Name: a simple one-step dissection protocol for whole-mount preparation of adult drosophila brains
Uploaded: 2016-12-01T13:30:00
Description: Watch this Scientific Journal Video about A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains at JoVE.com

We acknowledge Mr. Enes Mehmet, Ms. Kiara Andrade, Ms. Pilar Rodriguez, Chris Kwok, and Ms. Danna Ghafir for their immense support to the project.

1. Solutions Used for Brain Dissection and Immunofluorescent Staining
<ol>
	<li>Dissect the adult fly brains in artificial Cerebral Spinal Fluid (aCSF): 119 mM NaCl, 26.2 mM NaHCO3, 2.5 mM KCl, 1 mM NaH2PO4, 1.3 mM MgCl2, and 10 mM glucose. Before use, gas the aCSF with 5% CO2/95% O2 for 10 - 15 min and spike with 2.5 mM CaCl2. Sterilize the aCSF solution by filtering through a 0.22 &#181;m membrane filter. 
	Note: Store ...

<ol>
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S., Luo, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+protocol+for+dissecting+Drosophila+melanogaster+brains+for+live+imaging+or+immunostaining.">A protocol for dissecting Drosophila melanogaster brains for live imaging or immunostaining.</a> Nat Protoc. 1, 2110-2115 (2006).</li><li>Mao, Z., Davis, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eight+different+types+of+dopaminergic+neurons+innervate+the+Drosophila+mushroom+body+neuropil:+anatomical+and+physiological+heterogeneity.">Eight different types of dopaminergic neurons innervate the Drosophila mushroom body neuropil: anatomical and physiological heterogeneity.</a> Front Neural Circuits. 3, 5 (2009).</li><li>White, K. E., Humphrey, D. 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H., Kim, J., Kim, H., Yim, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glutathione+s-transferase+omega+1+activity+is+sufficient+to+suppress+neurodegeneration+in+a+Drosophila+model+of+Parkinson+disease.">Glutathione s-transferase omega 1 activity is sufficient to suppress neurodegeneration in a Drosophila model of Parkinson disease.</a> J Biol Chem. 287, 6628-6641 (2012).</li></ol>

With an increasing interest in using adult Drosophila brain to study human brain diseases, neuronal circuitry, and higher brain functions, it is necessary to develop simple and quick methods to obtain intact fly brains for whole-mount analyses, which is especially important for large-scale brain-based screens. Our method provides a simple and easy-to-learn approach to dissect out a fly head (often in less than 10 s&#160;with experience) with well-preserved morphology that is largely cleared of associated tissues...

The model organism Drosophila, commonly known as the fruit fly, has long been valued for its elegant genetic tools, short reproductive times, and highly conserved molecular and cellular pathways. The fruit fly has been successfully employed to dissect basic signaling pathways, the patterning mechanisms of multicellular organisms, as well as the mechanisms underlying neuronal development, functions, and diseases1,2. With recent advances in cell labeling and imaging technologies, the fruit fly brain has become especially powerful in fine mapping of neuronal circuitry and in dissecting the molecular and cellular basis of higher brain functions, such as learning and memory, and circadian rhythm1,3,4,5,6,7,8.
One particular advantage of the Drosophila system is its relatively small size, allowing whole-mount preparation and examination of the brain using a regular compound or confocal microscope. This feature enables detailed anatomic and functional analyses of neuronal circuitry, or even a single neuron, at cellular and subcellular levels, in the context of a whole brain tissue, thus providing both a holistic view of the studied subject and its exact geometry within the whole brain. However, given the rather miniature size of the brain, it also presents a technical challenge in efficiently dissecting an intact brain tissue out of the protective exoskeleton head case in an adult fly. Various effective and relatively simple dissection methods have been described in detail, which usually involve careful and step-wise removal of the head case and the associated tissues including the eyes, trachea, and fat from the brain proper9, 10. These microsurgical dissection methods often place rather stringent demands on the quality of the dissection forceps, relying on forceps with fine well-aligned tips that can be easily damaged. Moreover, as the dissected brains are often separated from the rest of the body, the brains can be easily lost during the subsequent staining and washing processes because of their small sizes and their transparency in the processing buffer. Here, we describe a relatively simple and easy-to-learn, one-step dissection protocol for adult brains that keeps the dissected brains attached to the torso. The dissection process often easily clears away most of the brain-associated tissues such as the eye and trachea and reduces the demand for good quality dissection forceps.
Additionally, when imaging the brain under the fluorescent compound microscope or confocal microscope, the side of the brain that is away from the fluorescent light source often produces a weaker signal and less clear images due to the thickness of the whole-mount brain. Here, we also describe a simple mounting method that allows easy flipping of the brain samples, enabling convenient imaging of both sides of the brain with similar signal intensity and quality.
As a proof-of-concept for the application of this method to study the adult brain, we further examined the presence of DA neurons in the brains of w1118 flies; a genotype that is often used as the parental line for generating transgenic flies and the wildtype control in many Drosophila studies.

