Technical supported by Melanie Pfeifer and Nikolai Schmarowski (Institute for Microscopic Anatomy and Neurobiology, University Medical Center Mainz).

Ethics Statement: The handling of the mice and the experimental procedures were conducted in accordance with European, national and institutional guidelines for animal care.
1. In Utero Electroporation
Note: In utero electroporation was performed as previously published12,14. Therefore, the method is only described briefly in the following (Figure 1).
<ol>
	<li>Preparations
	<ol>
		<li>Prepare Fast Green colored endotoxin-free advanced transfection-grade plasmid solution (containing 1,5 pCAGGS) as previously described12.</li>
		<li>Pull and grind (35&#176;angle) borosilicate glass capillaries (0.8-0.9 diameter) for injections.</li>
		<li>Sterilize instruments.</li>
	</ol>
	</li>
	<li>Surgery
	<ol>
		<li>Administer analgesics (carprofen, 4 mg/kg bodyweight, s.c., 24 hr depot) at least 30 min before starting the surgery.</li>
		<li>Keep the length of the anesthesia to a maximum of 35-45 min (Stage III - stage of surgical anesthesia according to Guedel15 - maximal 25-30 min).</li>
		<li>Anesthetize timed pregnant mice with isoflurane (induction in a chamber: 2.8%, surgery via mask: 2.5%). Confirm anesthesia by unresponsiveness to toe-pinch.</li>
		<li>Apply eye ointment to prevent eye-dryness during anesthesia.</li>
		<li>Sterilize the surgical area with 7.5% Providone-Iodine solution and cover the mouse with sterile gauze (moist with 0.9% benzyl alcohol saline solution) with only the surgical area exposed.</li>
		<li>Cut open the abdominal cavity with a scalpel (skin incision: 1.5-2 cm, muscle incision: 1-1.5 cm).</li>
		<li>Preserve the opened abdominal cavity from drying out by moistening with warmed 0.9% benzyl alcohol saline solution or other sterile isotonic solution as directed by veterinary staff or committee.&#160;</li>
		<li>Carefully extract uterine horns (using ring forceps, do not touch the uterus with fingers).</li>
	</ol>
	</li>
	<li>Injection of DNA and electroporation. Note: The exact details for targeting specific regions are indicated in section 2.
	<ol>
		<li>Slowly inject the colored DNA solution into the ventricle as indicated in Figure 1 and section 2 via the prepared borosilicate capillaries.</li>
		<li>Apply the appropriate voltage for the corresponding embryonic stage (e.g., 36-38 V for E14) via specialized forceps-type platinum electrodes (interval cycle length 50 msec, interval pause 950 msec).&#160;Pulse the electroporation paddles during the application of the voltage to minimize damage of the uterine wall.</li>
	</ol>
	</li>
	<li>Post electroporation/ post-operative care
	<ol>
		<li>Carefully replace the uterine horns in the abdominal cavity.</li>
		<li>Suture the muscle and the skin incision separately.</li>
		<li>Let the mouse rest on a thermal support device&#160;for recovery.</li>
		<li>Supervise the mouse during recovery (behavior, feed and water consumption), 4 hr, 24 hr and 48 hr after surgery. If necessary, apply additional analgesics (carprofen, 4 mg/kg bodyweight, 24 hr depot) for further 2 days.</li>
	</ol>
	</li>
</ol>
2. Transfection of Specific Cerebral Areas
Note: The position of the positive pole is shown as the angle between the vertical centerline through the ventricle filled with the DNA solution (the right or third ventricle) and the position of the positive pole. When filling the left ventricle the positions are mirror-inverted. In Figure 4 the positions of the ear primordial are shown, which provide important reference points.
<ol>
	<li>Transfection of cortical areas (Figure 2A, Table 1).
	<ol>
		<li>Perform surgery as described in section 1.2. For the in utero electroporation of cortical areas use E14 embryos.</li>
		<li>Inject 1.5-2 &#181;l DNA-solution containing 4 &#181;g DNA in the right lateral ventricle via the prepared borosilicate capillaries.
		<ol>
			<li>Carefully position the embryo by using ring forceps so that there are no visible vessels above the puncture site.</li>
			<li>Slowly inject the DNA-solution approximately 0.75 mm coronal from the lambdoidal suture and 0.5 mm lateral from the sagittal suture (Figure 3). Ensure that the insertion depth is 1.2 mm (E14, measured from the uterine wall). Check for a blue-green colouring with a sharp demarcation.</li>
		</ol>
		</li>
		<li>Apply voltage via the specialized forceps-type platinum electrodes (interval cycle length 50 msec, interval pause 950 msec).
		<ol>
			<li>Use a 3 or 5 mm electrode paddle.</li>
			<li>Use a voltage ranging from 36-38 V.</li>
			<li>Place the center of the electrodes just anterior of the ear primordia.</li>
			<li>To transfect the retrosplenial cortex use angles from 330-0&#176;, to transfect the motor cortex 0-40&#176;, to transfect the somatosensory cortex 40-95&#176;, to transfect the piriform cortex 95-110&#176; (Figure 2A).</li>
		</ol>
		</li>
		<li>Perform post electroporation/ post-operative care as described in section 1.4. Sacrifice the mice and analyze the embryos 4 days after electroporation (E18) as described in section 3.</li>
	</ol>
	</li>
	<li>Transfection of the hippocampus (Figure 2B, Table 1).
	<ol>
		<li>Perform surgery as described in section 1.2. For the in utero electroporation of hippocampal formation use E15 embryos.</li>
		<li>Inject 2 &#181;l DNA-solution containing 4 &#181;g DNA in the right lateral ventricle via the prepared borosilicate capillaries.</li>
