Name: double in utero electroporation to target temporally and spatially separated cell populations
Uploaded: 2020-06-14T13:00:00
Description: Watch this Scientific Journal Video about Double In Utero Electroporation to Target Temporally and Spatially Separated Cell Populations at JoVE.com

The authors thank Cristina Andr&#233;s Carbonell and members of the Animal Care facility of the Universidad de Valencia for technical assistance. We also want to thank Isabel Fari&#241;as and Sacramento R. Ferr&#243;n for reagents and sharing their equipment with us. I.M.W is funded by a Garant&#237;a Juvenil contract from the Conselleria de Educaci&#243;n de Valencia (GJIDI/2018/A/221), D.dA.D is funded by the Ministerio de Ciencia, Innovaci&#243;n y Universidades (MICINN)&#160;(FPI-PRE2018-086150). C.Gil-Sanz holds a Ram&#243;n y Cajal Grant (RYC-2015-19058) from the Spanish Ministerio de Ciencia, Innovaci&#243;n y Universidades (MICINN). This Work was funded RYC-2015-19058 and SAF2017-82880-R (MICINN).

The procedure herein described has been approved by the ethical committee in charge of experimentation, the animal welfare of the Universidad de Valencia and the Conselleria de Agricultura, Desarrollo Rural, Emergencia Clim&#225;tica y Transici&#243;n Ecol&#243;gica of the Comunidad Valenciana, and adheres to the guidelines of the International&#160;Council for Laboratory Animal Science (ICLAS) reviewed in the Real Decreto 53/2013 of the Spanish legislation as well as in the Directive 2010/63/EU of the European Parliamen...

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The study of cell-cell interactions in vivo in regions with high cellular density like the cerebral cortex is a complex task. Traditional approaches including the use of antibodies to label neurites are not suitable because of the lack of specific markers for different cell populations. The use of transgenic murine models, where a particular cell type expresses a fluorescent protein, is useful to visualize the neuronal processes, but this depends on the availability of such models. This task is even more complicated when...

The cerebral cortex is a very complex and intricately organized structure. To achieve such a degree of organization, cortical projection neurons go through complex developmental processes that require their temporal generation, migration to their final destination in the cortical plate, and the establishment of short- and long-range connections1,2. For a long time, the classical way to study corticogenesis was based on the use of knockout or knock-in murine models of genes of interest. However, this strategy, and particularly the use of conditional knockout mice, is time consuming and expensive, and sometimes presents additional problems regarding the existence of genetic redundancy or the lack of specific CRE drivers, among other issues. One of the approaches that arose to try to address those problems and that is nowadays extensively used to study cortical development is in utero electroporation3,4. In utero electroporation is a technique used for somatic transgenesis, allowing in vivo targeting of neural stem cells and their progeny. This method can be used to label cells by the expression of fluorescent proteins5,6, for gene manipulation in vivo (i.e., gain or loss of function assays)7,8,9, for isolating electroporated cortices in vitro and culturing cells8,10. Moreover, in utero electroporation permits temporal and regional control of the targeted area. This technique has numerous applications and has been widely used to study neuronal migration, stem cell division, neuronal connectivity, and other subjects8,9,11,12.
The current manuscript describes the use of an in utero electroporation variant, termed double in utero electroporation, to analyze the interactions of cells in the cerebral cortex with different temporal and spatial origins. These studies are extremely complex to complete when employing murine models because they require the combined use of several transgenic lines. Some of the applications of the protocol described in this paper include the study of close interactions among neighboring cells, as well as interactions between distant cells through long-range projections. The method requires performing two independent in utero electroporation surgeries, separated temporally and spatially, on the same embryos to target different cell populations of interest. The advantage of this approach is the possibility of manipulating gene function in one or both types of neurons using wild type animals. In addition, these functional experiments can be combined with the expression of cytoplasmic or membrane-tagged fluorescent proteins to visualize the fine morphology of targeted cells, including dendrites and axons, and analyze possible differences in cellular interactions in comparison with a control (i.e., cells only labeled with the fluorescent protein).
The protocol delineated here is focused on the study of cellular interactions inside the neocortex, but this strategy could also be used to examine interactions with extracortical areas that can be targeted using in utero electroporation, like the subpallium or the thalamus13,14, or cell-cell interactions in other structures, like the cerebellum15. Targeting of different areas is based on the orientation of the electrodes and on the ventricle where the DNA is injected (lateral, third, or fourth). With the strategy described here, we can label a substantial number of cells, which is useful to evaluate general changes in connectivity/innervation in functional experiments. Nevertheless, to study fine changes in connectivity, one can use modified versions of in utero electroporation to get sparser labeling and identify single cells16. In summary, double in utero electroporation is a versatile method that allows targeting temporally and spatially separated cell populations and studying their interactions in detail, either in control conditions or combined with functional experiments, considerably reducing temporal and economic costs.

