We thank Susan Farmer and the staff of the UAB zebrafish research facility for zebrafish care. Funding provided by start-up funds from the Department of Pharmacology and Toxicology.

NOTE: This protocol was approved by the University of Alabama at Birmingham Institutional Animal Care and Use Committee.
1. Zebrafish Breeding and Egg Collections
<ol>
	<li>Three days before beginning chemical exposures, assemble breeding tanks with dividers to separate males and females. Fill each tank halfway with aquaculture system water. Using a net, transfer Tg(5xERE:GFP)c262/c262 fish to breeding tanks, placing 2 males and 3 females in each tank separated by a divid...

<ol>
	<li>Molina, G., Watkins, S., Tsang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+FGF+reporter+transgenic+zebrafish+and+their+utility+in+chemical+screens.">Generation of FGF reporter transgenic zebrafish and their utility in chemical screens.</a> BMC Developmental Biology. 7, 62 (2007).</li><li>Perz-Edwards, A., Hardison, N. L., Linney, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinoic+acid-mediated+gene+expression+in+transgenic+reporter+zebrafish.">Retinoic acid-mediated gene expression in transgenic reporter zebrafish.</a> Developmental Biology. , 89-101 (2001).</li><li>Gorelick, D. A., Halpern, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+of+Estrogen+Receptor+Transcriptional+Activation+in+Zebrafish.">Visualization of Estrogen Receptor Transcriptional Activation in Zebrafish.</a> Endocrinology. 152, 2690-2703 (2011).</li><li>Tsang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish:+A+tool+for+chemical+screens.">Zebrafish: A tool for chemical screens.</a> Birth Defects Research Part C: Embryo Today: Reviews. 90, 185-192 (2010).</li><li>Peravali, 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=Automated+feature+detection+and+imaging+for+high-resolution+screening+of+zebrafish+embryos.">Automated feature detection and imaging for high-resolution screening of zebrafish embryos.</a> Biotechniques. 50, 319-324 (2011).</li><li>Walker, S. 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=Automated+reporter+quantification+in+vivo:+high-throughput+screening+method+for+reporter-based+assays+in+zebrafish.">Automated reporter quantification in vivo: high-throughput screening method for reporter-based assays in zebrafish.</a> PLoS One. 7, (2012).</li><li>Vogt, 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=Automated+image-based+phenotypic+analysis+in+zebrafish+embryos.">Automated image-based phenotypic analysis in zebrafish embryos.</a> Developmental Dynamics. 238, 656-663 (2009).</li><li>Vogt, A., Codore, H., Day, B. W., Hukriede, N. A., Tsang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+automated+imaging+and+analysis+for+zebrafish+chemical+screens.">Development of automated imaging and analysis for zebrafish chemical screens.</a> J. Vis. Exp. , (2010).</li><li>Gruber, C. J., Gruber, D. M., Gruber, I. M., Wieser, F., Huber, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomy+of+the+estrogen+response+element.">Anatomy of the estrogen response element.</a> Trends in Endocrinology and Metabolism. 15, 73-78 (2004).</li><li>Rovira, 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=Chemical+screen+identifies+FDA-approved+drugs+and+target+pathways+that+induce+precocious+pancreatic+endocrine+differentiation.">Chemical screen identifies FDA-approved drugs and target pathways that induce precocious pancreatic endocrine differentiation.</a> Proceedings of the National Academy of Sciences USA. 108, 19264-19269 (2011).</li><li>Westerfield, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Zebrafish+Book:+A+guide+for+the+laboratory+use+of+zebrafish+(Danio+rerio).">The Zebrafish Book: A guide for the laboratory use of zebrafish (Danio rerio).</a> , (2000).</li></ol>

The authors have no competing financial interests.

This protocol describes a straightforward method to automatically image tissue-specific fluorescence in zebrafish embryos. The protocol was developed using a Zeiss Axio Observer. Z1 with Zen Blue 2011 software, however the technique can be adapted using any inverted microscope with a motorized stage and microscope control software that can perform tiling to create composite images. Equipping an inverted microscope with a motorized stage can provide a practical, less expensive alternative to purchasing specialized equipme...

Transgenic zebrafish have been developed that allow for the direct visualization of activity in signaling pathways, such as fibroblast growth factors1, retinoic acid2 and estrogens3, in live embryos. Such tools enable screening for chemicals that perturb signaling pathways (assayed as change in fluorescence intensity) or for chemicals that modulate signaling in a tissue-specific manner (change in fluorescence localization)4. Automated image capture increases the throughput of chemical screens dramatically5,6. Screens that automatically assay fluorescence in live zebrafish often rely on expensive, specialized equipment. So-called high-content screening provides the benefit of high resolution, quantitative imaging but at the cost of using specialized plate readers equipped for confocal microscopy7,8. The goal of this method is to automatically assay tissue-specific fluorescence in zebrafish embryos in a 96-well plate using a standard epifluorescence microscope. Tissue-specific fluorescence can be distinguished using this technique and may be a reasonable approach for laboratories that lack access to specialized plate readers or high-content screening equipment.
In this protocol, we use automated imaging to detect tissue-specific estrogen receptor (ER) agonists in live zebrafish at 3 days post fertilization (dpf). The transgenic line Tg(5xERE:GFP)c262/c262 contains 5 tandem estrogen response element DNA sequences (ERE) upstream of green fluorescent protein (GFP)3. In the absence of ligand, ERs are normally inactive. Ligand binding triggers a conformational change, allowing receptors to bind ERE DNA and regulate transcription9. 5xERE:GFP fish can be used to screen chemical libraries for ER modulators and can be used to screen environmental water samples for estrogenic contaminants.

