This research project was supported by the National Natural Science Foundation of China (82371059 (H.Z.)), the Department of Science and Technology of Sichuan Province, China (2023JDZH0002 (H.Z.)), the Chengdu Science and Technology Bureau (2022-YF05-01984-SN (H.Z.)), and Sichuan Provincial People&#39;s Hospital (30320230095 (J.Y.), 30420220062 (J.Y.)).&#160;

The procedure complied with the guidelines of the Association for Research in Vision and Ophthalmology for using animals in research and was approved by the Institutional Animal Care and Use Committee (IACUC) of Sichuan Provincial People&#39;s Hospital. C57Bl/6J male mice (2 months old) were used in this study. Figure 1 illustrates the overall procedure described here. The details of the reagents and equipment used are listed in the Table of Materials.
1. Isolation of whole-mount retinas
<ol>
	<li>Animal sacrifice
	<ol>
		<li>Sacrifice the mice using cervical dislocation (following institutionally approved protocols) (Figure 2A). Prior to cervical dislocation, 
		anesthetize the mice by inhaling isoflurane (3%-5% in oxygen) or by intraperitoneal injection of&#160;the ketamine/xylazine mixture.</li>
	</ol>
	</li>
	<li>Enucleation and eyeball processing
	<ol>
		<li>Mark the edge of the cornea on the dorsal side of the eyeball with a blue marker to remember the orientation during subsequent dissection.</li>
		<li>Remove residual muscle tissues attached to the eyeball with scissors. Transfer the enucleated eyeball to a 2 mL round-bottom microcentrifuge tube filled with 1x PBS for a brief rinse (Figure 2C).</li>
	</ol>
	</li>
	<li>Fixation
	<ol>
		<li>Transfer the eyeball to another 2 mL round-bottom microcentrifuge tube containing freshly made 4% paraformaldehyde (PFA) for fixation at 4 &#176;C for 10 min (Figure 2D).</li>
		<li>Make a small incision (approximately 1-2 mm) on the cornea using fine scissors under a dissecting microscope.</li>
		<li>Place the eyeball back into the fixative for further fixation at 4 &#176;C for 3 h to preserve tissue morphology (Figure 2D).</li>
	</ol>
	</li>
	<li>Removal of cornea and lens1,9
	<ol>
		<li>Make a small incision of approximately 1 mm around the corneal limbus, the border between the cornea and the sclera, using fine surgical scissors.</li>
		<li>Carefully cut around the circumference of the cornea, excising it entirely to expose the underlying structures.</li>
		<li>Use fine forceps to gently grasp and carefully lift the lens from the surrounding tissues to prevent damage to the retina. Maintain the structural integrity of the retina with delicate operation.</li>
		<li>Transfer the eyecup to a microcentrifuge tube for further processing. 
		NOTE: Excise the cornea and extract the lens more efficiently using the &#34;cross-slit&#34; technique10. Make two perpendicular slits across the cornea and use forceps to extract the lens.</li>
	</ol>
	</li>
	<li>Scleral incision
	<ol>
		<li>Cut a precise slit in the sclera with fine ophthalmic scissors to facilitate subsequent dissection steps (Figure 2J).</li>
	</ol>
	</li>
	<li>Retina separation
	<ol>
		<li>Insert forceps with teeth into the incision between the sclera and the retina. Gently grasp the edge of the sclera, avoiding excessive force to prevent tearing the tissue.</li>
		<li>Gradually enlarge the incision by moving the forceps along the boundary between the sclera and the retina with slow, steady hand movements. Use the toothed part of the forceps to carefully separate the sclera from the retina, ensuring the retina is not damaged (Figure 2J).</li>
	</ol>
	</li>
	<li>Retina cutting
	<ol>
		<li>Divide the retina into four roughly equal-sized flaps using sharp scissors. Ensure cuts are approximately halfway towards the optic nerve and oriented at 90&#176; from each other.</li>
	</ol>
	</li>
	<li>Retina cleaning
	<ol>
		<li>Gently unfold the dissected retina using a soft-bristled brush, and meticulously remove debris from its surface (Figure 2K).</li>
	</ol>
	</li>
	<li>Final fixation
	<ol>
