The authors thank Victoria Carpenter for her critical comments of this protocol.

Part I - RNAi-mediated gene knockdown in adult Aedes aegypti mosquitoes. For experiment overview see Figure 1.
1. dsRNA Synthesis
<ol>
 <li>Synthesize specific dsRNAs against genes of interest and control dsRNAs. 
 Note: We recommend developing primers for PCR fragments in the range of 300 to 500 base pairs located at the 3' end of the specific cDNA2 and with the T7 primer sequence attached at the 5' end (5'-TAA TAC GAC TCA CTA TAG GG-3'). Uniqueness of the fragments should be confirmed by BLASTN analysis3. </li>
 <li>Use the Ambion Megascript T7 High Yield Transcription Kit (Ambion, table of reagents) that utilizes T7 RNA polymerase for the transcription reaction to synthesize dsRNA. Note: similar reagents and kits are available elsewhere. </li>
 <li>To purify dsRNA, precipitate with lithium chloride following the instructions with the Megascript kit. </li>
 <li>After purification, dissolve the dsRNA pellet in sterile water. To ensure adequate viscosity for microinjection, the dsRNA concentration should not exceed 2 &mu;g/&mu;l. </li>
</ol>
2. Injection Preparation 
<ol>
 <li>A simple micro injector can be constructed by using tubing, scissors, a metal needle, a 1 ml syringe, and a 1 ml plastic pipette tip (see Figure 2). The tubing should be cut to ~ 40 cm in length. Alternatively, an automated micro injector can be used such as Drummond Nanojet II4.
 <ol>
 <li>Cut the tip of the syringe (needle hub) at 2 ml scale mark and remove the rubber plunger head from the plunger. </li>
 <li>Punch a hole using a metal needle in the rubber plunger head and place the rubber plunger head back in the needle hub. </li>
 <li>Place the needle hub in one end of the tubing and place a 1 ml plastic pipette tip in the other end, which will be used as the mouth piece (alternatively, a 10 ml syringe can be used to produce the air pressure necessary for injection). </li>
 </ol>
 </li>
 <li>Place a glass capillary needle in the hole in the rubber plunger head and break the tip of the needle off so the width is big enough for liquid to flow through. Note: The optimal size of the needle tip has to be determined empirically - if the width of the needle is too big this will result in trauma and a high mosquito mortality rate, if the needle width is too small, it will be impossible to penetrate the mosquito exoskeleton. </li>
 <li>Submerge the injection needle in the prepared dsRNA sample and draw the liquid sample into the injection needle by sucking the liquid up with the mouth piece (or a syringe). Note: This step is identical for all liquid reagents that are injected into mosquitoes, including PBS buffer, which is used in the in vivo diuresis assay protocol (see below). </li>
</ol>
3. Collect and Anesthetize Mosquitoes 
<ol>
 <li>Collect mosquitoes with a battery powered aspirator into a collection vial. Place a cap over the collection vial and place the vial on a clean CO2 pad to anesthetize mosquitoes. Note: Alternatively mosquitoes can be anesthetized on ice. </li>
</ol>
4. Mosquito Injection
<ol>
 <li>Open the collection vial and place the mosquitoes directly on the CO2 pad and wait until mosquitoes are anesthetized. </li>
 <li>Discard all males. </li>
 <li>Line up the mosquitoes on the side to allow for easier access for injection. </li>
 <li>Grab mosquitoes by the legs or wings to avoid injury. You can also use a fine paintbrush or feather to manipulate mosquitoes. </li>
