The authors thank Adeline Dolly for the pictures of explant on fibronectin, Eric Theveneau for helpful discussions and the Animal Facility of the Institut Curie. C.M. is a postdoctoral fellow of Region Ile de France (Domaine d'Interet Majeur Stem Pole), Universite Paris Sud (Attache Temporaire d'Enseignement et de Recherche), and Agence Nationale de la Recherche. This work was funded by the Universite Paris Sud (Attractivite 2011), the Centre National de la Recherche Scientifique (Action Thematique et Incitative sur Programme), Association pour la Recherche contre le Cancer Grant SFI20101201882, Ligue contre le Cancer, and Agence Nationale de la Recherche (Agence Nationale de la Recherche Programme Blanc).

Experiments comply with National and European regulation on the protection of animals used for scientific purposes and with internationally established principles of replacement, reduction and refinement.
1. Preparation of Fibronectin-coated Dishes14
<ol>
	<li>Pipette 500 ml of 10 mg/ml culture grade fibronectin diluted in 1x&#160;Phosphate Buffered Saline (PBS) into a standard plastic Petri dish (&#216; 40 x 11 mm). Incubate at 37 &#176;C for 1 hr. Note: if using glass dishes or glass coverslips for subsequent imaging, use a 100 mg/ml fibronectin solution.</li>
	<li>Rinse three times with 1x&#160;PBS.</li>
	<li>Replace PBS with 500 ml of 1x&#160;PBS/0.1% Bovine Serum Albumin (BSA). Incubate at 37 &#176;C for 30 min.</li>
	<li>Rinse three times with 1x&#160;PBS.</li>
	<li>Fill up with 1x&#160;PBS and keep at 4 &#176;C until use (usually for 24-48 hr).</li>
</ol>
2. Dissection of the NC Explants
<ol>
	<li>Prepare 3/4 Normal Amphibian Medium (NAM) (110 mM NaCl, 2 mM KCl, 1 mM Ca(NO3)2, 1 mM MgSO4, 0.1 mM EDTA, 1 mM NaHCO3, 0.2x&#160;PBS, 50 mg/ml gentamycin10,15). Do not keep more than 1 week for dissection, store at 4 &#176;C. Older NAM can be used for preparing agarose-coated dissection dishes (below).</li>
	<li>Prepare 60 mm Petri dishes for dissection, coated with 10 ml of 2% agarose in 3/4 NAM.</li>
	<li>Collect dissection tools: plastic Pasteur pipettes, a finest insect pin mounted on pin holder (see materials table for reference), an &#34;eyebrow knife&#34; (made with eyebrow hair embedded in paraffin at the tip of a glass Pasteur pipette16), two fine dissection forceps, P1000 pipette and tips, a binocular stereoscope with magnification 8-40X to 50, a bright light source with optic fibers guides. All dissecting tools should be kept clean; after each experiment, rinse them twice with distilled water, once with 100% ethanol and let dry. Store away from dust.</li>
	<li>Fill in the dissection dish with fresh NAM almost to the top.</li>
	<li>Obtain X. laevis embryos according to standard procedures10 and age them until they reach neurula stage 16 (according to Nieuwkoop and Faber developmental table17).</li>
	<li>Place stage 16 embryos into the dissection dish using the plastic Pasteur pipette.</li>
	<li>Carry out all subsequent steps under the binocular scope. Remove the vitelline membrane with two pairs of forceps. Be careful not to damage the dorsal part of the embryos.</li>
	<li>Wait until the embryos have reached stage 17 to start the dissection. Stage 17 is appropriate since the neural crest is clearly set apart from the neural tube, in contrast to earlier stages. After stage 17, NC starts migrating and intermingling with the surrounding mesenchyme.</li>
	<li>Dig a small hole in the agarose with forceps to make a niche for the embryos in order to maintain them during the dissection. Place one embryo dorsal side up. Note: modeling clay can be used to maintain the embryos instead digging a hole into the agarose.</li>
	<li>Make an incision in the lateral part of the anterior neural fold with the eyebrow knife and the insect pin. Be careful not to go too deep into the embryo: aim to cut through 2-3 cell layers (never reach as deep as the archenteron!). During the whole dissection process, never allow the dissected tissues to enter in contact with the air-liquid interface since X. laevis embryonic tissues are lysed by surface tension.</li>