		<li>Apply voltage via the specialized forceps-type platinum electrodes (interval cycle length 50 msec, interval pause 950 msec).
		<ol>
			<li>Use a 3 or 5 mm electrode paddle.</li>
			<li>Use a voltage ranging from 38-40.</li>
			<li>Place the center of the negative pole just anterior of the ear primordium and the center of the positive pole at the middle of the ear primordium.</li>
			<li>To transfect the dentate gyrus use angles from 190-210&#176;, to transfect the cornu ammonis (CA)3 210-230&#176;, to transfect the CA2 230-250&#176;, to transfect the CA1 250-275&#176; (Figure 2B).</li>
		</ol>
		</li>
		<li>Perform post electroporation/ post-operative care as described in section 1.4. Perform analysis after complete hippocampal formation (after birth, p21) as described in section 3.</li>
	</ol>
	</li>
	<li>Transfection of the lateral septal nucleus and striatum (Figure 2C, Table 1) 
	Note: The angles overlap with those for transfecting the hippocampus. To effectively transfect the lateral septal nucleus and the striatum without unwanted hippocampus transfection earlier embryonic stages (E12) have to be used.
	<ol>
		<li>Perform surgery as described in section 1.2. For the in utero electroporation of the lateral septal nucleus and striatum use E12 embryos.</li>
		<li>Inject 1 &#181;l DNA-solution containing 4 &#181;g DNA in the right lateral ventricle via the prepared borosilicate capillaries.</li>
		<li>Apply voltage via the specialized forceps-type platinum electrodes (interval cycle length 50 msec, interval pause 950 msec).
		<ol>
			<li>Use a 0.5 mm electrode.</li>
			<li>Use 33 V.</li>
			<li>Place the center of the electrodes at the level of the ear primordia.</li>
			<li>To transfect the lateral septal nucleus use angles from 100-170&#176;, to transfect the striatum 170-240&#176; (Figure 2C).</li>
		</ol>
		</li>
		<li>Perform post electroporation/ post-operative care as described in section 1.4. Sacrifice the mice and analyze the embryos 6 days after electroporation (E18) as described in section 3.</li>
	</ol>
	</li>
	<li>Transfection of the thalamus and hypothalamus (Figure 2D, Table 1)
	<ol>
		<li>Perform surgery as described in section 1.2. For the in utero electroporation of the thalamus and hypothalamus use E12-E13 embryos.</li>
		<li>Inject 1-1.5 &#181;l DNA-solution containing 4 &#181;g DNA in the lateral ventricle (left or right)via the prepared borosilicate capillaries. Wait for 2-3 min, until the solution is diffused into the third ventricle. Alternatively directly inject into the third ventricle. 
		Note: This enhances specificity but might cause a decreased survival rate (high risk of damage).</li>
		<li>Apply voltage via the specialized forceps-type platinum electrodes (interval cycle length 50 msec, interval pause 950 msec).
		<ol>
			<li>Use a 0.5 or 3 mm electrode.</li>
			<li>Use a voltage ranging from 33-35 V.</li>
			<li>Place the center of the electrodes just posterior the ear primordia.</li>
			<li>To transfect the thalamus use angles from 25-40&#176;, to transfect the hypothalamus 90-180&#176; (Figure 2D).</li>
		</ol>
		</li>
		<li>Perform post electroporation/ post-operative care as described in section 1.4. Sacrifice the mice and analyze the embryos 6 days after electroporation (E18) as described in section 3.</li>
	</ol>
	</li>
</ol>
3. Perfusion Fixation
<ol>
	<li>Preparations
	<ol>
		<li>Warm 4% paraformaldehyde (PFA) to 37 &#176;C.</li>
		<li>Fill a 50 ml syringe with PBS (4 &#176;C) and a second syringe with warmed PFA. Avoid bubbles.</li>
		<li>Connect the syringes to a three-way stopcock. Connect the third end to a winged infusion set (butterfly).</li>
		<li>Flush the winged infusion set with PBS.</li>
	</ol>
	</li>
	<li>Perfusion
	<ol>
		<li>Deeply anesthetize the mice (pregnant or postnatal transfected) with subcutaneous application of ketamine hydrochloride (60 mg/ kg) and xylazine (7.5 mg/ kg).</li>
		<li>Confirm the surgical tolerance stage by unresponsiveness to toe-pinch.</li>
		<li>Open the abdominal cavity just beneath the rib cage.</li>
		<li>Carefully cut the diaphragm.</li>
		<li>Carefully open the rib cage via a cut on each site up to the collarbone.</li>
		<li>Insert the tip of the butterfly into the left heart chamber (starting from the apex of the heart).</li>
		<li>Cut the left atrial appendage.</li>
		<li>Slowly perfuse the mouse with PBS (approximately 10 ml).</li>
		<li>Switch the three-way stopcock.</li>
		<li>Perfuse the mouse with 5-10 ml 4% PFA.</li>
		<li>Decapitate the mouse using scissors and dissect the brain beginning at the foramen magnum. Perform the dissection as previously published 16.</li>
		<li>Postfixate the brain for 2 days in 4% PFA. Keep the brains at 4 &#176;C in the dark.</li>
	</ol>
	</li>
</ol>
4. Immunohistochemistry
<ol>
	<li>Generate 70 &#181;m sections (e.g., with a vibratome).</li>
	<li>Optional: Enhance fluorescence with antibody staining.
	<ol>
		<li>Block the sections for 1 hr at RT (0.1-0.2% Triton X-100, 5% normal goat serum)</li>
		<li>Incubate O/N with the appropriate antibody (anti-GFP, 1:1,000)</li>
		<li>Wash 3-5 times with 0.1 M phosphate buffer.</li>
		<li>Incubate 3-5 hr with the appropriate fluorescence-conjugated secondary antibody (Alexa Fluor 488 conjugated anti-rabbit-IgG, 1:1,000).</li>
		<li>Optional: Counterstain with 4-6-diaminodino-2-phenylindole (DAPI, 0.2 g/ ml in 0.1 M phosphate buffer) for 1 min.</li>
		<li>Analyze fluorescence with an appropriate fluorescence microscope.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

