Name: genotyping of sea anemone during early development
Uploaded: 2019-05-13T14:30:00
Description: Watch this Scientific Journal Video about Genotyping of Sea Anemone during Early Development at JoVE.com

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 animal...

<ol>
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Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CRISPR+knockouts+reveal+an+endogenous+role+for+ancient+neuropeptides+in+regulating+developmental+timing+in+a+sea+anemone.">CRISPR knockouts reveal an endogenous role for ancient neuropeptides in regulating developmental timing in a sea anemone.</a> eLife. 7, e39742 (2018).</li><li>He, S. N., 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=An+axial+Hox+code+controls+tissue+segmentation+and+body+patterning+in+Nematostella+vectensis.">An axial Hox code controls tissue segmentation and body patterning in Nematostella vectensis.</a> Science. 361 (6409), 1377 (2018).</li><li>Ikmi, A., McKinney, S. A., Delventhal, K. M., Gibson, M. 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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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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