	<li>Make a second parallel incision in the more dorsal part of the neural fold using the same instruments.</li>
	<li>If needed, turn the dish around 90&#176;. Make a third perpendicular incision with the eyebrow knife and the insect pin, at the posterior side of the first two incisions. The NC is a thick mass of cells underneath the pigmented outer layer of the ectoderm, lateral to the neural tube.</li>
	<li>Use the tip of the eyebrow knife to detach the pigmented ectoderm layer from the underlying NC, starting from the third incision edge.</li>
	<li>Use the side of the eyebrow knife to detach the NC tissue starting from the third incision. The NC tissue is rather greyish, while the underlying cephalic mesoderm is white. Carefully separate the NC from the mesoderm.</li>
	<li>Detach the NC tissue anteriorly from the optic vesicle, and cut at this level to free the explant. As a control for first experiments, checking snail2 expression (a canonical NC marker) in some explants by in situ hybridization is recommended.</li>
</ol>
3. Plating Explants on Fibronectin
<ol>
	<li>Fill-in the fibronectin-coated dish with Modified Danilchick Medium (MDM, NaCl 53 mM, Na2CO3 5 mM, K Gluconate 4.5 mM, Na Gluconate 32 mM, MgSO4 1 mM, CaCl2 1 mM, BSA 0.1 %, adjust pH to 8.3 with 1 M Bicine18).</li>
	<li>Transfer the explants into the fibronectin-coated dish using a P1000 pipette. Never allow the explants to touch the air-liquid interface. First, pipette some liquid into the tip, then the explants, then some liquid again. Do not allow any air into the tip while transferring the explants into the fibronectin-coated dish. Once the tip is inside the liquid of the fibronectin-coated dish, let the explants slowly go down by gravity, or push very gently. Avoid ejecting the explants too fast.</li>
	<li>Place 10-30 explants in the dish using the eyebrow knife. Avoid the sides of the dish, which are not adequate for subsequent imaging.</li>
	<li>Try not to move the dish until the explants have attached on the fibronectin (it takes about 15-30 min). If needed, move the dish very carefully.</li>
	<li>Place the dish in a refrigerated incubator (between 15-20 &#176;C, for temperature chart see17). When placed at 15 &#176;C, cells are usually migrating efficiently and scattering after 6 hr of incubation (this timing may vary between experiments).</li>
</ol>
4. Grafting Explants into Host Embryos
<ol>
	<li>Cut a fine glass coverslip into very small pieces using coarse forceps. The size of the pieces should be approximately 1.5 mm2. Immerse the pieces into a Petri dish containing 3/4 NAM or PBS using forceps.</li>
	<li>Preparation of the host embryo: dissect out the host NC in 3/4 NAM as described in 3) with special care not to damage the host embryo while removing the vitelline membrane and dissecting the NC. The tissue tension tends to increase the size of the ablation: let the host embryo heal partially while dissecting the donor embryo.</li>
	<li>In another agarose-coated dish or in another part of the same dish, dissect out the NC explant from the donor embryo as described in Protocol&#160;3. Transfer the NC graft into the dish containing the host with care, as described in Protocol&#160;3.</li>
	<li>Immediately place the NC explant onto the host ablated area using forceps. The explant should attach partially. Put a piece of glass coverslip onto the grafted embryo to maintain the graft in place. Choose a piece of glass bigger than the embryo to avoid damaging it. The embryo will be a little bit flattened.</li>
	<li>Wait for at least 15-20 min, then gently remove the coverslip. Let the embryo recover for another 10 min and carefully pipette it into a clean dish filled with 3/4 NAM, using the plastic Pasteur pipette.</li>
</ol>

