This work was supported by a G. Harold &#38; Leila Y. Mathers Award to H.L. and an NIH grant (R24 GM080527) to R.E.S. C.E.J. was an NRSA Postdoctoral Fellow (NIH F32GM9037222) and is currently supported by a Mentored Research Scientist Development Award from the National Institute on Aging (K01AG04435). We would like to thank the reviewers for helpful comments.

1. Preparation of Plasmid DNA, Needles, and Injection Dishes
<ol>
	<li>Prepare the plasmid DNA using a High Speed Maxi or Midi kit and concentrate the DNA to 2.5 mg/ml using ethanol precipitation. The DNA pellet should be dissolved in nuclease-free deionized water. Store the DNA in 10-20 &#181;l aliquots at -20&#176;C. (See Supplementary Table 1 for a list of available vectors)</li>
	<li>Make an injection dish using agarose to construct a trough for holding embryos in a 100 x 15 mm Petri dish.
	<ol>
		<li>Place a 75 x 50 glass microscope slide into a 100 x 15 mm Petri dish at an angle. Pour approximately 50 ml of 2% agarose melted in Hydra medium24 into the Petri dish. Alternatively, pour the agarose into the dish first and float a &#8220;Microinjection Fish Mold&#8221; on top.</li>
		<li>After the agarose has solidified, remove the glass slide or the mold. If a glass slide was used, cut away excess agarose with a razor blade to form a wall. Pour Hydra medium into the dish and use it immediately or store it at 4&#176;C until needed. Note: Injection dishes can be reused if stored at 4&#176;C between uses.</li>
	</ol>
	</li>
	<li>Pull needles from borosilicate glass capillaries with a filament on the micropipette puller using the following conditions: heat 525, pull 75, velocity 100, time 50. Store the needles by pressing them into a narrow strip of clay in a Petri dish such that they are held parallel to the bottom of the dish.</li>
	<li>To prepare the injection solution, combine 3 &#181;l of 2.5 mg/ml plasmid DNA solution with 2 &#181;l of 10% phenol red. Vortex the solution briefly and then spin it for 10 min&#160;at maximum speed in a microcentrifuge to remove any particles that might clog the needle.</li>
	<li>Under a dissecting microscope, clip the needle a few millimeters from the tip with forceps to create a small opening. Note: There is some flexibility in the appropriate size of the opening because the pressure can be adjusted in step 3.3 to accommodate this variation.</li>
	<li>Place the Petri dish so that it is holding the needle in a vertical position with the tip down. Load the needle with approximately 0.5 &#181;l of injection solution by pipetting the liquid into the back end of the needle. Allow capillary action to pull the solution into the tip of the needle.</li>
</ol>
2. Preparation of Embryos for Injection
<ol>
	<li>On a daily basis scan the Hydra AEP strain culture for polyps producing eggs. Collect these polyps and set them aside in a separate culture dish. Observe these polyps every few hours during the day to monitor the progress of egg formation. When eggs break through the ectoderm and sit on a ring of retracted ectodermal cells they are ready for injection25. Place these polyps in a dish with several Hydra that have testes for at least 1 hr before injection to allow for fertilization. Hydra males will release sperm without any special manipulation.</li>
	<li>If females are found in the AEP colony with fully-formed eggs, which are approximately 400 &#956;m in diameter25, or 1- to 8-cell stage embryos, also collect these for injection. Immediately inject embryos that have started cleaving. Note: It is not possible to tell the difference between fully-formed eggs and single-celled zygotes, thus these should be incubated with males prior to injection.</li>