		<li>Transfer the isolated retina to a microcentrifuge tube containing fresh 4% PFA using a disposable Pasteur pipette. Allow fixation on ice for an additional 5 h to overnight for tissue preservation.</li>
	</ol>
	</li>
</ol>
2. Immunostaining
<ol>
	<li>Washing
	<ol>
		<li>Wash the isolated whole-mount retina in 1x PBS with gentle agitation for 5 min. Discard the PBS solution. Repeat this process twice to remove residual fixative and debris.</li>
	</ol>
	</li>
	<li>Blocking
	<ol>
		<li>Immerse the washed retina in a blocking buffer solution (1x PBS with 4% normal donkey serum (NDS) and 0.2% Triton X-100) for 30 min to prevent nonspecific antibody binding and enhance permeabilization (Figure 3A).</li>
	</ol>
	</li>
	<li>Primary antibody incubation
	<ol>
		<li>Replace the blocking buffer with primary antibody BRN3A (diluted 1:200 in the blocking buffer). Incubate the retina overnight at 4 &#176;C to allow specific antigen-antibody binding (Figure 3B).</li>
	</ol>
	</li>
	<li>Washing
	<ol>
		<li>Wash the retina three times with 1x PBS for 5 min each to remove unbound primary antibodies and reduce background staining (Figure 3C).</li>
	</ol>
	</li>
	<li>Secondary antibody incubation
	<ol>
		<li>Incubate the retina with Alexa594- or Alexa488-conjugated anti-rabbit secondary antibody (diluted 1:300) for 2 h at room temperature to visualize target antigens (Figure 3D).</li>
	</ol>
	</li>
	<li>Washing
	<ol>
		<li>Perform three consecutive washes with 1x PBS for 5 min each to remove excess secondary antibodies and minimize nonspecific binding.</li>
	</ol>
	</li>
	<li>Mounting
	<ol>
		<li>Gently transfer the immunostained retina onto a glass microscope slide, carefully flattening it to minimize folding or distortion.</li>
		<li>Apply a small drop of anti-fade mounting medium to the center of the retina, ensuring even distribution across the tissue.</li>
		<li>Carefully position a coverslip over the mounted retina, avoiding air bubbles (Figure 3E,F).</li>
	</ol>
	</li>
</ol>
3. Image processing
NOTE: Import the image into the RGC automatic counting software and start counting. The number of BRN3A-positive cells for the entire retina can be obtained in minutes. Download the AutoCount software from GitHub (https://github.com/MOEMIL/Intelligent-quantifying-RGCs). Follow the detailed installation steps for the software below:
<ol>
	<li>Download the code from the GitHub link. One will receive a file named &#34;Intelligent-quantifying-RGCs.zip&#34;. Unzip this file.</li>
	<li>Download the necessary files from the cloud disk (see Table of Materials) and unzip them. The downloaded file is named &#34;yolov5_cpu&#34;. Unzip this package to the current folder to avoid unexpected issues.</li>
	<li>Locate the Config&#160;file from step 1 and modify its content to point to the &#34;yolov5_cpu&#34; path. 
	NOTE: For example, if the downloaded &#34;yolov5_cpu&#34; is placed in &#34;D:\1me\yolov5_cpu_&#34;, change the &#34;config.ini&#34; file in step 1 to &#34;D:/1me/yolov5_cpu&#34; (use / instead of \). (Figure 4A).</li>
	<li>Open the graphical interface by clicking on userinterface.exe. The initial loading may be slow (run as administrator) (Figure 4B).</li>
	<li>After opening the software, verify whether the &#34;pmse_plus.pt&#34; model file is present in the root directory of drive C. If it is not present, copy it to this directory. 
	NOTE: The &#34;pmse_plus.pt&#34; model file is located in the weights folder of the &#34;yolov5&#34; folder, found in the extracted Intelligent-quantifying RGCs folder (Figure 4C).</li>
	<li>Prepare the images to be detected. 
	NOTE: The software allows only one or five pictures to be read at a time. Reading more will result in an error.</li>
</ol>
4. Automated cell counting
<ol>
	<li>Open the counting software (Figure 5A).</li>
	<li>Click on OPEN IMAGE to import the image (Figure 5B).</li>
	<li>Click on RUN to allow the software to automatically count the cells (Figure 5C). 
	NOTE: The software will mark the counted cells with a red square box and display the cell count in the top right corner (Figure 5D).</li>
</ol>

