I wish to thank the many undergraduate students who have worked in my laboratory and contributed to the evolution of these protocols. NAT has received support from the Skidmore-Union Network, a project established with a NSF ADVANCE PAID grant.

I. RNA Whole Mount In situ Hybridization in Marine Elasmobranchs
1. Embryo Fixation and Preparation
<ol>
 <li>Skate embryos can be staged according to Ballard 7. Optimal stages for detection of gene expression depends on the tissue of interest. To track gene expression in the skate digestive tract, stages 27-30 are optimal 7.</li>
 <li>Dissect embryos into PBS, separating the embryos from the yolk sac.</li>
 <li>Fix in 30 ml of freshly made 4% paraformaldehyde (PF...

<ol>
	<li>Forester, R., Goldstein, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracellular+osmoregulatory+role+of+amino+acids+and+urea+in+marine+elasmobranchs.">Intracellular osmoregulatory role of amino acids and urea in marine elasmobranchs.</a> Am. J. Physiol. 230, 925-931 (1976).</li><li>Shuttleworth, T., Shuttleworth, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Physiology of elasmobranch fishes. , 171-194 (1988).</li><li>Yancey, P. H., Clark, M. E., Hand, S. C., Bowlus, R. D., Somero, G. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Living+with+water+stress:+evolution+of+osmolyte+systems.">Living with water stress: evolution of osmolyte systems.</a> Science. 217, 1214-1222 (1982).</li><li>Ballatori, N., Villalobos, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defining+the+molecular+and+cellular+basis+of+toxicity+using+comparative+models.">Defining the molecular and cellular basis of toxicity using comparative models.</a> Toxicl. Appl. Pharmacol. 183, 207-220 (2002).</li><li>Nieto, M. A., Patel, K., Wilkinson, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+hybridization+analysis+of+chick+embryos+in+whole+mount+and+tissue+sections.">In situ hybridization analysis of chick embryos in whole mount and tissue sections.</a> Methods Cell Biol. 51, 219-235 (1996).</li><li>Jass, J. R., Walsh, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+mucin+expression+in+the+gastrointestinal+tract:+a+review.">Altered mucin expression in the gastrointestinal tract: a review.</a> J Cell Mol Med. 5, 327-351 (2001).</li><li>Ballard, W. W., Mellinger, J., Lechenault, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+series+of+normal+stages+for+development+of+Scyliorhinus+canicula,+the+lesser+spotted+dogfish+(Chondrichthyes;+Scyliorhinidae).">A series of normal stages for development of Scyliorhinus canicula, the lesser spotted dogfish (Chondrichthyes; Scyliorhinidae).</a> J. Exp. Zool. 267, 318-336 (1993).</li><li>Echelard, 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=Sonic+hedgehog,+a+member+of+a+family+of+putative+signaling+molecules,+is+implicated+in+the+regulation+of+CNS+polarity.">Sonic hedgehog, a member of a family of putative signaling molecules, is implicated in the regulation of CNS polarity.</a> Cell. 75, 1417-1430 (1993).</li><li>Riddle, R. D., Johnson, R. L., Laufer, E., Tabin, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sonic+hedgehog+mediates+the+polarizing+activity+of+the+ZPA.">Sonic hedgehog mediates the polarizing activity of the ZPA.</a> Cell. 75, 1401-1416 (1993).</li><li>Theodosiou, N. A., Hall, D. A., Jowdry, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+acid+mucin+goblet+cell+distribution+and+Hox13+expression+patterns+in+the+developing+vertebrate+digestive+tract.">Comparison of acid mucin goblet cell distribution and Hox13 expression patterns in the developing vertebrate digestive tract.</a> J. Exp. Zool. B. Mol. Dev. Evol. 308, 442-453 (2007).</li><li>Sambrook, J., Russell, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ch.+7.">Ch. 7.</a> Molecular Cloning; A Laboratory Manual. 1, 7.82 (2001).</li><li>Zhang, G., Miyamoto, M. M., Cohn, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lamprey+type+II+collagen+and+Sox9+reveal+an+ancient+origin+of+the+vertebrate+collagenous+skeleton.">Lamprey type II collagen and Sox9 reveal an ancient origin of the vertebrate collagenous skeleton.</a> Proc. Natl. Acad. Sci. U.S.A. 103, 3180-3185 (2006).</li><li>Sheehan, D. C., Hrapchak, B. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Theory and practice of histotechnology. , (1980).</li><li>Theodosiou, N. A., Simeone, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+of+a+rudimentary+colon+in+the+elasmobranch,+Leucoraja+erinacea.">Evidence of a rudimentary colon in the elasmobranch, Leucoraja erinacea.</a> Dev. Genes Evol. 222, 237-243 (2012).</li><li>Filipe, M. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mucins+in+the+human+gastrointestinal+epithelium:+a+review.">Mucins in the human gastrointestinal epithelium: a review.</a> Invest. Cell Pathol. 2, 195-216 (1979).</li><li>Corfield, A. P., Wagner, S. A., Clamp, J. R., Kriaris, M. S., Hoskins, L. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mucin+degradation+in+the+human+colon:+production+of+sialidase,+sialate+O-acetylesterase,+N-acetylneuraminate+lyase,+arylesterase,+and+glycosulfatase+activities+by+strains+of+fecal+bacteria.">Mucin degradation in the human colon: production of sialidase, sialate O-acetylesterase, N-acetylneuraminate lyase, arylesterase, and glycosulfatase activities by strains of fecal bacteria.</a> Infect. Immun. 60, 3971-3978 (1992).</li><li>Reid, B. 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=Flow-cytometric+and+histological+progression+to+malignancy+in+Barrett's+esophagus:+prospective+endoscopic+surveillance+of+a+cohort.">Flow-cytometric and histological progression to malignancy in Barrett's esophagus: prospective endoscopic surveillance of a cohort.</a> Gastroenterology. 102, 1212-1219 (1992).</li><li>Mowry, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+staining+of+pancreatic+beta-cell+granules.+Evolution+and+present+status.">Selective staining of pancreatic beta-cell granules. Evolution and present status.</a> Arch. Pathol. Lab Med. 107, 464-468 (1983).</li><li>Roberts, D. J., Smith, D. M., Goff, D. J., Tabin, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epithelial-mesenchymal+signaling+during+the+regionalization+of+the+chick+gut.">Epithelial-mesenchymal signaling during the regionalization of the chick gut.</a> Development. 125, 2791-2801 (1998).</li></ol>

