Name: time-lapse confocal imaging of migrating neurons in organotypic slice culture of embryonic mouse brain using in utero electroporation
Uploaded: 2017-07-25T12:30:00
Description: Watch this Scientific Journal Video about Time-lapse Confocal Imaging of Migrating Neurons in Organotypic Slice Culture of Embryonic Mouse Brain Using In Utero Electroporation at JoVE.com

We thank Jacqueline Andratschke, Elena Werle, Sachi Takenaka, and Matthias Toberer for excellent technical assistance, as well as Victor Tarabykin for helpful discussions. This work was supported by a grant of the Deutsche Forschungsgemeinschaft to S.B. (BR-2215).

All experimental procedures were approved by the Animal Welfare Committee (Regierungspr&#228;sidium T&#252;bingen) and carried out in accordance by the German Animal Welfare Act and the EU Directive 2010/63/EU.
1. In Utero Electroporation
<ol>
	<li>Microinjection needles
	<ol>
		<li>Pull borosilicate glass capillaries (outer diameter: 1.0 mm, inner diameter: 0.58 mm, length: 100 mm) into microinjection needles using a micropipette puller with a box filament (2.5 mm ...

<ol>
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Radial migration is a key process in neocortex development. Mutations in genes affecting different steps of this process can cause severe cortical malformations, including lissencephaly and white matter heterotopia1,2. We recently showed that Bcl11a, which is expressed in young migrating cortical projection neurons, plays a role in radial migration. We used time-lapse confocal imaging of migrating neurons in acute cortical slices of electroporated brains to direc...

The neocortex is the major site of cognitive, emotional, and sensorimotor functions. It is composed of six horizontal layers oriented in parallel to the surface of the brain. During development progenitor cells in the lateral wall of the dorsal telencephalon give rise to projection neurons that migrate radially towards the pial surface and acquire a layer type-specific neuronal identity. After being generated in the ventricular/subventricular zones (VZ/SVZ) these neurons become transiently multipolar and slow their migration. After a short stay in the intermediate zone (IZ) they switch to a bipolar morphology, attach to the radial glial scaffold, and continue radially oriented migration into the cortical plate (CP). Upon reaching their final target projection neurons detach from the radial glial processes and acquire layer-specific identity. Mutations in genes affecting different steps of neuronal migration can cause severe cortical malformation, such as lissencephaly or white matter heterotopia1,2.
In utero electroporation is a rapid and powerful technique to transfect neural progenitor cells in the developing brain of rodent embryos3,4. With this technique it is possible to knockdown and/or overexpress genes of interest in order to study their functions in developing neurons. This method has specifically helped to describe the morphological details and characterize the molecular mechanisms of the process of radial migration5,6,7,8,9. Radially migrating neurons undergo dynamic changes in cell shape, migration speed, as well as migratory direction, which require direct and continuous observation over time. Organotypic slice culture and time-lapse confocal imaging of electroporated brains allow to directly observe migrating neurons over time. Using this combined approach, it is possible to analyze distinct features of migrating neurons that cannot be investigated in fixed tissue sections of electroporated brains.
We recently applied time-lapse confocal imaging of migrating neurons in slice cultures of electroporated brains to study the role of the transcription factor B cell CLL/lymphoma 11a (Bcl11a) during cortical development10. Bcl11a is expressed in young migrating cortical neurons and we used a conditional mutant Bcl11a allele (Bcl11aflox)11 to study its functions. Electroporation of Cre recombinase together with green fluorescent protein (GFP) into cortical progenitors of Bcl11aflox/flox brains allowed us to create a mosaic mutant situation, in which only few cells are mutated in an otherwise wild-type background. In this way, it was possible to study cell-autonomous functions of Bcl11a at the single cell level. We found that Bcl11a mutant neurons display reduced speed, shifts in their speed profiles, as well as random-like orientation changes during their migration10. In the outlined protocol we describe a workflow for successful electroporation and slice culture preparation12 of mouse brains, as well as time-lapse confocal imaging of cortical slice cultures.

