tissues surrounding the inner ear and is helpful for preparing tissue sections, which allows us to examine the detailed structure of the sensory epithelia. The fine dissection cleans up the non-sensory-epithelial tissues of each individual epithelium and enables us to examine the heterogeneity of the whole epithelium easily in whole-mount epithelial samples.

Gross and Fine Dissection of Inner Ear Sensory Epithelia in Adult Zebrafish Danio rerio

The inner ear sensory epithelium of adult zebrafish is a good model system for understanding the mechanisms of hair cell regeneration in adult vertebrates. This protocol demonstrates the fine dissection of the epithelia, through which we can get tissue samples for studying the regenerative events at cellular and subcellular levels.

Neurosensory epithelia in the inner ear are the crucial structures for hearing and balance functions. Therefore, it is important to understand the ...

Dissection of Hippocampal Dentate Gyrus from Adult Mouse

The hippocampus is one of the most widely studied areas in the brain because of its important functional role in memory processing and learning, its remarkable neuronal cell plasticity, and its involvement in epilepsy, neurodegenerative diseases, and psychiatric disorders. The hippocampus is composed of distinct regions; the dentate gyrus, which comprises mainly granule neurons, and Ammon's horn, which comprises mainly pyramidal neurons, and the two regions are connected by both anatomic and functional circuits. Many different mRNAs and proteins are selectively expressed in the dentate gyrus, and the dentate gyrus is a site of adult neurogenesis; that is, new neurons are continually generated in the adult dentate gyrus. To investigate mRNA and protein expression specific to the dentate gyrus, laser capture microdissection is often used. This method has some limitations, however, such as the need for special apparatuses and complicated handling procedures. In this video-recorded protocol, we demonstrate a dissection technique for removing the dentate gyrus from adult mouse under a stereomicroscope. Dentate gyrus samples prepared using this technique are suitable for any assay, including transcriptomic, proteomic, and cell biology analyses. We confirmed that the dissected tissue is dentate gyrus by conducting real-time PCR of dentate gyrus-specific genes, tryptophan 2,3-dioxygenase (TDO2) and desmoplakin (Dsp), and Ammon's horn enriched genes, Meis-related gene 1b (Mrg1b) and TYRO3 protein tyrosine kinase 3 (Tyro3). The mRNA expressions of TDO2 and Dsp in the dentate gyrus samples were detected at obviously higher levels, whereas Mrg1b and Tyro3 were lower levels, than those in the Ammon's horn samples. To demonstrate the advantage of this method, we performed DNA microarray analysis using samples of whole hippocampus and dentate gyrus. The mRNA expression of TDO2 and Dsp, which are expressed selectively in the dentate gyrus, in the whole hippocampus of alpha-CaMKII+/- mice, exhibited 0.037 and 0.10-fold changes compared to that of wild-type mice, respectively. In the isolated dentate gyrus, however, these expressions exhibited 0.011 and 0.021-fold changes compared to that of wild-type mice, demonstrating that gene expression changes in dentate gyrus can be detected with greater sensitivity. Taken together, this convenient and accurate dissection technique can be reliably used for studies focused on the dentate gyrus.

A dissection technique for removal of the dentate gyrus from adult mouse under a stereomicroscope was demonstrated in this video-recorded protocol.

The hippocampus is one of the most widely studied areas in the brain because of its important functional role in memory processing and learning, its ...

Dissection of Organs from the Adult Zebrafish

Over the last 20 years, the zebrafish has become a powerful model organism for understanding vertebrate development and disease.  Although experimental analysis of the embryo and larva is extensive and the morphology has been well documented, descriptions of adult zebrafish anatomy and studies of development of the adult structures and organs, together with techniques for working with adults are lacking. The organs of the larva undergo significant changes in their overall structure, morphology, and anatomical location during the larval to adult transition.  Externally, the transparent larva develops its characteristic adult striped pigment pattern and paired pelvic fins, while internally, the organs undergo massive growth and remodeling.  In addition, the bipotential gonad primordium develops into either testis or ovary.  This protocol identifies many of the organs of the adult and demonstrates methods for dissection of the brain, gonads, gastrointestinal system, heart, and kidney of the adult zebrafish. The dissected organs can be used for in situ hybridization, immunohistochemistry, histology, RNA extraction, protein analysis, and other molecular techniques.  This protocol will assist in the broadening of studies in the zebrafish to include the remodeling of larval organs, the morphogenesis of organs specific to the adult and other investigations of the adult organ systems.

This protocol describes a procedure for identifying and dissecting organs from the adult zebrafish.

Over the last 20 years, the zebrafish has become a powerful model organism for understanding vertebrate development and disease.  Although experimental ...

