We thank anonymous reviewers for comments on the earlier version of the manuscript, which improved the manuscript. This work was supported by funds from the University of Arkansas.

1. Induction of spawning, in vitro fertilization, and de-jellying
<ol>
	<li>Maintain Nematostella vectensis in seawater with a salinity of 12 parts per thousand (ppt) in darkness at 16 &#176;C, feeding Artemia daily.</li>
	<li>On the day before spawning induction, place animals in a temperature- and light-controlled incubator. Program the incubator so that the animals are exposed to 8 h of light at 25 &#176;C. Optional: Feed a small piece (&#60;1 mm3) of oyster to individual animals before placing them into the incubator to enhance spawning.</li>
	<li>Leave the animals in the incubator for 1 h at 16 &#176;C.</li>
	<li>Remove the animals from the incubator and leave them on a benchtop with light at room temperature (RT) to allow spawning. Spawning usually occurs within the next 1.5&#8211;2 h.</li>
	<li>If males and females are in separate containers, place egg packages from the female container into a sperm-containing male container by using a transfer pipette whose tip is cut to enlarge the opening so that the eggs are not damaged by mechanical stress during transfer. Allow eggs to be fertilized by leaving them in the male container for at least 15 min.</li>
	<li>De-jelly the egg packages in seawater containing 3% cysteine (pH 7.4) on a Petri dish or in a 15 mL tube. Gently agitate on a shaker for 12 min.</li>
	<li>Use a plastic pipette to break up clumps and continue to agitate for another 2-3 min until completely de-jellied.</li>
	<li>Remove cysteine by replacing the media with fresh seawater for at least 5x.</li>
	<li>Keep the fertilized eggs on a glass Petri dish at 16 &#176;C or RT.</li>
</ol>
2. Surgical removal of an aboral tissue from a gastrula embryo
<ol>
	<li>Prepare a DNA extraction buffer consisting of 10 mM Tris-HCl (pH 8), 50 mM KCl, 1 mM EDTA, 0.3% Tween20, 0.3% NP40, and 1 &#956;g/&#956;L proteinase K. Use 20 &#956;L of the extraction buffer per embryo. Mix well by vortexing and aliquot the buffer into PCR tubes.</li>
	<li>Dissolve 1% agarose in seawater and pour it into a Petri dish to cover the bottom. Cool on a benchtop to make a gel bed. Pour fresh seawater to cover the gel bed in the Petri dish.</li>
	<li>Transfer 24 h post-fertilization (hpf) embryos (early- to mid-gastrula stage) into the Petri dish containing an agarose gel bed.</li>
	<li>Insert a tungsten needle into a needle holder and sterilize by dipping the needle tip in alcohol (70% or higher) and placing it in flame to burn off the alcohol.</li>
	<li>Under a dissecting microscope (at 20x to 40x magnification), use the tungsten needle to make a depression on the agarose bed by removing a piece of surface agarose about the size of an embryo to be manipulated, and place the embryo onto the depression with its lateral side facing down in order to restrict the movement of the embryo for microsurgery.</li>
	<li>Use the tungsten needle to surgically excise a piece of aboral tissue located opposite to the oral blastoporal opening. An aboral one-third to one-quarter of the embryonic tissue along the oral-aboral axis is usually sufficient.</li>
	<li>Use a P20 pipette to transfer the isolated aboral tissue (in &#60;2 &#956;L) to a PCR tube containing 20 &#956;L of DNA extraction buffer.</li>
	<li>Transfer the post-surgery embryo into a well containing at least 500 &#956;L of fresh seawater in a 24- or 96-well plate.</li>
	<li>Repeat steps 2.4&#8211;2.8 for the number of embryos as needed.</li>
	<li>Place the well plate containing post-surgery embryos in an incubator at 16 &#176;C or RT until genotyping is completed.</li>
</ol>
3. Genomic DNA extraction and genotyping PCR
<ol>
	<li>Briefly spin down the PCR tubes containing the DNA extraction buffer and isolated embryonic tissues using a mini-centrifuge (e.g. at 2,680 x g for 10 s).</li>
	<li>To extract genomic DNA from single embryos, incubate the PCR tubes at 55 &#176;C for 3 h. Vortex for 30 s every 30 min to ensure breakup of cell clumps and enhance cell lysis.</li>
	<li>Incubate the PCR tubes at 95 &#176;C for 5 min to inactivate proteinase K.</li>
	<li>Keep gDNA extracts at 4 &#176;C or on ice, and immediately proceed to PCR. 
	NOTE: The protocol can be paused here by placing gDNA extracts in a -20 &#176;C freezer.</li>
	<li>Set up a PCR reaction using extracted gDNA as a template to amplify the genomic locus of interest.
	<ol>
		<li>If different alleles at the locus of interest differ in size so that the size difference can be detected by agarose gel electrophoresis, design a single set of primers to amplify the entire locus.</li>
		<li>Alternatively, use allele-specific primers that generate PCR products only in the presence of the specific allele; for instance, by designing the primer that binds to a region containing insertion/deletion mutations.</li>
		<li>Use a typical 20 &#956;L PCR reaction mix as follows: 5 &#956;L of gDNA extracts, 8 &#956;L of nuclease-free water, 4 &#956;L of PCR buffer, 0.2 &#956;L of 10mM dNTPs, 0.6 &#956;L of DMSO, 1 &#956;L of 10 &#956;M forward primer, 1 &#956;L of 10 &#956;M reverse primer, and 0.2 &#956;L of DNA polymerase (see Table of Materials). 
		NOTE: Multiple primers can be used in a PCR reaction. For instance, one universal forward primer and two allele-specific reverse primers can be combined, as long as the two reverse primers are designed to generate PCR products of distinct sizes so that the presence/absence of the two alleles can be unambiguously determined by gel electrophoresis (see representative results section).</li>
	</ol>
	</li>
	<li>Run agarose gel electrophoresis to determine the size and presence/absence of PCR products. Adjust the condition of agarose gel electrophoresis (e.g., agarose gel percentage, V/cm, and duration) depending on the expected size of PCR products.</li>
	<li>Use the results from PCR regarding the size and presence/absence of PCR products to assign a genotype to each post-surgery embryo. For instance, if different alleles are expected to generate PCR products of different sizes, use the size information to assign the genotype for each embryo. If allele-specific primers are used, the data on the presence/absence of PCR products should be used to assign a genotype to each embryo.</li>
	<li>Sort embryos according to genotype.</li>
</ol>