 <li>When ready to inject the first mosquito, gently support one side of the thorax with the forceps and insert the tip of the needle into the other side of the thorax (Figure 2). It is better to inject into a thin portion of the cuticle and avoid pushing the needle too deep into the thorax. </li>
 <li>Once the needle is in place, blow the liquid into the mosquito. The desired amount can be determined by monitoring the liquid meniscus in the needle. The number of millimeters necessary for a specific volume can be determined by calculating the cylinder volume of the glass capillary needle (&pi;r2h). The effective amount of dsRNA that is typically used for injection is 1 &mu;g. </li>
 <li>Once the liquid is injected into mosquito, carefully retract the needle. If a large liquid droplet forms on the outside of the thorax, the mosquito should be discarded. Then, repeat this process with the next mosquito. </li>
</ol>
5. Mosquito Recovery and Storage 
<ol>
 <li>After injection, place the mosquitoes in a container for storage. For example, one pint wax lined cardboard cups (soup cups) with mesh covering secured with the cardboard lid. The lid has a portion cut out for the mesh covering to be exposed. Once all the mosquitoes are placed in the container, place the container in an environmentally controlled chamber for incubation and provide the mosquitoes with a food source, such as 20% sucrose soaked cotton balls placed on top of the mesh covering. Before performing the in vivo diuresis assay, deprive the dsRNA-injected mosquitoes of a water source for 12 hrs to standardize the hydration state of each mosquito. </li>
 <li>The efficiency of dsRNA-mediated gene knockdown can be variable. Gene silencing could begin 1 day after injection and it could last up to 6 days after injection4. The optimal time to achieve maximum gene knockdown has to be determined empirically for every gene used. Generally, we wait 3 days after dsRNA injection before we proceed. </li>
</ol>
Part II - In vivo diuresis assay in adult Aedes aegypti mosquitoes
Note: This protocol has been developed by the authors and used for RNAi-mediated knockdown of aquaporin proteins in the yellow fever mosquito Aedes aegypti1. To avoid variability between individual mosquitoes, mosquitoes should be analyzed in groups. For technical reasons, we recommend groups of 5 mosquitoes per treatment - there is a limited amount of time to perform the first weight measurement before mosquitoes begin to excrete urine after injection.
6. Collect and Anesthetize Mosquitoes 
<ol>
 <li>Before collection of the mosquitoes, record the weight of an empty collection vial with a cap using an analytical precision balance. This vial will be used for all subsequent measurements. </li>
 <li>Collect 5 female mosquitoes into the weighed collection vial with an aspirator. Place the cap over the collection vial and let it sit on the CO2 pad for several seconds to anesthetize the mosquitoes. </li>
</ol>
7. Initial Weight Measurement 
<ol>
 <li>Take the initial weight measurement of the 5 mosquitoes by placing the collection vial containing the mosquitoes with the cap on the precision balance. </li>
 <li>Calculate the weight of the group of 5 mosquitoes by taking the weight of the mosquitoes and the collection vial with cap and subtracting the weight of the empty collection vial with cap. </li>
 <li>Open the collection vial and place the mosquitoes directly on the CO2 pad after recording the weight of the mosquitoes. If the mosquitoes are beginning to wake up during the weight measurements, set the vial on the CO2 pad for several seconds before opening it and placing the mosquitoes on the pad. </li>
