Name: ploidy manipulation of zebrafish embryos with heat shock 2 treatment
Uploaded: 2016-12-16T13:00:00
Description: Watch this Scientific Journal Video about Ploidy Manipulation of Zebrafish Embryos with Heat Shock 2 Treatment at JoVE.com

This work was supported by NIH grants R21 HD068949-01 and RO1 GM065303.

All animal experiments were conducted according to University of Wisconsin &#8211; Madison and Institutional Animal Care and Use Committee (IACUC) guidelines (University of Wisconsin &#8211; Madison Assurance number A3368-01).
1. Selecting Females for Egg Collection via Interrupted Mating
NOTE: IVF-based protocols rely on the extrusion of mature eggs from females through manual pressure 9. Previous protocols have used females directly from tanks or in pair matings without the females undergoing egg...

<ol>
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Biol. 20, 2040-2045 (2010).</li><li>Yabe, T., Ge, X., Pelegri, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+zebrafish+maternal-effect+gene+cellular+atoll+encodes+the+centriolar+component+Sas-6+and+defects+in+its+paternal+function+promote+whole+genome+duplication.">The zebrafish maternal-effect gene cellular atoll encodes the centriolar component Sas-6 and defects in its paternal function promote whole genome duplication.</a> Dev. Biol. 312, 44-60 (2007).</li><li>Poss, K. D., Nechiporuk, A., Stringer, K. F., Lee, C., Keating, M. 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Critical steps
It is critical to work under conditions of effective in vitro fertilization. To insure a good supply of mature eggs (step 1), females set up for mating should not have been set up in mating crosses for at least 5 days and should appear gravid. During interruption of breeding, an observer can monitor 15-30 tanks adequately for the first appearance of natural egg extrusion. Interruption of mating should occur as soon as possible when the first eggs are released through natural mating...

