Special thanks to James Copti for editing of the manuscript. We also gratefully acknowledge funding to JN from the German Research foundation (DFG) by the SFB 870 and SPP &#8220;Integrative Analysis of Olfaction&#8221; and SPP 1738 &#8220;Emerging roles of non-coding RNAs in nervous system development, plasticity &#38; disease&#8221;, SPP1757 &#8220;Glial heterogeneity&#8221;, and Excellence Strategy within the framework of the Munich Cluster for Systems Neurology (EXC 2145 SyNergy &#8211; ID 390857198).

All animals used in this protocol were kept under standard husbandry conditions, and experiments have been performed according to the handling guidelines and regulations of EU and the Government of Upper Bavaria (AZ 55.2-1-54-2532-0916).
1. Preparation of Plasmid Mixture for Electroporation
<ol>
	<li>Dilute the plasmid of interest in sterile water and add fast green stain stock solution [1 mg/mL]. Make sure that the final concentration of the plasmid is&#160; &#8764;1 &#181;g/&#181;L. Add th...

<ol>
	<li>Kaslin, J., Ganz, J., Brand, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proliferation,+neurogenesis+and+regeneration+in+the+non-mammalian+vertebrate+brain.">Proliferation, neurogenesis and regeneration in the non-mammalian vertebrate brain.</a> Philosophical Transactions of the Royal Society of London Series B Biological Sciences. 363 (1489), 101-122 (2008).</li><li>Baumgart, E. V., Barbosa, J. S., Bally-Cuif, L., Gotz, M., Ninkovic, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stab+wound+injury+of+the+zebrafish+telencephalon:+a+model+for+comparative+analysis+of+reactive+gliosis.">Stab wound injury of the zebrafish telencephalon: a model for comparative analysis of reactive gliosis.</a> Glia. 60 (3), 343-357 (2012).</li><li>Barbosa, 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=Live+imaging+of+adult+neural+stem+cell+behavior+in+the+intact+and+injured+zebrafish+brain.">Live imaging of adult neural stem cell behavior in the intact and injured zebrafish brain.</a> Science. 346 (6236), 789-793 (2015).</li><li>Kishimoto, N., Shimizu, K., Sawamoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+regeneration+in+a+zebrafish+model+of+adult+brain+injury.">Neuronal regeneration in a zebrafish model of adult brain injury.</a> Disease Model and Mechanisms. 5 (2), 200-209 (2012).</li><li>Kroehne, V., Freudenreich, D., Hans, S., Kaslin, J., Brand, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regeneration+of+the+adult+zebrafish+brain+from+neurogenic+radial+glia-type+progenitors.">Regeneration of the adult zebrafish brain from neurogenic radial glia-type progenitors.</a> Development. 138 (22), 4831-4841 (2011).</li><li>Marz, M., Schmidt, R., Rastegar, S., Strahle, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regenerative+response+following+stab+injury+in+the+adult+zebrafish+telencephalon.">Regenerative response following stab injury in the adult zebrafish telencephalon.</a> Developmental Dynamics. 240 (9), 2221-2231 (2011).</li><li>Ayari, B., Elhachimi, K. H., Yanicostas, C., Landoulsi, A., Soussi-Yanicostas, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prokineticin+2+expression+is+associated+with+neural+repair+of+injured+adult+zebrafish+telencephalon.">Prokineticin 2 expression is associated with neural repair of injured adult zebrafish telencephalon.</a> Journal of Neurotrauma. , (2010).</li><li>Skaggs, K., Goldman, D., Parent, J. 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A., Talbot, W. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glial+cell+development+and+function+in+zebrafish.">Glial cell development and function in zebrafish.</a> Cold Spring Harbor Perspectives in Biology. 7 (2), a020586 (2014).</li><li>Obermann, 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=The+Surface+Proteome+of+Adult+Neural+Stem+Cells+in+Zebrafish+Unveils+Long-Range+Cell-Cell+Connections+and+Age-Related+Changes+in+Responsiveness+to+IGF.">The Surface Proteome of Adult Neural Stem Cells in Zebrafish Unveils Long-Range Cell-Cell Connections and Age-Related Changes in Responsiveness to IGF.</a> Stem Cell Reports. 12 (2), 258-273 (2019).</li><li>Progatzky, F., Dallman, M. J., Lo Celso, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+seeing+to+believing:+labelling+strategies+for+in+vivo+cell-tracking+experiments.">From seeing to believing: labelling strategies for in vivo cell-tracking experiments.</a> Interface Focus. 3 (3), 20130001 (2013).</li><li>Kusumanto, Y. 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=Improvement+of+in+vivo+transfer+of+plasmid+DNA+in+muscle:+comparison+of+electroporation+versus+ultrasound.">Improvement of in vivo transfer of plasmid DNA in muscle: comparison of electroporation versus ultrasound.