This protocol describes in detail how to transfect 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 of C75BL/6 mice. With all the provided information this is the first protocol, which supplies all necessary information to easily recreate transfections of these cerebral regions in the C57BL/6 mouse. Previous publications are mostly focused only on a few specific regions and therefore the detailed information needed for specific transfections is only scarcely standardized. 
The position and the size of the electrode as well as the applied voltage for the corresponding embryonic stage, which are the critical steps for effective and specific transfections, are precisely described. The provided angle-map helps to orientate the electrodes for specific electroporation. The locations of the electrodes are additionally shown on an embryo in the uterus, an embryo in the amniotic sac and also on a pure, dissected embryo. All of this is intended to help in identifying the correct positions of the electrodes. 
Usage of the appropriate voltage is a central aspect in the provided protocol. High voltages decrease the survival rate, whereas low voltages reduce the transfection efficiency 2,3,12. Voltage recommendations given in this protocol are specific for C57BL/6 mice and slightly differ from these for CD12,3,12. CD1 mice tolerate higher voltages than C57BL/6 mice and therefore higher voltages might be used for transfecting CD1 mice12. No data exist for other mouse strains, but the standards might need some modifications. 
A further central point is the size of the electrode. The usage of a smaller electrode, rather than a bigger one, is always recommended for experiments where specificity is important. Smaller electrodes enhance specificity4,12. If the specificity of the transfection is not the main point, especially for inexperienced experimenters, bigger electrodes enhance the chance of hitting the desired region. Thereby one has to keep in mind that electrodes covering too much of the embryo, might affect the heart rhythm and lead to reduced survival. For example a 10 mm electrode covers the whole E12 embryo and therefore is not recommended for transfecting E12 embryos, even if specificity is not the primary goal. 
The stages used in this protocol were chosen exemplary. Considering the fact that progenitors that are transfected on a certain time point give rise to a particular type of neuron the embryonic stages for transfection can be adapted to the specific aim of the study. For instance during cortical development, neurons are born at different time points, forming the six cortical layers in a sequential manner. Hence, depending of the time point of transfection the transfected progenitors give rise to neurons of a specific layer2,17.
For a successful transfection the following points also should be observed. First, the careful preparation and injection of the glass capillaries play a crucial role for the survival of the embryos and therefore for effective transfection. Second, the selection of an appropriate DNA concentration can also be very important and might have to be specifically adapted for different vectors18. Third, application of high voltages affects neighboring embryos, and therefore transfection of neighboring embryos might reduce the survival of these embryos. Further it has also been recommended to avoid the embryos closest to the vaginal duct, because the damage of these embryos might lead to abortion18.
Besides great advantages the technique of in utero electroporation has its drawbacks, which should be taken into consideration while designing experiment. First the regions, which can be efficiently transfected, are manly restricted to areas surrounding the ventricles. This is due to the fact that the plasmid-solution has to be injected into a ventricle. Further, even with all the details provided in this protocol it is not possible to transfect all cells out of a specific region. Even the number of transfected cells is hardly controllable. The analysis of the gene function is not restricted to embryonic stages. Adult mice can also be analyzed because the transfection of postmitotic neurons lasts at least up to 4 months13, but is not passed to the next generation. 
Further specifications, such as specifically electroporating thalamic and hypothalamic nuclei or temporally addressing cortical layers can additionally broaden the scope. The combination of genetically engineered mice, or inducible systems in with the in utero electroporation also additionally enhances possible applications. 
With all the given facts, this protocol facilitates specific transfections and therefore reduces the number of animal used. Standardization of the protocol additionally enhances the comparability of the obtained results.

Since the first description in 2001 by three independent groups 1-3 in utero electroporation has become a widely used standard tool for analyzing gene expression in the rodent central nervous system. Compared to the generation of knockout mice, which is, despite continuously improving techniques, still time and money consuming, the in utero electroporation appeals due to its simplicity. So, in utero electroporation enables fast and efficient gain- and loss-of-function studies 4.
To transfect the cerebral regions, the solution containing the negatively charged plasmid is injected into a ventricle. During the electric pulse, the negatively charged DNA migrates towards the positive pole and therefore the transfected region can be selected simply by altering the position of the positive pole. It has frequently been shown that numerous regions of the central nervous system can be targeted 3,5-8. For instance, recent studies show specific transfections of the hippocampus, the piriform cortex or the striatum 9-11. However, the information about the appropriate positions are often only scarcely standardized and are not always easy to transfer to different mouse strains.
Transfection of certain embryonic stages is far from trivial. Many influencing factors must be taken into consideration when choosing the set-up for specific in utero electroporation. First, to optimally transfect the respective embryonic stages, knowledge about the appropriate voltages is needed. High voltages decrease the survival rate, whereas low voltages reduce the transfection efficiency 2,3,12. Also the size of the electrode paddle plays a crucial role, because the use of electrode paddles that are too large results in reduced specificity or can cause death due to affection of the heart rhythm 4,12,13. The applied voltage and the size and the position of the electrode paddle are the most important features to consider, but there are also further factors influencing the outcome of the electroporation, like the applied amount of DNA-solution.
We have developed a detailed protocol which enables fast and efficient transfection of various cerebral regions of the C57BL/6 mouse 12. In this protocol detailed information about the voltages to be used and the size of the electrode paddle for enhanced specificity is provided. Further, information about the ventricle to be filled along with recommendations for the amount of plasmid solution and the position of the electrode is supplied. The indication of the detailed position information in a map and the further visualization of these positions enables straightforward specific and efficient in utero electroporation of 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.