Heart Dissection in Larval, Juvenile and Adult Zebrafish, Danio rerio

Zebrafish have become a beneficial and practical model organism for the study of embryonic heart development (see recent reviews1-6), however, work examining post-embryonic through adult cardiac development has been limited7-10. Examining the changing morphology of the maturing and aging heart are restricted by the lack of techniques available for staging and isolating juvenile and adult hearts. In order to analyze heart development over the fish's lifespan, we dissect zebrafish hearts at numerous stages and photograph them for further analysis11. The morphological features of the heart can easily be quantified and individual hearts can be further analyzed by a host of standard methods. Zebrafish grow at variable rates and maturation correlates better with fish size than age, thus, post-fixation, we photograph and measure fish length as a gauge of fish maturation. This protocol explains two distinct, size dependent dissection techniques for zebrafish, ranging from larvae 3.5mm standard length (SL) with hearts of 100&mu;m ventricle length (VL), to adults, with SL of 30mm and VL 1mm or larger. Larval and adult fish have quite distinct body and organ morphology. Larvae are not only significantly smaller, they have less pigment and each organ is visually very difficult to identify. For this reason, we use distinct dissection techniques.
We used pre-dissection fixation procedures, as we discovered that hearts dissected directly after euthanization have a more variable morphology, with very loose and balloon like atria compared with hearts removed following fixation. The fish fixed prior to dissection, retain in vivo morphology and chamber position (data not shown). In addition, for demonstration purposes, we take advantage of the heart (myocardial) specific GFP transgenic Tg(myl7:GFP)twu34 (12), which allows us to visualize the entire heart and is particularly useful at early stages in development when the cardiac morphology is less distinct from surrounding tissues. Dissection of the heart makes further analysis of the cell and molecular biology underlying heart development and maturation using in situ hybridization, immunohistochemistry, RNA extraction or other analytical methods easier in post-embryonic zebrafish. This protocol will provide a valuable technique for the study of cardiac development maturation and aging.

Heart Dissection in Larval, Juvenile and Adult Zebrafish, Danio rerio

A clear, standardized method for dissection and isolation of the zebrafish heart at multiple developmental stages are described. Annotation and quantification techniques are also discussed.

Zebrafish have become a beneficial and practical model organism for the study of embryonic heart development (see recent reviews1-6), however, work ...

Single Cell Transcriptional Profiling of Adult Mouse Cardiomyocytes

While numerous studies have examined gene expression changes from homogenates of heart tissue, this prevents studying the inherent stochastic variation between cells within a tissue. Isolation of pure cardiomyocyte populations through a collagenase perfusion of mouse hearts facilitates the generation of single cell microarrays for whole transcriptome gene expression, or qPCR of specific targets using nanofluidic arrays. We describe here a procedure to examine single cell gene expression profiles of cardiomyocytes isolated from the heart. This paradigm allows for the evaluation of metrics of interest which are not reliant on the mean (for example variance between cells within a tissue) which is not possible when using conventional whole tissue workflows for the evaluation of gene expression (Figure 1). We have achieved robust amplification of the single cell transcriptome yielding micrograms of double stranded cDNA that facilitates the use of microarrays on individual cells. In the procedure we describe the use of NimbleGen arrays which were selected for their ease of use and ability to customize their design. Alternatively, a reverse transcriptase - specific target amplification (RT-STA) reaction, allows for qPCR of hundreds of targets by nanofluidic PCR. Using either of these approaches, it is possible to examine the variability of expression between cells, as well as examining expression profiles of rare cell types from within a tissue. Overall, the single cell gene expression approach allows for the generation of data that can potentially identify idiosyncratic expression profiles that are typically averaged out when examining expression of millions of cells from typical homogenates generated from whole tissues.

Single cell expression profiling allows the detailed gene expression analysis of individual cells. We describe methods for the isolation of cardiomyocytes, and preparing the resulting lysates for either whole transcriptome microarray or qPCR of specific targets.

While numerous studies have examined gene expression changes from homogenates of heart tissue, this prevents studying the inherent stochastic variation ...

Dissection of Xenopus laevis Neural Crest for in vitro Explant Culture or in vivo Transplantation

The neural crest (NC) is a transient dorsal neural tube cell population that undergoes an epithelium-to-mesenchyme transition (EMT) at the end of neurulation, migrates extensively towards various organs, and differentiates into many types of derivatives (neurons, glia, cartilage and bone, pigmented and endocrine cells). In this protocol, we describe how to dissect the premigratory cranial NC from Xenopus laevis embryos, in order to study NC development in vivo and in vitro. The frog model offers many advantages to study early development; abundant batches are available, embryos develop rapidly, in vivo gain and loss of function strategies allow manipulation of gene expression prior to NC dissection in donor and/or host embryos. The NC explants can be plated on fibronectin and used for in vitro studies. They can be cultured for several days in a serum-free defined medium. We also describe how to graft NC explants back into host embryos for studying NC migration and differentiation in vivo.