</a> Drug Delivery. 14 (5), 273-277 (2007).</li><li>Zou, M., De Koninck, P., Neve, R. L., Friedrich, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+gene+transfer+into+the+adult+zebrafish+brain+by+herpes+simplex+virus+1+(HSV-1)+and+electroporation:+methods+and+optogenetic+applications.">Fast gene transfer into the adult zebrafish brain by herpes simplex virus 1 (HSV-1) and electroporation: methods and optogenetic applications.</a> Frontiers in Neural Circuits. 8 (41), (2014).</li><li>Van Tendeloo, V. F., 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=Highly+efficient+gene+delivery+by+mRNA+electroporation+in+human+hematopoietic+cells:+superiority+to+lipofection+and+passive+pulsing+of+mRNA+and+to+electroporation+of+plasmid+cDNA+for+tumor+antigen+loading+of+dendritic+cells.">Highly efficient gene delivery by mRNA electroporation in human hematopoietic cells: superiority to lipofection and passive pulsing of mRNA and to electroporation of plasmid cDNA for tumor antigen loading of dendritic cells.</a> Blood. 98 (1), 49-56 (2001).</li><li>Mars, T., 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=Electrotransfection+and+lipofection+show+comparable+efficiency+for+in+vitro+gene+delivery+of+primary+human+myoblasts.">Electrotransfection and lipofection show comparable efficiency for in vitro gene delivery of primary human myoblasts.</a> The Journal of Membrane Biology. 248 (2), 273-283 (2015).</li><li>Barbosa, J. S., Di Giaimo, R., Gotz, M., Ninkovic, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-cell+in+vivo+imaging+of+adult+neural+stem+cells+in+the+zebrafish+telencephalon.">Single-cell in vivo imaging of adult neural stem cells in the zebrafish telencephalon.</a> Nature Protocols. 11 (8), 1360-1370 (2016).</li><li>Di Giaimo, R., 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+Aryl+Hydrocarbon+Receptor+Pathway+Defines+the+Time+Frame+for+Restorative+Neurogenesis.">The Aryl Hydrocarbon Receptor Pathway Defines the Time Frame for Restorative Neurogenesis.</a> Cell Reports. 25 (12), 3241-3251 (2018).</li><li>Breunig, C. T., 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=One+step+generation+of+customizable+gRNA+vectors+for+multiplex+CRISPR+approaches+through+string+assembly+gRNA+cloning+(STAgR).">One step generation of customizable gRNA vectors for multiplex CRISPR approaches through string assembly gRNA cloning (STAgR).</a> PLoS One. 13 (4), e0196015 (2018).</li><li>Barbosa, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> In vivo single cell analysis reveals distinct behavior of neural stem and progenitor cells in homeostasis and regeneration in the adult brain. , (2014).</li><li>Kelsh, R. N., 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=Zebrafish+pigmentation+mutations+and+the+processes+of+neural+crest+development.">Zebrafish pigmentation mutations and the processes of neural crest development.</a> Development. 123, 369-389 (1996).</li><li>Torper, O., 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+Vivo+Reprogramming+of+Striatal+NG2+Glia+into+Functional+Neurons+that+Integrate+into+Local+Host+Circuitry.">In Vivo Reprogramming of Striatal NG2 Glia into Functional Neurons that Integrate into Local Host Circuitry.</a> Cell Reports. 12 (3), 474-481 (2015).</li><li>Nguyen, L. T., Atobe, K., Barichello, J. M., Ishida, T., Kiwada, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complex+formation+with+plasmid+DNA+increases+the+cytotoxicity+of+cationic+liposomes.">Complex formation with plasmid DNA increases the cytotoxicity of cationic liposomes.</a> Biological and Pharmaceutical Bulletin. 30 (4), 751-757 (2007).</li><li>Chapouton, P., Godinho, L., Detrich, H. W., Westerfield, M., Zon, 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> Neurogenesis. Chapter IV in The Zebrafish: Cellular and Developmental Biology, Part A Developmental Biology. 100, (2010).</li><li>Zhu, 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=Optogenetic+Dissection+of+Neuronal+Circuits+in+Zebrafish+using+Viral+Gene+Transfer+and+the+Tet+System.">Optogenetic Dissection of Neuronal Circuits in Zebrafish using Viral Gene Transfer and the Tet System.</a> Frontiers in Neural Circuits. 3 (21), (2009).</li></ol>

This electroporation protocol is a reliable in vivo method of labelling individual ependymoglial cells. The protocol may need a further adaptation to label other cell types such as neurons or oligodendrocytes. To achieve successful labelling, plasmids containing different promoters can be used. Chicken-beta actin promoter, eF1alpha, CMV and ubiquitin promoter have been previously used to drive the expression of different transgenes in ependymoglia and their progeny23. However, different kinetics o...

