This work was supported by the National Science Foundation grant IOS-0817658.

The zebrafish procedures in this protocol have been approved by the Institutional Animal Care and Use Committee (IACUC) at Virginia Commonwealth University.
1. Preparation of Reagents
<ol>
	<li>4% PFA/PBS. Weigh 8 g of paraformaldehyde (PFA) in the fume hood. While still in the fume hood, dissolve the dry PFA in ~80 ml distilled H2O with stirring and heating to 50 &#176;C. While stirring, add 3 - 10 drops of fresh 1N NaOH until PFA is completely dissolved and solution clarifies.&#160;Remove from heat and add 100 ml 2x phosphate buffered saline (PBS). Bring volume to 200 ml&#160;with distilled H2O. Cool to RT&#160;and confirm pH of 7.4 before use. Store in the dark at 4 &#176;C but use within one week.</li>
	<li>Use 100% methanol without any supplements. Use 95% ethanol without any supplements.</li>
	<li>Prepare Phosphate-buffered Tween (PBT). Supplement Phosphate-buffered saline (PBS) with 0.1% Tween-20. Add 0.5 ml of a 20% Tween-20 stock solution to 100 ml&#160;1x PBS. Store at RT.</li>
	<li>Prepare Phosphate-buffered Triton-X (PBTx). Supplement PBS with 0.1% Triton X-100. Add 0.5 ml of a 20% Triton X-100 stock to&#160;100 ml of PBS. Store at RT.</li>
	<li>Prepare 10% NGS/PBTx. Normal goat serum (NGS) blocks non-specific binding sites. Store NGS in aliquots at -20 &#176;C. To use, add 1 ml to 9 ml PBTx.</li>
	<li>Prepare 50% glycerol/PBS. Mix thoroughly equal parts of 2x PBS and 100% glycerol. Store at RT.</li>
</ol>
2. Embryo Fixation
<ol>
	<li>Breeding.&#160;Obtain wild type (AB and WIK) or transgenic (e.g., &#946;-actin:CAAX-GFP) embryos through natural matings. If desired, inject embryos with constructs or morpholinos, as described.15,16</li>
	<li>Raise embryos.&#160;Collect embryos and incubate at 28.5 &#176;C in the presence of 0.003% 1-phenyl-2-thiourea (PTU) to block pigmentation as described.17</li>
	<li>Fix.&#160;When embryos have reached the desired developmental stage,18,&#160;anesthetize the embryos using MESAB, remove as much system water as possible and add fresh 4% PFA/PBS for 3 - 4 hr&#160;at RT.&#160;NOTE: At times less than 20 hr&#160;post fertilization (hpf), fix prior to dechorionation. At times after 20 hpf, dechorionate prior to fixation using two pairs of fine point forceps under a dissecting microscope.</li>
	<li>Changing solutions.&#160;Transfer embryos using a wide bore pipet, as described.17 Change solutions in 1.5 ml capped microcentrifuge tubes, simply by allowing embryos to settle by gravity without centrifugation.</li>
	<li>Post-fixative.&#160;After 3 - 4 hr, remove PFA/PBS, replace with 100% methanol and store at -20 &#176;C for at least 48 hr. NOTE: For maximal P-CaMK-II immunoreactivity, limit total methanol storage time to one week.</li>
</ol>
3. Immunostaining Whole Embryos
<ol>
	<li>Place a minimum of 10 embryos for each experimental condition in capped 1.5 ml microcentrifuge tube, and label them.</li>
	<li>Allow the embryos to settle. Remove and discard methanol and rehydrate with progressive washes containing 0.5 ml of decreasing concentrations of ethanol, as indicated in the next step. Each step is a 5 min wash with rocking.</li>
	<li>Progressively rehydrate with these 5 solutions: 66% ethanol/33% PBTx, 33% ethanol/66% PBTx, 100% PBTx, 100% PBTx (this is the first repeat of PBTx), 100% PBTx (this is the second repeat of PBTx).</li>
	<li>Remove last PBTx wash. Add 0.5 ml 10% NGS/PBTx. Incubate for at least 1 hr at RT&#160;with gentle rocking and then remove and discard solution.</li>
	<li>Prepare primary antibody solution by diluting in 10% NGS/PBTx. If co-immunostaining, use higher affinity antibody first. For this study, incubate with the mouse anti-acetylated tubulin monoclonal antibody diluted 1:500. For example, if there are 10 samples, combine 6 &#956;l of the stock antibody solution with 3 ml&#160;of 10% NGS/PBTx and then distribute 0.3 ml of this into each tube.</li>
	<li>Add 0.2 - 0.5 ml of the diluted primary antibody to each tube to immerse all embryos. Incubate with gentle rocking O/N&#160;at RT.</li>
	<li>In the morning, remove and discard antibody solution. Add 0.5 ml 2% NGS/PBTx to wash away excess primary antibody. Gently rock for 5 min. Remove and discard solution. Repeat twice.</li>
	<li>Dim overhead lights and dilute the appropriate fluorescently-conjugated secondary antibody in 10% NGS/PBTx so that each condition contains at least 0.5 ml. With the mouse anti-acetylated tubulin primary antibody, use the green-fluorescent dye goat anti-mouse IgG at a 1:500 dilution.</li>
	<li>Incubate secondary antibody for 4 hr with gentle rocking at RT in the dark. From now on, process the samples under dimmed lights and incubate in a dark container or by wrapping in aluminum foil.</li>