<table><tbody><tr><td>EndoFree Plasmid Maxi Kit</td><td>QIAGEN</td><td>12362</td><td></td></tr><tr><td>Fast Green</td><td>Roth</td><td>0301.1</td><td></td></tr><tr><td>pCAGGS</td><td>Addgene</td><td></td><td></td></tr><tr><td>borosilicate glass capillaries (0.8-0.9 mm diameter)</td><td>Wold Precision Instrument Inc.</td><td>1B100F-4</td><td></td></tr><tr><td>Isoflurane (Forene)</td><td>Abbott</td><td>PZN 4831850</td><td></td></tr><tr><td>Carprofen (Rimadyl)</td><td>Pfizer GmbH</td><td>approval number: 400684.00.00</td><td></td></tr><tr><td>eye ointment (Bepanthen Augen und Nasensalbe)</td><td>Bayer&amp;nbsp;</td><td>PZN 01578681</td><td></td></tr><tr><td>0.9% benzyl alcohol 0.9% saline solution</td><td>Pharmacy&lt;br/&gt; of the University Medical Center Mainz</td><td></td><td></td></tr><tr><td>gauze (ES-Kompressen)</td><td>Hartmann</td><td>407835</td><td></td></tr><tr><td>sterile 5-0 Perma-Hand Silk Suture</td><td>Ethicon Johnson &amp;amp; Johnson</td><td>K890H</td><td></td></tr><tr><td>ring forceps 1/ 1.5 mm</td><td>Fine Science Tools</td><td>11101-09</td><td></td></tr><tr><td>ring forceps 4.8/ 6 mm</td><td>Fine Science Tools</td><td>11106-09</td><td></td></tr><tr><td>ring forceps 2.2/ 3 mm</td><td>Fine Science Tools</td><td>11103-09</td><td></td></tr><tr><td>Adson Forceps-Serrated Straight 12 cm</td><td>Fine Science Tools</td><td>1106-12</td><td></td></tr><tr><td>IrisScissors-Delicate Straight-Sharp/Blunt 10 cm</td><td>Fine Science Tools</td><td>14028-10</td><td></td></tr><tr><td>Mayo-Stille Scissors-Straight 15 cm</td><td>Fine Science Tools</td><td>14012-15</td><td></td></tr><tr><td>Dumont #5 Forceps-Inox</td><td>Fine Science Tools</td><td>11251-20</td><td></td></tr><tr><td>Castroviejo NeedleHolder-with Lock-Tungsten Carbide 14 cm</td><td>Fine Science Tools</td><td>12565-14</td><td></td></tr><tr><td>Elektroporator CUY21 SC&amp;nbsp;</td><td>Nepa Gene Co.</td><td></td><td></td></tr><tr><td>FST 250 Hot Bead Sterilizer</td><td>Fine Science Tools</td><td>18000-45</td><td></td></tr><tr><td>Microgrinder EG-44</td><td>Narishige</td><td></td><td></td></tr><tr><td>P-97 Micropette Puller</td><td>Sutter Instrument Company</td><td>P-97</td><td></td></tr><tr><td>Platinum electrodes 650P 0.5 mm</td><td>Nepagene</td><td>CUY650P0.5</td><td></td></tr><tr><td>Platinum electrodes 650P 3 mm</td><td>Nepagene</td><td>CUY650P3</td><td></td></tr><tr><td>Platinum electrodes 650P 5 mm</td><td>Nepagene</td><td>CUY650P5</td><td></td></tr><tr><td>Platinum electrodes 650P 10 mm</td><td>Nepagene</td><td>CUY650P10</td><td></td></tr><tr><td>Anesthesia system</td><td>Rothacher-Medical GmbH</td><td>CV-30511-3 Vapor 19.3</td><td></td></tr><tr><td>Heating plate</td><td>Rothacher-Medical GmbH</td><td>HP-1M</td><td></td></tr><tr><td>Temperature Controller 220V AC</td><td>Rothacher-Medical GmbH</td><td>TCAT-2LV</td><td></td></tr></tbody></table>

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.