<ol>
	<li>Sauka-Spengler, T., Bronner-Fraser, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+gene+regulatory+network+orchestrates+neural+crest+formation.">A gene regulatory network orchestrates neural crest formation.</a> Nat. Rev. Mol. Cell Biol. 9 (7), 557-568 (2008).</li><li>Theveneau, E., Mayor, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+crest+delamination+and+migration:+from+epithelium-to-mesenchyme+transition+to+collective+cell+migration.">Neural crest delamination and migration: from epithelium-to-mesenchyme transition to collective cell migration.</a> Dev. Biol. 366 (1), 34-54 (2012).</li><li>Stuhlmiller, T. J., Garc&#237;a-Castro, M. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+perspectives+of+the+signaling+pathways+directing+neural+crest+induction.">Current perspectives of the signaling pathways directing neural crest induction.</a> Cell. Mol. Life Sci. 69 (22), 3715-3737 (2012).</li><li>Milet, C., Monsoro-Burq, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+crest+induction+at+the+neural+plate+border+in+vertebrates.">Neural crest induction at the neural plate border in vertebrates.</a> Dev. Biol. 366 (1), 22-33 (2012).</li><li>Pegoraro, C., Monsoro-Burq, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Signaling+and+transcriptional+regulation+in+neural+crest+specification+and+migration:+lessons+from+Xenopus+embryos.">Signaling and transcriptional regulation in neural crest specification and migration: lessons from Xenopus embryos.</a> Dev. Biol. 2 (2), 247-259 (2013).</li><li>Etchevers, H. C., Amiel, J., Lyonnet, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+Bases+of+Human+Neurocristopathies.">Molecular Bases of Human Neurocristopathies.</a> Neural Crest Induct. Different. 589, 213-234 (2005).</li><li>Nieuwkoop, P. D., 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=Activation+and+organization+of+the+central+nervous+system+in+amphibians.+Part+II.+Differentiation+and+organization.">Activation and organization of the central nervous system in amphibians. Part II. Differentiation and organization.</a> J. Exp. Zool. 120 (1), 33-81 (1952).</li><li>Nieuwkoop, P. D., 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=Activation+and+organization+of+the+central+nervous+system+in+amphibians+Part+I.+Induction+and+activation.">Activation and organization of the central nervous system in amphibians Part I. Induction and activation.</a> J. Exp. Zool. 120 (1), 1-31 (1952).</li><li>Sharpe, C. R., Fritz, A., De Robertis, E. M., Gurdon, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+homeobox-containing+marker+of+posterior+neural+differentiation+shows+the+importance+of+predetermination+in+neural+induction.">A homeobox-containing marker of posterior neural differentiation shows the importance of predetermination in neural induction.</a> Cell. 50 (5), 749-758 (1987).</li><li>Sive, H. L., Grainger, R. M., Harland, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Early development of Xenopus laevis: a laboratory manual. , (2000).</li><li>Monsoro-Burq, A. -. H., Fletcher, R. B., Harland, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+crest+induction+by+paraxial+mesoderm+in+Xenopus+embryos+requires+FGF+signals.">Neural crest induction by paraxial mesoderm in Xenopus embryos requires FGF signals.</a> Development. 130 (14), 3111-3124 (2003).</li><li>Milet, C., Maczkowiak, F., Roche, D. D., Monsoro-Burq, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pax3+and+Zic1+drive+induction+and+differentiation+of+multipotent,+migratory,+and+functional+neural+crest+in+Xenopus+embryos.">Pax3 and Zic1 drive induction and differentiation of multipotent, migratory, and functional neural crest in Xenopus embryos.</a> Proc. Natl. Acad. Sci. U.S.A. 110 (14), 5528-5533 (2013).</li><li>Sadaghiani, B., Thi&#233;baud, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+crest+development+in+the+Xenopus+laevis+embryo,+studied+by+interspecific+transplantation+and+scanning+electron+microscopy.">Neural crest development in the Xenopus laevis embryo, studied by interspecific transplantation and scanning electron microscopy.</a> Dev. Biol. 124 (1), 91-110 (1987).</li><li>Theveneau, E., 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=Collective+chemotaxis+requires+contact-dependent+cell+polarity.">Collective chemotaxis requires contact-dependent cell polarity.</a> Dev. Cell. 19 (1), 39-53 (2010).</li><li>Slack, J. M., Forman, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+interaction+between+dorsal+and+ventral+regions+of+the+marginal+zone+in+early+amphibian+embryos.">An interaction between dorsal and ventral regions of the marginal zone in early amphibian embryos.</a> J. Embryol. Exp. Morphol. 56, 283-299 (1980).</li><li>Sive, H. L., Grainger, R. M., Harland, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Embryo+dissection+and+micromanipulation+tools.">Embryo dissection and micromanipulation tools.</a> CSH Protoc. , (2007).</li><li>Nieuwkoop, P. D., Faber, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Normal+table+of+Xenopus+laevis+(Daudin):+a+systematical+and+chronological+survey+of+the+development+from+the+fertilized+egg+till+the+end+of+metamorphosis.">Normal table of Xenopus laevis (Daudin): a systematical and chronological survey of the development from the fertilized egg till the end of metamorphosis.</a> , (1994).</li><li>Theveneau, E., Mayor, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Beads+on+the+run:+beads+as+alternative+tools+for+chemotaxis+assays.">Beads on the run: beads as alternative tools for chemotaxis assays.</a> Methods Mol. Biol. 769, 449-460 (2011).</li><li>Bronner, M. E., LeDouarin, N. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+evolution+of+the+neural+crest:+An+overview.">Development and evolution of the neural crest: An overview.</a> Dev. Biol. 366 (1), 2-9 (2012).