We thank David Huss for helpful insights into this work. This work was supported in part by the Rose Hills Foundation Summer Research Fellowship (2016-2018) and USC Provost&#8217;s Undergrad Research Fellowship to M.T., the Saban Research Institute Intramural Training Pre-Doctoral Award to M.D., and the University of Southern California Undergraduate Research Associates Program award to R.L.

All animal procedures were carried out in accordance with approved guidelines from the Children&#8217;s Hospital Los Angeles and the University of Southern California Institutional Animal Care and Use Committees.
1. Generation pCS2-based Expression Vectors
<ol>
	<li>To clone pCS2.Lifeact-eGFP, prepare the vector backbone by digesting 2 &#181;g of pCS2.CycB1-GFP (a construct containing a different insert) with BamHI (10 U) and BsrGI (10 U) in appropriate digestion buffer (see Table of...

<ol>
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M., Lansford, R., Kulesa, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Four-color,+4-D+time-lapse+confocal+imaging+of+chick+embryos.">Four-color, 4-D time-lapse confocal imaging of chick embryos.</a> Biotechniques. 39 (5), 703-710 (2005).</li><li>Green, M. R., Maniatis, T., Melton, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+beta-globin+pre-mRNA+synthesized+in+vitro+is+accurately+spliced+in+Xenopus+oocyte+nuclei.">Human beta-globin pre-mRNA synthesized in vitro is accurately spliced in Xenopus oocyte nuclei.</a> Cell. 32 (3), 681-694 (1983).</li><li>Mimoto, M. S., Christian, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Manipulation+of+gene+function+in+Xenopus+laevis.">Manipulation of gene function in Xenopus laevis.</a> Methods in Molecular Biology. 770, 55-75 (2011).</li><li>Luni, 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=High-efficiency+cellular+reprogramming+with+microfluidics.">High-efficiency cellular reprogramming with microfluidics.</a> Nature Methods. 13 (5), 446-452 (2016).</li><li>Bugeon, S., 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=Direct+and+efficient+transfection+of+mouse+neural+stem+cells+and+mature+neurons+by+in+vivo+mRNA+electroporation.">Direct and efficient transfection of mouse neural stem cells and mature neurons by in vivo mRNA electroporation.</a> Development. 144 (21), 3968-3977 (2017).</li><li>Riedl, J., 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=Lifeact:+a+versatile+marker+to+visualize+F-actin.">Lifeact: a versatile marker to visualize F-actin.</a> Nature Methods. 5 (7), 605-607 (2008).</li><li>Turner, D. L., Weintraub, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+achaete-scute+homolog+3+in+Xenopus+embryos+converts+ectodermal+cells+to+a+neural+fate.">Expression of achaete-scute homolog 3 in Xenopus embryos converts ectodermal cells to a neural fate.</a> Genes and Development. 8 (12), 1434-1447 (1994).</li><li>Krieg, P. A., Melton, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+messenger+RNAs+are+produced+by+SP6+in+vitro+transcription+of+cloned+cDNAs.">Functional messenger RNAs are produced by SP6 in vitro transcription of cloned cDNAs.</a> Nucleic Acids Research. 12 (18), 7057-7070 (1984).</li><li>Hamburger, V., Hamilton, H. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+series+of+normal+stages+in+the+development+of+the+chick+embryo.">A series of normal stages in the development of the chick embryo.</a> Journal of Morphology. 88 (1), 49-92 (1951).</li><li>Eyal-Giladi, H., Kochav, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+cleavage+to+primitive+streak+formation:+a+complementary+normal+table+and+a+new+look+at+the+first+stage+of+the+development+of+the+chick.+I.