	<li>Before injection, remove most of the parental tissue above and below the embryo using a scalpel with a #15 blade. Leave only the embryo with a small piece of body column attached, to be used to manipulate the embryo with forceps if necessary. Note: The tissue that is dissected away from the embryo will regenerate and should be saved to ensure that females remain in the Hydra colony.</li>
	<li>Using a Pasteur pipette, move embryos to the injection dish, arranging them parallel to the wall of the agarose trough.</li>
</ol>
3. Microinjection of Plasmid DNA
<ol>
	<li>Mount the microinjector on a magnetic stand that sits on an iron plate. Mount the injection holder, which is the part of the microinjector that holds the needle, on a joystick micromanipulator. Mount the joystick manipulator to the iron plate, with a magnetic stand. Place this entire set-up on the right side of a dissecting microscope and position the injection holder so that it is visible in the observation field.</li>
	<li>Place the injection dish with embryos under the dissecting microscope, oriented such that the vertical wall of the agarose trough is to the left. Insert the needle into the injection holder and lower the tip of the needle into the Hydra medium in the dish.</li>
	<li>Slowly turn the knob of the syringe in the clockwise direction until mineral oil fills the top of the needle and a steady stream of injection solution is observed exiting the needle into the Hydra medium. If the stream is too strong, lower the pressure by turning the knob counterclockwise. Practice this step to routinely obtain a suitable pressure, which depends on the size of the needle opening (i.e., how the needle was clipped in step 1.5). Note: If the stream is too strong, the embryo will not survive the injection.</li>
	<li>While viewing through the dissecting microscope, move the injection dish so that the first embryo is at the center of the field. Move the needle so that it is touching that embryo. Use the micromanipulator to pierce the embryo with the needle. Note: The vertical wall of the agarose trough will keep the embryo from being pushed aside by the needle.</li>
	<li>Allow the injection solution to flow into the embryo 1 or 2 sec and then remove the needle quickly. If the embryo has more than one cell, inject each cell individually. Use forceps to reorient the embryo to align the next cell with the tip of the needle.</li>
	<li>After the first embryo is injected, move the dish so that the next embryo is in the injection position and repeat the procedure; continue until all embryos have been injected.</li>
</ol>
4. Culturing and Hatching of Embryos
<ol>
	<li>Move all of the injected embryos into a dish with a few Hydra that have testes (this is to ensure that all embryos are fertilized). Incubate the embryos in an 18 &#176;C incubator while they continue embryogenesis.</li>
	<li>Once the cuticle stage is reached, move each injected embryo to an individual well of a 24-well plate filled with Hydra medium.</li>
	<li>Incubate the injected embryos for 2 weeks in the dark at 18 &#176;C.</li>
	<li>After the 2 week incubation period, check each injected embryo under the dissecting microscope. Note any cases in which the cuticle-stage embryo has detached from the small piece of parental tissue and the parental tissue has regenerated. Remove this regenerated polyp immediately so that it is not mistaken for a new hatchling.</li>
	<li>Move the dish of injected embryos under an aquarium light at RT. Check the plates each day and collect hatchlings. New hatchlings will be white because the typical pink color of Hydra polyps comes from the Artemia they eat.</li>
	<li>Observe the hatchlings under a fluorescence microscope to detect transgene expression.</li>
</ol>