<ol>
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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TALEN+and+CRISPR/Cas9-mediated+genome+editing+in+the+early-branching+metazoan+Nematostella+vectensis.">TALEN and CRISPR/Cas9-mediated genome editing in the early-branching metazoan Nematostella vectensis.</a> Nature Communications. 5, 5486 (2014).</li><li>Servetnick, M. D., 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=Cas9-mediated+excision+of+Nematostella+brachyury+disrupts+endoderm+development,+pharynx+formation+and+oral-aboral+patterning.">Cas9-mediated excision of Nematostella brachyury disrupts endoderm development, pharynx formation and oral-aboral patterning.</a> Development. 144 (16), 2951-2960 (2017).</li><li>Kraus, Y., Aman, A., Technau, U., Genikhovich, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pre-bilaterian+origin+of+the+blastoporal+axial+organizer.">Pre-bilaterian origin of the blastoporal axial organizer.</a> Nature Communications. 7, 11694 (2016).</li><li>Fritzenwanker, J. H., Genikhovich, G., Kraus, Y., Technau, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+development+and+axis+specification+in+the+sea+anemone+Nematostella+vectensis.">Early development and axis specification in the sea anemone Nematostella vectensis.</a> Developmental Biology. 310 (2), 264-279 (2007).</li><li>Lee, P. N., Kumburegama, S., Marlow, H. Q., Martindale, M. Q., Wikramanayake, A. 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V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CRISPR/Cas9-mediated+genome+editing+in+a+reef-building+coral.">CRISPR/Cas9-mediated genome editing in a reef-building coral.</a> Proceedings of the National Academy of Sciences of the United States of America. 115 (20), 5235-5240 (2018).</li><li>Momose, 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=High+doses+of+CRISPR/Cas9+ribonucleoprotein+efficiently+induce+gene+knockout+with+low+mosaicism+in+the+hydrozoan+Clytia+hemisphaerica+through+microhomology-mediated+deletion.">High doses of CRISPR/Cas9 ribonucleoprotein efficiently induce gene knockout with low mosaicism in the hydrozoan Clytia hemisphaerica through microhomology-mediated deletion.</a> Scientific Reports. 8, 11734 (2018).</li><li>Artigas, G. 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The author has nothing to disclose.