+General+morphology.">From cleavage to primitive streak formation: a complementary normal table and a new look at the first stage of the development of the chick. I. General morphology.</a> Developmental Biology. 49, 321-337 (1976).</li><li>Ainsworth, S. J., Stanley, R. L., Evans, D. 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C., Lumsden, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+method+for+chick+whole-embryo+culture+using+a+filter+paper+carrier.">Improved method for chick whole-embryo culture using a filter paper carrier.</a> Developmental Dynamics. 220 (3), 284-289 (2001).</li><li>Hama, H., 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=Scale:+a+chemical+approach+for+fluorescence+imaging+and+reconstruction+of+transparent+mouse+brain.">Scale: a chemical approach for fluorescence imaging and reconstruction of transparent mouse brain.</a> Nature Neurosciences. 14 (11), 1481-1488 (2011).</li><li>New, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+technique+for+the+cultivation+of+the+chick+embryo+in+vitro.">A new technique for the cultivation of the chick embryo in vitro.</a> Journal of Embryology and Experimental Morphology. 3, 320-331 (1955).</li><li>Drake, C. J., Davis, L. A., Hungerford, J. E., Little, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perturbation+of+beta+1+integrin-mediated+adhesions+results+in+altered+somite+cell+shape+and+behavior.">Perturbation of beta 1 integrin-mediated adhesions results in altered somite cell shape and behavior.</a> Developmental Biology. 149 (2), 327-338 (1992).</li><li>Sato, Y., 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=Dynamic+analysis+of+vascular+morphogenesis+using+transgenic+quail+embryos.">Dynamic analysis of vascular morphogenesis using transgenic quail embryos.</a> PLoS ONE. 5 (9), e12674 (2010).</li><li>Kanda, T., Sullivan, K. F., Wahl, G. 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S., Krull, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sparking+new+frontiers:+using+in+vivo+electroporation+for+genetic+manipulations.">Sparking new frontiers: using in vivo electroporation for genetic manipulations.</a> Developmental Biology. 233 (1), 13-21 (2001).</li><li>Meyer, S., Temme, C., Wahle, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Messenger+RNA+turnover+in+eukaryotes:+pathways+and+enzymes.">Messenger RNA turnover in eukaryotes: pathways and enzymes.</a> Critical Reviews in Biochemistry and Molecular Biology. 39 (4), 197-216 (2004).</li><li>Bevilacqua, P. C., Ritchey, L. E., Su, Z., Assmann, 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=Genome-Wide+Analysis+of+RNA+Secondary+Structure.">Genome-Wide Analysis of RNA Secondary Structure.</a> Annual Review in Genetics. 50, 235-266 (2016).</li><li>Harland, R., Misher, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stability+of+RNA+in+developing+Xenopus+embryos+and+identification+of+a+destabilizing+sequence+in+TFIIIA+messenger+RNA.">Stability of RNA in developing Xenopus embryos and identification of a destabilizing sequence in TFIIIA messenger RNA.</a> Development. 102 (4), 837-852 (1988).</li><li>Lippincott-Schwartz, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+long+road:+peering+into+live+cells.">The long road: peering into live cells.</a> Nature Cell Biology. 12 (10), 918 (2010).</li><li>Sato, Y., Lansford, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transgenesis+and+imaging+in+birds,+and+available+transgenic+reporter+lines.">Transgenesis and imaging in birds, and available transgenic reporter lines.</a> Development Growth &amp; Differentiation. 55 (4), 406-421 (2013).</li><li>Goldman, R. D., Spector, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Live Cell Imaging: A Laboratory Manual. , (2005).</li></ol>

