We would like to acknowledge the contributions of D&ouml;rthe J&uuml;lich, Jennifer Round and Andrew Mara in developing this protocol. Research support provided by the NICHD, the American Cancer Society and the March of Dimes.

1. FIXATION
<ol>
<li>Fix embryos overnight at 4&deg;C with 4% paraformaldehyde (PFA) in PBS.</li>
<li>Remove fix and wash 2 x PBS, 5 minutes each at room temperature (RT).</li>
<li>Manually dechorionate embryos in PBS in a glass depression plate using watchmaker forceps. After dechorionation, embryos are transferred using a fire-polished glass Pasteur pipette as they may stick to polypropylene pipettes.</li>
<li>Transfer embryos through a series of 25%, 50% and 75% methanol in PBS for 5 minutes each.</li>
<li>Replace liquid with 100% methanol, incubate 5 minutes and then replace with fresh methanol.</li>
<li>Place embryos at -20&deg;C for a minimum of one hour. (We typically incubate the embryos overnight. Standard in situ hybridization will work on embryos stored for more than a year, but we have not examined whether the high-resolution of the fluorescent in situ hybridization is lost by prolonged storage.)</li>
<li>Wash embryos for 5 minutes each in 75%, 50%, 25% methanol in PBST at RT. Wash twice for 5 minutes each in PBST at RT.</li>
<li>Fix again for 20 minutes in 4% PFA in PBS at RT.</li>
<li>Wash twice for 5 minutes each in PBST at RT.</li>
</ol>
NOTE REGARDING PFA: We store 4% PFA in aliquots at &ndash;20&ordm;C (see table of reagents). For the initial fixation, we only use PFA that has never been previously thawed. For subsequent fixations, we often use PFA that has been previously thawed. The initial fixation appears to be critical for successful staining with this protocol.
2. PROTEINASE AND POSTFIXATION
<ol>
<li>Digest with proteinase K (5&mu;g/ml in PBST) at RT for 3 to 12 minutes to permeabilize the embryos. (The incubation time depends on the age of the embryos as younger stages are more sensitive. It also depends on the batch of enzyme.) For somitogenesis stage embryos, we typically permeabilize for 3-4 minutes. During this incubation, we lay the microcentrifuge tube on its side.</li>
<li>Rinse briefly in PBST and wash once for 5 minutes in PBST.</li>
<li>Fix again for 20 minutes in 4% PFA in PBS at RT.</li>
<li>Wash twice, for 5 minutes each, in PBST at RT.</li>
</ol>
3. PREHYBRIDIZATION
<ol>
<li>Incubate the embryos for 5 minutes at 65&ordm; C in HYB-.</li>
<li>Prehybridize at 65&ordm; C for at least 1 hour in HYB+.</li>
</ol>
4. HYBRIDIZATION
<ol>
<li>Remove all but 50 &mu;l of the preHYB, but make sure to keep the embryos completely submerged.</li>
<li>Add 1-2 &mu;l of each riboprobe (digoxygenin- and fluorescein-labeled riboprobes) to the embryos and mix by gently flicking the tube. The amount of probe is typically 1-2&micro;l from a 20&micro;l probe synthesis reaction.</li>
<li>Given that fluorescein is light-sensitive, the tubes should be wrapped in aluminum foil or otherwise exposed to minimal light from this point forward.</li>
<li>Incubate the embryos overnight at 65&ordm;C.</li>
</ol>
5. PROBE REMOVAL
Note that the solutions from this point forward lack detergent. Elimination of detergent appears to help the staining reactions but does cause the embryos to become rather sticky.
<ol>
<li>Remove the riboprobe.</li>
<li>Wash 2 x 30 minutes at 65&ordm;C in 50% formamide/2xSSC.</li>
<li>Wash for 15 minutes at 65&ordm;C in 2 x SSC.</li>
<li>Wash for 30 minutes 65&ordm;C in 0.2 x SSC.</li>
</ol>
6. ANTI-FLUORESCEIN ANTIBODY INCUBATION
<ol>
<li>Block for at least 1 hour at RT in 500&mu;l of a solution of 1x maleic acid buffer plus 2% blocking reagent (see table of reagents).</li>
<li>Add the anti-Fluorescein-POD antibody, as supplied by Roche, at a 1:500 dilution in the blocking solution.</li>
<li>Incubate overnight at 4&ordm;C. During this incubation, we lay the microcentrifuge tube on its side.</li>
<li>Wash 4 x 20 minutes in 1x maleic acid buffer. Wash twice for 5 minutes each in PBS.</li>
</ol>
7. DETECTION OF FLUORESCEIN-LABELLED PROBE
<ol>
<li>Incubate 30-60 minutes in TSA Plus Fluorescein Solution. (Spin down TSA substrate before making staining solution. For the reaction, dilute tyramide reagent 1:50 in Perkin Elmer amplification diluent buffer.) During this incubation, we lay the microcentrifuge tube on its side. Reaction time must be determined empirically for each probe. Unfortunately, the staining reaction cannot be visually monitored as the substrate is fluorescent, and one will see ubiquitous green fluorescence throughout the staining reaction.</li>
<li>Wash for 10 minutes each in 30%, 50%, 75% and 100% methanol in PBS.</li>
<li>Incubate in a solution of 1% H202 in methanol for 30 minutes to inactivate the first peroxidase.</li>