Described here a PCR-based protocol to genotype a single sea anemone embryo without sacrificing the animal. Following spawning and de-jellying, the fertilized eggs are allowed to develop into gastrulae. The aboral region of each gastrula embryo is surgically removed, and the isolated aboral tissue is used for subsequent genomic DNA extraction, while the remaining post-surgery embryos heal and continue development. The gDNA extracts are then used for a PCR assay to determine the genotype of each embryo. This method takes ...

Cnidarians represent a diverse group of animals that include jellyfish, corals, and sea anemones. They are diploblasts, composed of ectoderm and endoderm that are separated by an extracellular matrix (mesoglea). Cnidaria is a sister group to speciose Bilateria, to which traditional animal models such as Drosophila and Mus belong1. Additionally, the Cnidaria-Bilateria divergence is thought to have occurred in the pre-Cambrian period2. As such, comparative studies of cnidarians and bilaterians are essential for gaining insights into the biology of their most recent common ancestor. Recently, comparative genomics has revealed that cnidarians and bilaterians share many developmental toolkit genes such as notch and bHLH, implying that their common ancestor already had these genes3. However, the role of these developmental toolkit genes in the last common ancestor of Cnidaria and Bilateria is comparably less well understood. To address this problem, it is critical to study how these deeply conserved genes function in cnidarians.
One of the emerging cnidarian genetic models is the anthozoan Nematostella vectensis. Its genome has been sequenced3, and a variety of genetic tools, including morpholino-mediated gene knockdown, meganuclease-mediated transgenesis, and CRISPR-Cas9-mediated gene knockins and knockouts, are now available for use in this animal. In addition, Nematostella development is relatively well understood. During embryogenesis, gastrulation occurs by invagination4, and the embryo develops into a free-swimming planula larva. The planula subsequently transforms into a sessile polyp with a mouth and circumoral tentacles. The polyp then grows and reaches sexual maturity.
CRISPR-Cas9-mediated targeted mutagenesis is now routinely used to study gene function in Nematostella vectensis5,6,7,8,9. To generate knockout mutants in Nematostella, a cocktail containing locus-specific single-guide RNAs and the endonuclease Cas9 protein is first injected into unfertilized or fertilized eggs to produce F0 founder animals that typically show mosaicism. F0 animals are subsequently raised to sexual maturity and crossed with each other to produce an F1 population, a subset of which may be knockout mutants6. Alternatively, sexually mature F0 animals can be crossed with wild-type animals to generate F1 heterozygous animals, and F1 heterozygotes that carry a knockout allele in the locus of interest can then be crossed with each other to produce F2 offspring, one-quarter of which are expected to be knockout mutants5. Both approaches require a method to identify knockout mutants from a genetically heterogeneous population. Polyp tentacles can be used to extract genomic DNA for genotyping6,7. However, in cases where the developmental function of the gene of interest is being investigated and mutant embryos do not reach the polyp stage (i.e., due to larval lethality associated with the mutation), knockout mutants need to be identified early in ontogeny. Described here is a PCR-based protocol to genotype individual animals at the gastrula stage without sacrificing the animal, which enables identification of knockout mutants from a genetically heterogeneous population of embryos. The duration of the entire genotyping process depends on the number of embryos to be screened, but it minimally requires 4-5 h.