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N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pattern+of+epithelial+cell+cycling+in+hydra.">Pattern of epithelial cell cycling in hydra.</a> Dev Biol. 148, 602-611 (1991).</li><li>Dubel, S., Hoffmeister, S. A., Schaller, H. 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N., Murphy, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+interstitial+stem+cells+in+hydra+by+cloning.">Characterization of interstitial stem cells in hydra by cloning.</a> Dev Biol. 58, 372-383 (1977).</li><li>Chapman, 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=The+dynamic+genome+of+Hydra.">The dynamic genome of Hydra.</a> Nature. 464, 592-596 (2010).</li><li>Boehm, A. M., Bosch, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Migration+of+multipotent+interstitial+stem+cells+in+Hydra.">Migration of multipotent interstitial stem cells in Hydra.</a> Zoology (Jena). 115, 275-282 (2012).</li><li>Glauber, K. M., 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+small+molecule+screen+identifies+a+novel+compound+that+induces+a+homeotic+transformation+in+Hydra.">A small molecule screen identifies a novel compound that induces a homeotic transformation in Hydra.</a> Development. 140, 4788-4796 (2013).</li><li>Siebert, S., Anton-Erxleben, F., Bosch, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+type+complexity+in+the+basal+metazoan+Hydra+is+maintained+by+both+stem+cell+based+mechanisms+and+transdifferentiation.">Cell type complexity in the basal metazoan Hydra is maintained by both stem cell based mechanisms and transdifferentiation.</a> Dev Biol. 313, 13-24 (2008).</li><li>Anton-Erxleben, F., Thomas, A., Wittlieb, J., Fraune, S., Bosch, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasticity+of+epithelial+cell+shape+in+response+to+upstream+signals:+a+whole-organism+study+using+transgenic+Hydra.">Plasticity of epithelial cell shape in response to upstream signals: a whole-organism study using transgenic Hydra.</a> Zoology (Jena). 112, 185-194 (2009).</li><li>Hemmrich, 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=Molecular+signatures+of+the+three+stem+cell+lineages+in+Hydra+and+the+emergence+of+stem+cell+function+at+the+base+of+multicellularity.">Molecular signatures of the three stem cell lineages in Hydra and the emergence of stem cell function at the base of multicellularity.</a> Mol Biol Evol. , (2012).</li><li>Juliano, C. 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=PIWI+proteins+and+PIWI-interacting+RNAs+function+in+Hydra+somatic+stem+cells.">PIWI proteins and PIWI-interacting RNAs function in Hydra somatic stem cells.</a> Proc Natl Acad Sci U S A. 111, 337-342 (2014).</li><li>Nishimiya-Fujisawa, C., Kobayashi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Germline+stem+cells+and+sex+determination+in+Hydra.">Germline stem cells and sex determination in Hydra.</a> Int J Dev Biol. 56, 499-508 (2012).</li><li>Milde, 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=Characterization+of+taxonomically+restricted+genes+in+a+phylum-restricted+cell+type.">Characterization of taxonomically restricted genes in a phylum-restricted cell type.</a> Genome Biol. 10, 8 (2009).</li><li>Nakamura, Y., Tsiairis, C. D., Ozbek, S., Holstein, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autoregulatory+and+repressive+inputs+localize+Hydra+Wnt3+to+the+head+organizer.">Autoregulatory and repressive inputs localize Hydra Wnt3 to the head organizer.</a> Proc Natl Acad Sci U S A. 108, 9137-9142 (2011).</li><li>Gee, 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=beta-catenin+plays+a+central+role+in+setting+up+the+head+organizer+in+hydra.">beta-catenin plays a central role in setting up the head organizer in hydra.</a> Dev Biol. 340, 116-124 (2010).</li><li>Fraune, 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=In+an+early+branching+metazoan,+bacterial+colonization+of+the+embryo+is+controlled+by+maternal+antimicrobial+peptides.">In an early branching metazoan, bacterial colonization of the embryo is controlled by maternal antimicrobial peptides.</a> Proc Natl Acad Sci U S A. 107, 18067-18072 (2010).</li><li>Bridge, 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=FoxO+and+stress+responses+in+the+cnidarian+Hydra+vulgaris.">FoxO and stress responses in the cnidarian Hydra vulgaris.</a> PLoS One. 5, e11686 (2010).</li><li>Boehm, A. M., 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=FoxO+is+a+critical+regulator+of+stem+cell+maintenance+in+immortal+Hydra.">FoxO is a critical regulator of stem cell maintenance in immortal Hydra.</a> Proc Natl Acad Sci U S A. 109, 19697-19702 (2012).</li><li>Franzenburg, 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=MyD88-deficient+Hydra+reveal+an+ancient+function+of+TLR+signaling+in+sensing+bacterial+colonizers.">MyD88-deficient Hydra reveal an ancient function of TLR signaling in sensing bacterial colonizers.</a> Proc Natl Acad Sci U S A. 109, 19374-19379 (2012).</li><li>Dana, C. E., Glauber, K. M., Chan, T. A., Bridge, D. M., Steele, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Incorporation+of+a+horizontally+transferred+gene+into+an+operon+during+cnidarian+evolution.">Incorporation of a horizontally transferred gene into an operon during cnidarian evolution.</a> PLoS One. 7, e31643 (2012).</li><li>Lenhoff, H. M., Lenhoff, H. 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> Hydra: Research Methods. , 29-34 (1983).</li><li>Miller, M. A., Technau, U., Smith, K. M., Steele, R. 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The authors have nothing to disclose