</ol>
8. Injection Preparation
<ol>
 <li>Set up the micro injector following the instructions given in the RNAi-mediated gene knockdown protocol. </li>
 <li>Place a glass capillary needle in the micro injector and break the tip of the needle off so the width is big enough for liquid to flow through. </li>
 <li>Submerge the needle in PBS buffer and draw the buffer into the injection needle, the desired amount to use for this protocol is 1.25 &mu;l of PBS for each mosquito. 
 Note: This amount mimics the average amount of blood plasma that is taken up by a female mosquito5. </li>
</ol>
9. Mosquito Injection
<ol>
 <li>Line up the mosquitoes to allow for easier access with the micro injector. </li>
 <li>Once the needle is in place, blow PBS buffer into the mosquito. </li>
 <li>Once the liquid is injected into the mosquito, a droplet might form on the outside of the thorax. This droplet has to be carefully removed before the next step. </li>
 <li>Repeat this injection process with the next mosquito. With experience, mosquito survival rate will be almost 100% after injection. </li>
</ol>
10. Weighing Mosquitoes
<ol>
 <li>After the injection, gently place the mosquitoes in the collection vial and cap. Take the first weight measurement of the 5 mosquitoes by placing the collection vial containing the mosquitoes with the cap on the precision balance. </li>
 <li>Calculate the weight of the group of 5 mosquitoes by taking the weight of the mosquitoes and the collection vial with cap and subtract the weight of the empty collection vial with cap. Note: mosquitoes will begin to excrete urine within 2 minutes after removal from the CO2 anesthesia pad, so it is important to take the weight measurement before they start to excrete. </li>
 <li>Place mosquitoes in a small container where they will begin to excrete urine. </li>
</ol>
11. Second and Subsequent Weight Measurements 
Note: Weight measurements of the mosquitoes should be taken in 30 minute intervals, but this can be adjusted to shorter or longer intervals depending on excretion rates. 
<ol>
 <li>After 30 minutes, collect the group of 5 mosquitoes with an aspirator into the same collection vial with cap. Take the next weight measurement of the mosquitoes by placing the collection vial containing the mosquitoes with the cap on the precision balance. </li>
 <li>After the measurement, place the mosquitoes in the same holding container for the next 30 minutes. </li>
 <li>Repeat this process for a desired amount of time. </li>
</ol>
12. Determining Mosquito Excretion Rate 
<ol>
 <li>The total amount of liquid that was injected into the group of 5 mosquitoes can be calculated by subtracting the initial weight of the mosquitoes from the weight immediately after injection. </li>
 <li>The amount of urine that was excreted by the group of mosquitoes at a specific time point can be calculated by subtracting the initial weight of the mosquitoes from the weight of the mosquitoes at the specific time point. </li>
 <li>The excretion rate at a specific time point can be calculated by dividing the amount of urine excreted at this time point by the total amount of liquid injected (Table 1). </li>
</ol>
13. Representative Results