	<li>At the end of the incubation, remove and discard the secondary antibody solution. Add 0.5 ml 2% NGS/PBTx to wash. Gently rock for 5 min. Remove and discard solution. Repeat twice.</li>
	<li>If co-immunostaining, obtain the second primary antibody from a different species than the first primary antibody. In these studies, follow the rabbit anti-phospho CaMK-II antibody by the red-fluorescent dye-conjugated goat anti-rabbit IgG secondary antibody.</li>
	<li>Dilute rabbit anti-phospho CaMK-II antibody 1:20. For each tube of embryos, suspend in 0.3 ml 10% NGS/PBTx, then add 15 &#956;l of the stock antibody solution.</li>
	<li>Ensure that embryos are immersed and lights are dimmed. Incubate with gentle rocking O/N at RT in the dark.</li>
	<li>In the morning under dim lights, remove and discard antibody solution. Add 0.5 ml 2% NGS/PBTx. Gently rock for 5 min. Remove and discard solution. Repeat twice.</li>
	<li>Keep overhead lights dim and dilute enough of the appropriate fluorescently-conjugated secondary antibody so that each condition contains at least 0.5 ml. In this study, dilute the red-fluorescent dye-conjugated goat anti-rabbit IgG secondary antibody (red channel) 1:500 in 10% NGS/PBTx.</li>
	<li>Incubate second secondary antibody for 4 hr with gentle rocking at RT in the dark.</li>
	<li>At the end of this incubation and under dim lights, remove and discard the secondary antibody solution. Add 0.5 ml PBTx. Gently rock for 5 min. Remove and discard solution. Repeat twice. Store in either PBTx or 50% glycerol/PBS depending on the imaging procedure.</li>
</ol>
4. Confocal Imaging and Processing
<ol>
	<li>Mount embryos for imaging. Place 1 - 5 embryos on a glass slide. Create a chamber between the main coverslip and the slide using coverslip fragments on each side of the chamber. Typically, four #1 coverslips are used to make these spacer stacks without sealing. 
	NOTE: No mounting medium is necessary.</li>
	<li>Use a 100X oil immersion objective to bring single embryo into focus using transmitted light. Turn off light. Turn on confocal microscope. Ensure that appropriate lasers (green and/or red) are turned on and remote focus accessary is engaged.</li>
	<li>Turn on the confocal program. In the &#34;Acquire bar,&#34; select the proper objective. In the &#34;XY Basic&#34; bar, set image size to 1,024 by clicking the 1,024 button.</li>
	<li>In the &#34;Laser and Detector&#34; bar, click on the red 488 box and the green 568 box to turn on laser and detector for each channel. Set pinhole to medium and adjust the gain in the &#34;Gain&#34; bar of each channel to visualize.</li>
	<li>In the &#34;Acquire Settings&#34; bar, click &#34;Live&#34; to begin acquiring images. In the &#34;View Settings&#34; bar, uncheck the &#34;Force Integral Zoom&#34; box to center in the &#34;Live&#34; window.</li>
	<li>In the &#34;Acquire Settings&#34; bar, under the &#34;Z&#34; tab, step through the layers of the image. After selecting the number of optical sections to incorporate into the image, move to some point in the &#34;center&#34; of the z-plane.</li>
	<li>Under the &#34;Z&#34; tab, click the small red &#34;Reference&#34; box. This will zero the RFA at the point chosen as the &#34;center&#34;. In the box labeled &#34;Step Size&#34;, select the thickness of the layers (between 0.25 &#181;m and 2.0 &#181;m is ideal). Pay attention to the &#34;File Size&#34; box and try to limit to 1GB. 
	NOTE: Typically, up to 40 optical sections of 0.5 - 1.0 &#956;m are obtained, but the number of sections can be determined empirically.</li>
	<li>To find the top extreme of the image, click the circle next to &#34;Top&#34; and move through the z layers. Now click the circle next to &#34;Bottom&#34;, the computer will take the image back to the layer as the center. Again move through the layers to find the bottom extreme of the image.</li>
	<li>Click on &#34;Live&#34; again in the &#34;Acquire Settings&#34; box to stop the laser acquisition. In this panel, click the red boxes labeled Average and Z-stack. These boxes will turn green.</li>
	<li>In the &#34;Acquire Settings&#34; box, click &#34;Single&#34; to acquire the entire series of images. You can monitor the progress as it scans in both channels and through the entire z-stack.</li>
	<li>To save, click on the volume window and click &#34;save as&#34; and name the file. Save as an &#34;.ids&#34; file. To volume render the file while the z-stack is still open, select the Data pull down menu and click on &#34;volume render&#34;. Save the rendered file as a tiff file. This is the projected image that are shown in this publication.</li>
</ol>