Figure 2, shows examples for the specific in utero electroporation of the regions developing 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. The results of the transfections are shown next to the recommended angle (Figure 2). For better visualization of the angles in vivo the position of the electrode (0.5 mm) are also shown on an embryo (Figure 5, embryo in utero, embryo in amniotic sac, dissected embryo). In order to provide an overview Table 1 summarized the relevant facts for specific transfection.
Further, it was demonstrated that the size of the electrode plays a crucial role for the specificity (Figure 6). Larger size of the electrode paddles leads to larger transfected areas, as exemplary shown in Figure 6. Further, electrodes that are too large cover too much of the embryo, thereby enhancing the risk of affecting the embryos heart rhythm (Figure 7). For example a 10 mm electrode paddle covers the whole E12 embryo (Figure 7).
<img alt="Tissue dissection and microsurgery setup in lab; steps include sample extraction and preparation." src="/files/ftp_upload/53303/53303fig1.jpg" data-altupdatedat="1747911167000" data-alt="Figure 1"> 
Figure 1. In utero electroporation. Basic steps of the performance of the in utero electroporation are shown. (A) Shows the whole setup of the surgery, with the mouse placed on a hotplate already anesthetized with isoflurane. (B) The disinfection of the surgical area is a crucial step before opening the abdominal cavity (C) of the mouse. (D) The DNA-containing solution is colored with Fast Green, which enables the visualization of successful injection (E, F). Successful injection into a lateral ventricle results into crescent-shaped spot. (G) After the injection the appropriate voltage is applied via forceps type platinum electrodes. (H) After carefully replacing the uterus into the abdominal cavity the surgical wound is sutured. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53303/53303fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Brain region fluorescence microscopy; cortical, hippocampal, nuclei diagrams; neuronal polarity study." src="/files/ftp_upload/53303/53303fig2.jpg" data-altupdatedat="1747911167000" data-alt="Figure 2"> 
Figure 2. Angle-map for electroporation of specific areas in the murine cortex, hippocampus, lateral septal nucleus, striatum, thalamus and hypothalamus. The appropriate positions for the positive and negative pole, are indicated in the schematic drawing. For (A-C) the positions are indicated for injecting the DNA-solution into the right ventricle. For injections into the left ventricle, the angles are mirror-inverted. The specific transfections were histologically verified. (A) Shows the positions of the positive and negative pole for transfecting cortical areas (the retrosplenial cortex (RSC), the motor cortex (MC), the somatosensory cortex (SSC) and the piriform cortex (PC). (B) Shows the positions of the positive and negative pole for transfecting the hippocampal formations (the cornu ammonis 1-3 (CA1, CA2, CA3) and the dentate gyrus (DG). (C) Shows the positions of the positive and negative pole for transfecting the striatum (STR) and the lateral septal nucleus (LS). (D) Shows the appropriate positions of the electrodes for transfecting the thalamus (TH) and the hypothalamus (HY). Adapted from Baumgart J. &amp; Grebe N., 2015 12. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53303/53303fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Schematic of a fetal skull diagram highlighting lambdoidal and sagittal sutures, with measurements." src="/files/ftp_upload/53303/53303fig3.jpg" data-altupdatedat="1747911167000" data-alt="Figure 3"> 
Figure 3. Puncture site. The optimal position for the injection of the DNA solution is approximately 0.75 mm coronal from the lambdoidal suture and 0.5 mm lateral from the sagittal suture. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53303/53303fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Dissection analysis, anatomical tissue structure, veterinary or biological study, educational reference." src="/files/ftp_upload/53303/53303fig4.jpg" data-altupdatedat="1747911167000" data-alt="Figure 4"> 
Figure 4. Position of the ear primordium. The position of the ear primordium is clearly defined (arrow). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53303/53303fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt='Alt text: "Cortex dissection stages diagram; in utero, amniotic sac, dissected; retrosplenial to piriform."' src="/files/ftp_upload/53303/53303fig5A.jpg" data-altupdatedat="1747911167000" data-alt="Figure 5A">
<img alt="Hippocampus dissection images: in utero, amniotic sac, dissected; CA1, CA2, CA3, DG stages." src="/files/ftp_upload/53303/53303fig5B.jpg" data-altupdatedat="1747911167000" data-alt="Figure 5B">
<img alt="Lateral Septal Nucleus and Striatum dissection process; embryo stages: in utero, amniotic sac, dissected." src="/files/ftp_upload/53303/53303fig5C.jpg" data-altupdatedat="1747911167000" data-alt="Figure 5C">
<img alt="Thalamus and hypothalamus developmental stages; dissection; embryo analysis; biology research." src="/files/ftp_upload/53303/53303fig5D.jpg" data-altupdatedat="1747911167000" data-alt="Figure 5D"> 
Figure 5. Visualization of the angles on an embryo. For better visualization the appropriate positions for the positive (indicated with a blue plus sign) and the negative pole for specific transfections of the cortical areas (retrosplenial cortex, motor cortex, somatosensory cortex, piriform cortex), the hippocampal areas (cornu ammonis (CA) 1-3, dentate gyrus (DG)), the lateral septal nucleus, the striatum, the thalamus and hypothalamus are shown on an embryo in utero, an embryo in the amniotic sac and on a dissected embryo (all E15,5). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53303/53303fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Embryo brain section diagrams, electrode paddle size effect on fluorescence, microscopy results." src="/files/ftp_upload/53303/53303fig6.jpg" data-altupdatedat="1747911167000" data-alt="Figure 6"> 
Figure 6. Specificity of transfection depending on the electrode size. Increased size of the electrode paddle reduces the specificity of the transfection. This is especially obvious in younger embryonic stages (E12, top), but also visible in late embryonic stages (E17, bottom). Adapted from Baumgart J. &amp; Grebe N., 2015 12. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53303/53303fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Embryo development stages E12 at 0.5mm, 3mm, 5mm, 10mm; size comparison with tools, microscope image." src="/files/ftp_upload/53303/53303fig7.jpg" data-altupdatedat="1747911167000" data-alt="Figure 7"> 
Figure 7. Size of the electrode paddle compared to the size of an E12 embryo. Electrodes that are too large cover too much of the embryo and therefore increase the risk of affection of the heart rhythm. For example, a 10 mm electrode (on the right) covers the whole E12 embryo and therefore is not recommended, even if specificity is not the primary goal. Adapted from Baumgart J. &amp; Grebe N., 2015 12. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53303/53303fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table fo:keep-together.within-page="1">
	<tbody>
		<tr>
			<td>Targeted region</td>
			<td>Angle</td>
			<td colspan="2">Position of the electrode</td>
			<td>Age of embryo</td>
			<td>DNA amount/ concentration</td>
			<td>Voltage</td>
			<td>Size of electrode</td>
		</tr>
		<tr>
			<td>Retrosplenial Cortex</td>
			<td>330°- 0°</td>
			<td colspan="2">Center of the electrodes just anterior of the ear primordia</td>
			<td>E14 (E11-E17)</td>
			<td>1.5- 2 µl/ 
			2.7- 2 µg/µl</td>
			<td>36- 38</td>
			<td>3- 5 mm</td>
		</tr>
		<tr>
			<td>Motor Cortex</td>
			<td>0°- 40°</td>
			<td colspan="2">Center of the electrodes just anterior of the ear primordia</td>
			<td>E14 (E11-E17)</td>
			<td>1.5- 2 µl/ 
			2.7- 2 µg/µl</td>
			<td>36- 38</td>
			<td>3- 5 mm</td>
		</tr>
		<tr>
			<td>Somatosensory Cortex</td>
			<td>40°- 95°</td>
			<td colspan="2">Center of the electrodes just anterior of the ear primordia</td>
			<td>E14 (E11-E17)</td>
			<td>1.5- 2 µl/ 
			2.7- 2 µg/µl</td>
			<td>36- 38</td>
			<td>3- 5 mm</td>
		</tr>
		<tr>
			<td>Piriform Cortex</td>
			<td>95°- 110°</td>
			<td colspan="2">Center of the electrodes just anterior of the ear primordia</td>
			<td>E14 (E11-E17)</td>
			<td>1.5- 2 µl/ 
			2.7- 2 µg/µl</td>
			<td>36-3 8</td>
			<td>3- 5 mm</td>
		</tr>
		<tr>
			<td>Cornu Ammonis 
			(CA)1</td>
			<td>250°- 275°</td>
			<td colspan="2">Center of the positive pole at the middle of the ear primordium</td>
			<td>(E14-) E15</td>
			<td>2 µl/ 
			2 µg/µl</td>
			<td>38- 40</td>
			<td>3- 5 mm</td>
		</tr>
		<tr>
			<td>CA2</td>
			<td>230°- 250°</td>
			<td colspan="2">Center of the positive pole at the middle of the ear primordium</td>
			<td>(E14-) E15</td>
			<td>2 µl/ 
			2 µg/µl</td>
			<td>38- 40</td>
			<td>3- 5 mm</td>
		</tr>
		<tr>
			<td>CA3</td>
			<td>210°- 230°</td>
			<td colspan="2">Center of the positive pole at the middle of the ear primordium</td>
			<td>(E14-) E15</td>
			<td>2 µl/ 
			2 µg/µl</td>
			<td>38- 40</td>
			<td>3- 5 mm</td>
		</tr>
		<tr>
			<td>Dentate Gyrus</td>
			<td>190°- 210°</td>
			<td colspan="2">Center of the positive pole at the middle of the ear primordium</td>
			<td>(E14-) E15</td>
			<td>2 µl/ 
			2 µg/µl</td>
			<td>38- 40</td>
			<td>3- 5 mm</td>
		</tr>
		<tr>
			<td>Striatum</td>
			<td>170°- 240°</td>
			<td colspan="2">Center of the electrodes at the level of the ear primordia</td>
			<td>E12</td>
			<td>1 µl/ 
			4 µg/µl</td>
			<td>33</td>
			<td>0.5 mm</td>
		</tr>
		<tr>
			<td>Lateral Septal Nucleus</td>
			<td>100°- 170°</td>
			<td colspan="2">Center of the electrodes at the level of the ear primordia</td>
			<td>E12</td>
			<td>1 µl/ 
			4 µg/µl</td>
			<td>33</td>
			<td>0.5 mm</td>
		</tr>
		<tr>
			<td>Thalamus</td>
			<td>25°- 40°</td>
			<td colspan="2">Center of the electodes just posterior the ear primordia</td>
			<td>E12- E13</td>
			<td>1-1.5 µl/ 
			4-2.7 µg/µl</td>
			<td>33- 35</td>
			<td>0.5- 3 mm</td>
		</tr>
		<tr>
			<td>Hypothalamus</td>
			<td>90°- 180°</td>
			<td colspan="2">Center of the electodes just posterior the ear primordia</td>
			<td>E12- E13</td>
			<td>1-1.5 µl/ 
			4-2.7 µg/µl</td>
			<td>33- 35</td>
			<td>0.5- 3 mm</td>
		</tr>
	</tbody>
</table>
Table 1: Summary of results. Included in this table is all relevant information for specific transfection of the described cortical areas. It contains details about the targeted region, the angle, the position of the electrode, the embryonic stage, the applied amount and concentration of the DNA solution, the voltage and the size of the electrode.