<table border="0" cellpadding="0" cellspacing="0" width="771">
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		<tr height="21">
			<td height="21" style="height:21px;width:281px;">isoflurane</td>
			<td style="width:171px;">Abbott Laboratories&#160;</td>
			<td style="width:111px;">506949</td>
			<td style="width:209px;">Forene</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">6-well plate</td>
			<td style="width:171px;">Corning</td>
			<td style="width:111px;">351146</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">12-well plate</td>
			<td style="width:171px;">Corning</td>
			<td style="width:111px;">351143</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">non-absorbable surgical suture</td>
			<td style="width:171px;">Ethicon</td>
			<td style="width:111px;">K890H</td>
			<td>3/8 circle, 13 mm, taper point</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">Micro Adson Forceps</td>
			<td style="width:171px;">Fine Science Tools</td>
			<td style="width:111px;">11018-12</td>
			<td>serrated, length: 12 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">fine scissors</td>
			<td style="width:171px;">Fine Science Tools</td>
			<td style="width:111px;">14063-09</td>
			<td>angled to side, length: 9 cm</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:281px;">Mathieu Needle Holder</td>
			<td style="width:171px;">Fine Science Tools</td>
			<td style="width:111px;">12510-14</td>
			<td>tungsten carbide, length: 14 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">fine tipped forceps</td>
			<td style="width:171px;">Fine Science Tools</td>
			<td style="width:111px;">11370-40</td>
			<td>straight, 11 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">Vannas T&#252;bingen Spring Scissors</td>
			<td style="width:171px;">Fine Science Tools</td>
			<td style="width:111px;">15005-08</td>
			<td>angled up, 9.5 cm</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:281px;">ring forceps</td>
			<td style="width:171px;">Fine Science Tools</td>
			<td style="width:111px;">11103-09</td>
			<td>OD: 3mm, ID, 2.2 mm, length: 9 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">HBSS (10X)</td>
			<td style="width:171px;">Gibco</td>
			<td style="width:111px;">14180046</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">L-Glutamine</td>
			<td style="width:171px;">Gibco</td>
			<td style="width:111px;">25030081</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">Penicillin/Streptomycin</td>
			<td style="width:171px;">Gibco</td>
			<td style="width:111px;">15140122</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">horse serum</td>
			<td style="width:171px;">Gibco</td>
			<td style="width:111px;">26050088</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">BME</td>
			<td style="width:171px;">Gibco</td>
			<td style="width:111px;">41010026</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">borosilicate glass capillaries</td>
			<td style="width:171px;">Harvard Apparatus</td>
			<td style="width:111px;">30-0016</td>
			<td>1.0 OD x 0.58 ID x 100 L mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">anesthsesia system</td>
			<td style="width:171px;">Harvard Apparaus</td>
			<td style="width:111px;">72-6471</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">anesthetizing chamber</td>
			<td style="width:171px;">Harvard Apparaus</td>
			<td style="width:111px;">34-0460</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">fluosorber filter canister</td>
			<td style="width:171px;">Harvard Apparaus</td>
			<td style="width:111px;">34-0415</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">low melting point agarose</td>
			<td style="width:171px;">Invitrogen</td>
			<td style="width:111px;">16520100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">vibrating blade microtome</td>
			<td style="width:171px;">Leica</td>
			<td style="width:111px;">VT1200 S</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:281px;">fluorescence stereo microscope</td>
			<td style="width:171px;">Leica</td>
			<td style="width:111px;">M205 FA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">stereo microscope</td>
			<td style="width:171px;">Leica</td>
			<td style="width:111px;">M125</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:281px;">inverted fluorescence tissue culture microscope</td>
			<td style="width:171px;">Leica</td>
			<td style="width:111px;">DM IL LED</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">confocal laser scanning microscope</td>
			<td style="width:171px;">Leica</td>
			<td style="width:111px;">TCS SP5II</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">hybrid detector</td>
			<td style="width:171px;">Leica</td>
			<td style="width:111px;">HyD</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">objective, 40x/0.60 NA</td>
			<td style="width:171px;">Leica</td>
			<td style="width:111px;">11506201</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:281px;">microscope temperature control system</td>
			<td style="width:171px;">Life Imaging Services</td>
			<td style="width:111px;">Cube, Brick &#38; Box</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">cell culture insert</td>
			<td style="width:171px;">Millipore</td>
			<td style="width:111px;">PICM0RG50</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">microgrinder</td>
			<td style="width:171px;">Narishige</td>
			<td style="width:111px;">EG-45</td>
			<td>use 38&#176; angle for beveling</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">microinjector</td>
			<td style="width:171px;">Parker Hannifin&#160;</td>
			<td>052-0500-900</td>
			<td style="width:209px;">Picospritzer III</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:281px;">carprofen</td>
			<td style="width:171px;">Pfizer Animal Health</td>
			<td style="width:111px;">NDC 61106-8507</td>
			<td>Rimadyl</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">emdedding mold</td>
			<td style="width:171px;">Polysciences</td>
			<td style="width:111px;">18986-1</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:281px;">endotoxin-free plasmid maxi kit</td>
			<td style="width:171px;">Qiagen</td>
			<td style="width:111px;">12362</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">fast green</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:111px;">F7252</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">laminin</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:111px;">L2020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">poly-L-lysine</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:111px;">P5899</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">HEPES</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:111px;">H4034</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">D-glucose</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:111px;">G6152</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">calcium chloride</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:111px;">C7902</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">magensium sulfate</td>
			<td>Sigma</td>
			<td style="width:111px;">M2643</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">sodium bicarbonate</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:111px;">S6297</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">square wave electroporator</td>
			<td style="width:171px;">Sonidel</td>
			<td style="width:111px;">CUY21EDIT</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:281px;">tweezers with 5 mm platinum disk electrodes</td>
			<td style="width:171px;">Sonidel</td>
			<td style="width:111px;">CUY650P5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">micropipette puller</td>
			<td style="width:171px;">Sutter Instrument</td>
			<td style="width:111px;">P-97</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">box filament</td>
			<td style="width:171px;">Sutter Instrument</td>
			<td style="width:111px;">FB255B</td>
			<td>2.5 mm x 2.5 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:281px;">micro-spoon spatula</td>
			<td style="width:171px;">VWR</td>
			<td style="width:111px;">231-0191</td>
			<td>185 mm x 5 mm</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:281px;">glass bottom dish, 50 mm</td>
			<td style="width:171px;">World Precision Instruments</td>
			<td style="width:111px;">FD5040-100</td>
			<td></td>
		</tr>
	</tbody>
</table>

