We thank Dr. Yuval Gottlieb-Dror for the electroporation illustration. This work was supported by grants to DSD from The National Institute for Psychobiology in Israel and from the Niedersachsen-Israel Research cooperation program and by grants to AK from The Israel Science Foundation, The Israel ministry of health, and The Center of Excellence-Legacy Heritage Biomedical Science partnership.

1. Hindbrain Electroporation
1.1 Egg handling
<ol>
	<li>Place the eggs horizontally in a humidified incubator (37-38.5 &deg;C). Embryos are electroporated after 65-70 hr of incubation, when they reach 16-17 (HH) stage (25-30 somites).</li>
	<li>Remove the eggs from the incubator; they remain in the horizontal position.</li>
</ol>
1.2 Preparations
<ol>
	<li>Pull glass capillaries (0.5 mm diameter).</li>
	<li>Connect bent L-shaped gold Genetrodes electrodes (3 mm diameter) with an adaptor holder to the pulse generator. Electroporation parameters include 25 volts, 5 pulse numbers, 45 msec pulse length, 300 msec pulse intervals.</li>
	<li>Prepare a mouth pipette, 10 ml syringe needle, parafilm strips, a soft brush, sharp dissecting scissors and 25 ml sterile PBS solution. This amount is usually sufficient to handle an egg tray (18 eggs).</li>
	<li>Prepare an adequate mixture of DNA plasmids (5 &mu;g/&mu;l each) and add about 0.025% Fast Green dye to visualize DNA injection. Usually a volume of 4 &mu;l is sufficient for the injection of a tray.</li>
</ol>
1.3 Windowing, Injection and Electroporation
<ol>
	<li>Clean egg shells with 70% ethanol.</li>
	<li>Handle one egg at a time to minimize embryonic exposure time to air.</li>
	<li>Make a hole at the egg pole with the scissors ends and remove 3-4 ml of albumin with the syringe. Do not remove a larger amount of albumin as it reduces viability.</li>
	<li>Open a small oval window (2.5 x 2 cm size) at the upper center of the egg shell using the dissecting scissors.</li>
	<li>Drip few drops of PBS on top of the embryo to prevent dryness during the whole process.</li>
	<li>Load a small amount of the DNA mixture into the glass capillary using a mouth pipette.</li>
	<li>Place the embryo with its posterior end towards you. No ink injection is required at this stage as the embryo is clearly visible. Avoiding ink injection increases embryonic survival. Penetrate the caudal hindbrain by holding the capillary at ~45&deg;. Do not remove any membrane from around the embryo. Inject DNA solution carefully into the hindbrain lumen and exhale without forming air bubbles. DNA solution spreads anteriorly.</li>
	<li>Immediately after DNA injection, place the parallel electrodes at the precise AP and DV hindbrain position you aim to target. Push the electrodes slightly ventrally without touching the heart, as it may reduce viability. Pulse the electroporator. Electrodes should be covered with bubbles to indicate electrical conductivity (Figure 1A).</li>
	<li>Carefully remove the electrodes and drip few drops of PBS to cool the embryo and to remove bubbles. Seal the egg opening properly with a parafilm strip to prevent drying during incubation. Wash electrodes in PBS with the soft brush.</li>
	<li>Place egg in the incubator for the desired length of time. Survival of embryos is approximately 90% 2-3 days after electroporation, and reduces up to 50% 12 days following electroporation.</li>
</ol>
2. Analysis of Embryos
2.1 Flat-mount preparation and immunofluorescence
<ol>
	<li>Flat-mount preparations of the hindbrain can be performed up to E6.5 to easily visualize axons under a microscope or a stereo-microscope.</li>
	<li>Dissect the embryo carefully by separating it from surrounding membranes and blood vessels. Place the embryo in a small silicone-coated Petri dish containing PBS. Attach the embryo to the dish with tungsten pins facing dorsally. Perform a dorsal slit in the hindbrain roof-plate using sharp glass capillaries.</li>
	<li>Using sharp tweezers and micro-scissors hold the upper part of the head and pull the hindbrain tissue very carefully from rostral to caudal. After separation of the hindbrain remove remaining ventral tissues to reach a clean preparation.</li>
	<li>Incubate the hindbrain with 4% paraformaldehyde (PFA) solution for 1-2 hr at room-temperature (RT). Wash the hindbrain with PBT (PBS/0.1% Triton X-100) to remove PFA.</li>
	<li>For Immunofluorescence in flat-mounted hindbrains add 500 &mu;l of blocking solution (5% of goat serum in PBT and incubate for 2 hr at RT Incubate with 1st antibody ON at 4 &deg;C. Wash with PBT (15 min x 3). Incubate with 2nd antibody for 2 hr at RT. Wash with PBT (15 min x 3).</li>
	<li>Place the hindbrain facing dorsally on a glass slide. Add fluorescent mounting media onto the hindbrain. Use glass capillaries or tungsten needles to flatten the hindbrain on the slide.</li>
	<li>Add small amount of grease at each corner to prevent squeezing of the tissue by the cover slip. Carefully place a cover slip on top of the hindbrain and avoid air bubbles. For adherence add nail polish to cover glass edges.</li>
</ol>
2.2 Cryo-sections and Immunofluorescence
<ol>
	<li>Cryo-sections of the brainstem can be performed at any stage to visualize axonal trajectories. Yet, after E6.5 this should be the preferred method due to the difficulty to visualize axons in the flat-mounted embryo, which becomes too thick. Moreover, demonstration of synapses requires sectioning of the tissue and a high-magnification view under a microscope.</li>
	<li>Dissect the embryo and remove all surrounding tissues. Rinse with PBS. Cut the embryo at the caudal part of the medulla using micro-scissors and sharp tweezers. Make a wide incision between the cerebellum and the midbrain and remove the entire brainstem. The tissue should contain the medulla, pons and cerebellum.</li>
	<li>Fix the brainstem in 4% PFA for overnight (ON) at 4 &deg;C, rinse with PBS (10 min x 3), and incubate with 30% sucrose for ON at 4 &deg;C until sinking.</li>
	<li>Embed the hindbrain in a cryo-mold with OCT (Optimal Cutting Temperature) compound, and place it at -20 &deg;C until freezing, as described elsewhere 11.</li>
	<li>Place the OCT block in the cryostat at the desired sectional axis. Section width is 12 &mu;m.</li>
	<li>Dry the slides. Add 100 &mu;l blocking solution on each slide for 2 hr at RT. Add 100 &mu;l of antibodies (diluted in the blocking solution to the desired concentration). Incubation period for 1st and 2nd antibodies is ON at 4 &deg;C or 2 hr at RT, respectively. For each incubation time, gently add parafilm strip on top of the slide to prevent dryness. Wash with PBS (10 min x 3) between antibodies. If required, add 1:1,000 Dapi (4'-6-Diamidino-2-phenylindole), diluted in PBS for 20 min at RT. Rinse with PBS.</li>
	<li>Mount the slide with fluorescent mounting media. Let dry for 1 hr before analysis.</li>
</ol>

