Name: inducing cre-lox recombination in mouse cerebral cortex through in utero electroporation
Uploaded: 2017-11-17T15:00:00
Description: Watch this Scientific Journal Video about Inducing Cre-lox Recombination in Mouse Cerebral Cortex Through In Utero Electroporation at JoVE.com

The authors thank the generous support of the James Madison University Department of Biology and the James Madison University Light Microscopy and Imaging Facility. Dr. Mark L. Gabriele for helpful advice regarding young postnatal tissue preparation, and Drs. Justin W. Brown and Corey L. Cleland for generous coordination of surgical materials and space. This research was funded in part by a Collaborative Research Grant by 4-VA, a collaborative partnership for advancing the Commonwealth of Virginia (G.S.V.), and by a Virginia Academy of Science Small Project Research Grant (G.S.V.). Support has been generously provided by a Betty Jo Loving Butler &#39;58 Endowment for Undergraduate Research Scholarship (to K.M.B.), a Farrell Summer Research Scholarship (to K.M.B.), a James Madison University Second Century Scholarship (to K.M.B.), a James Madison University Centennial Scholarship (to C.J.H.), a James Madison University Lucy Robinson Search &#39;30 Memorial Scholarship (to Z.L.H.), and a James Madison University College of Science and Mathematics Faculty Assistance Grant (to G.S.V.).

Methods described here have been approved by the Animal Care and Use Committee (ACUC) of James Madison University, and are in accordance and compliance with all relevant regulatory and institutional guidelines.
1. Mouse Set-up
<ol>
	<li>House a young (&#62;P60) male and female homozygous floxed mouse together to set up a breeder pair25. 
	NOTE: A good negative control is to set up an additional breeder pair of wildtype mice, in which Cre recombinase expression wi...

<ol>
	<li>Southwell, D. G., Froemke, R. C., Alvarez-Buylla, A., Stryker, M. P., Gandhi, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cortical+plasticity+induced+by+inhibitory+neuron+transplantation.">Cortical plasticity induced by inhibitory neuron transplantation.</a> Science. 327 (5969), 1145-1148 (2010).</li><li>Hanson, J. E., Madison, D. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Presynaptic+FMR1+genotype+influences+the+degree+of+synaptic+connectivity+in+a+mosaic+mouse+model+of+fragile+X+syndrome.">Presynaptic FMR1 genotype influences the degree of synaptic connectivity in a mosaic mouse model of fragile X syndrome.</a> J. Neurosci. 27 (15), 4014-4018 (2007).</li><li>Patel, A. B., Hays, S. A., Bureau, I., Huber, K. M., Gibson, J. 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Here, we introduce the combination of in utero electroporation with Cre recombinase in floxed mice to generate mosaic brain tissue. An advantage of this approach is that a new mouse line does not need to be generated each time a different cellular subtype is to be targeted: in utero electroporation can be used to target excitatory neurons, inhibitory neurons, or glia depending on the time and location of electroporation15,16,<sup clas...

Generating a genetic mosaic is a classic experimental paradigm for understanding the function of a gene of interest. To determine if a gene is necessary for a cellular phenotype, the simplest approach is causing a loss of function of the gene throughout the organism (e.g. knockout). However, to determine if a gene is required specifically in a certain cell type, knockout of the gene throughout the organism is not a valid approach. Instead, a method is required that will cause the loss of function of a gene in a given cell while it is surrounded by wildtype (i.e. genetically unperturbed) tissue&#8212;in other words, creating mosaic tissue. If the mutant cell shows a mutant phenotype, but surrounding wildtype cells do not, the gene functions in a cell-autonomous manner. Analysis of mosaic tissue, in which mutant cells are surrounded by wildtype tissue, is ideal for understanding cell-autonomous functions of genes, especially in the brain where neurons and glia form a vast interconnected network of tissue.
Several forms of mosaic brain tissue have provided powerful models to investigate cell-autonomous functions of genes. Studies focused on neuronal transplantation1, female X-linked mosaicism2,3,4, and endogenous somatic mosaicism5,6 have drawn their conclusions based on mosaic brain tissue. Conditional deletion of a gene through the Cre-lox recombination system is a method that takes full advantage of the great availability of transgenic mouse lines. In this method, two loxP sites are introduced on either side of a required sequence of a gene (such as an exon), leaving it flanked by loxP sites that both face in the same direction (&#34;floxed&#34;). Cre recombinase excises the sequence between the loxP sites7. Cre-mediated recombination can be achieved by crossing floxed mice to another mouse line expressing Cre recombinase along with a fluorescent marker in a subset of cells (&#34;Cre reporter line&#34;). This has been demonstrated in a variety of ways to uncover the functions of a gene in subsets of cells, such as excitatory neurons or astrocytes8. Cre reporter lines can express CreERT2 to allow Cre-mediated recombination to be drug-inducible (single-neuron labeling with inducible Cre-mediated knockout, or SLICK)9. In another strategy called mosaic analysis with double markers (MADM)10,11, Cre-mediated interchromosomal recombination allows a homozygous mutant to be created alongside heterozygous tissue. In these approaches, a new line of mice needs to be produced each time for each candidate gene or cellular subtype that is tested. Alternatively, Cre recombinase can be introduced postnatally through iontophoresis12 or through viral vectors (e.g. adeno-associated viruses13 or lentiviruses14 carrying cellular subtype-specific promoters). This strategy creates strong and postnatal labeling. To target developing cerebral cortical neurons sparsely and prenatally, an ideal strategy is in utero electroporation of Cre recombinase with a fluorescent marker.
In addition to combining Cre-lox recombination through in utero electroporation to produce mosaic tissue in vivo, we introduce several adaptations to procedures from other published protocols15,16,17,18,19,20,21. We provide information to improve success in breeding timed-pregnant females. We also outline our two strategies to introduce sparse and bright labeling of neurons in cortical tissue: One strategy is to titrate the levels of a single construct coding for Cre recombinase and a fluorescent marker22. Another strategy is to use the &#34;Supernova&#34; system, designed specifically with these parameters in mind23,24. Additionally, we offer improvements on producing consistent microinjection pipettes and simplifications to the in utero electroporation surgery. Finally, we outline critical steps in a simplified histological preparation that permits the analysis of dendritic spines and dendritic and axonal arbors, without further staining or immunohistochemistry.