Dissection of Xenopus laevis Neural Crest for in vitro Explant Culture or in vivo Transplantation

This protocol describes how to dissect premigratory cranial neural crest (NC) from Xenopus laevis neurulas. These explants can be plated on fibronectin and cultured in vitro, or grafted back into host embryos. This technique allows studying the mechanisms of NC epithelium-to-mesenchyme transition, migration, and differentiation.

The neural crest (NC) is a transient dorsal neural tube cell population that undergoes an epithelium-to-mesenchyme transition (EMT) at the end of ...

Dissection and Immunostaining of Imaginal Discs from Drosophila melanogaster

A significant portion of post-embryonic development in the fruit fly, Drosophila melanogaster, takes place within a set of sac-like structures called imaginal discs. These discs give rise to a high percentage of adult structures that are found within the adult fly. Here we describe a protocol that has been optimized to recover these discs and prepare them for analysis with antibodies, transcriptional reporters and protein traps. This procedure is best suited for thin tissues like imaginal discs, but can be easily modified for use with thicker tissues such as the larval brain and adult ovary. The written protocol and accompanying video will guide the reader/viewer through the dissection of third instar larvae, fixation of tissue, and treatment of imaginal discs with antibodies. The protocol can be used to dissect imaginal discs from younger first and second instar larvae as well. The advantage of this protocol is that it is relatively short and it has been optimized for the high quality preservation of the dissected tissue. Another advantage is that the fixation procedure that is employed works well with the overwhelming number of antibodies that recognize Drosophila proteins. In our experience, there is a very small number of sensitive antibodies that do not work well with this procedure. In these situations, the remedy appears to be to use an alternate fixation cocktail while continuing to follow the guidelines that we have set forth for the dissection steps and antibody incubations.

Dissection and Immunostaining of Imaginal Discs from Drosophila melanogaster

The adult structures of Drosophila are derived from sac-like structures called imaginal discs. Analysis of these discs provides insight into many developmental processes including tissue determination, compartment boundary establishment, cell proliferation, cell fate specification, and planar cell polarity. This protocol is used to prepare imaginal discs for light/fluorescent microscopy.

A significant portion of post-embryonic development in the fruit fly, Drosophila melanogaster, takes place within a set of sac-like structures called ...

Analysis of LINE-1 Retrotransposition at the Single Nucleus Level

Long interspersed nuclear element-1 (Line-1 or L1) accounts for approximately 17% of the DNA present in the human genome. While the majority of L1s are inactive due to 5' truncations, ~80-100 of these elements remain retrotransposition competent and propagate to different locations throughout the genome via RNA intermediates. While older L1s are believed to target AT rich regions of the genome, the chromosomal targets of newer, more active L1s remain poorly defined. Here we describe fluorescence in situ hybridization (FISH) methodology that can be used to track patterns of L1 insertion and rates of ectopic L1 incorporation at the single nucleus level. In these experiments, fluorescein isothiocyanate/cyanine-3 (FITC/CY3) labeled neomycin probes were employed to track L1 retrotransposition in vitro in HepG2 cells stably expressing ectopic L1. This methodology prevents errors in the estimation of rates of retrotransposition posed by toxicity and account for the occurrence of multiple insertions into a single nucleus.

Here we employ FISH methodology to track LINE-1 retrotransposition at the single nuclei level in chromosome spreads of HepG2 cell lines stably expressing synthetic LINE-1.

Long interspersed nuclear element-1 (Line-1 or L1) accounts for approximately 17% of the DNA present in the human genome. While the majority of L1s are ...

Trans-inner Cell Mass Injection of Embryonic Stem Cells Leads to Higher Chimerism Rates

In an effort to increase efficiency in the creation of genetically modified mice via ES Cell methodologies, we present an adaptation to the current blastocyst injection protocol. Here we report that a simple rotation of the embryo, and injection through Trans-Inner cell mass (TICM) increased the percentage of chimeric mice from 31% to 50%, with no additional equipment or further specialized training. 26 different inbred clones, and 35 total clones were injected over a period of 9 months. There was no significant difference in either pregnancy rate or recovery rate of embryos between traditional injection techniques and TICM. Therefore, without any major alteration in the injection process and a simple positioning of the blastocyst and injecting through the ICM, releasing the ES cells into the blastocoel cavity can potentially improve the quantity of chimeric production and subsequent germline transmission.

Here we present a protocol to increase chimera production without the use of new equipment. A simple orientation change of the embryo for injection can increase the number of embryos produced, and potentially reduce the timeline to germline transmission.

In an effort to increase efficiency in the creation of genetically modified mice via ES Cell methodologies, we present an adaptation to the current ...