<li>Wash 10 minutes each in 75%, 50% and 30% methanol in PBS. Then wash twice for 10 minutes each in PBS. It is important that all of the methanol be removed.</li>
</ol>
NOTES ON THE TYRAMIDE SIGNAL AMPLIFICATION: We have been using the Perkin Elmer TSA Kits. We find that the Alexa-Tyramide substrates stain well using the Perkin Elmer amplification diluent buffer, but we have not had success using the staining buffer provided with the Invitrogen/Molecular Probes Kits. Lastly, we have found that Cy5 fluorescence is eliminated by subsequent Methanol/H2O2 treatment while fluorescein and Alexa-647 are unaffected. Cy3 may also be adversely affected by the Methanol/H2O2 treatment as it is structurally related to Cy5. For this reason, Cy3 and Cy5 TSA reactions should only be used for the second staining reaction in a double fluorescent in situ protocol.
8. ANTI-Digoxygenin ANTIBODY INCUBATION
<ol>
<li>Block the embryos again for at least 1 hour at RT in a solution of 1x maleic acid buffer plus 2% blocking reagent.</li>
<li>Add the anti-DIG POD antibody as supplied by Roche at a 1:1000 dilution in above blocking solution</li>
<li>Incubate overnight at 4&ordm;C. During this incubation, we lay the microcentrifuge tube on its side.</li>
<li>Wash 4 x 20 minutes in 1x maleic acid buffer. Wash twice for 5 minutes each in PBS.</li>
</ol>
9. DETECTION OF Digoxygenin-LABELLED PROBE
<ol>
<li>Incubate 30-60 minutes in TSA Plus Cy5 Solution (Spin down TSA substrate before making staining solution. For the reaction, dilute tyramide reagent 1:50 in amplification diluent buffer) During this incubation, we lay the microcentrifuge tube on its side. Reaction time must be determined empirically for each probe.</li>
<li>Wash three times for 10 minutes each in PBST.</li>
</ol>
10. PROPIDIUM IODIDE STAINING
<ol>
<li>Wash twice for 5 minutes each in 2 x SSC.</li>
<li>Incubate embryos for 30 minutes at 37&deg;C in 50 &mu;l 2 x SSCT with 10 &mu;l RNAse (for a final concentration of 100&mu;g/ml).</li>
<li>Wash six times for 3 minutes each in 2 x SSC at RT.</li>
<li>Stain embryos for 8 minutes in a solution of 330&micro;g/ml propidium iodide in 2 x SSC.</li>
<li>Wash six times for 3 minutes each in 2 x SSC at RT.</li>
<li>Fix for 20 minutes in 4% PFA in PBS at RT.</li>
<li>Wash twice, for 5 minutes each, in PBST at RT.</li>
</ol>
11. MOUNTING
<ol>
<li>Incubate the embryos for 10 minutes each in 25% and 50% glycerol in PBST. Clear overnight in 75% glycerol at 4&ordm;C.</li>
<li>We dissect and deyolk the embryos and flat mount them on a microscope slide. The yolk can produce significant background fluorescence. Dissection is much easier after the embryos have cleared ovenight in gylcerol.</li>
</ol>
SOLUTIONS:
<table border="1">
<tbody>
<tr>
<td>PBST</td>
<td>PBS plus 0.1% Tween</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>SSCT</td>
<td>SSC plus 0.1% Tween</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>HYB-</td>
<td>50% formamide 5xSSC 0.1% Tween-20</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>HYB+</td>
<td>HYB- 5mg/ml torula (yeast) RNA 50&mu;g/ml heparin</td>
<td style="width: 300px;">The torula RNA is prepared by proteinase K digestion of RNA with subsequent phenol-, phenol-chloroform-, and chloroform-extraction.The RNA is precipitated and dissolved in DEPC-treated water.</td>
</tr>
<tr>
<td>1 x maleic acid buffer</td>
<td>150mM maleic acid, 100mM NaCl (pH 7.5)</td>
<td>&nbsp;</td>
</tr>
</tbody>
</table>
<img src="/files/ftp_upload/1229/Brend_Holley_Fig1.png" alt="Figure 1" width="600" height="688" />
Figure 1. Representative results of whole mount double fluorescent in situ hybridization. (A-C). Images show a single confocal section through the posterior region of a zebrafish embryo at the ten-somite stage. The view is dorsal with anterior to the top. Nuclei stained with propidium iodide are colored blue. (A) deltaC mRNA was detected using a digoxygenin-labeled riboprobe and TSA-Cy5 reagent. (B) mRNA transcribed from the her1 gene was detected with a fluorescein-labeled riboprobe and TSA-fluorescein reagent. (C) Merging the green and red channels unambiguously identifies regions of distinct or overlapping gene expression of the two genes. (D, E) Detail of her1 expression demonstrating the high resolution of this procedure. Subcellular localization of mRNA can be clearly discerned. Arrowheads indicate a cell exhibiting active transcription, revealed by dots of staining in the nucleus. Arrows indicate a cell showing cytoplasmic localization of mRNA. (F, G) Double staining for her1 and deltaC reveals cells that are transcribing both genes (white arrowhead), or either gene separately (red and green arrowheads).