Zebrafish are excellent animal models to examine brain regeneration after a stab wound injury. In comparison to mammals, on the evolutionary ladder, less evolved species such as zebrafish generally show higher rates of constitutive neurogenesis and broader areas of adult neural stem cell residence, leading to constant generation of new neurons throughout most brain areas in the adult life. This feature appears to correlate with significantly higher regenerative capacity of zebrafish in comparison to mammals1, as zebrafish have remarkable potential to efficiently generate new neurons in most brain injury models studied2,3,4,5,6,7,8. Here, the zebrafish telencephalon is studied, since it is a brain area with prominent neurogenesis in adulthood. These zones of adult neurogenesis are homologous to neurogenic zones in the adult mammalian brain9,10,11.
Abundant neurogenic areas in the zebrafish telencephalon are present due to the existence of radial glia like cells or ependymoglia cells. Ependymoglial cells act as resident adult neural stem cells and are responsible for generation of new neurons in both the intact and regenerating brain3,5. Lineage tracing experiments have shown that ventricular ependymoglia react to injury, then proliferate and generate new neuroblasts that migrate to the lesion site5. Due to the everted nature of zebrafish telencephalon, ependymoglial cells line the ventricular surface and build the ventral ventricular wall. The dorsal ventricular wall is formed by a dorsal ependymal cell layer (Figure 1A). Importantly, zebrafish ependymoglia embody the characteristics of both mammalian radial glia and ependymal cells. Long radial processes are a typical feature of radial glia cells, whereas cellular extensions and tight junctions (as well as their ventricular positions) are typical features of ependymal cells12,13,14. Therefore, these cells are referred to as ependymoglial cells.
To follow in vivo behavior of single ependymoglial cells during regeneration, they need to be reliably labeled. Various methods of in vivo cell labeling for fluorescent microscopy have been previously described, such as endogenous reporters or lipophilic dyes15. These methods, in contrast to electroporation, may require longer periods of time and often do not offer the possibility of single cell labeling or permanent long-term tracing. Electroporation, however (besides single cell labeling), offers the possibility of introducing new DNA into the host cell. Moreover, compared to other methods of DNA transfer into the cells, electroporation has been demonstrated to be one of the most efficient methods16,17,18,19.
Presented here is an electroporation protocol that has been refined for the purpose of labeling single ependymoglial cells in the adult zebrafish telencephalon. This protocol allows for the labelling of single ependymoglial cells in order to follow them over a long-term period20 or to manipulate specific pathways in a cell-autonomous manner21,22.

<table>
	<tbody>
		<tr>
			<td>Reagent/Material</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fast Green</td>
			<td>Sigma-Aldrich</td>
			<td>F7258-25G</td>
			<td>For coloring plasmid solution</td>
		</tr>
		<tr>
			<td>MS222</td>
			<td>Sigma-Aldrich</td>
			<td>A5040-25G</td>
			<td>MS222 should be stored at RT (up to two weeks) and protected from light</td>
		</tr>
		<tr>
			<td>Ultrasound gel</td>
			<td>SignaGel, Parker laboratories INC.</td>
			<td>15-60</td>
			<td>Electrode Gel</td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Air pump</td>
			<td>TetraTec APS 50, 10l-60l</td>
			<td></td>
			<td>Can be bought in the pet shops</td>
		</tr>
		<tr>
			<td>BTX Tweezertrodes Electrodes</td>
			<td>Platinum Tweezertrode, BTX Harvard Apparatus</td>
			<td>45-0486</td>
			<td>1mm diameter</td>
		</tr>
		<tr>
			<td>Electroporation device</td>
			<td>BTX ECM830 Square Wave Electroporation System, BTX Harvard Apparatus</td>
			<td>45-0662</td>
			<td></td>
		</tr>
		<tr>
			<td>Injection device</td>
			<td>FemtoJet 4i, Eppendorf</td>
			<td>5252000013</td>
			<td></td>
		</tr>
		<tr>
			<td>Standard Wall Borosillicate Glass Capillary</td>
			<td>Warner Instruments</td>
			<td>64-0766</td>
			<td>Model No: G100-4</td>
		</tr>
		<tr>
			<td>Microloader tips</td>
			<td>Eppendorf</td>
			<td>5242956003</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro-knife</td>
			<td>Fine Science Tools</td>
			<td>10056-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Joystick micromanipulator</td>
			<td>Narishige Japan</td>
			<td>MN - 151</td>
			<td></td>
		</tr>
		<tr>
			<td>Needle holder</td>
			<td>FemtoJet 4i, Eppendorf</td>
			<td>5252000013</td>
			<td>Needle holder comes together with the injection device</td>
		</tr>
		<tr>
			<td>Needle pulling device</td>
			<td>Narishige Japan</td>
			<td>Model No: PC-10</td>
			<td>The PC-10 was discontinued by Narishige in 2017 and replaced by the PC-100</td>
		</tr>
		<tr>
			<td>Petri dishes</td>
			<td>Greiner Bio-One International</td>
			<td>633161</td>
			<td></td>
		</tr>
	</tbody>
</table>