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			<td height="54" style="height:54px;width:573px;">w*;&#160;park&#916;21/TM3,&#160;P{GAL4-Kr.C}DC2,&#160;P{UAS-GFP.S65T}DC10,&#160;Sb1</td>
			<td style="width:311px;">Bloomington Drosophila Stock Center</td>
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			<td style="width:287px;">Balancer was switched to TM6B</td>
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			<td>Exelixis at Harvard Medical School</td>
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			<td>Balancer was switched to TM6C</td>
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			<td>02-003-265</td>
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			<td>Replaces glucose</td>
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			<td>GVWP14250</td>
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			<td height="21" style="height:21px;width:573px;">Formalin Solution, 10% (Histological)</td>
			<td style="width:311px;">Fisher Scientific</td>
			<td>SF98-20</td>
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			<td height="21" style="height:21px;width:573px;">Potassium Phosphate, Dibasic, Powder, Ultrapure Bioreagent</td>
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			<td>02-003-823</td>
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			<td height="21" style="height:21px;width:573px;">Tween 20</td>
			<td style="width:311px;">Fisher Scientific</td>
			<td>BP337-500</td>
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			<td height="21" style="height:21px;width:573px;">Excelta Precision Tweezers with Very Fine Points</td>
			<td style="width:311px;">Fisher Scientific</td>
			<td>17-456-055</td>
			<td>Protocol does not require very fine points.&#160;</td>
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			<td height="21" style="height:21px;width:573px;">Anti-Tyrosine Hydroxylase Antibody</td>
			<td>Pel-Freez Biologicals</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:573px;">Rat-Elav-7E8A10 anti-elav</td>
			<td>The Developmental Studies Hybridoma Bank</td>
			<td>Clone 7E8A10</td>
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			<td height="21" style="height:21px;width:573px;">Goat anti-Rat IgG (H+L) Secondary Antibody, Alexa Fluor 647 conjugate</td>
			<td style="width:311px;">ThermoFisher Scientific</td>
			<td style="width:151px;">A-21247</td>
			<td></td>
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			<td height="21" style="height:21px;width:573px;">Goat anti-Rabbit IgG (H+L) Secondary Antibody, Alexa Fluor 594 conjugate</td>
			<td style="width:311px;">ThermoFisher Scientific</td>
			<td style="width:151px;">A-11037</td>
			<td></td>
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			<td height="21" style="height:21px;width:573px;">DAPI Solution (1 mg/mL)</td>
			<td style="width:311px;">ThermoFisher Scientific</td>
			<td style="width:151px;">62248</td>
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			<td height="21" style="height:21px;">Propyl gallate powder</td>
			<td style="width:311px;">Sigma-Aldrich</td>
			<td>P3130-100G</td>
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			<td height="21" style="height:21px;width:573px;">Glycerol ACS reagent, &#8805;99.5%</td>
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			<td height="21" style="height:21px;">Zeiss Axioimager Z1</td>
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			<td style="width:151px;">Quote</td>
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			<td height="21" style="height:21px;width:573px;">Zeiss Apotome.2</td>
			<td style="width:311px;">Zeiss</td>
			<td style="width:151px;">Quote</td>
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			<td height="21" style="height:21px;width:573px;">Zen lite software</td>
			<td style="width:311px;"></td>
			<td style="width:151px;">Quote</td>
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a simple one-step dissection protocol for whole-mount preparation of adult drosophila brains