Immunostaining and AI-Based Counting of RGCs in Mouse Whole-Mount Retina

<ol>
	<li>Quigley, H. A., Broman, A. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+number+of+people+with+glaucoma+worldwide+in+2010+and+2020.">The number of people with glaucoma worldwide in 2010 and 2020.</a> Br J Ophthalmol. 90 (3), 262-267 (2006).</li><li>Gallo Afflitto, G., Swaminathan, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Racial-ethnic+disparities+in+concurrent+rates+of+peripapillary+&amp;+macular+OCT+parameters+among+a+large+glaucomatous+clinical+population.">Racial-ethnic disparities in concurrent rates of peripapillary &amp; macular OCT parameters among a large glaucomatous clinical population.</a> Eye. , (2024).</li><li>Atkinson, M. 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=A+new+measure+of+patient+satisfaction+with+ocular+hypotensive+medications:+the+Treatment+Satisfaction+Survey+for+Intraocular+Pressure+(TSS-IOP).">A new measure of patient satisfaction with ocular hypotensive medications: the Treatment Satisfaction Survey for Intraocular Pressure (TSS-IOP).</a> Health Qual Life Outcomes. 1, 67 (2003).</li><li>Guo, 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=A+new+mouse-fixation+device+for+IOP+measurement+in+awake+mice.">A new mouse-fixation device for IOP measurement in awake mice.</a> Vision Res. 219, 108397 (2024).</li><li>Almasieh, M., Wilson, A. M., Morquette, B., Cueva Vargas, J. L., Di Polo, 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+molecular+basis+of+retinal+ganglion+cell+death+in+glaucoma.">The molecular basis of retinal ganglion cell death in glaucoma.</a> Prog Retin Eye Res. 31 (2), 152-181 (2012).</li><li>Jeon, C. J., Strettoi, E., Masland, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+major+cell+populations+of+the+mouse+retina.">The major cell populations of the mouse retina.</a> J Neurosci. 18 (21), 8936-8946 (1998).</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=Automatic+counting+of+retinal+ganglion+cells+in+the+entire+mouse+retina+based+on+improved+YOLOv5.">Automatic counting of retinal ganglion cells in the entire mouse retina based on improved YOLOv5.</a> Zool Res. 43 (5), 738-749 (2022).</li><li>Al-Khindi, 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=The+transcription+factor+Tbx5+regulates+direction-selective+retinal+ganglion+cell+development+and+image+stabilization.">The transcription factor Tbx5 regulates direction-selective retinal ganglion cell development and image stabilization.</a> Curr Biol. 32 (19), 4286-4298 (2022).</li><li>Claes, M., Moons, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinal+ganglion+cells:+Global+number,+density+and+vulnerability+to+glaucomatous+injury+in+common+laboratory+mice.">Retinal ganglion cells: Global number, density and vulnerability to glaucomatous injury in common laboratory mice.</a> Cells. 11 (17), 2689 (2022).</li><li>Zhang, N., Wang, Z., Lin, P., Xing, Y., Yang, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methanol-based+whole-mount+preparation+for+the+investigation+of+retinal+ganglion+cells.">Methanol-based whole-mount preparation for the investigation of retinal ganglion cells.</a> J Vis Exp. (194), e65222 (2023).</li></ol>

The authors have no conflicts to disclose.

This protocol provides a method for determining all retinal ganglion cells (RGCs) in a mouse retina, which can be used to monitor the progression of RGC degeneration in mouse models for glaucoma studies. The mouse retina is a delicate nerve tissue5, and isolating whole-mount retinas from mouse eyes requires repeated practice. During experimentation, it was found that the fixation time significantly affects retina morphology. For mice around 2 weeks of age, a fixation time of 20 min is sufficient t...