<ol>
	<li>Schulte-Merker, S., Ho, R. K., Herrmann, B. G., N&#252;sslein-Volhard, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+protein+product+of+the+zebrafish+homologue+of+the+mouse+T-gene+is+expressed+in+nuclie+of+the+germ+ring+and+the+notochord+of+the+early+embryo.">The protein product of the zebrafish homologue of the mouse T-gene is expressed in nuclie of the germ ring and the notochord of the early embryo.</a> Development. 116, 1021-1027 (1992).</li><li>Jowett, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Double+in+situ+hybridization+techniques+in+zebrafish.">Double in situ hybridization techniques in zebrafish.</a> Methods. 23, 345-358 (2001).</li><li>J&#252;lich, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=beamter/deltaC+and+the+role+of+Notch+ligands+in+the+zebrafish+somite+segmentation,+hindbrain+neurogenesis+and+hypochord+differentiation.">beamter/deltaC and the role of Notch ligands in the zebrafish somite segmentation, hindbrain neurogenesis and hypochord differentiation.</a> Dev Biol. 286, 391-404 (2005).</li><li>Mara, A., Schroeder, J., Chalouni, C., Holley, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Priming,+Initiation+and+Synchronization+of+the+Segmentation+Clock+by+deltaD+and+deltaC.">Priming, Initiation and Synchronization of the Segmentation Clock by deltaD and deltaC.</a> Nat Cell Biol. 9, 523-530 (2007).</li><li>Lecuyer, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+analysis+of+mRNA+localization+reveals+a+prominent+role+in+organizing+cellular+architecture+and+function.">Global analysis of mRNA localization reveals a prominent role in organizing cellular architecture and function.</a> Cell. 131, 174-187 (2007).</li></ol>

The protocol presented here works well with probes that give a clean strong signal after staining for 30-45 minutes in a typical alkaline phosphatase-mediated reaction. Prior to performing the fluorescent in situ hybridization protocol, we always test our probes using the standard non-fluorescent protocol (provided in supplemental material along with the probe synthesis protocol). We have had less success with the fluorescent in situ hybridization protocol when using weaker probes, but it may be possible in some cases....