electroporation method for in vivo delivery of plasmid dna in the adult zebrafish telencephalon

Electroporation is a transfection method in which an electrical field is applied to cells to create temporary pores in a cell membrane and increase its permeability, thereby allowing different molecules to be introduced to the cell. In this paper, electroporation is used to introduce plasmids to ependymoglial cells, which line the ventricular zone of the adult zebrafish telencephalon. A fraction of these cells shows stem cell properties and generates new neurons in the zebrafish brain; therefore, studying their behavior is essential to determine their roles in neurogenesis and regeneration. The introduction of plasmids via electroporation enables long-term labeling and tracking of a single ependymoglial cell. Furthermore, plasmids such as Cre recombinase or Cas9 can be delivered to single ependymoglial cells, which enables gene recombination or gene editing and provides a unique opportunity to assess the cell&#8217;s autonomous gene function in a controlled, natural environment. Finally, this detailed, step-by-step electroporation protocol is used to obtain successful introduction of plasmids into a large number of single ependymoglial cells.

The described electroporation method allows delivery of plasmid DNA into ependymoglial cells, which are located superficially in the zebrafish telencephalon and just under the dorsal ependymal cell layer (Figure 1A).
If the result of electroporation is positive, labeled single ependymoglial cells (red cells in Figure 2A,B) can be observed among other ependymoglial cells (white in <s...

Watch this Scientific Journal Video about Electroporation Method for In Vivo Delivery of Plasmid DNA in the Adult Zebrafish Telencephalon at JoVE.com

Electroporation Method for In Vivo Delivery of Plasmid DNA in the Adult Zebrafish Telencephalon

Presented here is an electroporation method for plasmid DNA delivery and ependymoglial cell labeling in the adult zebrafish telencephalon. This protocol is a quick and efficient method to visualize and trace individual ependymoglial cells and opens up new possibilities to apply electroporation to a broad range of genetic manipulations.

Electroporation is a transfection method in which an electrical field is applied to cells to create temporary pores in a cell membrane and increase its ...