This protocol allows the manipulation of ploidy in zebrafish embryos, such as in the generation of homozygous gynogenetic diploids from gynogenetic haploids (Figure 1) or the production of tetraploids. This is achieved by inducing a delay in cytokinesis corresponding to precisely one cell cycle (Figure 2A, 2B). The key one-cycle delay in cytokinesis is achieved by treatment with heat shock. The standard protocol of Heat Shock (HS) as originally described by Streisinger and colleagues involved a temperature pulse during the period 13-15 mpf, resulting in a one-cycle cell division stall during the first cell cycle 1. The efficiency of this protocol has been recently improved by scanning the early cell cycles with a sliding temporal window of heat shock treatment. This scan identified a later time point for a heat shock, still within the first cell cycle (22-24 mpf), that results in a higher rate of embryos with a one-cycle cell division stall, which in this case affects the second cell cycle 2. The observation that experimental manipulations during the first cell cycle interfere with cell division during the second cell cycle and cause DNA content duplication has also been reported in other fish species 3,4. We refer to this modified protocol as Heat Shock 2 (HS2 &#8211; the term &#34;2&#34; reflects that the heat pulse occurs at a later time point than the standard HS method, and that the cell cycle delay caused by HS2 occurs during the second cell cycle). These studies showed that the basis for cytokinesis arrest after heat shock is the inhibition of centriole duplication during the heat pulse, which affects spindle formation and furrow induction in the following cell cycle. HS2 results in yields of cell cycle arrest nearing 100%, and rates of ploidy duplication up to 4 times higher than standard HS 2.
Embryos treated with a heat shock during blastomere cell cycling exhibit many deleterious effects, suggesting that heat shock affects multiple processes required for cell division 2. On the other hand, if the heat shock is applied prior to the initiation of cell cycling (time period 0-30 mpf), it appears to have effects consistent with specific interference with centriole duplication and does not seem to affect other essential cell processes 2. These studies showed that the time prior to the initiation of blastomere division appears to be a developmental period amenable to using Heat Shock as a tool to specifically manipulate ploidy through centriole inhibition. The underlying cause of the apparent selectivity for heat shock on centriole duplication is unknown, but may be related to a selective degradation of centrosome substructures observed under heat stress in certain cell types, such as leukocytes 5.
Temporal synchronization of embryonic development is achieved by in vitro fertilization (IVF). Use of untreated sperm during fertilization results in diploid embryos that upon HS2-induced one-cycle cytokinesis stall become tetraploid. Use of UV-treated sperm, which carries crosslinks that inactivate its DNA, results in gynogenetic haploid embryos 6, which upon HSII-induced one-cycle cytokinesis stall become gynogenetic diploids 2. Because of the resulting whole genome duplication, the latter gynogenetic diploids are homozygous at every single locus across the genome. For conciseness, we refer to gynogenetic haploid embryos as &#34;haploids&#34;, and homozygous gynogenetic diploid embryos as &#34;homozygous diploids&#34;. If viable and fertile, homozygous diploids can be used to initiate sterile and lethal-free lines. Direct homozygosity induced by HS2 should also be readily incorporated into genetic analysis or genetic screens, since homozygous diploids from females that are heterozygous carriers of mutations exhibit rates of homozygosity at high and fixed (50%) ratios 2.
The following protocol describes steps to perform HS2 and induce ploidy duplication with full homozygosity. For tetraploid production, sperm solution should be untreated. For homozygous diploid production, sperm should be inactivated by UV treatment. In addition, as described in the Discussion, visible pigment markers can also be used to facilitate identification of homozygous diploids. Zebrafish mate primarily during the first 3 hr of the initiation of their light cycle 7, and both adults and eggs are sensitive to circadian rhythms 8, so for best results the IVF procedure should occur within this time period.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<colgroup>
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		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Zebrafish mating boxes</td>
			<td style="width:71px;">Aqua Schwarz</td>
			<td style="width:119px;">SpawningBox1</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">NaCl</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">S5886</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">KCl</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">P5405</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Na2HPO4</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">S3264</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">KH2PO4</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">P9791</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">CaCl2</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">C7902</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">MgSO4-7H2O</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">63138</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">NaHCO3</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">S5761</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Tricaine</td>
			<td style="width:71px;">Western Chemical</td>
			<td style="width:119px;">Tricaine-D (MS 222)</td>
			<td>FDA approved (ANADA 200-226)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tris base</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">77-86-1</td>
			<td>to prepare 1 M Tris pH 9.0</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">HCl</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:119px;">920-1</td>
			<td>to prepare 1 M Tris pH 9.0</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Fish net (fine mesh) (4-5 in)</td>
			<td style="width:71px;">PennPlax</td>
			<td style="width:119px;">(ThatFishThatPlace # 212370)</td>
			<td>available in ThatFishThatPlace</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Plastic spoon</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>available in most standard stores</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Dissecting scissors</td>
			<td style="width:71px;">Fine Science Tools</td>
			<td style="width:119px;">14091-09</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Dissecting forceps</td>
			<td style="width:71px;">Dumont</td>
			<td style="width:119px;">SS</td>
			<td>available from Fine Science Tools</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Dissecting stereoscope (with transmitted light source)</td>
			<td style="width:71px;">Nikon</td>
			<td style="width:119px;">SMZ645</td>
			<td>or equivalent</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Reflective light source (LED arms)</td>
			<td style="width:71px;">Fostec</td>
			<td style="width:119px;">KL1600 LED</td>
			<td>or equivalent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Petri plates 10 cm diameter</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>any maker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Eppendorf tubes 1.5 ml</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>any maker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ice bucket</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>any maker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Pipetteman P-1000</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>any maker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Pipette tips 1000 &#181;l</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>any maker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Narrow spatula</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:119px;">14-374</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Depression glass plate</td>
			<td style="width:71px;">Corning Inc</td>
			<td style="width:119px;">722085 (Fisher cat. No 13-748B)</td>
			<td>available from Fisher Scientific</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">UV lamp</td>
			<td style="width:71px;">UVP</td>
			<td style="width:119px;">Model XX-15 (cat No. UVP18006201)</td>
			<td>available from Fisher Scientific. Although not observed by us with this model, some UV sources have been observed to experience a decrease of intensity over time (if this is the case, see Modifications and Troubleshooting)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">UV glasses</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>any maker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Paper towels</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>any maker</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Kimwipes</td>
			<td style="width:71px;">Kimberly-Clark</td>
			<td style="width:119px;">06-666-11</td>
			<td>available from Fisher Scientific</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Timer stop watch</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>any maker</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Wash bottle</td>
			<td style="width:71px;">Thermo Scientific</td>
			<td style="width:119px;">24020500</td>
			<td>available from Fisher Scientific</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tea strainer</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>available in kitchen stores</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">beakers, 250 ml (2)</td>
			<td style="width:71px;">Corning Inc.</td>
			<td style="width:119px;">1000250</td>
			<td>available from Fisher Scientific</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">water bath (2)</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>any maker, with accurary to 0.1 C (e.g. Shel Lab H2O Bath Series)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="44">
			<td height="44" style="height:44px;">Hanks&#8217; Solution 1</td>
			<td style="width:71px;">see above</td>
			<td style="width:119px;">see above</td>
			<td>8.0g NaCl, 0.4g KCl in 100ml ddH2O. Store at 4&#176;C.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hanks&#8217; Solution 2</td>
			<td style="width:71px;">see above</td>
			<td style="width:119px;">see above</td>
			<td>0.358g Anhydrous Na2HPO4, 0.6g KH2PO4 in 100ml ddH2O. Store at 4&#176;C.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hanks&#8217; Solution 4</td>
			<td style="width:71px;">see above</td>
			<td style="width:119px;">see above</td>
			<td>0.72g CaCl2 in 50ml ddH2O. Store at 4&#176;C.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hanks&#8217; Solution 5</td>
			<td style="width:71px;">see above</td>
			<td style="width:119px;">see above</td>
			<td>1.23g MgSO4 &#8729; 7H2O in 50ml ddH2O. Store at 4&#176;C.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hank&#39;s Premix</td>
			<td style="width:71px;">see above</td>
			<td style="width:119px;">see above</td>
			<td>add, in the following order: 10.0 ml Solution 1;&#160; 1.0 ml Solution 2;&#160; 1.0 ml Solution 4;&#160; 86.0 ml ddH2O;&#160; 1.0 ml Solution 5. Store at 4&#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hanks&#8217; Solution 6</td>
			<td style="width:71px;">see above</td>
			<td style="width:119px;">see above</td>
			<td>0.33g NaHCO3 in 10ml ddH2O. Prepare fresh the morning of the IVF procedure.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hank&#39;s Solution (final solution)</td>
			<td style="width:71px;">see above</td>
			<td style="width:119px;">see above</td>
			<td>Combine 990ul of Hank&#8217;s Premix and 10ul of freshly made Solution 6 (NaHCO3 solution)</td>
		</tr>
	</tbody>
</table>