<ol>
	<li>Altman, J., Bayer, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+the+precerebellar+nuclei+in+the+rat:+II.+The+intramural+olivary+migratory+stream+and+the+neurogenetic+organization+of+the+inferior+olive.">Development of the precerebellar nuclei in the rat: II. The intramural olivary migratory stream and the neurogenetic organization of the inferior olive.</a> J. Comp. Neurol. 257, 490-512 (1987).</li><li>Rose, M. F., Ahmad, K. A., Thaller, C., Zoghbi, H. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Excitatory+neurons+of+the+proprioceptive,+interoceptive,+and+arousal+hindbrain+networks+share+a+developmental+requirement+for+Math1.">Excitatory neurons of the proprioceptive, interoceptive, and arousal hindbrain networks share a developmental requirement for Math1.</a> Proc. Natl. Acad. Sci. U.S.A. 106, 22462-22467 (2009).</li><li>Storm, R., 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+bHLH+transcription+factor+Olig3+marks+the+dorsal+neuroepithelium+of+the+hindbrain+and+is+essential+for+the+development+of+brainstem+nuclei.">The bHLH transcription factor Olig3 marks the dorsal neuroepithelium of the hindbrain and is essential for the development of brainstem nuclei.</a> Development. 136, 295-305 (2009).</li><li>Lumsden, 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+cellular+basis+of+segmentation+in+the+developing+hindbrain.">The cellular basis of segmentation in the developing hindbrain.</a> Trends Neurosci. 13, 329-335 (1990).</li><li>Liu, Z., 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=Control+of+precerebellar+neuron+development+by+Olig3+bHLH+transcription+factor.">Control of precerebellar neuron development by Olig3 bHLH transcription factor.</a> J. Neurosci. 28, 10124-10133 (2008).</li><li>Muller, 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+bHLH+factor+Olig3+coordinates+the+specification+of+dorsal+neurons+in+the+spinal+cord.">The bHLH factor Olig3 coordinates the specification of dorsal neurons in the spinal cord.</a> Genes Dev. 19, 733-743 (2005).</li><li>Avraham, O., 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=Motor+and+dorsal+root+ganglion+axons+serve+as+choice+points+for+the+ipsilateral+turning+of+dI3+axons.">Motor and dorsal root ganglion axons serve as choice points for the ipsilateral turning of dI3 axons.</a> J. Neurosci. 30, 15546-15557 (2010).</li><li>Avraham, O., 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=Transcriptional+control+of+axonal+guidance+and+sorting+in+dorsal+interneurons+by+the+Lim-HD+proteins+Lhx9+and+Lhx1.">Transcriptional control of axonal guidance and sorting in dorsal interneurons by the Lim-HD proteins Lhx9 and Lhx1.</a> Neural Dev. 4, 21 (2009).</li><li>Avraham, O., Zisman, S., Hadas, Y., Vald, L., Klar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deciphering+axonal+pathways+of+genetically+defined+groups+of+neurons+in+the+chick+neural+tube+utilizing+in+ovo+electroporation.">Deciphering axonal pathways of genetically defined groups of neurons in the chick neural tube utilizing in ovo electroporation.</a> J. Vis. Exp. (39), e1792 (2010).</li><li>Kohl, A., Hadas, Y., Klar, A., Sela-Donenfeld, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Axonal+Patterns+and+Targets+of+dA1+Interneurons+in+the+Chick+Hindbrain.">Axonal Patterns and Targets of dA1 Interneurons in the Chick Hindbrain.</a> J. Neurosci. 32, 5757-5771 (2012).</li><li>Vogel, J., Mobius, C., Kuschinsky, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+delineation+of+ischemic+tissue+in+rat+brain+cryosections+by+high-contrast+staining.">Early delineation of ischemic tissue in rat brain cryosections by high-contrast staining.</a> Stroke. 30, 1134-1141 (1999).</li><li>Helms, A. W., Abney, A. L., Ben-Arie, N., Zoghbi, H. Y., Johnson, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autoregulation+and+multiple+enhancers+control+Math1+expression+in+the+developing+nervous+system.">Autoregulation and multiple enhancers control Math1 expression in the developing nervous system.