This protocol allows the labeling of individual ependymoglial cells in the zebrafish telencephalon to enable their long-term monitoring, as well as the manipulation of specific pathways in a cell-autonomous manner. The main advantage of this technique is that it allows single cell labeling in fast and efficient way, as well as gene editing and signaling pathway manipulation in cell-autonomous manner. This method allows the investigation of basic cell biology questions, for example, about cell delamination, the maintenance of epithelial homeostasis, and the symmetry of cell division.Begin by using a needle-pulling apparatus to prepare glass capillaries. Use microloader tips to fill a prepared glass capillary with ten microliters of plasmid solution. Then press menu change capillary"on the injection device to allow the needle to be loaded into the needle holder.Then switch the injection device from change capillary to inject mode. Then, using a stereomicroscope with a four times magnification, and Finden forceps, cut only the tip of the capillary. Then apply pressure to the foot pedal to confirm that the plasmid solutions runs easily out of the needle without hindrance.When the needle is ready, transfer a zebrafish from the husbandry tank to a container of anesthetic solution. And wait a few minutes until the movement of the gills subsides. Press the sedated fish dorsal side up onto a pre-wetted sponge under the stereomicroscope, and use a stainless steel dissecting microknife with a 40 millimeter cutting edge and a 0.5 millimeter thickness to carefully create a small hole in the fish skull at the posterior side of the telencephalon, just next to the border of the optic tectum.Tilt the fish as necessary and orient the tip of the glass capillary towards the skull in the correct angle to facilitate penetration of the capillary tip through the hole. Then, very carefully insert the tip of the capillary into the hole through the dorsal ependymal cell layer, until it reaches the telencephalic ventricle, and apply pressure to the foot pedal for about 10 seconds to deliver approximately 1 microliter of the plasmid solution. The success of the delivery can be confirmed by observing the spreading of the green liquid throughout the ventricle.Cover the fish telencephalon with a small amount of ultrasound gel. For electroporation of the plasmid injected animal, remove the sponge from the injection set-up and immerse the inner side of the electrotips into ultrasound gel. Position the fish head between the electrodes, with the positive electrode at the ventral side of the head and the negative electrode on the dorsal side.Then, while still holding the fish's body in the sponge, press the electrodes gently and precisely against the telencephalon and administer the current with the foot pedal, holding the electrodes in place until all five pulses are finished. If the electroporation is successful, plasmid labeled single ependymoglial cells can be observed among the non-plasmid labeled ependymoglial cells. Depending on the efficiency of the electroporation process, a higher or lower number of ependymoglial cells may be labeled.Nevertheless, the demonstrated protocol yields a higher number of labeled cells than previously published protocols. Note that the highest density of labeled cells tends to emerge mostly at the inner ventricular side of both hemispheres due to the way in which the injected plasmid liquid distributes between the hemispheres. In this video, one hemisphere of the zebrafish telencephalon is presented in 3D, where the ependymoglial cells with radio-processes, are in magenta when observed from the side.Through co-electroporation with another plasmid that labels nuclei, cell division of ependymoglial cells can be observed. Unsuccessful electroporation results in very low number or no labeled ependymoglial cells. Dorsal ependymal cells, however, are the most likely to be labeled.Their soma is larger in cuboid and they do not possess radio-elongated processes as evident from a side view of the ependymoglial cell layer. tdTomato-mem labeled cells are most likely ependymal cells, which are located above the layer of ependymoglia. In contrast, the introduction of a tdTomato-mem expressing plasmid to individual ependmyoglial cells results in tdTomato-mem expression in addition to the initial cell labeling.The most important things to remember are to cut only the tip of the capillary and to penetrate the ependymal layer while injecting so that the liquid spreads throughout the ventricle. This technique enables the long-term monitoring of single ependymoglial cells through in vivo imaging, and therefore establishing their role in brain regeneration as well as their vast in vivo genetic link.

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JoVE Journal

Developmental Biology

9.5K Views.  Helmholtz Zentrum München. This protocol allows the labeling of individual ependymoglial cells in the zebrafish telencephalon to enable their long-term monitoring, as well as the manipulation of specific pathways in a cell-autonomous manner. The main advantage of this technique is that it allows single cell labeling in fast and efficient way, as well as gene editing and signaling pathway manipulation in cell-autonomous manner. This method allows the investigation of basic cell biology questions, for example, about cell...

Video: Electroporation Method for In Vivo Delivery of Plasmid DNA in the Adult Zebrafish Telencephalon

Kidney Regeneration in Adult Zebrafish by Gentamicin Induced Injury

The kidney is essential for fluid homeostasis, blood pressure regulation and filtration of waste from the body. The fundamental unit of kidney function is the nephron. Mammals are able to repair existing nephrons after injury, but lose the ability to form new nephrons soon after birth. In contrast to mammals, adult fish produce new nephrons (neonephrogenesis) throughout their lives in response to growth requirements or injury. Recently, lhx1a has been shown to mark nephron progenitor cells in the adult zebrafish kidney, however mechanisms controlling the formation of new nephrons after injury remain unknown. Here we show our method for robust and reproducible injury in the adult zebrafish kidney by intraperitoneal (i.p.) injection of gentamicin, which uses a noninvasive visual screening process to select for fish with strong but nonlethal injury. Using this method, we can determine optimal gentamicin dosages for injury and go on to demonstrate the effect of higher temperatures on kidney regeneration in zebrafish.

Here we present a reliable method to study adult kidney regeneration by inducing acute kidney injury by gentamicin injection. We show that injury is dependent on gentamicin dosage and environmental temperature using in situ hybridization to label lhx1a+ developing new nephrons.

The kidney is essential for fluid homeostasis, blood pressure regulation and filtration of waste from the body. The fundamental unit of kidney function is ...