ploidy manipulation of zebrafish embryos with heat shock 2 treatment

Manipulation of ploidy allows for useful transformations, such as diploids to tetraploids, or haploids to diploids. In the zebrafish Danio rerio, specifically the generation of homozygous gynogenetic diploids is useful in genetic analysis because it allows the direct production of homozygotes from a single heterozygous mother. This article describes a modified protocol for ploidy duplication based on a heat pulse during the first cell cycle, Heat Shock 2 (HS2). Through inhibition of centriole duplication, this method results in a precise cell division stall during the second cell cycle. The precise one-cycle division stall, coupled to unaffected DNA duplication, results in whole genome duplication. Protocols associated with this method include egg and sperm collection, UV treatment of sperm, in vitro fertilization and heat pulse to cause a one-cell cycle division delay and ploidy duplication. A modified version of this protocol could be applied to induce ploidy changes in other animal species.

In spite of the one-cell cycle cytokinesis stall, DNA replication occurs normally in such embryos, resulting in the duplication of the DNA content of the embryo (Figure 1). The Streisinger Heat Shock protocol (standard HS) involves a heat pulse during the period 13-15 minutes post fertilization (mpf) and induces primarily cytokinesis arrest during the first embryonic cell division at 35 mpf 1,2, whereas the derived method described here, referred to as Heat Sho...

Watch this Scientific Journal Video about Ploidy Manipulation of Zebrafish Embryos with Heat Shock 2 Treatment at JoVE.com

Ploidy Manipulation of Zebrafish Embryos with Heat Shock 2 Treatment

A modified protocol for ploidy manipulation uses a heat shock to induce a one-cycle stall in cytokinesis in the early embryo. This protocol is demonstrated in the zebrafish but may be applicable to other species.

Manipulation of ploidy allows for useful transformations, such as diploids to tetraploids, or haploids to diploids. In the zebrafish Danio rerio, ...

