We acknowledge K. Mikic, who contributed to the initial phase of this movie and M. Nicolescu for the miR picture. C. Huber was supported by a fellowship of the IZKF of the Universtit&auml;tsklinikum T&uuml;bingen, A. Alwin Prem Anand by the Fort&uuml;ne programme of the Universtit&auml;tsklinikum T&uuml;bingen.

1. Requirements for In ovo Electroporation
<ol>
 <li>Preparing the vector construct: 
 miR sense and antisense primers were designed after the instructions of Ambion, annealed and ligated into ApaI/EcoRI digested pSilencer U6.1 vector. After successful transformation one of the resulting clones was grown and pSilencer plasmid was isolated by alkaline lysis method using a Quiagen midi preparation kit. </li>
 <li>Electrodes: 
 Electrodes can be purchased or easily be built13. We use self-made electrodes of platinum wire (&Phi; = 0.2, 0.25, or 0.5 mm in diameter) or in some cases an even smaller tungsten wire electrode (&Phi; = 0.1 mm)8 depending on which area we want to electroporate. To avoid scorching of tissue, we use as a rule the nearer to the tissue the thinner the electrodes. For broad electroporation of midbrain, we use 0.5 mm platinum wires soldered to a brass/stainless steel tubular shaft and fixed to an electrode holder with a distance of 3-5 mm (Figure 1). To electroporate specific areas, we use 0.25 mm platinum wire anodes and 0.2 mm platinum wire or 0.1 mm tungsten for the cathode with an approximate distance of 1 mm or less. </li>
 <li>Solutions: Have the following solutions ready: 
 <ol>
 <li>Autoclaved chicken Ringer, pH 7.5 (9.0 g NaCl, 0.42 g KCl, 0.24 g CaCl2, dissolve in 1 L distilled water).</li>
 <li>PBS (8 g NaCl, 0.2 g KCl, 0.24 g KH2PO4, 1.44 g Na2HPO4, dissolve in 1l distilled H2O). </li>
 <li>Fast Green: stock solution 10 mg/ml distilled H2O</li>
 <li> Slow drying ink (less shellac and thus less poisoning for the embryo). Note: A blue dichroic filter attached to a fiber optic lamp as described in Canto-Soler and Adler14 enhances the contrast and can eliminate the need to inject ink. </li>
 </ol>
 </li>
</ol>
<img src="/files/ftp_upload/50024/50024fig1.jpg" fo:content-width="6in" fo:src="/files/ftp_upload/50024/50024fig1highres.jpg"/> 
Figure 1. Schematic diagram of electrodes and electrode holder. (A, B, C) Platinum wire was soldered to one side of a stainless steel tubular shaft. A hole was drilled into the other side of the tubular shaft thus that pin plugs can fit in. (A) Red and blue colored wires were connected to the pin plugs. At the opposite end the wire was fitted to banana connectors that work with the electrical sockets of the electroporator. (A, C) The platinum wire was bent in an angel of 90&deg;. A layer of nail varnish isolated the shaft above the bend.
2. Preparations Directly Before In ovo Electroporation
<ol>
 <li>Prepare the following material:
 <ol>
 <li>Dilute Ink with chicken Ringer 1:6, add Antibiotic-Antimycotic solution (100x from Gibco) 1:100.</li>
 <li>Prepare vector solution: 1-2 &mu;g/&mu;l per specific DNA in H2O supplemented with Fast Green (1:20).</li>
 <li>Sterilize forceps, scissors, tungsten needle and electrodes with 70% ethanol.</li>
 <li>Pull micropipettes for nucleic acid injection from borosilicate glass capillaries (length to outer diameter: 100 mm x 0.9 mm). We use a simple puller PUL-1 (WPI, Berlin) with the settings shown in Table 1. </li>
 <li>Set the parameters of the electroporator as shown in Table 2.</li>
 </ol>
 </li> 
</ol>
 <table border="1" >
 <tbody>
 <tr>
 <td fo:width="1in">Parameters</td>
 <td fo:width="1in">Values</td>
 </tr>
 <tr>
 <td>Heat </td>
 <td>350</td>
 </tr>
 <tr>
 <td>Pull</td>
 <td>100</td>
 </tr>
 <tr>
 <td>Velocity</td>
 <td>50</td>
 </tr>
 <tr>
 <td>Delay</td>
 <td>200</td>
 </tr>
 </tbody>
 </table>
Table 1. Settings for PUL-1 
 <table border="1">
 <tbody>
 <tr>
 <td fo:width="1.5in">Parameters</td>