</a> Development. 127, 1185-1196 (2000).</li><li>Lumpkin, E. A., 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=Math1-driven+GFP+expression+in+the+developing+nervous+system+of+transgenic+mice.">Math1-driven GFP expression in the developing nervous system of transgenic mice.</a> Gene Expr. Patterns. 3, 389-395 (2003).</li><li>Lu, Y., Lin, C., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PiggyBac+transgenic+strategies+in+the+developing+chicken+spinal+cord.">PiggyBac transgenic strategies in the developing chicken spinal cord.</a> Nucleic Acids Res. 37, e141 (2009).</li><li>Wang, 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=piggyBac-like+elements+in+the+pink+bollworm,+Pectinophora+gossypiella.">piggyBac-like elements in the pink bollworm, Pectinophora gossypiella.</a> Insect Mol. Biol. 19, 177-184 (2010).</li><li>Alsina, B., Vu, T., Cohen-Cory, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualizing+synapse+formation+in+arborizing+optic+axons+in+vivo:+dynamics+and+modulation+by+BDNF.">Visualizing synapse formation in arborizing optic axons in vivo: dynamics and modulation by BDNF.</a> Nat. Neurosci. 4, 1093-1101 (2001).</li><li>Leal-Ortiz, 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=Piccolo+modulation+of+Synapsin1a+dynamics+regulates+synaptic+vesicle+exocytosis.">Piccolo modulation of Synapsin1a dynamics regulates synaptic vesicle exocytosis.</a> J. Cell Biol. 181, 831-846 (2008).</li><li>Gardzinski, P., 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+role+of+synaptotagmin+I+C2A+calcium-binding+domain+in+synaptic+vesicle+clustering+during+synapse+formation.">The role of synaptotagmin I C2A calcium-binding domain in synaptic vesicle clustering during synapse formation.</a> J. Physiol. 581, 75-90 (2007).</li><li>Nowack, A., Yao, J., Custer, K. L., Bajjalieh, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SV2+regulates+neurotransmitter+release+via+multiple+mechanisms.">SV2 regulates neurotransmitter release via multiple mechanisms.</a> Am. J. Physiol. Cell Physiol. 299, C960-C967 (2010).</li><li>Itasaki, N., Sharpe, J., Morrison, A., Krumlauf, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reprogramming+Hox+expression+in+the+vertebrate+hindbrain:+influence+of+paraxial+mesoderm+and+rhombomere+transposition.">Reprogramming Hox expression in the vertebrate hindbrain: influence of paraxial mesoderm and rhombomere transposition.</a> Neuron. 16, 487-500 (1996).</li><li>Clarke, J. D., Lumsden, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Segmental+repetition+of+neuronal+phenotype+sets+in+the+chick+embryo+hindbrain.">Segmental repetition of neuronal phenotype sets in the chick embryo hindbrain.</a> Development. 118, 151-162 (1993).</li><li>Diaz, C., Glover, J. C., Puelles, L., Bjaalie, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+between+hodological+and+cytoarchitectonic+organization+in+the+vestibular+complex+of+the+11-day+chicken+embryo.">The relationship between hodological and cytoarchitectonic organization in the vestibular complex of the 11-day chicken embryo.</a> J. Comp. Neurol. 457, 87-105 (2003).</li><li>Marin, F., Puelles, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphological+fate+of+rhombomeres+in+quail/chick+chimeras:+a+segmental+analysis+of+hindbrain+nuclei.">Morphological fate of rhombomeres in quail/chick chimeras: a segmental analysis of hindbrain nuclei.</a> Eur. J. Neurosci. 7, 1714-1738 (1995).</li><li>Niwa, H., Yamamura, K., Miyazaki, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+selection+for+high-expression+transfectants+with+a+novel+eukaryotic+vector.">Efficient selection for high-expression transfectants with a novel eukaryotic vector.</a> Gene. 108, 193-199 (1991).</li></ol>