The authors have no conflicts of interest to declare.

In this protocol, we provided step by step instructions on how to precisely microinject and electroporate mRNA into the cells of gastrulating quail embryos. We demonstrated that in vitro synthesized mRNA electroporation allows fast and efficient expression of fluorescent proteins (FPs) in gastrulating quail embryos (Figure 2 and 3). Fluorescence from H2B-citrine protein translated from electroporated mRNAs could be detected by confocal microscopy within ~20 min and increased...

Electroporation is a physical transfection method that uses an electrical pulse to create transient pores in the plasma membrane, allowing substances like nucleic acids or chemicals to pass into the cytosol. Electroporation is widely used to deliver DNA into bacteria, yeast, plants, and mammalian cells1,2,3. It is routinely used to introduce genetic payloads into target cells and tissues within the developing avian embryo to study the genetic control of development or label migrating populations of cells4,5,6,7. However, several experimental limitations also exist with DNA electroporation8. For instance, DNA electroporation often introduces highly variable numbers of expression vectors per cell and subsequently the mRNAs and proteins they encode. This variability can lead to considerable cell-cell heterogeneity that complicates both image analysis and data interpretation9,10. Additionally, proteins from DNA electroporation only begin to express ~3 h post-electroporation and do not reach the maximum efficiency in cell number and fluorescence intensity until 12 h, likely due to the time required to transfer into the nucleus and complete both transcription and translation in vivo11.
In contrast, mRNA transfection has been effectively used in a variety of model systems, including Xenopus laevis oocytes by microinjection12,13, reprogramming human stem cells by mRNA lipofectamine transfection14, and electroporating recalcitrant neural stem cells in adult mice15. We tested the ability of mRNA electroporation to efficiently label cells during early avian embryonic development using in vitro synthesized mRNAs that encode distinct fluorescent proteins (FPs). For our studies, we used the pCS2+ vector, a multipurpose expression vector that is commonly used for expressing proteins in Xenopus and zebrafish embryos. The SP6 and T7 RNA polymerase promoters in the pCS2+ permit the synthesis of mRNA and protein&#160;from any cloned gene when used in an&#160;in vitro&#160;transcription/translation system.
Here, we demonstrate that mRNA electroporation allows fast and efficient expression of fluorescent proteins (FPs) in gastrulating quail embryos. We designed and generated many of the expression vectors used in these studies. For example, we subcloned the LifeAct-eGFP gene16 into the pCS2+ vector17 to express from the CMV promoter and SP6 promoter. The inserted gene lies downstream of the SP6 promoter and upstream of the SV40 poly(A) tail18. In embryos co-electroporated with mRNA and DNA, FPs encoded from in vitro transcribed mRNAs were first detected within 20 min of electroporation, whereas FPs from DNA expression vectors were detected only after 3 h. Multiple mRNAs encoding for nuclear, Golgi, and membrane proteins can be electroporated into an embryo simultaneously, resulting in the quick and efficient expression of multiple proteins in individual cells. Finally, using an in vivo fluorescence recovery after photobleaching (FRAP) assay, we show that a majority of the electroporated mRNAs decay within 2 h. Thus, fast initial protein production combined with limited new protein translation makes mRNA electroporation a valuable technique when temporal control of expression is necessary.