Glaucoma is characterized by&#160;the progressive death of ganglion cells, which&#160;poses a significant challenge for sight&#160;restoration1,2. This disease is a major focus of ophthalmic research due to its prevalence and impact on vision3. Mouse models are indispensable in glaucoma 
research due to&#160;their homogeneous genetic background, high&#160;reproductive capacity, and the similarity of&#160;their ganglion cell properties to humans4. The primary goal of this method is to accurately quantify retinal ganglion cells (RGCs) in mouse models, which is essential for understanding the pathogenesis of glaucoma and developing relevant treatments.
The rationale behind developing this technique stems from the need for a reliable and efficient method to assess RGC degeneration in mouse models. Traditional methods, such as labeling RGCs in retinal sections, often provide unreliable results due to the non-uniform distribution of RGCs in the retina5. Quantifying RGCs across the entire retina better reflects changes in their numbers and is crucial for evaluating disease progression and therapeutic interventions.
This method offers several advantages over alternative techniques. For instance, manual counting of retinal ganglion cells (RGCs) in a normal adult mouse retina, which contains 40,000 to 60,000 RGCs, can be time-consuming and error-prone6,7,8. The software for automatic RGC counting that we developed allows for accurate counting in less than 3 min, potentially saving researchers a significant amount of time. Additionally, the AI-based software used&#160;for automatic counting minimizes bias and&#160;enhances reproducibility.
Furthermore, this technique provides a standardized approach to assess RGC degeneration across different mouse models and experimental conditions, contributing valuable data to the field of glaucoma research. The method aligns with other studies that emphasize the importance of whole-mount retina analysis for understanding retinal changes in diseases9.
To help readers determine whether this method is suitable for their application, it is important to note that this technique is particularly advantageous for researchers studying retinal ganglion cell (RGC) degeneration in mouse models of glaucoma or other retinal diseases. The method is adaptable to various experimental setups and offers a high degree of accuracy and efficiency in RGC counting, making it ideal for both small-scale and large-scale studies. Additionally, the protocol&#39;s straightforward design and the availability of user-friendly software make it accessible to researchers with varying levels of expertise in retinal analysis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1&#215; PBS</td>
			<td>Servicebio</td>
			<td>G4202</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa594-conjugated Goat Anti-Rabbit IgG&#160; (H+L)</td>
			<td>ThermoFisher</td>
			<td>A-11012</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-BRN3A antibody [EPR23257-285]</td>
			<td>Abcam</td>
			<td>ab245230</td>
			<td></td>
		</tr>
		<tr>
			<td>AutoCount software</td>
			<td></td>
			<td></td>
			<td>https://github.com/MOEMIL/Intelligent-quantifying-RGCs</td>
		</tr>
		<tr>
			<td>Cloud disk</td>
			<td>Google drive link</td>
			<td></td>
			<td>https://drive.google.com/file/d/1yOEsBvil6KEdZFa5ENQxB6&#160;</td>
		</tr>
		<tr>
			<td>Cloud disk</td>
			<td>Baidu link</td>
			<td>Extraction code: g44k</td>
			<td>https://pan.baidu.com/s/1lccg1OVbeudsp2VtnqxWZg&#160;</td>
		</tr>
		<tr>
			<td>Marker</td>
			<td>Sharpie</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Normal Donkey Serum</td>
			<td>Biosharp, Labgic</td>
			<td>25030081</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Macklin</td>
			<td>P804536</td>
			<td></td>
		</tr>
		<tr>
			<td>ProClean 300</td>
			<td>Beyotime</td>
			<td>ST853</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>BBI, Sangon</td>
			<td>A610498</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>BioFroxx, neoFroxx</td>
			<td>1139ML100</td>
			<td></td>
		</tr>
	</tbody>
</table>

whole-mount immunostaining and automatic counting of mouse retinal ganglion cells

Glaucoma is a leading cause of blindness globally, characterized by a complex pathogenic mechanism that makes vision restoration challenging. Mice serve as valuable animal models for studying the pathogenesis and treatment of glaucoma due to their relatively homogenous genetic background and retinal ganglion cells (RGCs), which structurally resemble those in humans. Accurate assessment of RGC damage and treatment outcomes in mouse glaucoma models requires determining the RGC number across the entire retina. This protocol outlines a comprehensive method involving the isolation of the whole retina, labeling RGCs with specific antibodies, and rapid, accurate automatic counting of RGCs using an AI-based program. The streamlined approach allows for efficient and precise quantification of RGC numbers in mouse retinas, facilitating the evaluation of RGC degeneration and potential therapeutic interventions. By enabling researchers to assess the extent of RGC damage, this protocol contributes to a deeper understanding of glaucoma pathogenesis and aids in developing effective treatment strategies to manage and prevent vision loss.