<table>
	<tbody>
		<tr>
			<td>Drosophila Peltier Refrigerated Incubator</td>
			<td>Shellab</td>
			<td>SRI6PF</td>
			<td>Used for spawning induction</td>
		</tr>
		<tr>
			<td>Instant ocean sea salt</td>
			<td>Instant ocean</td>
			<td>138510</td>
			<td></td>
		</tr>
		<tr>
			<td>Brine shrimp cysts</td>
			<td>Aquatic Eco-Systems, Inc.</td>
			<td>BS90</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Cysteine Hydrochloride</td>
			<td>Sigma Aldrich</td>
			<td>C7352</td>
			<td></td>
		</tr>
		<tr>
			<td>Standard Orbital Shaker, Model 3500</td>
			<td>VWR</td>
			<td>89032-092</td>
			<td></td>
		</tr>
		<tr>
			<td>TRIS-HCl, 1M, pH8.0</td>
			<td>QUALITY BIOLOGICAL</td>
			<td>351-007-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium chloride</td>
			<td>VWR</td>
			<td>BDH9258</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA, 0.5M pH8</td>
			<td>VWR</td>
			<td>BDH7830-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween 20</td>
			<td>Sigma Aldrich</td>
			<td>P9416</td>
			<td></td>
		</tr>
		<tr>
			<td>Nonidet-P40 Substitute</td>
			<td>US Biological</td>
			<td>N3500</td>
			<td></td>
		</tr>
		<tr>
			<td>Proteinase K solution (20 mg/mL), RNA grade</td>
			<td>ThermoFisher</td>
			<td>25530049</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>VWR</td>
			<td>710</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro Dissecting needle holder</td>
			<td>Roboz</td>
			<td>RS-6060</td>
			<td></td>
		</tr>
		<tr>
			<td>Tungsten dissecting needle</td>
			<td>Roboz</td>
			<td>RS-6063</td>
			<td></td>
		</tr>
		<tr>
			<td>PCR Eppendorf Mastercycler Thermal Cyclers</td>
			<td>Eppendorf</td>
			<td>E6336000024</td>
			<td></td>
		</tr>
		<tr>
			<td>Phusion High-Fidelity DNA polymerase</td>
			<td>New England BioLabs</td>
			<td>M0530L</td>
			<td></td>
		</tr>
		<tr>
			<td>dNTP mix</td>
			<td>New England BioLabs</td>
			<td>N0447L</td>
			<td></td>
		</tr>
		<tr>
			<td>GLWamide universal forward primer</td>
			<td></td>
			<td></td>
			<td>5&#8217;- CATGCGGAGACCAAGCGCAAGGC-3&#8217;</td>
		</tr>
		<tr>
			<td>Reverse primer specific to glw-a</td>
			<td></td>
			<td></td>
			<td>5&#8217;-CCAGATGCCTGGTGATAC-3&#8217;</td>
		</tr>
		<tr>
			<td>Reverse primer specific to glw-c </td>
			<td></td>
			<td></td>
			<td>5&#8217;- CGGCCGGCGCATATATAG-3&#8217;</td>
		</tr>
	</tbody>
</table>

genotyping of sea anemone during early development

Described here is a PCR-based protocol to genotype the gastrula stage embryo of the anthozoan cnidarian Nematostella vectensis without sacrificing the life of the animal. Following in vitro fertilization and de-jellying, zygotes are allowed to develop for 24 h at room temperature to reach the early- to mid-gastrula stage. The gastrula embryos are then placed on an agarose gel bed in a Petri dish containing seawater. Under the dissecting microscope, a tungsten needle is used to surgically separate an aboral tissue fragment from each embryo. Post-surgery embryos are then allowed to heal and continue development. Genomic DNA is extracted from the isolated tissue fragment and used as a template for locus-specific PCR. The genotype can be determined based on the size of PCR products or presence/absence of allele-specific PCR products. Post-surgery embryos are then sorted according to the genotype. The duration of the entire genotyping process depends on the number of embryos to be screened, but it minimally requires 4&#8211;5 h. This method can be used to identify knockout mutants from a genetically heterogeneous population of embryos and enables analyses of phenotypes during development.

The Nematostella genome has a single locus that encodes a precursor protein for the neuropeptide GLWamide. Three knockout mutant alleles at this locus (glw-a, glw-b, and glw-c) have been previously reported5. Four heterozygous males carrying a wild-type allele (+) and knockout allele glw-c at the GLWamide locus (genotype: +/glw-c) were crossed with a heterozygous fem...

Watch this Scientific Journal Video about Genotyping of Sea Anemone during Early Development at JoVE.com

Genotyping of Sea Anemone during Early Development

The goal of this protocol is to genotype the sea anemone Nematostella vectensis during gastrulation without sacrificing the embryo.

Described here is a PCR-based protocol to genotype the gastrula stage embryo of the anthozoan cnidarian Nematostella vectensis without sacrificing the ...

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Developmental Biology

5.5K Views.  University of Arkansas. The goal of this protocol is to genotype the sea anemone Nematostella vectensis during gastrulation without sacrificing the embryo.