RNAi-mediated gene knockdown and in vivo diuresis assay have been used by the Hansen lab to study the effects of aquaporins in Aedes aegypti mosquito diuresis. Three aquaporins that are expressed in Aedes aegypti Malpighian tubules were knocked down with significant effects on excretion rates compared to control mosquitoes1. Figure 4 shows representative results of an experiment where the diuresis assay has been used to compare excretion rates between Aedes aegypti and Culex quinquefasciatus at different temperatures. 
<img src="/files/ftp_upload/3479/3479fig1.jpg" alt="Figure 1" /> 
Figure 1. Flowchart of the RNAi/diuresis assay. 5 groups of 10 mosquitoes each are injected with dsRNA for a specific gene and another five groups of ten mosquitoes are injected with control dsRNA. Another group of mosquitoes injected with 200 &mu;M HgCl2 in PBS is used as a positive control. These mosquitoes are weighed before injection, and after injection in thirty minute intervals for 3 hours. 
<img src="/files/ftp_upload/3479/3479fig2.jpg" alt="Figure 2" /> 
Figure 2. A simple micro injection device for the RNAi-mediated gene knockdown and in vivo diuresis assay. A. The glass capillary needles used for injection. The gray triangle represents the millimeter increments drawn on the needle to indicate the amount of liquid injected into the mosquito. B. 1 ml syringe used to construct the micro injector. The white triangle represents the needle hub and the black triangle represents the rubber plunger head attached to the plunger in the syringe. C. The tubing used to attach the mouthpiece to the injector. D. 1 ml disposable pipette tip (blue tip) that is used as the mouthpiece of the microinjection device. E. The microinjection device that incorporates A-D parts. <a href="https://www.jove.com/files/ftp_upload/3479/3479fig2large.jpg" target="_blank"> Click here to view larger figure</a>.
<img src="/files/ftp_upload/3479/3479fig3.jpg" alt="Figure 3" /> 
Figure 3. Optimal mosquito injection site. A. Female Aedes aegypti mosquito injected with a glass capillary needle between the large scales on the thorax. The black bar indicates 1 mm for size comparison. B. A drawing of the female mosquito thorax and the white spots represent the white scales in the mosquito exoskeleton. The injection needle should pierce the mosquito between the spots to minimize mortality rate during injection. 
<img src="/files/ftp_upload/3479/3479fig4.jpg" alt="Figure 4" /> 
Figure 4. Effects of temperature on Culex quinquefasciatus and Aedes aegypti diuresis. The diuresis assay was performed with two species of mosquitoes, Aedes aegypti and Culex quinquefasciatus, at different temperatures. The excretion rate during the first hour after injection is given in percent.
<table border="1">
<tbody>
 <tr>
 <td>Group</td>
 <td>TARA 
 (g)</td>
 <td>not injected 
 (g)</td>
 <td>after injection 
 (g)</td>
 <td>1h post injection 
 (g)</td>
 <td>average weight (mg)</td>
 <td>amount injected 
 (&mu;l)</td>
 <td>amount excreted 
 (&mu;l)</td>
 <td>% excreted</td>
 </tr>
 <tr>
 <td>1</td>
 <td>7.5938</td>
 <td>7.6057</td>
 <td>7.6104</td>
 <td>7.6096</td>
 <td>2.38</td>
 <td>0.94</td>
 <td>0.16</td>
 <td>17.0</td>
 </tr>
 <tr>
 <td>2</td>
 <td>7.8252</td>
 <td>7.8349</td>
 <td>7.8415</td>
 <td>7.8403</td>
 <td>1.94</td>
 <td>1.32</td>
 <td>0.24</td>
 <td>18.2</td>
 </tr>
 <tr>
 <td>3</td>
 <td>7.8896</td>
 <td>7.9026</td>
 <td>7.9077</td>
 <td>7.906</td>
 <td>2.6</td>
 <td>1.02</td>
 <td>0.34</td>
 <td>33.3</td>
 </tr>
</tbody>
</table>
Table 1. Aedes aegypti in vivo diuresis assay results. Raw data from the in vivo diuresis assay performed with Aedes aegypti female mosquitoes at 4 &deg;C.

