Name: use of a recombinant mosquito densovirus as a gene delivery vector for the functional analysis of genes in mosquito larvae
Uploaded: 2017-10-06T13:00:00
Description: Watch this Scientific Journal Video about Use of a Recombinant Mosquito Densovirus As a Gene Delivery Vector for the Functional Analysis of Genes in Mosquito Larvae at JoVE.com

The authors acknowledge financial support from the National Key Research and Development Program of China (2016YFC1200500 to Xiao-Guang Chen), the National Natural Science Foundation of China (81672054 and 81371846), the Research Team Programme of the Natural Science Foundation of Guangdong (2014A030312016), and the Scientific and Technological Programme of Guangzhou (201508020263). We gratefully acknowledge Professor Jonathan Carlson (Colorado State University) for kindly providing the pUCA and p7NS1-GFP plasmids and for critically reading this manuscript.

All protocols were approved by the Ethical Committee of Southern Medical University.
1. Designing an Artificial Intron
NOTE: The artificial intron used in this work is 65 bp in length, and the sequence is 5&#39;-GTAAGAGTCGATCGACGCGTTACTAACTGGTACCTCTTCTTTTTTTTTTGATATCCTGCAG-3&#39;.
<ol>
	<li>Place the HpaI restriction site on both ends of artificial intron so that HpaI digestion can release the intron from plasmids (see Figure...

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	<li>Tolle, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosquito-borne+diseases.">Mosquito-borne diseases.</a> Current problems in pediatric and adolescent health care. 39, 97-140 (2009).</li><li>Petersen, L. R., Jamieson, D. J., Powers, A. M., Honein, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zika+Virus.">Zika Virus.</a> The New England journal of medicine. 374, 1552-1563 (2016).</li><li>Roberts, D. R., Andre, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insecticide+resistance+issues+in+vector-borne+disease+control.">Insecticide resistance issues in vector-borne disease control.</a> The American journal of tropical medicine and hygiene. 50, 21-34 (1994).</li><li>Attaran, A., Roberts, D. R., Curtis, C. F., Kilama, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Balancing+risks+on+the+backs+of+the+poor.">Balancing risks on the backs of the poor.</a> Nature medicine. 6, 729-731 (2000).</li><li>Volohonsky, G., 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=Transgenic+Expression+of+the+Anti-parasitic+Factor+TEP1+in+the+Malaria+Mosquito+Anopheles+gambiae.">Transgenic Expression of the Anti-parasitic Factor TEP1 in the Malaria Mosquito Anopheles gambiae.</a> PLoS pathogens. 13, 1006113 (2017).</li><li>Galizi, R., 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=A+synthetic+sex+ratio+distortion+system+for+the+control+of+the+human+malaria+mosquito.">A synthetic sex ratio distortion system for the control of the human malaria mosquito.</a> Nature communications. 5, 3977 (2014).</li><li>Bourtzis, K., Lees, R. S., Hendrichs, J., Vreysen, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=More+than+one+rabbit+out+of+the+hat:+Radiation,+transgenic+and+symbiont-based+approaches+for+sustainable+management+of+mosquito+and+tsetse+fly+populations.">More than one rabbit out of the hat: Radiation, transgenic and symbiont-based approaches for sustainable management of mosquito and tsetse fly populations.</a> Acta tropica. 157, 115-130 (2016).</li><li>Kumar, S. S., Puttaraju, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improvised+microinjection+technique+for+mosquito+vectors.">Improvised microinjection technique for mosquito vectors.</a> The Indian journal of medical research. 136, 971-978 (2012).</li><li>Attardo, G. M., Higgs, S., Klingler, K. A., Vanlandingham, D. L., Raikhel, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+interference-mediated+knockdown+of+a+GATA+factor+reveals+a+link+to+anautogeny+in+the+mosquito+Aedes+aegypti.">RNA interference-mediated knockdown of a GATA factor reveals a link to anautogeny in the mosquito Aedes aegypti.</a> Proceedings of the National Academy of Sciences of the United States of America. 100, 13374-13379 (2003).</li><li>Singh, A. D., Wong, S., Ryan, C. P., Whyard, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oral+delivery+of+double-stranded+RNA+in+larvae+of+the+yellow+fever+mosquito,+Aedes+aegypti:+implications+for+pest+mosquito+control.">Oral delivery of double-stranded RNA in larvae of the yellow fever mosquito, Aedes aegypti: implications for pest mosquito control.