There is an increasing interest in using Drosophila to model human brain degenerative diseases, map neuronal circuitries in adult brains, and study the molecular and cellular basis of higher brain functions. A whole-mount preparation of adult brains with well-preserved morphology is critical for such whole brain-based studies, but can be technically challenging and time-consuming. This protocol describes an easy-to-learn, one-step dissection approach of an adult fly head in less than 10 s, while keeping the intact brain attached to the rest of the body to facilitate subsequent processing steps. The procedure helps remove most of the eye and tracheal tissues normally associated with the brain that can interfere with the later imaging step, and also places less demand on the quality of the dissecting forceps. Additionally, we describe a simple method that allows convenient flipping of the mounted brain samples on a coverslip, which is important for imaging both sides of the brains with similar signal intensity and quality. As an example of the protocol, we present an analysis of dopaminergic (DA) neurons in adult brains of WT (w1118) flies. The high efficacy of the dissection method makes it particularly useful for large-scale adult brain-based studies in Drosophila.

Figure 1 illustrates the main procedures for adult brain dissection, as described above. Figures 2 and 3 are representative images of 3-day-old WT (genotype: w1118) adult fly brains, which were costained with an antibody against Tyrosine Hydroxylase (TH, colored in red in Figure 2 and white in Figure 3), a marker commonly used to label DA neurons11, in addition to the DNA dy...

Watch this Scientific Journal Video about A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains at JoVE.com

A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains

The adult Drosophila brain is a valuable system for studying neuronal circuitry, higher brain functions, and complex disorders. An efficient method to dissect whole brain tissue from the small fly head will facilitate brain-based studies. Here we describe a simple, one-step dissection protocol of adult brains with well-preserved morphology.

A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains

There is an increasing interest in using Drosophila to model human brain degenerative diseases, map neuronal circuitries in adult brains, and study the ...