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			<td>Ampicillin sodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>A9518-25G</td>
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			<td>Baby-mixter hemostat (perfusion)</td>
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			<td>Rb Pharmaceuticals Limited</td>
			<td>921425</td>
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			<td>CAG-BFP plasmid</td>
			<td>Kindly provided by U.M&#252;ller Lab</td>
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			<td>CAG-EGFP plasmid</td>
			<td>Kindly provided by U.M&#252;ller Lab</td>
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			<td>CAG-mCherry plasmid</td>
			<td>Kindly provided by U.M&#252;ller Lab</td>
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			<td>CAG-mtdTomato-2A-nGFP plasmid</td>
			<td>Kindly provided by U.M&#252;ller Lab</td>
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			<td>Confocal microscope</td>
			<td>Olympus</td>
			<td>FV10i</td>
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			<td>Cotton Swabs</td>
			<td>BFHCVDF</td>
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			<td>Cyanoacrylate glue</td>
			<td>B. Braun Surgical</td>
			<td>1050044</td>
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			<td>Dissecting scope</td>
			<td>Zeiss</td>
			<td>stemi 305</td>
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			<td>Dumont Forceps #5 Fine Forceps</td>
			<td>Fine Science Tools (FST)</td>
			<td>11254-20</td>
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			<td>ECM830 Square Wave Electroporator</td>
			<td>BTX</td>
			<td>45-0052</td>
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			<td>Electric Razor</td>
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			<td>76998</td>
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			<td>Endotoxin-free TE buffer</td>
			<td>QIAGEN</td>
			<td>1018499</td>
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			<td>Ethanol wipes</td>
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			<td>Extra Fine Graefe Forceps</td>
			<td>Fine Science Tools (FST)</td>
			<td>11150-10</td>
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			<td>Eye ointment</td>
			<td>Alcon</td>
			<td>682542.6</td>
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			<td>Fast Green dye</td>
			<td>Sigma-Aldrich</td>
			<td>F7252-5G</td>
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			<td>Fine Scissors</td>
			<td>Fine Science Tools (FST)</td>
			<td>14069-09</td>
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			<td>Fluorescence LEDs</td>
			<td>CoolLED</td>
			<td>pE-300-W</td>
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			<td>Genopure Plasmid Maxi Kit</td>
			<td>Roche</td>
			<td>3143422001</td>
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			<td>Halsted-Mosquito Hemostats (suture)</td>
			<td>Fine Science Tools (FST)</td>
			<td>91308-12</td>
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			<td>Heating Pad</td>
			<td>UFESA</td>
			<td>AL5514</td>
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			<td>Inverted epifluorescence microscope</td>
			<td>Nikon</td>
			<td>Eclipse TE2000-S</td>
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			<td>Iodine wipes</td>
			<td>Lorsoul</td>
			<td></td>
			<td></td>
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		<tr>
			<td>Isofluorane vaporizer</td>
			<td>Flow-Meter</td>
			<td>A15B5001</td>
			<td></td>
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		<tr>
			<td>Isoflurane</td>
			<td>Karizoo</td>
			<td>586259</td>
			<td></td>
		</tr>
		<tr>
			<td>Ketamine (Anastemine)</td>
			<td>Fatro Ib&#233;rica SL</td>
			<td>583889-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Kimtech precision wipes</td>
			<td>Kimberly-Clark</td>
			<td>7252</td>
			<td></td>
		</tr>
		<tr>
			<td>LB (Lennox) Agar GEN</td>
			<td>Labkem</td>
			<td>AGLB-00P-500</td>
			<td></td>
		</tr>
		<tr>
			<td>LB (Lennox) broth GEN</td>
			<td>Labkem</td>
			<td>LBBR-00P-500</td>
			<td></td>
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		<tr>
			<td>Low-melting point agarose</td>
			<td>Fisher Scientific</td>
			<td>BP165-25</td>
			<td></td>
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		<tr>
			<td>Medetomidine (Sedator)</td>
			<td>Dechra</td>
			<td>573749.2</td>
			<td></td>
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		<tr>
			<td>Microscope coverslips</td>
			<td>Menel-Gl&#228;ser</td>
			<td>15747592</td>
			<td></td>
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			<td>Microscope Slides</td>
			<td>Labbox</td>
			<td>SLIB-F10-050</td>
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			<td>Mounting medium</td>
			<td>Electron Microscopy Sciences</td>
			<td>17984-25</td>
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			<td>Mutiwell plates (24)</td>
			<td>SPL Life Sciences</td>
			<td>32024</td>
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			<td>Mutiwell plates (48)</td>
			<td>SPL Life Sciences</td>
			<td>32048</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl (for saline solution)</td>
			<td>Fisher Scientific</td>
			<td>10112640</td>
			<td></td>
		</tr>
		<tr>
			<td>Needle 25 G (BD Microlance 3)</td>
			<td>Becton, Dickinson and Company</td>
			<td>300600</td>
			<td></td>
		</tr>
		<tr>
			<td>Orbital incubator S150</td>
			<td>Stuart Scientific</td>
			<td>5133</td>
			<td></td>
		</tr>
		<tr>
			<td>P Selecta Incubator</td>
			<td>J. P. Selecta, s.a.</td>
			<td>0485472</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>PanReac AppliedChem</td>
			<td>A3813</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Sigma -Aldrich</td>
			<td>P4333</td>
			<td></td>
		</tr>
		<tr>
			<td>Peristaltic perfusion pump</td>
			<td>Cole-Parmer</td>
			<td>EW-07522-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Platinum Tweezertrode, 5 mm Diameter</td>
			<td>Btx</td>
			<td>45-0489</td>
			<td></td>
		</tr>
		<tr>
			<td>Reflex Skin Closure System - 7mm Clips, box of 100</td>
			<td>AgnThos</td>
			<td>203-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Reflex Skin Closure System - Clip Applyer, 7mm</td>
			<td>AgnThos</td>
			<td>204-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Ring Forceps</td>
			<td>Fine Science Tools (FST)</td>
			<td>11103-09</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium azide</td>
			<td>PanReac AppliedChem</td>
			<td>122712-1608</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical absorbent pad (steryle)</td>
			<td>HK Surgical</td>
			<td>PD-M</td>
			<td></td>
		</tr>
		<tr>
			<td>Suture (Surgicryl PGA 6-0)</td>
			<td>SMI Suture Materials</td>
			<td>BYD11071512</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe 1ml (BD plastipak)</td>
			<td>Becton, Dickinson and Company</td>
			<td>303172</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue Culture Dish 100 x 20 mm</td>
			<td>Falcon</td>
			<td>353003</td>
			<td></td>
		</tr>
		<tr>
			<td>Vertical Micropipette Puller</td>
			<td>Sutter Instrument Co</td>
			<td>P-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Vertical microscope</td>
			<td>Nikon</td>
			<td>Eclipse Ni</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibratome</td>
			<td>Leica</td>
			<td>VT1200S</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

