We would like to thank C. Burns, C. McRae for outlining the basic principle of this purification protocol, and F. Priller for initial implementation of this method in our lab. S.A.-S. is supported by a Heisenberg professorship of the Deutsche Forschungsgemeinschaft (DFG). This work was supported by DFG grant SE2016/7-1.

This protocol follows the animal care guidelines of the German and Berlin state law; zebrafish handling was monitored by the local authority for animal protection (LaGeSo, Berlin-Brandenburg).
1. Obtaining Zebrafish Embryos for Heart Extraction
<ol>
	<li>Cross cardiac reporter zebrafish such as the Tg(myl7:EGFP)twu34 transgenic line9 in order to obtain embryos with heart-specific GFP expression.</li>
	<li>Maintain the embryos in egg water at 28.5 &#176...

<ol>
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J., Tu, C. T., Hsiao, C. D., Hsieh, F. J., Tsai, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Germ-line+transmission+of+a+myocardium-specific+GFP+transgene+reveals+critical+regulatory+elements+in+the+cardiac+myosin+light+chain+2+promoter+of+zebrafish.">Germ-line transmission of a myocardium-specific GFP transgene reveals critical regulatory elements in the cardiac myosin light chain 2 promoter of zebrafish.</a> Dev Dyn. 228, 30-40 (2003).</li><li>Kimmel, C. B., Ballard, W. W., Kimmel, S. R., Ullmann, B., Schilling, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stages+of+embryonic+development+of+the+zebrafish.">Stages of embryonic development of the zebrafish.</a> Dev Dyn. 203, 253-310 (1995).</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=.">.</a> The zebrafish book. A guide for the laboratory use of zebrafish (Danio rerio). , (2000).</li><li>Veerkamp, 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=Unilateral+dampening+of+Bmp+activity+by+nodal+generates+cardiac+left-right+asymmetry).">Unilateral dampening of Bmp activity by nodal generates cardiac left-right asymmetry).</a> Dev Cell. 24, 660-667 (2013).</li><li>Jin, S. W., Beis, D., Mitchell, T., Chen, J. N., Stainier, D. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+and+molecular+analyses+of+vascular+tube+and+lumen+formation+in+zebrafish.">Cellular and molecular analyses of vascular tube and lumen formation in zebrafish.</a> Development. 132, 5199-5209 (2005).</li><li>Brownlie, 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=Characterization+of+embryonic+globin+genes+of+the+zebrafish.">Characterization of embryonic globin genes of the zebrafish.</a> Dev Biol. 255, 48-61 (2003).</li><li>Marvin, 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=Developmental+expression+patterns+of+the+zebrafish+small+heat+shock+proteins.">Developmental expression patterns of the zebrafish small heat shock proteins.</a> Dev Dyn. 237, 454-463 (2008).</li><li>Lam, C. S., Marz, M., 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=gfap+and+nestin+reporter+lines+reveal+characteristics+of+neural+progenitors+in+the+adult+zebrafish+brain.">gfap and nestin reporter lines reveal characteristics of neural progenitors in the adult zebrafish brain.</a> Dev Dyn. 238, 475-486 (2009).</li><li>Wang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Moesin1+and+Ve-cadherin+are+required+in+endothelial+cells+during+in+vivo+tubulogenesis.">Moesin1 and Ve-cadherin are required in endothelial cells during in vivo tubulogenesis.</a> Development. 137, 3119-3128 (2010).</li><li>Heiman, 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+translational+profiling+approach+for+the+molecular+characterization+of+CNS+cell+types.">A translational profiling approach for the molecular characterization of CNS cell types.</a> Cell. 135, 738-748 (2008).</li><li>Tryon, R. 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This protocol allows the rapid enrichment of zebrafish embryonic heart tissue for gene expression analyses. The quantity and quality of the cardiac-specific RNA sample greatly depends on a few crucial steps: first, the quantity of the sample is greatly improved if loss of hearts is prevented at every step of the protocol, since RNA purification will only work with sufficient starting material. Second, the purity of the sample, which depends entirely on the experimenter, is determined by sorting and collecting hearts with...