time-lapse confocal imaging of migrating neurons in organotypic slice culture of embryonic mouse brain using in utero electroporation

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

Previously, we have shown that genetic deletion of Bcl11a by in utero electroporation impairs radial migration of late-born upper-layer projection neurons10. Electroporation of a DNA plasmid vector containing Cre-IRES-GFP efficiently deleted Bcl11a in conditional Bcl11aflox/flox brains11. When we analyzed E14.5 electroporated brains three days after the electroporation, most control neu...

Watch this Scientific Journal Video about Time-lapse Confocal Imaging of Migrating Neurons in Organotypic Slice Culture of Embryonic Mouse Brain Using In Utero Electroporation at JoVE.com

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

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

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

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

The overall goal of this procedure is to directly observe radially migrating neurons in organotypic slice culture prepared from electroporated embryonic brain by time-lapse confocal microscopy. This method can help study key aspects of neocortex development. It allows investigation of the molecular mechanisms involved in neuron polarization and the radial migration of neurons to their final position within the brain.The main advantage of this technique is the dynamic properties of migrating neurons can be analyzed including speed profiles, average migration speed as well changes of migratory direction. Begin by placing a properly anesthetized pregnant mouse in the supine position on a warming plate. Check for the absence of the pedal reflex.And then, carefully cover the eyes with petroleum jelly to prevent them from drying. Next, gently spread out the limbs and fix them to the warming plate with surgical tape. Sterilize the abdomen by swabbing with 70%ethanol followed by iodine solution, then place sterile gauze, in which a cut has been made for the abdominal incision, over the abdomen.Moisten the gauze with bacteriostatic sodium chloride solution. After reassessing the development of surgical anesthesia, by loss of the pedal reflex, use serrated micro Adson forceps and angled fine scissors to cut the skin approximately 1.5 centimeters along the midline of the abdomen. Then, cut the underlying muscle along the linea alba.Grasp the uterine horn between embryos with ring forceps and gently place it onto the moistened gauze without perturbing the placentas or supply vessels. Then, carefully position an embryo to give a clear view of the lateral ventricle which presents as a crescent-shaped shadow parallel to the sagittal sinus. The injection site lies in the middle of a line between the pigmented eye and the confluence of sinuses where the sagittal sinus branches to two transfer sinuses.Once identified, push the microinjection needle through the uterine wall and into the lateral ventricle. Next, use a microinjector operated with a foot pedal to inject one to two microliters of DNA solution with five to 10 pulses. Successful injection can be monitored by the colored DNA solution which should fill the ventricular system.Then, place tweezers-type electrodes so that the positive terminal is on the same side as the injected ventricle and the negative terminal is on the opposite side of the injected ventricle below the ear of the embryo's head. Moisten the electroporation site with a few drops of bacteriostatic sodium chloride solution and apply five electrical current pulses of 50-millisecond duration with 950-millisecond intervals. Bubbles at the negative electrode indicate electrical current.60 to 90 milliamperes are usually sufficient for successful electroporation. Lower currents will not efficiently transfect neurons whereas higher currents may lead to embryonic death. After repeating the procedure for every embryo of the first uterine horn, gently place it back into the abdominal cavity.After suturing the muscle layer and skin, carefully disinfect with iodine solution and gently remove the petroleum jelly from the eyes using cellulose swabs. Place the mouse under an infrared lamp until it wakes up. After euthanizing the pregnant female using an approved method, remove the uterus containing the embryos and place it into a 10-centimeter Petri dish with ice-cold complete HBSS.From this point onward, keep all solutions, embryos and brains on ice. While working under a stereomicroscope, use fine-tipped forceps and a pair of Vannas Tubingen spring scissors to separate each embryo from the uterus. Transfer the embryos to another Petri dish containing ice-cold complete HBSS.Make an incision at the level of the brainstem and cut along the sagittal midline. Peel away the skin and cartilage covering the brain. Then, cut off the brainstem right behind the hemispheres and remove the brain from the skull.Transfer the brain with a micro spoon spatula to a 12-well plate containing ice-cold complete HBSS. Collect all brains from the litter in the 12-well plate. Then, use a fluorescent stereomicroscope to screen the brains in the 12-well plate for brightness of florescence as well as the size of the electroporated region.Select two to four brains with bright fluorescent signals and the presumptive somatosensory cortex for further processing. Then, pour molten 3%low-melting-point agarose solution