No conflicts of interest declared.

In ovo electroporation is a feasible, reliable, and effective tool to examine cell specification and axonal guidance during chick nervous system development 20. In this protocol we describe a mode of electroporation in the chick hindbrain at E2.75 using enhancer elements which enable the conditional labeling of specific interneurons. This strategy is combined with the PiggyBac-mediated transposition system to insert foreign genes into the chick genome, which enables tracking of axonal routes, projecti...

The hindbrain represents a key relay hub of the nervous system by communicating between the central and peripheral nervous systems via ascending and descending neuronal networks. It regulates basic functions including respiration, consciousness, hearing, and motor coordination 1-3. During early embryonic development, the vertebrate hindbrain is transiently subdivided along its anterior-posterior (AP) axis into repetitive rhombomeres, in which distinct neuronal cell types are formed and generate multiple brainstem nuclei centers 4. The hindbrain is also divided along its dorsal-ventral (DV) axis into a basal and alar plate, at which discrete neuronal progenitors become specified and differentiate in distinct DV locations 3,5,6. How the early AP and DV-specific neuronal patterns are governing the establishment of functional brainstem circuitries is largely unknown.
To gain knowledge on this fundamental question, tools are required in order to label specific subsets of neurons in the early hindbrain and to trace their axonal trajectories and connectivity at more advanced stages. We have previously utilized specific enhancer elements, and a Cre/LoxP-based conditional expression system for tracking axonal trajectory of dorsal spinal interneurons in the early chick embryo 7-9. In the current manuscript we have targeted the hindbrain and upgraded the experimental paradigm for labeling late embryonic hindbrain interneurons, axons and their synaptic targets, using a modified electroporation strategy and the PiggyBac - mediated DNA transposition. Our new strategy allows the tagging of distinct neuronal subtypes in one side of the hindbrain and the tracking of their axonal projections and synaptic sites at various embryonic stages, from 2 up to 12 days following electroporation. Based on this method, we labeled the dorsal-most subgroup of hindbrain interneurons (dA1/Atoh1+ cells) and revealed two contralateral ascending axonal projection patterns, each derives from a different AP location and elongates in a distinct funiculus. dA1 axons were found to project and form synapses in the auditory nuclei, midbrain and in multiple layers of the cerebellum 10.
The combination of chick electroporation, genetic tracing of neurons and analysis of projection sites at much advanced stages of development provides a unique platform to study the formation of neuronal networks in the brain and to elucidate molecular mechanisms that govern circuit formation.

<table><tbody><tr><td>L-shaped gold Genetrodes 3 mm electrodes</td><td>BTX, Harvard Apparatus</td><td>45-0162</td><td></td></tr><tr><td>pulse generator, ECM 830</td><td>BTX, Harvard Apparatus</td><td>45-0002</td><td></td></tr><tr><td>OCT (Optimal Cutting Temperature) Compound</td><td>Tissue-Tek Sakura</td><td>4583 O.C.T. Compound</td><td></td></tr><tr><td>Nail Polish</td><td>From Any Commercial Supplier</td><td></td><td></td></tr></tbody></table>

electroporation of the hindbrain to trace axonal trajectories and synaptic targets in the chick embryo

Electroporation of the chick embryonic neural tube has many advantages such as being quick and efficient for the expression of foreign genes into neuronal cells. In this manuscript we provide a method that demonstrates uniquely how to electroporate DNA into the avian hindbrain at E2.75 in order to specifically label a subset of neuronal progenitors, and how to follow their axonal projections and synaptic targets at much advanced stages of development, up to E14.5. We have utilized novel genetic tools including specific enhancer elements, Cre/Lox - based plasmids and the PiggyBac-mediated DNA transposition system to drive GFP expression in a subtype of hindbrain cells (the dorsal most subgroup of interneurons, dA1). Axonal trajectories and targets of dA1 axons are followed at early and late embryonic stages at various brainstem regions. This strategy contributes advanced techniques for targeting cells of interest in the embryonic hindbrain and for tracing circuit formation at multiple stages of development.

This protocol was recently used to uncover the axonal patterns and projection sites of dA1 subgroup of interneurons in the chick hindbrain 10. To specifically label these axons, an enhancer element (Atoh1), that has previously been characterized as specific for spinal dI1 neurons 8,12,13, was confirmed to be expressed in hindbrain dA1 cells 10. The element was cloned upstream to Cre recombinase and co-electroporated at E2.75 along with a Cre dependent cytoplasmic GFP reporter plasmid (pCA...

Watch this Scientific Journal Video about Electroporation of the Hindbrain to Trace Axonal Trajectories and Synaptic Targets in the Chick Embryo at JoVE.com

Electroporation of the Hindbrain to Trace Axonal Trajectories and Synaptic Targets in the Chick Embryo

How neuronal networks are established in the embryonic brain is a fundamental question in developmental neurobiology. Here we combined an electroporation technique with novel genetic tools, such as Cre/Lox&#x2013;plasmids and PiggyBac-mediated DNA transposition system in the avian hindbrain to label dorsal interneurons and track their axonal projections and synaptic targets at various developmental stages.