<table>
	<tbody>
		<tr>
			<td>C57BL/6J mice</td>
			<td>The Jackson Laboratory</td>
			<td>#000664</td>
			<td>See &#34;1. Mouse set-up&#34; (step 1.1, &#34;wildtype mice&#34;)</td>
		</tr>
		<tr>
			<td>GFP.Cre empty vector</td>
			<td>AddGene</td>
			<td>#20781</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.1 &#34;single DNA construct that codes for Cre recombinase as well as a fluorescent marker&#34;). GFP.Cre empty vector was a gift from Tyler Jacks.</td>
		</tr>
		<tr>
			<td>pK029.CAG-loxP-stop-loxP-RFP-ires-tTA-WPRE (Supernova)</td>
			<td>AddGene</td>
			<td>#69138</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.1 &#34;Supernova&#34; system) and http://snsupport.webcrow.jp/. pK029.CAG-loxP-stop-loxP-RFP-ires-tTA-WPRE (Supernova) was a gift from Takuji Iwasato.</td>
		</tr>
		<tr>
			<td>pK031.TRE-Cre (Supernova)</td>
			<td>AddGene</td>
			<td>#69136</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.1 &#34;Supernova&#34; system) and http://snsupport.webcrow.jp/. pK031.TRE-Cre (Supernova) was a gift from Takuji Iwasato.</td>
		</tr>
		<tr>
			<td>pK038.CAG-loxP-stop-loxP-EGFP-ires-tTA-WPRE (Supernova)</td>
			<td>AddGene</td>
			<td>#85006</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.1 &#34;Supernova&#34; system) and http://snsupport.webcrow.jp/. pK038.CAG-loxP-stop-loxP-EGFP-ires-tTA-WPRE (Supernova) was a gift from Takuji Iwasato.</td>
		</tr>
		<tr>
			<td>EndoFree Plasmid Maxi Kit (10)</td>
			<td>Qiagen</td>
			<td>#12362</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.3 &#34;endotoxin-free plasmid purification kit&#34;)</td>
		</tr>
		<tr>
			<td>Trypan Blue powder, BioReagent grade</td>
			<td>Sigma</td>
			<td>T6146-5G</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.5 &#34;trypan blue&#34;)</td>
		</tr>
		<tr>
			<td>Sodium Chloride, ACS, 2.5 kg</td>
			<td>VWR</td>
			<td>BDH9286-2.5KG</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.5 &#34;NaCl&#34;)</td>
		</tr>
		<tr>
			<td>Potassium Chloride, ACS, 500 g</td>
			<td>VWR</td>
			<td>#97061-566</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.5 &#34;KCl&#34;)</td>
		</tr>
		<tr>
			<td>Sodium phosphate dibasic, ReagentPlus, 100 g</td>
			<td>Sigma-Aldrich</td>
			<td>S0876-100G</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.5 &#34;Na2HPO4&#34;)</td>
		</tr>
		<tr>
			<td>Potassium phosphate monobasic, ReagentPlus, 100 g</td>
			<td>Sigma-Aldrich</td>
			<td>P5379-100G</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.5 &#34;KH2PO4&#34;)</td>
		</tr>
		<tr>
			<td>Hydrochloric acid, ACS reagent, 500 mL</td>
			<td>Fisher Scientific</td>
			<td>A144-500</td>
			<td>See &#34;2. DNA set-up&#34; (step 2.5 &#34;HCl&#34;)</td>
		</tr>
		<tr>
			<td>P-97 Micropipette Puller</td>
			<td>Sutter Instrument</td>
			<td>P-97</td>
			<td>See &#34;3. Pipette set-up&#34; (step 3.1 &#34;glass capillary puller&#34;)</td>
		</tr>
		<tr>
			<td>3.0 mm wide trough filament</td>
			<td>Sutter Instrument</td>
			<td>FT330B</td>
			<td>See &#34;3. Pipette set-up&#34; (step 3.1 &#34;glass capillary puller&#34;)</td>
		</tr>
		<tr>
			<td>Thin Wall Glass Capillaries, 4&#34;, 1 / 0.75 OD/ID</td>
			<td>World Precision Instruments</td>
			<td>TW100-4</td>
			<td>See &#34;3. Pipette set-up&#34; (step 3.1.1 &#34;glass capillary&#34;)</td>
		</tr>
		<tr>
			<td>Single Ply Soft-Tech Wipes, 4.5&#34;</td>
			<td>Phenix</td>
			<td>LW-8148</td>
			<td>See &#34;3. Pipette set-up&#34; (step 3.2.1 &#34;single-ply task wipe&#34;); other single-ply wipes (e.g. Kimwipes) can be used.</td>
		</tr>
		<tr>
			<td>Graefe Forceps, 7 cm, Straight, 0.7 mm 1x2 Teeth</td>
			<td>World Precision Instruments</td>
			<td>#14140</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.1 &#34;Graefe forceps&#34;)</td>
		</tr>
		<tr>
			<td>Iris Scissors, 11.5 cm, Straight, 12-pack</td>
			<td>World Precision Instruments</td>
			<td>#503708-12</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.1 &#34;iris scissors&#34;)</td>
		</tr>
		<tr>
			<td>Hartman Mosquito Forceps, 9 cm, Straight, 12-pack</td>
			<td>World Precision Instruments</td>
			<td>#503728-12</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.1 &#34;Hartman mosquito forceps&#34;)</td>
		</tr>
		<tr>
			<td>General Purpose Non-Woven Sponges, 2&#34; x 2&#34;, 4-ply</td>
			<td>Medrepexpress</td>
			<td>#2204-c</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.1 &#34;non-woven gauze sponges&#34;)</td>
		</tr>
		<tr>
			<td>Ring Tipped Forceps, 10 cm, Straight, 2.2mm ID</td>
			<td>World Precision Instruments</td>
			<td>#503203</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.1 &#34;ring-tipped forceps&#34;)</td>
		</tr>
		<tr>
			<td>Pyrex petri dishes complete, O.D. &#215; H 100 mm &#215; 20 mm</td>
			<td>Sigma-Aldrich</td>
			<td>CLS3160102-12EA</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.1 &#34;Petri dishes&#34;)</td>
		</tr>
		<tr>
			<td>Flat Type Instrument Tray, Stainless Steel, 13-5/8&#34; x 9-3/4&#34; x 5/8&#34;</td>
			<td>Amazon</td>
			<td>B007SHGAHA</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.1 &#34;stainless steel tray&#34;)</td>
		</tr>
		<tr>
			<td>Platinum Tweezertrode, 5 mm</td>
			<td>BTX</td>
			<td>#45-0489</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.3 and 4.16 &#34;tweezer-type electrodes&#34;)</td>
		</tr>
		<tr>
			<td>ECM 830 Foot Pedal</td>
			<td>BTX</td>
			<td>#45-0211</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.3 and 4.17 &#34;foot pedal&#34;)</td>
		</tr>
		<tr>
			<td>ECM 830 Generator</td>
			<td>BTX</td>
			<td>#45-0052</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.3 &#34;generator&#34;)</td>
		</tr>
		<tr>
			<td>Single Animal Isoflurane Anesthesia System with Small Induction Box</td>
			<td>Harvard Apparatus</td>
			<td>#72-6468</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.4 and 4.6 &#34;nose cone&#34;, step 4.4 &#34;induction chamber&#34;)</td>