<ol>
	<li>Drake, L. L., 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=The+Aquaporin+gene+family+of+the+yellow+fever+mosquito,+Aedes+aegypti.">The Aquaporin gene family of the yellow fever mosquito, Aedes aegypti.</a> PloS one. 5, e15578 (2010).</li><li>Shepard, A. R., Jacobson, N., Clark, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Importance+of+quantitative+PCR+primer+location+for+short+interfering+RNA+efficacy+determination.">Importance of quantitative PCR primer location for short interfering RNA efficacy determination.</a> Analytical biochemistry. 344, 287-288 (2005).</li><li>Altschul, S. F., 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=Gapped+BLAST+and+PSI-BLAST:+a+new+generation+of+protein+database+search+programs.">Gapped BLAST and PSI-BLAST: a new generation of protein database search programs.</a> Nucleic acids research. 25, 3389-3402 (1997).</li><li>Garver, L., Dimopoulos, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protocol+for+RNAi+Assays+in+Adult+Mosquitoes+(A.+gambiae).">Protocol for RNAi Assays in Adult Mosquitoes (A. gambiae).</a> J. Vis. Exp. (5), e230 (2007).</li><li>Clements, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Volume+1+Development,+Nutrition,+and+Reproduction.">Volume 1 Development, Nutrition, and Reproduction.</a> The Biology of Mosquitoes. 2, (1992).</li><li>Hansen, I. A., Attardo, G. M., Park, J. H., Peng, Q., 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=Target+of+rapamycin-mediated+amino+acid+signaling+in+mosquito+anautogeny.">Target of rapamycin-mediated amino acid signaling in mosquito anautogeny.</a> Proceedings of the National Academy of Sciences of the United States of America. 101, 10626-10631 (2004).</li><li>Hansen, I. A., Attardo, G. M., Roy, S. G., 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=Target+of+rapamycin-dependent+activation+of+S6+kinase+is+a+central+step+in+the+transduction+of+nutritional+signals+during+egg+development+in+a+mosquito.">Target of rapamycin-dependent activation of S6 kinase is a central step in the transduction of nutritional signals during egg development in a mosquito.</a> The Journal of biological chemistry. 280, 20565-20572 (2005).</li><li>Pannabecker, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiology+of+the+Malpighian+Tubule.">Physiology of the Malpighian Tubule.</a> Annual review of entomology. 40, 493-510 (1995).</li><li>Dow, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+insights+into+Malpighian+tubule+function+from+functional+genomics.">New insights into Malpighian tubule function from functional genomics.</a> Comp Biochem Phys A. 150, S135 (2008).</li><li>Dow, J. A. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insights+into+the+Malpighian+tubule+from+functional+genomics.">Insights into the Malpighian tubule from functional genomics.</a> Journal of Experimental Biology. 212, 435-445 (2009).</li><li>Lawson, 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=VectorBase:+a+data+resource+for+invertebrate+vector+genomics.">VectorBase: a data resource for invertebrate vector genomics.</a> Nucleic acids research. 37, 583-587 (2009).</li><li>Beyenbach, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transport+mechanisms+of+diuresis+in+Malpighian+tubules+of+insects.">Transport mechanisms of diuresis in Malpighian tubules of insects.</a> J. Exp. Biol. 206 (Pt 21), 3845-3856 (2003).</li><li>Coast, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous+recording+of+excretory+water+loss+from+Musca+domestica+using+a+flow-through+humidity+meter:+hormonal+control+of+diuresis.">Continuous recording of excretory water loss from Musca domestica using a flow-through humidity meter: hormonal control of diuresis.</a> Journal of insect physiology. 50, 455-468 (2004).</li><li>Kersch, C. N., Pietrantonio, P. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosquito+Aedes+aegypti+(L.)+leucokinin+receptor+is+critical+for+in+vivo+fluid+excretion+post+blood+feeding.">Mosquito Aedes aegypti (L.) leucokinin receptor is critical for in vivo fluid excretion post blood feeding.</a> FEBS letters. 585, 3507-3512 (2011).</li><li>Hays, A. R., 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=A+novel+protein+produced+by+the+vitellogenic+fat+body+and+accumulated+in+mosquito+oocytes.">A novel protein produced by the vitellogenic fat body and accumulated in mosquito oocytes.</a> Development Genes and Evolution. 199, 114-121 (1990).</li></ol>