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Paraformaldehyde 16% solution, EM Grade</td>
<td>&nbsp;</td>
<td>Electron Microscopy Services</td>
<td>15710</td>
<td>Dilute to 4% in 1.33x PBS (final 1x). Store in 2ml aliquots at &#x2013;20&deg;C</td>
</tr>
<tr>
<td>Proteinase K, recombinant PCR grade</td>
<td>&nbsp;</td>
<td>Roche</td>
<td>03115879001</td>
<td>Make a 20mg/ml stock solution in water. Store in 1ml aliquots at &#x2013;20&deg;C</td>
</tr>
<tr>
<td>Blocking Reagent</td>
<td>&nbsp;</td>
<td>Roche</td>
<td>11096176001</td>
<td>Make a 10% stock solution in 1x maleic acid buffer. Store in 50ml aliquots at &#x2013;20&deg;C. Stable over multiple freeze/thaws.</td>
</tr>
<tr>
<td>Anti-Fluorescein-POD, Fab fragments</td>
<td>&nbsp;</td>
<td>Roche</td>
<td>11426346910</td>
<td>Aliquot and store at -20&deg;C. Keep one working aliquot at 4&deg;C.</td>
</tr>
<tr>
<td>Anti-Digoxigenin-POD, Fab fragments</td>
<td>&nbsp;</td>
<td>Roche</td>
<td>11207739910</td>
<td>As above.</td>
</tr>
<tr>
<td>TSA Plus Fluorescein system</td>
<td>&nbsp;</td>
<td>Perkin Elmer</td>
<td>NEL741001KT</td>
<td>Prepare each vial of TSA reagent only when needed. Dissolve in 60&mu;l DMSO. Store at 4&deg;C.</td>
</tr>
<tr>
<td>TSA Plus Cyanine5 system</td>
<td>&nbsp;</td>
<td>Perkin Elmer</td>
<td>NEL745001KT</td>
<td>As above</td>
</tr>
<tr>
<td>TSA Plus Cyanine3 system</td>
<td>&nbsp;</td>
<td>Perkin Elmer</td>
<td>NEL744001KT</td>
<td>As above</td>
</tr>
<tr>
<td>TSA Kit #16 AlexaFluor647 tyramide (plus HRP-goat-anti-rabbit IgG)</td>
<td>&nbsp;</td>
<td>Molecular Probes /Invitrogen</td>
<td>T20926</td>
<td>Dissolve tyramide reagent in 150&mu;l DMSO, aliquot and store at &#x2013;20&deg;C.</td>
</tr>
<tr>
<td>RNase, DNase free</td>
<td>&nbsp;</td>
<td>Roche</td>
<td>11119915001</td>
<td>Supplied as 500&mu;g/ml solution</td>
</tr>
<tr>
<td>Propidium Iodide</td>
<td>&nbsp;</td>
<td>Molecular Probes /Invitrogen</td>
<td>P-3566</td>
<td>Supplied as 1mg/ml solution in water.</td>
</tr>		</tbody>
		</table>
		</div>

zebrafish whole mount high-resolution double fluorescent in situ hybridization

Whole mount in situ hybridization is one of the most widely used techniques in developmental biology. Here, we present a high-resolution double fluorescent in situ hybridization protocol for analyzing the precise expression pattern of a single gene and for determining the overlap of the expression domains of two genes. The protocol is a modified version of the standard in situ hybridization using alkaline phosphatase and substrates such as NBT/BCIP and Fast Red 1,2. This protocol utilizes standard digoxygenin and fluorescein labeled probes along with tyramide signal amplification (TSA) 3. The commercially available TSA kits allow flexible experimental design as fluorescence emission from green to far-red can be used in combination with various nuclear stains, such as propidium iodide, or fluorescence immunohistochemistry for proteins. TSA produces a reactive fluorescent substrate that quickly covalently binds to moieties, typically tyrosine residues, in the immediate vicinity of the labeled antisense riboprobe. The resulting staining patterns are high resolution in that subcellular localization of the mRNA can be observed using laser scanning confocal microscopy 3,4. One can observe nascent transcripts at the chromosomal loci, distinguish nuclear and cytoplasmic staining and visualize other patterns such as cortical localization of mRNA. Studies in Drosophila indicate that roughly 70% of mRNAs exhibit specific patterns of subcellular localization that frequently correlate with the function of the encoded protein 5. When combined with computer-aided reconstruction of 3D confocal datasets, our protocol allows the detailed analysis of mRNA distribution with sub-cellular resolution in whole vertebrate embryos.

Watch this Scientific Journal Video about Zebrafish Whole Mount High-Resolution Double Fluorescent In Situ Hybridization at JoVE.com

Zebrafish Whole Mount High-Resolution Double Fluorescent In Situ Hybridization

Whole mount in situ hybridization is one of the most widely used techniques in developmental biology. Here, we present a high-resolution double fluorescent in situ hybridization protocol for analyzing the precise expression pattern of a single gene and for determining the overlap of the expression domains of two genes. We include a propidium iodide nuclear counter-stain to highlight tissue organization.

Zebrafish Whole Mount High-Resolution Double Fluorescent In Situ Hybridization

Whole mount in situ hybridization is one of the most widely used techniques in developmental biology.  Here, we present a high-resolution double ...

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23.1K Views.  Yale University. Whole mount in situ hybridization is one of the most widely used techniques in developmental biology. Here, we present a high-resolution double fluorescent in situ hybridization protocol for analyzing the precise expression pattern of a single gene and for determining the overlap of the expression domains of two genes. We include a propidium iodide nuclear counter-stain to highlight tissue organization. 