		</tr>
		<tr>
			<td>Ophthalmic ointment</td>
			<td>Hanna Pharmaceutical Supply Co</td>
			<td>#0536108691</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.7 &#34;veterinary ophthalmic ointment&#34;)</td>
		</tr>
		<tr>
			<td>Space Gel (AIMS)</td>
			<td>VWR</td>
			<td>#95059-640</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.8 &#34;sealed pouch filled with supersaturated salt solution&#34;)</td>
		</tr>
		<tr>
			<td>Hair Remover Gel Cream, Sensitive Formula</td>
			<td>Veet</td>
			<td>#062200809951</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.9 &#34;depilatory cream&#34;)</td>
		</tr>
		<tr>
			<td>10ul Low Retention Tip Starter (960 tips/pk)</td>
			<td>Phenix Research Products</td>
			<td>TSP-10LKIT</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.12 &#34;sterile 10 &#181;L micropipette tip&#34;)</td>
		</tr>
		<tr>
			<td>Aspirator tube assemblies for calibrated microcapillary pipettes</td>
			<td>Sigma-Aldrich</td>
			<td>A5177</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.15 &#34;aspirator tube assembly&#34;)</td>
		</tr>
		<tr>
			<td>Braided Absorbable Suture, 4-0, Needle NFS-2(FS-2), 27&#34;</td>
			<td>Medrepexpress</td>
			<td>MV-J397</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.19 &#34;absorbable sutures&#34;)</td>
		</tr>
		<tr>
			<td>&#8220;LiquiVet Rapid&#8221; Tissue Adhesive</td>
			<td>Medrepexpress</td>
			<td>VG3</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.20 &#34;tissue adhesive&#34;)</td>
		</tr>
		<tr>
			<td>Hypodermic syringes, polypropylene, Luer lock tip, capacity 1.0 mL</td>
			<td>Sigma-Aldrich</td>
			<td>Z551546-100EA</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.21 &#34;1 mL syringe&#34;)</td>
		</tr>
		<tr>
			<td>BD Precisionglide syringe needles gauge 26, L 1/2 in.</td>
			<td>Sigma-Aldrich</td>
			<td>Z192392-100EA</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.21 &#34;26G, &#189;&#8221; needle&#34;)</td>
		</tr>
		<tr>
			<td>Nestlets Nesting Material</td>
			<td>Ancare</td>
			<td>NES3600</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.24 &#34;nesting materials&#34;)</td>
		</tr>
		<tr>
			<td>Sunflower Seeds, Black Oil, Sterile</td>
			<td>Bio-Serv</td>
			<td>S5137</td>
			<td>See &#34;4. In utero electroporation&#34; (step 4.24 &#34;sunflower seeds&#34;)</td>
		</tr>
		<tr>
			<td>Paraformaldehyde, 97%</td>
			<td>Alfa Aesar</td>
			<td>A11313</td>
			<td>See &#34;5. Histology&#34; (step 5.1.1 &#34;PFA&#34;)</td>
		</tr>
		<tr>
			<td>Economy Tweezers #3, 11 cm, 0.2 x 0.4 mm tips</td>
			<td>World Precision Instruments</td>
			<td>#501976</td>
			<td>See &#34;5. Histology&#34; (step 5.5 &#34;tweezers&#34;)</td>
		</tr>
		<tr>
			<td>Agar powder</td>
			<td>Alfa Aesar</td>
			<td>#10752</td>
			<td>See &#34;5. Histology&#34; (step 5.8.1 &#34;agar&#34;)</td>
		</tr>
		<tr>
			<td>Single-edge razor blades, #9 blade</td>
			<td>Stanley Tools</td>
			<td>#11-515</td>
			<td>See &#34;5. Histology&#34; (step 5.9 &#34;single-edge razor blade&#34;)</td>
		</tr>
		<tr>
			<td>Specimen disc S D 50 mm</td>
			<td>Leica</td>
			<td>#14046327404</td>
			<td>See &#34;5. Histology&#34; (step 5.9 &#34;vibrating microtome specimen disc&#34;)</td>
		</tr>
		<tr>
			<td>Buffer tray S assembly</td>
			<td>Leica</td>
			<td>#1404630132</td>
			<td>See &#34;5. Histology&#34; (step 5.10 &#34;buffer tray&#34;)</td>
		</tr>
		<tr>
			<td>VT1000 S Vibratome</td>
			<td>Leica</td>
			<td>#14047235612</td>
			<td>See &#34;5. Histology&#34; (step 5.10 &#34;vibrating microtome&#34;)</td>
		</tr>
		<tr>
			<td>Double Edge Razor Blades</td>
			<td>Personna</td>
			<td>BP9020</td>
			<td>See &#34;5. Histology&#34; (step 5.10 &#34;blade&#34;)</td>
		</tr>
		<tr>
			<td>Knife Holder S</td>
			<td>Leica</td>
			<td>#14046230131</td>
			<td>See &#34;5. Histology&#34; (step 5.10 &#34;knife holder&#34;)</td>
		</tr>
		<tr>
			<td>Studio Elements Golden Taklon Short Handle Round Brush Set</td>
			<td>Amazon</td>
			<td>B0089KU6XE</td>
			<td>See &#34;5. Histology&#34; (step 5.12.1 &#34;fine tipped paintbrush&#34;)</td>
		</tr>
		<tr>
			<td>Superfrost Plus Slides</td>
			<td>Electron Microscopy Services</td>
			<td>#71869-11</td>
			<td>See &#34;5. Histology&#34; (step 5.12.1 &#34;microscope slide&#34;)</td>
		</tr>
		<tr>
			<td>ProLong Diamond Antifade Mountant, 10 ml</td>
			<td>Thermofisher</td>
			<td>P36970</td>
			<td>See &#34;5. Histology&#34; (step 5.12.3-5.12.4 &#34;mountant&#34;)</td>
		</tr>
		<tr>
			<td>Cover Glass, 24 x 50 mm, No. 1</td>
			<td>Phenix Research Products</td>
			<td>MS1415-10</td>
			<td>See &#34;5. Histology&#34; (step 5.12.4 &#34;coverslip&#34;)</td>
		</tr>
		<tr>
			<td>4&#8242;,6-Diamidino-2-phenylindole dihydrochloride (DAPI)</td>
			<td>Sigma-Aldrich</td>
			<td>D9542</td>
			<td>See &#34;5. Histology&#34; (step 5.13.1 &#34;DAPI&#34;)</td>
		</tr>
		<tr>
			<td>Fixed Stage Upright Microscope</td>
			<td>Olympus</td>
			<td>BX51WI</td>
			<td>See &#34;5. Histology&#34; (step 5.15 &#34;light microscope&#34;)</td>
		</tr>
		<tr>
			<td>Laser Scanning Confocal Microscope</td>
			<td>Nikon</td>
			<td>TE2000/C2si</td>
			<td>See &#34;5. Histology&#34; (step 5.15 &#34;confocal microscope&#34;)</td>
		</tr>
		<tr>
			<td>4x objective, NA = 0.20</td>
			<td>Nikon</td>
			<td>CFI Plan Apo Lambda 4X</td>
			<td>See &#34;5. Histology&#34; (step 5.15 &#34;low-power objective&#34;)</td>
		</tr>
		<tr>
			<td>20x objective, NA = 0.75</td>
			<td>Nikon</td>
			<td>CFI Plan Apo Lambda 20X</td>
			<td>See &#34;5. Histology&#34; (step 5.15 &#34;medium-power objective&#34;)</td>
		</tr>
		<tr>
			<td>60x objective, NA = 1.40</td>
			<td>Nikon</td>
			<td>CFI Plan Apo VC 60X Oil</td>
			<td>See &#34;5. Histology&#34; (step 5.15 &#34;high-power objective&#34;)</td>
		</tr>
	</tbody>
</table>