The overall goal of this procedure is to promote diploidization in the early zebrafish embryo through inhibition of cytokinesis corresponding to one embryonic cell cycle. This method can help answer key questions in the field of genetics such as through the identification of genes involved in adult or reproductive traits, the generation of inbred lines or other genetic manipulations. The main advantage of this technique is that it is simple yet effective in promoting diploidization, allowing the direct homozygosis of alleles present in a single heterozygous individual.The afternoon before the experiment, set up mating pairs of the desired zebrafish strain in standard zebrafish mating boxes with dividers to separate males and females. The morning of the experiment, remove the physical partition for egg laying to begin. Visually inspect tanks containing mating pairs to detect extrusion of eggs during natural mating.At the first signs of egg extrusions, separate the male and female to interrupt breeding. Keep the pre-selected females either separately or pooled in the same tank. Use multiple females depending on the number of embryos desired.To prepare a sperm solution from zebrafish testes, after confirming euthanasia according to the text protocol, remove the males from the beaker. Use conditioned water to rinse briefly and dry them lightly by briefly placing them on several locations of paper towel. Use dissecting scissors or a razor blade to decapitate the fish and make a longitudinal cut along the abdomen.Then under a dissecting microscope with a reflected light source, use dissecting forceps to remove the internal organs. Pull out each of the testes'masses and transfer them to a microcentrifuge tube with Hank solution. To release the sperm into the solution, use a narrow spatula to shear the testes or use a 1, 000 microliter tip and pipette up and down five to six times in the solution while avoiding air bubble formation.Then allow the testes debris to settle. Store the sperm solution on ice where it can keep its potency for two to three hours. If proceeding to UV sperm treatment, transfer the sperm solution to a clean microcentrifuge tube leaving the sperm debris behind.To carry out UV treatment of sperm, transfer up to one milliliter of the sperm solution to a clean dry well of a depression glass plate sitting on an ice bed. Place the ice bed with the depression plate under a UV lamp at a distance of 19 centimeters from the light source and treat the sperm solution at 115 volts for 90 seconds. With the end of an unused pipette tip, gently mix the solution every 30 seconds during UV treatment.Using a clean pipette tip on a micropipette, transfer the treated sperm solution to a new microcentrifuge tube. Store on ice no longer than two to three hours until needed for IVF. After anesthetizing female zebrafish according to the text protocol, as soon as the fish stops gill movement, use a spoon to collect the fish and use conditioned water to briefly rinse it.With the spoon moving from the anterior to the posterior of the fish to avoid damaging the gill operculum, place the fish briefly and repeatedly on several locations of a paper towel to lightly dry it. Then transfer it to a clean 10 centimeter diameter Petri dish. Use lab wipes or soft tissue to further gently dry the anal fin area to prevent any released eggs from prematurely being activated by water.Then after lightly dampening the fingers with water, place one finger of one hand on the female's back as support and with the finger on the other hand, apply slight pressure along the female's abdomen until eggs are extruded. It is crucial that the extruded eggs do not encounter any excess water to avoid them from becoming prematurely activated which would prevent them from becoming fertilized by sperm. Use a narrow spatula to move the eggs away from the female's body.Then place the female back into a tank with conditioned water for recovery. Within 90 seconds after egg extrusion, add 100 microliters of sperm solution to the extruded eggs in a Petri dish. Gently swirl the pipette tip among the eggs to mix the sperm and eggs together, being sure not to lift the tip from the surface of the Petri dish to avoid egg damage.Immediately activate the eggs by adding approximately one milliliter of embryonic or E3 medium and again gently mix the eggs and sperm by using a pipette tip to swirl. Initiate timing relative to fertilization. At one minute post fertilization in the one milliliter volume, use E3 to flood the plate.Leave the fertilized eggs undisturbed until 10 to 12 minutes post fertilization or MPF to allow egg activation including full chorion expansion. After expansion of the chorions, pour the embryos from the Petri dish into a tea strainer. Then use a wash bottle with E3 to rinse the Petri dish to collect any remaining eggs into the strainer.Place the tea strainer with the embryos inside a beaker in a pre-heated bath with E3 at 28.5 degrees Celsius. Pre-equilibrate the beaker and E3 to the water bath temperature and make sure there is enough E3 so that all embryos in the strainer are submerged. At 22 MPF, remove the tea strainer from the water bath then briefly blot it onto a paper towel to remove excess moisture and place it inside a similarly pre-heated E3 beaker in a heat bath at 41.4 degrees Celsius.The key step in the procedure is the heat shock which induces a one-cycle delay in the cell division and therefore hold genome duplication. At 24 MPF, briefly blot the strainer and transfer it back into the E3 in a 28.5 degrees Celsius water bath. Then at 29 MPF, use a wash bottle with E3 to transfer the embryos from the tea strainer to a 10 centimeter Petri plate.Between 35 to 45 MPF, under a dissecting microscope with a transmitted light source, select embryos that are undergoing symmetrical cleavage into the two-cell stage and which were therefore fertilized. Remove embryos that are not undergoing cell cleavage. Continue observing the fertilized embryos selected for normal cell division during the first cell cycle and during the second cell cycle.Sort embryos according to the following categories. Four cells or no stall in the two to two arrangement standard for a four-cell embryo, three cells or partial stall in an aberrant two smaller cells to one large cell arrangement and two cells or stalled embryos. Sort the stalled embryos into a fresh Petri plate.Allow up to 80 embryos to develop in the Petri dish. At 24 hours post fertilization or HPF, observe the embryos to determine whether they have a normal morphology characteristic of diploid or homozygous diploid embryos. In contrast to reduced axis extension, an increased body thickness characteristic of haploids.In addition, at 36 HPF, assess diploidization using genetic pigment markers and other assays such as golden or albino. Finally, remove any embryos that appear to have a haploid morphology or that have lysed or exhibit other grossly abnormal defects. The derived method demonstrated here, referred to as HS2, uses a heat shock during the period 22 to 24 MPF and induces cytokinesis arrest during the second embryonic cell division at 50 MPF.During the stall, ongoing DNA synthesis result in embryos undergoing diploidization from either haploid to diploid or diploid to tetraploid. HS2 treated embryos can exhibit a variety of blastomere arrangements including no stall where neither blastomere exhibits a delay, a partial stall where one of the two blastomeres is delayed and stalled where both blastomeres exhibit delays. The morphology of the embryos can be determined at 24 HPF with a normal morphology characteristic of diploid or homozygous diploid embryos or the shorter and wider body axis morphology characteristic of haploid embryos.If properly selected for a one-cell cycle delay, all embryos should exhibit a normal diploid morphology. Once mastered, this technique can be done in two hours if it is performed properly. Although, it will take more time to process multiple clutches.While attempting this procedure, it is important to remember to separate females in time, dissect testes accurately, avoid prematurely contact of extruded eggs with water and keep proper timing of the fertilized clutches. Following this procedure, other methods like forward genetic screens can be performed in order to answer additional questions like what genes are involved in specific biological functions. After its development, this technique paved the way for researchers in the field of genetics to explore traits relevant to juvenile, adult and intergenerational traits in the zebrafish.After watching this video, you should have a good understanding of how to use heat treatment to induce diploidization in zebrafish. Don't forget that working with UV light can be extremely hazardous and precautions such as wearing UV protective safety glasses should always be taken while performing this procedure.