We have nothing to disclose.

The RNAi protocol used has been developed in the laboratory of Alexander Raikhel at the University of California Riverside6,7 and is similar to a protocol published by Garver and Dimopoulos4. The experimental approach shown in this video protocol can be used to study genes involved in insect diuresis in an in vivo setting. The excretory organs of insects, the Malpighian tubules, have attracted the interest of generations of researchers as a 'simple' model system for diuresis. This organ is ...

<table border="1">
<tbody>
 <tr>
 <td>Name 			of reagent or equipment</td>
 <td>Company</td>
 <td>Catalogue 			number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>MEGAscript 			T7 			High Yield Kit</td>
 <td>Ambion, 			Inc.</td>
 <td>AM1334</td>
 <td></td>
 </tr>
 <tr>
 <td>PBS 			buffer</td>
 <td>Sigma-Aldrich</td>
 <td>P4417</td>
 <td></td>
 </tr>
 <tr>
 <td>Plastic 			tubing</td>
 <td>Local 			vendor</td>
 <td></td>
 <td>PVC</td>
 </tr>
 <tr>
 <td>1 			ml plastic pipette tip</td>
 <td>VWR</td>
 <td>83007-376</td>
 <td>Blue 			tip</td>
 </tr>
 <tr>
 <td>1 			ml syringe</td>
 <td>Becton, 			Dickinson and Company</td>
 <td>309602</td>
 <td></td>
 </tr>
 <tr>
 <td>Scissors </td>
 <td>Local 			vendor</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Metal 			needle</td>
 <td>Carolina 			Biologicals</td>
 <td>654307</td>
 <td>Size 			5</td>
 </tr>
 <tr>
 <td>Fly 			pad</td>
 <td>Genesee 			Scientific</td>
 <td>789060</td>
 <td></td>
 </tr>
 <tr>
 <td>Battery-powered 			aspirator w/ collection vial</td>
 <td>UPMA 			Labs</td>
 <td>IPMM 			2000</td>
 <td></td>
 </tr>
 <tr>
 <td>Fine 			tip forceps</td>
 <td>World 			Precision Instruments</td>
 <td>14095</td>
 <td></td>
 </tr>
 <tr>
 <td>Glass 			capillary needles</td>
 <td>World 			Precision Instruments</td>
 <td>1B200-6</td>
 <td></td>
 </tr>
 <tr>
 <td>Stereo 			dissection microscope </td>
 <td>Leica 			Microsystems</td>
 <td>S6D</td>
 <td></td>
 </tr>
 <tr>
 <td>Analytical 			precision balance</td>
 <td>Mettler 			Toledo</td>
 <td>AB54S</td>
 <td></td>
 </tr>
 <tr>
 <td>Sucrose</td>
 <td>Sigma-Aldrich</td>
 <td>84097</td>
 <td></td>
 </tr>
 <tr>
 <td>One 			pint waxed lined cardboard cups</td>
 <td>Local 			vendor</td>
 <td></td>
 <td>Manufactured 			soup cups</td>
 </tr>
 <tr>
 <td>Mesh 			net</td>
 <td>Local 			vendor</td>
 <td></td>
 <td>plastic 			fly gauze</td>
 </tr>
 </tbody>
</table>

rnai-mediated gene knockdown and in vivo diuresis assay in adult female aedes aegypti mosquitoes

This video protocol demonstrates an effective technique to knockdown a particular gene in an insect and conduct a novel bioassay to measure excretion rate. This method can be used to obtain a better understanding of the process of diuresis in insects and is especially useful in the study of diuresis in blood-feeding arthropods that are able to take up huge amounts of liquid in a single blood meal. 
This RNAi-mediated gene knockdown combined with an in vivo diuresis assay was developed by the Hansen lab to study the effects of RNAi-mediated knockdown of aquaporin genes on Aedes aegypti mosquito diuresis1. 
The protocol is setup in two parts: the first demonstration illustrates how to construct a simple mosquito injection device and how to prepare and inject dsRNA into the thorax of mosquitoes for RNAi-mediated gene knockdown. The second demonstration illustrates how to determine excretion rates in mosquitoes using an in vivo bioassay.

Watch this Scientific Journal Video about RNAi-mediated Gene Knockdown and In Vivo Diuresis Assay in Adult Female Aedes aegypti Mosquitoes at JoVE.com

RNAi-mediated Gene Knockdown and In Vivo Diuresis Assay in Adult Female Aedes aegypti Mosquitoes

In this protocol we combine RNAi-mediated gene silencing with an in vivo diuresis assay to study the effects knockdown of genes of interest has on mosquito fluid excretion.

RNAi-mediated Gene Knockdown and In Vivo Diuresis Assay in Adult Female Aedes aegypti Mosquitoes

This video protocol demonstrates an effective technique to knockdown a particular gene in an insect and conduct a novel bioassay to measure excretion ...

rnai-mediated-gene-knockdown-vivo-diuresis-assay-adult-female-aedes

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JoVE Journal

Biology

13.5K Views.  New Mexico State University. In this protocol we combine RNAi-mediated gene silencing with an in vivo diuresis assay to study the effects knockdown of genes of interest has on mosquito fluid excretion.

Video: RNAi-mediated Gene Knockdown and In Vivo Diuresis Assay in Adult Female Aedes aegypti Mosquitoes

Injection of dsRNA into Female A. aegypti Mosquitos

Reverse genetic approaches have proven extremely useful for determining  which genes underly resistance to vector pathogens in mosquitoes.  This video protocol illustrates a method used by the James lab to inject dsRNA into female A. aegypti mosquitoes, which harbor the dengue virus.  The technique for calibrating injection needles, manipulating the injection setup, and injecting dsRNA into the thorax is illustrated.