inducing cre-lox recombination in mouse cerebral cortex through in utero electroporation

Cell-autonomous neuronal functions of genes can be revealed by causing loss or gain of function of a gene in a small and sparse population of neurons. To do so requires generating a mosaic in which neurons with loss or gain of function of a gene are surrounded by genetically unperturbed tissue. Here, we combine the Cre-lox recombination system with in utero electroporation in order to generate mosaic brain tissue that can be used to study the cell-autonomous function of genes in neurons. DNA constructs (available through repositories), coding for a fluorescent label and Cre recombinase, are introduced into developing cortical neurons containing genes flanked with loxP sites in the brains of mouse embryos using in utero electroporation. Additionally, we describe various adaptations to the in utero electroporation method that increase survivability and reproducibility. This method also involves establishing a titer for Cre-mediated recombination in a sparse or dense population of neurons. Histological preparations of labeled brain tissue do not require (but can be adapted to) immunohistochemistry. The constructs used guarantee that fluorescently labeled neurons carry the gene for Cre recombinase. Histological preparations allow morphological analysis of neurons through confocal imaging of dendritic and axonal arbors and dendritic spines. Because loss or gain of function is achieved in sparse mosaic tissue, this method permits the study of cell-autonomous necessity and sufficiency of gene products in vivo.

The single construct GFP.Cre (see list of materials) was electroporated at E15.5 and visualized at P14. Depending on the concentration of the construct and the volume of injection, a sparse or dense result can be obtained22,26. For example, injection of 1 &#181;L of 2 mg/mL GFP.Cre results in a sparse distribution of labeled cells, some of which can be bright (Figure 1A), and localized in layer II/III...