 <td fo:width="1.5in">Values</td>
 </tr>
 <tr>
 <td>Frequency</td>
 <td>50 Hz</td>
 </tr>
 <tr>
 <td>Delay</td>
 <td>20 - 50 msec*</td>
 </tr>
 <tr>
 <td>Width</td>
 <td>20 msec</td>
 </tr>
 <tr>
 <td>Voltage</td>
 <td>8-25 V *</td>
 </tr>
 <tr>
 <td>Pulse</td>
 <td>3 - 5 times</td>
 </tr>
 <tr>
 <td colspan="2">*Depending on electrode diameter and distance. Please take that into account when changing one of the parameters. </td>
 </tr>
 </tbody>
 </table>
Table 2. Settings for the Pulse Stimulator
<ol start="2">
 <li>Prepare chick embryos for electroporation:
 <ol>
 <li>Incubate fertilized chicken eggs on their longer side at 37 &deg;C with 65% humidity for 39 hr to acquire embryos between Hamburger &amp; Hamilton (HH) stages15 9-11. The embryo settles at the topmost part of the egg, so you should mark it with a pencil line.</li>
 <li>Disinfect the eggs with 70% ethanol. </li>
 <li>Pierce the egg at its broader side, where the air cavity should be. </li>
 <li>Remove 1-2 ml of egg white. This will detach the embryo from the eggshell. </li>
 <li>Cello-tape the eggshell to avoid shell splinters falling onto the embryo. Use a pair of scissors to cut a small window into the eggshell around the pencil line. </li>
 <li>Inject a bit of ink underneath the area opaca to visualize the embryo.</li>
 <li>Make a cut into the vitelline membrane with a sharpened tungsten needle to achieve a better accessibility of the embryo for nucleic acid injection and electroporation. </li>
 </ol>
 </li>
</ol>
3. Electroporation and Incubation
<ol>
 <li>Add a few drops of warm Ringer's solution onto the embryos. This will lower the embryos, prevent overheating, sticking of the electrodes to the tissue and provide a medium for the current between the two electrodes. </li>
 <li>Inject the vector solution into the lumen of the neural tube at midbrain level. If your DNA expression vector contains no reporter gene (e.g. EGFP), add a slightly lower concentrated reporter gene vector (1 &mu;g/&mu;l miR expressing vector to 0.9 &mu;g/&mu;l reporter gene vector) to the DNA solution. This will ensure that you recognize transfected cells later8. We use the so-called pCAX vector, a kind gift from C. Krull 13. </li>
 <li>For a broad transfection of the midbrain, place the electrodes left and right of the embryo at the height of the midbrain. The distance between the electrodes should be around 3-5 mm. The other settings are 15V, 20 msec pulses and 50 msec delay for HH 10. Changing the position of the two electrodes slightly along the dorso-ventral (DV) axis of the midbrain assures a more a broad transfection of cells the DV axis transfection. </li>
 <li>For ventral transfection, add some Ringer to raise the head from the yolk membrane and place the anode beneath ventral midbrain. If the head does not rise push the electrode under the membrane that separates yolk and embryo to avoid scorching of the neural tube. The cathode should be placed above the midbrain dorso-laterally opposite to the anode. Do not touch the neural tube. We transfect the left ventral half of the midbrain to avoid any difficulties with heart development. The distance between the electrodes is around 1-0.5 mm, the rest of the settings are 10V, 20 msec width and 50 msec delay.</li>
 <li>Apply another drop of Saline on top of the embryos to cool it down and remove air bubbles. </li>
 <li>Seal the eggs with the tape and incubate for at least 4 hr; the minimum time required for vector expression. </li>
</ol>
 4. Fixation of Chicken Embryos
 <ol>
 <li>Remove the embryos from their eggs. </li>
 <li>Clean embryos under a stereomicroscope and assess the extent of transfection with a fluorescent stereo microscope. </li>
 <li>Fix the embryos over night in 4% PFA at 4&deg;C. Proceed with sectioning and/or staining (in situ hybridization, immunohistochemistry) to analyse changes in the transfected area. </li>
 </ol>