Video: Zebrafish Whole Mount High-Resolution Double Fluorescent In Situ Hybridization

Double Whole Mount in situ Hybridization of Early Chick Embryos

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying  gene expression in brain, neural tube, somite and heart primordia formation. This video demonstrates the different steps in 2-color whole mount in situ hybridization; First, the embryo is dissected from the egg and fixed in paraformaldehyde. Second, the embryo is processed for prehybridization. The embryo is then hybridized with two different probes, one coupled to DIG, and one coupled to FITC.  Following overnight hybridization, the embryo is incubated with DIG coupled antibody. Color reaction for DIG substrate is performed, and the region of interest appears blue. The embryo is then incubated with FITC coupled antibody. The embryo is processed for color reaction with FITC, and the region of interest appears red. Finally, the embryo is fixed and processed for phtograph and sectioning. A troubleshooting guide is also presented.

This video demonstrates 2-color whole mount in situ hybridization, a method by which the spatial and temporal expression pattern of 2 different genes can be visualized in young chick embryos. This method was originally introduced by David Wilkinson, Domingos Henrique, Phil Ingham and David Ish -Horowicz.

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ...

Method for Whole Mount Antibody Staining in Chick

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying antibody expression in developing brain, neural tube and somite. This video demonstrates the different steps in whole-mount antibody staining using HRP conjugated secondary antibodies; First, the embryo is dissected from the egg and fixed in paraformaldehyde. Second, endogenous peroxidase is inactivated; The embryo is then exposed to primary antibody. After several washes, the embryo is incubated with secondary antibody conjugated to HRP. Peroxidase activity is revealed using reaction with diaminobenzidine substrate. Finally, the embryo is fixed and processed for photography and sectioning. The advantage of this method over the use of fluorescent antibodies is that embryos can be processed for wax sectioning, thus enabling the study of antigen sites in cross section. This method was originally introduced by Jane Dodd and Tom Jessell 1.

This video demonstrates whole mount immunohistochemistry, a method by which the spatial and temporal expression pattern of an antigen can be visualized in young chick embryos. This method was originally introduced by Jane Dodd and Tom Jessell.

Using Whole Mount in situ Hybridization to Link Molecular and Organismal Biology

Whole mount in situ hybridization (WISH) is a common technique in molecular biology laboratories used to study gene expression through the localization of specific mRNA transcripts within whole mount specimen. This technique (adapted from Albertson and Yelick, 2005) was used in an upper level undergraduate Comparative Vertebrate Biology laboratory classroom at Syracuse University. The first two thirds of the Comparative Vertebrate Biology lab course gave students the opportunity to study the embryology and gross anatomy of several organisms representing various chordate taxa primarily via traditional dissections and the use of models. The final portion of the course involved an innovative approach to teaching anatomy through observation of vertebrate development employing molecular techniques in which WISH was performed on zebrafish embryos. A heterozygous fibroblast growth factor 8 a (fgf8a) mutant line, ace, was used. Due to Mendelian inheritance, ace intercrosses produced wild type, heterozygous, and homozygous ace/fgf8a mutants in a 1:2:1 ratio. RNA probes with known expression patterns in the midline and in developing anatomical structures such as the heart, somites, tailbud, myotome, and brain were used. WISH was performed using zebrafish at the 13 somite and prim-6 stages, with students performing the staining reaction in class. The study of zebrafish embryos at different stages of development gave students the ability to observe how these anatomical structures changed over ontogeny. In addition, some ace/fgf8a mutants displayed improper heart looping, and defects in somite and brain development. The students in this lab observed the normal development of various organ systems using both external anatomy as well as gene expression patterns. They also identified and described embryos displaying improper anatomical development and gene expression (i.e., putative mutants).
For instructors at institutions that do not already own the necessary equipment or where funds for lab and curricular innovation are limited, the financial cost of the reagents and apparatus may be a factor to consider, as will the time and effort required on the part of the instructor regardless of the setting. Nevertheless, we contend that the use of WISH in this type of classroom laboratory setting can provide an important link between developmental genetics and anatomy. As technology advances and the ability to study organismal development at the molecular level becomes easier, cheaper, and increasingly popular, many evolutionary biologists, ecologists, and physiologists are turning to research strategies in the field of molecular biology. Using WISH in a Comparative Vertebrate Biology laboratory classroom is one example of how molecules and anatomy can converge within a single course. This gives upper level college students the opportunity to practice modern biological research techniques, leading to a more diversified education and the promotion of future interdisciplinary scientific research.

Using Whole Mount in situ Hybridization to Link Molecular and Organismal Biology

Whole mount in situ hybridization (WISH) was used in an upper level undergraduate Comparative Vertebrate Biology course in addition to vertebrate dissections. This gave students the opportunity to study gene expression patterns as well as gross anatomy, linking the study of molecular and organismal biology within one course.