The overall goal of this protocol is to describe a simple one step dissection procedure for adult Drosophila brains, which can quickly produce brains with well preserved morphology suitable for whole mount analysis. This method can help answer questions in the fields of neuroscience and genetics. This includes fine mapping of brain circuitries, studying the effects of genetic manipulations of neurons, and functional characterization of genes.The main advantage of this technique is that it involves an easy to learn procedure. It can facilitate in dissecting out an adult fly brain with well preserved morphology in less than 10 seconds. Video demonstration of this method is critical, as controlling the required momentum when releasing the forceps to tear away the exoskeleton surrounding the fly head takes skills and practice.These tiny, annoying fruit flies have taught us a lot about the biological principles. They may also help us find the causes and the cures for human diseases, such as Alzheimer's disease, and Parkinson's disease. Using a dissecting microscope set to 1.2 X magnification, immobilize an anesthetized fly and immerse it into cold dissection solution with the abdomen facing upwards.Keep the forceps at a 160 to 170 degree angle respective to the dissection plate, and then exert a small force onto the abdomen of the fly. This should immobilize the fly, force the head backwards 15 to 25 degrees, and extend the proboscis upwards. After this maneuver, a soft translucent region of the cuticle underneath the proboscis should become apparent.Increase the magnification and adjust the focal plane onto this region. Using the dominant hand, take a pair of dissecting forceps and exert pressure to close the tips. Position the forceps perpendicularly to the forceps restraining the fly.Pierce the closed tips of the forceps through the soft translucent region of the cuticle, taking care not to penetrate so deeply that they touch the brain. Then quickly, but steadily, release the forceps, so that the points open, tearing away the exoskeleton of the fly head. Use the momentum from releasing the forceps tips to gently remove the exoskeleton and most of the head case associated eye and trachea from the brain tissue in one motion.An intact brain should now be visible. Using the forceps, carefully remove the remaining accessory tissues, such as the white fibrous tracheal tissue, taking care not to pull or damage the brain proper. Place the dissected brain samples with associated torsos into approximately one milliliter of 4%paraformaldehyde on ice for 40 to 60 minutes.Remove the paraformaldehyde, and then rinse the samples with one milliliter of one X PBS by pipetting the solution up and down three times, taking care not to aspirate the brains. Next, remove the PBS and then wash five times with one milliliter of one X PBT for five minutes each with nutation. Add the primary antibody of interest at the appropriate dilution.And then incubate the samples overnight at four degrees Celsius with nutation. Remove the primary antibody and wash the samples five times with one milliliter of one X PBT for five to 10 minutes each wash with nutation. Add secondary antibody to the washed samples at the appropriate dilution and incubation time.Following this, wash the samples six times in one milliliter of one X PBT for 10 minutes each with nutation. This step is critical to remove any non-specifically bound secondary antibodies. Incubate the samples in a one to 10, 000 dilution of one milligram per milliliter DAPI in one milliliter of one X PBT solution for 30 to 60 minutes with nutation.Finally, rinse the samples by adding one milliliter of one X PBS and then pipetting the solution up and down three times. Place a cover slip onto a mounting slide. Using a pipette with a cut tip, transfer the brains in one X PBS solution onto the coverslip.Next, using forceps, separate the brains from the bodies. Use a fine pipette tip to remove the liquid around the brain tissue. And then, add 20 to 40 microliters of anti-fade mounting medium.Gently spread the brains, whilst displacing the viscous medium outwards. Beginning at one side, gently lower a second coverslip onto the samples, taking care to minimize brain contact with bubbles. Allow the slips to settle, and then remove any excess liquid from the edge of the slips using a laboratory wipe.Use a small piece of tape to temporarily attach the coverslip pair to the mounting slide. To image the samples, use a compound fluorescent or confocal microscope. These images show anterior and posterior views of the same adult Drosophila.Cell nuclei were visualized by DAPI staining and neurons were labeled using a pan neuronal marker and anti-ELAV antibodies. Dopaminergic, or DA, neurons were revealed by anti-TH antibody stain. Similar levels of intensity were seen between both sides of the brain for all image channels.Enlarged views of the anterior and posterior of the brain allow detailed examination of the DA neuronal clusters. The paired anterior medial cluster can be seen in the anterior images, and the paired posterior medial and paired posterior lateral clusters in the posterior side of the brain. Quantification of these neurons revealed that three day old male w1118 strain flies typically have 27 DA neurons in the PPM cluster in the whole brain, 16 in the PPL cluster per hemisphere, and five in the PAL cluster per hemisphere.An average of 97 DA neurons was seen in each of the PAM clusters. 3D reconstruction of the PAL and PAM clusters also showed that the DA neurons in the PAM cluster have relatively small sizes and weaker TH staining than those in the other clusters, such as the PAL. Increasingly, more studies are focusing on adult fly brains for dissecting molecular pathways and neuronal circuitry underlying higher brain functions, and for modeling human brain diseases.In such brain based studies it will be necessary to efficiently prepare brain samples with well preserved morphology. This could be especially important in large scale brain based screens. I first had the idea for this method when struggling to hold flies in the forceps.Instead of forceps with sharp tips that most Drosophila researchers use, Shebna tried blunt end forceps and found that it was easier to dissect the brains. Once mastered, this technique can be done in less than 10 seconds if it is performed properly. Once, I dissected about 100 brains of six different genotype for one experiment in just one day.While this dissection procedure may look simple, it's important to practice it first with dispensable flies. The investigator may also struggle with positioning the forceps without destroying the fly brain. The dissected brains can be used for other studies, like RNA, in situ hybridization, and extraction of protein and RNA sample from brain tissue.After watching this video, you should be able to dissect fly brains with well preserved morphology. We predict that improvements can be developed to make this procedure simpler and faster. This can potentially become automated in the future for large scale studies.Don't forget that working with the paraformaldehyde and the sharp dissecting forceps can be hazardous. Take precautions, such as wearing gloves, when handling fixative solutions, and once the dissection is complete immediately cap the forceps before putting them aside.