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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CaMK-II+is+a+PKD2+target+that+promotes+pronephric+kidney+development+and+stabilizes+cilia.">CaMK-II is a PKD2 target that promotes pronephric kidney development and stabilizes cilia.</a> Development. 138, 3387-3397 (2011).</li><li>Rothschild, S. C., 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=CaMK-II+activation+is+essential+for+zebrafish+inner+ear+development+and+acts+through+Delta-Notch+signaling.">CaMK-II activation is essential for zebrafish inner ear development and acts through Delta-Notch signaling.</a> Dev Biol. 381, 179-188 (2013).</li><li>Yuan, S., Sun, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microinjection+of+mRNA+and+morpholino+antisense+oligonucleotides+in+zebrafish+embryos.">Microinjection of mRNA and morpholino antisense oligonucleotides in zebrafish embryos.</a> J Vis Exp. , e1113 (2009).</li><li>Rosen, J. N., Sweeney, M. F., Mably, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microinjection+of+zebrafish+embryos+to+analyze+gene+function.">Microinjection of zebrafish embryos to analyze gene function.</a> J Vis Exp. , e1115 (2009).</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 (Brachydanio rerio). , (1993).</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>Obara, 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=Polycystin-2+immunolocalization+and+function+in+zebrafish.">Polycystin-2 immunolocalization and function in zebrafish.</a> J Am Soc Nephrol. 17, 2706-2718 (2006).</li><li>Chitramuthu, B. P., Bennett, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+resolution+whole+mount+in+situ+hybridization+within+zebrafish+embryos+to+study+gene+expression+and+function.">High resolution whole mount in situ hybridization within zebrafish embryos to study gene expression and function.</a> J Vis Exp. , e50644 (2013).</li><li>Thisse, C., Thisse, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+in+situ+hybridization+to+whole-mount+zebrafish+embryos.">High-resolution in situ hybridization to whole-mount zebrafish embryos.</a> Nature. 3, 59-69 (2008).</li><li>Harris, P., Osborn, M., Weber, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distribution+of+tubulin-containing+structures+in+the+egg+of+the+sea+urchin+Strongylocentrotus+purpuratus+from+fertilization+through+first+cleavage.">Distribution of tubulin-containing structures in the egg of the sea urchin Strongylocentrotus purpuratus from fertilization through first cleavage.</a> J Cell Biol. 84, 668-679 (1980).</li></ol>

The authors declare that they have no competing financial interests.

The PFA/methanol method was developed in this laboratory with the primary objective of optimizing the immunolocalization of the phospho-T287-CaMK-II epitope during zebrafish development. This method successfully localized P-CaMK-II during the formation of several ciliated organs including the zebrafish KV,12 inner ear14 and kidney.13 Particularly at the KV stage, this technique was necessary. The success of this method is likely due to a combination of a) minimization of autofl...