</li><li>Alfandari, D., Cousin, H., Gaultier, A., Hoffstrom, B. G., DeSimone, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrin+&#945;5&#946;1+supports+the+migration+of+Xenopus+cranial+neural+crest+on+fibronectin.">Integrin &#945;5&#946;1 supports the migration of Xenopus cranial neural crest on fibronectin.</a> Dev. Biol. 260 (2), 449-464 (2003).</li><li>Fort, P., 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=Activity+of+the+RhoU/Wrch1+GTPase+is+critical+for+cranial+neural+crest+cell+migration.">Activity of the RhoU/Wrch1 GTPase is critical for cranial neural crest cell migration.</a> Dev. Biol. 350 (2), 451-463 (2011).</li><li>Matthews, H. 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=Directional+migration+of+neural+crest+cells+in+vivo+is+regulated+by+Syndecan-4/Rac1+and+non-canonical+Wnt+signaling/RhoA.">Directional migration of neural crest cells in vivo is regulated by Syndecan-4/Rac1 and non-canonical Wnt signaling/RhoA.</a> Development. 135 (10), 1771-1780 (2008).</li><li>Kashef, J., K&#246;hler, A., Kuriyama, S., Alfandari, D., Mayor, R., Wedlich, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cadherin-11+regulates+protrusive+activity+in+Xenopus+cranial+neural+crest+cells+upstream+of+Trio+and+the+small+GTPases.">Cadherin-11 regulates protrusive activity in Xenopus cranial neural crest cells upstream of Trio and the small GTPases.</a> Genes Dev. 23 (12), 1393-1398 (2009).</li><li>Hwang, Y. -. S., Luo, T., Xu, Y., Sargent, T. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myosin-X+is+required+for+cranial+neural+crest+cell+migration+in+Xenopus+laevis.">Myosin-X is required for cranial neural crest cell migration in Xenopus laevis.</a> Dev. Dyn. 238 (10), 2522-2529 (2009).</li><li>Lee, G., 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=Modelling+pathogenesis+and+treatment+of+familial+dysautonomia+using+patient-specific+iPSCs.">Modelling pathogenesis and treatment of familial dysautonomia using patient-specific iPSCs.</a> Nature. 461 (7262), 402-406 (2009).</li><li>Mica, Y., Lee, G., Chambers, S. M., Tomishima, M. J., Studer, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+Neural+Crest+Induction,+Melanocyte+Specification,+and+Disease-Related+Pigmentation+Defects+in+hESCs+and+Patient-Specific+iPSCs..">Modeling Neural Crest Induction, Melanocyte Specification, and Disease-Related Pigmentation Defects in hESCs and Patient-Specific iPSCs..</a> Cell Reports. 3 (4), 1140-1152 (2013).</li><li>Shnitsar, I., Borchers, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PTK7+recruits+dsh+to+regulate+neural+crest+migration.">PTK7 recruits dsh to regulate neural crest migration.</a> Development. 135 (24), 4015-4024 (2008).</li><li>Matthews, H. 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=Directional+migration+of+neural+crest+cells+in+vivo+is+regulated+by+Syndecan-4/Rac1+and+non-canonical+Wnt+signaling/RhoA.">Directional migration of neural crest cells in vivo is regulated by Syndecan-4/Rac1 and non-canonical Wnt signaling/RhoA.</a> Development. 135 (10), 1771-1780 (2008).</li><li>Matthews, H. K., Broders-Bondon, F., Thiery, J. P., Mayor, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wnt11r+is+required+for+cranial+neural+crest+migration.">Wnt11r is required for cranial neural crest migration.</a> Dev. Dyn. 237 (11), 3404-3409 (2008).</li><li>Carmona-Fontaine, C., 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=Contact+inhibition+of+locomotion+in+vivo+controls+neural+crest+directional+migration.">Contact inhibition of locomotion in vivo controls neural crest directional migration.</a> Nature. 456 (7224), 957-961 (2008).</li><li>Guiral, E. C., Faas, L., Pownall, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+crest+migration+requires+the+activity+of+the+extracellular+sulphatases+XtSulf1+and+XtSulf2.">Neural crest migration requires the activity of the extracellular sulphatases XtSulf1 and XtSulf2.</a> Dev. Biol. 341 (2), 375-388 (2010).</li><li>Cousin, H., Abbruzzese, G., Kerdavid, E., Gaultier, A., Alfandari, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translocation+of+the+Cytoplasmic+Domain+of+ADAM13+to+the+Nucleus+Is+Essential+for+Calpain8-a+Expression+and+Cranial+Neural+Crest+Cell+Migration.">Translocation of the Cytoplasmic Domain of ADAM13 to the Nucleus Is Essential for Calpain8-a Expression and Cranial Neural Crest Cell Migration.</a> Dev. Cell. 20 (2), 256-263 (2011).</li><li>Borchers, A., David, R., Wedlich, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Xenopus+cadherin-11+restrains+cranial+neural+crest+migration+and+influences+neural+crest+specification.">Xenopus cadherin-11 restrains cranial neural crest migration and influences neural crest specification.</a> Development. 128 (16), 3049-3060 (2001).</li><li>Borchers, A., Epperlein, H. -. H., Wedlich, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+assay+system+to+study+migratory+behavior+of+cranial+neural+crest+cells+in+Xenopus.">An assay system to study migratory behavior of cranial neural crest cells in Xenopus.</a> Dev. Genes Evol. 210 (4), 217-222 (2000).</li><li>Kerney, R., Gross, J. B., Hanken, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Runx2+is+essential+for+larval+hyobranchial+cartilage+formation+in+Xenopus+laevis.">Runx2 is essential for larval hyobranchial cartilage formation in Xenopus laevis.</a> Dev. Dyn. 236 (6), 1650-1662 (2007).</li><li>Yan, C. Y. I., Skourides, P., Chang, C., Samba Brivanlou, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=a+Xenopus+hnRNP+expressed+in+neural+and+neural+crest+tissues.">a Xenopus hnRNP expressed in neural and neural crest tissues.</a> Dev. Dyn. 238 (1), 204-209 (2009).</li><li>Acloque, H., Adams, M. S., Fishwick, K., Bronner-Fraser, M., Nieto, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epithelial-mesenchymal+transitions:+the+importance+of+changing+cell+state+in+development+and+disease.">Epithelial-mesenchymal transitions: the importance of changing cell state in development and disease.</a> J. Clin. Invest. 119 (6), 1438-1449 (2009).</li></ol>