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Neuroscience

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

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

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

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

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

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 ...

Single Drosophila Ommatidium Dissection and Imaging

The fruit fly Drosophila melanogaster has made invaluable contributions to neuroscience research and has been used widely as a model for neurodegenerative diseases because of its powerful genetics1. The fly eye in particular has been the organ of choice for neurodegeneration research, being the most accessible and life-dispensable part of the Drosophila nervous system. However the major caveat of intact eyes is the difficulty, because of the intense autofluorescence of the pigment, in imaging intracellular events, such as autophagy dynamics2, which are paramount to understanding of neurodegeneration.
We have recently used the dissection and culture of single ommatidia3 that has been essential for our understanding of autophagic dysfunctions in a fly model of Dentatorubro-Pallidoluysian Atrophy (DRPLA)3, 4.
We now report a comprehensive description of this technique (Fig. 1), adapted from electrophysiological studies5, which is likely to expand dramatically the possibility of fly models for neurodegeneration. This method can be adapted to image live subcellular events and to monitor effective drug administration onto photoreceptor cells (Fig. 2). If used in combination with mosaic techniques6-8, the responses of genetically different cells can be assayed in parallel (Fig. 2).

Single Drosophila Ommatidium Dissection and Imaging

The limiting factor in the use of the adult Drosophila eye to study neurodegeneration and cell biology is the difficult imaging of intracellular processes. We describe the dissection of single ommatidia to generate a bona-fide primary neuronal cell culture, which can be subject to drug treatment and advanced imaging.

The fruit fly Drosophila melanogaster has made invaluable contributions to neuroscience research and has been used widely as a model for neurodegenerative ...

Whole Mount Preparation of the Adult Drosophila Ventral Nerve Cord for Giant Fiber Dye Injection

To analyze the axonal and dendritic morphology of neurons, it is essential to obtain accurate labeling of neuronal structures. Preparing well labeled samples with little to no tissue damage enables us to analyze cell morphology and to compare individual samples to each other, hence allowing the identification of mutant anomalies.
In the demonstrated dissection method the nervous system remains mostly inside the adult fly. Through a dorsal incision, the abdomen and thorax are opened and most of the internal organs are removed. Only the dorsal side of the ventral nerve cord (VNC) and the cervical connective 
(CvC) containing the big axons of the giant fibers (GFs)1 are exposed, while the brain containing the GF cell body and dendrites remains2 in the 
intact head. In this preparation most nerves of the VNC should remain attached to their muscles. 
Following the dissection, the intracellular filling of the giant fiber (GF) with a fluorescent dye is demonstrated. In the CvC the GF axons are located at the dorsal surface and thus can be easily visualized under a microscope with differential interference contrast (DIC) optics. This allows the injection of the GF axons with dye at this site to label the entire GF including the axons and their terminals in the VNC. This method results in reliable and strong staining of the GFs allowing the neurons to be imaged immediately after filling with an epifluorescent microscope. Alternatively, the fluorescent signal can be enhanced using standard immunohistochemistry procedures3 suitable for high resolution confocal microscopy.

Whole Mount Preparation of the Adult Drosophila Ventral Nerve Cord for Giant Fiber Dye Injection

An in vivo dissection of the adult Drosophila ventral nerve cord (VNC) is demonstrated. This particular dissection method causes little damage to the VNC allowing the subsequent labeling of the giant fiber neurons with fluorescent dye for high resolution imaging.

To analyze the axonal and dendritic morphology of neurons, it is essential to obtain accurate labeling of neuronal structures. Preparing well labeled ...