Reverse genetic approaches have proven extremely useful for determining which genes underly resistance to vector pathogens in mosquitoes. This video protocol illustrates a method used by the James lab to inject dsRNA into female A. aegypti mosquitoes, which harbor the dengue virus. The technique for calibrating injection needles, manipulating the injection setup, and injecting dsRNA into the thorax is illustrated.

Reverse genetic approaches have proven extremely useful for determining  which genes underly resistance to vector pathogens in mosquitoes.  This video ...

Microinjection of A. aegypti Embryos to Obtain Transgenic Mosquitoes

In this video, Nijole Jasinskiene demonstrates the methodology employed to generate transgenic Aedes aegypti mosquitoes, which are vectors for dengue fever.  The techniques for correctly preparing microinjection needles, dessicating embryos, and performing microinjection are demonstrated.

In this video, Nijole Jasinskiene demonstrates the methodology employed to generate transgenic Aedes aegypti mosquitoes, which are vectors for dengue fever. The techniques for correctly preparing microinjection needles, dessicating embryos, and performing microinjection are demonstrated.

In this video, Nijole Jasinskiene demonstrates the methodology employed to generate transgenic Aedes aegypti mosquitoes, which are vectors for dengue ...

Protocol for Dengue Infections in Mosquitoes (A. aegypti) and Infection Phenotype Determination

The purpose of this procedure is to infect the Aedes mosquito with dengue virus in a laboratory condition and examine the infection level and dynamic of the virus in the mosquito tissues. This protocol is routinely used for studying mosquito-virus interactions, especially for identification of novel host factors that are able to determine vector competence. The entire experiment must be conducted in a BSL2 laboratory. Similar to Plasmodium falciparum infections, proper attire including gloves and lab coat must be worn at all times. After the experiment, all the materials that came in contact with the virus need to be treated with 75% ethanol and bleached before proceeding with normal washing. All other materials need to be autoclaved before discarding them.

Protocol for Dengue Infections in Mosquitoes A. aegypti and Infection Phenotype Determination

Once a gene is identified as potentially refractory for the dengue virus, it must be evaluated for it's role in preventing viral infections within the mosquito. This protocol illustrates how the extent of dengue infections of mosquitoes can be assayed. The techniques for growing up the virus in culture, membrane feeding mosquitoes human blood, and assaying viral titers in the mosquito midgut are demonstrated.

The purpose of this procedure is to infect the Aedes mosquito with dengue virus in a laboratory condition and examine the infection level and dynamic of ...

Dissection of Midgut and Salivary Glands from Ae. aegypti Mosquitoes

The mosquito midgut and salivary glands are key entry and exit points for pathogens such as Plasmodium parasites and Dengue viruses. This video protocol demonstrates dissection techniques for removal of the midgut and salivary glands from Aedes aegypti mosquitoes. 



The mosquito midgut and salivary glands are key entry and exit points for vector pathogens like Plasmodium falciparum and the dengue virus. This video demonstrates the dissection techniques for removing the midgut and salivary glands from Aedes aegypti mosquitoes.

The mosquito midgut and salivary glands are key entry and exit points for pathogens such as Plasmodium parasites and Dengue viruses. This video protocol ...

RNAi Mediated Gene Knockdown and Transgenesis by Microinjection in the Necromenic Nematode Pristionchus pacificus