ploidy-manipulation-of-zebrafish-embryos-with-heat-shock-2-treatment

Research

JoVE Journal

Developmental Biology

Mechanical Vessel Injury in Zebrafish Embryos

Zebrafish (Danio rerio) embryos have proven to be a powerful model for studying a variety of developmental and disease processes. External development and optical transparency make these embryos especially amenable to microscopy, and numerous transgenic lines that label specific cell types with fluorescent proteins are available, making the zebrafish embryo an ideal system for visualizing the interaction of vascular, hematopoietic, and other cell types during injury and repair in vivo. Forward and reverse genetics in zebrafish are well developed, and pharmacological manipulation is possible. We describe a mechanical vascular injury model using micromanipulation techniques that exploits several of these features to study responses to vascular injury including hemostasis and blood vessel repair. Using a combination of video and timelapse microscopy, we demonstrate that this method of vascular injury results in measurable and reproducible responses during hemostasis and wound repair. This method provides a system for studying vascular injury and repair in detail in a whole animal model.

This article describes a method for creating a mechanical vessel injury in zebrafish embryos. This injury model provides a platform for studying hemostasis, injury-related inflammation, and wound healing in an organism ideally suited for real-time microscopy.

Zebrafish (Danio rerio) embryos have proven to be a powerful model for studying a variety of developmental and disease processes.  External development ...

