The authors acknowledge the Foundation Leducq (MITRAL) and the Agence Nationale pour la Recherche (grant ANR Specistem) for funding this research.

1. Preparation
Animal procedures
Obtain approval from an animal ethical committee and follow institutional guidelines for work with virus, HuESC and/or iPSC (when applicable), as well as mouse handling, obtaining mouse embryos, and performing mouse surgery. For timed matings, the day of the plug is considered embryonic day (E)0.5 / 0.5 days post-coitum.
<ol>
	<li>Microinjection needles: 
	For ex utero microinjection, pull glass pipettes (1.2 mm external diameter borosilicate capillary tubes) using a pipette puller/beveller to get a 1 or 10 &#956;m internal tip diameter and a sharp and conic tip shape to inject DNA or cells, respectively. For ultrasound-mediated injections, use customized sterile needles, which have an outer/inner diameter (OD/ID) of 1.14 mm/0.53 mm, with a 50/35 &#956;m OD/ID tip.</li>
	<li>Silicon-filled Petri dishes: 
	Prepare silicon as described in the manual. Fill a clean glass 60 mm diameter Petri dish with an elastomer layer of ~1 cm. Avoid air bubbles.</li>
	<li>Instruments: 
	Keep all surgical instruments sterile prior to and during the procedure.</li>
	<li>DNA preparation: 
	Add 3 &#956;g DNA and 12 &#956;l Opti-MEM in one tube. Add 3 &#956;l Lipofectamine 2000 and 12 &#956;l Opti-MEM in another tube. Incubate for 5 min at RT and mix both solutions. Use immediately.</li>
	<li>Cell preparation: 
	Prepare a suspension of 106 cells/ml DMEM (Dulbecco&#8217;s Eagle Medium, high glucose and 50% rat serum). 50 &#956;l of final cell suspension is enough for 8-10 embryos.</li>
	<li>Dye preparation: 
	Use the green fluorescent CDCFDA-SE at 25 mg/ml DMSO. Prepare 20 &#181;l aliquots and store at -20 &#176;C. Dilute 1:100/1:200 in sterile saline or PBS before use.</li>
	<li>Virus preparation: 
	Use a commercial 3rd generation PGK-GFP-expressing lentivirus with a titer of ~109-1010 transducing units/ml DMEM. For the preparation of lentivirus, see Tiscornia et al.14 Wear personal protective equipment and safely use and dispose of virus.</li>
</ol>
2. Collection of E9.5 and E10.5 Embryos for Ex vivo Injection
<ol>
	<li>Euthanize a pregnant mouse at embryonic day 9.5 or 10.5.</li>
	<li>Sterilize the chest and abdomen of the mouse with 70% ethanol.</li>
	<li>Make a ventral midline incision to open the abdomen and retrieve the uterine horn at RT in PBS and transfer it after two PBS washes to a silicone-filled Petri dish with M16 medium.</li>
	<li>Pin the uterine horn with insect pins to the silicone layer so that the vascularized side of the uterus is at the bottom.</li>
	<li>Cut the surface of the uterus with fine forceps, and a cap of the decidua at 1 mm below the surface.</li>
	<li>Gently retrieve the embryo in the yolk sac by spreading out the walls of the decidua.</li>
	<li>Store the embryos at 37 &#176;C in M16 medium before cell injection. For injection, each embryo is transferred to the silicone dish filled with M16 medium pre-warmed at 37 &#176;C.</li>
</ol>
3. DNA or Cell Injection Under a Stereomicroscope
<ol>
	<li>Fill the glass pipette from the back with a Hamilton syringe and shake the pipette to remove bubbles at the tip.</li>
	<li>Set the pipette on the microinjection holder; set the holding pressure to 50 (DNA) or 30 (cells) hPa, and the injection pressure to 150 (DNA) to 300 (cells) hPa. Set the injection time to 0.2 sec (DNA) or 0.5 sec (cells). These settings might slightly vary according to the type of microinjector and pipette.</li>
	<li>Pin the embryo to the silicone bottom through the yolk sac without touching the embryo proper. Watch the region of the heart and open the sac just above this region.</li>
	<li>Add 4 pins around the embryo to prevent any motion during cell injection.</li>
	<li>Using the micromanipulator (set to manual), slowly position the pipette tip at an angle of 45&#176; above the pericardium, just above the region of the heart that is to be injected (Figure 1).</li>
	<li>Move the pipette into the region of interest and trigger the injection. Take out the pipette as quickly as possible. Make sure the heart is properly beating after DNA/cell injection.</li>
</ol>
4. Embryo, Isolated Heart, and Explant Culture
<ol>
	<li>Culture the E9.5 embryos in 25% M2 medium and 75% rat serum, supplemented with penicillin/streptomycin, pre-warmed at 37 &#176;C and oxygenated with 40% O2.</li>
	<li>Add 2 ml culture medium in a 25 ml glass tube, gently add the embryo, and oxygenate with 40% O2 before screwing the cap onto the tube. Incubate up to 36 hr at 37 &#176;C while rotating or shaking (30 rotations/min).</li>
	<li>At the desired time point (e.g. 24 hr), dissect the hearts carefully with fine forceps, without touching the hearts, by first decapitating the embryos; the heart is easy to excise by pulling it out using the distal outflow tract.</li>
	<li>Culture the isolated heart for another 36-48 hr in DMEM with 50% FCS on a Matrigel-coated insert set in a 12-well plate. See Dyer &#38; Patterson (2013) for an improved protocol of heart culture15.</li>
	<li>Make any explant of the region of interest. As an example, dissect the atrio-ventricular canal (AVC) and culture it for 48 hr on collagen type 1 gel16.</li>
</ol>
5. Ultrasound-guided Injection in the Heart In utero
<ol>