Watch this Scientific Journal Video about Inducing Cre-lox Recombination in Mouse Cerebral Cortex Through In Utero Electroporation at JoVE.com

Inducing Cre-lox Recombination in Mouse Cerebral Cortex Through In Utero Electroporation

Cell-autonomous functions of genes in the brain can be studied by inducing loss or gain of function in sparse populations of cells. Here, we describe in utero electroporation to deliver Cre recombinase into sparse populations of developing cortical neurons with floxed genes to cause loss of function in vivo.

Inducing Cre-lox Recombination in Mouse Cerebral Cortex Through In Utero Electroporation

Cell-autonomous neuronal functions of genes can be revealed by causing loss or gain of function of a gene in a small and sparse population of neurons. To ...

The overall goal of this procedure is to generate a genetic mosaic in mouse cerebral cortex by inducing Cre-Lox recombination through in utero electroporation. This method of generating genetic mosaics can help answer key questions in neurobiology. Such as determining if a gene is necessary for a given neuronal phenotype in a cell autonomous manner.The main advantage of this technique is that the effective Cre-Lox recombination system is combined with an equally effective gene delivery technique in utero electroporation. Though this method is focused on targeting layer two-three cortical neurons, it can be used to target neurons in other cortical layers depths. When we tried to make genetic mosaics in our brain tissue, we encountered several problems in getting our experimental animals to survive after birth, so we introduced several simplifications and refinements to our technique.Prepare a pipette with a very long taper and very fine tip, typical of pipettes for embryonic stem cell injection or nuclear transfer by first inserting the glass capillary into the pipette puller. After fastening the clamps, activate the program to pulling protocol, creating a taper on the glass capillary. Ensure that the taper length is between 10 and 15 mm using a compound light microscope.Next, to break the tip of the pipette center a single-ply task wipe over a 50-mL beaker and stretch it taut with one hand. With the other hand, push the pulled pipette, taper side down, perpendicularly through the center of the wipe causing a clean break in the taper. Check the size of the opening under a compound light microscope.Then calibrate the pipette by aspirating 1 mcL of 0.4%Trypan blue and PBS into a partially filled pipette and graduate the pipette with 1-mcL markings based on the height of 1 mcL in the pipette. Use the calibrated pipette to graduate other pulled pipettes before discarding. Place the pipettes in the pipette holder free from dust and other particles.After deeply anesthetizing a pregnant mouse at E-15.5, test the righting reflex by gently tilting the induction chamber and noting the response of the mouse. If the righting reflex is absent, transfer the mouse to the surgical preparation area and administer inhaled isoflurane through a nose cone to maintain a surgical plane of anesthesia. Use forceps to test the pedal reflex to verify anesthetization.Monitor respiratory rate in effort, looking for deep, regular breathing and that mucous membranes are pink in color and moist. Apply enough veterinary ophthalmic ointment over the eyes to cover them completely for protection against drying. Massage depilatory cream onto the abdominal area with cotton swabs until the abdominal fur dissolves.Then wipe off the abdominal fur. Carefully clean off any remaining residue and depilatory cream with 70%ethanol and cotton swabs. Apply iodine-based scrub solution to the abdominal area in a circular motion.Then use a surgical drape to isolate the surgical area and maintain sterile conditions. After a making a 2-cm ventral midline incision in the skin, find the linea alba to visualize the midline of the rectus abdominis. Pull the muscle up and away from the abdomen and make a 2-cm midline incision to expose the abdominal cavity using aseptic techniques.Using a sterile 10-mcL micropipette tip, dispense carprofen into the abdominal cavity for analgesia. Next, clamp one Hartmann mosquito forceps on the left edge of the rectus abdominis incision. Rest the forceps on overturned Petri dish to the left of the incision, keeping the left side of the incision open.After clamping the right side of the incision in a similar manner, place gauze sponge around the area of the incision. Using ring forceps without an attached limit screw, pull on the uterus between any two neighboring embryos without crushing or injuring any tissue. Begin pulling out all embryos through the incision, laying them on top of the gauze sponge.Connect a calibrated pipette to the aspirator tube assembly and inject exactly 1 mcL of DNA solution prepared through the uterine wall into a lateral ventricle of each embryo. Use the thumb and forefinger to manipulate the embryos, allowing the embryos to be pushed gently against the uterine wall during injection. The lateral ventricles appear as two darker patches on the dorsal telencephalon of the embryo.Confirm successful injection by observing Trypan blue filling the lateral ventricle. After injecting all embryos, place the cathode of tweezer-type electrodes on the uterus, directly over the medial and caudal cortex to target the visual cortex. Place the anode just inferior and anterior to the embryo's head.With the foot pedal, trigger the delivery of 550-ms pulses of 50 volts separated by a 950-ms interval. After electroporating all embryos, return the uterus to the abdominal cavity in the same orientation it was found. Use saline to lubricate the uterus while guiding it manually and extremely gently, taking care not to displace embryos from their position in the uterus.Close the abdominal muscles with absorbable sutures. Use a simple interrupted stitch, tying the ends with a surgeon's knot. Close the skin layer with absorbable sutures.Apply a small amount of tissue adhesive to seal the wound. Apply tissue adhesive to the knots to prevent unfastening. Use a micropipette to remove any tissue adhesive surrounding the wound that can be aspirated.Once the tissue adhesive is dry, remove the animal from isoflurane and allow the female to recover alone in a warm cage. Continue to monitor the mouse until it is fully recovered and behaving normally. Once removed, place female back in cage with the male.Place the skull on a flat surface with single-ply task wipes moistened with 1-x PBS. Using tweezers, first remove the occipital bone. Then carefully remove the parietal bones, removing the tweezers out and away from the surface of the brain.Carefully remove any meninges to prevent damage to the cortex. Wedge the back of the tweezers under the brain along the skull to sever any cranial nerves and remove the brain. Use a single-edge razor blade to make a coronal cut approximately 0.5 mm rostral to bregma, and another coronal cut approximately 0.5 mm caudal to the tissue of interest.Tissue block is now ready for sectioning. Injection of 1 mcL of 2 mg/mL of GFP Cre results in a sparse distribution of labeled cells, some of which can be bright. Because the tissue is sectioned at 100 microns, most of the dendritic arbors are preserved.When the in utero electroporation is performed at embryonic day 15.5, labeling occurs across cortical layers two and three. Dendritic spines can be observed at high magnifications. Injection of 1.5 mcL of 2 mg/mL of GFP Cre results in very dense labeling, which can be suboptimal as it is difficult to track the source of neurites and dendritic spines.However, by selecting a bright cell in the periphery of the labeled area, it is still possible to image a neuron and its processes. Alternatively, injection of SuperNova constructs results in a sparse distribution of layer two-three neurons that are very brightly labeled. Once mastered the in utero electroporation surgery will take less than 30 minutes if it is performed properly.While attempting this procedure with other DNA constructs, it's important to remember to try different concentrations and volumes, this will help achieve the desired sparseness of labeling required for mosaic analysis. Our representative results used either a single construct or recently invented SuperNova construct. In the latter, we found that we could achieve excellent sparse labeling, while maximizing the brightness of the neurons.This technique could be adapted to create mosaic brain tissue in other ways. For example, CRISPR and Cas9 gene editing can be combined with in utero electroporation, or Cre-Lox recombination could be combined with intraventricular injection of viral vectors. After watching this video, you should have a good understanding of several simplified and refined techniques used to achieve a sparse genetic mosaic, so that you can combine Cre-Lox recombination and in utero electroporation together.We wish you the best of luck.