Electroporation of  the chick embryonic neural tube has many advantages such as being quick and efficient  for the expression of foreign genes into ...

electroporation-hindbrain-to-trace-axonal-trajectories-synaptic

Universidad de Cartagena UDEC

Research

JoVE Journal

Neuroscience

10.8K Views.  The Hebrew University of Jerusalem. How neuronal networks are established in the embryonic brain is a fundamental question in developmental neurobiology. Here we combined an electroporation technique with novel genetic tools, such as Cre/Lox–plasmids and PiggyBac-mediated DNA transposition system in the avian hindbrain to label dorsal interneurons and track their axonal projections and synaptic targets at various developmental stages.

Video: Electroporation of the Hindbrain to Trace Axonal Trajectories and Synaptic Targets in the Chick Embryo

In Ovo Electroporations of HH Stage 10 Chicken Embryos

Large size and external development of the chicken embryo have long made it a valuable tool in the study of developmental biology.  With the advent of molecular biological techniques, the chick has become a useful system in which to study gene regulation and function.  By electroporating DNA or RNA constructs into the developing chicken embryo, genes can be expressed or knocked down in order to analyze in vivo gene function.  Similarly, reporter constructs can be used for fate mapping or to examine putative gene regulatory elements.  Compared to similar experiments in mouse, chick electroporation has the advantages of being quick, easy and inexpensive.  This video demonstrates first how to make a window in the eggshell to manipulate the embryo.  Next, the embryo is visualized with a dilute solution of India ink injected below the embryo.  A glass needle and pipette are used to inject DNA and Fast Green dye into the developing neural tube, then platinum electrodes are placed parallel to the embryo and short electrical pulses are administered with a pulse generator.  Finally, the egg is sealed with tape and placed back into an incubator for further development.  Additionally, the video shows proper egg storage and handling and discusses possible causes of embryo loss following electroporation.

Chick in ovo electroporation is a technique which allows genetic manipulation of the avian embryo. Common applications of this technique include functional analysis of genes and putative enhancer elements. This video demonstrates neural tube electroporation in HH 10 chick embryos. Injection technique and proper egg handling are discussed.

Large size and external development of the chicken embryo have long made it a valuable tool in the study of developmental biology.  With the advent of ...

Biology

In Ovo Electroporation in the Chicken Auditory Brainstem

Electroporation is a method that introduces genes of interest into biologically relevant organisms like the chicken embryo. It is long established that the chicken embryo is an effective research model for studying basic biological functions of auditory system development. More recently, the chicken embryo has become particularly valuable in studying gene expression, regulation and function associated with hearing. In ovo electroporation can be used to target auditory brainstem regions responsible for highly specialized auditory functions. These regions include the chicken nucleus magnocellularis (NM) and nucleus laminaris (NL). NM and NL neurons arise from distinct precursors of rhombomeres 5 and 6 (R5/R6). Here, we present in ovo electroporation of plasmid-encoded genes to study gene-related properties in these regions. We show a method for spatial and temporal control of gene expression that promote either gain or loss of functional phenotypes. By targeting auditory neural progenitor regions associated with R5/R6, we show plasmid transfection in NM and NL. Temporal regulation of gene expression can be achieved by adopting a tet-on vector system. This is a drug inducible procedure that expresses the genes of interest in the presence of doxycycline (Dox). The in ovo electroporation technique &#8211; together with either biochemical, pharmacological, and or in vivo functional assays &#8211; provides an innovative approach to study auditory neuron development and associated pathophysiological phenomena.

In Ovo Electroporation in the Chicken Auditory Brainstem

Auditory brainstem neurons of avians and mammals are specialized for fast neural encoding, a fundamental process for normal hearing functions. These neurons arise from distinct precursors of embryonic hindbrain. We present techniques utilizing electroporation to express genes in the hindbrain of chicken embryos to study gene function during auditory development.

Electroporation is a method that introduces genes of interest into biologically relevant organisms like the chicken embryo. It is long established that ...

Developmental Biology

In ovo Electroporation in Chick Midbrain for Studying Gene Function in Dopaminergic Neuron Development