Watch this Scientific Journal Video about Cortex-, Hippocampus-, Thalamus-, Hypothalamus-, Lateral Septal Nucleus- and Striatum-specific In Utero Electroporation in the C57BL/6 Mouse at JoVE.com

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.

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 ...

cortex-hippocampus-thalamus-hypothalamus-lateral-septal-nucleus

Nanyang Technological University

Research

JoVE Journal

Neuroscience

28.0K Views.  University Medical Center, JGU Mainz. 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.

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

In Utero Intraventricular Injection and Electroporation of E15 Mouse Embryos

In-utero in-vivo injection and electroporation of the embryonic mouse neocortex provides a powerful tool for the manipulation of individual progenitors lining the walls of the lateral ventricle. This technique is now widely used to study the processes involved in corticogenesis by over-expressing or knocking down genes and observing the effects on cellular proliferation, migration, and differentiation. In comparison to traditional knockout strategies, in-utero electroporation provides a rapid means to manipulate a population of cells during a specific temporal window. In this video protocol we outline the experimental methodology for preparing mice for surgery, exposing the uterine horns through laporatomy, injecting DNA into the lateral ventricles of the developing embryo, electroporating DNA into the progenitors lining the lateral wall, and caring for animals post-surgery. Our laboratory uses this protocol for surgeries on E13-E16 mice, however, it is most commonly performed at E15, as shown in this video. 

In-utero in-vivo injection and electroporation of the embryonic mouse neocortex provides a powerful tool for the manipulation of individual progenitors ...