Interactions between neighboring cells originated in distal places and at different times: Cajal-Retzius cells (CR-cells) and early migrating cortical projection neurons (strategy A)
The interaction of CR-cells and early cortical projection neurons was previously described as necessary to regulate somal translocation via nectin and cadherin adhesion molecules using a double electroporation strategy8. CR-cells originate&#160;from the neuroepithelium at t...

Watch this Scientific Journal Video about Double In Utero Electroporation to Target Temporally and Spatially Separated Cell Populations at JoVE.com

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

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 ...

Double in utero electroporation is a powerful method for studying the important aspects of mammalian corticogenesis such as the interaction between neuron cells, generated at different locations and developmental ages. The main advantage of this technique is the ability to examine unperturbed interactions among these different cell populations in a quick, detailed, and inexpensive manner. One striking implication of our method is that it facilitates a better understanding of how similar our wiring is altered in neuronal disorders like autism and schizophrenia.This study is not restricted to the neocortex but it can also be employed to analyze cell to cell interactions, in exocortico areas such as the sepalium or cerebellum. One of the most challenging steps is injection of DNA into the lateral ventricles of early embryos. The use of a bright light source is essential for successful injections.For each surgery first prepare a 10 microliter solution containing one microliter of fast green dye, a one microgram per microliter plasmid DNA solution of interest for each plasmid, and the appropriate volume on Endotoxin free TE buffer. And preload a glass microcapillary pipette with the appropriate prepared DNA solution. For the first in utero electroporation surgery, apply ointment to the eyes of an appropriately timed anesthetized pregnant mouse, and use a razor to shave the abdomen.Disinfect the exposed skin two times with sequential 70%ethanol and iodine wipes before proceeding with the incision on the right side of the abdomen. Once the uterus is accessible use ring forceps to carefully extract the organ. Using a mouth controlled aspirator tube, inject approximately 0.5 microliters of solution into the lateral ventricle of the left hemisphere of E11.5 embryos for strategy A.Or into the lateral ventricle of the right hemisphere of E13.5 embryos for strategy B, until the fast green dye is visible inside the ventricle.When all of the solution has been injected, place forceps type platinum electrodes laterally around of the head of the injected embryos, with the positive pole oriented to the medial wall to target the cortical hem for strategy A, or oriented to the lateral cortex for strategy B, taking care to avoid the heart and placenta. Use a square-wave electroporater to apply the appropriate sequence of electric pulses for each embryonic age, as indicated in the table. When all of the embryos have been injected and electroporated, use forceps to carefully return the uterus to the abdominal cavity, and fill the abdomen with warm saline.Using a needle 6-0 suture, close the abdominal wall, and carefully close the skin incision. Then return the animal to its home cage with monitoring until full recovery. Two days after the initial surgery, confirm that the mouse is exhibiting normal behavior, and presents no signs of pain or distress.Before preparing the animal for the second in utero electroporation as just demonstrated. Inject 0.5 microliters of the desired DNA solution into the left lateral brain ventricle of E13.5 embryos for strategy A, and into the left lateral brain ventricle of E15.5 embryos for strategy B.After each injection, place the electrodes with the positive pole oriented to the lateral cortex of the injected hemisphere for strategy A and strategy B.And electroporate embryos as indicated in the table. When the electroporation is finished, return the uterus to the abdominal cavity, and complete the surgery and post-surgical care as demonstrated.When implementing strategy A, four days after the second electroporation, harvest the uterus of the embryonic day 17.5 pregnant female mouse into a petri dish of PBS on ice. And use tweezers to transfer the embryos into a new dish of PBS under a dissecting microscope. Using forceps, carefully grasp the head of each embryo to facilitate removal of the skin over the head and skull.Use forceps or a spatula to lift out the exposed brains. Then use spoon to transfer each brain into individual wells of a 48 well plate containing around 600 microliters of fixative solution per well. When