The techniques described here are the outcome of studies that have sought to define downstream targets of Ca2+ signals during events that occur during early development, including fertilization, gastrulation, somitogenesis and trunk, eye, brain and organ formation.1-3 The original discoveries of embryonic Ca2+ signaling were dependent on the use of natural and engineered Ca2+ indicators, such as aequorin4 and fura-2.5 Even with current technology, the detection of transient elevations of Ca2+ requires cumbersome analytical tools and does not reveal the targets of such Ca2+ signals. 
This laboratory investigates Ca2+ signals that act through the Ca2+/calmodulin-dependent (multifunctional) protein kinase known as CaMK-II, an enzyme that is enriched in the central nervous system and originally identified as a regulator of long-term potentiation.6 CaMK-II is not brain-specific, is widely expressed and highly conserved throughout the entire lifespan and bodies of species throughout the animal kingdom, including invertebrates.7,8 CaMK-II has the unique capability of sustaining its own activity even after Ca2+ levels have diminished due to its ability to autophosphorylate at Thr287. In this autophosphorylated state, CaMK-II remains active in a Ca2+/CaM-independent manner, until dephosphorylated.6 Thus, the localization of phosphorylated CaMK-II (Thr287) can identify cells in which natural, relevant Ca2+ elevations have occurred. 
An antibody against autophosphorylated (P-Thr287) mammalian CaMK-II has been well-characterized and was initially used to localize activated CaMK-II in brain tissue.9 Zebrafish (Danio rerio) have seven CaMK-II genes10,11 whose protein products contain a sequence of MHRQE[pT287]VECLK in this region.10,11 This sequence is very similar to the phosphopeptide antigen used to create this rabbit polyclonal antibody (MHRQE[pT]VDCLK; Upstate/Millipore) and therefore it was not a complete surprise that this antibody cross-reacted with zebrafish CaMK-II. This laboratory showed that this antibody reacts with zebrafish CaMK-II in proportion to autophosphorylation and Ca2+/CaM-independent activity.12 Additional pan-specific CaMK-II antibodies have also been shown to cross-react with zebrafish CaMK-II.13
This antibody has been used to demonstrate that zebrafish CaMK-II is preferentially activated in cells on one side of the zebrafish Kupffer's Vesicle (KV), the ciliated organ necessary for establishment of left/right asymmetry.12 This antibody was used to demonstrate that CaMK-II is transiently activated in four adjacent cells on the left side of the KV during the exact same developmental phase that organ positioning is determined.12 In addition to the Kupffer's Vesicle (KV), autophosphorylated (P-T287) was also located in specific intracellular sites in other ciliated tissues including the kidney, neuromasts, and inner ear.12,13 In the zebrafish kidney, P-T287-CaMK-II is enriched along the apical border of ciliated ductal cells and within cloacal cilia where it influences their assembly.13 Finally, in the developing inner ear, P-T287-CaMK-II is intensely concentrated at the base of cilia and influences cell differentiation through the Delta-Notch signal pathway.14 In summary, the detection of activated CaMK-II has pinpointed sites of intracellular Ca2+ release and illuminated potential new signaling pathways.
These discoveries were completely dependent on developing a sensitive and accurate method to localize activated (P-T287-autophosphorylated) CaMK-II. The methods to fix and immunostain the zebrafish KV, kidney and inner ear are described. The limitations of this technique are also described. These techniques should be useful to any investigator who seeks to obtain high-resolution images in two fluorescent channels of not just phospho-epitopes, but any epitope, during early vertebrate development.

<table><tbody><tr><td>1-phenyl-2-thiourea (PTU)</td><td>Sigma</td><td>P-7629</td><td>0.12% Stock solution. Dilute 1:40 in system water</td></tr><tr><td>Alexa488 anti-mouse IgG</td><td>Life Technologies</td><td>A11001</td><td>Goat polyclonal, use at 1:500</td></tr><tr><td>Alexa488 anti-rabbit IgG</td><td>Life Technologies</td><td>A11008</td><td>Goat polyclonal, use at 1:500</td></tr><tr><td>Alexa488 phalloidin</td><td>Life Technologies</td><td>A12379</td><td>Preferentially binds to F-actin</td></tr><tr><td>Alexa568 anti-mouse IgG</td><td>Life Technologies</td><td>A11004</td><td>Goat polyclonal, use at 1:500</td></tr><tr><td>Alexa568 anti-rabbit IgG</td><td>Life Technologies</td><td>A11011</td><td>Goat polyclonal, use at 1:500</td></tr><tr><td>anti-acetylated &amp;#945;-tubulin</td><td>Sigma</td><td>T7451</td><td>Mouse monoclonal, use at 1:500</td></tr><tr><td>anti-phospho-T&lt;sup&gt;287&lt;/sup&gt; CaMK-II</td><td>EMD Millipore</td><td>06-881</td><td>Rabbit polyclonal, use at 1:20</td></tr><tr><td>anti-total CaMK-II</td><td>BD Biosciences</td><td>611292</td><td>Mouse monoclonal, use at 1:20</td></tr><tr><td>Ethanol</td><td>Fisher</td><td>S96857</td><td>Lab grade, 95% denatured</td></tr><tr><td>Forceps</td><td>Fine Science Tools</td><td>11252-20</td><td>Dumont #5</td></tr><tr><td>Glass coverslips</td><td>VWR</td><td>16004-330</td><td>#1&amp;nbsp; thickness</td></tr><tr><td>Glass microscope slides</td><td>Fisher</td><td>12-550-15</td><td>Standard glass slides</td></tr><tr><td>Methanol</td><td>Fisher</td><td>A411</td><td>Store in freezer</td></tr><tr><td>Microcentrifuge tubes</td><td>VWR</td><td>20170-038</td><td>capped tubes, not sterile</td></tr><tr><td>Normal goat serum</td><td>Life Technologies</td><td>16210-064</td><td>Aliquot 1 ml tubes, store in freezer</td></tr><tr><td>Paraformaldehyde</td><td>Sigma</td><td>P-6148</td><td>Reagent grade, crystalline</td></tr><tr><td>Phosphate buffered saline (PBS)</td><td>Quality Biological</td><td>119-069-131</td><td>10x stock solution or made in lab</td></tr><tr><td>Triton X-100</td><td>Sigma</td><td>BP-151</td><td>10% solution in water, store at RT</td></tr><tr><td>Tween-20</td><td>Life Technologies</td><td>85113</td><td>10% solution in water, store at RT</td></tr><tr><td>Compound microscope</td><td>Nikon</td><td>E-600</td><td>Mount on vibration-free table</td></tr><tr><td>C1 Plus two-laser scanning confocal</td><td>Nikon</td><td>C1 Plus</td><td>Run by EZ-C1 program, but upgrades use &quot;Elements&quot;</td></tr></tbody></table>