Video: Genotyping of Sea Anemone during Early Development

Protocols for Obtaining Zygotic and Somatic Embryos for Studying the Regulation of Early Embryo Development in the Model Legume Medicago truncatula

Early embryogenesis starting from a single cell zygote goes through rapid cell division and morphogenesis, and is morphologically characterized by pre-globular, globular, heart, torpedo and cotyledon stages. This progressive development is under the tight regulation of a complex molecular network. Harvesting sufficient early embryos at a similar stage of development is essential for investigating the cellular and molecular regulation of early embryogenesis. This is not straightforward since early embryogenesis undergoes rapid morphogenesis in a short while e.g. 8 days for Medicago truncatula to reach the early cotyledon stage. Here, we address the issue by two approaches. The first one establishes a linkage between embryo development and pod morphology in helping indicate the stage of the zygotic embryo. This is particularly based on the number of pod spirals and development of the spines. An alternative way to complement the in vivo studies is via culturing leaf explants to produce somatic embryos. The medium includes an unusual hormone combination - an auxin (1-naphthaleneacetic acid), a cytokinin (6-benzylaminopurine), abscisic acid and gibberellic acid. The different stages can be discerned growing out of the callus without dissection.

Protocols for Obtaining Zygotic and Somatic Embryos for Studying the Regulation of Early Embryo Development in the Model Legume Medicago truncatula

The goal is to illustrate that the model legume Medicago truncatula can be readily utilized to investigate the regulation of early plant embryogenesis to complement the non-legume Arabidopsis model. Pod morphology is linked to zygotic embryogenesis stages and a protocol to collect embryos using tissue culture is also provided.

Early embryogenesis starting from a single cell zygote goes through rapid cell division and morphogenesis, and is morphologically characterized by ...

Transcriptome Profiling of In-Vivo Produced Bovine Pre-implantation Embryos Using Two-color Microarray Platform

Early embryonic loss is a large contributor to infertility in cattle. Moreover, bovine becomes an interesting model to study human preimplantation embryo development due to their similar developmental process. Although genetic factors are known to affect early embryonic development, the discovery of such factors has been a serious challenge. Microarray technology allows quantitative measurement and gene expression profiling of transcript levels on a genome-wide basis. One of the main decisions that have to be made when planning a microarray experiment is whether to use a one- or two-color approach. Two-color design increases technical replication, minimizes variability, improves sensitivity and accuracy as well as allows having loop designs, defining the common reference samples. Although microarray is a powerful biological tool, there are potential pitfalls that can attenuate its power. Hence, in this technical paper we demonstrate an optimized protocol for RNA extraction, amplification, labeling, hybridization of the labeled amplified RNA to the array, array scanning and data analysis using the two-color analysis strategy.

Transcriptome Profiling of In-Vivo Produced Bovine Pre-implantation Embryos Using Two-color Microarray Platform

Microarray technology allows quantitative measurement and gene expression profiling of transcripts on a genome-wide basis. Therefore, this protocol provides an optimized technical procedure in a two-color custom made bovine array using Day 7 bovine embryos to demonstrate the feasibility of using low amount of total RNA.

Early embryonic loss is a large contributor to infertility in cattle. Moreover, bovine becomes an interesting model to study human preimplantation embryo ...

Studying Wnt Signaling During Patterning of Conducting Airways

Wnt signaling pathways play critical roles during development of the respiratory tract. Defining precise mechanisms of differentiation and morphogenesis controlled by Wnt signaling is required to understand how tissues are patterned during normal development. This knowledge is also critical to determine the etiology of birth defects such as lung hypoplasia and tracheobronchomalacia. Analysis of earliest stages of development of respiratory tract imposes challenges, as the limited amount of tissue prevents the performance of standard protocols better suited for postnatal studies. In this paper, we discuss methodologies to study cell differentiation and proliferation in the respiratory tract. We describe techniques such as whole mount staining, processing of the tissue for confocal microscopy and immunofluorescence in paraffin sections applied to developing tracheal lung. We also discuss methodologies for the study of tracheal mesenchyme differentiation, in particular cartilage formation. Approaches and techniques discussed in the current paper circumvent the limitation of material while working with embryonic tissue, allowing for a better understanding of the patterning process of developing conducting airways.

The use of reporter mice coupled to whole mount and section staining, microscopy and in vivo assays facilitates the analysis of mechanisms underlying the normal patterning of the respiratory tract. Here we describe how these techniques contributed to the analysis of Wnt signaling during tracheal development.

Wnt signaling pathways play critical roles during development of the respiratory tract. Defining precise mechanisms of differentiation and morphogenesis ...