<table>
	<tbody>
		<tr>
			<td>BamHI-HF</td>
			<td>New England Biolabs</td>
			<td>R3136L</td>
			<td></td>
		</tr>
		<tr>
			<td>BglII</td>
			<td>New England Biolabs</td>
			<td>R0144S</td>
			<td></td>
		</tr>
		<tr>
			<td>BsrG1-HF</td>
			<td>New England Biolabs</td>
			<td>R3575S</td>
			<td></td>
		</tr>
		<tr>
			<td>NotI-HF</td>
			<td>New England Biolabs</td>
			<td>R3189L</td>
			<td></td>
		</tr>
		<tr>
			<td>SalI-HF</td>
			<td>New England Biolabs</td>
			<td>R3138L</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenol:Chloroform:Isoamyl Alcohol</td>
			<td>Thermo Fisher</td>
			<td>15593031</td>
			<td></td>
		</tr>
		<tr>
			<td>SP6 mMessage Machine in vitro transcription kit</td>
			<td>Thermo Fisher</td>
			<td>AM1340</td>
			<td></td>
		</tr>
		<tr>
			<td>Fast Green FCF</td>
			<td>Sigma Aldrich</td>
			<td>F7252</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma Aldrich</td>
			<td>93443</td>
			<td>4-(1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol, t-Octylphenoxypolyethoxyethanol, Polyethylene glycol tert-octylphenyl ether</td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td>Sigma Aldrich</td>
			<td>D9542</td>
			<td>2-(4-Amidinophenyl)-6-indolecarbamidine dihydrochloride, 4&#8242;,6-Diamidino-2-phenylindole dihydrochloride, DAPI dihydrochloride</td>
		</tr>
		<tr>
			<td>Whatman No.1 filter paper</td>
			<td>Sigma Aldrich</td>
			<td>WHA1001125</td>
			<td></td>
		</tr>
		<tr>
			<td>glycerol</td>
			<td>Sigma Aldrich</td>
			<td>G9012</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea</td>
			<td>Sigma Aldrich</td>
			<td>51457</td>
			<td></td>
		</tr>
		<tr>
			<td>pmTurquoise2-Golgi</td>
			<td>Addgene</td>
			<td>36205</td>
			<td>pmTurquoise2-Golgi was a gift from Dorus Gadella (Addgene plasmid # 36205 ; http://n2t.net/addgene:36205 ; RRID:Addgene_36205)</td>
		</tr>
		<tr>
			<td>pmEGFP-N1-LifeAct</td>
			<td></td>
			<td></td>
			<td>Nat. Methods 2008;5:605-7. PubMed ID: 18536722</td>
		</tr>
		<tr>
			<td>pCS2.Lifeact-mGFP</td>
			<td>Addgene</td>
			<td></td>
			<td>This paper</td>
		</tr>
		<tr>
			<td>pCS.H2B-citrine</td>
			<td>Addgene</td>
			<td>53752</td>
			<td>pCS-H2B-citrine was a gift from Sean Megason (Addgene plasmid # 53752 ; http://n2t.net/addgene:53752 ; RRID:Addgene_53752)</td>
		</tr>
		<tr>
			<td>pCS.memb-mCherry</td>
			<td>Addgene</td>
			<td>#53750</td>
			<td>pCS-memb-mCherry was a gift from Sean Megason (Addgene plasmid # 53750 ; http://n2t.net/addgene:53750 ; RRID:Addgene_53750)</td>
		</tr>
		<tr>
			<td>Zeiss LSM-780 inverted microscope</td>
			<td>Carl Zeiss Microscopy GmbH</td>
			<td></td>
			<td>The LSM-780 is a confocal and multi-photon microscope that offers the sensitivity required for vital imaging work. Equipped with a motorized stage, an autofocus device, and a full stage-top blackout incubator, the 780 is an excellent microscope for high-end live cell/embryo imaging. The high-sensitivity 32-channel Quasar detector allows for spectral imaging, linear unmixing, and high color count (&#62;4) image acquisition. Excitation can be performed with 6 lines single photon lasers (405, 458, 488, 514, 564 and 633 nm), Chameleon (Coherent) 2-photon laser (range from 690nm to 1000nm), and run with ZEN 2011 SP7 (Black) system software.</td>
		</tr>
		<tr>
			<td>CUY-21 EDIT in vivo electroporator</td>
			<td>Bex Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Platinum flat square electrode, side length 5 mm</td>
			<td>Bex Co., Ltd.</td>
			<td>LF701P5E</td>
			<td></td>
		</tr>
		<tr>
			<td>Olympus MVX10 FL Stereo Microscope</td>
			<td>Olympus LifeScience</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>XM10 Monochrome camera</td>
			<td>Olympus LifeScience</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate-Buffered Saline (PBS) for HCR (10&#215;, pH 7.4) </td>
			<td></td>
			<td></td>
			<td>To prepare 1 L of a 10&#215; stock solution, combine 80 g of NaCl (Sigma-Aldrich S3014), 2 g of KCl (Sigma-Aldrich P9541), 11.4 g of Na2HPO4 (anhydrous; Sigma-Aldrich S3264), and 2.7 g of KH2PO4 (anhydrous; Sigma-Aldrich P9791). Adjust the pH to 7.4 with HCl, and bring the final volume to 1 L with ultrapure H2O. Avoid using CaCl2 and MgCl2 in PBS for HCR. It is important that the PBS for HCR is prepared as an RNase-free solution (e.g., via diethylpyrocarbonate [DEPC] treatment).</td>
		</tr>
		<tr>
			<td>1.37 M NaCl</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>27 mM KCl</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>80 mM Na2HPO4 20 mM KH2PO4</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PBS/Triton</td>
			<td></td>
			<td></td>
			<td>Add 1 mL of Triton X-100 (Sigma Aldrich 93443) and 100 mL of 10&#215; PBS to 890 mL of ultrapure distilled H2O. Filter the solution through a 0.2-&#956;m filter and store it at 4 &#778;C until use.</td>
		</tr>
		<tr>
			<td>1&#215; phosphate-buffered saline (PBS) (DEPC-treated; pH 7.4)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>0.1% Triton X-100</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

fast and efficient expression of multiple proteins in avian embryos using mrna electroporation