	<li>Setup of ultrasound machine and microinjector:
	<ol>
		<li>Use the high-resolution ultrasound system with a 40 MHz transducer and microinjection setup on a rail.</li>
		<li>Set the injection volume on the microinjector at 69 nl per injection. See the manufacturer&#8217;s microinjection manual for programming the microinjector.</li>
	</ol>
	</li>
	<li>Preparation of the microinjection setup and injection:
	<ol>
		<li>Place a glass micropipette in the microinjector. To ensure efficient injection, first coat the inner side of the pipette with mineral oil by aspirating up to the maximum volume. Then eject the oil again, leaving 1-2 mm of oil inside the needle.</li>
		<li>Aspirate the injectate until maximum volume is reached. Be careful not to touch any surfaces with the needle tip as this will blunt the tip and make injection more difficult.</li>
		<li>To stabilize the uterine horn containing the embryos during injection, use a modified Petri dish with a hole in the middle (2.5 cm diameter), covered by a thin silicone membrane with a small slit cut in the center, and position it above the incision site. Stabilize the Petri dish on the mouse handling table by positioning 3-4 clumps of clay under the edges of the dish.</li>
	</ol>
	</li>
	<li>Injection procedure:
	<ol>
		<li>Shave the abdomen of a pregnant mouse (at the desired embryonic stage) prior to anesthesia to remove hair. Treat the abdomen with a chemical hair removal agent to remove residual hair and sterilize with 70% ethanol.</li>
		<li>Anesthetize a pregnant mouse with oxygen/isoflurane via a face mask. Use 3-5% isoflurane in 100% oxygen for initial anesthesia, followed by 1-1.5% during the rest of the procedure. Ensure that the mouse is adequately anesthetized by gently pinching its paws and/or tail.</li>
		<li>Place the mouse supine on the mouse handling table (set to heat at 37 &#176;C) and cover the eyes with lubricant to prevent dehydration of the cornea.</li>
		<li>Apply electrode gel on the electrodes and tape the paws to the electrodes to monitor heart rate, respiration rate, and ECG. Position a rectal thermometer to monitor body temperature.</li>
		<li>Verify first that the mouse is pregnant by visualizing and counting the embryos by ultrasound. Apply ultrasound gel on the abdomen and position the scan head above the bladder. For consistency, visualize the bladder first, and count embryos in the left and right uterine horns, starting from the position of the bladder. Ensure that embryonic hearts are beating normally.</li>
		<li>If the mouse is pregnant, position the Petri dish above the future incision site with clay. Press the dish slightly onto the abdomen so that the dish is in direct contact.</li>
		<li>Remove the dish and sterilize the abdomen again. Make a 1.5-2 cm ventral midline incision, approximately 0.75-1 cm above the vagina, to open the abdomen and peritoneum. Avoid injury to internal organs.</li>
		<li>Exteriorize the left or right uterine horn with forceps, gently pull it through the silicon membrane of the dish, and stabilize the dish on the clay again. Prevent extensive pulling or manipulation, since this may cause bleeding of the uterine vessels and premature death of the female and/or embryos.</li>
		<li>Count the embryos again to ensure adequate record keeping of which embryos were injected.</li>
		<li>Apply ultrasound gel on the uterine horns to image the heart and to prevent dehydration.</li>
		<li>Image the first embryo to be injected. Check normal beating of the embryonic heart and keep records of the cranial-caudal and left-right orientation of the embryo. If necessary, reposition the uterine horn slightly to ensure proper orientation. If this proves difficult, move on to the next embryo.</li>
		<li>Puncture the uterus carefully with the microinjection needle to position the needle in a 45&#176; angle above the embryo, slightly outside of the pericardium (Figure 3). For labeling of epicardial cells, image the heart in a four-chamber view and position the needle so that it points towards the atrio-ventricular groove (Figure 3). If the angle needs to be adjusted, pull out the needle, and reposition. Do not adjust the angle with the needle inside the uterus, since this might break the needle. Avoid puncturing other tissues, such as limbs or placenta.</li>
		<li>Move the needle onto the pericardial wall and puncture it with a gentle, but swift motion. In general, there will be some resistance, but moving the needle too fast may cause the needle tip to puncture the heart itself. The tip should end up in the pericardial space of the atrio-ventricular groove. In the case of pericardial bleeding, blood cells will be visible as a white snow-like pattern. If this is the case, stop injecting the embryo and move on to another embryo.</li>
		<li>Inject the injectate. Inject maximally 700 nl into the pericardial space to prevent adverse effect on hearts development. Monitor the proper injection by slight, temporal swelling of the pericardial sac.</li>
		<li>Following injection, pull the needle out and confirm that injectate can still be ejected to ensure that the needle was not clogged by tissue fragments.</li>
		<li>Reposition the handling table to image and inject the next embryo. Keep the number of injected embryos to maximally 3-4 (in one uterine horn) to prevent extended anesthesia, to allow for control embryos in the opposed uterine horn, and to ensure that the procedure did not disturb embryonic development.</li>