<ol>
	<li>Kutter, C., Svoboda, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=miRNA,+siRNA,+piRNA:+Knowns+of+the+unknown.">miRNA, siRNA, piRNA: Knowns of the unknown.</a> RNA Biol. 5, 181-188 (2008).</li><li>Szell, M., Bata-Csorgo, Z., Kemeny, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+enigmatic+world+of+mRNA-like+ncRNAs:+their+role+in+human+evolution+and+in+human+diseases.">The enigmatic world of mRNA-like ncRNAs: their role in human evolution and in human diseases.</a> Semin. Cancer Biol. 18, 141-148 (2008).</li><li>Li, X., Jin, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Roles+of+small+regulatory+RNAs+in+determining+neuronal+identity.">Roles of small regulatory RNAs in determining neuronal identity.</a> Nature reviews. Neuroscience. 11, 329-338 (2010).</li><li>Riedmann, L. T., Schwentner, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=miRNA,+siRNA,+piRNA+and+argonautes:+news+in+small+matters.">miRNA, siRNA, piRNA and argonautes: news in small matters.</a> RNA Biol. 7, 133-139 (2010).</li><li>Coolen, M., Bally-Cuif, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MicroRNAs+in+brain+development+and+physiology.">MicroRNAs in brain development and physiology.</a> Curr. Opin. Neurobiol. 19, 461-470 (2009).</li><li>Muramatsu, T., Mizutani, Y., Ohmori, Y., Okumura, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+three+nonviral+transfection+methods+for+foreign+gene+expression+in+early+chicken+embryos+in+ovo.">Comparison of three nonviral transfection methods for foreign gene expression in early chicken embryos in ovo.</a> Biochem. Biophys. Res. Commun. 230, 376-380 (1997).</li><li>Itasaki, N., Bel-Vialar, S., 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=Shocking'+developments+in+chick+embryology:+electroporation+and+in+ovo+gene+expression.">Shocking' developments in chick embryology: electroporation and in ovo gene expression.</a> Nat. Cell Biol. 1, 203-207 (1999).</li><li>Momose, 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=Efficient+targeting+of+gene+expression+in+chick+embryos+by+microelectroporation.">Efficient targeting of gene expression in chick embryos by microelectroporation.</a> Dev. Growth Differ. 41, 335-344 (1999).</li><li>Nakamura, H., Watanabe, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Misexpression+of+genes+in+brain+vesicles+by+in+ovo+electroporation.">Misexpression of genes in brain vesicles by in ovo electroporation.</a> Dev. Growth Differ. 42, 199-201 (2000).</li><li>Voiculescu, O., Papanayotou, C., Stern, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatially+and+temporally+controlled+electroporation+of+early+chick+embryos.">Spatially and temporally controlled electroporation of early chick embryos.</a> Nat. Protoc. 3, 419-426 (2008).</li><li>Neumann, E., Schaefer-Ridder, M., Wang, Y., Gene Hofschneider, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=transfer+into+mouse+lyoma+cells+by+electroporation+in+high+electric+fields.">transfer into mouse lyoma cells by electroporation in high electric fields.</a> The EMBO journal. 1, 841-845 (1982).</li><li>Potter, H., Weir, L., Leder, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancer-dependent+expression+of+human+kappa+immunoglobulin+genes+introduced+into+mouse+pre-B+lymphocytes+by+electroporation.">Enhancer-dependent expression of human kappa immunoglobulin genes introduced into mouse pre-B lymphocytes by electroporation.</a> Proceedings of the National Academy of Sciences of the United States of America. 81, 7161-7165 (1984).</li><li>Krull, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+primer+on+using+in+ovo+electroporation+to+analyze+gene+function.">A primer on using in ovo electroporation to analyze gene function.</a> Dev. Dyn. 229, 433-439 (2004).</li><li>Canto-Soler, M. V., Adler, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optic+cup+and+lens+development+requires+Pax6+expression+in+the+early+optic+vesicle+during+a+narrow+time+window.">Optic cup and lens development requires Pax6 expression in the early optic vesicle during a narrow time window.</a> Developmental biology. , 294-2119 (2006).</li><li>Hamburger, V., Hamilton, H. 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+series+of+normal+stages+in+the+development+of+the+chick+embryo.+1951.">A series of normal stages in the development of the chick embryo. 1951.</a> Dev Dyn. 195, 231-272 (1992).</li><li>Muramatsu, T., Nakamura, A., Park, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+electroporation:+a+powerful+and+convenient+means+of+nonviral+gene+transfer+to+tissues+of+living+animals+(Review).">In vivo electroporation: a powerful and convenient means of nonviral gene transfer to tissues of living animals (Review).</a> Int J Mol Med. 1, 55-62 (1998).</li><li>Agoston, Z., Li, N., Haslinger, A., Wizenmann, A., Schulte, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+and+physical+interaction+of+Meis2,+Pax3+and+Pax7+during+dorsal+midbrain+development.">Genetic and physical interaction of Meis2, Pax3 and Pax7 during dorsal midbrain development.</a> BMC Dev Biol. 12, 10 (2012).</li><li>De Pietri Tonelli, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-cell+detection+of+microRNAs+in+developing+vertebrate+embryos+after+acute+administration+of+a+dual-fluorescence+reporter/sensor+plasmid.">Single-cell detection of microRNAs in developing vertebrate embryos after acute administration of a dual-fluorescence reporter/sensor plasmid.</a> Biotechniques. 41, 727-732 (2006).</li></ol>