into a peel-away disposable embedding mold. Use a micro spoon spatula to remove the brain from the 12-well plate and carefully drain excess complete HBSS from around the brain using fine tissue paper.Place the brain gently into the agarose solution. Then, use a 20-gauge needle to push it to the bottom of the mold and carefully adjust its position. For coronal sections, orient the brain with the olfactory bulbs pointing upwards.Keep the mold on ice until the agarose solution is solidified then proceed to sectioning the brain. Use a clean razor blade to trim away excess agarose around the brain leaving approximately one millimeter of agarose on all sides except for the olfactory bulbs where two to three millimeters of agarose should be left. After applying a small amount of cyanoacrylate glue to a specimen, fix the trimmed agarose block with the olfactory bulbs pointing downwards.Transfer the specimen stage to the slicing chamber of a vibrating blade microtome containing ice-cold complete HBSS and position the brain with its dorsal side towards the blade. Cut 250 micron-thick brain slices containing the electroporated region with a low to moderate amplitude and a very slow sectioning speed. Usually four to six slices with bright fluorescent signal are obtained from each successfully electroporated brain.Grasp the agarose rim of one section with fine-tipped forceps and pull the slice onto a bent micro spoon spatula. In this manner, carefully transfer the brain slices to a six-well plate containing ice-cold complete HBSS. Moisten laminin-coated membrane inserts with 100 microliters of complete HBSS.Then, carefully transfer the slices onto the membranes using the bent micro spoon spatula and forceps. Gently push the slice from the spatula onto the membrane, then position using forceps. Continue to transfer the remaining slices.Up to five slices can be placed on one membrane insert. Remove excess complete HBSS with a pipette. Then, with the help of forceps, carefully place the membrane inserts with the slices into a six-well plate containing 1.8 milliliters of sliced culture medium.Select a brain slice for imaging by viewing the slices through an inverted microscope. Choose a slice with bright single neurons in the upper SVZ migrating radially towards the pile surface of the slice. The presence of fine fluorescent processes of radial glial cells that span the entire conjugate plate indicates an intact radial glial scaffold which is used by migrating conjugate neurons.Transfer the membrane insert with a selected slice into a 50-millimeter-diameter glass-bottomed dish containing two milliliters of slice culture medium. Place the dish into the climate chamber of the confocal microscope. Set the resolution to 512 by 512 pixels.Increase the scan speed from 400 hertz to 700 hertz to increase the frame rate from about 1.4 to about 2.5 frames per second. Use no more than two times averaging. Define a Z-stack through the electroporated region with the step size of 1.5 microns.Start the time-lapse series by taking a Z-stack every 30 minutes. The settings described allow for sufficient resolution and brightness of the image while keeping photo damage low during acquisition. This movie shows E16.5 cortical neurons migrating from the ventricular subventrical zones to the cortical plate.In the Bcl11a floxed conditional transgenic after electroporation of the IRES-GFP control plasmid on embryonic day 14.5. The movie is comprised of 108 frames at the rate of five frames per second. The scale bar represents 100 microns.Electroporation of a DNA plasmid vector containing Cre-IRES-GFP affected cortical neuron migration in conditional Bcl11a floxed brains. As seen here, very few neurons move past the intermediate zone to reach the cortical plate. This movie shows the polarization of cortical neurons from a GFP-labeled control on the left compared to neurons from a Bcl11a mutant on the right.These animated traces of representative control in Bcl11a mutant neurons were obtained from time-lapse series of E16.5 slice cultures with one-hour-interval resolution. Again, data from the control brain is shown on the left and data from the Cre-IRES-GFP electroporated brain is shown on the right. As seen from this collection of representative traces from control and Bcl11a mutant slice cultures, the Bcl11a mutant neurons frequently undergo repetitive phases of reduced migration speed and randomly changed orientation as marked by the red arrowheads.Speed profiles can be calculated from traces of migrating neurons. As seen here, a greater proportion of Bcl11a mutant neurons have slower migration speeds compared to controls. The deviation angle may be calculated from the trace data.As seen from this histogram, the Bcl11a mutant neurons represented by the black bars exhibit greater angles of deviation compared to controls. Once mastered, this technique can be done in less than two hours each for the in utero electroporation and the preparation of organotypic brain slice culture. This procedure can easily be adapted to perform fractional analysis of genes of interest in radially migrating cortical neurons by gain and loss of function as well as vascular experiments.After watching this video, you should have a good understanding of how to directly observe radially migrating neurons in organotypic slice culture prepared from electroporated embryonic brains by time-lapse confocal microscopy.