The authors have nothing to disclose.

This protocol describes an easy technique to explant premigratory cranial NC in X. laevis embryos. The embryos used for such experiments need to be robust and heal well. Discard any batch of unhealthy embryos. In addition, grow embryos at various temperatures (from 12 to 18-20 &#176;C), in order to excise neural crest at stage 17 and not later. After stage 17, neural crest may be mixed with cephalic mesoderm and cannot be removed completely. Xenopus tissues heal quickly and then loose their adh...

The neural crest (NC) is a transient embryonic cell population that emerges from the neural tube at the end of neurulation in vertebrate embryos. The signaling and genetic events that control NC specification start as early as gastrulation. The NC is specified at the border between the neural and non-neural ectoderm by signals from surrounding dorsal tissues. At the end of neurulation, NC cells undergo an epithelium-to-mesenchyme transition (EMT) and migrate extensively in the embryo following stereotyped routes&#160;by responding to surrounding guiding cues. Once they have reached their final destination, they differentiate into a vast array of derivatives, e.g. neurons, glia, bone, cartilage, and pigmented cells1-5. Because of their contribution to many cell types and embryonic tissues, defects at any step of NC cells development, from induction to final differentiation, can cause congenital syndromes named neurocristopathies6. Experimental manipulation of the developing NC at different stages - specification, EMT, migration, and differentiation - will improve our understanding of neurocristopathies and allow design of potential therapeutic strategies.
The Xenopus laevis embryo is a model of choice to study NC development. Large numbers of embryos are easy to obtain, and external fertilization gives access to the very first steps of development. Many tools are available to experimentally manipulate X. laevis embryonic development. Gene gain-of-function and knockdown are easy to perform by microinjecting individual cells of early blastulas. Embryonic tissues can be cut for in vitro reassociation 7-11 or back-grafting assays12,13.
In this protocol, we describe how to dissect out premigratory cranial NC in X. laevis late neurulas, prior to migration. These explants can be cultured on fibronectin-coated plates to study migration and differentiation in controlled in vitro experimental conditions. NC explants can also be grafted into normal or manipulated host embryos to study their migration and differentiation in vivo.