inducing-cre-lox-recombination-mouse-cerebral-cortex-through-utero

Research

JoVE Journal

Neuroscience

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

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

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

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

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

Mouse in Utero Electroporation: Controlled Spatiotemporal Gene Transfection

In order to understand the function of genes expressed in specific region of the developing brain, including signaling molecules and axon guidance molecules, local gene transfer or knock- out is required. Gene targeting knock-in or knock-out into local regions is possible to perform with combination with a specific CRE line, which is laborious, costly, and time consuming. Therefore, a simple transfection method, an in utero electroporation technique, which can be performed with short time, will be handy to test the possible function of candidate genes prior to the generation of transgenic animals 1,2. In addition to this, in utero electroporation targets areas of the brain where no specific CRE line exists, and will limit embryonic lethality 3,4. Here, we present a method of in utero electroporation combining two different types of electrodes for simple and convenient gene transfer into target areas of the developing brain. First, a unique holding method of embryos using an optic fiber optic light cable will make small embryos (from E9.5) visible for targeted DNA solution injection into ventricles and needle type electrodes insertion to the targeted brain area 5,6. The patterning of the brain such as cortical area occur at early embryonic stage, therefore, these early electroporation from E9.5 make a big contribution to understand entire area patterning event. Second, the precise shape of a capillary prevents uterine damage by making holes by insertion of the capillary. Furthermore, the precise shape of the needle electrodes are created with tungsten and platinum wire and sharpened using sand paper and insulated with nail polish 7, a method which is described in great detail in this protocol. This unique technique allows transfection of plasmid DNA into restricted areas of the brain and will enable small embryos to be electroporated. This will help to, open a new window for many scientists who are working on cell differentiation, cell migration, axon guidance in very early embryonic stage. Moreover, this technique will allow scientists to transfect plasmid DNA into deep parts of the developing brain such as thalamus and hypothalamus, where not many region-specific CRE lines exist for gain of function (GOF) or loss of function (LOF) analyses.

Mouse in Utero Electroporation: Controlled Spatiotemporal Gene Transfection

A gene transfer method into the developing mouse brain is described by using a unique surgical method and special shape of electrodes. This unique technique allows transfection of plasmid DNA temporally and spatially, which will aid many neuroscientists in studying brain development.

In order to understand the function of genes expressed in specific region of the developing brain, including signaling molecules and axon guidance ...

Detection of Microregional Hypoxia in Mouse Cerebral Cortex by Two-photon Imaging of Endogenous NADH Fluorescence

The brain's ability to function at high levels of metabolic demand depends on continuous oxygen supply through blood flow and tissue oxygen diffusion. Here we present a visualized experimental and methodological protocol to directly visualize microregional tissue hypoxia and to infer perivascular oxygen gradients in the mouse cortex. It is based on the non-linear relationship between nicotinamide adenine dinucleotide (NADH) endogenous fluorescence intensity and oxygen partial pressure in the tissue, where observed tissue NADH fluorescence abruptly increases at tissue oxygen levels below 10 mmHg1. We use two-photon excitation at 740 nm which allows for concurrent excitation of intrinsic NADH tissue fluorescence and blood plasma contrasted with Texas-Red dextran. The advantages of this method over existing approaches include the following: it takes advantage of an intrinsic tissue signal and can be performed using standard two-photon in vivo imaging equipment; it permits continuous monitoring in the whole field of view with a depth resolution of ~50 &mu;m. We demonstrate that brain tissue areas furthest from cerebral blood vessels correspond to vulnerable watershed areas which are the first to become functionally hypoxic following a decline in vascular oxygen supply. This method allows one to image microregional cortical oxygenation and is therefore useful for examining the role of inadequate or restricted tissue oxygen supply in neurovascular diseases and stroke.

Here we describe a method to directly visualize microregional tissue hypoxia in the mouse cortex in vivo. It is based on concurrent two-photon imaging of nicotinamide adenine dinucleotide (NADH) and the cortical microcirculation. This method is useful for high resolution analysis of tissue oxygen supply.

The brain's ability to function at high levels of metabolic demand depends on continuous oxygen supply through blood flow and tissue oxygen diffusion. ...