immunostaining phospho-epitopes in ciliated organs of whole mount zebrafish embryos

The rapid proliferation of cells, the tissue-specific expression of genes and the emergence of signaling networks characterize early embryonic development of all vertebrates. The kinetics and location of signals - even within single cells - in the developing embryo complements the identification of important developmental genes. Immunostaining techniques are described that have been shown to define the kinetics of intracellular and whole animal signals in structures as small as primary cilia. The techniques for fixing, imaging and processing images using a laser-scanning confocal compound microscope can be completed in as few as 36 hr.
Zebrafish (Danio rerio) is a desirable organism for investigators who seek to conduct studies in a vertebrate species that is affordable and relevant to human disease. Genetic knockouts or knockdowns must be confirmed by the loss of the actual protein product. Such confirmation of protein loss can be achieved using the techniques described here. Clues into signaling pathways can also be deciphered by using antibodies that are reactive with proteins that have been post-translationally modified by phosphorylation. Preserving and optimizing the phosphorylated state of an epitope is therefore critical to this determination and is accomplished by this protocol.
This study describes techniques to fix embryos during the first 72 hr of development and co-localize a variety of relevant epitopes with cilia in the Kupffer&#39;s Vesicle (KV), the kidney and the inner ear. These techniques are straightforward, do not require dissection and can be completed in a relatively short period of time. Projecting confocal image stacks into a single image is a useful means of presenting these data.

Optimal Conditions for Visualizing Phospho-epitopes
Methods describing the immunolocalization of protein epitopes in zebrafish embryos have been relatively sparse compared to those for localizing mRNAs via in situ hybridization. Fixatives used in localizing protein epitopes in ciliated cells of zebrafish embryos have included 4% PFA/PBS and Dent&#39;s fixative, which is a mixture of methanol and DMSO.<s...

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Immunostaining Phospho-epitopes in Ciliated Organs of Whole Mount Zebrafish Embryos

Techniques are described to immunostain phospho-epitopes in whole zebrafish embryos and then conduct two-color fluorescent confocal localization in cellular structures as small as primary cilia. The techniques for fixing and imaging can define the location and kinetics of the appearance or activation of specific proteins.

The rapid proliferation of cells, the tissue-specific expression of genes and the emergence of signaling networks characterize early embryonic development ...

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Chemistry

8.0K Views.  Virginia Commonwealth University. Techniques are described to immunostain phospho-epitopes in whole zebrafish embryos and then conduct two-color fluorescent confocal localization in cellular structures as small as primary cilia. The techniques for fixing and imaging can define the location and kinetics of the appearance or activation of specific proteins.