Hydra routinely reproduces asexually, but requires environmental stimuli to begin producing gametes. These stimuli are not well-defined for most Hydra species and may differ from strain to strain. A significant hurdle to the production of transgenic Hydra is obtaining embryos on a regular basis because it can be difficult in a laboratory setting to induce Hydra to become sexual. The AEP strain25, however, produces gametes readily in the laboratory and this is the only strain...

Hydra has been used to study regeneration, pattern formation, and stem cells for approximately 250 years2. Hydra has a simple body plan consisting of three cell lineages: ectodermal epithelial, endodermal epithelial, and interstitial. The tubular body is formed by the ectodermal and endodermal epithelial lineages, each of which is a single cell layer. All of the epithelial cells in the body column are mitotic. When epithelial cells are displaced into the extremities3, the head (mouth and tentacles) at the oral end or the foot (basal disc) at the aboral end, they arrest in the G2 phase of the cell cycle and change cell fate4. The cells of the interstitial lineage reside within the interstices between the epithelial cells. This lineage is supported by multipotent stem cells that are located in the ectodermal epithelial layer of the body column5. The interstitial stem cells give rise to three somatic cell types (nerves, gland cells, and nematocytes) and the germ cells6,7.
As a member of the phylum Cnidaria, the sister group to all bilaterians, Hydra can shed light on fundamental biological processes shared among multicellular animals. Until recently, these efforts were impeded by the lack of reliable methods for the perturbation of gene function. However, with the development of transgenic methodology1, we are now able to take full advantage of Hydra to gain a better understanding of the basic mechanisms common to multicellular animals, such as stem cell function, regeneration, and patterning. Transgenic Hydra lines are established by injection of plasmid DNA into embryos, which results in random integration and chimeric expression in a substantial frequency of hatchlings. A line with uniform expression in a particular lineage can be established by asexual propagation. The ability to clonally propagate transgenic Hydra lines is an advantage over the majority of animal models, which can be propagated only by sexual reproduction. In addition, transgenic cells can be tracked easily in vivo due to the transparency of the animal and the absence of endogenous fluorescent proteins 8.
In the seven years since the first transgenic Hydra lines were made1, such lines have been used for a variety of applications. Expression of fluorescent proteins in different cell types has made it possible to track cell movement, observe changes in cell shape, and track cell fates both in wild type conditions and after chemical perturbation1,5,9-12. In addition, expression of different fluorescent proteins in the various lineages allows for FACS isolation of specific cell populations. This technique has been used for the sequencing of stem-cell specific mRNAs and lineage-specific small RNAs13,14. While the promoter of one of the two Hydra actin genes has been most widely used, a few cell-type specific promoters have been identified and used to drive expression of GFP in transgenic Hydra9,11,15,16. In the future, cell-type specific promoters will allow for the observation and collection of any specific cell type. In addition, a transgenic approach was successfully used to define the cis-acting regulatory elements of the Wnt3 promoter17.
The development of transgenic methods in Hydra provides a robust approach for testing the function of genes by ectopic expression, overexpression, and knockdown. Transgenic animals have been made that express fluorescently-tagged proteins in order to examine both function and cellular localization18-20. In addition, the expression of RNA hairpins in the 3&#8217;UTR of a GFP transgene leads to knockdown of target genes21,22. In these approaches GFP is required to identify and track the transgenic tissue during the creation of the transgenic line. However, it is likely that in some cases the GFP molecule would interfere with the function of the tagged protein. A recent study demonstrates that Hydra genes can be arranged in an operon configuration, i.e.,&#160;polycistronic transcripts are made, which are then separated by trans-spliced leader addition and translated separately23. By placing a gene encoding a protein or an RNA hairpin in the upstream position of an operon and a fluorescent protein gene in the downstream position, one can track transgenic tissue without having to tag the gene encoding the protein or RNA hairpin. This method has been used to express an RNA hairpin in an operon configuration with DsRed2 in order to achieve gene knockdown14.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">AEP Hydra Strain</td>
			<td style="width:112px;">NA</td>
			<td style="width:119px;">NA</td>
			<td style="width:576px;">Email: Celina Juliano at celina.juliano@yale.edu or Hiroshi Shimizu bubuchin2006@yahoo.co.jp</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">High Speed Maxi Kit</td>
			<td style="width:112px;">Qiagen</td>
			<td align="right" style="width:119px;">12662</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">100 x 15 mm Petri Dishes</td>
			<td style="width:112px;">BD Falcon</td>
			<td align="right" style="width:119px;">351029</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">75 x 50 mm Glass Microscope Slide</td>
			<td style="width:112px;">Sigma</td>
			<td>CLS294775X50</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Microinjection Fish Mold</td>
			<td style="width:112px;">IBI Scientific</td>
			<td style="width:119px;">FM-600</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Borosilicate Glass with Filament</td>
			<td style="width:112px;">Sutter Instrument</td>
			<td style="width:119px;">BF100-50-10</td>
			<td>O.D.: 1.0 mm, I.D.: 0.50 mm, 10 cm length</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Flaming/Brown Micropipette Puller</td>
			<td style="width:112px;">Sutter Instrument</td>
			<td style="width:119px;">P-97</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Phenol Red</td>
			<td style="width:112px;">Sigma</td>
			<td style="width:119px;">P3532</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Jewelers Forceps, Durmont #5</td>
			<td style="width:112px;">Sigma</td>
			<td>F6521</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Scalpel Blade #15</td>
			<td style="width:112px;">Fisher</td>
			<td style="width:119px;">50-822-421</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Mineral oil</td>
			<td style="width:112px;">Sigma</td>
			<td style="width:119px;">M8410-500ML</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Microinjector</td>
			<td style="width:112px;">Narishige</td>
			<td style="width:119px;">IM-9B</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Magnetic Stand</td>
			<td style="width:112px;">Narishige</td>
			<td style="width:119px;">GJ-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Iron Plate</td>
			<td style="width:112px;">Narishige</td>
			<td style="width:119px;">IP</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Joystick Micromanipulator</td>
			<td style="width:112px;">Narishige</td>
			<td style="width:119px;">MN-151</td>
			<td></td>
		</tr>
	</tbody>
</table>