Dopaminergic neurons located in the ventral midbrain control movement, emotional behavior, and reward mechanisms1-3. The dysfunction of ventral midbrain dopaminergic neurons is implicated in Parkinson's disease, Schizophrenia, depression, and dementia1-5. Thus, studying the regulation of midbrain dopaminergic neuron differentiation could not only provide important insight into mechanisms regulating midbrain development and neural progenitor fate specification, but also help develop new therapeutic strategies for treating a variety of human neurological disorders.
Dopaminergic neurons differentiate from neural progenitors lining the ventricular zone of embryonic ventral midbrain. The development of neural progenitors is controlled by gene expression programs6,7. Here we report techniques utilizing electroporation to express genes specifically in the midbrain of Hamburger Hamilton (HH) stage 11 (thirteen somites, 42 hours) chick embryos8,9. The external development of chick embryos allows for convenient experimental manipulations at specific embryonic stages, with the effects determined at later developmental time points10-13. Chick embryonic neural tubes earlier than HH stage 13 (nineteen somites, 48 hours) consist of multipotent neural progenitors that are capable of differentiating into distinct cell types of the nervous system. The pCAG vector, which contains both a CMV promoter and a chick &beta;-actin enhancer, allows for robust expression of Flag or other epitope-tagged constructs in embryonic chick neural tubes14. In this report, we emphasize special measures to achieve regionally restricted gene expression in embryonic midbrain dopaminergic neuron progenitors, including how to inject DNA constructs specifically into the embryonic midbrain region and how to pinpoint electroporation with small custom-made electrodes. Analyzing chick midbrain at later stages provides an excellent in vivo system for plasmid vector-mediated gain-of-function and loss-of-function studies of midbrain development. Modification of the experimental system may extend the assay to other parts of the nervous system for performing fate mapping analysis and for investigating the regulation of gene expression.

In ovo Electroporation in Chick Midbrain for Studying Gene Function in Dopaminergic Neuron Development

To assess the function and the regulation of genes during the development of midbrain dopaminergic neurons, we describe a method that involves in ovo electroporation of plasmid DNA constructs into embryonic chick ventral midbrain dopaminergic neuron progenitors. This technique can be used to achieve efficient expression of genes of interest to study different aspects of midbrain development and dopaminergic neuron differentiation.

Dopaminergic neurons located in the ventral midbrain control movement, emotional behavior, and reward mechanisms1-3. The dysfunction of ventral midbrain ...

In ovo Electroporation of miRNA-based Plasmids in the Developing Neural Tube and Assessment of Phenotypes by DiI Injection in Open-book Preparations

Commissural dI1 neurons have been extensively studied to elucidate the mechanisms underlying axon guidance during development1,2. These neurons are located in the dorsal spinal cord and send their axons along stereotyped trajectories. Commissural axons initially project ventrally towards and then across the floorplate. After crossing the midline, these axons make a sharp rostral turn and project longitudinally towards the brain. Each of these steps is regulated by the coordinated activities of attractive and repulsive guidance cues. The correct interpretation of these cues is crucial to the guidance of axons along their demarcated pathway. Thus, the physiological contribution of a particular molecule to commissural axon guidance is ideally investigated in the context of the living embryo. Accordingly, gene knockdown in vivo must be precisely controlled in order to carefully distinguish axon guidance activities of genes that may play multiple roles during development.
Here, we describe a method to knockdown gene expression in the chicken neural tube in a cell type-specific, traceable manner. We use novel plasmid vectors3 harboring cell type-specific promoters/enhancers that drive the expression of a fluorescent protein marker, followed directly by a miR30-RNAi transcript4 (located within the 3'-UTR of the cDNA encoding the fluorescent protein) (Figure 1). When electroporated into the developing neural tube, these vectors elicit efficient downregulation of gene expression and express bright fluorescent marker proteins to enable direct tracing of the cells experiencing knockdown3. Mixing different RNAi vectors prior to electroporation allows the simultaneous knockdown of two or more genes in independent regions of the spinal cord. This permits complex cellular and molecular interactions to be examined during development, in a manner that is fast, simple, precise and inexpensive. In combination with DiI tracing of commissural axon trajectories in open-book preparations5, this method is a useful tool for in vivo studies of the cellular and molecular mechanisms of commissural axon growth and guidance. In principle, any promoter/enhancer could be used, potentially making the technique more widely applicable for in vivo studies of gene function during development6.
This video first demonstrates how to handle and window eggs, the injection of DNA plasmids into the neural tube and the electroporation procedure. To investigate commissural axon guidance, the spinal cord is removed from the embryo as an open-book preparation, fixed, and injected with DiI to enable axon pathways to be traced. The spinal cord is mounted between coverslips and visualized using confocal microscopy.

In ovo Electroporation of miRNA-based Plasmids in the Developing Neural Tube and Assessment of Phenotypes by DiI Injection in Open-book Preparations

A method by which gene expression in the neural tube can be downregulated in a cell type-specific, traceable manner is described. We demonstrate how in ovo electroporation of microRNA-based plasmids that elicit spatiotemporally controlled RNA interference can be used to investigate commissural axon guidance in the developing neural tube.

Commissural dI1 neurons have been extensively studied to elucidate the mechanisms underlying axon guidance during development1,2. These neurons are ...

Visualization of Tangential Cell Migration in the Developing Chick Optic Tectum

Time-lapse imaging is a powerful method to analyze migrating cell behavior. After fluorescent cell labeling, the movement of the labeled cells in culture can be recorded under video microscopy. For analyzing cell migration in the developing brain, slice culture is commonly used to observe cell migration parallel to the slice section, such as radial cell migration. However, limited information can be obtained from the slice culture method to analyze cell migration perpendicular to the slice section, such as tangential cell migration. Here, we present the protocols for time-lapse imaging to visualize tangential cell migration in the developing chick optic tectum. A combination of cell labeling by electroporation in ovo and a subsequent flat-mount culture on the cell culture insert enables detection of migrating cell movement in the horizontal plane. Moreover, our method facilitates detection of both individual cell behavior and the collective action of a group of cells in the long term. This method can potentially be applied to detect the sequential change of the fluorescent-labeled micro-structure, including the axonal elongation in the neural tissue or cell displacement in the non-neural tissue.