Zebrafish (Danio rerio) is widely used in developmental biology to study organogenesis in vivo due to its fast, transparent and extrauterine embryonic development, combined with small size and the availability of transgenic reporter lines with tissue-specific expression of fluorescent proteins. This small vertebrate is particularly well suited to study heart development because oxygenation of the early zebrafish embryo does not rely on heart beat and blood flow; these features have allowed the characterization of large numbers of cardiovascular mutants1,2 and the zebrafish is now a widely recognized model organism to study heart diseases3.
To study gene expression during embryonic development, transcripts are commonly analyzed by whole-mount in situ hybridization (WISH)4, RT-qPCR5, microarrays6, or next generation sequencing (RNA-Seq)7. While WISH allows a spatial-temporal analysis of gene expression within the entire embryo, transcript levels are usually assessed by RT-qPCR, microarrays or RNA-Seq approaches. However, these methods require tissue enrichment for specific gene expression profiling.
Since the zebrafish embryonic heart represents a small fraction of the entire embryo, transcriptome studies during cardiac development require a protocol for dissection and enrichment of hearts. In addition, to obtain physiologically relevant data, it is important to maintain the cardiac tissue fully functional until RNA extraction. Here, we describe a protocol for rapidly isolating physiologically normal and beating hearts from hundreds of zebrafish embryos to efficiently obtain high quality RNA samples for further analyses. The present method is based on the protocol reported by Burns and MacRae, 20068. For enrichment of cardiac tissue, both methods use a transgenic myocardial reporter line and take advantage of the differential adhesion properties of zebrafish embryonic hearts versus other tissues. Briefly, by pipetting many embryos up and down through a narrow pipette tip, hearts are simultaneously released from embryonic bodies and subsequently separated from embryonic debris in two rapid filtration steps; fluorescently labelled hearts are then manually sorted from remaining debris and collected for further processing.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr >
			<td >Equipment for raising fish and collecting eggs&#160;</td>
			<td></td>
			<td></td>
			<td>see the Zebrafish Book11 for details</td>
		</tr>
		<tr >
			<td >Fluorescence stereomicroscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >Refrigerated Microcentrifuge</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >UV-Spectrophotometer</td>
			<td></td>
			<td></td>
			<td>eg. Thermo Scientific Nanodrop 2000</td>
		</tr>
		<tr >
			<td >Nucleic acid electrophoresis chamber</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >Petri dishes 4cm &#216;, coated with 1% agarose in E3 medium</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >Micropipettes and tips (P20, P100, P1000)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >1,5ml centrifugation tubes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >15ml and 50ml centrifugation tubes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >Pair of Dumont #5 forceps</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >ExactaCruz&#8482; Round Gel Loading Tips in Sterile Rack, 1-200&#956;l&#160;</td>
			<td>Santa Cruz</td>
			<td>sc-201732</td>
			<td></td>
		</tr>
		<tr >
			<td >100 &#956;m filter (BD Falcon 100 mm Cell Strainer)</td>
			<td>BD Biosciences</td>
			<td>352360</td>
			<td></td>
		</tr>
		<tr >
			<td >30 &#956;m filter (Pre-Separation Filters-30 &#181;m)</td>
			<td>Miltenyi Biotec</td>
			<td>130-041-407</td>
			<td></td>
		</tr>
		<tr >
			<td >Phase lock gel, heavy, 1,5ml tubes&#160;</td>
			<td>Prime</td>
			<td>2302810</td>
			<td></td>
		</tr>
		<tr >
			<td >Egg water medium</td>
			<td></td>
			<td></td>
			<td>60&#956;g/ml Instant Ocean Sea Salts in ddH2O, 0.00001% (w/v) Methylene Blue</td>
		</tr>
		<tr >
			<td >E3 medium&#160;</td>
			<td></td>
			<td></td>
			<td>5 mM NaCl, 0.17 mM KCl, 0.33 mM CaCl2, 0.33 mM MgSO4</td>
		</tr>
		<tr >
			<td >Tricaine (3-amino benzoic acidethylester)</td>
			<td>Sigma-Aldrich</td>
			<td>A-5040</td>
			<td>4mg/ml Tricaine stock solution, pH 7</td>
		</tr>
		<tr >
			<td >1% agarose (in E3 medium)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >1% agarose gel (in TBE buffer)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >Leibovitz&#180;s L-15 medium&#160;</td>
			<td>Gibco</td>
			<td>21083-027</td>
			<td></td>
		</tr>
		<tr >
			<td >FBS (Fetal Bovine Serum)</td>
			<td>Sigma</td>
			<td>F4135</td>
			<td></td>
		</tr>
		<tr >
			<td >RNAlater</td>
			<td>Ambion</td>
			<td>AM7020</td>
			<td></td>
		</tr>
		<tr >
			<td >Trizol</td>
			<td>Ambion</td>
			<td>1559606</td>
			<td></td>
		</tr>
		<tr >
			<td >Glycogen&#160;</td>
			<td>Invitrogen</td>
			<td>10814-010</td>
			<td>20 &#181;g/&#181;L in RNase-free water</td>
		</tr>
		<tr >
			<td >chloroform</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >isopropanol</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >75% ethanol (in DEPC-ddH2O)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >Nuclease-free water or sterilized DEPC treated ddH2O</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >Nucleic acid loading buffer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr >
			<td >TBE (Tris/Borate/EDTA) buffer for electrophoresis</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