generation of transgenic hydra by embryo microinjection

As a member of the phylum Cnidaria, the sister group to all bilaterians, Hydra can shed light on fundamental biological processes shared among multicellular animals. Hydra is used as a model for the study of regeneration, pattern formation, and stem cells. However, research efforts have been hampered by lack of a reliable method for gene perturbations to study molecular function. The development of transgenic methods has revitalized the study of Hydra biology1. Transgenic Hydra allow for the tracking of live cells, sorting to yield pure cell populations for biochemical analysis, manipulation of gene function by knockdown and over-expression, and analysis of promoter function. Plasmid DNA injected into early stage embryos randomly integrates into the genome early in development. This results in hatchlings that express transgenes in patches of tissue in one or more of the three lineages (ectodermal epithelial, endodermal epithelial, or interstitial). The success rate of obtaining a hatchling with transgenic tissue is between 10% and 20%. Asexual propagation of the transgenic hatchling is used to establish a uniformly transgenic line in a particular lineage. Generating transgenic Hydra is surprisingly simple and robust, and here we describe a protocol that can be easily implemented at low cost.

Establishing transgenic Hydra lines
Feed transgenic hatchlings every 2-3 days with Artemia nauplii. Hatchlings sometimes do not eat for a day or two after hatching. Some new hatchlings will never eat, and thus will not survive. If the hatchling is transgenic in either the ectodermal (Figure 1A) or endodermal epithelial tissue, allow the animal to bud and collect the buds that have the most transgenic tissue (Figure 1B, C). Continue to d...

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Generation of Transgenic Hydra by Embryo Microinjection

Stably transgenic Hydra are made by microinjection of plasmid DNA into embryos followed by random genomic integration and asexual propagation to establish a uniform line. Transgenic Hydra are used to track cell movements, overexpress genes, study promoter function, or knock down gene expression using RNAi.

Generation of Transgenic Hydra by Embryo Microinjection

As a member of the phylum Cnidaria, the sister group to all bilaterians, Hydra can shed light on fundamental biological processes shared among ...

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13.9K Views.  Yale University School of Medicine. Stably transgenic Hydra are made by microinjection of plasmid DNA into embryos followed by random genomic integration and asexual propagation to establish a uniform line. Transgenic Hydra are used to track cell movements, overexpress genes, study promoter function, or knock down gene expression using RNAi. 

Video: Generation of Transgenic Hydra by Embryo Microinjection

Microinjection of A. aegypti Embryos to Obtain Transgenic Mosquitoes

In this video, Nijole Jasinskiene demonstrates the methodology employed to generate transgenic Aedes aegypti mosquitoes, which are vectors for dengue fever.  The techniques for correctly preparing microinjection needles, dessicating embryos, and performing microinjection are demonstrated.

In this video, Nijole Jasinskiene demonstrates the methodology employed to generate transgenic Aedes aegypti mosquitoes, which are vectors for dengue fever. The techniques for correctly preparing microinjection needles, dessicating embryos, and performing microinjection are demonstrated.

In this video, Nijole Jasinskiene demonstrates the methodology employed to generate transgenic Aedes aegypti mosquitoes, which are vectors for dengue ...

Generation of Stable Transgenic C. elegans Using Microinjection

Transgenic Caenorhabditis elegans can be readily created via microinjection of a DNA plasmid solution into the gonad 1. The plasmid DNA rearranges to form extrachromosomal concatamers that are stably inherited, though not with the same efficiency as actual chromosomes 2. A gene of interest is co-injected with an obvious phenotypic marker, such as rol-6 or GFP, to allow selection of transgenic animals under a dissecting microscope. The exogenous gene may be expressed from its native promoter for cellular localization studies. Alternatively, the transgene can be driven by a different tissue-specific promoter to assess the role of the gene product in that particular cell or tissue. This technique efficiently drives gene expression in all tissues of C. elegans except for the germline or early embryo 3. Creation of transgenic animals is widely utilized for a range of experimental paradigms. This video demonstrates the microinjection procedure to generate transgenic worms. Furthermore, selection and maintenance of stable transgenic C. elegans lines is described.