Inducing Complete Polyp Regeneration from the Aboral Physa of the Starlet Sea Anemone Nematostella vectensis

Cnidarians, and specifically Hydra, were the first animals shown to regenerate damaged or severed structures, and indeed such studies arguably launched modern biological inquiry through the work of Trembley more than 250 years ago. Presently the study of regeneration has seen a resurgence using both &#34;classic&#34; regenerative organisms, such as the Hydra, planaria and Urodeles, as well as a widening spectrum of species spanning the range of metazoa, from sponges through mammals. Besides its intrinsic interest as a biological phenomenon, understanding how regeneration works in a variety of species will inform us about whether regenerative processes share common features and/or species or context-specific cellular and molecular mechanisms. The starlet sea anemone, Nematostella vectensis, is an emerging model organism for regeneration. Like Hydra, Nematostella is a member of the ancient phylum, cnidaria, but within the class anthozoa, a sister clade to the hydrozoa that is evolutionarily more basal. Thus aspects of regeneration in Nematostella will be interesting to compare and contrast with those of Hydra and other cnidarians. In this article, we present a method to bisect, observe and classify regeneration of the aboral end of the Nematostella adult, which is called the physa. The physa naturally undergoes fission as a means of asexual reproduction, and either natural fission or manual amputation of the physa triggers re-growth and reformation of complex morphologies. Here we have codified these simple morphological changes in a Nematostella Regeneration Staging System (the NRSS). We use the NRSS to test the effects of chloroquine, an inhibitor of lysosomal function that blocks autophagy. The results show that the regeneration of polyp structures, particularly the mesenteries, is abnormal when autophagy is inhibited.

Inducing Complete Polyp Regeneration from the Aboral Physa of the Starlet Sea Anemone Nematostella vectensis

Here we demonstrate how to induce and monitor regeneration in the Starlet Sea Anemone Nematostella vectensis, a model cnidarian anthozoan. We demonstrate how to amputate and categorize regeneration using a morphological staging system, and we use this system to reveal a requirement for autophagy in regenerating polyp structures.

Cnidarians, and specifically Hydra, were the first animals shown to regenerate damaged or severed structures, and indeed such studies arguably launched ...

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 ...

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development

Kinase activity is crucial for a plethora of cellular functions, including cell proliferation, differentiation, migration, and apoptosis. During early embryonic development, kinase activity is highly dynamic and widespread across the embryo. Pharmacological and genetic approaches are commonly used to probe kinase activities. Unfortunately, it is challenging to achieve superior spatial and temporal resolution using these strategies. Furthermore, it is not feasible to control the kinase activity in a reversible fashion in live cells and multicellular organisms. Such a limitation remains a bottleneck for achieving a quantitative understanding of kinase activity during development and differentiation. This work presents an optogenetic strategy that takes advantage of a bicistronic system containing photoactivatable proteins Arabidopsis thaliana cryptochrome 2 (CRY2) and the N-terminal domain of cryptochrome-interacting basic-helix-loop-helix (CIBN). Reversible activation of the mitogen-activated protein kinase (MAPK) signaling pathway is achieved through light-mediated protein translocation in live cells. This approach can be applied to mammalian cell cultures and live vertebrate embryos. This bicistronic system can be generalized to control the activity of other kinases with similar activation mechanisms and can be applied to other model systems.

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development

This protocol describes an optogenetic strategy to modulate mitogen-activated protein kinase (MAPK) activity during cell differentiation and Xenopus embryonic development. This method allows for the reversible activation of the MAPK signaling pathway in mammalian cell culture and in multicellular live organisms, like Xenopus embryos, with high spatial and temporal resolution.

Kinase activity is crucial for a plethora of cellular functions, including cell proliferation, differentiation, migration, and apoptosis. During early ...

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 ...

Analysis of Cardiac Chamber Development During Mouse Embryogenesis Using Whole Mount Epifluorescence

The goal of this protocol is to describe a method for the dissection of mouse embryos and visualization of embryonic mouse ventricular chambers during heart development using ventricular specific fluorescent reporter knock-in mice (MLC-2v-tdTomato mice). Heart development involves a linear heart tube formation, the heart tube looping, and four chamber septation. These complex processes are highly conserved in all vertebrates. The mouse embryonic heart has been widely used for heart developmental studies. However, due to their extremely small size, dissecting mouse embryonic hearts is technically challenging. In addition, visualization of cardiac chamber formation often needs in situ hybridization, beta-galactosidase staining using LacZ reporter mice, or immunostaining of sectioned embryonic hearts. Here, we describe how to dissect mouse embryonic hearts and directly visualize ventricular chamber formation of MLC-2v-tdTomato mice using whole mount epifluorescent microscopy. With this method, it is possible to directly examine heart tube formation and looping, and four chamber formation without further experimental manipulation of mouse embryos. Although the MLC-2v-tdTomato reporter knock-in mouse line is used in this protocol as an example, this protocol can be applied to other heart-specific fluorescent reporter transgenic mouse lines.