Video: Immunostaining Phospho-epitopes in Ciliated Organs of Whole Mount Zebrafish Embryos

High Precision Zinc Isotopic Measurements Applied to Mouse Organs

We present a procedure to measure with high precision zinc isotope ratios in mouse organs. Zinc is composed of 5 stable isotopes (64Zn, 66Zn, 67Zn, 68Zn and 70Zn) which are naturally fractionated between mouse organs. We first show how to dissolve the different organs in order to free the Zn atoms; this step is realized by a mixture of HNO3 and H2O2. We then purify the zinc atoms from all the other elements, in particular from isobaric interferences (e.g., Ni), by anion-exchange chromatography in a dilute HBr/HNO3 medium. These first two steps are performed in a clean laboratory using high purity chemicals. Finally, the isotope ratios are measured by using a multi-collector inductively-coupled-plasma mass-spectrometer, in low resolution. The samples are injected using a spray chamber and the isotopic fractionation induced by the mass-spectrometer is corrected by comparing the ratio of the samples to the ratio of a standard (standard bracketing technique).&#160;This full typical&#160;procedure produces an isotope ratio with a 50 ppm (2 s.d.) reproducibility.

We present the technique to measure with high precision zinc isotope ratios in mouse organs.

We present a procedure to measure with high precision zinc isotope ratios in mouse organs. Zinc is composed of 5 stable isotopes (64Zn, 66Zn, 67Zn, 68Zn ...

Visualizing Multiciliated Cells in the Zebrafish Through a Combined Protocol of Whole Mount Fluorescent In Situ Hybridization and Immunofluorescence

In recent years, the zebrafish embryo has emerged as a popular model to study developmental biology due to traits such as ex utero embryo development and optical transparency. In particular, the zebrafish embryo has become an important organism to study vertebrate kidney organogenesis as well as multiciliated cell (MCC) development. To visualize MCCs in the embryonic zebrafish kidney, we have developed a combined protocol of whole-mount fluorescent in situ hybridization (FISH) and whole mount immunofluorescence (IF) that enables high resolution imaging. This manuscript describes our technique for co-localizing RNA transcripts and protein as a tool to better understand the regulation of developmental programs through the expression of various lineage factors.

Visualizing Multiciliated Cells in the Zebrafish Through a Combined Protocol of Whole Mount Fluorescent In Situ Hybridization and Immunofluorescence

Cilia development is vital to proper organogenesis. This protocol describes an optimized method to label and visualize ciliated cells of the zebrafish.

In recent years, the zebrafish embryo has emerged as a popular model to study developmental biology due to traits such as ex utero embryo development and ...

Developmental Biology

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.

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.

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

Biology

Whole Mount Immunohistochemistry in Zebrafish Embryos and Larvae

Immunohistochemistry is a widely used technique to explore protein expression and localization during both normal developmental and disease states. Although many immunohistochemistry protocols have been optimized for mammalian tissue and tissue sections, these protocols often require modification and optimization for non-mammalian model organisms. Zebrafish are increasingly used as a model system in basic, biomedical, and translational research to investigate the molecular, genetic, and cell biological mechanisms of developmental processes. Zebrafish offer many advantages as a model system but also require modified techniques for optimal protein detection. Here, we provide our protocol for whole-mount fluorescence immunohistochemistry in zebrafish embryos and larvae. This protocol additionally describes several different mounting strategies that can be employed and an overview of the advantages and disadvantages each strategy provides. We also describe modifications to this protocol to allow detection of chromogenic substrates in whole mount tissue and fluorescence detection in sectioned larval tissue. This protocol is broadly applicable to the study of many developmental stages and embryonic structures.

Here, we present a protocol for fluorescent antibody-mediated detection of proteins in whole preparations of zebrafish embryos and larvae.

Immunohistochemistry is a widely used technique to explore protein expression and localization during both normal developmental and disease states. ...

Single Cell Fate Mapping in Zebrafish

The ability to differentially label single cells has important implications in developmental biology. For instance, determining how hematopoietic, lymphatic, and blood vessel lineages arise in developing embryos requires fate mapping and lineage tracing of undifferentiated precursor cells. Recently, photoactivatable proteins which include: Eos1, 2, PAmCherry3, Kaede4-7, pKindling8, and KikGR9, 10 have received wide interest as cell tracing probes. The fluorescence spectrum of these photosensitive proteins can be easily converted with UV excitation, allowing a population of cells to be distinguished from adjacent ones. However, the photoefficiency of the activated protein may limit long-term cell tracking11. As an alternative to photoactivatable proteins, caged fluorescein-dextran has been widely used in embryo model systems7, 12-14. Traditionally, to uncage fluorescein-dextran, UV excitation from a fluorescence lamp house or a single photon UV laser has been used; however, such sources limit the spatial resolution of photoactivation. Here we report a protocol to fate map, lineage trace, and detect single labeled cells. Single cells in embryos injected with caged fluorescein-dextran are photoactivated with near-infrared laser pulses produced from a titanium sapphire femtosecond laser. This laser is customary in all two-photon confocal microscopes such as the LSM 510 META NLO microscope used in this paper. Since biological tissue is transparent to near-infrared irradiation15, the laser pulses can be focused deep within the embryo without uncaging cells above or below the selected focal plane. Therefore, non-linear two-photon absorption is induced only at the geometric focus to uncage fluorescein-dextran in a single cell. To detect the cell containing uncaged fluorescein-dextran, we describe a simple immunohistochemistry protocol16 to rapidly visualize the activated cell. The activation and detection protocol presented in this paper is versatile and can be applied to any model system. 
Note: The reagents used in this protocol can be found in the table appended at the end of the article.