We describe the methods for fluorescent labeling of tangentially migrating cells by electroporation, and for time-lapse imaging of the labeled cell movement in a flat-mount culture in order to visualize migrating cell behavior in the developing chick optic tectum.

Time-lapse imaging is a powerful method to analyze migrating cell behavior. After fluorescent cell labeling, the movement of the labeled cells in culture ...

Deciphering Axonal Pathways of Genetically Defined Groups of Neurons in the Chick Neural Tube Utilizing in ovo Electroporation

Employment of enhancer elements to drive expression of reporter genes in neurons is a widely used paradigm for tracking axonal projection. For tracking axonal projection of spinal interneurons in vertebrates, germ line-targeted reporter genes yield bilaterally symmetric labeling. Therefore, it is hard to distinguish between the ipsi- and contra-laterally projecting axons. Unilateral electroporation into the chick neural tube provides a useful means to restrict expression of a reporter gene to one side of the central nervous system, and to follow axonal projection on both sides 1 ,2-5. This video demonstrates first how to handle the eggs prior to injection. At HH stage 18-20, DNA is injected into the sacral level of the neural tube, then tungsten electrodes are placed parallel to the embryo and short electrical pulses are administered with a pulse generator. The egg is sealed with tape and placed back into an incubator for further development. Three days later (E6) the spinal cord is removed as an open book preparation from embryo, fixed, and processed for whole mount antibody staining. The stained spinal cord is mounted on slide and visualized using confocal microscopy.

Deciphering Axonal Pathways of Genetically Defined Groups of Neurons in the Chick Neural Tube Utilizing in ovo Electroporation

This video demonstrates how to visualize axonal pathways of genetically defined groups of neurons in the embryonic chick spinal cord utilizing in ovo electroporation of reporter genes under the control of specific enhancer elements.

Employment of enhancer elements to drive expression of reporter genes in neurons is a widely used paradigm for tracking axonal projection. For tracking ...

RNA-Seq Analysis of Differential Gene Expression in Electroporated Chick Embryonic Spinal Cord

In ovo electroporation of the chick neural tube is a fast and inexpensive method for identification of gene function during neural development. Genome wide analysis of differentially expressed transcripts after such an experimental manipulation has the potential to uncover an almost complete picture of the downstream effects caused by the transfected construct. This work describes a simple method for comparing transcriptomes from samples of transfected embryonic spinal cords comprising all steps between electroporation and identification of differentially expressed transcripts. The first stage consists of guidelines for electroporation and instructions for dissection of transfected spinal cord halves from HH23 embryos in ribonuclease-free environment and extraction of high-quality RNA samples suitable for transcriptome sequencing. The next stage is that of bioinformatic analysis with general guidelines for filtering and comparison of RNA-Seq datasets in the Galaxy public server, which eliminates the need of a local computational structure for small to medium scale experiments. The representative results show that the dissection methods generate high quality RNA samples and that the transcriptomes obtained from two control samples are essentially the same, an important requirement for detection of differential expression genes in experimental samples. Furthermore, one example is provided where experimental overexpression of a DNA construct can be visually verified after comparison with control samples. The application of this method may be a powerful tool to facilitate new discoveries on the function of neural factors involved in spinal cord early development.

This video shows the basic steps for performing whole transcriptome analysis on dissected chick embryonic spinal cord samples after transfection with in ovo electroporation.

In ovo electroporation of the chick neural tube is a fast and inexpensive method for identification of gene function during neural development. Genome ...

In Ovo and Ex Ovo Methods to Study Avian Inner Ear Development

The inner ear perceives sound and maintains balance using the cochlea and vestibule. It does this by using a dedicated mechanosensory cell type known as the hair cell. Basic research in the inner ear has led to a deep understanding of how the hair cell functions, and how dysregulation can lead to hearing loss and vertigo. For this research, the mouse has been the pre-eminent model system. However, mice, like all mammals, have lost the ability to replace hair cells. Thus, when trying to understand cellular therapies for restoring inner ear function, complementary studies in other vertebrate species could provide further insights. The auditory epithelium of birds, the basilar papilla (BP), is a sheet of epithelium composed of mechanosensory hair cells (HCs) intercalated by supporting cells (SCs). Although the anatomical architecture of the basilar papilla and the mammalian cochlea differ, the molecular mechanisms of inner ear development and hearing are similar. This makes the basilar papilla a useful system for not only comparative studies but also to understand regeneration. Here, we describe dissection and manipulation techniques for the chicken inner ear. The technique shows genetic and small molecule inhibition methods, which offer a potent tool for studying the molecular mechanisms of inner ear development. In this paper, we discuss in ovo electroporation techniques to genetically perturb the basilar papilla using CRIPSR-Cas9 deletions, followed by dissection of the basilar papilla. We also demonstrate the BP organ culture and optimal use of culture matrices, to observe the development of the epithelium and the hair cells.