Whole mount in situ hybridization (WISH) is a common technique in molecular biology laboratories used to study gene expression through the localization of ...

Whole Mount in Situ Hybridization of E8.5 to E11.5 Mouse Embryos

Whole mount in situ hybridization is a very informative approach for defining gene expression patterns in embryos. The in situ hybridization procedures are lengthy and technically demanding with multiple important steps that collectively contribute to the quality of the final result. This protocol describes in detail several key quality control steps for optimizing probe labeling and performance. Overall, our protocol provides a detailed description of the critical steps necessary to reproducibly obtain high quality results. First, we describe the generation of digoxygenin (DIG) labeled RNA probes via in vitro transcription of DNA templates generated by PCR. We describe three critical quality control assays to determine the amount, integrity and specific activity of the DIG-labeled probes. These steps are important for generating a probe of sufficient sensitivity to detect endogenous mRNAs in a whole mouse embryo. In addition, we describe methods for the fixation and storage of E8.5-E11.5 day old mouse embryos for in situ hybridization. Then, we describe detailed methods for limited proteinase K digestion of the rehydrated embryos followed by the details of the hybridization conditions, post-hybridization washes and RNase treatment to remove non-specific probe hybridization. An AP-conjugated antibody is used to visualize the labeled probe and reveal the expression pattern of the endogenous transcript. Representative results are shown from successful experiments and typical suboptimal experiments.

Whole Mount in Situ Hybridization of E8.5 to E11.5 Mouse Embryos

This whole mount in situ hybridization protocol discusses critical steps that ensure reproducible high quality results for gene expression studies in E8.5-E11.5 day old mouse embryos.

Whole mount in situ hybridization is a very informative approach for defining gene expression patterns in embryos. The in situ hybridization procedures ...

Analysis of Single-cell Gene Transcription by RNA Fluorescent In Situ Hybridization (FISH)

Adhesion of Plasmodium falciparum infected erythrocytes (IE) to human endothelial receptors during malaria infections is mediated by expression of PfEMP1 protein variants encoded by the var genes.
The haploid P. falciparum genome harbors approximately 60 different var genes of which only one has been believed to be transcribed per cell at a time during the blood stage of the infection. How such mutually exclusive regulation of var gene transcription is achieved is unclear, as is the identification of individual var genes or sub-groups of var genes associated with different receptors and the consequence of differential binding on the clinical outcome of P. falciparum infections. Recently, the mutually exclusive transcription paradigm has been called into doubt by transcription assays based on individual P. falciparum transcript identification in single infected erythrocytic cells using RNA fluorescent in situ hybridization (FISH) analysis of var gene transcription by the parasite in individual nuclei of P. falciparum IE1.
Here, we present a detailed protocol for carrying out the RNA-FISH methodology for analysis of var gene transcription in single-nuclei of P. falciparum infected human erythrocytes. The method is based on the use of digoxigenin- and biotin- labeled antisense RNA probes using the TSA Plus Fluorescence Palette System2 (Perkin Elmer), microscopic analyses and freshly selected P. falciparum IE. The in situ hybridization method can be used to monitor transcription and regulation of a variety of genes expressed during the different stages of the P. falciparum life cycle and is adaptable to other malaria parasite species and other organisms and cell types.

Analysis of Single-cell Gene Transcription by RNA Fluorescent In Situ Hybridization FISH

Fluorescent in situ hybridization (FISH) to identify mRNA transcripts in individual cells allows analysis of polygenic activity such as the simultaneous transcription of more than one member of the var multigene family in Plasmodium falciparum infected erythrocytes 1. The technique is adaptable and can be used on different types of genes, cells and organisms.

Adhesion of Plasmodium falciparum infected erythrocytes (IE) to human endothelial receptors during malaria infections is mediated by expression of PfEMP1 ...

Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

Mammalian DNA replication initiates at multiple sites along chromosomes at different times during S phase, following a temporal replication program. The specification of replication timing is thought to be a dynamic process regulated by tissue-specific and developmental cues that are responsive to epigenetic modifications. However, the mechanisms regulating where and when DNA replication initiates along chromosomes remains poorly understood. Homologous chromosomes usually replicate synchronously, however there are notable exceptions to this rule. For example, in female mammalian cells one of the two X chromosomes becomes late replicating through a process known as X inactivation1. Along with this delay in replication timing, estimated to be 2-3 hr, the majority of genes become transcriptionally silenced on one X chromosome. In addition, a discrete cis-acting locus, known as the X inactivation center, regulates this X inactivation process, including the induction of delayed replication timing on the entire inactive X chromosome. In addition, certain chromosome rearrangements found in cancer cells and in cells exposed to ionizing radiation display a significant delay in replication timing of &gt;3 hours that affects the entire chromosome2,3. Recent work from our lab indicates that disruption of discrete cis-acting autosomal loci result in an extremely late replicating phenotype that affects the entire chromosome4. Additional 'chromosome engineering' studies indicate that certain chromosome rearrangements affecting many different chromosomes result in this abnormal replication-timing phenotype, suggesting that all mammalian chromosomes contain discrete cis-acting loci that control proper replication timing of individual chromosomes5.
Here, we present a method for the quantitative analysis of chromosome replication timing combined with fluorescent in situ hybridization. This method allows for a direct comparison of replication timing between homologous chromosomes within the same cell, and was adapted from6. In addition, this method allows for the unambiguous identification of chromosomal rearrangements that correlate with changes in replication timing that affect the entire chromosome. This method has advantages over recently developed high throughput micro-array or sequencing protocols that cannot distinguish between homologous alleles present on rearranged and un-rearranged chromosomes. In addition, because the method described here evaluates single cells, it can detect changes in chromosome replication timing on chromosomal rearrangements that are present in only a fraction of the cells in a population.

Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

A quantitative method for the analysis of chromosome replication timing is described. The method utilizes BrdU incorporation in combination with fluorescent in situ hybridization (FISH) to assess replication timing of mammalian chromosomes. This technique allows for the direct comparison of rearranged and un-rearranged chromosomes within the same cell.

Mammalian DNA replication initiates at multiple sites along chromosomes at different times during S phase, following a temporal replication program. The ...

Whole Mount RNA Fluorescent in situ Hybridization of Drosophila Embryos

Assessing the expression pattern of a gene, as well as the subcellular localization properties of its transcribed RNA, are key features for understanding its biological function during development. RNA in situ hybridization (RNA-ISH) is a powerful method used for visualizing RNA distribution properties, be it at the organismal, cellular or subcellular levels 1. RNA-ISH is based on the hybridization of a labeled nucleic acid probe (e.g. antisense RNA, oligonucleotides) complementary to the sequence of an mRNA or a non-coding RNA target of interest 2. As the procedure requires primary sequence information alone to generate sequence-specific probes, it can be universally applied to a broad range of organisms and tissue specimens 3. Indeed, a number of large-scale ISH studies have been implemented to document gene expression and RNA localization dynamics in various model organisms, which has led to the establishment of important community resources 4-11. While a variety of probe labeling and detection strategies have been developed over the years, the combined usage of fluorescently-labeled detection reagents and enzymatic signal amplification steps offer significant enhancements in the sensitivity and resolution of the procedure 12. Here, we describe an optimized fluorescent in situ hybridization method (FISH) employing tyramide signal amplification (TSA) to visualize RNA expression and localization dynamics in staged Drosophila embryos. The procedure is carried out in 96-well PCR plate format, which greatly facilitates the simultaneous processing of large numbers of samples.

Whole Mount RNA Fluorescent in situ Hybridization of Drosophila Embryos

Here we describe a whole-mount fluorescent in situ hybridization (FISH) protocol for determining the expression and localization properties of RNAs expressed during embryogenesis in the fruit fly, Drosophila melanogaster.

Assessing  the expression pattern of a gene, as well as the subcellular localization  properties of its transcribed RNA, are key features for ...

RNA In situ Hybridization in Whole Mount Embryos and Cell Histology Adapted for Marine Elasmobranchs

Marine elasmobranchs are valued animal models for biomedical and genomic studies as they are the most primitive vertebrates to have adaptive immunity and have unique mechanisms for osmoregulation 1-3. As the most primitive living jawed-vertebrates with paired appendages, elasmobranchs are an evolutionarily important model, especially for studies in evolution and development. Marine elasmobranchs have also been used to study aquatic toxicology and stress physiology in relationship to climate change 4. Thus, development and adaptation of methodologies is needed to facilitate and expand the use of these primitive vertebrates to multiple biological disciplines. Here I present the successful adaptation of RNA whole mount in situ hybridization and histological techniques to study gene expression and cell histology in elasmobranchs.
Monitoring gene expression is a hallmark tool of developmental biologists, and is widely used to investigate developmental processes 5. RNA whole mount in situ hybridization allows for the visualization and localization of specific gene transcripts in tissues of the developing embryo. The expression pattern of a gene's message can provide insight into what developmental processes and cell fate decisions a gene may control. By comparing the expression pattern of a gene at different developmental stages, insight can be gained into how the role of a gene changes during development.
While whole mount in situ's provides a means to localize gene expression to tissue, histological techniques allow for the identification of differentiated cell types and tissues. Histological stains have varied functions. General stains are used to highlight cell morphology, for example hematoxylin and eosin for general staining of nuclei and cytoplasm, respectively. Other stains can highlight specific cell types. For example, the alcian blue stain reported in this paper is a widely used cationic stain to identify mucosaccharides. Staining of the digestive tract with alcian blue can identify the distribution of goblet cells that produce mucosaccharides. Variations in mucosaccharide constituents on short peptides distinguish goblet cells by function within the digestive tract 6. By using RNA whole mount in situ's and histochemical methods concurrently, cell fate decisions can be linked to gene-specific expression.
Although RNA in situ's and histochemistry are widely used by researchers, their adaptation and use in marine elasmobranchs have met limited and varied success. Here I present protocols developed for elasmobranchs and used on a regular basis in my laboratory. Although further modification of the RNA in situ's hybridization method may be needed to adapt to different species, the protocols described here provide a strong starting point for researchers wanting to adapt the use of marine elasmobranchs to their scientific inquiries.