We present the protocols to examine mouse heart development using whole mount epifluorescent microscopy on mouse embryos dissected from ventricular specific MLC-2v-tdTomato reporter knock-in mice. This method allows us to directly visualize each stage of the ventricular formation during mouse heart development without labor-intensive histochemical methods.

The goal of this protocol is to describe a method for the dissection of mouse embryos and visualization of embryonic mouse ventricular chambers during ...

Genotyping and Quantification of In Situ Hybridization Staining in Zebrafish

In situ hybridization (ISH) is an important technique that enables researchers to study mRNA distribution in situ and has been a critical technique in developmental biology for decades. Traditionally, most gene expression studies relied on visual evaluation of the ISH signal, a method that is prone to bias, particularly in cases where sample identities are known a priori. We have previously reported on a method to circumvent this bias and provide a more accurate quantification of ISH signals. Here, we present a simple guide to apply this method to quantify the expression levels of genes of interest in ISH-stained embryos and correlate that with their corresponding genotypes. The method is particularly useful to quantify spatially restricted gene expression signals in samples of mixed genotypes and it provides an unbiased and accurate alternative to the traditional visual scoring methods.

Gene editing technologies have enabled researchers to generate zebrafish mutants to investigate gene function with relative ease. Here, we provide a guide to perform parallel embryo genotyping and quantification of in situ hybridization signals in zebrafish. This unbiased approach provides greater accuracy in phenotypical analyses based on in situ hybridization.

In situ hybridization (ISH) is an important technique that enables researchers to study mRNA distribution in situ and has been a critical technique in ...

Preparation of Small RNA Libraries for Sequencing from Early Mouse Embryos

MicroRNAs (miRNAs) are important for the complex regulation of cell fate decisions and developmental timing. In vivo studies of the contribution of miRNAs during early development are technically challenging due to the limiting cell number. Moreover, many approaches require a miRNA of interest to be defined in assays such as northern blotting, microarray, and qPCR. Therefore, the expression of many miRNAs and their isoforms have not been studied during early development. Here, we demonstrate a protocol for small RNA sequencing of sorted cells from early mouse embryos to enable relatively unbiased profiling of miRNAs in early populations of neural crest cells. We overcome the challenges of low cell input and size selection during library preparation using amplification and gel-based purification. We identify embryonic age as a variable accounting for variation between replicates and stage-matched mouse embryos must be used to accurately profile miRNAs in biological replicates. Our results suggest that this method can be broadly applied to profile the expression of miRNAs from other lineages of cells. In summary, this protocol can be used to study how miRNAs regulate developmental programs in different cell lineages of the early mouse embryo.

We describe a technique for profiling microRNAs in early mouse embryos. This protocol overcomes the challenge of low cell input and small RNA enrichment. This assay can be used to analyze changes in miRNA expression over time in different cell lineages of the early mouse embryo.

MicroRNAs (miRNAs) are important for the complex regulation of cell fate decisions and developmental timing. In vivo studies of the contribution of miRNAs ...

Genotyping of Sea Anemone during Early Development

Summary

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Chapters in this video

Protocols for Obtaining Zygotic and Somatic Embryos for Studying the Regulation of Early Embryo Development in the Model Legume Medicago truncatula

Transcriptome Profiling of In-Vivo Produced Bovine Pre-implantation Embryos Using Two-color Microarray Platform

Studying Wnt Signaling During Patterning of Conducting Airways

Inducing Complete Polyp Regeneration from the Aboral Physa of the Starlet Sea Anemone Nematostella vectensis

Induction of Hypoxia in Living Frog and Zebrafish Embryos

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development

Visualization of Cellular Electrical Activity in Zebrafish Early Embryos and Tumors

Analysis of Cardiac Chamber Development During Mouse Embryogenesis Using Whole Mount Epifluorescence

Genotyping and Quantification of In Situ Hybridization Staining in Zebrafish

Preparation of Small RNA Libraries for Sequencing from Early Mouse Embryos