A method is described to photoactivate single cells containing a caged fluorescent protein using two-photon absorption from a Ti:Sapphire femtosecond laser oscillator. To fate map the photoactivated cell, immunohistochemistry is used. This technique can be applied to any cell type.

The ability to differentially label single cells has important implications in developmental biology. For instance, determining how hematopoietic, ...

Immunostaining of Dissected Zebrafish Embryonic Heart 

Zebrafish embryo becomes a popular in vivo vertebrate model for studying cardiac development and human heart diseases due to its advantageous embryology and genetics 1,2. About 100-200 embryos are readily available every week from a single pair of adult fish. The transparent embryos that develop ex utero make them ideal for assessing cardiac defects 3. The expression of any gene can be manipulated via morpholino technology or RNA injection 4. Moreover, forward genetic screens have already generated a list of mutants that affect different perspectives of cardiogenesis 5. 
Whole mount immunostaining is an important technique in this animal model to reveal the expression pattern of the targeted protein to a particular tissue 6. However, high resolution images that can reveal cellular or subcellular structures have been difficult, mainly due to the physical location of the heart and the poor penetration of the antibodies. 
 Here, we present a method to address these bottlenecks by dissecting heart first and then conducting the staining process on the surface of a microscope slide. To prevent the loss of small heart samples and to facilitate solution handling, we restricted the heart samples within a circle on the surface of the microscope slides drawn by an immEdge pen. After the staining, the fluorescence signals can be directly observed by a compound microscope. 
Our new method significantly improves the penetration for antibodies, since a heart from an embryonic fish only consists of few cell layers. High quality images from intact hearts can be obtained within a much reduced procession time for zebrafish embryos aged from day 2 to day 6. Our method can be potentially extended to stain other organs dissected from either zebrafish or other small animals.

Immunostaining of Dissected Zebrafish Embryonic Heart

A rapid way to conduct immunostaining of zebrafish embryonic heart is described. Compared to the whole mount immunostaining approach, this method dramatically increases the penetration of the antibodies, which allows obtaining high resolution images that reveal cellular/subcellular structures in the heart within a much reduced processing time.

Zebrafish embryo becomes a popular in vivo vertebrate model for studying cardiac development and human heart diseases due to its advantageous embryology ...

An Efficient Protocol to Assess ERK Activity Modulation in Early Zebrafish Noonan Syndrome Models via Live FRET Microscopy and Immunofluorescence

RASopathies are genetic syndromes caused by ERK hyperactivation and resulting in multisystemic diseases that can also lead to cancer predisposition. Despite a broad genetic heterogeneity, germline gain-of-function mutations in key regulators of the RAS-MAPK pathway underlie the majority of the cases, and, thanks to advanced sequencing techniques, potentially pathogenic variants affecting the RAS-MAPK pathway continue to be identified. Functional validation of the pathogenicity of these variants, essential for accurate diagnosis, requires fast and reliable protocols, preferably in vivo. Given the scarcity of effective treatments in early childhood, such protocols, especially if scalable in cost-effective animal models, can be instrumental in offering a preclinical ground for drug repositioning/repurposing. 
Here we describe step-by-step the protocol for rapid generation of transient RASopathy models in zebrafish embryos and direct inspection of live disease-associated ERK activity changes occurring already during gastrulation through real-time multispectral F&#246;rster resonance energy transfer (FRET) imaging. The protocol uses a transgenic ERK reporter recently established and integrated with the hardware of commercial microscopes. We provide an example application for Noonan syndrome (NS) zebrafish models obtained by expression of the Shp2D61G. We describe a straightforward method that enables registration of ERK signal change in the NS fish model before and after pharmacological signal modulation by available low-dose MEK inhibitors. We detail how to generate, retrieve, and assess ratiometric FRET signals from multispectral acquisitions before and after treatment and how to cross-validate the results via classical immunofluorescence on whole embryos at early stages. We then describe how, via examining standard morphometric parameters, to query late changes in embryo shape, indicative of a resulting impairment of gastrulation, in the same embryos whose ERK activity is assessed by live FRET at 6 h post fertilization.