<table border="0" cellpadding="0" cellspacing="0" width="601">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:244px;">Fibronectin from bovine plasma</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">F4759-1MG</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:244px;">Bovine Serum Albumine. Fraction V</td>
			<td style="width:71px;">Euromedex</td>
			<td style="width:119px;">04-100-811-C</td>
			<td>Lower quality grade may&#160; be suitable for this application</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:244px;">Stainless Steel Insect Pins. Size 000</td>
			<td style="width:71px;">FST</td>
			<td align="right" style="width:119px;">26001</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:244px;">Dumont #5 forceps 0.05 mm x 0.02 mm</td>
			<td style="width:71px;">FST</td>
			<td style="width:119px;">11252-20</td>
			<td></td>
		</tr>
	</tbody>
</table>

dissection of xenopus laevis neural crest for in vitro explant culture or in vivo transplantation

The neural crest (NC) is a transient dorsal neural tube cell population that undergoes an epithelium-to-mesenchyme transition (EMT) at the end of neurulation, migrates extensively towards various organs, and differentiates into many types of derivatives (neurons, glia, cartilage and bone, pigmented and endocrine cells). In this protocol, we describe how to dissect the premigratory cranial NC from Xenopus laevis embryos, in order to study NC development in vivo and in vitro. The frog model offers many advantages to study early development; abundant batches are available, embryos develop rapidly, in vivo gain and loss of function strategies allow manipulation of gene expression prior to NC dissection in donor and/or host embryos. The NC explants can be plated on fibronectin and used for in vitro studies. They can be cultured for several days in a serum-free defined medium. We also describe how to graft NC explants back into host embryos for studying NC migration and differentiation in vivo.

When plated on fibronectin, the neural crest explants attach rapidly (15-30 min) and the explant spreads flat within 2 hr (Figure 1A). After 3-6 hr cells start to scatter. At 24 hr at 15 &#176;C, many cells have started to migrate away from the explant (Figures 1B and 1C). Yolk makes cells very bright under phase contrast (Figure 1B). Cell protrusions (filopodes and lamellipodes) are clearly visible after phalloidin staining of the actin cytoskeleton (<s...

Watch this Scientific Journal Video about Dissection of Xenopus laevis Neural Crest for in vitro Explant Culture or in vivo Transplantation at JoVE.com

Dissection of Xenopus laevis Neural Crest for in vitro Explant Culture or in vivo Transplantation

This protocol describes how to dissect premigratory cranial neural crest (NC) from Xenopus laevis neurulas. These explants can be plated on fibronectin and cultured in vitro, or grafted back into host embryos. This technique allows studying the mechanisms of NC epithelium-to-mesenchyme transition, migration, and differentiation.

Dissection of Xenopus laevis Neural Crest for in vitro Explant Culture or in vivo Transplantation

The neural crest (NC) is a transient dorsal neural tube cell population that undergoes an epithelium-to-mesenchyme transition (EMT) at the end of ...

dissection-xenopus-laevis-neural-crest-for-vitro-explant-culture-or

Research

JoVE Journal

Biology

13.1K Views.  Centre Universitaire. This protocol describes how to dissect premigratory cranial neural crest (NC) from Xenopus laevis neurulas. These explants can be plated on fibronectin and cultured in vitro, or grafted back into host embryos. This technique allows studying the mechanisms of NC epithelium-to-mesenchyme transition, migration, and differentiation.

Video: Dissection of Xenopus laevis Neural Crest for in vitro Explant Culture or in vivo Transplantation

Dissection of Organizer and Animal Pole Explants from Xenopus laevis Embryos and Assembly of a Cell Adhesion Assay

This video demonstrates the technique used for preparation of organizer and animal pole explants from Xenopus laevis embryos, including the use of the eyebrow knife - a specialized dissection tool made of one's eyebrow. The protocol for assembling an adhesion assay is also given, which probes for the presence of key adhesion molecules present on the surface organizer or animal pole cells that are critical for proper development.

Plastic Embedding and Sectioning of Xenopus laevis Embryos

Plastic sections maintain true tissue morphology in thin sections of tissue that can be immunostained with fluorescent secondary antibodies, making this method more useful than paraffin-embedded or frozen sections for many types of tissue. The method for staining, plastic embedding, and sectioning is demonstrated in this video.

Obtaining Eggs from Xenopus laevis Females

The eggs of Xenopus laevis intact, lysed, and/or fractionated are useful for a wide variety of experiments. This protocol shows how to induce egg laying, collect and dejelly the eggs, and sort the eggs to remove any damaged eggs.

The eggs of Xenopus laevis intact, lysed, and/or fractionated are useful for a wide variety of experiments. This protocol shows how to induce egg laying, collect and dejelly the eggs, and sort the eggs to remove any damaged eggs.

The eggs of Xenopus laevis intact, lysed, and/or fractionated are useful for a wide variety of experiments. This protocol shows how to induce egg laying, ...

Preparation and Fractionation of Xenopus laevis Egg Extracts

Crude and fractionated Xenopus egg extracts can be used to provide ingredients for reconstituting cellular processes for morphological and biochemical analysis. Egg lysis and differential centrifugation are used to prepare the crude extract which in turn in used to prepare fractionated extracts and light membrane preparations.