Reproducible Mouse Sciatic Nerve Crush and Subsequent Assessment of Regeneration by Whole Mount Muscle Analysis

Regeneration in the peripheral nervous system (PNS) is widely studied both for its relevance to human disease and to understand the robust regenerative response mounted by PNS neurons thereby possibly illuminating the failures of CNS regeneration1. Sciatic nerve crush (axonotmesis) is one of the most common models of peripheral nerve injury in rodents2. Crushing interrupts all axons but Schwann cell basal laminae are preserved so that regeneration is optimal3,4. This allows the investigator to study precisely the ability of a growing axon to interact with both the Schwann cell and basal laminae4. Rats have generally been the preferred animal models for experimental nerve crush. They are widely available and their lesioned sciatic nerve provides a reasonable approximation of human nerve lesions5,4. Though smaller in size than rat nerve, the mouse nerve has many similar qualities. Most importantly though, mouse models are increasingly valuable because of the wide availability of transgenic lines now allows for a detailed dissection of the individual molecules critical for nerve regeneration6, 7. Prior investigators have used multiple methods to produce a nerve crush or injury including simple angled forceps, chilled forceps, hemostatic forceps, vascular clamps, and investigator-designed clamps8,9,10,11,12. Investigators have also used various methods of marking the injury site including suture, carbon particles and fluorescent beads13,14,1. We describe our method to obtain a reproducibly complete sciatic nerve crush with accurate and persistent marking of the crush-site using a fine hemostatic forceps and subsequent carbon crush-site marking. As part of our description of the sciatic nerve crush procedure we have also included a relatively simple method of muscle whole mount we use to subsequently quantify regeneration.

In this report we describe a method to crush mouse sciatic nerve. This method uses readily available hemostatic forceps and easily and reproducibly produces complete sciatic nerve crush. In addition, we describe a method to prepare muscle whole mounts suitable for analysis of nerve regeneration after sciatic nerve crush.

Regeneration in the peripheral nervous system (PNS) is widely studied both for its relevance to human disease and to understand the robust regenerative ...

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

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

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

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

Dissection and Immunohistochemistry of Larval, Pupal and Adult Drosophila Retinas

The compound eye of Drosophila melanogaster consists of about 750 ommatidia (unit eyes). Each ommatidium is composed of about 20 cells, including lens-secreting cone cells, pigment cells, a bristle cell and eight photoreceptors (PRs) R1-R8 2. The PRs have specialized microvillar structures, the rhabdomeres, which contain light-sensitive pigments, the Rhodopsins (Rhs). The rhabdomeres of six PRs (R1-R6) form a trapezoid and contain Rh1 3 4. The rhabdomeres of R7 and R8 are positioned in tandem in the center of the trapezoid and share the same path of light. R7 and R8 PRs stochastically express different combinations of Rhs in two main subtypes5: In the 'p' subtype, Rh3 in pR7s is coupled with Rh5 in pR8s, whereas in the 'y' subtype, Rh4 in yR7s is associated with Rh6 in yR8s 6 7 8.
Early specification of PRs and development of ommatidia begins in the larval eye-antennal imaginal disc, a monolayer of epithelial cells. A wave of differentiation sweeps across the disc9 and initiates the assembly of undifferentiated cells into ommatidia10-11. The 'founder cell' R8 is specified first and recruits R1-6 and then R7 12-14. Subsequently, during pupal development, PR differentiation leads to extensive morphological changes 15, including rhabdomere formation, synaptogenesis and eventually rh expression.
In this protocol, we describe methods for retinal dissections and immunohistochemistry at three defined periods of retina development, which can be applied to address a variety of questions concerning retinal formation and developmental pathways. Here, we use these methods to visualize the stepwise PR differentiation at the single-cell level in whole mount larval, midpupal and adult retinas (Figure 1).

Dissection and Immunohistochemistry of Larval, Pupal and Adult Drosophila Retinas

The Drosophila retina is a crystal-like lattice composed of a small number of cell types that are generated in a stereotyped manner 1. Its amenability to sophisticated genetic analysis allows the study of complex developmental programs. This protocol describes dissections and immunohistochemistry of retinas at three discrete developmental stages, with a focus on photoreceptor differentiation.

The compound eye of Drosophila melanogaster consists of about 750 ommatidia (unit eyes). Each ommatidium is composed of about 20 cells, including ...

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

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

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

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

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

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

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

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

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

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

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 ...