This protocol details the methodology for whole-mount immunostaining of mouse retinas, ensuring meticulous tissue preparation, precise antibody incubation, and reliable automated cell counting. The procedure facilitates robust labeling and quantification of retinal ganglion cells (RGCs), enabling accurate assessment of cellular populations in various experimental contexts. The method was used to count RGCs in wild-type and glaucoma-modeled mice, yielding consistent results. A representative result shows that the number o...

Author Spotlight: Efficient Retinal Ganglion Cell Counting in Mouse Models of Glaucoma for Treatment Evaluation

This protocol describes the procedure for isolating the whole-mount mouse retina and performing immunostaining to label all retinal ganglion cells (RGCs). The process is followed by imaging and automatically counting RGCs using AI-based software, providing a simple, fast, and accurate method for quantifying RGCs in the entire mouse retina.

Whole-Mount Immunostaining and Automatic Counting of Mouse Retinal Ganglion Cells

Glaucoma is a leading cause of blindness globally, characterized by a complex pathogenic mechanism that makes vision restoration challenging. Mice serve ...

Our research scope is to use the mouse as an animal model for studies of glaucoma. To precise assess the disease condition of glaucoma in the mouse retina, we need to determine how many retinal ganglion cells are in the retina. There around the 50, 000 retinal ganglion cells in an entire mouse retina.If we count them manually, it may take up to eight to 10 hours. Automatic counting methods can get it done in minutes and save people lots of time and effort. In the future, our lab will focus on glaucoma treatment study.We are going to use different mouse models for glaucoma to test a variety of treatment methods. The method described in this protocol is particularly useful for treatment evaluation.

whole-mount-immunostaining-automatic-counting-mouse-retinal-ganglion

Research

JoVE Journal

Neuroscience

760 Views.  University of Electronic Science and Technology of China. Our research scope is to use the mouse as an animal model for studies of glaucoma. To precise assess the disease condition of glaucoma in the mouse retina, we need to determine how many retinal ganglion cells are in the retina. There around the 50, 000 retinal ganglion cells in an entire mouse retina.If we count them manually, it may take up to eight to 10 hours. Automatic counting methods can get it done in minutes and save people lots of time and effort. In the future, our lab will f...

Video: Author Spotlight: Efficient Retinal Ganglion Cell Counting in Mouse Models of Glaucoma for Treatment Evaluation

Dissection of a Mouse Eye for a Whole Mount of the Retinal Pigment Epithelium

The retinal pigment epithelium (RPE) lies at the back of the mammalian eye, just under the neural retina, which contains the photoreceptors (rods and cones). The RPE is a monolayer of pigmented cuboidal cells and associates closely with the neural retina just above it. This association makes the RPE of great interest to researchers studying retinal diseases. The RPE is also the site of an in vivo assay of homology-directed DNA repair, the pun assay. The mouse eye is particularly difficult to dissect due to its small size (about 3.5mm in diameter) and its spherical shape. This article demonstrates in detail a procedure for dissection of the eye resulting in a whole mount of the RPE. In this procedure, we show how to work with, rather than against, the spherical structure of the eye. Briefly, the connective tissue, muscle, and optic nerve are removed from the back of the eye. Then, the cornea and lens are removed. Next, strategic cuts are made that result in significant flattening of the remaining tissue. Finally, the neural retina is gently lifted off, revealing an intact RPE, which is still attached to the underlying choroid and sclera. This whole mount can be used to perform the pun assay or for immunohistochemistry or immunofluorescent assessment of the RPE tissue.

A formal demonstration of the dissection of a mouse eye, resulting in a whole mount of the retinal pigment epithelium.

The retinal pigment epithelium (RPE) lies at the back of the mammalian eye, just under the neural retina, which contains the photoreceptors (rods and ...