</a> Journal of insect science. 13, 69 (2013).</li><li>Ward, T. W., 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=Aedes+aegypti+transducing+densovirus+pathogenesis+and+expression+in+Aedes+aegypti+and+Anopheles+gambiae+larvae.">Aedes aegypti transducing densovirus pathogenesis and expression in Aedes aegypti and Anopheles gambiae larvae.</a> Insect molecular biology. 10, 397-405 (2001).</li><li>Carlson, J., Suchman, E., Buchatsky, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Densoviruses+for+control+and+genetic+manipulation+of+mosquitoes.">Densoviruses for control and genetic manipulation of mosquitoes.</a> Advances in virus research. 68, 361-392 (2006).</li><li>Barreau, C., Jousset, F. X., Bergoin, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathogenicity+of+the+Aedes+albopictus+parvovirus+(AaPV),+a+denso-like+virus,+for+Aedes+aegypti+mosquitoes.">Pathogenicity of the Aedes albopictus parvovirus (AaPV), a denso-like virus, for Aedes aegypti mosquitoes.</a> Journal of invertebrate pathology. 68, 299-309 (1996).</li><li>Liu, P., 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=Development+of+non-defective+recombinant+densovirus+vectors+for+microRNA+delivery+in+the+invasive+vector+mosquito,+Aedes+albopictus.">Development of non-defective recombinant densovirus vectors for microRNA delivery in the invasive vector mosquito, Aedes albopictus.</a> Scientific reports. 6, 20979 (2016).</li><li>Ortega, M. M., Bouamar, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Guidelines+on+Designing+MicroRNA+Sponges:+From+Construction+to+Stable+Cell+Line.">Guidelines on Designing MicroRNA Sponges: From Construction to Stable Cell Line.</a> Methods in molecular biology. 1509, 221-233 (2017).</li><li>Froger, A., Hall, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transformation+of+plasmid+DNA+into+E.+coli+using+the+heat+shock+method.">Transformation of plasmid DNA into E. coli using the heat shock method.</a> Journal of visualized experiments : JoVE. , e253 (2007).</li><li>Afanasiev, B. N., Kozlov, Y. V., Carlson, J. O., Beaty, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Densovirus+of+Aedes+aegypti+as+an+expression+vector+in+mosquito+cells.">Densovirus of Aedes aegypti as an expression vector in mosquito cells.</a> Experimental parasitology. 79, 322-339 (1994).</li><li>Hu, H. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+the+human-specific+microRNA+miR-941.">Evolution of the human-specific microRNA miR-941.</a> Nature communications. 3, 1145 (2012).</li><li>Sanger, F., Nicklen, S., Coulson, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+sequencing+with+chain-terminating+inhibitors.">DNA sequencing with chain-terminating inhibitors.</a> Proceedings of the National Academy of Sciences of the United States of America. 74, 5463-5467 (1977).</li><li>Dalby, B., 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=Advanced+transfection+with+Lipofectamine+2000+reagent:+primary+neurons,+siRNA,+and+high-throughput+applications.">Advanced transfection with Lipofectamine 2000 reagent: primary neurons, siRNA, and high-throughput applications.</a> Methods (San Diego, Calif). 33, 95-103 (2004).</li><li>Gu, J. B., Dong, Y. Q., Peng, H. J., Chen, X. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+recombinant+AeDNA+containing+the+insect-specific+toxin,+BmK+IT1,+displayed+an+increasing+pathogenicity+on+Aedes+albopictus.">A recombinant AeDNA containing the insect-specific toxin, BmK IT1, displayed an increasing pathogenicity on Aedes albopictus.</a> The American journal of tropical medicine and hygiene. 83, 614-623 (2010).</li><li>Hou, Y., Zhang, H., Miranda, L., Lin, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Serious+overestimation+in+quantitative+PCR+by+circular+(supercoiled)+plasmid+standard:+microalgal+pcna+as+the+model+gene.">Serious overestimation in quantitative PCR by circular (supercoiled) plasmid standard: microalgal pcna as the model gene.</a> PloS one. 5, 9545 (2010).</li><li>Ding, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+rAAV9+to+Overexpress+or+Knockdown+Genes+in+Mouse+Hearts.">Preparation of rAAV9 to Overexpress or Knockdown Genes in Mouse Hearts.</a> Journal of visualized experiments : JoVE. , (2016).</li></ol>