RNA In situ Hybridization in Whole Mount Embryos and Cell Histology Adapted for Marine Elasmobranchs

By combining methods for RNA whole mount in situ hybridization and histology, gene expression can be linked with cell fate decisions in the developing embryo. These methods have been adapted to marine elasmobranchs and facilitate the use of these animals as model organisms for biomedical, toxicology and comparative studies.

Marine  elasmobranchs are valued animal models for biomedical and genomic studies as  they are the most primitive vertebrates to have adaptive immunity ...

High Resolution Whole Mount In Situ Hybridization within Zebrafish Embryos to Study Gene Expression and Function

This article focuses on whole-mount in situ hybridization (WISH) of zebrafish embryos. The WISH technology facilitates the assessment of gene expression both in terms of tissue distribution and developmental stage. Protocols are described for the use of WISH of zebrafish embryos using antisense RNA probes labeled with digoxigenin. Probes are generated by incorporating digoxigenin-linked nucleotides through in vitro transcription of gene templates that have been cloned and linearized. The chorions of embryos harvested at defined developmental stages are removed before incubation with specific probes. Following a washing procedure to remove excess probe, embryos are incubated with anti-digoxigenin antibody conjugated with alkaline phosphatase. By employing a chromogenic substrate for alkaline phosphatase, specific gene expression can be assessed. Depending on the level of gene expression the entire procedure can be completed within 2-3 days.

High Resolution Whole Mount In Situ Hybridization within Zebrafish Embryos to Study Gene Expression and Function

The zebrafish, a small tropical fish, has become a popular model for studying gene function during vertebrate development and disease. The temporal and spatial expression of target genes can be determined by in situ hybridization. Our improved protocol allows for the detection of low abundant transcripts with low non-specific background signal.

This article focuses on whole-mount in situ hybridization (WISH) of zebrafish embryos. The WISH technology facilitates the assessment of gene expression ...

Analysis of Apoptosis in Zebrafish Embryos by Whole-mount Immunofluorescence to Detect Activated Caspase 3

Whole-mount immunofluorescence to detect activated Caspase 3 (Casp3 assay) is useful to identify cells undergoing either intrinsic or extrinsic apoptosis in zebrafish embryos. The whole-mount analysis provides spatial information in regard to tissue specificity of apoptosing cells, although sectioning and/or colabeling is ultimately required to pinpoint the exact cell types undergoing apoptosis. The whole-mount Casp3 assay is optimized for analysis of fixed embryos between the 4-cell stage and 32 hr-post-fertilization and is useful for a number of applications, including analysis of zebrafish mutants and morphants, overexpression of mutant and wild-type mRNAs, and exposure to chemicals. Compared to acridine orange staining, which can identify apoptotic cells in live embryos in a matter of hours, Casp3 and TUNEL assays take considerably longer to complete (2-4 days). However, because of the dynamic nature of apoptotic cell formation and clearance, analysis of fixed embryos ensures accurate comparison of apoptotic cells across multiple samples at specific time points. We have also found the Casp3 assay to be superior to analysis of apoptotic cells by the whole-mount TUNEL assay in regard to cost and reliability. Overall, the Casp3 assay represents a robust, highly reproducible assay in which to analyze apoptotic cells in early zebrafish embryos.

Certain genetic perturbations or exposure to toxins can disrupt normal developmental processes leading to death of specific cell types. The analysis of activated Caspase 3 by whole-mount immunofluorescence in zebrafish embryos reveals stage- and tissue-specific localization of cells specifically undergoing apoptosis.

Whole-mount immunofluorescence to detect activated Caspase 3 (Casp3 assay) is useful to identify cells undergoing either intrinsic or extrinsic apoptosis ...