Analysis of Zebrafish Larvae Skeletal Muscle Integrity with Evans Blue Dye

The zebrafish model is an emerging system for the study of neuromuscular disorders. In the study of neuromuscular diseases, the integrity of the muscle membrane is a critical disease determinant. To date, numerous neuromuscular conditions display degenerating muscle fibers with abnormal membrane integrity; this is most commonly observed in muscular dystrophies. Evans Blue Dye (EBD) is a vital, cell permeable dye that is rapidly taken into degenerating, damaged, or apoptotic cells; in contrast, it is not taken up by cells with an intact membrane. EBD injection is commonly employed to ascertain muscle integrity in mouse models of neuromuscular diseases. However, such EBD experiments require muscle dissection and/or sectioning prior to analysis. In contrast, EBD uptake in zebrafish is visualized in live, intact preparations. Here, we demonstrate a simple and straightforward methodology for performing EBD injections and analysis in live zebrafish. In addition, we demonstrate a co-injection strategy to increase efficacy of EBD analysis. Overall, this video article provides an outline to perform EBD injection and characterization in zebrafish models of neuromuscular disease.

In this study, we describe a straightforward method to perform Evans Blue Dye (EBD) analysis on zebrafish larvae. This technique is a powerful tool for the characterization of skeletal muscle integrity and delineation of zebrafish models of muscular dystrophy, and is a valuable method for the development of novel therapeutics.

The zebrafish model is an emerging system for the study of neuromuscular disorders.  In the study of neuromuscular diseases, the integrity of the muscle ...

Gene Transfer into the Chicken Auditory Organ by In Ovo Micro-electroporation

Chicken embryos are ideal model systems for studying embryonic development as manipulations of gene function can be conducted with relative ease in ovo. The inner ear auditory sensory organ is critical for our ability to hear. It houses a highly specialized sensory epithelium that consists of mechano-transducing hair cells (HCs) and surrounding glial-like supporting cells (SCs). Despite structural differences in the auditory organs, molecular mechanisms regulating the development of the auditory organ are evolutionarily conserved between mammals and aves. In ovo electroporation is largely limited to early stages at E1 - E3. Due to the relative late development of the auditory organ at E5, manipulations of the auditory organ by in ovo electroporation past E3 are difficult due to the advanced development of the chicken embryo at later stages. The method presented here is a transient gene transfer method for targeting genes of interest at stage E4 - E4.5 in the developing chicken auditory sensory organ via in ovo micro-electroporation. This method is applicable for gain- and loss-of-functions with conventional plasmid DNA-based expression vectors and can be combined with in ovo cell proliferation assay by adding EdU (5-ethynyl-2&#180;-deoxyuridine) to the whole embryo at the time of electroporation. The use of green or red fluorescent protein (GFP or RFP) expression plasmids allows the experimenter to quickly determine whether the electroporation successfully targeted the auditory portion of the developing inner ear. In this method paper, representative examples of GFP electroporated specimens are illustrated; embryos were harvested 18 - 96 hr&#160;after electroporation and targeting of GFP to the pro-sensory area of the auditory organ was confirmed by RNA in situ hybridization. The method paper also provides an optimized protocol for the use of the thymidine analog EdU to analyze cell proliferation; an example of an EdU based cell proliferation assay that combines immuno-labeling and click EdU chemistry is provided.

Gene Transfer into the Chicken Auditory Organ by In Ovo Micro-electroporation

The auditory organ mediates hearing. Here we present a modified in ovo micro-electroporation method optimized for studying auditory progenitor cell proliferation and differentiation in the developing chicken auditory organ.

Chicken embryos are ideal model systems for studying embryonic development as manipulations of gene function can be conducted with relative ease in ovo. ...

In Vivo Imaging of Transgenic Gene Expression in Individual Retinal Progenitors in Chimeric Zebrafish Embryos to Study Cell Nonautonomous Influences

The genetic and technical strengths have made the zebrafish vertebrate a key model organism in which the consequences of gene manipulations can be traced in vivo throughout the rapid developmental period. Multiple processes can be studied including cell proliferation, gene expression, cell migration and morphogenesis. Importantly, the generation of chimeras through transplantations can be easily performed, allowing mosaic labeling and tracking of individual cells under the influence of the host environment. For example, by combining functional gene manipulations of the host embryo (e.g., through morpholino microinjection) and live imaging, the effects of extrinsic, cell nonautonomous signals (provided by the genetically modified environment) on individual transplanted donor cells can be assessed. Here we demonstrate how this approach is used to compare the onset of fluorescent transgene expression as a proxy for the timing of cell fate determination in different genetic host environments.
In this article, we provide the protocol for microinjecting zebrafish embryos to mark donor cells and to cause gene knockdown in host embryos, a description of the transplantation technique used to generate chimeric embryos, and the protocol for preparing and running in vivo time-lapse confocal imaging of multiple embryos. In particular, performing multiposition imaging is crucial when comparing timing of events such as the onset of gene expression. This requires data collection from multiple control and experimental embryos processed simultaneously. Such an approach can easily be extended for studies of extrinsic influences in any organ or tissue of choice accessible to live imaging, provided that transplantations can be targeted easily according to established embryonic fate maps.