time-lapse-confocal-imaging-migrating-neurons-organotypic-slice

Research

JoVE Journal

Neuroscience

Dissection and Culture of Commissural Neurons from Embryonic Spinal Cord

Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies of these neurons are located in the dorsal spinal cord and their axons follow stereotyped trajectories during embryonic development. Commissural axons initially project ventrally towards the floorplate. After crossing the midline, these axons turn anteriorly and project towards the brain. Each of these steps is regulated by the action of several guidance cues. Cultures highly enriched in commissural neurons are ideally suited for many experiments addressing the mechanisms of axon pathfinding, including turning assays, immunochemistry and biochemistry. Here, we describe a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. First, the spinal cord is isolated and dorsal strips are dissected out. The dorsal tissue is then dissociated into a cell suspension by trypsinization and mechanical disruption. Neurons are plated onto poly-L-lysine-coated glass coverslips or tissue-culture dishes. After 30 hours in vitro, most neurons have extended an axon. The purity of the culture (Yam et al. 2009), typically over 90%, can be assessed by immunolabeling with the commissural neuron markers DCC, LH2 and TAG1 (Helms and Johnson, 1998). This neuronal preparation is a useful tool for in vitro studies of the cellular and molecular mechanisms of commissural axon growth and guidance during spinal cord development.

This video demonstrates a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. Dissociated commissural neurons are useful to study the cellular and molecular mechanisms of axon growth and guidance.

Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies ...

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 ...