This video demonstrates the technique of microinjection into the gonad of C. elegans to create transgenic animals.

Transgenic Caenorhabditis elegans can be readily created via microinjection of a DNA plasmid solution into the gonad 1.  The plasmid DNA rearranges to ...

Microinjection Techniques for Studying Mitosis in the Drosophila melanogaster Syncytial Embryo

This protocol describes the use of the Drosophila melanogaster syncytial embryo for studying mitosis1. Drosophila has useful genetics with a sequenced genome, and it can be easily maintained and manipulated. Many mitotic mutants exist, and transgenic flies expressing functional fluorescently (e.g. GFP) - tagged mitotic proteins have been and are being generated. Targeted gene expression is possible using the GAL4/UAS system2. 

The Drosophila early embryo carries out multiple mitoses very rapidly (cell cycle duration, &asymp;10 min). It is well suited for imaging mitosis, because during cycles 10-13, nuclei divide rapidly and synchronously without intervening cytokinesis at the surface of the embryo in a single monolayer just underneath the cortex. These rapidly dividing nuclei probably use the same mitotic machinery as other cells, but they are optimized for speed; the checkpoint is generally believed to not be stringent, allowing the study of mitotic proteins whose absence would cause cell cycle arrest in cells with a strong checkpoint. Embryos expressing GFP labeled proteins or microinjected with fluorescently labeled proteins can be easily imaged to follow live dynamics (Fig. 1). In addition, embryos can be microinjected with function-blocking antibodies or inhibitors of specific proteins to study the effect of the loss or perturbation of their function3. These reagents can diffuse throughout the embryo, reaching many spindles to produce a gradient of concentration of inhibitor, which in turn results in a gradient of defects comparable to an allelic series of mutants. Ideally, if the target protein is fluorescently labeled, the gradient of inhibition can be directly visualized4. It is assumed that the strongest phenotype is comparable to the null phenotype, although it is hard to formally exclude the possibility that the antibodies may have dominant effects in rare instances, so rigorous controls and cautious interpretation must be applied. Further away from the injection site, protein function is only partially lost allowing other functions of the target protein to become evident.

Microinjection Techniques for Studying Mitosis in the Drosophila melanogaster Syncytial Embryo

This protocol describes the use of microinjection and high resolution imaging in the Drosophila melanogaster syncytial embryo to study mitosis.

This protocol describes the use of the Drosophila melanogaster syncytial embryo  for studying mitosis1.  Drosophila has useful genetics with a sequenced ...

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 ...

Generation of Transgenic C. elegans by Biolistic Transformation

The number of laboratories using the free living nematode C. elegans is rapidly growing. The popularity of this biological model is attributed to a rapid generation time and short life span, easy and inexpensive maintenance, fully sequenced genome, and array of RNAi resources and mutant animals. Additionally, analysis of the C. elegans genome revealed a great similarity between worms and higher vertebrates, which suggests that research in worms could be an important adjunct to studies performed in whole mice or cultured cells. A powerful and important part of worm research is the ability to use transgenic animals to study gene localization and function. Transgenic animals can be created either via microinjection of the worm germline or through the use of biolistic bombardment. Bombardment is a newer technique and is less familiar to a number of labs. Here we describe a simple protocol to generate transgenic worms by biolistic bombardment with gold particles using the Bio-Rad PDS-1000 system. Compared with DNA microinjection into hermaphrodite germline, this protocol has the advantage of not requiring special skills from the operator with regards to identifying worm anatomy or performing microinjection. Further multiple transgenic lines are usually obtained from a single bombardment. Also in contrast to microinjection, biolistic bombardment produces transgenic animals with both extrachromosomal arrays and integrated transgenes. The ability to obtain integrated transgenic lines can avoid the use of mutagenic protocols to integrate foreign DNA. In conclusion, biolistic bombardment can be an attractive method for the generation of transgenic animals, especially for investigators not interested in investing the time and effort needed to become skilled at microinjection.

Generation of Transgenic C. elegans by Biolistic Transformation

Transgenic worms are commonly used in C. elegans research. Described is a simple, yet effective, protocol to introduce transgenes into worms using biolistic bombardment with DNA-coated gold particles. The effort involved and results of bombardment compare favorably with microinjection for the generation of transgenic animals.

The number of laboratories using the free living nematode C. elegans is rapidly growing. The popularity of this biological model is attributed to a rapid ...