all of the brains have been collected, fix the brains at four degrees Celsius overnight on an orbital shaker, followed by three ten minute washes in PBS.After the last wash, embed the brains in 4%low melting point agarose in PBS for about ten minutes. After the agarose has solidified, use cyanoacrylate glue to secure each brain to a vibratome tissue holder olfactory bulb side up. Place the holder inside the vibratome container, and fill the container with PBS.Then use the vibratome and a brush to obtain 100 micrometer thick coronal serial sections. Transferring up to seven sections per well and six wells per embryo, in a new 48 well plate containing 600 microliters per well of fresh PBS, supplemented with anti-fungal preservatives as they are collected. When all of the sections have been acquired, use a fine brush to mount each section onto a glass microscope slide, and cover them with a glass coverslip for assessment of the electroporation efficacy on an upright epifluorescence microscope.When implementing strategy B, on postnatal day 15, after confirming a lack of response to topinch, secure the mouse in the supine position, and use scissors to make a midline skin incision to expose the ribcage and diaphragm, and cut the diaphragm to gain access to the heart. Using fine scissors, make an incision in the right atrium, and use a 25 gage needle connected to a flexible tube to a peristaltic perfusion pump to penetrate the left ventricle. When the needle is in place, deliver at least 25 milliliters of 4%paraformaldehyde by transcardial perfusion, at a constant flux at 5.5 milliliters per minute.After approximately five minutes, stop the perfusion, and use scissors to remove the skin over the head. Remove the skull, and use a spatula to remove the brain tissue. Place the brain into one well of a 24 well plate containing 1.5 milliliters of fresh 4%paraformaldehyde, for an overnight incubation at four degrees Celsius on an orbital shaker.Then acquire 40 micrometer sections of the postnatal brains as just demonstrated. For embryonic and postnatal brain slice imaging, place the slides containing the mounted brain sections of interest onto a microscope slide holder. Introduce the slider holder in the confocal microscope, and select the appropriate channel for the fluorofores used in the experiment.Perform sample scanning to obtain map images of each brain section at two different wavelengths for a general view of the double electroporation output. Once finished, select the 10x lens, in the multi-area Z-stack time lapse observation mode. In each of the select XY regions, set the appropriate imaging perimeters as well as the depth of the scanning along the Z axis according to the planes of the sample, in which the fluorescence is visible.Obtain low magnification images of all of the chosen regions, and export the images from OIF to TIFF format in the microscope viewer software. Then select the 60x lens, and capture high magnification images as just demonstrated, to observe the cell-to-cell interactions at a more detailed level. The temporal gap between the double in utero electroporation surgeries allows CAG toresial cells targeted on embryonic day 11.5 in one of its places of origin to reach the marginal zone of the lateral neocortex including the somatosensory area, in time to establish contacts with cortical projection neurons, labeled on embryonic day 13.5.The leading processes of projection neurons expressing enhanced GFP profusely uprise in the marginal zone of the cortex, and intermingle with the processes of M-cherry expressing cataretzial cells. In utero electroporation at embryonic day 13.5, using a BFP expressing plasmid facilitates the labeling of projection neurons across different cortical layers. A second electroporation in the contralateral side of embryonic day 15.5 targets the upper layer callosal projection neurons subpopulation, but not the lower layer projection neurons that develop at earlier stages.Upper layer targeted neurons extend their axons to the contralateral hemisphere, with the characteristic arborization pattern. High magnification allows a more detailed visualization of callosal axon innervation of the targeted projection neurons within the contralateral hemisphere. When attempting this protocol, it is important to plan electroporation timing, the hemisphere to inject, and the position of the electrodes according to the cell populations to be targeted.Following this procedure all the methods, such as electroporation is the interesting one. For both cell types can be performed to study possible circuit alterations in vivo. Using this technique, it is possible to study fine interactions between two different targeted cells.Including new science information in vivo, by the electroporation of fluorescent synaptic proteins.