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

The targeting and refinement of RGC projections to the midbrain is a popular and powerful model system for studying how precise patterns of neural connectivity form during development. In mice, retinofugal projections are arranged in a topographic manner and form eye-specific layers in the Lateral Geniculate Nucleus (dLGN) of the thalamus and the Superior Colliculus (SC). The development of these precise patterns of retinofugal projections has typically been studied by labeling populations of RGCs with fluorescent dyes and tracers, such as horseradish peroxidase1-4. However, these methods are too coarse to provide insight into developmental changes in individual RGC axonal arbor morphology that are the basis of retinotopic map formation. They also do not allow for the genetic manipulation of RGCs.
Recently, electroporation has become an effective method for providing precise spatial and temporal control for delivery of charged molecules into the retina5-11. Current retinal electroporation protocols do not allow for genetic manipulation and tracing of retinofugal projections of a single or small cluster of RGCs in postnatal mice. It has been argued that postnatal in vivo electroporation is not a viable method for transfecting RGCs since the labeling efficiency is extremely low and hence requires targeting at embryonic ages when RGC progenitors are undergoing differentiation and proliferation6. 
In this video we describe an in vivo electroporation protocol for targeted delivery of genes, shRNA, and fluorescent dextrans to murine RGCs postnatally. This technique provides a cost effective, fast and relatively easy platform for efficient screening of candidate genes involved in several aspects of neural development including axon retraction, branching, lamination, regeneration and synapse formation at various stages of circuit development. In summary we describe here a valuable tool which will provide further insights into the molecular mechanisms underlying sensory map development.

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

We demonstrate an in vivo electroporation protocol for transfecting single or small clusters of retinal ganglion cells (RGCs) and other retinal cell types in postnatal mice over a wide range of ages. The ability to label and genetically manipulate postnatal RGCs in vivo is a powerful tool for developmental studies.

The targeting and refinement of RGC projections to the midbrain is a popular and powerful model system for studying how precise patterns of neural ...

Implementing Dynamic Clamp with Synaptic and Artificial Conductances in Mouse Retinal Ganglion Cells

Ganglion cells are the output neurons of the retina and their activity reflects the integration of multiple synaptic inputs arising from specific neural circuits. Patch clamp techniques, in voltage clamp and current clamp configurations, are commonly used to study the physiological properties of neurons and to characterize their synaptic inputs. Although the application of these techniques is highly informative, they pose various limitations. For example, it is difficult to quantify how the precise interactions of excitatory and inhibitory inputs determine response output. To address this issue, we used a modified current clamp technique, dynamic clamp, also called conductance clamp 1, 2, 3 and examined the impact of excitatory and inhibitory synaptic inputs on neuronal excitability. This technique requires the injection of current into the cell and is dependent on the real-time feedback of its membrane potential at that time. The injected current is calculated from predetermined excitatory and inhibitory synaptic conductances, their reversal potentials and the cell's instantaneous membrane potential. Details on the experimental procedures, patch clamping cells to achieve a whole-cell configuration and employment of the dynamic clamp technique are illustrated in this video article. Here, we show the responses of mouse retinal ganglion cells to various conductance waveforms obtained from physiological experiments in control conditions or in the presence of drugs. Furthermore, we show the use of artificial excitatory and inhibitory conductances generated using alpha functions to investigate the responses of the cells.

This video article illustrates the set-up, the procedures to patch cell bodies and how to implement dynamic clamp recordings from ganglion cells in whole-mount mouse retinae. This technique allows the investigation of the precise contribution of excitatory and inhibitory synaptic inputs, and their relative magnitude and timing to neuronal spiking.

Ganglion cells are the output neurons of the  retina and their activity reflects the integration of multiple synaptic inputs  arising from specific neural ...

Whole-mount Imaging of Mouse Embryo Sensory Axon Projections

The visualization of full-length neuronal projections in embryos is essential to gain an understanding of how mammalian neuronal networks develop. Here we describe a method to label in situ a subset of dorsal root ganglion (DRG) axon projections to assess their phenotypic characteristics using several genetically manipulated mouse lines. The TrkA-positive neurons are nociceptor neurons, dedicated to the transmission of pain signals. We utilize a TrkAtaulacZ mouse line to label the trajectories of all TrkA-positive peripheral axons in the intact mouse embryo. We further breed the TrkAtaulacZ line onto a Bax null background, which essentially abolishes neuronal apoptosis, in order to assess growth-related questions independently of possible effects of genetic manipulations on neuronal survival. Subsequently, genetically modified mice of interest are bred with the TrkAtaulacZ/Bax null line and are then ready for study using the techniques described herein. This presentation includes detailed information on mouse breeding plans, genotyping at the time of dissection, tissue preparation, staining and clearing to allow for visualization of full-length axonal trajectories in whole-mount preparation.