Methods for Study of Neuronal Morphogenesis: Ex vivo RNAi Electroporation in Embryonic Murine Cerebral Cortex

The cerebral cortex directs higher cognitive functions. This six layered structure is generated in an inside-first, outside-last manner, in which the first born neurons remain closer to the ventricle while the last born neurons migrate past the first born neurons towards the surface of the brain1. In addition to neuronal migration2, a key process for normal cortical function is the regulation of neuronal morphogenesis3. While neuronal morphogenesis can be studied in vitro in primary cultures, there is much to be learned from how these processes are regulated in tissue environments.
We describe techniques to analyze neuronal migration and/or morphogenesis in organotypic slices of the cerebral cortex4,6. A pSilencer modified vector is used which contains both a U6 promoter that drives the double stranded hairpin RNA and a separate expression cassette that encodes GFP protein driven by a CMV promoter7-9. Our approach allows for the rapid assessment of defects in neurite outgrowth upon specific knockdown of candidate genes and has been successfully used in a screen for regulators of neurite outgrowth8. Because only a subset of cells will express the RNAi constructs, the organotypic slices allow for a mosaic analysis of the potential phenotypes. Moreover, because this analysis is done in a near approximation of the in vivo environment, it provides a low cost and rapid alternative to the generation of transgenic or knockout animals for genes of unknown cortical function. Finally, in comparison with in vivo electroporation technology, the success of ex vivo electroporation experiments is not dependant upon proficient surgery skill development and can be performed with a shorter training time and skill.

Methods for Study of Neuronal Morphogenesis: Ex vivo RNAi Electroporation in Embryonic Murine Cerebral Cortex

To conduct a rapid assessment of the function of genes in the development of cerebral cortex, we describe methods involving the ex vivo electroporation of plasmids co-expressing inhibitory RNA (RNAi) and GFP in murine embryonic cortex. This protocol is amenable to the study of various aspects of neurodevelopment such as neurogenesis, neuronal migration and neuronal morphogenesis including dendrite and axon outgrowth.

The cerebral cortex directs higher cognitive functions. This six layered structure is generated in an inside-first, outside-last manner, in which the ...

Visualization and Genetic Manipulation of Dendrites and Spines in the Mouse Cerebral Cortex and Hippocampus using In utero Electroporation

In utero electroporation (IUE) has become a powerful technique to study the development of different regions of the embryonic nervous system 1-5. To date this tool has been widely used to study the regulation of cellular proliferation, differentiation and neuronal migration especially in the developing cerebral cortex 6-8. Here we detail our protocol to electroporate in utero the cerebral cortex and the hippocampus and provide evidence that this approach can be used to study dendrites and spines in these two cerebral regions.
Visualization and manipulation of neurons in primary cultures have contributed to a better understanding of the processes involved in dendrite, spine and synapse development. However neurons growing in vitro are not exposed to all the physiological cues that can affect dendrite and/or spine formation and maintenance during normal development. Our knowledge of dendrite and spine structures in vivo in wild-type or mutant mice comes mostly from observations using the Golgi-Cox method 9. However, Golgi staining is considered to be unpredictable. Indeed, groups of nerve cells and fiber tracts are labeled randomly, with particular areas often appearing completely stained while adjacent areas are devoid of staining. Recent studies have shown that IUE of fluorescent constructs represents an attractive alternative method to study dendrites, spines as well as synapses in mutant / wild-type mice 10-11 (Figure 1A). Moreover in comparison to the generation of mouse knockouts, IUE represents a rapid approach to perform gain and loss of function studies in specific population of cells during a specific time window. In addition, IUE has been successfully used with inducible gene expression or inducible RNAi approaches to refine the temporal control over the expression of a gene or shRNA 12. These advantages of IUE have thus opened new dimensions to study the effect of gene expression/suppression on dendrites and spines not only in specific cerebral structures (Figure 1B) but also at a specific time point of development (Figure 1C).
Finally, IUE provides a useful tool to identify functional interactions between genes involved in dendrite, spine and/or synapse development. Indeed, in contrast to other gene transfer methods such as virus, it is straightforward to combine multiple RNAi or transgenes in the same population of cells. 
In summary, IUE is a powerful method that has already contributed to the characterization of molecular mechanisms underlying brain function and disease and it should also be useful in the study of dendrites and spines.

Visualization and Genetic Manipulation of Dendrites and Spines in the Mouse Cerebral Cortex and Hippocampus using In utero Electroporation

This article describes in detail a protocol to electroporate in utero the cerebral cortex and the hippocampus at E14.5 in mice. We also show that this is a valuable method to study dendrites and spines in these two cerebral regions.

In utero electroporation (IUE) has become a powerful technique to study the development of different regions of the embryonic nervous system 1-5. To date ...

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 ...

Generation of Topically Transgenic Rats by In utero Electroporation and In vivo Bioluminescence Screening

In utero electroporation (IUE) is a technique which allows genetic modification of cells in the brain for investigating neuronal development. So far, the use of IUE for investigating behavior or neuropathology in the adult brain has been limited by insufficient methods for monitoring of IUE transfection success by non-invasive techniques in postnatal animals. 
 For the present study, E16 rats were used for IUE. After intraventricular injection of the nucleic acids into the embryos, positioning of the tweezer electrodes was critical for targeting either the developing cortex or the hippocampus. 
 Ventricular co-injection and electroporation of a luciferase gene allowed monitoring of the transfected cells postnatally after intraperitoneal luciferin injection in the anesthetized live P7 pup by in vivo bioluminescence, using an IVIS Spectrum device with 3D quantification software. 
 Area definition by bioluminescence could clearly differentiate between cortical and hippocampal electroporations and detect a signal longitudinally over time up to 5 weeks after birth. This imaging technique allowed us to select pups with a sufficient number of transfected cells assumed necessary for triggering biological effects and, subsequently, to perform behavioral investigations at 3 month of age. As an example, this study demonstrates that IUE with the human full length DISC1 gene into the rat cortex led to amphetamine hypersensitivity. Co-transfected GFP could be detected in neurons by post mortem fluorescence microscopy in cryosections indicating gene expression present at &ge;6 months after birth.
 We conclude that postnatal bioluminescence imaging allows evaluating the success of transient transfections with IUE in rats. Investigations on the influence of topical gene manipulations during neurodevelopment on the adult brain and its connectivity are greatly facilitated. For many scientific questions, this technique can supplement or even replace the use of transgenic rats and provide a novel technology for behavioral neuroscience.