Crude and fractionated Xenopus egg extracts can be used to provide ingredients for reconstituting cellular processes for morphological and biochemical analysis. Egg lysis and differential centrifugation are used to prepare the crude extract which in turn in used to prepare fractionated extracts and light membrane preparations.

Crude and fractionated Xenopus egg extracts can be used to provide ingredients for reconstituting cellular processes for morphological and biochemical ...

Microinjection of Xenopus Laevis Oocytes

Microinjection of Xenopus laevis oocytes followed by thin-sectioning electron microscopy (EM) is an excellent system for studying nucleocytoplasmic transport. Because of its large nucleus and high density of nuclear pore complexes (NPCs), nuclear transport can be easily visualized in the Xenopus oocyte. Much insight into the mechanisms of nuclear import and export has been gained through use of this system (reviewed by Pant&eacute;, 2006). In addition, we have used microinjection of Xenopus oocytes to dissect the nuclear import pathways of several viruses that replicate in the host nucleus. 
Here we demonstrate the cytoplasmic microinjection of Xenopus oocytes with a nuclear import substrate. We also show preparation of the injected oocytes for visualization by thin-sectioning EM, including dissection, dehydration, and embedding of the oocytes into an epoxy embedding resin. Finally, we provide representative results for oocytes that have been microinjected with the capsid of the baculovirus Autographa californica nucleopolyhedrovirus (AcMNPV) or the parvovirus Minute Virus of Mice (MVM), and discuss potential applications of the technique.

Here we demonstrate cytoplasmic microinjection of Xenopus laevis oocytes with a nuclear import substrate, as well as preparation of the injected oocytes for visualization by thin-sectioning electron microscopy.

Microinjection of Xenopus laevis oocytes followed by thin-sectioning electron microscopy (EM) is an excellent system for studying nucleocytoplasmic ...

Tissue Determination Using the Animal Cap Transplant (ACT) Assay in Xenopus laevis

Many proteins play a dual role in embryonic development. Those that regulate cell fate determination in a specific tissue can also affect the development of a larger region of the embryo. This makes defining its role in a particular tissue difficult to analyze. For example, noggin overexpression in Xenopus laevis embryos causes the expansion of the entire anterior region, including the eye1,2. From this result, it is not known if Noggin plays a direct role in eye determination or that by causing an expansion of neural tissue, Noggin indirectly affects eye formation. Having this complex phenotype makes studying its eye-specific role in cell fate determination difficult to analyze. We have developed an assay that overcomes this problem. Taking advantage of the pluripotent nature of the Xenopus laevis animal cap 3, we have developed an assay to test the ability of gene product(s), like noggin or the eye field transcription factors (EFTFs), to transform caps into particular tissue or cell types by transplanting this tissue onto the side of the embryo 4. While we have found either Noggin protein treatment or a collection of transcription factors can determine retinal cell fate in animal caps, this procedure could be used to identify gene product(s) involved in specifying other tissues as well.

Tissue Determination Using the Animal Cap Transplant ACT Assay in Xenopus laevis

Animal caps overexpressing gene product(s) are transplanted to the flank of developing Xenopus laevis embryos in order to establish whether tissue is determined.

Many proteins play a dual role in embryonic development. Those that regulate cell fate determination in a specific tissue can also affect the development ...

Production of Transgenic Xenopus laevis by Restriction Enzyme Mediated Integration and Nuclear Transplantation

Stable integration of cloned gene products into the Xenopus genome is necessary to control the time and place of expression, to express genes at later stages of embryonic development, and to define how enhancers and promoters regulate gene expression within the embryo. The protocol demonstrated here can be used to efficiently produce transgenic Xenopus laevis embryos. This transgenesis approach involves three parts: 1. Sperm nuclei are isolated from adult X. laevis testis by treatment with lysolecithin, which permeabilizes the sperm plasma membrane. 2. Egg extract is prepared by low speed centrifugation, addition of calcium to cause the extract to progress to interphase of the cell cycle, and a high-speed centrifugation to isolate interphase cytosol. 3. Nuclear transplantation: the nuclei and extract are combined with the linearized plasmid DNA to be introduced as the transgene and a small amount of restriction enzyme. During a short reaction, egg extract partially decondenses the sperm chromatin and the restriction enzyme generates chromosomal breaks that promote recombination of the transgene into the genome. The treated sperm nuclei are then transplanted into unfertilized eggs. Integration of the transgene usually occurs prior to the first embryonic cleavage such that the resulting embryos are not chimeric. These embryos can be analyzed without any need to breed to the next generation, allowing for efficient and rapid generation of transgenic embryos for analyses of promoter and gene function. Adult X. laevis resulting from this procedure also propagate the transgene through the germline and can be used to generate lines of transgenic animals for multiple purposes.