The protocols presented are classic methods for monitoring gene expression and identifying differentiated cell types, and have been adapted for use in marine elasmobranchs. Further modifications of these protocols may be needed to adapt to different elasmobranch species.
The most common concern regarding RNA whole mount in situ's is the risk of RNase contamination and thereby the degradation of the RNA probe and endogenous messages. Two aspects need to be considered: the synthe...

<table border="1">
 <tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments </td>
 </tr>
 <tr>
 <td>10 x transcription buffer</td>
 <td>Roche</td>
 <td>11-465-384-001</td>
 <td></td>
 </tr>
 <tr>
 <td>DIG-RNA labeling mix</td>
 <td>Roche</td>
 <td>11-277-073-910</td>
 <td></td>
 </tr>
 <tr>
 <td>RNAse inhibitor</td>
 <td>Roche</td>
 <td>03-335-399-001</td>
 <td></td>
 </tr>
 <tr>
 <td>RNA polymerase - SP6</td>
 <td>Roche</td>
 <td>10-810-274-001</td>
 <td></td>
 </tr>
 <tr>
 <td>DNAseI, RNAse-free </td>
 <td>Roche</td>
 <td>10-776-785-001</td>
 <td></td>
 </tr>
 <tr>
 <td>Yeast RNA</td>
 <td>Invitrogen</td>
 <td>15401-029</td>
 <td></td>
 </tr>
 <tr>
 <td>CHAPS</td>
 <td>EMD-Millipore</td>
 <td>220201</td>
 <td></td>
 </tr>
 <tr>
 <td>heparin</td>
 <td>Sigma-Aldrich</td>
 <td>H4784</td>
 <td></td>
 </tr>
 <tr>
 <td>DEPC (diethyl pyrocarbonate)</td>
 <td>Research Organics</td>
 <td>2106D</td>
 <td></td>
 </tr>
 <tr>
 <td>Moria Perforated Spoon</td>
 <td>Fine Science Tools</td>
 <td>10370-17</td>
 <td></td>
 </tr>
 <tr>
 <td>Netwell inserts</td>
 <td>Electron Microscopy Sciences</td>
 <td>64713-00</td>
 <td>Netwells for use in 6-well tissue culture dishes</td>
 </tr>
 <tr>
 <td>6-well tissue culture plate</td>
 <td>Corning</td>
 <td>3516</td>
 <td></td>
 </tr>
 <tr>
 <td>Glass scintillation vials with screw-cap lids</td>
 <td>Weaton Science Products</td>
 <td>986540</td>
 <td></td>
 </tr>
 <tr>
 <td>formamide</td>
 <td>Fisher</td>
 <td>BP227500</td>
 <td></td>
 </tr>
 <tr>
 <td>Proteinase K</td>
 <td>Invitrogen</td>
 <td>59895 (AM2542)</td>
 <td></td>
 </tr>
 <tr>
 <td>NBT</td>
 <td></td>
 <td>11585029001</td>
 <td></td>
 </tr>
 <tr>
 <td>BCIP</td>
 <td>Roche</td>
 <td>11585002001</td>
 <td></td>
 </tr>
 <tr>
 <td>Hydrogen peroxide, 30%</td>
 <td>EMD</td>
 <td>HX0635-1</td>
 <td></td>
 </tr>
 <tr>
 <td>Sheep serum</td>
 <td>VWR</td>
 <td>101301-478</td>
 <td></td>
 </tr>
 <tr>
 <td>glutaraldehyde</td>
 <td>Sigma-Aldrich</td>
 <td>G5882</td>
 <td></td>
 </tr>
 <tr>
 <td>tRNA</td>
 <td>Roche</td>
 <td>10-109-541-001</td>
 <td></td>
 </tr>
 <tr>
 <td>Anti-DIG Fab Fragments</td>
 <td>Roche</td>
 <td>1137-6623</td>
 <td></td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>Table 3. Reagents and equipment for RNA whole mount in situ's.</td>