We have nothing to disclose.

This video demonstrates an effective method to transfect plasmid into the neuroepithelial cells of specific areas of the chick midbrain. Rectangular electric pulses of low voltage can introduce DNA into cells of the chick neural tube in ovo6,16. However, the accuracy of DNA targeting is often hindered by the wide electric field, which rises through the relatively large electrodes (&Phi; = 0.5 mm). We tried to tackle that problem by using electrodes smaller in diameter following the guidelines of Momos...

The recognition of small non-coding RNAs as additional players for gene expression launched a new complexity to genomic programming/gene regulation. Different species of non-coding RNAs have functional importance in neural cells, including small non-coding RNAs1-4. MicroRNAs (miR or miRNA) for example show distinct and changing expression profiles in developing brains5. Targeted in ovo electroporation of chick embryos provides a unique opportunity for temporal and spatial control of gene expression and silencing during development. 
This video demonstrates the different steps of performing ectopic expression of miRs in specific areas of the chick midbrain using in ovo electroporation6-10. To ensure a long lasting effect of these small non-coding RNAs in cells, the DNA sequence of miRs were cloned into mono- or bi-cistronic vectors. For in ovo electroporation, miR containing vector is injected into the midbrain neural tube by exposing the embryo after making a small window in the egg shell. To transfect specific areas of the midbrain small plus (anode) and minus (cathode) platinum electrodes are placed at specific positions. For ventral midbrain transfection, the anode is placed underneath the left ventral midbrain and the cathode above the right half of the midbrain before applying a current. The opening in the eggshell is closed with tape and embryos are incubated for as long as required for any analysis. This method was originally described by Muramatsu et al.6 and improved by Momose et al.8 for specific area transfection.
<img src="/files/ftp_upload/50024/50024schematic1.jpg" fo:content-width-="6in" fo:src="/files/ftp_upload/50024/50024schematic1highres.jpg"/> 
Schematic Overview. 
<ol>
 <li> The embryo in the egg is exposed by cutting a small window into the eggshell. </li>
 <li> The dissolved vector(s) is injected into the midbrain using a micro capillary. </li>
 <li>Two electrodes - placed parallel or under and above the embryo - generate a pulsed electric field.</li>
 <li> The electric field temporally creates pores in the cell membrane, which facilitate entry into the cell by the negatively charged DNA (or RNA) attracted to the anode11,12. </li>
</ol>

<table border="1">
<tbody>
 <tr>
 <td>Name </td>
 <td>Company</td>
 <td></td>
 <td>Model</td>
 </tr>
 <tr>
 <td>Borosillicate glass capillaries </td>
 <td>Hartenstein</td>
 <td></td>
 <td>Model: 0.9 mm</td>
 </tr>
 <tr>
 <td>Microcapillary puller</td>
 <td>WPI, Berlin</td>
 <td></td>
 <td>Model: Pul1-E</td>
 </tr>
 <tr>
 <td>Electroporator</td>
 <td>Intracel</td>
 <td></td>
 <td>Model: TSSIC</td>
 </tr>
 <tr>
 <td>Stereomicroscope - fluorescence </td>
 <td>LEICA</td>
 <td></td>
 <td>Model: MZFLIII</td>
 </tr>
 <tr>
 <td>Stereomicroscope</td>
 <td>Zeiss</td>
 <td></td>
 <td>Model: Stemi</td>
 </tr>
 <tr>
 <td>Camera and software</td>
 <td>Zeiss</td>
 <td></td>
 <td>Model: Axiocam MRc/ Axiovision Re. 4.8</td>
 </tr>
 </tbody>
</table>

in ovo expression of microrna in ventral chick midbrain

Non-coding RNAs are additional players in regulating gene expression. Targeted in ovo electroporation of specific areas provides a unique tool for spatial and temporal control of ectopic microRNA expression. However, ventral brain structures like ventral midbrain are rather difficult to reach for any manipulations. Here, we demonstrate an efficient way to electroporate miRNA into ventral midbrain using thin platinum electrodes. This method offers a reliable way to transfect specific areas of the midbrain and a useful tool for in vivo studies.