Isolation and Characterization of Single Cells from Zebrafish Embryos

The zebrafish (Danio rerio) is a powerful model organism to study vertebrate development. Though many aspects of zebrafish embryonic development have been described at the morphological level, little is known about the molecular basis of cellular changes that occur as the organism develops. With recent advancements in microfluidics and multiplexing technologies, it is now possible to characterize gene expression in single cells. This allows for investigation of heterogeneity between individual cells of specific cell populations to identify and classify cell subtypes, characterize intermediate states that occur during cell differentiation, and explore differential cellular responses to stimuli. This study describes a protocol to isolate viable, single cells from zebrafish embryos for high throughput multiplexing assays. This method may be rapidly applied to any zebrafish embryonic cell type with fluorescent markers. An extension of this method may also be used in combination with high throughput sequencing technologies to fully characterize the transcriptome of single cells. As proof of principle, the relative abundance of cardiac differentiation markers was assessed in isolated, single cells derived from nkx2.5 positive cardiac progenitors. By evaluation of gene expression at the single cell level and at a single time point, the data support a model in which cardiac progenitors coexist with differentiating progeny. The method and work flow described here is broadly applicable to the zebrafish research community, requiring only a labeled transgenic fish line and access to microfluidics technologies.

This protocol describes a method for isolating single cells from zebrafish embryos, enriching for cells of interest, capturing zebrafish cells in microfluidic based single cell multiplex systems, and assessing gene expression from single cells.

The zebrafish (Danio rerio) is a powerful model organism to study vertebrate development. Though many aspects of zebrafish embryonic development have been ...

Generation of Parabiotic Zebrafish Embryos by Surgical Fusion of Developing Blastulae

Surgical parabiosis of two animals of different genetic backgrounds creates a unique scenario to study cell-intrinsic versus cell-extrinsic roles for candidate genes of interest, migratory behaviors of cells, and secreted signals in distinct genetic settings. Because parabiotic animals share a common circulation, any blood or blood-borne factor from one animal will be exchanged with its partner and vice versa. Thus, cells and molecular factors derived from one genetic background can be studied in the context of a second genetic background. Parabiosis of adult mice has been &#160;used extensively to research aging, cancer, diabetes, obesity, and brain development. More recently, parabiosis of zebrafish embryos has been used to study the developmental biology of hematopoiesis. In contrast to mice, the transparent nature of zebrafish embryos permits the direct visualization of cells in the parabiotic context, making it a uniquely powerful method for investigating fundamental cellular and molecular mechanisms. The utility of this technique, however, is limited by a steep learning curve for generating the parabiotic zebrafish embryos. This protocol provides a step-by-step method on how to surgically fuse the blastulae of two zebrafish embryos of different genetic backgrounds to investigate the role of candidate genes of interest. In addition, the parabiotic zebrafish embryos are tolerant to heat shock, making temporal control of gene expression possible. This method does not require a sophisticated set-up and has broad applications for studying cell migration, fate specification, and differentiation in vivo during embryonic development.

This protocol provides step-by-step instruction on how to generate parabiotic zebrafish embryos of different genetic backgrounds. When combined with the unparalleled imaging capabilities of the zebrafish embryo, this method provides a uniquely powerful means to investigate cell-autonomous versus non-cell-autonomous functions for candidate genes of interest.

Surgical parabiosis of two animals of different genetic backgrounds creates a unique scenario to study cell-intrinsic versus cell-extrinsic roles for ...

Affinity Labeling Detection of Endogenous Receptors from Zebrafish Embryos

By combining the powers of Affinity Labeling and Immunoprecipitation (AFLIP), a technique for the detection of low abundance receptors in zebrafish embryos has been implemented. This technique takes advantage of the selectivity and sensitivity conferred by affinity labeling of a given receptor by its ligand with the specificity of the immunoprecipitation. We have used AFLIP to detect the type III TGF-&#946; receptor (TGFBR3), also know as betaglycan, during early zebrafish development. AFLIP was instrumental in validating the efficacy of a TGFBR3 morphant zebrafish phenotype. In the first step, embryo protein extracts are prepared and used to generate 125I-TGF-&#946;2-TGFBR3 complexes that are purified by immunoprecipitation. Later, these complexes are covalently cross-linked and revealed using SDS-PAGE separation and autoradiography detection. This technique requires the availability of a labeled ligand for, and a specific antibody against, the receptor to be detected, and shall be easily adapted to identify any growth factor or cytokine receptor that meets these requirements.