double-utero-electroporation-to-target-temporally-spatially-separated

Research

JoVE Journal

Neuroscience

Ultrasound-Guided Microinjection into the Mouse Forebrain In Utero at E9.5

In utero survival surgery in mice permits the molecular manipulation of gene expression during development. However, because the uterine wall is opaque during early embryogenesis, the ability to target specific parts of the embryo for microinjection is greatly limited. Fortunately, high-frequency ultrasound imaging permits the generation of images that can be used in real time to guide a microinjection needle into the embryonic region of interest. Here we describe the use of such imaging to guide the injection of retroviral vectors into the ventricular system of the mouse forebrain at embryonic day (E) 9.5. This method uses a laparotomy to permit access to the uterine horns, and a specially designed plate that permits host embryos to be bathed in saline while they are imaged and injected. Successful surgeries often result in most or all of the injected embryos surviving to any subsequent time point of interest (embryonically or postnatally). The principles described here can be used with slight modifications to perform injections into the amnionic fluid of E8.5 embryos (thereby permitting infection along the anterior posterior extent of the neural tube, which has not yet closed), or into the ventricular system of the brain at E10.5/11.5. Furthermore, at mid-neurogenic ages (~E13.5), ultrasound imaging can be used direct injection into specific brain regions for viral infection or cell transplantation. The use of ultrasound imaging to guide in utero injections in mice is a very powerful technique that permits the molecular and cellular manipulation of mouse embryos in ways that would otherwise be exceptionally difficult if not impossible.