The extent of the midbrain area transfected with miR is visible through the expression of GFP from a reporter vector injected along with the miR expressing vector (Figure 2). Using platinum electrodes with a diameter of 0.5 mm and placed parallel to the AP axis of midbrain leads normally to the transfection of a broad area along the DV- and AP- axis, including hindbrain, midbrain and sometimes diencephalon (Figures 2A and B). The size of the electrodes results in a wide electric field ap...

Watch this Scientific Journal Video about In ovo Expression of MicroRNA in Ventral Chick Midbrain at JoVE.com

In ovo Expression of MicroRNA in Ventral Chick Midbrain

Ectopic expression is one technique to elucidate the microRNAs role in brain development. However, targeting specific areas using in ovo electroporation is challenging. Here, we show an efficient way to selectively electroporate ventral and dorsal midbrain regions.

In ovo Expression of MicroRNA in Ventral Chick Midbrain

Non-coding RNAs are additional players in regulating gene expression. Targeted in ovo electroporation of specific areas provides a unique tool for spatial ...

in-ovo-expression-of-microrna-in-ventral-chick-midbrain

Research

JoVE Journal

Neuroscience

10.4K Views.  University of Tübingen. Ectopic expression is one technique to elucidate the microRNAs role in brain development. However, targeting specific areas using in ovo electroporation is challenging. Here, we show an efficient way to selectively electroporate ventral and dorsal midbrain regions.

Video: In ovo Expression of MicroRNA in Ventral Chick Midbrain

Organotypic Slice Cultures of Embryonic Ventral Midbrain: A System to Study Dopaminergic Neuronal Development in vitro

The mouse is an excellent model organism to study mammalian brain development due to the abundance of molecular and genetic data. However, the developing mouse brain is not suitable for easy manipulation and imaging in vivo since the mouse embryo is inaccessible and opaque. Organotypic slice cultures of embryonic brains are therefore widely used to study murine brain development in vitro. Ex-vivo manipulation or the use of transgenic mice allows the modification of gene expression so that subpopulations of neuronal or glial cells can be labeled with fluorescent proteins. The behavior of labeled cells can then be observed using time-lapse imaging. Time-lapse imaging has been particularly successful for studying cell behaviors that underlie the development of the cerebral cortex at late embryonic stages 1-2. Embryonic organotypic slice culture systems in brain regions outside of the forebrain are less well established. Therefore, the wealth of time-lapse imaging data describing neuronal cell migration is restricted to the forebrain 3,4. It is still not known, whether the principles discovered for the dorsal brain hold true for ventral brain areas. In the ventral brain, neurons are organized in neuronal clusters rather than layers and they often have to undergo complicated migratory trajectories to reach their final position. The ventral midbrain is not only a good model system for ventral brain development, but also contains neuronal populations such as dopaminergic neurons that are relevant in disease processes. While the function and degeneration of dopaminergic neurons has been investigated in great detail in the adult and ageing brain, little is known about the behavior of these neurons during their differentiation and migration phase 5. We describe here the generation of slice cultures from the embryonic day (E) 12.5 mouse ventral midbrain. These slice cultures are potentially suitable for monitoring dopaminergic neuron development over several days in vitro. We highlight the critical steps in generating brain slices at these early stages of embryonic development and discuss the conditions necessary for maintaining normal development of dopaminergic neurons in vitro. We also present results from time lapse imaging experiments. In these experiments, ventral midbrain precursors (including dopaminergic precursors) and their descendants were labeled in a mosaic manner using a Cre/loxP based inducible fate mapping system 6.

Organotypic Slice Cultures of Embryonic Ventral Midbrain: A System to Study Dopaminergic Neuronal Development in vitro

A method to generate organotypic slices from the E12.5 murine embryonic midbrain is described. The organotypic slice cultures can be used to observe the behavior of dopaminergic neurons or other ventral midbrain neurons.

The  mouse is an excellent model organism to study mammalian brain development due  to the abundance of molecular and genetic data. However, the ...