Biology

Efficient Gene Delivery into Multiple CNS Territories Using In Utero Electroporation

The ability to manipulate gene expression is the cornerstone of modern day experimental embryology, leading to the elucidation of multiple developmental pathways. Several powerful and well established transgenic technologies are available to manipulate gene expression levels in mouse, allowing for the generation of both loss- and gain-of-function models. However, the generation of mouse transgenics is both costly and time consuming. Alternative methods of gene manipulation have therefore been widely sought. In utero electroporation is a method of gene delivery into live mouse embryos1,2 that we have successfully adapted3,4. It is largely based on the success of in ovo electroporation technologies that are commonly used in chick5. Briefly, DNA is injected into the open ventricles of the developing brain and the application of an electrical current causes the formation of transient pores in cell membranes, allowing for the uptake of DNA into the cell. In our hands, embryos can be efficiently electroporated as early as embryonic day (E) 11.5, while the targeting of younger embryos would require an ultrasound-guided microinjection protocol, as previously described6. Conversely, E15.5 is the latest stage we can easily electroporate, due to the onset of parietal and frontal bone differentiation, which hampers microinjection into the brain. In contrast, the retina is accessible through the end of embryogenesis. Embryos can be collected at any time point throughout the embryonic or early postnatal period. Injection of a reporter construct facilitates the identification of transfected cells.
To date, in utero electroporation has been most widely used for the analysis of neocortical development1,2,3,4. More recent studies have targeted the embryonic retina7,8,9 and thalamus10,11,12. Here, we present a modified in utero electroporation protocol that can be easily adapted to target different domains of the embryonic CNS. We provide evidence that by using this technique, we can target the embryonic telencephalon, diencephalon and retina. Representative results are presented, first showing the use of this technique to introduce DNA expression constructs into the lateral ventricles, allowing us to monitor progenitor maturation, differentiation and migration in the embryonic telencephalon. We also show that this technique can be used to target DNA to the diencephalic territories surrounding the 3rd ventricle, allowing the migratory routes of differentiating neurons into diencephalic nuclei to be monitored. Finally, we show that the use of micromanipulators allows us to accurately introduce DNA constructs into small target areas, including the subretinal space, allowing us to analyse the effects of manipulating gene expression on retinal development.

Efficient Gene Delivery into Multiple CNS Territories Using In Utero Electroporation

In utero electroporation allows for rapid gene delivery in a spatially- and temporally-controlled manner in the developing central nervous system (CNS). Here we describe a highly adaptable in utero electroporation protocol that can be used to deliver expression constructs into multiple embryonic CNS domains, including the telencephalon, diencephalon and retina.

The ability to manipulate gene expression is the cornerstone of modern day experimental embryology, leading to the elucidation of multiple developmental ...

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 ...

Expansion of Embryonic and Adult Neural Stem Cells by In Utero Electroporation or Viral Stereotaxic Injection

Somatic stem cells can divide to generate additional stem cells (expansion) or more differentiated cell types (differentiation), which is fundamental for tissue formation during embryonic development and tissue homeostasis during adulthood 1. Currently, great efforts are invested towards controlling the switch of somatic stem cells from expansion to differentiation because this is thought to be fundamental for developing novel strategies for regenerative medicine 1,2. However, a major challenge in the study and use of somatic stem cell is that their expansion has been proven very difficult to control.
Here we describe a system that allows the control of neural stem/progenitor cell (altogether referred to as NSC) expansion in the mouse embryonic cortex or the adult hippocampus by manipulating the expression of the cdk4/cyclinD1 complex, a major regulator of the G1 phase of the cell cycle and somatic stem cell differentiation 3,4. Specifically, two different approaches are described by which the cdk4/cyclinD1 complex is overexpressed in NSC in vivo. By the first approach, overexpression of the cell cycle regulators is obtained by injecting plasmids encoding for cdk4/cyclinD1 in the lumen of the mouse telencephalon followed by in utero electroporation to deliver them to NSC of the lateral cortex, thus, triggering episomal expression of the transgenes 5-8. By the second approach, highly concentrated HIV-derived viruses are stereotaxically injected in the dentate gyrus of the adult mouse hippocampus, thus, triggering constitutive expression of the cell cycle regulators after integration of the viral construct in the genome of infected cells 9. Both approaches, whose basic principles were already described by other video protocols 10-14, were here optimized to i) reduce tissue damage, ii) target wide portions of very specific brain regions, iii) obtain high numbers of manipulated cells within each region, and iv) trigger high expression levels of the transgenes within each cell. Transient overexpression of the transgenes using the two approaches is obtained by different means i.e. by natural dilution of the electroporated plasmids due to cell division or tamoxifen administration in Cre-expressing NSC infected with viruses carrying cdk4/cyclinD1 flanked by loxP sites, respectively 9,15.
These methods provide a very powerful platform to acutely and tissue-specifically manipulate the expression of any gene in the mouse brain. In particular, by manipulating the expression of the cdk4/cyclinD1 complex, our system allows the temporal control of NSC expansion and their switch to differentiation, thus, ultimately increasing the number of neurons generated in the mammalian brain. Our approach may be critically important for basic research and using somatic stem cells for therapy of the mammalian central nervous system while providing a better understanding of i) stem cell contribution to tissue formation during development, ii) tissue homeostasis during adulthood, iii) the role of adult neurogenesis in cognitive functions, and perhaps, iv) better using somatic stem cells in models of neurodegenerative diseases.

Expansion of Embryonic and Adult Neural Stem Cells by In Utero Electroporation or Viral Stereotaxic Injection

Controlling the expansion of somatic stem cells is a major factor hampering their study and use in therapy. Here we describe a system to temporally control neural stem cells expansion during development and adulthood, which can be used to increase the number of neurons generated in the mouse brain.

Somatic stem cells can divide to generate additional stem cells (expansion) or more differentiated cell types (differentiation), which is fundamental for ...