Generation of Topically Transgenic Rats by In utero Electroporation and In vivo Bioluminescence Screening

Genes can be manipulated during development of the cortex or the hippocampus of the rat via in utero electroporation (IUE) at E16, to enable fast and targeted modifications in neuronal connectivity for later studies of behavior or neuropathology in adult animals. Postnatal in vivo imaging for control of IUE success is performed by bioluminescence of activating co-transfected luciferase.

 In utero electroporation (IUE) is a technique which allows genetic modification of cells in the brain for investigating neuronal development. So far, the ...

Genetic Manipulation of the Mouse Developing Hypothalamus through In utero Electroporation

Genetic modification of specific regions of the developing mammalian brain is a very powerful experimental approach. However, generating novel mouse mutants is often frustratingly slow. It has been shown that access to the mouse brain developing in utero with reasonable post-operatory survival is possible. Still, results with this procedure have been reported almost exclusively for the most superficial and easily accessible part of the developing brain, i.e. the cortex. The thalamus, a narrower and more medial region, has proven more difficult to target. Transfection into deeper nuclei, especially those of the hypothalamus, is perhaps the most challenging and therefore very few results have been reported. Here we demonstrate a procedure to target the entire hypothalamic neuroepithelium or part of it (hypothalamic regions) for transfection through electroporation. The keys to our approach are longer narcosis times, injection in the third ventricle, and appropriate kind and positioning of the electrodes. Additionally, we show results of targeting and subsequent histological analysis of the most recessed hypothalamic nucleus, the mammillary body.

Genetic Manipulation of the Mouse Developing Hypothalamus through In utero Electroporation

Despite the functional and medical importance of the hypothalamus, in utero genetic manipulation of its development has rarely been attempted. We show a detailed procedure for in utero electroporation into the mouse hypothalamus and show representative results of total and partial (regional) hypothalamic transfection.

Genetic  modification of specific regions of the developing mammalian brain is a very  powerful experimental approach. However, generating novel mouse ...

Cortex-, Hippocampus-, Thalamus-, Hypothalamus-, Lateral Septal Nucleus- and Striatum-specific In Utero Electroporation in the C57BL/6 Mouse

In utero electroporation is a widely used technique for fast and efficient spatiotemporal manipulation of various genes in the rodent central nervous system. Overexpression of desired genes is just as possible as shRNA mediated loss-of-function studies. Therefore it offers a wide range of applications. The feasibility to target particular cells in a distinct area further increases the range of potential applications of this very useful method. For efficiently targeting specific regions knowledge about the subtleties, such as the embryonic stage, the voltage to apply and most importantly the position of the electrodes, is indispensable.
Here, we provide a detailed protocol that allows for specific and efficient in utero electroporation of several regions of the C57BL/6 mouse central nervous system. In particular it is shown how to transfect regions the develop into the retrosplenial cortex, the motor cortex, the somatosensory cortex, the piriform cortex, the cornu ammonis 1-3, the dentate gyrus, the striatum, the lateral septal nucleus, the thalamus and the hypothalamus. For this information about the appropriate embryonic stage, the appropriate voltage for the corresponding embryonic stage is provided. Most importantly an angle-map, which indicates the appropriate position of the positive pole, is depicted. This standardized protocol helps to facilitate efficient in utero electroporation, which might also lead to a reduced number of animals.

Cortex-, Hippocampus-, Thalamus-, Hypothalamus-, Lateral Septal Nucleus- and Striatum-specific In Utero Electroporation in the C57BL/6 Mouse

This protocol describes in detail how to specifically transfect different regions in the C57BL/6 central nervous system via in utero electroporation. Included in this protocol are detailed instructions for transfections of regions that develop into the cortex, hippocampus, thalamus, hypothalamus, lateral septal nucleus and striatum.

In utero electroporation is a widely used technique for fast and efficient spatiotemporal manipulation of various genes in the rodent central nervous ...

Time-lapse Confocal Imaging of Migrating Neurons in Organotypic Slice Culture of Embryonic Mouse Brain Using In Utero Electroporation

In utero electroporation is a rapid and powerful approach to study the process of radial migration in the cerebral cortex of developing mouse embryos. It has helped to describe the different steps of radial migration and characterize the molecular mechanisms controlling this process. To directly and dynamically analyze migrating neurons they have to be traced over time. This protocol describes a workflow that combines in utero electroporation with organotypic slice culture and time-lapse confocal imaging, which allows for a direct examination and dynamic analysis of radially migrating cortical neurons. Furthermore, detailed characterization of migrating neurons, such as migration speed, speed profiles, as well as radial orientation changes, is possible. The method can easily be adapted to perform functional analyses of genes of interest in radially migrating cortical neurons by loss and gain of function as well as rescue experiments. Time-lapse imaging of migrating neurons is a state-of-the-art technique that once established is a potent tool to study the development of the cerebral cortex in mouse models of neuronal migration disorders.

Time-lapse Confocal Imaging of Migrating Neurons in Organotypic Slice Culture of Embryonic Mouse Brain Using In Utero Electroporation

This protocol provides instructions for direct observation of radially migrating cortical neurons. In utero electroporation, organotypic slice culture, and time-lapse confocal imaging are combined to directly and dynamically study the effects of overexpression or downregulation of genes of interest in migrating neurons and to analyze their differentiation during development.

In utero electroporation is a rapid and powerful approach to study the process of radial migration in the cerebral cortex of developing mouse embryos. It ...