We report that mRNA electroporation permits fluorescent proteins to label cells in living quail embryos more quickly and broadly than DNA electroporation. The high transfection efficiency permits at least 4 distinct mRNAs to be co-transfected with ~87% efficiency. Most of the electroporated mRNAs are degraded during the first 2 h post-electroporation, permitting time-sensitive experiments to be carried out in the developing embryo. Finally, we describe how to dynamically image live embryos electroporated with mRNAs that encode various subcellular targeted fluorescent proteins.

mRNA electroporation is more efficient than DNA electroporation
We used pCS2+.H2B-Citrine to prepare in vitro transcribed mRNA. Since DNA electroporation is usually performed at 1-2 &#181;g/&#181;L, we used an equimolar concentration of mRNA (calculated to be around 0.25-0.5 &#181;g/&#181;L for H2B-Citrine) for mRNA electroporation. We first tested the electroporation efficiency of pCS2+.H2B-Citrine DNA compared...

Watch this Scientific Journal Video about Fast and Efficient Expression of Multiple Proteins in Avian Embryos Using mRNA Electroporation at JoVE.com

Fast and Efficient Expression of Multiple Proteins in Avian Embryos Using mRNA Electroporation

We report messenger RNA (mRNA) electroporation as a method that permits fast and efficient expression of multiple proteins in the quail embryo model system. This method can be used to fluorescently label cells and record their in vivo movements by time-lapse microscopy shortly after electroporation.

We report that mRNA electroporation permits fluorescent proteins to label cells in living quail embryos more quickly and broadly than DNA electroporation. ...