In utero and ex vivo Electroporation for Gene Expression in Mouse Retinal Ganglion Cells

The retina and its sole output neuron, the retinal ganglion cell (RGC), comprise an excellent model in which to examine biological questions such as cell differentiation, axon guidance, retinotopic organization and synapse formation[1]. One drawback is the inability to efficiently and reliably manipulate gene expression in RGCs in vivo, especially in the otherwise accessible murine visual pathways. Transgenic mice can be used to manipulate gene expression, but this approach is often expensive, time consuming, and can produce unwanted side effects. In chick, in ovo electroporation is used to manipulate gene expression in RGCs for examining retina and RGC development. Although similar electroporation techniques have been developed in neonatal mouse pups[2], adult rats[3], and embryonic murine retinae in vitro[4], none of these strategies allow full characterization of RGC development and axon projections in vivo. To this end, we have developed two applications of electroporation, one in utero and the other ex vivo, to specifically target embryonic murine RGCs[5, 6]. 
With in utero retinal electroporation, we can misexpress or downregulate specific genes in RGCs and follow their axon projections through the visual pathways in vivo, allowing examination of guidance decisions at intermediate targets, such as the optic chiasm, or at target regions, such as the lateral geniculate nucleus. Perturbing gene expression in a subset of RGCs in an otherwise wild-type background facilitates an understanding of gene function throughout the retinal pathway. Additionally, we have developed a companion technique for analyzing RGC axon growth in vitro. We electroporate embryonic heads ex vivo, collect and incubate the whole retina, then prepare explants from these retinae several days later. Retinal explants can be used in a variety of in vitro assays in order to examine the response of electroporated RGC axons to guidance cues or other factors. In sum, this set of techniques enhances our ability to misexpress or downregulate genes in RGCs and should greatly aid studies examining RGC development and axon projections.

In utero and ex vivo Electroporation for Gene Expression in Mouse Retinal Ganglion Cells

Here we present two techniques for manipulating gene expression in murine retinal ganglion cells (RGCs) by in utero and ex vivo electroporation. These techniques enable one to examine how alterations in gene expression affect RGC development, axon guidance, and functional properties.

The retina and its sole output neuron, the retinal ganglion cell (RGC), comprise an excellent model in which to examine biological questions such as cell ...

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 ...

Subtype-selective Electroporation of Cortical Interneurons

The study of central nervous system (CNS) maturation relies on genetic targeting of neuronal populations. However, the task of restricting the expression of genes of interest to specific neuronal subtypes has proven remarkably challenging due to the relative scarcity of specific promoter elements. GABAergic interneurons constitute a neuronal population with extensive genetic and morphological diversity. Indeed, more than 11 different subtypes of GABAergic interneurons have been characterized in the mouse cortex1. Here we present an adapted protocol for selective targeting of GABAergic populations. We achieved subtype selective targeting of GABAergic interneurons by using the enhancer element of the homeobox transcription factors Dlx5 and Dlx6, homologues of the Drosophila distal-less (Dll) gene2,3, to drive the expression of specific genes through in utero electroporation.

This procedure shows how to target interneurons in the developing mouse forebrain by means of in utero electroporation. This technique was particularly efficient to achieve selective gene expression in interneuron subtypes destined to the superficial layers of the cortex.

The study of central nervous system (CNS) maturation relies on genetic targeting of neuronal populations. However, the task of restricting the expression ...

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

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

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

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

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

Double In Utero Electroporation to Target Temporally and Spatially Separated Cell Populations

In utero electroporation is an in vivo DNA transfer technique extensively used to study the molecular and cellular mechanisms underlying mammalian corticogenesis. This procedure takes advantage of the brain ventricles to allow the introduction of DNA of interest and uses a pair of electrodes to direct the entrance of the genetic material into the cells lining the ventricle, the neural stem cells. This method allows researchers to label the desired cells and/or manipulate the expression of genes of interest in those cells. It has multiple applications, including assays targeting neuronal migration, lineage tracing, and axonal pathfinding. An important feature of this method is its temporal and regional control, allowing circumvention of potential problems related with embryonic lethality or the lack of specific CRE driver mice. Another relevant aspect of this technique is that it helps to considerably reduce the economic and temporal limitations that involve the generation of new mouse lines, which become particularly important in the study of interactions between cell types that originate in distant areas of the brain at different developmental ages. Here we describe a double electroporation strategy that enables targeting of cell populations that are spatially and temporally separated. With this approach we can label different subtypes of cells in different locations with selected fluorescent proteins to visualize them, and/or we can manipulate genes of interest expressed by these different cells at the appropriate times. This strategy enhances the potential of in utero electroporation and provides a powerful tool to study the behavior of temporally and spatially separated cell populations that migrate to establish close contacts, as well as long-range interactions through axonal projections, reducing temporal and economic costs.

Double in utero electroporation allows targeting cell populations that are spatially and temporally separated. This technique is useful to visualize interactions between those cell populations using fluorescent proteins in normal conditions but also after functional experiments to perturb genes of interest.

In utero electroporation is an in vivo DNA transfer technique extensively used to study the molecular and cellular mechanisms underlying mammalian ...

Murine In Utero Electroporation

In utero electroporation is an important technique for studying the molecular mechanisms that guide the proliferation, differentiation, migration, and maturation of cells during neural development. Electroporation enables the rapid and targeted delivery of material into cells by utilizing electrical pulses to create transient pores in cell membranes. Although electroporation has traditionally been used in in vitro studies, scientific advancements have now broadened its utilization to intact organs, such as those found in mouse embryos developing in utero. This video will introduce the key principles behind in utero electroporation in addition to reviewing the basic surgical techniques required to access developing embryos within a pregnant rodent. Details of the injection and electroporation steps are provided along with important considerations for directing gene delivery to specific brain regions. Finally, neurobiological applications of in utero electroporation are presented, such as investigating how specific genes contribute to neural development and how connections form between developing neurons.

Murine In Utero Electroporation

In utero electroporation is an important technique for studying the molecular mechanisms that guide the proliferation, differentiation, migration, and ...

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

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