An Organotypic Slice Assay for High-Resolution Time-Lapse Imaging of Neuronal Migration in the Postnatal Brain

Neurogenesis in the postnatal brain depends on maintenance of three biological events: proliferation of progenitor cells, migration of neuroblasts, as well as differentiation and integration of new neurons into existing neural circuits. For postnatal neurogenesis in the olfactory bulbs, these events are segregated within three anatomically distinct domains: proliferation largely occurs in the subependymal zone (SEZ) of the lateral ventricles, migrating neuroblasts traverse through the rostral migratory stream (RMS), and new neurons differentiate and integrate within the olfactory bulbs (OB). The three domains serve as ideal platforms to study the cellular, molecular, and physiological mechanisms that regulate each of the biological events distinctly. This paper describes an organotypic slice assay optimized for postnatal brain tissue, in which the extracellular conditions closely mimic the in vivo environment for migrating neuroblasts. We show that our assay provides for uniform, oriented, and speedy movement of neuroblasts within the RMS. This assay will be highly suitable for the study of cell autonomous and non-autonomous regulation of neuronal migration by utilizing cross-transplantation approaches from mice on different genetic backgrounds.

This protocol describes an organotypic slice assay optimized for the postnatal brain and high-resolution time-lapse imaging of neuroblast migration in the rostral migratory stream.

Neurogenesis in the postnatal brain depends on maintenance of three biological events: proliferation of progenitor cells, migration of neuroblasts, as ...

Time-lapse Live Imaging of Clonally Related Neural Progenitor Cells in the Developing Zebrafish Forebrain

Precise patterns of division, migration and differentiation of neural progenitor cells are crucial for proper brain development and function1,2. To understand the behavior of neural progenitor cells in the complex in vivo environment, time-lapse live imaging of neural progenitor cells in an intact brain is critically required. In this video, we exploit the unique features of zebrafish embryos to visualize the development of forebrain neural progenitor cells in vivo. We use electroporation to genetically and sparsely label individual neural progenitor cells. Briefly, DNA constructs coding for fluorescent markers were injected into the forebrain ventricle of 22 hours post fertilization (hpf) zebrafish embryos and electric pulses were delivered immediately. Six hours later, the electroporated zebrafish embryos were mounted with low melting point agarose in glass bottom culture dishes. Fluorescently labeled neural progenitor cells were then imaged for 36hours with fixed intervals under a confocal microscope using water dipping objective lens. The present method provides a way to gain insights into the in vivo development of forebrain neural progenitor cells and can be applied to other parts of the central nervous system of the zebrafish embryo.

The present video demonstrates a method which takes advantage of the combination of electroporation and confocal microscopy to perform live imaging on individual neural progenitor cells in the developing zebrafish forebrain. In vivo analysis of the development of forebrain neural progenitor cells at a clonal level can be achieved in this way.

Precise patterns of division, migration and differentiation of neural progenitor cells are crucial for proper brain development and function1,2. To ...

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 ...

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 ...

In vivo Postnatal Electroporation and Time-lapse Imaging of Neuroblast Migration in Mouse Acute Brain Slices

The subventricular zone (SVZ) is one of the main neurogenic niches in the postnatal brain. Here, neural progenitors proliferate and give rise to neuroblasts able to move along the rostral migratory stream (RMS) towards the olfactory bulb (OB). This long-distance migration is required for the subsequent maturation of newborn neurons in the OB, but the molecular mechanisms regulating this process are still unclear. Investigating the signaling pathways controlling neuroblast motility may not only help understand a fundamental step in neurogenesis, but also have therapeutic regenerative potential, given the ability of these neuroblasts to target brain sites affected by injury, stroke, or degeneration.
In this manuscript we describe a detailed protocol for in vivo postnatal electroporation and subsequent time-lapse imaging of neuroblast migration in the mouse RMS. Postnatal electroporation can efficiently transfect SVZ progenitor cells, which in turn generate neuroblasts migrating along the RMS. Using confocal spinning disk time-lapse microscopy on acute brain slice cultures, neuroblast migration can be monitored in an environment closely resembling the in vivo condition. Moreover, neuroblast motility can be tracked and quantitatively analyzed. As an example, we describe how to use in vivo postnatal electroporation of a GFP-expressing plasmid to label and visualize neuroblasts migrating along the RMS. Electroporation of shRNA or CRE recombinase-expressing plasmids in conditional knockout mice employing the LoxP system can also be used to target genes of interest. Pharmacological manipulation of acute brain slice cultures can be performed to investigate the role of different signaling molecules in neuroblast migration. By coupling in vivo electroporation with time-lapse imaging, we hope to understand the molecular mechanisms controlling neuroblast motility and contribute to the development of novel approaches to promote brain repair.