 </tr>
 <tr>
 <td>1% Alcian Blue 8GS, pH 2.5</td>
 <td>Electron Microscopy Sciences</td>
 <td>26323-01</td>
 <td></td>
 </tr>
 <tr>
 <td>Nuclear Fast Red</td>
 <td>Electron Microscopy Sciences</td>
 <td>26078-05</td>
 <td></td>
 </tr>
 <tr>
 <td>DPX Mountant</td>
 <td>Electron Microscopy Sciences</td>
 <td>13510</td>
 <td></td>
 </tr>
 <tr>
 <td>Paraffin (Paraplast X-tra)</td>
 <td>McCormick Scientific</td>
 <td>39503002</td>
 <td></td>
 </tr>
 <tr>
 <td>10% Formalin, NBF</td>
 <td>VWR</td>
 <td>95042-908</td>
 <td></td>
 </tr>
 <tr>
 <td>Glass scintillation vials with screw-cap lids</td>
 <td>Weaton Science Products</td>
 <td>986540</td>
 <td></td>
 </tr>
 <tr>
 <td>Stainless steal base molds</td>
 <td>Tissue-Tek</td>
 <td>4161-4165</td>
 <td>Multiple sizes available.</td>
 </tr>
 <tr>
 <td>Cassettes </td>
 <td>Tissue-Tek</td>
 <td>4170</td>
 <td></td>
 </tr>
 <tr>
 <td>Slide warmer</td>
 <td>Fisher-Scientific</td>
 <td>12-594Q</td>
 <td></td>
 </tr>
 <tr>
 <td>Tissue Embedder</td>
 <td>Leica Microsystems</td>
 <td>EG1160</td>
 <td></td>
 </tr>
 <tr>
 <td>Microtome, rotary</td>
 <td>Leica Microsystems</td>
 <td>RM2235</td>
 <td></td>
 </tr>
 <tr>
 <td>Tissue-Tek Slide Staining Set</td>
 <td>Electron Microscopy Sciences</td>
 <td>62540-01</td>
 <td></td>
 </tr>
 <tr>
 <td>Tissue-Tek 24-Slide Holder</td>
 <td>Electron Microscopy Sciences</td>
 <td>62543-06</td>
 <td></td>
 </tr>
 <tr>
 <td>Superfrost*Plus slides</td>
 <td>Fisherbrand</td>
 <td>12-550-17</td>
 <td></td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>Table 4. Reagents and equipment for Alcian Blue stain.</td>
 </tr>
 </tbody>
</table>

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.

Examples of alcian blue staining in different regions of the L. erinacea digestive tract are shown in Figure 2. Acid mucin containing globlet cells are clearly visible by the alcian blue stain throughout the digestive tract. The distribution of acid mucins differs in the different regions of the digestive tract, thus reflecting differences in function. Acidic mucins are sparsely produced in the spiral intestine and cloaca, while a high concentration of acid mucins are detected in the dista...

Watch this Scientific Journal Video about RNA In situ Hybridization in Whole Mount Embryos and Cell Histology Adapted for Marine Elasmobranchs at JoVE.com

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.

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 ...

rna-situ-hybridization-whole-mount-embryos-cell-histology-adapted-for

Research

JoVE Journal

Biology

12.6K Views.  Union College. 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.