		<li>After injecting the desired number of embryos, remove excess ultrasound gel and gently place the uterine horn back into the abdomen in its proper position.</li>
		<li>Close the maternal abdomen by using one layer of suture for the peritoneum and abdominal muscles, and a second layer of suture for the skin.</li>
		<li>Inject the mouse with the first dose of pain medication. Use one injection of 0.05-0.1 mg/kg Buprenorphine 15 min prior to ending anesthesia and three additional injections with 12 hr intervals.</li>
		<li>Discontinue anesthesia and monitor the mouse for adequate recovery from the procedure. House the pregnant mouse in an individual cage for the desired duration of follow-up.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Thomson, J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Embryonic+stem+cell+lines+derived+from+human+blastocysts.">Embryonic stem cell lines derived from human blastocysts.</a> Science. 282, 1145-1147 (1998).</li><li>Takahashi, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+pluripotent+stem+cells+from+adult+human+fibroblasts+by+defined+factors.">Induction of pluripotent stem cells from adult human fibroblasts by defined factors.</a> Cell. 131, 861-872 (2007).</li><li>Mummery, C. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differentiation+of+human+embryonic+stem+cells+and+induced+pluripotent+stem+cells+to+cardiomyocytes:+a+methods+overview.">Differentiation of human embryonic stem cells and induced pluripotent stem cells to cardiomyocytes: a methods overview.</a> Circ. Res. 111, 344-358 (2012).</li><li>Badylak, S. F., Taylor, D., Uygun, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole-organ+tissue+engineering:+decellularization+and+recellularization+of+three-dimensional+matrix+scaffolds.">Whole-organ tissue engineering: decellularization and recellularization of three-dimensional matrix scaffolds.</a> Annu. Rev. Biomed. Eng. 13, 27-53 (2011).</li><li>Dickinson, L. E., Kusuma, S., Gerecht, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reconstructing+the+differentiation+niche+of+embryonic+stem+cells+using+biomaterials.">Reconstructing the differentiation niche of embryonic stem cells using biomaterials.</a> Macromol. Biosci. 11, 36-49 (2011).</li><li>Van Vliet, P., Zaffran, S., Wu, S., Puceat, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+cardiac+development:+a+view+from+stem+cells+to+embryos.">Early cardiac development: a view from stem cells to embryos.</a> Cardiovasc. Res. In press, (2012).</li><li>Cai, C. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+myocardial+lineage+derives+from+Tbx18+epicardial+cells.">A myocardial lineage derives from Tbx18 epicardial cells.</a> Nature. 454, 104-108 (2008).</li><li>Boulland, J. L., Halasi, G., Kasumacic, N., Glover, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Xenotransplantation+of+human+stem+cells+into+the+chicken.">Xenotransplantation of human stem cells into the chicken.</a> J. Vis. Exp. , (2010).</li><li>Liu, A., Joyner, A. L., Turnbull, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alteration+of+limb+and+brain+patterning+in+early+mouse+embryos+by+ultrasound-guided+injection+of+Shh-expressing+cells.">Alteration of limb and brain patterning in early mouse embryos by ultrasound-guided injection of Shh-expressing cells.</a> Mech. Dev. 75, 107-115 (1998).</li><li>Pierfelice, T. J., Gaiano, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound-guided+microinjection+into+the+mouse+forebrain+in+utero+at+E9.5.">Ultrasound-guided microinjection into the mouse forebrain in utero at E9.5.</a> J. Vis. Exp. , (2010).</li><li>Nagy, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cre+recombinase:+the+universal+reagent+for+genome+tailoring.">Cre recombinase: the universal reagent for genome tailoring.</a> Genesis. 26, 99-109 (2000).</li><li>Buckingham, M. E., Meilhac, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracing+cells+for+tracking+cell+lineage+and+clonal.">Tracing cells for tracking cell lineage and clonal.</a> Dev. Cell. 21, 394-409 (2011).</li><li>Phoon, C. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+tools+for+the+developmental+biologist:+ultrasound+biomicroscopy+of+mouse+embryonic+development.">Imaging tools for the developmental biologist: ultrasound biomicroscopy of mouse embryonic development.</a> Pediatr. Res. 60, 14-21 (2006).</li><li>Tiscornia, G., Singer, O., Verma, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+and+purification+of+lentiviral+vectors.">Production and purification of lentiviral vectors.</a> Nat. Protoc. 1, 241-245 (2006).</li><li>Dyer, L. A., Patterson, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Novel+Ex+vivo+Culture+Method+for+the+Embryonic+Mouse.">A Novel Ex vivo Culture Method for the Embryonic Mouse.</a> J. Vix. Exp. , (2013).</li><li>Runyan, R. B., Markwald, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Invasion+of+mesenchyme+into+three-dimensional+collagen+gels:+a+regional+and+temporal+analysis+of+interaction+in+embryonic+heart+tissue.">Invasion of mesenchyme into three-dimensional collagen gels: a regional and temporal analysis of interaction in embryonic heart tissue.</a> Dev. Biol. 95, 108-114 (1983).</li></ol>