Analysis of mRNA Nuclear Export Kinetics in Mammalian Cells by Microinjection

In eukaryotes, messenger RNA (mRNA) is transcribed in the nucleus and must be exported into the cytoplasm to access the translation machinery. Although the nuclear export of mRNA has been studied extensively in Xenopus oocytes1 and genetically tractable organisms such as yeast2 and the Drosophila derived S2 cell line3, few studies had been conducted in mammalian cells. Furthermore the kinetics of mRNA export in mammalian somatic cells could only be inferred indirectly4,5. In order to measure the nuclear export kinetics of mRNA in mammalian tissue culture cells, we have developed an assay that employs the power of microinjection coupled with fluorescent in situ hybridization (FISH). These assays have been used to demonstrate that in mammalian cells, the majority of mRNAs are exported in a splicing dependent manner6,7, or in manner that requires specific RNA sequences such as the signal sequence coding region (SSCR) 6. In this assay, cells are microinjected with either in vitro synthesized mRNA or plasmid DNA containing the gene of interest. The microinjected cells are incubated for various time points then fixed and the sub-cellular localization of RNA is assessed using FISH. In contrast to transfection, where transcription occurs several hours after the addition of nucleic acids, microinjection of DNA or mRNA allows for rapid expression and allows for the generation of precise kinetic data.

Here we describe an assay that employs the power of microinjection coupled with fluorescent in situ hybridization in order to accurately measure the nuclear export kinetics of mRNA in mammalian somatic cells.

In eukaryotes, messenger RNA (mRNA) is transcribed in the nucleus and must be exported into the cytoplasm to access the translation machinery. Although ...

Analyzing the Function of Small GTPases by Microinjection of Plasmids into Polarized Epithelial Cells

Epithelial cells polarize their plasma membrane into biochemically and functionally distinct apical and basolateral domains where the apical domain faces the 'free' surfaces and the basolateral membrane is in contact with the substrate and neighboring cells. Both membrane domains are separated by tight junctions, which form a diffusion barrier. Apical-basolateral polarization can be recapitulated successfully in culture when epithelial cells such as Madin-Darby Canine Kidney (MDCK) cells are seeded at high density on polycarbonate filters and cultured for several days 1 2. Establishment and maintenance of cell polarity is regulated by an array of small GTPases of the Ras superfamily such as RalA, Cdc42, Rab8, Rab10 and Rab13 3 4 5 6 7. Like all GTPases these proteins cycle between an inactive GDP-bound state and an active GTP-bound state. Specific mutations in the nucleotide binding regions interfere with this cycling 8. For example, Rab13T22N is permanently locked in the GDP-form and thus dubbed 'dominant negative', whereas Rab13Q67L can no longer hydrolyze GTP and is thus locked in a 'dominant active' state 7. To analyze their function in cells both dominant negative and dominant active alleles of GTPases are typically expressed at high levels to interfere with the function of the endogenous proteins 9. An elegant way to achieve high levels of overexpression in a short amount of time is to introduce the plasmids encoding the relevant proteins directly into the nuclei of polarized cells grown on filter supports using microinjection technique. This is often combined with the co-injection of reporter plasmids that encode plasma membrane receptors that are specifically sorted to the apical or basolateral domain. A cargo frequently used to analyze cargo sorting to the basolateral domain is a temperature sensitive allele of the vesicular stomatitis virus glycoprotein (VSVGts045) 10. This protein cannot fold properly at 39&deg;C and will thus be retained in the endoplasmic reticulum (ER) while the regulatory protein of interest is assembled in the cytosol. A shift to 31&deg;C will then allow VSVGts045 to fold properly, leave the ER and travel to the plasma membrane 11. This chase is typically performed in the presence of cycloheximide to prevent further protein synthesis leading to cleaner results. Here we describe in detail the procedure of microinjecting plasmids into polarized cells and subsequent incubations including temperature shifts that allow a comprehensive analysis of regulatory proteins involved in basolateral sorting.

This article details the procedures involved in overexpression and analysis of small GTPases in polarized epithelial cells using microinjection technique.

Epithelial cells polarize their plasma membrane into biochemically and functionally distinct apical and basolateral domains where the apical domain faces ...