High-resolution Live Imaging of Cell Behavior in the Developing Neuroepithelium

The embryonic spinal cord consists of cycling neural progenitor cells that give rise to a large percentage of the neuronal and glial cells of the central nervous system (CNS). Although much is known about the molecular mechanisms that pattern the spinal cord and elicit neuronal differentiation1, 2, we lack a deep understanding of these early events at the level of cell behavior. It is thus critical to study the behavior of neural progenitors in real time as they undergo neurogenesis.
In the past, real-time imaging of early embryonic tissue has been limited by cell/tissue viability in culture as well as the phototoxic effects of fluorescent imaging. Here we present a novel assay for imaging such tissue for long periods of time, utilizing a novel ex vivo slice culture protocol and wide-field fluorescence microscopy (Fig. 1). This approach achieves long-term time-lapse monitoring of chick embryonic spinal cord progenitor cells with high spatial and temporal resolution.
This assay may be modified to image a range of embryonic tissues3, 4 In addition to the observation of cellular and sub-cellular behaviors, the development of novel and highly sensitive reporters for gene activity (for example, Notch signaling5) makes this assay a powerful tool with which to understand how signaling regulates cell behavior during embryonic development.

Imaging embryonic tissue in real-time is challenging over long periods of time. Here we present an assay for monitoring cellular and sub-cellular changes in chick spinal cord for long periods with high spatial and temporal resolution. This technique can be adapted for other regions of the nervous system and developing embryo.

The embryonic spinal cord consists of cycling neural progenitor cells that give rise to a large percentage of the neuronal and glial cells of the central ...

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 ...

Comprehensive Profiling of Dopamine Regulation in Substantia Nigra and Ventral Tegmental Area

Dopamine is a vigorously studied neurotransmitter in the CNS. Indeed, its involvement in locomotor activity and reward-related behaviour has fostered five decades of inquiry into the molecular deficiencies associated with dopamine regulation. The majority of these inquiries of dopamine regulation in the brain focus upon the molecular basis for its regulation in the terminal field regions of the nigrostriatal and mesoaccumbens pathways; striatum and nucleus accumbens. Furthermore, such studies have concentrated on analysis of dopamine tissue content with normalization to only wet tissue weight. Investigation of the proteins that regulate dopamine, such as tyrosine hydroxylase (TH) protein, TH phosphorylation, dopamine transporter (DAT), and vesicular monoamine transporter 2 (VMAT2) protein often do not include analysis of dopamine tissue content in the same sample. The ability to analyze both dopamine tissue content and its regulating proteins (including post-translational modifications) not only gives inherent power to interpreting the relationship of dopamine with the protein level and function of TH, DAT, or VMAT2, but also extends sample economy. This translates into less cost, and yet produces insights into the molecular regulation of dopamine in virtually any paradigm of the investigators' choice.
We focus the analyses in the midbrain. Although the SN and VTA are typically neglected in most studies of dopamine regulation, these nuclei are easily dissected with practice. A comprehensive readout of dopamine tissue content and TH, DAT, or VMAT2 can be conducted. There is burgeoning literature on the impact of dopamine function in the SN and VTA on behavior, and the impingements of exogenous substances or disease processes therein 1-5. Furthermore, compounds such as growth factors have a profound effect on dopamine and dopamine-regulating proteins, to a comparatively greater extent in the SN or VTA 6-8. Therefore, this methodology is presented for reference to laboratories that want to extend their inquiries on how specific treatments modulate behaviour and dopamine regulation. Here, a multi-step method is presented for the analyses of dopamine tissue content, the protein levels of TH, DAT, or VMAT2, and TH phosphorylation from the substantia nigra and VTA from rodent midbrain. The analysis of TH phosphorylation can yield significant insights into not only how TH activity is regulated, but also the signaling cascades affected in the somatodendritic nuclei in a given paradigm.
We will illustrate the dissection technique to segregate these two nuclei and the sample processing of dissected tissue that produces a profile revealing molecular mechanisms of dopamine regulation in vivo, specific for each nuclei (Figure 1).

Dopamine is distinctly regulated in the midbrain nuclei, which contain the cell bodies and dendrites of the dopamine neurons. Here we describe a dissection and sample-handling approach to maximize results, and thus conclusions and insights, on dopamine regulation in the midbrain nuclei of the substantia nigra (SN) and ventral tegmental area (VTA) in rodents.