The authors have nothing to disclose.

The intra-cardiac ex vivo injection protocols described above are designed to preserve myocardial function for at least 48 hr in mid-stage (E9.5- E11.5) mouse embryos. These injection approaches allow for spatially targeted injection of DNA or cells. The few examples shown in Figures 1-3 provide proof of concept for delineating ex vivo and in vivo molecular mechanisms of developmental processes that take place in restricted cardiac regions, such as EMT of endocardial or epicard...

More than a decade ago, human embryonic stem cells (HuESCs) have been derived from human blastocysts1. Since then, these cells have become the subject of an important field of research which addresses unmet questions in human developmental biology. HuESCs have furthermore provided hopes in regenerative medicine. In recent years, human induced pluripotent stem cells (iPSCs) have been generated from patient-specific somatic cells, providing models of genetic disease2. Many in vitro protocols for differentiation of embryonic or induced pluripotent stem cells towards various cell lineages, including heart lineages3, have been reported. The differentiated cells are often phenotyped by analysis of RNA and protein expression, immunostaining, and/or in vitro functional tests. However, pluripotent stem cell derivatives have to be placed in a proper embryonic environment in order to test whether they fully acquire the cell fate of their embryonic counterpart and whether they recapitulate the genuine in vivo function in response to regional cues. While tissue engineering is promising, it does not yet provide all the known and unknown cues of the proper in vivo developing embryonic tissue4,5.
Cell labeling with dyes or retroviral vectors in embryos, including mouse embryos, have brought important information as to the embryonic origin of cell lineages during cardiac development6. For example, dye injection into the pericardial space of mouse embryos ex vivo, followed by in vitro culture of isolated hearts, was used to label epicardial cells and their descendants7. However, dye and retroviral cell labeling have been mostly applied to early mouse embryos with still poorly developed organs, or chicken embryos, which are more easily accessible8. An exception is the brain, which is easier to target in embryos9,10. Such an approach has not yet been applied to the beating embryonic mouse heart.
To complement direct labeling with dyes or virus and to perform lineage tracing in more advanced stage mouse embryos and adult mice, the cell labeling approach has been combined with analysis of transgenic mice using the Cre/Lox technology. The Cre/Lox approach11 however features some limitations due to the spatiotemporal specificity of the genomic regulatory regions used to drive expression of the recombinase, and the efficiency of the Cre/Lox recombination12. Furthermore, this approach does not fully address the specific questions of cell migration-driven acquisition of cell fate as it can only label a precursor after activation of the regulatory region used to drive Cre expression. It also&#160;cannot apply to human embryos for obvious ethical issues.
Given these limitations, we designed a series of new protocols to inject a variety of cell labeling agents such as fluorescent dyes, virus, gene expression modulators such as shRNAs and DNA-based cell labeling vectors, or cells in the mouse embryo at E9.5 and later stages of development in targeted regions of the heart.
The DNA/cell injections use a stereomicroscope and a simple microinjection device combined with ex vivo embryo culture up to 48 hr, or isolated heart or embryonic explant culture for 48-72 hr. We also report an ultrasound-mediated microinjection protocol in mouse embryonic hearts in utero. This technique allows monitoring the development of embryos13 and allows for long-term follow-up of the injectates and/or labeled cells.
We found that these approaches preserve the function of the organ and provide a more representative environment than in vitro testing of stem cell potential. It also provides the opportunity to follow migration of labeled and/or injected cells to monitor their fate. Ultimately, this should yield a better understanding of regional tissue patterning and key biological processes.