We present here an optimized protocol to genotype, stain and prepare fetal mice for the imaging of peripheral nociceptor axon projections in the whole animal, as an effective method to assess sensory axon growth phenotypes in developing genetically engineered mice.

The visualization of full-length neuronal projections in embryos is essential to gain an understanding of how mammalian neuronal networks develop. Here we ...

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 ...

Single-cell RNA-Seq of Defined Subsets of Retinal Ganglion Cells

The discovery of cell type-specific markers can provide insight into cellular function and the origins of cellular heterogeneity. With a recent push for the improved understanding of neuronal diversity, it is important to identify genes whose expression defines various subpopulations of cells. The retina serves as an excellent model for the study of central nervous system diversity, as it is composed of multiple major cell types. The study of each major class of cells has yielded genetic markers that facilitate the identification of these populations. However, multiple subtypes of cells exist within each of these major retinal cell classes, and few of these subtypes have known genetic markers, although many have been characterized by morphology or function. A knowledge of genetic markers for individual retinal subtypes would allow for the study and mapping of brain targets related to specific visual functions and may also lend insight into the gene networks that maintain cellular diversity. Current avenues used to identify the genetic markers of subtypes possess drawbacks, such as the classification of cell types following sequencing. This presents a challenge for data analysis and requires rigorous validation methods to ensure that clusters contain cells of the same function. We propose a technique for identifying the morphology and functionality of a cell prior to isolation and sequencing, which will allow for the easier identification of subtype-specific markers. This technique may be extended to non-neuronal cell types, as well as to rare populations of cells with minor variations. This protocol yields excellent-quality data, as many of the libraries have provided read depths greater than 20 million reads for single cells. This methodology overcomes many of the hurdles presented by Single-cell RNA-Seq and may be suitable for researchers aiming to profile cell types in a straightforward and highly efficient manner.

Here, we present a combinatorial approach for classifying neuronal cell types prior to isolation and for the subsequent characterization of single-cell transcriptomes. This protocol optimizes the preparation of samples for successful RNA Sequencing (RNA-Seq) and describes a methodology designed specifically for the enhanced understanding of cellular diversity.

The discovery of cell type-specific markers can provide insight into cellular function and the origins of cellular heterogeneity. With a recent push for ...

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

Structural changes in the retina are common manifestations of ophthalmic diseases. Optical coherence tomography (OCT) enables their identification in vivo&#8212;rapidly, repetitively, and at a high resolution. This protocol describes OCT imaging in the mouse retina as a powerful tool to study optic neuropathies (OPN). The OCT system is an interferometry-based, non-invasive alternative to common post mortem histological assays. It provides a fast and accurate assessment of retinal thickness, allowing the possibility to track changes, such as retinal thinning or thickening. We present the imaging process and analysis with the example of the Opa1delTTAG mouse line. Three types of scans are proposed, with two quantification methods: standard and homemade calipers. The latter is best for use on the peripapillary retina during radial scans; being more precise, is preferable for analyzing thinner structures. All approaches described here are designed for retinal ganglion cells (RGC) but are easily adaptable to other cell populations. In conclusion, OCT is efficient in mouse model phenotyping and has the potential to be used for the reliable evaluation of therapeutic interventions.

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

This manuscript describes a protocol for the in vivo imaging of the mouse retina with high-resolution spectral domain optical coherence tomography (SD-OCT). It focuses on retinal ganglion cells (RGC) in the peripapillary region, with several scanning and quantifying approaches described.

Structural changes in the retina are common manifestations of ophthalmic diseases. Optical coherence tomography (OCT) enables their identification in ...