A novel technique for the detection of low abundance endogenous receptors present in zebrafish embryos is described. We have named it AFLIP because it consists of affinity labeling of the receptor by its ligand linked to immunoprecipitation.

By combining the powers of Affinity Labeling and Immunoprecipitation (AFLIP), a technique for the detection of low abundance receptors in zebrafish ...

Biosensing Motor Neuron Membrane Potential in Live Zebrafish Embryos

The protocols described here are designed to allow researchers to study cell communication without altering the integrity of the environment in which the cells are located. Specifically, they have been developed to analyze the electrical activity of excitable cells, such as spinal neurons. In such a scenario, it is crucial to preserve the integrity of the spinal cell, but it is also important to preserve the anatomy and physiological shape of the systems involved. Indeed, the comprehension of the manner in which the nervous system-and other complex systems-works must be based on a systemic approach. For this reason, the live zebrafish embryo was chosen as a model system, and the spinal neuron membrane voltage changes were evaluated without interfering with the physiological conditions of the embryos. 
Here, an approach combining the employment of zebrafish embryos with a FRET-based biosensor is described. Zebrafish embryos are characterized by a very simplified nervous system and are particularly suited for imaging applications thanks to their transparency, allowing for the employment of fluorescence-based voltage indicators at the plasma membrane during zebrafish development. The synergy between these two components makes it possible to analyze the electrical activity of the cells in intact living organisms, without perturbing the physiological state. Finally, this non-invasive approach can co-exist with other analyses (e.g., spontaneous movement recordings, as shown here).

Protocols described here allow for the study of the electrical properties of excitable cells in the most non-invasive physiological conditions by employing zebrafish embryos in an in vivo system together with a fluorescence resonance energy transfer (FRET)-based genetically encoded voltage indicator (GEVI) selectively expressed in the cell type of interest.

The protocols described here are designed to allow researchers to study cell communication without altering the integrity of the environment in which the ...

Induction of Hypoxia in Living Frog and Zebrafish Embryos

Here, we introduce a novel system for hypoxia induction, which we developed to study the effects of hypoxia in aquatic organisms such as frog and zebrafish embryos. Our system comprises a chamber featuring a simple setup that is nevertheless robust to induce and maintain a specific oxygen concentration and temperature in any experimental solution of choice. The presented system is very cost-effective but highly functional, it allows induction and sustainment of hypoxia for direct experiments in vivo and for various time periods up to 48 h.
To monitor and study the effects of hypoxia, we have employed two methods - measurement of levels of hypoxia-inducible factor 1alpha (HIF-1&#945;) in whole embryos or specific tissues and determination of retinal stem cell proliferation by 5-ethynyl-2&#8242;-deoxyuridine (EdU) incorporation into the DNA. HIF-1&#945; levels can serve as a general hypoxia marker in the whole embryo or tissue of choice, here embryonic retina. EdU incorporation into the proliferating cells of embryonic retina is a specific output of hypoxia induction. Thus, we have shown that hypoxic embryonic retinal progenitors decrease proliferation within 1 h of incubation under 5% oxygen of both frog and zebrafish embryos.
Once mastered, our setup can be employed for use with small aquatic model organisms, for direct in vivo experiments, any given time period and under normal, hypoxic or hyperoxic oxygen concentration or under any other given gas mixture.

We introduce a novel hypoxic chamber system for use with aquatic organisms such as frog and zebrafish embryos. Our system is simple, robust, cost-effective and allows the induction and sustainment of hypoxia in vivo and for up to 48 h. We present 2 reproducible methods to monitor the effectiveness of hypoxia.

Here, we introduce a novel system for hypoxia induction, which we developed to study the effects of hypoxia in aquatic organisms such as frog and ...

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

Studying the cell biological processes during converting the identities of specific cell types provides important insights into mechanism that maintain and protect cellular identities. The conversion of germ cells into specific neurons in the nematode Caenorhabditis elegans (C. elegans) is a powerful tool for performing genetic screens in order to dissect regulatory pathways that safeguard established cell identities. Reprogramming of germ cells to a specific type of neurons termed ASE requires transgenic animals that allow broad over-expression of the Zn-finger transcription factor (TF) CHE-1. Endogenous CHE-1 is expressed exclusively in two head neurons and is required to specify the glutamatergic ASE neurons fate, which can easily be visualized by the gcy-5prom::gfp reporter. A trans gene containing the heat-shock promoter-driven che-1 gene expression construct allows broad mis-expression of CHE-1 in the entire animal upon heat-shock treatment. The combination of RNAi against the chromatin-regulating factor LIN-53 and heat-shock-induced che-1 over-expression leads to reprogramming of germ cell into ASE neuron-like cells. We describe here the specific RNAi procedure and appropriate conditions for heat-shock treatment of transgenic animals in order to successfully induce germ cell to neuron conversion.