<table border="0" cellpadding="0" cellspacing="0" width="986">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Setups / Hardware</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td style="width:411px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">40 MHz Transducer</td>
			<td style="width:175px;">VisualSonics</td>
			<td>MS550S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Microinjector</td>
			<td style="width:175px;">VisualSonics</td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microinjector&#160;</td>
			<td style="width:175px;">Eppendorf</td>
			<td>5242</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micromanipulator&#160;</td>
			<td style="width:175px;">Eppendorf</td>
			<td>5171</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Nitrogen</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td>required to pressurize the injector</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Rail system</td>
			<td style="width:175px;">VisualSonics</td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">rotator</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td>to rotate glass tube with embryos inside the incubator</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Standard incubator</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td>5% CO2, 37 C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">stereomicroscope</td>
			<td style="width:175px;">Zeiss</td>
			<td style="width:104px;">Discovery. V8</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Vevo 2100</td>
			<td style="width:175px;">VisualSonics</td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;"></td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Microinjection</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">borosilicate capillary tubes</td>
			<td style="width:175px;">World Precision Instrument</td>
			<td style="width:104px;">KTW-120-6</td>
			<td>1.2 mm external diameter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">pipette puller&#160;</td>
			<td style="width:175px;">Sutter</td>
			<td style="width:104px;">Model P87</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">microinjection needles</td>
			<td>Origio-Humagen&#160;</td>
			<td>C060609</td>
			<td>OD/ID 1.14mm/53mm, with 50/35 um OD/ID tip</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hamilton syringes&#160;</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Petridishes</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td>10 cm diameter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mineral oil&#160;</td>
			<td style="width:175px;">Sigma</td>
			<td>M8410</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Silicon membrane</td>
			<td style="width:175px;">Visualsonics</td>
			<td style="width:104px;"></td>
			<td>4.3x4.3 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Play-Doh</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Isoflurane</td>
			<td style="width:175px;">Vet One</td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">hair removal agent&#160;</td>
			<td style="width:175px;">Nair</td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:297px;">eye lubricant</td>
			<td style="width:175px;">Optixcare</td>
			<td>31779</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Electrode gel (Signa)</td>
			<td style="width:175px;">Parker</td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Suture</td>
			<td style="width:175px;">Sofsilk 5-0</td>
			<td style="width:104px;">S1173</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Ultrasound gel</td>
			<td style="width:175px;">Aquasonic</td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Buprenex Buprenex (buprenorphine hydrochloride)</td>
			<td style="width:175px;">Reckitt Benckiser Pharmaceuticals Inc.</td>
			<td style="width:104px;">NDC 12496-0757-1</td>
			<td>0.05-0.1 mg/kg in saline</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;"></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Other</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Silicone Elastomer</td>
			<td>Dow Corning</td>
			<td>Sylgard 184&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Glass petridishes</td>
			<td>Fine Science Tools&#160;</td>
			<td style="width:104px;"></td>
			<td>60mm diameter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">insect pins&#160;</td>
			<td>Fine Science Tools&#160;</td>
			<td>26002-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;"></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Media and culture reagents</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Optimem medium</td>
			<td style="width:175px;">Life Technologies</td>
			<td style="width:104px;">51985026</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">M2 medium&#160;</td>
			<td style="width:175px;">Sigma</td>
			<td style="width:104px;">M7167</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s Eagle Medium</td>
			<td style="width:175px;">Lonza</td>
			<td style="width:104px;">BE12-640F</td>
			<td>high glucose and 50% rat serum</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">M16 medium&#160;</td>
			<td style="width:175px;">Sigma</td>
			<td style="width:104px;">M7292</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">rat serum</td>
			<td style="width:175px;">Janvier</td>
			<td style="width:104px;">ODI 7158</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">pennicilin/streptomycin&#160;</td>
			<td style="width:175px;">Life Technologies</td>
			<td style="width:104px;">15140-12</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">oxygen 40%</td>
			<td style="width:175px;">Air liquid</td>
			<td style="width:104px;"></td>
			<td>required to oxygenate the embryo culture medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">fetal calf serum</td>
			<td style="width:175px;">Fisher</td>
			<td style="width:104px;">RVJ35882</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">matrigel</td>
			<td style="width:175px;">BD</td>
			<td style="width:104px;">356230</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">collagen type I</td>
			<td style="width:175px;">BD</td>
			<td style="width:104px;">354236</td>
			<td>to coat culture dishes for explant culture</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">culture dishes</td>
			<td style="width:175px;">Dutcher /Orange</td>
			<td style="width:104px;">131020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;"></td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Injectates</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CDCFDA-SE&#160;</td>
			<td>Invitrogen/Molecular Probes&#160;</td>
			<td>C1165</td>
			<td>25mg/ml DMSO. Store at -20 C. Dilute 1:100-200 in saline before use.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PGK-GFP-expressing lentivirus&#160;</td>
			<td style="width:175px;"></td>
			<td style="width:104px;"></td>
			<td>~8E9 transducing units/ml DMEM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">lipofectamine 2000&#160;</td>
			<td style="width:175px;">Life Technologies</td>
			<td style="width:104px;">11668019</td>
			<td></td>
		</tr>
	</tbody>
</table>

cell labeling and injection in developing embryonic mouse hearts

Testing the fate of embryonic or pluripotent stem cell-derivatives in in vitro protocols has led to controversial outcomes that do not necessarily reflect their in vivo potential. Preferably, these cells should be placed in a proper embryonic environment in order to acquire their definite phenotype. Furthermore, cell lineage tracing studies in the mouse after labeling cells with dyes or retroviral vectors has remained mostly limited to early stage mouse embryos with still poorly developed organs. To overcome these limitations, we designed standard and ultrasound-mediated microinjection protocols to inject various agents in targeted regions of the heart in mouse embryos at E9.5 and later stages of development. &#160;Embryonic explant or embryos are then cultured or left to further develop in utero. These agents include fluorescent dyes, virus, shRNAs, or stem cell-derived progenitor cells. Our approaches allow for preservation of the function of the organ while monitoring migration and fate of labeled and/or injected cells. These technologies can be extended to other organs and will be very helpful to address key biological questions in biology of development.

Using the injection protocols described above, cells can be labeled and/or injected into the embryonic mouse heart. As proof of concept, several examples are shown in which the injection protocol and the ex vivo AVC explant, isolated heart, or whole embryo culture were combined (Figure 1).
Figure 1 shows the preparation of the embryo before cell injection. The E9.5 embryo is removed from its decidua while maintaining integrity of the yolk sac (<strong...

Watch this Scientific Journal Video about Cell Labeling and Injection in Developing Embryonic Mouse Hearts at JoVE.com

Cell Labeling and Injection in Developing Embryonic Mouse Hearts

We describe a series of methods to inject dyes, DNA vectors, virus, and cells in order to monitor both cell fate and phenotype of endogenous and grafted cells derived from embryonic or pluripotent cells within mouse embryos at embryonic day (E)9.5 and later stages of development.

Testing the fate of embryonic or pluripotent stem cell-derivatives in in vitro protocols has led to controversial outcomes that do not necessarily reflect ...

cell-labeling-and-injection-in-developing-embryonic-mouse-hearts

Research

JoVE Journal

Biology

14.1K Views.  Aix-Marseille University. We describe a series of methods to inject dyes, DNA vectors, virus, and cells in order to monitor both cell fate and phenotype of endogenous and grafted cells derived from embryonic or pluripotent cells within mouse embryos at embryonic day (E)9.5 and later stages of development.