Activation of Apoptosis by Cytoplasmic Microinjection of Cytochrome c

Apoptosis, or programmed cell death, is a conserved and highly regulated pathway by which cells die1. Apoptosis can be triggered when cells encounter a wide range of cytotoxic stresses. These insults initiate signaling cascades that ultimately cause the release of cytochrome c from the mitochondrial intermembrane space to the cytoplasm2. The release of cytochrome c from mitochondria is a key event that triggers the rapid activation of caspases, the key cellular proteases which ultimately execute cell death3-4.
The pathway of apoptosis is regulated at points upstream and downstream of cytochrome c release from mitochondria5. In order to study the post-mitochondrial regulation of caspase activation, many investigators have turned to direct cytoplasmic microinjection of holocytochrome c (heme-attached) protein into cells6-9. Cytochrome c is normally localized to the mitochondria where attachment of a heme group is necessary to enable it to activate apoptosis10-11. Therefore, to directly activate caspases, it is necessary to inject the holocytochrome c protein instead of its cDNA, because while the expression of cytochrome c from cDNA constructs will result in mitochondrial targeting and heme attachment, it will be sequestered from cytosolic caspases. Thus, the direct cytosolic microinjection of purified heme-attached cytochrome c protein is a useful tool to mimic mitochondrial cytochrome c release and apoptosis without the use of toxic insults which cause cellular and mitochondrial damage.
In this article, we describe a method for the microinjection of cytochrome c protein into cells, using mouse embryonic fibroblasts (MEFs) and primary sympathetic neurons as examples. While this protocol focuses on the injection of cytochrome c for investigations of apoptosis, the techniques shown here can also be easily adapted for microinjection of other proteins of interest.

Activation of Apoptosis by Cytoplasmic Microinjection of Cytochrome c

In this protocol, we describe the direct cytoplasmic microinjection of cytochrome c protein into fibroblasts and primary sympathetic neurons. This technique allows for the introduction of cytochrome c protein into the cytoplasm of cells and mimics the release of cytochrome c from mitochondria, which occurs during apoptosis.

Apoptosis, or programmed cell death, is a conserved and highly regulated pathway by which cells die1.  Apoptosis can be triggered when cells encounter a ...

Generation of Myospheres From hESCs by Epigenetic Reprogramming

Generation of a homogeneous and abundant population of skeletal muscle cells from human embryonic stem cells (hESCs) is a requirement for cell-based therapies and for a "disease in a dish" model of human neuromuscular diseases. Major hurdles, such as low abundance and heterogeneity of the population of interest, as well as a lack of protocols for the formation of three-dimensional contractile structures, have limited the applications of stem cells for neuromuscular disorders. We have designed a protocol that overcomes these limits by ectopic introduction of defined factors in hESCs - the muscle determination factor MyoD and SWI/SNF chromatin remodeling complex component BAF60C - that are able to reprogram hESCs into skeletal muscle cells. Here we describe the protocol established to generate hESC-derived myoblasts and promote their clustering into tridimensional miniaturized structures (myospheres) that functionally mimic miniaturized skeletal muscles7.

Here, we describe a protocol based on epigenetic reprogramming of human embryonic stem cells (hESCs) toward generating a homogeneous population of skeletal muscle progenitors that under permissive culture conditions form three-dimensional clusters of contractile myofibers (myospheres), which recapitulate biological features of human skeletal muscles.

Generation of a homogeneous and abundant population of skeletal muscle cells from human embryonic stem cells (hESCs) is a requirement for cell-based ...

Culturing Caenorhabditis elegans in Axenic Liquid Media and Creation of Transgenic Worms by Microparticle Bombardment

In this protocol, we present the required materials, and the procedure for making modified&#160;C. elegans&#160;Habituation and Reproduction media (mCeHR). Additionally, the steps for exposing and acclimatizing C. elegans grown on E. coli to axenic liquid media are described. Finally, downstream experiments that utilize axenic C. elegans illustrate the benefits of this procedure. The ability to analyze and determine C. elegans&#160;nutrient requirement was illustrated by growing N2 wild type worms in axenic liquid media with varying heme concentrations. This procedure can be replicated with other nutrients to determine the optimal concentration for worm growth and development or, to determine the toxicological effects of drug treatments. The effects of varied heme concentrations on the growth of wild type worms were determined through qualitative microscopic observation and by quantitating the number of worms that grew in each heme concentration. In addition, the effect of varied nutrient concentrations can be assayed by utilizing worms that express fluorescent sensors that respond to changes in the nutrient of interest. Furthermore, a large number of worms were easily produced for the generation of transgenic C. elegans using microparticle bombardment.

Culturing Caenorhabditis elegans in Axenic Liquid Media and Creation of Transgenic Worms by Microparticle Bombardment

C. elegans is usually grown on solid agar plates or in liquid cultures seeded with E. coli. To prevent bacterial byproducts from confounding toxicological and nutritional studies, we utilized an axenic liquid medium, CeHR, to grow and synchronize a large number of worms for a range of downstream applications.

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Methods Article

Generation of Transgenic Hydra by Embryo Microinjection