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

This protocol describes how to study cellular processes during cell fate conversion in Caenorhabditis elegans in vivo. Using transgenic animals, allowing heat-shock promoter-driven overexpression of the neuron fate-inducing transcription factor CHE-1 and RNAi-mediated depletion of the chromatin-regulating factor LIN-53 germ cell to neuron reprogramming can be observed in vivo.

Studying the cell biological processes during converting the identities of specific cell types provides important insights into mechanism that maintain ...

Visualization of Cellular Electrical Activity in Zebrafish Early Embryos and Tumors

Bioelectricity, endogenous electrical signaling mediated by ion channels and pumps located on the cell membrane, plays important roles in signaling processes of excitable neuronal and muscular cells and many other biological processes, such as embryonic developmental patterning. However, there is a need for in vivo electrical activity monitoring in vertebrate embryogenesis. The advances of genetically encoded fluorescent voltage indicators (GEVIs) have made it possible to provide a solution for this challenge. Here, we describe how to create a transgenic voltage indicator zebrafish using the established voltage indicator, ASAP1 (Accelerated Sensor of Action Potentials 1), as an example. The Tol2 kit and a ubiquitous zebrafish promoter, ubi, were chosen in this study. We also explain&#160;the processes of Gateway site-specific cloning, Tol2 transposon-based zebrafish transgenesis, and the imaging process for early-stage fish embryos and fish tumors using regular epifluorescent microscopes. Using this fish line, we found that there are cellular electric voltage changes during zebrafish embryogenesis, and fish larval movement. Furthermore, it was observed that in a few zebrafish malignant peripheral nerve sheath tumors, the tumor cells were generally polarized compared to the surrounding normal tissues.

Here, we show the process of creating a cellular electric voltage reporter zebrafish line to visualize embryonic development, movement, and fish tumor cells in vivo.

Bioelectricity, endogenous electrical signaling mediated by ion channels and pumps located on the cell membrane, plays important roles in signaling ...

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. ...

Imaging Intranuclear Actin Rods in Live Heat Stressed Drosophila Embryos

The purpose of this protocol is to visualize intranuclear actin rods that assemble in live Drosophila melanogaster embryos following heat stress. Actin rods are a hallmark of a conserved, inducible Actin Stress Response (ASR) that accompanies human pathologies, including neurodegenerative disease. Previously, we showed that the ASR contributes to morphogenesis failures and reduced viability of developing embryos. This protocol allows the continued study of mechanisms underlying actin rod assembly and the ASR in a model system that is highly amenable to imaging, genetics and biochemistry. Embryos are collected and mounted on a coverslip to prepare them for injection. Rhodamine-conjugated globular actin (G-actinRed) is diluted and loaded into a microneedle. A single injection is made into the center of each embryo. After injection, embryos are incubated at elevated temperature and intranuclear actin rods are then visualized by confocal microscopy. Fluorescence recovery after photobleaching (FRAP) experiments may be performed on the actin rods; and other actin-rich structures in the cytoplasm can also be imaged. We find that G-actinRed polymerizes like endogenous G-actin and does not, on its own, interfere with normal embryo development. One limitation of this protocol is that care must be taken during injection to avoid serious injury to the embryo. However, with practice, injecting G-actinRed into Drosophila embryos is a fast and reliable way to visualize actin rods and can easily be used with flies of any genotype or with the introduction of other cellular stresses, including hypoxia and oxidative stress.

Imaging Intranuclear Actin Rods in Live Heat Stressed Drosophila Embryos

The goal of this protocol is to inject Rhodamine-conjugated globular actin into Drosophila embryos and image intranuclear actin rod assembly following heat stress.

The purpose of this protocol is to visualize intranuclear actin rods that assemble in live Drosophila melanogaster embryos following heat stress. Actin ...