<table border="0" cellpadding="0" cellspacing="0" style="width:885px;" width="886">
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	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:100px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:451px;">Comments/Description</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Plastic transfer pipettes; wide bore</td>
			<td style="width:100px;">Fisher</td>
			<td style="width:119px;">13-711-23</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Plastic transfer pipettes; fine tip</td>
			<td style="width:100px;">Fisher</td>
			<td style="width:119px;">13-711-26</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">96-well, round, flat bottom plates</td>
			<td style="width:100px;">Fisher</td>
			<td style="width:119px;">21-377-203</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">100 x 35mm paltes</td>
			<td style="width:100px;">Fisher</td>
			<td style="width:119px;">08-757-100D</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">35 x 60mm plates</td>
			<td style="width:100px;">Fisher</td>
			<td style="width:119px;">08-757-100B</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Dumont #5 fine forceps</td>
			<td style="width:100px;">Fine Science Tools</td>
			<td style="width:119px;">11254-20</td>
			<td>tip dimensions 0.05 x 0.01 mm, for manually removing chorions from embryos</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tricane methanesulfonate</td>
			<td style="width:100px;">Sigma Aldrich</td>
			<td style="width:119px;">A5040-25G</td>
			<td>see Zebrafish Book for recipe (http://zfin.org/zf_info/zfbook/chapt10.html#wptohtml63)&#160;</td>
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			<td height="21" style="height:21px;">1-phenyl 2-thiourea (PTU)</td>
			<td style="width:100px;">Sigma Aldrich</td>
			<td style="width:119px;">P7629-10G</td>
			<td>Prepare 20 mM stock (100x) and use at 200 &#956;M in E3B&#160;</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Zeiss Axio Observer Z1</td>
			<td style="width:100px;">Carl Zeiss</td>
			<td style="width:119px;"></td>
			<td style="width:451px;">Protocol requires an inverted fluorescence microscope with a motorized stage</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">20x long working distance objective</td>
			<td style="width:100px;">Carl Zeiss</td>
			<td style="width:119px;"></td>
			<td>We use an objective with 0.4 NA and 8.4 mm working distance</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Axiocam HRm digital camera</td>
			<td style="width:100px;">Carl Zeiss</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">ZenBlue 2011 microscope control software</td>
			<td style="width:100px;">Carl Zeiss</td>
			<td style="width:119px;"></td>
			<td style="width:451px;">Protocol requires microscopy automation and control software to enable capturing of tiled images using a motorized stage</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Methylene Blue</td>
			<td style="width:100px;">Sigma Aldrich</td>
			<td>&#160;MB-1; 25 grams</td>
			<td>make 2% solution in RO water for use in E3B (below)</td>
		</tr>
		<tr height="273">
			<td height="273" style="height:273px;">E3B</td>
			<td style="width:100px;"></td>
			<td style="width:119px;"></td>
			<td style="width:451px;">60X E3 SOLUTION: 
			NaCl&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; - 17.2 grams 
			KCl&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; - 0.76 grams 
			CaCl2-2H2O&#160;&#160;&#160;&#160; - 2.9 grams 
			MgSO4-7H2O&#160; - 4.9 grams or MgSO4 &#8211; 2.39 grams 
			Dissolve in 1 liter Milli-Q water; store in sterile 1 liter bottle. 
			 
			1X E3B SOLUTION FOR ZEBRAFISH: 
			60X E3&#160;&#160;&#160;&#160;&#160; 150mls 
			2% methylene blue&#160;&#160;&#160;&#160; 100&#956;l&#160; 
			Bring to 9 liters with Milli-Q water 
			&#160;</td>
		</tr>
	</tbody>
</table>

semi-automated imaging of tissue-specific fluorescence in zebrafish embryos

Zebrafish embryos are a powerful tool for large-scale screening of small molecules. Transgenic zebrafish that express fluorescent reporter proteins are frequently used to identify chemicals that modulate gene expression. Chemical screens that assay fluorescence in live zebrafish often rely on expensive, specialized equipment for high content screening. We describe a procedure using a standard epifluorescence microscope with a motorized stage to automatically image zebrafish embryos and detect tissue-specific fluorescence. Using transgenic zebrafish that report estrogen receptor activity via expression of GFP, we developed a semi-automated procedure to screen for estrogen receptor ligands that activate the reporter in a tissue-specific manner. In this video we describe procedures for arraying zebrafish embryos at 24-48 hours post fertilization (hpf) in a 96-well plate and adding small molecules that bind estrogen receptors. At 72-96 hpf, images of each well from the entire plate are automatically collected and manually inspected for tissue-specific fluorescence. This protocol demonstrates the ability to detect estrogens that activate receptors in heart valves but not in liver.

Figure 1 shows composite images from individual wells of a 96-well plate. Each composite image is composed of 59 individual images with 5% image overlap. Note that the live zebrafish are oriented randomly within each well, yet we are able to distinguish fluorescence in the heart from the liver. Brightfield images are useful as references to assess zebrafish orientation and visualize morphological abnormalities (Figures 1A and&#160;1C). Automated imaging using a 10x objective is used to s...

Watch this Scientific Journal Video about Semi-automated Imaging of Tissue-specific Fluorescence in Zebrafish Embryos at JoVE.com

Semi-automated Imaging of Tissue-specific Fluorescence in Zebrafish Embryos

Described here is a protocol for semi-automated imaging of tissue-specific fluorescence in zebrafish embryos.

Zebrafish embryos are a powerful tool for large-scale screening of small molecules. Transgenic zebrafish that express fluorescent reporter proteins are ...

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9.5K Views.  University of Alabama at Birmingham. Described here is a protocol for semi-automated imaging of tissue-specific fluorescence in zebrafish embryos.