It is important to overcome two of the key barriers that limit rAaeDV construction. The first is the production of defective recombinant virus. It has been reported that MDV can be used as a vector to express appropriately sized foreign genes, such as scorpion insect-specific neurotoxins20 and the GFP protein; however, regardless of the construction strategy, once the ORFs of MDV are inserted or replaced with exogenous genes, virions cannot form independently unless a helper plasmid is cotransfected to supply the missing...

Mosquito-borne diseases such as malaria, dengue fever, zika fever, and yellow fever, are major international public health problems that continue to account for a significant fraction of the global infectious disease burden1,2. Conventional insecticides, which have been used in response to vectors, are a major component of sustainable integrated mosquito control strategy for the prevention of mosquito-borne diseases. However, such strategies have proven to be relatively ineffective or undesirable due to the associated negative environmental impacts as well as the evolution of resistance in mosquito populations3,4. For these reasons, there is an urgent need for alternative methods of mosquito control, and the use of transgenic methods to produce sterile male mosquitoes and the release of pathogen-resistant mosquitoes have arisen as promising new control strategies. To develop effective new control methods, such as safe and effective approaches for in vivo gene delivery, the comprehensive analysis of mosquito gene function is required.
Direct microinjection of plasmid DNA, double stranded RNA (dsRNA) or small interfering RNA (siRNA) is the most commonly used in vivo gene delivery method in mosquitoes. In fact, the production of transgenic strains of mosquitoes still rely on a process of embryo microinjection5,6,7. However, microinjection has several limitations.First, this technique is technically demanding and involves complicated procedures. Second, injection causes a physical insult to the embryo, larvae, pupae, and adult, which directly affects the viability of the target organism. Third, it is difficult to immobilize mosquito larvae for microinjection because most live in an aquatic habitat and possess a characteristic wriggling movement. Fourth, the size of 1st-2nd instar larvae is 10- to 20-fold smaller than that of 4th instar and older larvae, and the cuticles of the former are more delicate. These features make it difficult to manipulate 1st-2nd instar larvae compared to those in older stages. Combined, these factors contribute to a reduced post-injection survival rate for larvae (approximately 5%) compared to adults8. Viral-based delivery systems have been developed to overcome the associated extracellular and intracellular barriers. These systems have the advantages of easy manipulation, high transduction efficiency, long-term and robust levels of expression, and the ability to produce persistent effects in vivo. Therefore, gene delivery systems utilizing retroviruses, lentiviruses, and adenoviruses have been widely used inmammalian cell lines and model species. The Sindbis viral expression system had been previously used to analyze the gene function in the adult mosquito; besides the biosafety concerns, however, the injection is still a necessary process for viral infection9. Although, the oral delivery by soaking larvae in the dsRNA solution has been reported previously as a feasible delivery method, it is unsuitable for small RNA function analysis10. So, effective viral delivery methods must still be developed for mosquitoes.
Mosquito densoviruses (MDVs) are part of the Densovirinae subfamily of Parvoviridae, and all but one fall within the genus Brevidensovirus11. MDV virions are non-enveloped and consist of a single-stranded DNA (ssDNA) genome and an icosahedral capsid (20 nm in diameter). The viral genome is approximately 4 kb in size and is replicated within the nuclei of host cells. MDVs are relatively stable in the environment and show a narrow host range with high specificity for mosquitoes. These viruses have the potential to spread and persist naturally in mosquito populations and can invade almost all organs and tissues of these insects, including the midgut, Malpighian tubules, fat body, musculature, neurons, and salivary glands12.
Intact MDV genomes can be subcloned into plasmid vectors to produce plasmid-based infectious clones; when these clones are delivered into mosquito cells, the viral genome is extracted from the plasmid vector, and infectious viral particles are produced. Because MDV has a small ssDNA genome, infectious clones are easily constructed and the viral genome can be easily manipulated11,13. These characteristics make MDV a valuable agent for examining mosquito biology. However, because nearly all of the viral genome sequence is essential for viral proliferation, the creation of recombinant virus through the replacement or insertion of foreign genes causes a loss in viral packaging and/or replication abilities, which creates a barrier for the development of MDVs as gene delivery vectors. Herein, we report using an artificial intronic small-RNA expression strategy to develop a non-defective rAaeDV in vivo RNA delivery system that has the advantages of easy plasmid construction and the maintenance of a functional virus that can produce stable and long-term expression in host cells without the need for wild-type virus. Additionally, this method allows for the easy transduction of larvae.
The protocols for the following steps are described in this study: 1) design of rAaeDVs encoding an intronic small-RNA expression cassette, 2) production of recombinant virus particles using the C6/36 packaging cell line, 3) quantitative analysis of cell-free rAaeDV genome copy numbers, and 4) infection of Ae. albopictus larvae by direct introduction of virus into the water body of the larval habitat. Overall, this work demonstrated that specific small RNAs or target genes can be overexpressed or knocked down in mosquito larvae using the developed MDV delivery system.

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			<td height="21" style="width:401px;height:21px;">Roswell Park Memorial Institute (RPMI) 1640 medium</td>
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			<td height="21" style="width:401px;height:21px;">Fetal Bovine Serum&#65288; Australia Origin&#65289;</td>
			<td style="width:215px;">Gibco&#65292; Life Technologies</td>
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			<td height="21" style="width:401px;height:21px;">penicillin/streptomycin</td>
			<td style="width:215px;">Gibco&#65292; Life Technologies</td>
			<td style="width:119px;">15070063</td>
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			<td height="23" style="width:401px;height:23px;">Lipofectamine 2000 Transfection Reagent</td>
			<td style="width:215px;">&#160;Invitrogen&#65292;Life Technologies</td>
			<td style="width:119px;">11668019</td>
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			<td height="21" style="width:401px;height:21px;">Proteinase K</td>
			<td style="width:215px;">Promega</td>
			<td>MC5008</td>
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			<td height="21" style="width:401px;height:21px;">DNase I (RNase-free)</td>
			<td style="width:215px;">&#160;Invitrogen&#65292;Life Technologies</td>
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use of a recombinant mosquito densovirus as a gene delivery vector for the functional analysis of genes in mosquito larvae