Video: Cell Labeling and Injection in Developing Embryonic Mouse Hearts

Measuring Exocytosis in Neurons Using FM Labeling

The ability to measure the kinetics of vesicle release can help provide insight into some of the basics of neurotransmission.  Here we used real-time imaging of vesicles labeled with FM dye to monitor the rate of presynaptic vesicle release.  FM4-64 is a red fluorescent amphiphilic styryl dye that embeds into the membranes of synaptic vesicles as endocytosis is stimulated.  Lipophilic interactions cause the dye to greatly increase in fluorescence, thus emitting a bright signal when associated with vesicles and a nominal one when in the extracellular fluid. After a wash step is used to help remove external dye within the plasma membrane, the remaining FM is concentrated within the vesicles and is then expelled when exocytosis is induced by another round of electrical stimulation. The rate of vesicles release is measured from the resulting decrease in fluorescence.  Since FM dye can be applied external and transiently, it is a useful tool for determining rates of exocytosis in neuronal cultures, especially when comparing the rates between transfected synapses and neighboring control boutons.



The ability to measure the kinetics of vesicle release can help provide insight into some of the basics of neurotransmission. Here we used real-time imaging of vesicles labeled with the red fluorescent dye FM 4-64 to measure the rate of presynaptic vesicle release in hippocampal neuronal cultures.

Pomiar egzocytozy w Neurony Korzystanie FM etykietowania

The ability to measure the kinetics of vesicle release can help provide insight into some of the basics of neurotransmission.  Here we used real-time ...

Single Cell Electroporation in vivo within the Intact Developing Brain

Single-cell electroporation (SCE) is a specialized technique allowing the delivery of DNA or other macromolecules into individual cells within intact tissue, including in vivo preparations. The distinct advantage of this technique is that experimental manipulations may be performed on individual cells while leaving the surrounding tissue unaltered, thereby distinguishing cell-autonomous effects from those resulting from global treatments. When combined with advanced in vivo imaging techniques, SCE of fluorescent markers permits direct visualization of cellular morphology, cell growth, and intracellular events over timescales ranging from seconds to days. While this technique is used in a variety of in vivo and ex vivo preparations, we have optimized this technique for use in Xenopus laevis tadpoles. In this video article, we detail the procedure for SCE of a fluorescent dye or plasmid DNA into neurons within the intact brain of the albino Xenopus tadpole. We also discuss methods to optimize yield, and show examples of live two-photon fluorescence imaging of neurons fluorescently labeled by SCE.

Single-cell electroporation (SCE) is a specialized technique allowing delivery of DNA or other macromolecules into individual cells within intact tissue, including in vivo preparations. Here we detail the procedure for SCE of a fluorescent dye or plasmid DNA into neurons within the intact brain of the Xenopus laevis tadpole.

Single-cell electroporation (SCE) is a specialized technique allowing the delivery of DNA or other macromolecules into individual cells within intact ...

In vitro Labeling of Human Embryonic Stem Cells for Magnetic Resonance Imaging

Human embryonic stem cells (hESC) have demonstrated the ability to restore the injured myocardium. Magnetic resonance imaging (MRI) has emerged as one of the predominant imaging modalities to assess the restoration of the injured myocardium. Furthermore, ex-vivo labeling agents, such as iron-oxide nanoparticles, have been employed to track and localize the transplanted stem cells. However, this method does not monitor a fundamental cellular biology property regarding the viability of transplanted cells. It has been known that manganese chloride (MnCl2) enters the cells via voltage-gated calcium (Ca2+) channels when the cells are biologically active, and accumulates intracellularly to generate T1 shortening effect. Therefore, we suggest that manganese-guided MRI can be useful to monitor cell viability after the transplantation of hESC into the myocardium.
In this video, we will show how to label hESC with MnCl2 and how those cells can be clearly seen by using MRI in vitro. At the same time, biological activity of Ca2+-channels will be modulated utilizing both Ca2+-channel agonist and antagonist to evaluate concomitant signal changes.

In this video, we are showing how to label human embryonic stem cells (hESC) with manganese chloride (MnCl2) which can enter cells via voltage-gated calcium channels when the cells are biologically active. Additionally, we show the use of MnCl2 as cellular MRI contrast agent to determine the in vitro viability of hESC.

Human embryonic stem cells (hESC) have demonstrated the ability to restore the injured myocardium. Magnetic resonance imaging (MRI) has emerged as one of ...

Preparation of embryos for Electron Microscopy of the Drosophila embryonic heart tube

The morphogenesis of the Drosophila embryonic heart tube has emerged as a valuable model system for studying cell migration, cell-cell adhesion and cell shape changes during embryonic development. One of the challenges faced in studying this structure is that the lumen of the heart tube, as well as the membrane features that are crucial to heart tube formation, are difficult to visualize in whole mount embryos, due to the small size of the heart tube and intra-lumenal space relative to the embryo. The use of transmission electron microscopy allows for higher magnification of these structures and gives the advantage of examining the embryos in cross section, which easily reveals the size and shape of the lumen. In this video, we detail the process for reliable fixation, embedding, and sectioning of late stage Drosophila embryos in order to visualize the heart tube lumen as well as important cellular structures including cell-cell junctions and the basement membrane.

Preparation of embryos for Electron Microscopy of the Drosophila embryonic heart tube

We describe a process for fixation, embedding, sectioning, and imaging of late stage Drosophila embryos for Trasmission Electron Microscopy of the embryonic heart tube. This technique allows for the visualization of the heart tube lumen as well as the basement membrane, which lines the lumen of the heart.