In Vivo Imaging of Transgenic Gene Expression in Individual Retinal Progenitors in Chimeric Zebrafish Embryos to Study Cell Nonautonomous Influences

Live tracking of individual WT retinal progenitors in distinct genetic backgrounds allows for the assessment of the contribution of cell non-autonomous signaling during neurogenesis. Here, a combination of gene knockdown, chimera generation via embryo transplantation and in vivo time-lapse confocal imaging was utilized for this purpose.

The genetic and technical strengths have made the zebrafish vertebrate a key model organism in which the consequences of gene manipulations can be traced ...

In Ovo Electroporation in the Chicken Auditory Brainstem

Electroporation is a method that introduces genes of interest into biologically relevant organisms like the chicken embryo. It is long established that the chicken embryo is an effective research model for studying basic biological functions of auditory system development. More recently, the chicken embryo has become particularly valuable in studying gene expression, regulation and function associated with hearing. In ovo electroporation can be used to target auditory brainstem regions responsible for highly specialized auditory functions. These regions include the chicken nucleus magnocellularis (NM) and nucleus laminaris (NL). NM and NL neurons arise from distinct precursors of rhombomeres 5 and 6 (R5/R6). Here, we present in ovo electroporation of plasmid-encoded genes to study gene-related properties in these regions. We show a method for spatial and temporal control of gene expression that promote either gain or loss of functional phenotypes. By targeting auditory neural progenitor regions associated with R5/R6, we show plasmid transfection in NM and NL. Temporal regulation of gene expression can be achieved by adopting a tet-on vector system. This is a drug inducible procedure that expresses the genes of interest in the presence of doxycycline (Dox). The in ovo electroporation technique &#8211; together with either biochemical, pharmacological, and or in vivo functional assays &#8211; provides an innovative approach to study auditory neuron development and associated pathophysiological phenomena.

In Ovo Electroporation in the Chicken Auditory Brainstem

Auditory brainstem neurons of avians and mammals are specialized for fast neural encoding, a fundamental process for normal hearing functions. These neurons arise from distinct precursors of embryonic hindbrain. We present techniques utilizing electroporation to express genes in the hindbrain of chicken embryos to study gene function during auditory development.

Electroporation is a method that introduces genes of interest into biologically relevant organisms like the chicken embryo. It is long established that ...

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the proteins involved in these pathways are evolutionarily conserved between mammals and other eukaryotes, such as the fruit fly Drosophila melanogaster, suggesting that similar organizing principles exist during the development of these organisms. Importantly, Drosophila has been used extensively to identify cellular and molecular mechanisms regulating processes that are required in mammals including neurogenesis, differentiation, axonal guidance, and synaptogenesis. Flies have also been used successfully to model a variety of human neurodevelopmental diseases. Here we describe a protocol for the step-by-step microdissection, fixation, and immunofluorescent localization of proteins within the adult Drosophila brain. This protocol focuses on two example neuronal populations, mushroom body neurons and retinal photoreceptors, and includes optional steps to trace individual mushroom body neurons using Mosaic Analysis with a Repressible Cell Marker (MARCM) technique. Example data from both wild-type and mutant brains are shown along with a brief description of a scoring criteria for axonal guidance defects. While this protocol highlights two well-established antibodies for investigating the morphology of mushroom body and photoreceptor neurons, other Drosophila brain regions and the localization of proteins within other brain regions can also be investigated using this protocol.

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

This protocol describes the dissection and immunostaining of adult Drosophila melanogaster brain tissues. Specifically, this protocol highlights the use of Drosophila mushroom body and photoreceptor neurons as example neuronal subsets that can be accurately used to uncover general principles underlying many aspects of neuronal development.

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the ...

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

Studying the cell biological processes during converting the identities of specific cell types provides important insights into mechanism that maintain and protect cellular identities. The conversion of germ cells into specific neurons in the nematode Caenorhabditis elegans (C. elegans) is a powerful tool for performing genetic screens in order to dissect regulatory pathways that safeguard established cell identities. Reprogramming of germ cells to a specific type of neurons termed ASE requires transgenic animals that allow broad over-expression of the Zn-finger transcription factor (TF) CHE-1. Endogenous CHE-1 is expressed exclusively in two head neurons and is required to specify the glutamatergic ASE neurons fate, which can easily be visualized by the gcy-5prom::gfp reporter. A trans gene containing the heat-shock promoter-driven che-1 gene expression construct allows broad mis-expression of CHE-1 in the entire animal upon heat-shock treatment. The combination of RNAi against the chromatin-regulating factor LIN-53 and heat-shock-induced che-1 over-expression leads to reprogramming of germ cell into ASE neuron-like cells. We describe here the specific RNAi procedure and appropriate conditions for heat-shock treatment of transgenic animals in order to successfully induce germ cell to neuron conversion.