Dopamine is a vigorously studied neurotransmitter in the CNS. Indeed, its involvement in locomotor activity and reward-related behaviour has fostered five ...

Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs through activation of their ion channels and neurotransmitter receptors, and process information in part through activity-dependent release of gliotransmitters. Furthermore, astrocytes constitute the main uptake system for glutamate, contribute to potassium spatial buffering, as well as to GABA clearance. These cells therefore constantly monitor synaptic activity, and are thereby sensitive indicators for alterations in synaptically-released glutamate, GABA and extracellular potassium levels. Additionally, alterations in astroglial uptake activity or buffering capacity can have severe effects on neuronal functions, and might be overlooked when characterizing physiopathological situations or knockout mice. Dual recording of neuronal and astroglial activities is therefore an important method to study alterations in synaptic strength associated to concomitant changes in astroglial uptake and buffering capacities. Here we describe how to prepare hippocampal slices, how to identify stratum radiatum astrocytes, and how to record simultaneously neuronal and astroglial electrophysiological responses. Furthermore, we describe how to isolate pharmacologically the synaptically-evoked astroglial currents.

The preparation of acute brain slices from isolated hippocampi, as well as the simultaneous electrophysiological recordings of astrocytes and neurons in stratum radiatum during stimulation of schaffer collaterals is described. The pharmacological isolation of astroglial potassium and glutamate transporter currents is demonstrated.

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs ...

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 ...

Environmental Modulations of the Number of Midbrain Dopamine Neurons in Adult Mice

Long-lasting changes in the brain or &#8216;brain plasticity&#8217; underlie adaptive behavior and brain repair following disease or injury. Furthermore, interactions with our environment can induce brain plasticity. Increasingly, research is trying to identify which environments stimulate brain plasticity beneficial for treating brain and behavioral disorders. Two environmental manipulations are described which increase or decrease the number of tyrosine hydroxylase immunopositive (TH+, the rate-limiting enzyme in dopamine (DA) synthesis) neurons in the adult mouse midbrain. The first comprises pairing male and female mice together continuously for 1 week, which increases midbrain TH+ neurons by approximately 12% in males, but decreases midbrain TH+ neurons by approximately 12% in females. The second comprises housing mice continuously for 2 weeks in &#8216;enriched environments&#8217; (EE) containing running wheels, toys, ropes, nesting material, etc., which increases midbrain TH+ neurons by approximately 14% in males. Additionally, a protocol is described for concurrently infusing drugs directly into the midbrain during these environmental manipulations to help identify mechanisms underlying environmentally-induced brain plasticity. For example, EE-induction of more midbrain TH+ neurons is abolished by concurrent blockade of synaptic input onto midbrain neurons. Together, these data indicate that information about the environment is relayed via synaptic input to midbrain neurons to switch on or off expression of &#8216;DA&#8217; genes. Thus, appropriate environmental stimulation, or drug targeting of the underlying mechanisms, might be helpful for treating brain and behavioral disorders associated with imbalances in midbrain DA (e.g. Parkinson&#8217;s disease, attention deficit and hyperactivity disorder, schizophrenia, and drug addiction).

This protocol describes two different environmental manipulations and a concurrent brain infusion protocol to study environmentally-induced brain changes underlying adaptive behavior and brain repair in adult mice.

Long-lasting changes in the brain or &#8216;brain plasticity&#8217; underlie adaptive behavior and brain repair following disease or injury. Furthermore, ...

Reliable Identification of Living Dopaminergic Neurons in Midbrain Cultures Using RNA Sequencing and TH-promoter-driven eGFP Expression

In Parkinson&#39;s Disease (PD) there is widespread neuronal loss throughout the brain with pronounced degeneration of dopaminergic neurons in the SNc, leading to bradykinesia, rigidity, and tremor. The identification of living dopaminergic neurons in primary Ventral Mesencephalic (VM) cultures using a fluorescent marker provides an alternative way to study the selective vulnerability of these neurons without relying on the immunostaining of fixed cells. Here, we isolate, dissociate, and culture mouse VM neurons for 3 weeks. We then identify dopaminergic neurons in the cultures using eGFP fluorescence (driven by a Tyrosine Hydroxylase (TH) promoter). Individual neurons are harvested into microcentrifuge tubes using glass micropipettes. Next, we lyse the harvested cells, and conduct cDNA synthesis and transposon-mediated &#34;tagmentation&#34; to produce single cell RNA-Seq libraries1,2,3,4,5. After passing a quality-control check, single-cell libraries are sequenced and subsequent analysis is carried out to measure gene expression. We report transcriptome results for individual dopaminergic and GABAergic neurons isolated from midbrain cultures. We report that 100% of the live TH-eGFP cells that were harvested and sequenced were dopaminergic neurons. These techniques will have widespread applications in neuroscience and molecular biology.