Production of Transgenic Xenopus laevis by Restriction Enzyme Mediated Integration and Nuclear Transplantation

This video protocol demonstrates a method for generating transgenic Xenopus laevis by introduction of transgenes into sperm nuclei followed by nuclear transplantation into unfertilized eggs.

Stable integration of cloned gene products into the Xenopus genome is necessary to control the time and place of expression, to express genes at later ...

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes

The protocol presented here is designed to study the activation of the large conductance, voltage- and Ca2+-activated K+ (BK) channels. The protocol may also be used to study the structure-function relationship for other ion channels and neurotransmitter receptors1. BK channels are widely expressed in different tissues and have been implicated in many physiological functions, including regulation of smooth muscle contraction, frequency tuning of inner hair cells and regulation of neurotransmitter release2-6. BK channels are activated by membrane depolarization and by intracellular Ca2+ and Mg2+ 6-9. Therefore, the protocol is designed to control both the membrane voltage and the intracellular solution. In this protocol, messenger RNA of BK channels is injected into Xenopus laevis oocytes (stage V-VI) followed by 2-5 days of incubation at 18&deg;C10-13. Membrane patches that contain single or multiple BK channels are excised with the inside-out configuration using patch clamp techniques10-13. The intracellular side of the patch is perfused with desired solutions during recording so that the channel activation under different conditions can be examined. To summarize, the mRNA of BK channels is injected into Xenopus laevis oocytes to express channel proteins on the oocyte membrane; patch clamp techniques are used to record currents flowing through the channels under controlled voltage and intracellular solutions.

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes

Ionic current of BK channels is recorded using patch clamp techniques. BK channels are expressed in Xenopus oocytes by injecting messenger RNA. The intracellular solution during patch clamp recordings is controlled by a perfusion system.

The protocol presented here is designed to study the activation of the large conductance, voltage- and Ca2+-activated K+ (BK) channels. The protocol may ...

Facial Transplants in Xenopus laevis Embryos

Craniofacial birth defects occur in 1 out of every 700 live births, but etiology is rarely known due to limited understanding of craniofacial development. To identify where signaling pathways and tissues act during patterning of the developing face, a 'face transplant' technique has been developed in embryos of the frog Xenopus laevis. A region of presumptive facial tissue (the "Extreme Anterior Domain" (EAD)) is removed from a donor embryo at tailbud stage, and transplanted to a host embryo of the same stage, from which the equivalent region has been removed. This can be used to generate a chimeric face where the host or donor tissue has a loss or gain of function in a gene, and/or includes a lineage label. After healing, the outcome of development is monitored, and indicates roles of the signaling pathway within the donor or surrounding host tissues. Xenopus is a valuable model for face development, as the facial region is large and readily accessible for micromanipulation. Many embryos can be assayed, over a short time period since development occurs rapidly. Findings in the frog are relevant to human development, since craniofacial processes appear conserved between Xenopus and mammals.

Facial Transplants in Xenopus laevis Embryos

A technique for transplanting "Extreme Anterior Domain" facial tissue between Xenopus laevis embryos has been developed. Tissue can be moved from one gene expression background into another, allowing the study of local requirements for craniofacial development and for signaling interactions between facial regions.

Craniofacial birth defects occur in 1 out of every 700 live births, but etiology is rarely known due to limited understanding of craniofacial development. ...

The Slice Culture Method for Following Development of Tooth Germs In Explant Culture

Explant culture allows manipulation of developing organs at specific time points&#160;and is therefore an important method for the developmental biologist. For many organs it is difficult to access developing tissue to allow monitoring during ex vivo culture. The slice culture method allows access to tissue so that morphogenetic movements can be followed and specific cell populations can be targeted for manipulation or lineage tracing.
In this paper we describe a method of slice culture that has been very successful for culture of tooth germs in a range of species. The method provides excellent access to the tooth germs, which develop at a similar rate to that observed in vivo, surrounded by the other jaw tissues. This allows tissue interactions between the tooth and surrounding tissue to be monitored. Although this paper concentrates on tooth germs, the same protocol can be applied to follow development of a number of other organs, such as salivary glands, Meckel&#39;s cartilage, nasal glands, tongue, and ear.

Here we detail a method to culture tooth germs in mandible slices using a tissue chopper. This method allows unique access to the tooth during development, providing excellent opportunity for manipulation and lineage tracing, not available using more traditional culture methods.