large-scale zebrafish embryonic heart dissection for transcriptional analysis

The zebrafish embryonic heart is composed of only a few hundred cells, representing only a small fraction of the entire embryo. Therefore, to prevent the cardiac transcriptome from being masked by the global embryonic transcriptome, it is necessary to collect sufficient numbers of hearts for further analyses. Furthermore, as zebrafish cardiac development proceeds rapidly, heart collection and RNA extraction methods need to be quick in order to ensure homogeneity of the samples. Here, we present a rapid manual dissection protocol for collecting functional/beating hearts from zebrafish embryos. This is an essential prerequisite for subsequent cardiac-specific RNA extraction to determine cardiac-specific gene expression levels by transcriptome analyses, such as quantitative real-time polymerase chain reaction (RT-qPCR). The method is based on differential adhesive properties of the zebrafish embryonic heart compared with other tissues; this allows for the rapid physical separation of cardiac from extracardiac tissue by a combination of fluidic shear force disruption, stepwise filtration and manual collection of transgenic fluorescently labeled hearts.

Here, we describe a representative heart dissection experiment using the zebrafish Tg(myl7:GFP)twu34 transgenic line9, which expresses green fluorescent protein (GFP) exclusively within the myocardium (Fig. 1). We collected both the dissected hearts and the embryos from which they were derived to assess the purity of the heart sample. Briefly, homozygous Tg(myl7:GFP)twu34 zebrafish9 were outcrossed with wild-type so that all embryonic hearts ...

Watch this Scientific Journal Video about Large-scale Zebrafish Embryonic Heart Dissection for Transcriptional Analysis at JoVE.com

Large-scale Zebrafish Embryonic Heart Dissection for Transcriptional Analysis

To analyse cardiac gene expression profiles during zebrafish heart development, total RNA has to be extracted from isolated hearts. Here, we present a protocol for collecting functional/beating hearts by rapid manual dissection from zebrafish embryos to obtain cardiac-specific mRNA.

The zebrafish embryonic heart is composed of only a few hundred cells, representing only a small fraction of the entire embryo. Therefore, to prevent the ...

large-scale-zebrafish-embryonic-heart-dissection-for-transcriptional

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14.1K Views.  Max Delbrück Center for Molecular Medicine. To analyse cardiac gene expression profiles during zebrafish heart development, total RNA has to be extracted from isolated hearts. Here, we present a protocol for collecting functional/beating hearts by rapid manual dissection from zebrafish embryos to obtain cardiac-specific mRNA.