Ultrasound-Guided Microinjection into the Mouse Forebrain In Utero at E9.5

In utero survival surgery in mice permits the molecular manipulation of gene expression during development. Here we describe the use of high-frequency ultrasound imaging to guide the injection of retroviral vectors into the mouse brain at embryonic day (E) 9.5.

In utero survival surgery in mice permits the molecular manipulation of gene expression during development.  However, because the uterine wall is opaque ...

In utero Electroporation followed by Primary Neuronal Culture for Studying Gene Function in Subset of Cortical Neurons

In vitro study of primary neuronal cultures allows for quantitative analyses of neurite outgrowth. In order to study how genetic alterations affect neuronal process outgrowth, shRNA or cDNA constructs can be introduced into primary neurons via chemical transfection or viral transduction. However, with primary cortical cells, a heterogeneous pool of cell types (glutamatergic neurons from different layers, inhibitory neurons, glial cells) are transfected using these methods. The use of in utero electroporation to introduce DNA constructs in the embryonic rodent cortex allows for certain subsets of cells to be targeted: while electroporation of early embryonic cortex targets deep layers of the cortex, electroporation at late embryonic timepoints targets more superficial layers. Further, differential placement of electrodes across the heads of individual embryos results in the targeting of dorsal-medial versus ventral-lateral regions of the cortex. Following electroporation, transfected cells can be dissected out, dissociated, and plated in vitro for quantitative analysis of neurite outgrowth. Here, we provide a step-by-step method to quantitatively measure neuronal process outgrowth in subsets of cortical cells.
The basic protocol for in utero electroporation has been described in detail in two other JoVE articles from the Kriegstein lab 1, 2. We will provide an overview of our protocol for in utero electroporation, focusing on the most important details, followed by a description of our protocol that applies in utero electroporation to the study of gene function in neuronal process outgrowth.

In utero Electroporation followed by Primary Neuronal Culture for Studying Gene Function in Subset of Cortical Neurons

In utero electroporation is a valuable method for transfecting neuronal progenitor cells in vivo. Depending upon the placement of the electrodes and the developmental timepoint of electroporation, certain subsets of cortical cells can be targeted. Targeted cells can then be analyzed in vivo or in vitro for effects of genetic alteration.

In vitro study of primary neuronal cultures allows for quantitative analyses of neurite outgrowth. In order to study how genetic alterations affect ...

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 ...

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 ...

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 ...

A Novel Strategy Combining Array-CGH, Whole-exome Sequencing and In Utero Electroporation in Rodents to Identify Causative Genes for Brain Malformations

Birth defects that involve the cerebral cortex &#8212; also known as malformations of cortical development (MCD) &#8212; are important causes of intellectual disability and account for 20-40% of drug-resistant epilepsy in childhood. High-resolution brain imaging has facilitated in vivo identification of a large group of MCD phenotypes. Despite the advances in brain imaging, genomic analysis and generation of animal models, a straightforward workflow to systematically prioritize candidate genes and to test functional effects of putative mutations is missing. To overcome this problem, an experimental strategy enabling the identification of novel causative genes for MCD was developed and validated. This strategy is based on identifying candidate genomic regions or genes via array-CGH or whole-exome sequencing and characterizing the effects of their inactivation or of overexpression of specific mutations in developing rodent brains via in utero electroporation. This approach led to the identification of the C6orf70 gene, encoding for a putative vesicular protein, to the pathogenesis of periventricular nodular heterotopia, a MCD caused by defective neuronal migration.

A Novel Strategy Combining Array-CGH, Whole-exome Sequencing and In Utero Electroporation in Rodents to Identify Causative Genes for Brain Malformations

Periventricular nodular heterotopia (PNH) is the most common form of malformation of cortical development (MCD) in adulthood but its genetic basis remains unknown in most sporadic cases. We have recently developed a strategy to identify novel candidate genes for MCDs and to directly confirm their causative role in vivo.