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

This protocol describes how to study cellular processes during cell fate conversion in Caenorhabditis elegans in vivo. Using transgenic animals, allowing heat-shock promoter-driven overexpression of the neuron fate-inducing transcription factor CHE-1 and RNAi-mediated depletion of the chromatin-regulating factor LIN-53 germ cell to neuron reprogramming can be observed in vivo.

Studying the cell biological processes during converting the identities of specific cell types provides important insights into mechanism that maintain ...

Nanoparticle-mediated siRNA Gene-silencing in Adult Zebrafish Heart

Mammals have a very limited capacity to regenerate the heart after myocardial infarction. On the other hand, the adult zebrafish regenerates its heart after apex resection or cryoinjury, making it an important model organism for heart regeneration study. However, the lack of loss-of-function methods for adult organs has restricted insights into the mechanisms underlying heart regeneration. RNA interference via different delivery systems is a powerful tool for silencing genes in mammalian cells and model organisms. We have previously reported that siRNA-encapsulated nanoparticles successfully enter cells and result in a remarkable gene-specific knockdown in the regenerating adult zebrafish heart. Here, we present a simple, rapid, and efficient protocol for the dendrimer-mediated siRNA delivery and gene-silencing in the regenerating adult zebrafish heart. This method provides an alternative approach for determining gene functions in adult organs in zebrafish and can be extended to other model organisms as well.

It remains a major challenge to develop conditional gene-knockout or effective gene-knockdown in adult zebrafish organs. Here we report a protocol for performing nanoparticle-mediated siRNA gene-silencing in adult zebrafish heart, thus providing a new loss-of-function method for studying adult organs in zebrafish and other model organisms.

Mammals have a very limited capacity to regenerate the heart after myocardial infarction. On the other hand, the adult zebrafish regenerates its heart ...

Adult Zebrafish Injury Models to Study the Effects of Prednisolone in Regenerating Bone Tissue

Zebrafish are able to regenerate various organs, including appendages (fins) after amputation. This involves the regeneration of bone, which regrows within roughly two weeks after injury. Furthermore, zebrafish are able to heal bone rapidly after trepanation of the skull, and repair fractures that can be easily introduced into zebrafish bony fin rays. These injury assays represent feasible experimental paradigms to test the effect of administered drugs on rapidly forming bone. Here, we describe the use of these 3 injury models and their combined use with systemic glucocorticoid treatment, which exerts bone inhibitory and immunosuppressive effects. We provide a workflow on how to prepare for immunosuppressive treatment in adult zebrafish, illustrate how to perform fin amputation, trepanation of calvarial bones, and fin fractures, and describe how the use of glucocorticoids affects both bone forming osteoblasts and cells of the monocyte/macrophage lineage as part of innate immunity in bone tissue.

Here, we describe 3 adult zebrafish injury models and their combined use with immunosuppressive drug treatment. We provide guidance on imaging of regenerating tissues and on detecting bone mineralization therein.

Zebrafish are able to regenerate various organs, including appendages (fins) after amputation. This involves the regeneration of bone, which regrows ...

An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity

Spermatogenesis is the development of spermatogonia into mature spermatozoa in the seminiferous tubules of the testis. This process is supported by Sertoli cell junctions at the blood-testis barrier (BTB), which is the tightest tissue barrier in the mammalian body and segregates the seminiferous epithelium into two compartments, a basal and an adluminal. The BTB creates a unique microenvironment for germ cells in meiosis I/II and for the development of postmeiotic spermatids into spermatozoa via spermiogenesis. Here, we describe a reliable assay to monitor BTB integrity of mouse testis in vivo. An intact BTB blocks the diffusion of FITC-conjugated inulin from the basal to the apical compartment of the seminiferous tubules. This technique is suitable for studying gene candidates, viruses, or environmental toxicants that may affect BTB function or integrity, with an easy procedure and a minimal requirement of surgical skills compared to alternative methods.

An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity

Here, we present a protocol to assess the blood-testis barrier integrity by injecting inulin-FITC into testes. This is an efficient in vivo method to study blood-testis barrier integrity that can be compromised by genetic and environmental elements.

Spermatogenesis is the development of spermatogonia into mature spermatozoa in the seminiferous tubules of the testis. This process is supported by ...