In Ovo and Ex Ovo Methods to Study Avian Inner Ear Development

The chick is a cost-effective, accessible, and widely available model organism for a variety of studies. Here, a series of protocols is detailed to understand the molecular mechanisms underlying avian inner ear development and regeneration.

The inner ear perceives sound and maintains balance using the cochlea and vestibule. It does this by using a dedicated mechanosensory cell type known as ...

In Utero Electroporation Approaches to Study the Excitability of Neuronal Subpopulations and Single-cell Connectivity

The nervous system is composed of an enormous range of distinct neuronal types. These neuronal subpopulations are characterized by, among other features, their distinct dendritic morphologies, their specific patterns of axonal connectivity, and their selective firing responses. The molecular and cellular mechanisms responsible for these aspects of differentiation during development are still poorly understood.
Here, we describe combined protocols for labeling and characterizing the structural connectivity and excitability of cortical neurons. Modification of the in utero electroporation (IUE) protocol allows the labeling of a sparse population of neurons. This, in turn, enables the identification and tracking of the dendrites and axons of individual neurons, the precise characterization of the laminar location of axonal projections, and morphometric analysis. IUE can also be used to investigate changes in the excitability of wild-type (WT) or genetically modified neurons by combining it with whole-cell recording from acute slices of electroporated brains. These two techniques contribute to a better understanding of the coupling of structural and functional connectivity and of the molecular mechanisms controlling neuronal diversity during development. These developmental processes have important implications on axonal wiring, the functional diversity of neurons, and the biology of cognitive disorders.

In Utero Electroporation Approaches to Study the Excitability of Neuronal Subpopulations and Single-cell Connectivity

This manuscript provides protocols that use in utero electroporation (IUE) to describe the structural connectivity of neurons at the single-cell level and the excitability of fluorescently labeled neurons. Histology is used to characterize dendritic and axonal projections. Whole-cell recording in acute slices is used to investigate excitability.

The nervous system is composed of an enormous range of distinct neuronal types. These neuronal subpopulations are characterized by, among other features, ...

In Ovo Electroporation in Embryonic Chick Retina

Chicken embryonic retina is an excellent tool to study retinal development in higher vertebrates. Because of large size and external development, it is comparatively very easy to manipulate the chick embryonic retina using recombinant DNA/RNA technology. Electroporation of DNA/RNA constructs into the embryonic retina have a great advantage to study gene regulation in retinal stem/progenitor cells during retinal development. Different type of assays such as reporter gene assay, gene over-expression, gene knock down (shRNA) etc. can be performed using the electroporation technique. This video demonstrates targeted retinal injection and in ovo electroporation into the embryonic chick retina at the Hamburger and Hamilton stage 22-23, which is about embryonic day 4 (E4). Here we show a rapid and convenient in ovo electroporation technique whereby a plasmid DNA that expresses green fluorescent protein (GFP) as a marker is directly delivered into the chick embryonic subretinal space and followed by electric pulses to facilitate DNA uptake by retinal stem/progenitor cells. The new method of retinal injection and electroporation at E4 allows the visualization of all retinal cell types, including the late-born neurons1, which has been difficult with the conventional method of injection and electroporation at E1.52.

In Ovo Electroporation in Embryonic Chick Retina

The overall goal of this video is to show how to perform targeted retinal injection and in ovo electroporation of DNA/RNA constructs into the chick embryonic retina at the Hamburger and Hamilton stage 22-23, which is about embryonic day 4 (E4). This technique is very useful to study gene expression, gene regulation, and morphological change in developing chick retina.

Chicken embryonic retina is an excellent tool to study retinal development in higher vertebrates. Because of large size and external development, it is ...

Electroporation of the Hindbrain to Trace Axonal Trajectories and Synaptic Targets in the Chick Embryo

Podsumowanie

Przeglądaj więcej filmów

Rozdziały w tym wideo

In Ovo Electroporations of HH Stage 10 Chicken Embryos

In Ovo Electroporation in the Chicken Auditory Brainstem

In ovo Electroporation in Chick Midbrain for Studying Gene Function in Dopaminergic Neuron Development

In ovo Electroporation of miRNA-based Plasmids in the Developing Neural Tube and Assessment of Phenotypes by DiI Injection in Open-book Preparations

Visualization of Tangential Cell Migration in the Developing Chick Optic Tectum

Deciphering Axonal Pathways of Genetically Defined Groups of Neurons in the Chick Neural Tube Utilizing in ovo Electroporation

RNA-Seq Analysis of Differential Gene Expression in Electroporated Chick Embryonic Spinal Cord

In Ovo and Ex Ovo Methods to Study Avian Inner Ear Development

In Utero Electroporation Approaches to Study the Excitability of Neuronal Subpopulations and Single-cell Connectivity

In Ovo Electroporation in Embryonic Chick Retina