RASopathies are multisystem genetic syndromes caused by RAS-MAPK pathway hyperactivation. Potentially pathogenic variants awaiting validation emerge continuously while poor preclinical evidence limits therapy. Here, we describe our in vivo protocol to test and cross-validate RASopathy-associated ERK activation levels and its pharmacological modulation during embryogenesis by live FRET imaging in Teen-reporter zebrafish.

RASopathies are genetic syndromes caused by ERK hyperactivation and resulting in multisystemic diseases that can also lead to cancer predisposition. ...

Biochemistry

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 ...

In Situ Hybridization Combined with Immunohistochemistry in Cryosectioned Zebrafish Embryos

As a vertebrate, the zebrafish has been widely used in biological studies. Zebrafish and humans share high genetic homology, which allows its use as a model for human diseases. Gene function study is based on the detection of gene expression patterns. Although immunohistochemistry offers a powerful way to assay protein expression, the limited number of commercially available antibodies in zebrafish restricts the application of costaining. In situ hybridization is widely used in zebrafish embryos to detect mRNA expression. This protocol describes how to obtain images by combining in situ hybridization and immunohistochemistry for zebrafish embryo sections. In situ hybridization was performed prior to cryosectioning, followed by antibody staining. Immunohistochemistry and the imaging of a single cryosection were performed after in situ hybridization. The protocol is helpful to unravel the expression pattern of two genes, first by in situ transcript detection and then by immunohistochemistry against a protein in the same section.

In Situ Hybridization Combined with Immunohistochemistry in Cryosectioned Zebrafish Embryos

This protocol describes how to obtain images by combining in situ hybridization and immunohistochemistry of zebrafish embryonic sections. In situ hybridization was performed prior to cryosectioning, followed by antibody staining. It is useful to detect the expression patterns of two genes in zebrafish if there is a paucity of antibodies.

As a vertebrate, the zebrafish has been widely used in biological studies. Zebrafish and humans share high genetic homology, which allows its use as a ...

Neuroscience

Sequential Immunofluorescence and Immunohistochemistry on Cryosectioned Zebrafish Embryos

Investigation of intercellular interactions often requires discrete labeling of specific cell populations and precise protein localization. The zebrafish embryo is an excellent tool for examining such interactions with an in vivo model. Whole-mount immunohistochemical and immunofluorescence assays are frequently applied in zebrafish embryos to assess protein expression. However, it can be difficult to achieve accurate mapping of co-localized proteins in three-dimensional space. In addition, some studies may require the use of two antibodies that are not compatible with the same technique (e.g., antibody 1 is only suitable for immunohistochemistry and antibody 2 is only suitable for immunofluorescence). The purpose of the method described herein is to perform sequential immunofluorescence and/or immunohistochemistry on individual cryosections derived from early-stage zebrafish embryos. Here we describe the use of sequential rounds of immunofluorescence, imaging, immunohistochemistry, imaging for a single cryosection in order to achieve precise identification of protein expression at the single-cell level. This methodology is suitable for any study in early-stage zebrafish embryos that requires accurate identification of multiple protein targets in individual cells.

This protocol demonstrates sequential immunofluorescence and immunohistochemistry on cryosections from early-stage zebrafish embryos enabling precise colocalization analyses in specific cell populations.

Investigation of intercellular interactions often requires discrete labeling of specific cell populations and precise protein localization. The zebrafish ...

Immunostaining Phospho-epitopes in Ciliated Organs of Whole Mount Zebrafish Embryos

Summary

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Chapters in this video

High Precision Zinc Isotopic Measurements Applied to Mouse Organs

Visualizing Multiciliated Cells in the Zebrafish Through a Combined Protocol of Whole Mount Fluorescent In Situ Hybridization and Immunofluorescence

Zebrafish Whole Mount High-Resolution Double Fluorescent In Situ Hybridization

Whole Mount Immunohistochemistry in Zebrafish Embryos and Larvae

Single Cell Fate Mapping in Zebrafish

Immunostaining of Dissected Zebrafish Embryonic Heart

An Efficient Protocol to Assess ERK Activity Modulation in Early Zebrafish Noonan Syndrome Models via Live FRET Microscopy and Immunofluorescence

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

In Situ Hybridization Combined with Immunohistochemistry in Cryosectioned Zebrafish Embryos

Sequential Immunofluorescence and Immunohistochemistry on Cryosectioned Zebrafish Embryos