In vivo microinjection is the most commonly used gene transfer technique for analyzing the gene functions in individual mosquitoes. However, this method requires a more technically demanding operation and involves complicated procedures, especially when used in larvae due to their small size, relatively thin and fragile cuticle, and high mortality, which limit its application. In contrast, viral vectors for gene delivery have been developed to surmount extracellular and intracellular barriers. These systems have the advantages of easy manipulation, high gene transduction efficiency, long-term maintenance of gene expression, and the ability to produce persistent effects in vivo. Mosquito densoviruses (MDVs) are mosquito-specific, small single-stranded DNA viruses that can effectively deliver foreign nucleic acids into mosquito cells; however, the replacement or insertion of foreign genes to create recombinant viruses typically causes a loss of packaging and/or replication abilities, which is a barrier to the development of these viruses as delivery vectors.
Herein, we report using an artificial intronic small-RNA expression strategy to develop a non-defective recombinant Aedes aegypti densovirus (AaeDV) in vivo delivery system. Detailed procedures for the construction, packaging and quantitative analysis of the rAaeDV vectors, and for larval infection are described.
This study demonstrates, for the first time, the feasibility of developing a non-defective recombinant MDV micro RNA (miRNA) expression system, and thus providing a powerful tool for the functional analysis of genes in mosquito and establishing a basis for the application of viral paratransgenesis for controlling mosquito-borne diseases. We demonstrated that Aedes albopictus 1st instar larvae could be easily and effectively infected by introducing the virus into the water body of the larvae breeding site and that the developed rAaeDVs could be used to overexpress or knock down the expression of a specific target gene in larvae, providing a tool for the functional analysis of mosquito genes.

Strategies for rAaeDV construction&#160; 
A defective rAaeDV vector was generated to express the DsRed gene in mosquito larvae. The resulting plasmid contained a NS1-DsRed fusion protein cassette with the VP protein deleted (Figure 1A). rAaeDV plasmids containing expression constructs for miRNA, miRNA sponge, shRNA and amiRNA were designed (shown in Figure 1B). For example, ...

Watch this Scientific Journal Video about Use of a Recombinant Mosquito Densovirus As a Gene Delivery Vector for the Functional Analysis of Genes in Mosquito Larvae at JoVE.com

Use of a Recombinant Mosquito Densovirus As a Gene Delivery Vector for the Functional Analysis of Genes in Mosquito Larvae

We report using an artificial intronic small RNA expression strategy to develop a non-defective recombinant Aedes aegypti densovirus (AaeDV) in vivo delivery system. A detailed procedure for the construction, packaging, and quantitative analysis of the rAaeDV vectors as well as for larval infection is described.

In vivo microinjection is the most commonly used gene transfer technique for analyzing the gene functions in individual mosquitoes. However, this method ...