The morphogenesis of the Drosophila  embryonic heart tube has emerged as a valuable model system for studying cell migration, cell-cell adhesion and cell ...

Isolation and Derivation of Mouse Embryonic Germinal Cells

The ability of embryonic germinal cells (EG) to differentiate into primordial germinal cells (PGCs) and later into gametes during early developmental stages is a perfect model to address our hypothesis about cancer and infertility. This protocol shows how to isolate primordial germinal cells from developing gonads in 10.5-11.5 days post coitum (dpc) mouse embryos.  Developing gonadal ridges from mouse embryos (C57BL6J) were dissociated by mechanical disruption with collagenase, then plated in a mouse embryo fibroblast feeder layer (MEF-CF1) that was previously mitotically inactivated with mitomycin C in the presence of knockout media and supplemented with Leukemia Inhibitor Factor (LIF), basic Fibroblast Growth Factor (bFGF), and Stem Cell Factor (SCF).  Using these optimized methods for PCG identification, isolation, and establishment of culture conditions permits long term cultures of EG cells for more than 40 days.  The embryonic germinal cell lines showed embryonic phenotype and expression of common used markers of the pluripotent state.  Isolation and derivation of germinal cells in culture provide a tool to understand their development in vitro and offer the opportunity to monitor cumulative damage at genetic and epigenetic levels after exposure to oxidative stress.

The ability of embryonic germinal cells to differentiate into primordial germinal cells during early development stages is a perfect model to address our hypothesis about cancer and infertility. This protocol shows how to isolate primordial germinal cells from developing gonads in 10.5-11.5 days post coitum mouse embryos.

The ability of embryonic germinal cells (EG) to differentiate into primordial germinal cells (PGCs) and later into gametes during early developmental ...

Retro-orbital Injection in Adult Zebrafish

Drug treatment of whole animals is an essential tool in any model system for pharmacological and chemical genetic studies. Intravenous (IV) injection is often the most effective and noninvasive form of delivery of an agent of interest. In the zebrafish (Danio rerio), IV injection of drugs has long been a challenge because of the small vessel diameter. This has also proved a significant hurdle for the injection of cells during hematopoeitic stem cell transplantation. Historically, injections into the bloodstream were done directly through the heart. However, this intra-cardiac procedure has a very high mortality rate as the heart is often punctured during injection leaving the fish prone to infection, massive blood loss or fatal organ damage. Drawing on our experience with the mouse, we have developed a new injection procedure in the zebrafish in which the injection site is behind the eye and into the retro-orbital venous sinus. This retro-orbital (RO) injection technique has been successfully employed in both the injection of drugs in the adult fish as well as transplantation of whole kidney marrow cells. RO injection has a much lower mortality rate than traditional intra-cardiac injection. Fish that are injected retro-orbitally tend to bleed less following injection and are at a much lower risk of injury to a major organ like the heart. Further, when performed properly, injected cells and/or drugs quickly enter the bloodstream allowing compounds to exert their effect on the whole fish and kidney cells to easily home to their niche. Thus, this new injection technique minimizes mortality while allowing efficient delivery of material into the bloodstream of adult fish. Here we exemplify this technique by retro-orbital injection of Tg(globin:GFP) cells into adult casper fish as well as injection of a red fluorescent dye (dextran, Texas Red ) into adult casper fish. We then visualize successful injections by whole animal fluorescence microscopy.

Here we show how to do retro-orbital injection in adult zebrafish.

Drug treatment of whole animals is an essential tool in any model system for pharmacological and chemical genetic studies. Intravenous (IV) injection is ...

Single-cell Suction Recordings from Mouse Cone Photoreceptors

Rod and cone photoreceptors in the retina are responsible for light detection. In darkness, cyclic nucleotide-gated (CNG) channels in the outer segment are open and allow cations to flow steadily inwards across the membrane, depolarizing the cell. Light exposure triggers the closure of the CNG channels, blocks the inward cation current flow, and thus results in cell hyperpolarization. Based on the polarity of photoreceptors, a suction recording method was developed in 1970s that, unlike the classic patch-clamp technique, does not require penetrating the plasma membrane 1. Drawing the outer segment into a tightly-fitting glass pipette filled with extracellular solution allows recording the current changes in individual cells upon test-flash exposure. However, this well-established "outer-segment-in (OS-in)" suction recording is not suitable for mouse cone recordings, because of the low percentage of cones in the mouse retina (3%) and the difficulties in identifying the cone outer segments. Recently, an inner-segment-in (IS-in) recording configuration was developed to draw the inner segment/nuclear region of the photoreceptor into the recording pipette 2,3. In this video, we will show how to record from individual mouse cone photoresponses using single-cell suction electrode.

We will show how to record flash responses from single mouse cones using a suction electrode.

Rod and cone photoreceptors in the retina are responsible for light detection. In darkness, cyclic nucleotide-gated (CNG) channels in the outer segment ...