In Parkinson&#39;s Disease (PD), Substantia Nigra (SNc) dopaminergic neurons degenerate, leading to motor dysfunction. Here we report a protocol for culturing ventral midbrain neurons from a mouse expressing eGFP driven by a Tyrosine Hydroxylase (TH) promoter sequence, harvesting individual fluorescent neurons from the cultures, and measuring their transcriptome using RNA-seq.

In Parkinson&#39;s Disease (PD) there is widespread neuronal loss throughout the brain with pronounced degeneration of dopaminergic neurons in the SNc, ...

An In Ovo Model for Testing Insulin-mimetic Compounds

Elevated blood glucose levels in type 2 diabetes mellitus (T2DM), a complex and multifactorial metabolic disease, are caused by insulin resistance and &#946;-cell failure. Various strategies, including the injection of insulin or the usage of insulin-sensitizing drugs, were pursued to treat T2DM or at least reduce the symptoms. In addition, the application of herbal compounds has attracted increasing attention. Thus, it is necessary to find efficient test systems to identify and characterize insulin-mimetic compounds. Here we developed a modified chick embryo model, which enables testing of synthetic compounds and herbal extracts with insulin-mimetic properties. Using a fluorescence microscopy-based primary screen, which quantifies the translocation of Glucose transporter 4 (Glut4) to the plasma membrane, we were able to identify compounds, mainly herbal extracts, which lead to an increase of intracellular glucose concentrations in adipocytes. However, the efficacy of these substances requires further verification in a living organism. Thus, we used an in-ovo approach to identify their blood glucose-reducing properties. The approval by an ethics committee is not needed since the use of chicken embryos during the first two-thirds of embryonic development is not considered an animal experiment. Here, the application of this model is described in detail.

An In Ovo Model for Testing Insulin-mimetic Compounds

In this study, we describe an in-ovo system as a promising tool to test insulin-mimetic compounds in a living organism. The main advantages include adequate throughput rates and acceptable costs, which enable the identification of phytochemicals with insulin-mimetic properties.

Elevated blood glucose levels in type 2 diabetes mellitus (T2DM), a complex and multifactorial metabolic disease, are caused by insulin resistance and ...

Combined In Vivo Anatomical and Functional Tracing of Ventral Tegmental Area Glutamate Terminals in the Hippocampus

Optogenetic modulation of neuron sub-populations in the brain has allowed researchers to dissect neural circuits in vivo and ex vivo. This provides a premise for determining the role of neuron types within a neural circuit, and their significance in information encoding relative to learning. Likewise, the method can be used to test the physiological significance of two or more connected brain regions in awake and anesthetized animals. The current study demonstrates how VTA glutamate neurons modulate the firing rate of putative pyramidal neurons in the CA1 (hippocampus) of anesthetized mice. This protocol employs adeno-associated virus (AAV)-dependent labeling of VTA glutamate neurons for the tracing of VTA presynaptic glutamate terminals in the layers of the hippocampus. Expression of light-controlled opsin (channelrhodopsin; hChR2) and fluorescence protein (eYFP) harbored by the AAV vector permitted anterograde tracing of VTA glutamate terminals, and photostimulation of VTA glutamate neuron cell bodies (in the VTA). High-impedance acute silicon electrodes were positioned in the CA1 to detect multi-unit and single-unit responses to VTA photostimulation in vivo. The results of this study demonstrate the&#160;layer-dependent distribution of presynaptic VTA glutamate terminals in the hippocampus (CA1, CA3, and DG). Also, the photostimulation of VTA glutamate neurons increased the firing and burst rate of putative CA1 pyramidal units in vivo.

The current protocol demonstrates a simple method for tracing of ventral tegmental area (VTA) glutamate projections to the hippocampus. Photostimulation of VTA glutamate neurons was combined with CA1 recording to demonstrate how VTA glutamate terminals modulate CA1 putative pyramidal firing rate in vivo.

Optogenetic modulation of neuron sub-populations in the brain has allowed researchers to dissect neural circuits in vivo and ex vivo. This provides a ...

Methods Article

In ovo Expression of MicroRNA in Ventral Chick Midbrain