In vivo Postnatal Electroporation and Time-lapse Imaging of Neuroblast Migration in Mouse Acute Brain Slices

Neuroblast migration is a fundamental event in postnatal neurogenesis. We describe a protocol for efficient labeling of neuroblasts by in vivo postnatal electroporation and subsequent visualization of their migration using time-lapse imaging of acute brain slices. We include a description for the quantitative analysis of neuroblast dynamics by video tracking.

The subventricular zone (SVZ) is one of the main neurogenic niches in the postnatal brain. Here, neural progenitors proliferate and give rise to ...

Ex Utero Electroporation and Organotypic Slice Cultures of Embryonic Mouse Brains for Live-Imaging of Migrating GABAergic Interneurons

GABAergic interneurons (INs) are critical components of neuronal networks that drive cognition and behavior. INs destined to populate the cortex migrate tangentially from their place of origin in the ventral telencephalon (including from the medial and caudal ganglionic eminences (MGE, CGE)) to the dorsal cortical plate in response to a variety of intrinsic and extrinsic cues. Different methodologies have been developed over the years to genetically manipulate specific pathways and investigate how they regulate the dynamic cytoskeletal changes required for proper IN migration. In utero electroporation has been extensively used to study the effect of gene repression or overexpression in specific IN subtypes while assessing the impact on morphology and final position. However, while this approach is readily used to modify radially migrating pyramidal cells, it is more technically challenging when targeting INs. In utero electroporation generates a low yield given the decreased survival rates of pups when electroporation is conducted before e14.5, as is customary when studying MGE-derived INs. In an alternative approach, MGE explants provide easy access to the MGE and facilitate the imaging of genetically modified INs. However, in these explants, INs migrate into an artificial matrix, devoid of endogenous guidance cues and thalamic inputs. This prompted us to optimize a method where INs can migrate in a more naturalistic environment, while circumventing the technical challenges of in utero approaches. In this paper, we describe the combination of ex utero electroporation of embryonic mouse brains followed by organotypic slice cultures to readily track, image and reconstruct genetically modified INs migrating along their natural paths in response to endogenous cues. This approach allows for both the quantification of the dynamic aspects of IN migration with time-lapse confocal imaging, as well as the detailed analysis of various morphological parameters using neuronal reconstructions on fixed immunolabeled tissue.

Ex Utero Electroporation and Organotypic Slice Cultures of Embryonic Mouse Brains for Live-Imaging of Migrating GABAergic Interneurons

Here, we provide a low-cost and reliable method to generate electroporated brain organotypic slice cultures from mouse embryos suitable for confocal microscopy and live-imaging techniques.

GABAergic interneurons (INs) are critical components of neuronal networks that drive cognition and behavior. INs destined to populate the cortex migrate ...

Ex Vivo Oculomotor Slice Culture from Embryonic GFP-Expressing Mice for Time-Lapse Imaging of Oculomotor Nerve Outgrowth

Accurate eye movements are crucial for vision, but the development of the ocular motor system, especially the molecular pathways controlling axon guidance, has not been fully elucidated. This is partly due to technical limitations of traditional axon guidance assays. To identify additional axon guidance cues influencing the oculomotor nerve, an ex vivo slice assay to image the oculomotor nerve in real-time as it grows towards the eye was developed. E10.5 IslMN-GFP embryos are used to generate ex vivo slices by embedding them in agarose, slicing on a vibratome, then growing them in a microscope stage-top incubator with time-lapse photomicroscopy for 24-72 h. Control slices recapitulate the in vivo timing of outgrowth of axons from the nucleus to the orbit. Small molecule inhibitors or recombinant proteins can be added to the culture media to assess the role of different axon guidance pathways. This method has the advantages of maintaining more of the local microenvironment through which axons traverse, not axotomizing the growing axons, and assessing the axons at multiple points along their trajectory. It can also identify effects on specific subsets of axons. For example, inhibition of CXCR4 causes axons still within the midbrain to grow dorsally rather than ventrally, but axons that have already exited ventrally are not affected.

An ex vivo slice assay allows oculomotor nerve outgrowth to be imaged in real time. Slices are generated by embedding E10.5 IslMN:GFP embryos in agarose, slicing on a vibratome, and growing in a stage-top incubator. The role of axon guidance pathways is assessed by adding inhibitors to the culture media.