Video Bioinformatics Analysis of Human Embryonic Stem Cell Colony Growth

Because video data are complex and are comprised of many images, mining information from video material is difficult to do without the aid of computer software.  Video bioinformatics is a powerful quantitative approach for extracting spatio-temporal data from video images using computer software to perform dating mining and analysis. In this article, we introduce a video bioinformatics method for quantifying the growth of human embryonic stem cells (hESC) by analyzing time-lapse videos collected in a Nikon BioStation CT incubator equipped with a camera for video imaging. In our experiments, hESC colonies that were attached to Matrigel were filmed for 48 hours in the BioStation CT.  To determine the rate of growth of these colonies, recipes were developed using CL-Quant software which enables users to extract various types of data from video images.  To accurately evaluate colony growth, three recipes were created. The first segmented the image into the colony and background, the second enhanced the image to define colonies throughout the video sequence accurately, and the third measured the number of pixels in the colony over time.  The three recipes were run in sequence on video data collected in a BioStation CT to analyze the rate of growth of individual hESC colonies over 48 hours. To verify the truthfulness of the CL-Quant recipes, the same data were analyzed manually using Adobe Photoshop software. When the data obtained using the CL-Quant recipes and Photoshop were compared, results were virtually identical, indicating the CL-Quant recipes were truthful. The method described here could be applied to any video data to measure growth rates of hESC or other cells that grow in colonies. In addition, other video bioinformatics recipes can be developed in the future for other cell processes such as migration, apoptosis, and cell adhesion.  

Video bioinformatics is the automated processing, analysis, understanding, and data mining of biological spatio-temporal data extracted from microscopic videos. The purpose of this article is to demonstrate a method for measuring human embryonic stem cell colony growth using a video bioinformatics method.

Because video data are complex and are comprised of many images, mining information from video material is difficult to do without the aid of computer ...

In vivo Imaging and Therapeutic Treatments in an Orthotopic Mouse Model of Ovarian Cancer

Human cancer and response to therapy is better represented in orthotopic animal models. This paper describes the development of an orthotopic mouse model of ovarian cancer, treatment of cancer via oral delivery of drugs, and monitoring of tumor cell behavior in response to drug treatment in real time using in vivo imaging system. In this orthotopic model, ovarian tumor cells expressing luciferase are applied topically by injecting them directly into the mouse bursa where each ovary is enclosed. Upon injection of D-luciferin, a substrate of firefly luciferase, luciferase-expressing cells generate bioluminescence signals. This signal is detected by the in vivo imaging system and allows for a non-invasive means of monitoring tumor growth, distribution, and regression in individual animals. Drug administration via oral gavage allows for a maximum dosing volume of 10 mL/kg body weight to be delivered directly to the stomach and closely resembles delivery of drugs in clinical treatments. Therefore, techniques described here, development of an orthotopic mouse model of ovarian cancer, oral delivery of drugs, and in vivo imaging, are useful for better understanding of human ovarian cancer and treatment and will improve targeting this disease.

In vivo Imaging and Therapeutic Treatments in an Orthotopic Mouse Model of Ovarian Cancer

Orthotopic animal models of ovarian cancer replicate better human disease and therefore enhance our understanding of cancer progression and tumor response to therapy. A mouse model receives an intrabursal injection of luciferase-expressing ovarian tumor cells. Treatment is administered via oral gavage. Tumor growth is monitored by in vivo imaging system.

Human cancer and response to therapy is better represented in orthotopic animal models.  This paper describes the development of an orthotopic mouse model ...

Separation of Mouse Embryonic Facial Ectoderm and Mesenchyme

Orofacial clefts are the most frequent craniofacial defects, which affect 1.5 in 1,000 newborns worldwide1,2. Orofacial clefting is caused by abnormal facial development3. In human and mouse, initial growth and patterning of the face relies on several small buds of tissue, the facial prominences4,5. The face is derived from six main prominences: paired frontal nasal processes (FNP), maxillary prominences (MxP) and mandibular prominences (MdP). These prominences consist of swellings of mesenchyme that are encased in an overlying epithelium. Studies in multiple species have shown that signaling crosstalk between facial ectoderm and mesenchyme is critical for shaping the face6. Yet, mechanistic details concerning the genes involved in these signaling relays are lacking. One way to gain a comprehensive understanding of gene expression, transcription factor binding, and chromatin marks associated with the developing facial ectoderm and mesenchyme is to isolate and characterize the separated tissue compartments.
Here we present a method for separating facial ectoderm and mesenchyme at embryonic day (E) 10.5, a critical developmental stage in mouse facial formation that precedes fusion of the prominences. Our method is adapted from the approach we have previously used for dissecting facial prominences7. In this earlier study we had employed inbred C57BL/6 mice as this strain has become a standard for genetics, genomics and facial morphology8. Here, though, due to the more limited quantities of tissue available, we have utilized the outbred CD-1 strain that is cheaper to purchase, more robust for husbandry, and tending to produce more embryos (12-18) per litter than any inbred mouse strain8. Following embryo isolation, neutral protease Dispase II was used to treat the whole embryo. Then, the facial prominences were dissected out, and the facial ectoderm was separated from the mesenchyme. This method keeps both the facial ectoderm and mesenchyme intact. The samples obtained using this methodology can be used for techniques including protein detection, chromatin immunoprecipitation (ChIP) assay, microarray studies, and RNA-seq.

A protocol for separation of embryo facial ectoderm and mesenchyme is described. We use Dispase II to treat whole embryos first, dissect whole facial prominences out, and then separate the facial ectoderm and mesenchyme.

 Orofacial clefts are the most frequent  craniofacial defects, which affect 1.5 in 1,000 newborns worldwide1,2. Orofacial clefting is caused by abnormal ...