The overall goal of this procedure is to analyze the gene function of mosquito larvae, using recombinant mosquito densovirus as a gene delivery. This method can help answer key questions in viral-based delivery systems, such as how to overcome the associated extracellular and intracellular barriers. The main advantages of these techniques are easy manipulation, high transduction efficiency, long-term and robust use of expressions, and the ability to produce persistent effects in vivo.This work demonstrated that specific small RNAs or target genes can be overexpressed or knocked down in mosquito larvae, using the developed densovirus delivery system. The implications of this technique extend the applications of the described expression strategy to investigate mosquito biology because this method allows for easy transductions of larvae. Demonstrating the procedure will be Pei-Wen Liu, a doctoral candidate from our laboratory.Start by ordering the chemical synthesis of full-length cDNA sequences for the precursor miRNAs, miRNA sponges, and shRNA, as described in the accompanying text protocol. After receiving the ordered DNA, spin the tubes containing DNA blocks to ensure that all of the dried DNA is at the bottom of the tube. Then, resuspend the DNA in DNase-free water to achieve a final concentration of 10 nanograms per microliter.Add six microliters of XbaI to digest plasmid backbone and cDNA sequences, and place the reaction at 37 degrees Celsius for one hour. Then, dephosphorylate the five-prime ends of the linearized plasmid backbone with calf-intestinal alkaline phosphatase, according to the manufacturer's instructions. For efficient packaging, the genome size cannot exceed 4, 400 nucleotide, representing 110%of the length of the wild-type mosquito densovirus genome, or intronic microRNA expression consist of no more than 400 nucleotide can be introduced into the Aedes aegypti genome.Next, heat inactivate the alkaline phosphatase at 65 degrees Celsius. Then, run the DNA on a 1%agarose gel, and cut the linearized backbone. Extract the DNA from the gel slice, using a gel extraction kit, following the manufacturer's instructions.Once extracted, ligate the DNA fragment into the backbone, using T4 DNA ligase. Then, use heat shock to transform the products of the ligation reaction into competent DH5-alpha E.coli cells. Plate the transformed bacteria on an LB agar plate containing 100 micrograms per milliliter of ampicillin.The next day, pick a single colony from the plate, and create a starter culture, using three milliliters enriched medium containing 100 micrograms per milliliter of ampicillin. Finally, extract the plasmid DNA from the bacterial culture, using a miniprep kit, following the manufacturer's instructions. Send a sample of the DNA to a DNA sequencing company for verification.Ligate pre-miRNA or shRNA into the HpaI site of the AaeDV NS1 coding region in the pUCA plasmid backbone, using the methods that were shown for the artificial intronic small-RNA expression cassette. In place of using DH5-alpha cells, transform the DNA into Stbl3 competent E.coli cells. Then, plate the transformed cells onto an LB agar plate containing 100 micrograms per milliliter of ampicillin, and make a starter culture from a positive clone.Following this, extract the rAaeDV plasmid from the bacterial cells, using a maxiprep kit, following the manufacturer's instructions. On day zero, split 90 to 95%confluent flasks of C6/36 cells one to two into 10 T-25 culture flasks. Incubate the flasks for 18 to 20 hours at 28 degrees Celsius until they again reach 90 to 95%confluence.On day one, transfect the cells with the generated rAaeDV plasmids. To accomplish this, dilute 10 micrograms of DNA into 600 microliters of RPMI-1640 medium, and mix the solution gently. Meanwhile, prepare 600 microliters of RPMI-1640 medium and 25 microliters of transfection reagent per transfection.Incubate the cells with the DNA for five to 10 minutes at room temperature. Then, add 625 microliters of the RPMI-1640 transfection reagent mixture to the plasmid DNA mixture, and incubate this mixture for 20 to 30 minutes at room temperature. Following incubation, wash the cells twice with RPMI-1640 medium, and then add the transfection mixture to each of the T-25 culture flasks.Incubate the cells in the transfection mixture for six hours at 28 degrees Celsius. After six hours, remove the transfection media, wash the cells twice with five milliliters of RPMI-1640 medium, and then add fresh RPMI-1640 medium containing 10%FBS. Five days after transfection, use a five-milliliter glass dropper to dislodge and suspend the cells in the dishes by pipetting up and down with the culture medium.Transfer the cell suspensions from each flask into their own sterile 50-milliliter tube. To harvest a high threshold whereas it is necessary to maintain the cells for five days after transfection. Freeze the individual tubes at negative 80 degrees Celsius or in a dry ice ethanol bath for 30 minutes.Then, quick thaw them at 37 degrees Celsius, and vortex the cell suspension for one minute. Next, collect the supernatant from the centrifuged sample, and discard the pellet. Then, pass the supernatant through a 0.22 micrometer disposable syringe filter.Aliquot and store the final purified virion stocks at negative 80 degrees Celsius. Wash 100 first-instar A.albopictus larvae three times, using deionized water. And then, transfer the larvae into a beaker containing 95 milliliters of deionized water.Add five milliliters of the rAaeDV stocks, and incubate the larvae for 24 hours at 28 degrees Celsius. For success for larva infection, it is essential for larvae to be contained with infection virus particles for 24 to 36 hour to ensure high infection ratios. Following the incubation, wash the larvae three times using deionized water, and then transfer the larvae back to the plates.Feed the larvae regularly. Monitor the level of target gene expression in the larvae, using quantitative PCR or western blot, using standard techniques. In this example, 100 first-instar larvae were analyzed for their endogenous miRNA expression after infection with the recombinant virus containing the aal-let-7 expression cassette showing overexpression.The efficiency of the anti-let-7 construct is shown on the right, highlighting its knockdown capabilities. In order to monitor the V-ATPase mRNA knockdown efficiency of the rAaeDV vectors, a total of 100 first-instar larvae were treated with equal amounts of rAaeDV of varying types by adding the virus into the water body of the larval habitat. The V-ATPase mRNA levels were substantially reduced by an miRNA expressing rAaeDV and by intronic shRNA expressing rAaeDV.Our results validate an intronic expression strategy that offers a new paradigm, which can overcome the limitations of mosquito densoviruses with defective genome, to enable efficient delivery of foreign genes into mosquitoes. While attempting this procedure, it is important to remember that an intronic microRNA expression cassette of no more than 400 nt can be introduced into the Aedes aegypti densovirus genome. After its development, this technique paved the way for research in productions of non-defective recombinant mosquito densovirus that can overexpress or downregulate microRNAs and the target genes to explore functional analysis of mosquito genes.After watching this video, you should have good understanding of how to use developed mosquito densovirus delivery system to analyze the gene functions in mosquito larvae.

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Research

JoVE Journal

Developmental Biology

Differentiation of a Human Neural Stem Cell Line on Three Dimensional Cultures, Analysis of MicroRNA and Putative Target Genes

Neural stem cells (NSCs) are capable of self-renewal and differentiation into neurons, astrocytes and oligodendrocytes under specific local microenvironments. In here, we present a set of methods used for three dimensional (3D) differentiation and miRNA analysis of a clonal human neural stem cell (hNSC) line, currently in clinical trials for stroke disability (NCT01151124 and NCT02117635, Clinicaltrials.gov). HNSCs were derived from an ethical approved first trimester human fetal cortex and conditionally immortalized using retroviral integration of a single copy of the c-mycERTAMconstruct. We describe how to measure axon process outgrowth of hNSCs differentiated on 3D scaffolds and how to quantify associated changes in miRNA expression using PCR array. Furthermore we exemplify computational analysis with the aim of selecting miRNA putative targets. SOX5 and NR4A3 were identified as suitable miRNA putative target of selected significantly down-regulated miRNAs in differentiated hNSC. MiRNA target validation was performed on SOX5 and NR4A3 3&#8217;UTRs by dual reporter plasmid transfection and dual luciferase assay.

With the intent of characterizing changes in miRNAs on differentiated human neural stem cells (hNSCs) we describe hNSC differentiation on a three dimensional system,the evaluation of changes in microRNA expression by miRNA PCR array, and computational analysis for miRNA target prediction and its validation by dual luciferase assay.

Neural stem cells (NSCs) are capable of self-renewal and differentiation into neurons, astrocytes and oligodendrocytes under specific local ...