Immunostaining of Whole-Mount Retinas with the CLARITY Tissue Clearing Method

The tissue hydrogel delipidation method (CLARITY), originally developed by the Deisseroth laboratory, has been modified and widely used for immunostaining and imaging of thick brain samples. However, this advanced technology has not yet been used for whole-mount retinas. Although the retina is partially transparent, its thickness of approximately 200 &#181;m (in mice) still limits the penetration of antibodies into the deep tissue as well as reducing light penetration for high-resolution imaging. Here, we adapted the CLARITY method for whole-mount mouse retinas by polymerizing them with an acrylamide monomer to form a nanoporous hydrogel and then clearing them in sodium dodecyl sulfate to minimize protein loss and avoid tissue damage. CLARITY-processed retinas were immunostained with antibodies for retinal neurons, glial cells, and synaptic proteins, mounted in a refractive index matching solution, and imaged. Our data demonstrate that CLARITY&#160;can improve the quality of standard immunohistochemical staining and imaging for retinal neurons and glial cells in whole-mount preparation. For instance, 3D resolution of fine axon-like and dendritic structures of dopaminergic amacrine cells were much improved by CLARITY. Compared to non-processed whole-mount retinas, CLARITY can reveal immunostaining for synaptic proteins such as postsynaptic density protein 95. Our results show that CLARITY renders the retina more optically transparent after the removal of lipids and preserves fine structures of retinal neurons and their proteins, which can be routinely used for obtaining high-resolution imaging of retinal neurons and their subcellular structures in whole-mount preparation.

Here we present a protocol to adapt the CLARITY method of the brain tissues for whole-mount retinas to improve the quality of standard immunohistochemical staining and high-resolution imaging of retinal neurons and their subcellular structures.

The tissue hydrogel delipidation method (CLARITY), originally developed by the Deisseroth laboratory, has been modified and widely used for immunostaining ...

Quantification of Vascular Parameters in Whole Mount Retinas of Mice with Non-Proliferative and Proliferative Retinopathies

Retinopathies are a heterogeneous group of diseases that affect the neurosensory tissue of the eye. They are characterized by neurodegeneration, gliosis&#160;and a progressive change in vascular function and structure. Although the onset of the retinopathies is characterized by subtle disturbances in visual perception, the modifications in the vascular plexus are the first signs detected by clinicians. The absence or presence of neovascularization determines whether the retinopathy is classified as either non-proliferative (NPDR) or proliferative (PDR). In this sense, several animal models tried to mimic specific vascular features of each stage to determine the underlying mechanisms involved in endothelium alterations, neuronal death and other events taking place in the retina. In this article, we will provide a complete description of the procedures required for the measurement of retinal vascular parameters in adults and early birth mice at postnatal day (P)17. We will detail the protocols to carry out retinal vascular staining with Isolectin GSA-IB4 in whole mounts for later microscopic visualization. Key steps for image processing with Image J Fiji software are also provided, therefore, the readers will be able to measure vessel density, diameter and tortuosity, vascular branching, as well as avascular and neovascular areas. These tools are highly helpful to evaluate and quantify vascular alterations in both non-proliferative and proliferative retinopathies.

This article describes a well-established and reproducible lectin stain assay for the whole mount retinal preparations and the protocols required for the quantitative measurement of vascular parameters frequently altered in proliferative and non-proliferative retinopathies.

Retinopathies are a heterogeneous group of diseases that affect the neurosensory tissue of the eye. They are characterized by neurodegeneration, ...

Mouse Retina Isolation and Methanol Treatment for Studying Retinal Ganglion Cells

Methanol-Based Whole-Mount Preparation for the Investigation of Retinal Ganglion Cells

Retinal ganglion cells (RGCs), which are the projection neurons of the retina, propagate external visual information to the brain. Pathological changes in RGCs have a close relationship with numerous retinal degenerative diseases. Whole-mount retinal immunostaining is frequently used in experimental studies on RGCs to evaluate the developmental and pathological conditions of the retina. Under some circumstances, some valuable retina samples, such as those from transgenic mice, may need to be retained for a long period without affecting the morphology or number of RGCs. For credible and reproducible experimental results, using an effective preserving medium is essential. Here, we describe the effect of methanol as an auxiliary fixed medium for retinal whole-mount preparations and long-term storage. In brief, during the isolation process, cold methanol (&#8722;20 &#176;C) is pipetted onto the surface of the retina to help fix the tissues and facilitate their permeability, and then the retinas can be stored in cold methanol (&#8722;20 &#176;C) before being immunostained. This protocol describes the retina isolation workflow and tissue sample storage protocol, which is useful and practical for the investigation of RGCs.

Author Spotlight: Methanol-Based Whole-Mount Preparation for the Investigation of Retinal Ganglion Cells  

Methanol can be used as an auxiliary fixed medium for retinal whole-mount preparations and long-term storage, which is useful for the investigation of retinal ganglion cells.

Retinal ganglion cells (RGCs), which are the projection neurons of the retina, propagate external visual information to the brain. Pathological changes in ...