mRNA electroporation provides a fast, efficient, and spatially and temporally controlled expression of multiple proteins within the avian model system. This method allows for a more broad and quick expression of fluorescent proteins than the labeling achieved by standard DNA electroporation. Electroporation facilitates the transient opening of pores in the plasma membrane that serve as conduits for the transfer of genetic payloads like RNA and DNA into the cells of numerous model organisms.For the initial experiments work with embryos that are older than a day old since they are hardier and more resistant to external manipulations like electroporation. At the appropriate embryonic developmental stage gently break and pour the quail egg contents into a 10 centimeter Petri dish. Use a transfer pipette to remove the majority of the thick albumen.Use a lab tissue to gently wipe the surface of the yoke to remove the remaining thick albumen around the embryo to ensure that the embryo will stick tightly to the paper ring. Lay precut filter paper over the embryo and use scissors to smoothly cut around the perimeter of the embryo. Use a Pasteur pipette to layer PPS under the embryo using gentle streams to vacate any yoke sticking to the tissue.Slowly pull the embryo paper ring at an oblique angle up and off of the yoke. Place the paper into a Petri dish filled with PBS for further cleaning. Once most of the yoke has been removed, place the embryo ventral side up in a 35 millimeter Petri dish covered with a semisolid mixture of agar and albumen.Prepare the electroporation chamber by connecting the black electrode filling it with PBS and placing the embryo inside. Use a glass microcapillary to inject a bolus of 200 nanoliters of mRNA into the cavity between the epiblast and vitelline membrane covering the desired region. And then use the red electrode to electroporate the embryo.Place the electroporated embryo back onto the agar-albumen mixture and incubate at 38 degrees Celsius until the desired developmental stage. For imaging of the electroporation-encoded fluorescent proteins observe all of the electroporated embryos under a fluorescent dissecting stereoscope to select the healthiest and best electroporated embryo for the dynamic imaging experiments. Continue to incubate the other electroplated embryos and non-electroplated embryos in a separate incubator.Briefly rinse the selected embryo with PBS to remove any bubbles that may have formed on the dorsal side of the embryo during the electroporation. Place the cleaned embryo directly into an imaging dish containing a thin layer of about 150 microliters of albumen-agar taking care not to generate any bubbles on the dorsal surface of the embryo. Add a small moist rolled up piece of tissue paper along the inside edges of the imaging dish.Seal the dish with paraffin film to minimize evaporation during the imaging and incubation. Move the dish quickly to the prewarmed stage of a confocal microscope and use the brightfield channel to locate the colored dye in the embryo. Set the imaging software to the desired objective, dichroic mirror, and emission spectra, and turn on an appropriate laser.Take care that the cells will remain in the image vision for the entirety of the movie. Use a high enough imaging resolution, and ensure that the imaging conditions will not cause phototoxicity. Click Live in the imaging software and adjust the laser power to a setting that is appropriate for the fluorescence intensity depending on each microscope laser power.Begin imaging the embryo using 1%laser power and an 800 gain, increasing the laser power slowly by 1%increments until saturated pixels are seen. When saturated pixels are observed decrease the laser power slightly until no saturated pixels can be visualized. Image the embryo every three to five minutes to check the migration of individual cells across different time points using five micrometer Z-stacks of the entire electroplated area with some extra room toward the bottom of the Z-stack in case the embryo sinks into the agarose bed during the imaging session.To observe how fast the cells are moving check the first few time points of the first movie. If the cells are moving at a fast rate, consider expanding the zoom of the imaged area or imaging a different region. When the entire electroplated region of the embryo has been imaged, image in unelectroplated region of the same embryo to determine the autofluorescence levels.To determine how long transfected mRNA can be translated into fluorescent proteins after confirming electroporation of the gene of interest on the stereo microscope, place the embryo on a preheated stage of the inverted confocal microscope and use the 405 nanometer laser with a 70%laser power, 100 iterations, and a scan speed of four to photobleach most of the cellular fluorescence from the electroplated gene at a variety of time points. Continue to incubate the embryos on the stage at 36 degrees Celsius after photo bleaching, taking care to pay attention to the actively dividing cells within the photobleached region that are typically only seen in healthy embryos and thus indicate that the electroporation did not harm the embryonic cells. Acquire post-bleach Z-stack images of the electroplated region for a desired length of time at regular three to five minute time intervals.To ensure that the imaging conditions do not deleteriously affect the embryo survival concurrently incubate electroplated embryos that are not photobleached to serve as a control for the imaging. To quantitate the photobleaching results for the mRNA decay post-electroporation use ImageJ to measure the fluorescence intensity of a 7.5 micrometer circle in the center of the electroplated area of each cell to track the cell fluorescence over each three to five minute interval. When all of the cells within the photobleached region that are not undergoing mitosis and have been completely photobleached have been measured, plot the fluorescence intensity over time post-bleach at each of the time points the embryo was photobleached.Although DNA electroporation leads to a brighter fluorescence in some electroplated cells, the efficiency of DNA electroporation is visibly lower compared to the widely expressed mRNA-encoded fluorescent proteins. When comparing DNA and mRNA co-electroporation within the same embryo, the DNA expressing fluorescent protein efficiency is also significantly and consistently less efficient than that of the mRNA expressing fluorescent protein. Quantification of all of the embryos electroplated with only mRNA, DNA or a combination of the two, reveals that mRNA transfects about 75%of the cells in a given region, while DNA only transfects about 25%of the cells.The transfected mRNA should lead to a faster protein production compared to transfected DNA since the mRNA can be immediately recognized by cytosolic translation machinery. Although the co-electroporation of multiple DNAs has previously been shown to be relatively inefficient, the co-electroporation of four mRNAs in this experiment resulted in an 87%transfection efficiency of all four of the mRNAs within all of the electroplated regions. Although photobleaching initially reduces the fluorescence intensity in the photobleached cells by about 95%some cells remain that recover their ability to divide and express fluorescent proteins shortly after electroporation.This ability decreases over five hours post-electroporation however. Take your time optimizing the best imaging conditions and continue to tinker even after starting the movie being ready to make any adjustments if needed.

fast-efficient-expression-multiple-proteins-avian-embryos-using-mrna

Research

JoVE Journal

Developmental Biology

7.0K visualizações.  University of Southern California, Los Angeles. A eletroporação mRNA fornece uma expressão rápida, eficiente e espacialmente e temporalmente controlada de múltiplas proteínas dentro do sistema modelo aviário. Este método permite uma expressão mais ampla e rápida de proteínas fluorescentes do que a rotulagem alcançada pela eletroporação padrão de DNA. A eletroporação facilita a abertura transitória de poros na membrana plasmática que servem como conduítes para a transferência de cargas genéticas como RNA e DNA para as ...