Mosaic Zebrafish Transgenesis for Functional Genomic Analysis of Candidate Cooperative Genes in Tumor Pathogenesis

Comprehensive genomic analysis has uncovered surprisingly large numbers of genetic alterations in various types of cancers. To robustly and efficiently identify oncogenic &#8220;drivers&#8221; among these tumors and define their complex relationships with concurrent genetic alterations during tumor pathogenesis remains a daunting task. Recently, zebrafish have emerged as an important animal model for studying human diseases, largely because of their ease of maintenance, high fecundity, obvious advantages for in vivo imaging, high conservation of oncogenes and their molecular pathways, susceptibility to tumorigenesis and, most importantly, the availability of transgenic techniques suitable for use in the fish. Transgenic zebrafish models of cancer have been widely used to dissect oncogenic pathways in diverse tumor types. However, developing a stable transgenic fish model is both tedious and time-consuming, and it is even more difficult and more time-consuming to dissect the cooperation of multiple genes in disease pathogenesis using this approach, which requires the generation of multiple transgenic lines with overexpression of the individual genes of interest followed by complicated breeding of these stable transgenic lines. Hence, use of a mosaic transient transgenic approach in zebrafish offers unique advantages for functional genomic analysis in vivo. Briefly, candidate transgenes can be coinjected into one-cell-stage wild-type or transgenic zebrafish embryos and allowed to integrate together into each somatic cell in a mosaic pattern that leads to mixed genotypes in the same primarily injected animal. This permits one to investigate in a faster and less expensive manner whether and how the candidate genes can collaborate with each other to drive tumorigenesis. By transient overexpression of activated ALK in the transgenic fish overexpressing MYCN, we demonstrate here the cooperation of these two oncogenes in the pathogenesis of a pediatric cancer, neuroblastoma that has resisted most forms of contemporary treatment.

The goal of this study is to demonstrate how the mosaic transgenesis strategy can be used in zebrafish to rapidly and efficiently assess the relative contributions of multiple oncogenes in tumor initiation and progression in vivo.

Comprehensive genomic analysis has uncovered surprisingly large numbers of genetic alterations in various types of cancers.  To robustly and efficiently ...

Capturing Tissue Repair in Zebrafish Larvae with Time-lapse Brightfield Stereomicroscopy

The zebrafish larval tail fin is ideal for studying tissue regeneration due to the simple architecture of the larval fin-fold, which comprises of two layers of skin that enclose undifferentiated mesenchyme, and because the larval tail fin regenerates rapidly within 2-3 days. Using this system, we demonstrate a method for capturing the repair dynamics of the amputated tail fin with time-lapse video brightfield stereomicroscopy. We demonstrate that fin amputation triggers a contraction of the amputation wound and extrusion of cells around the wound margin, leading to their subsequent clearance. Fin regeneration proceeds from proximal to distal direction after a short delay. In addition, developmental growth of the larva can be observed during all stages. The presented method provides an opportunity for observing and analyzing whole tissue-scale behaviors such as fin development and growth in a simple microscope setting, which is easily adaptable to any stereomicroscope with time-lapse capabilities.

We present a protocol for capturing the dynamics of zebrafish larval tail fin regeneration on a whole-tissue scale using brightfield-based stereomicroscopy. This technique enables capturing the regeneration dynamics with single cell resolution. This methodology can be adapted to any stereomicroscope equipped with a CCD camera and time-lapse software.

The zebrafish larval tail fin is ideal for studying tissue regeneration due to the simple architecture of the larval fin-fold, which comprises of two ...

Analysis of Zebrafish Larvae Skeletal Muscle Integrity with Evans Blue Dye

The zebrafish model is an emerging system for the study of neuromuscular disorders. In the study of neuromuscular diseases, the integrity of the muscle membrane is a critical disease determinant. To date, numerous neuromuscular conditions display degenerating muscle fibers with abnormal membrane integrity; this is most commonly observed in muscular dystrophies. Evans Blue Dye (EBD) is a vital, cell permeable dye that is rapidly taken into degenerating, damaged, or apoptotic cells; in contrast, it is not taken up by cells with an intact membrane. EBD injection is commonly employed to ascertain muscle integrity in mouse models of neuromuscular diseases. However, such EBD experiments require muscle dissection and/or sectioning prior to analysis. In contrast, EBD uptake in zebrafish is visualized in live, intact preparations. Here, we demonstrate a simple and straightforward methodology for performing EBD injections and analysis in live zebrafish. In addition, we demonstrate a co-injection strategy to increase efficacy of EBD analysis. Overall, this video article provides an outline to perform EBD injection and characterization in zebrafish models of neuromuscular disease.

In this study, we describe a straightforward method to perform Evans Blue Dye (EBD) analysis on zebrafish larvae. This technique is a powerful tool for the characterization of skeletal muscle integrity and delineation of zebrafish models of muscular dystrophy, and is a valuable method for the development of novel therapeutics.

The zebrafish model is an emerging system for the study of neuromuscular disorders.  In the study of neuromuscular diseases, the integrity of the muscle ...

Methods to Examine the Lymph Gland and Hemocytes in Drosophila Larvae

Many parallels exist between the Drosophila and mammalian hematopoietic systems, even though Drosophila lack the lymphoid lineage that characterize mammalian adaptive immunity. Drosophila and mammalian hematopoiesis occur in spatially and temporally distinct phases to produce several blood cell lineages. Both systems maintain reservoirs of blood cell progenitors with which to expand or replace mature lineages. The hematopoietic system allows Drosophila and mammals to respond to and to adapt to immune challenges. Importantly, the transcriptional regulators and signaling pathways that control the generation, maintenance, and function of the hematopoietic system are conserved from flies to mammals. These similarities allow Drosophila to be used to genetically model hematopoietic development and disease.
Here we detail assays to examine the hematopoietic system of Drosophila larvae. In particular, we outline methods to measure blood cell numbers and concentration, visualize a specific mature lineage in vivo, and perform immunohistochemistry on blood cells in circulation and in the hematopoietic organ. These assays can reveal changes in gene expression and cellular processes including signaling, survival, proliferation, and differentiation and can be used to investigate a variety of questions concerning hematopoiesis. Combined with the genetic tools available in Drosophila, these assays can be used to evaluate the hematopoietic system upon defined genetic alterations. While not specifically outlined here, these assays can also be used to examine the effect of environmental alterations, such as infection or diet, on the hematopoietic system.

Methods to Examine the Lymph Gland and Hemocytes in Drosophila Larvae

Drosophila and mammalian hematopoietic systems share many common features, making Drosophila an attractive genetic model to study hematopoiesis. Here we demonstrate dissection and mounting of the major larval hematopoietic organ for immunohistochemistry. We also describe methods to assay various larval hematopoietic compartments including circulating hemocytes and sessile crystal cells.

Many parallels exist between the Drosophila and mammalian hematopoietic systems, even though Drosophila lack the lymphoid lineage that characterize ...

Rapid Isolation of BMPR-IB+ Adipose-Derived Stromal Cells for Use in a Calvarial Defect Healing Model

Invasive cancers, major injuries, and infection can cause bone defects that are too large to be reconstructed with preexisting bone from the patient's own body. The ability to grow bone de novo using a patient's own cells would allow bony defects to be filled with adequate tissue without the morbidity of harvesting native bone. There is interest in the use of adipose-derived stromal cells (ASCs) as a source for tissue engineering because these are obtained from an abundant source: the patient's own adipose tissue. However, ASCs are a heterogeneous population and some subpopulations may be more effective in this application than others. Isolation of the most osteogenic population of ASCs could improve the efficiency and effectiveness of a bone engineering process. In this protocol, ASCs are obtained from subcutaneous fat tissue from a human donor. The subpopulation of ASCs expressing the marker BMPR-IB is isolated using FACS. These cells are then applied to an in vivo calvarial defect healing assay and are found to have improved osteogenic regenerative potential compared with unsorted cells.

Adipose-derived stromal cells may be useful for engineering new tissue from a patient's own cells. We present a protocol for the isolation of a subpopulation of human adipose-derived stromal cells (ASCs) with increased osteogenic potential, followed by application of the cells in an in vivo calvarial healing assay.

Invasive cancers, major injuries, and infection can cause bone defects that are too large to be reconstructed with preexisting bone from the patient's own ...

Hypoxic Preconditioning of Marrow-derived Progenitor Cells As a Source for the Generation of Mature Schwann Cells

This manuscript describes a means to enrich for neural progenitors from the marrow stromal cell (MSC) population and thereafter to direct them to the mature Schwann cell fate. We subjected rat and human MSCs to transient hypoxic conditions (1% oxygen for 16 h) followed by expansion as neurospheres upon low-attachment substratum with epidermal growth factor (EGF)/basic fibroblast growth factor (bFGF) supplementation. Neurospheres were seeded onto poly-D-lysine/laminin-coated tissue culture plastic and cultured in a gliogenic cocktail containing &#946;-Heregulin, bFGF, and platelet-derived growth factor (PDGF) to generate Schwann cell-like cells (SCLCs). SCLCs were directed to fate commitment via coculture for 2 weeks with purified dorsal root ganglia (DRG) neurons obtained from E14-15 pregnant Sprague Dawley rats. Mature Schwann cells demonstrate persistence in S100&#946;/p75 expression and can form myelin segments. Cells generated in this manner have potential applications in autologous cell transplantation following spinal cord injury, as well as in disease modeling.

Marrow stromal cells (MSCs) with neural potential exist within the bone marrow. Our protocol enriches this population of cells via hypoxic preconditioning and thereafter directs them to become mature Schwann cells.

This manuscript describes a means to enrich for neural progenitors from the marrow stromal cell (MSC) population and thereafter to direct them to the ...

A Method for Characterizing Embryogenesis in Arabidopsis

Given the highly predictable nature of their development, Arabidopsis embryos have been used as a model for studies of morphogenesis in plants. However, early stage plant embryos are small and contain few cells, making them difficult to observe and analyze. A method is described here for characterizing pattern formation in plant embryos under a microscope using the model organism Arabidopsis. Following the clearance of fresh ovules using Hoyer's solution, the cell number in and morphology of embryos could be observed, and their developmental stage could be determined by differential interference contrast microscopy using a 100X oil immersion lens. In addition, the expression of specific marker proteins tagged with Green Fluorescent Protein (GFP) was monitored to annotate cell identity specification during embryo patterning by confocal laser scanning microscopy. Thus, this method can be used to observe pattern formation in wild-type plant embryos at the cellular and molecular levels, and to characterize the role of specific genes in embryo patterning by comparing pattern formation in embryos from wild-type plants and embryo-lethal mutants. Therefore, the method can be used to characterize embryogenesis in Arabidopsis.

A Method for Characterizing Embryogenesis in Arabidopsis

This protocol outlines a method for observing embryogenesis in Arabidopsis via ovule clearance followed by the inspection of embryo pattern formation under a microscope.

Given the highly predictable nature of their development, Arabidopsis embryos have been used as a model for studies of morphogenesis in plants. However, ...

A Novel Use of Three-dimensional High-frequency Ultrasonography for Early Pregnancy Characterization in the Mouse

High-frequency ultrasonography (HFUS) is a common method to non-invasively monitor the real-time development of the human fetus in utero. The mouse is routinely used as an in vivo model to study embryo implantation and pregnancy progression. Unfortunately, such murine studies require pregnancy interruption to enable follow-up phenotypic analysis. To address this issue, we used three-dimensional (3-D) reconstruction of HFUS imaging data for early detection and characterization of murine embryo implantation sites and their individual developmental progression in utero. Combining HFUS imaging with 3-D reconstruction and modeling, we were able to accurately quantify embryo implantation site number as well as monitor developmental progression in pregnant C57BL6J/129S mice from 5.5 days post coitus (d.p.c.) through to 9.5 d.p.c. with the use of a transducer. Measurements included: number, location, and volume of implantation sites as well as inter-implantation site spacing; embryo viability was assessed by cardiac activity monitoring. In the immediate post-implantation period (5.5 to 8.5 d.p.c.), 3-D reconstruction of the gravid uterus in both mesh and solid overlay format enabled visual representation of the developing pregnancies within each uterine horn. As genetically engineered mice continue to be used to characterize female reproductive phenotypes derived from uterine dysfunction, this method offers a new approach to detect, quantify, and characterize early implantation events in vivo. This novel use of 3-D HFUS imaging demonstrates the ability to successfully detect, visualize, and characterize embryo-implantation sites during early murine pregnancy in a non-invasive manner. The technology offers a significant improvement over current methods, which rely on the interruption of pregnancies for gross tissue and histopathologic characterization. Here we use a video and text format to describe how to successfully perform ultrasounds of early murine pregnancy to generate reliable and reproducible data with reconstruction of the uterine form in mesh and solid 3-D images.

Mice are widely used to study gestational biology. However, pregnancy termination is required for such studies which precludes longitudinal investigations and necessitates the use of large numbers of animals. Therefore, we describe a non-invasive technique of high-frequency ultrasonography for early detection and monitoring of post-implantation events in the pregnant mouse.

High-frequency ultrasonography (HFUS) is a common method to non-invasively monitor the real-time development of the human fetus in utero. The mouse is ...

Generation of Scaffold-free, Three-dimensional Insulin Expressing Pancreatoids from Mouse Pancreatic Progenitors In Vitro

The pancreas is a complex organ composed of many different cell types that work together to regulate blood glucose homeostasis and digestion. These cell types include enzyme-secreting acinar cells, an arborized ductal system responsible for the transportation of enzymes to the gut, and hormone-producing endocrine cells. 
Endocrine beta-cells are the sole cell type in the body that produce insulin to lower blood glucose levels. Diabetes, a disease characterized by a loss or the dysfunction of beta-cells, is reaching epidemic proportions. Thus, it is essential to establish protocols to investigate beta-cell development that can be used for screening purposes to derive the drug and cell-based therapeutics. While the experimental investigation of mouse development is essential, in vivo studies are laborious and time-consuming. Cultured cells provide a more convenient platform for screening; however, they are unable to maintain the cellular diversity, architectural organization, and cellular interactions found in vivo. Thus, it is essential to develop new tools to investigate pancreatic organogenesis and physiology.
Pancreatic epithelial cells develop in the close association with mesenchyme from the onset of organogenesis as cells organize and differentiate into the complex, physiologically competent adult organ. The pancreatic mesenchyme provides important signals for the endocrine development, many of which are not well understood yet, thus difficult to recapitulate during the in vitro culture. Here, we describe a protocol to culture three-dimensional, cellular complex mouse organoids that retain mesenchyme, termed pancreatoids. The e10.5 murine pancreatic bud is dissected, dissociated, and cultured in a scaffold-free environment. These floating cells self-assemble with mesenchyme enveloping the developing pancreatoid and a robust number of endocrine beta-cells developing along with the acinar and the duct cells. This system can be used to study the cell fate determination, structural organization, and morphogenesis, cell-cell interactions during organogenesis, or for the drug, small molecule, or genetic screening.

Generation of Scaffold-free, Three-dimensional Insulin Expressing Pancreatoids from Mouse Pancreatic Progenitors In Vitro

Here, we present a protocol to generate insulin expressing 3D murine pancreatoids from free-floating e10.5 dissociated pancreatic progenitors and the associated mesenchyme.

The pancreas is a complex organ composed of many different cell types that work together to regulate blood glucose homeostasis and digestion. These cell ...