Although it is increasingly affordable for emerging model organisms to obtain completely sequenced genomes, further in-depth gene function and expression analyses by RNA interference and stable transgenesis remain limited in many species due to the particular anatomy and molecular cellular biology of the organism. For example, outside of the crown group Caenorhabditis that includes Caenorhabditis elegans3, stably transmitted transgenic lines in non-Caenorhabditis species have not been reported in this specious phylum (Nematoda), with the exception of Strongyloides stercoralis4 and Pristionchus pacificus5. To facilitate the expanding role of P. pacificus in the study of development, evolution, and behavior6-7, we describe here the current methods to use microinjection for making transgenic animals and gene knock down by RNAi. Like the gonads of C. elegans and most other nematodes, the gonads of P. pacificus is syncitial and capable of incorporating DNA and RNA into the oocytes when delivered by direct microinjection. Unlike C. elegans however, stable transgene inheritance and somatic expression in P. pacificus requires the addition of self genomic DNA digested with endonucleases complementary to the ends of target transgenes and coinjection markers5. The addition of carrier genomic DNA is similar to the requirement for transgene expression in Strongyloides stercoralis4 and in the germ cells of C. elegans. However, it is not clear if the specific requirement for the animals' own genomic DNA is because P. pacificus soma is very efficient at silencing non-complex multi-copy genes or that extrachromosomal arrays in P. pacificus require genomic sequences for proper kinetochore assembly during mitosis. The ventral migration of the two-armed (didelphic) gonads in hermaphrodites further complicates the ability to inject both gonads in individual worms8. We also demonstrate the use of microinjection to knockdown a dominant mutant (roller,tu92) by injecting double-stranded RNA (dsRNA) into the gonads to obtain non-rolling F1 progeny. Unlike C. elegans, but like most other nematodes, P. pacificus PS312 is not receptive to systemic RNAi via feeding and soaking and therefore dsRNA must be administered by microinjection into the syncitial gonads. In this current study, we hope to describe the microinjection process needed to transform a Ppa-egl-4 promoter::GFP fusion reporter and knockdown a dominant roller prl-1 (tu92) mutant in a visually informative protocol.

RNAi Mediated Gene Knockdown and Transgenesis by Microinjection in the Necromenic Nematode Pristionchus pacificus

In model organisms, transgenesis can manipulate gene functions while RNAi can knockdown specific mRNA transcripts 1-2. This protocol aims to illustrate the techniques needed to introduce stably transmitted DNA and transient double stranded RNA into the necromenic nematode Pristionchus pacificus for studies in evolutionary, developmental, and behavioral biology.

Although it is increasingly affordable for emerging model organisms to obtain completely sequenced genomes, further in-depth gene function and expression ...

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the messagefor review see 1. However, it's now widely accepted that synonymous codon usage is the primary cause of non-uniform translational elongation rates1. Synonymous codons are not used with identical frequency. A bias exists in the use of synonymous codons with some codons used more frequently than others2. Codon bias is organism as well as tissue specific2,3. Moreover, frequency of codon usage is directly proportional to the concentrations of cognate tRNAs4. Thus, a frequently used codon will have higher multitude of corresponding tRNAs, which further implies that a frequent codon will be translated faster than an infrequent one. Thus, regions on mRNA enriched in rare codons (potential pause sites) will as a rule slow down ribosome movement on the message and cause accumulation of nascent peptides of the respective sizes5-8. These pause sites can have functional impact on the protein expression, mRNA stability and protein foldingfor review see 9. Indeed, it was shown that alleviation of such pause sites can alter ribosome movement on mRNA and subsequently may affect the efficiency of co-translational (in vivo) protein folding1,7,10,11. To understand the process of protein folding in vivo, in the cell, that is ultimately coupled to the process of protein synthesis it is essential to gain comprehensive insights into the impact of codon usage/tRNA content on the movement of ribosomes along mRNA during translational elongation.
Here we describe a simple technique that can be used to locate major translation pause sites for a given mRNA translated in various cell-free systems6-8. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA. The rationale is that at low-frequency codons, the increase in the residence time of the ribosomes results in increased amounts of nascent peptides of the corresponding sizes. In vitro transcribed mRNA is used for in vitro translational reactions in the presence of radioactively labeled amino acids to allow the detection of the nascent chains. In order to isolate ribosome bound nascent polypeptide complexes the translation reaction is layered on top of 30% glycerol solution followed by centrifugation. Nascent polypeptides in polysomal pellet are further treated with ribonuclease A and resolved by SDS PAGE. This technique can be potentially used for any protein and allows analysis of ribosome movement along mRNA and the detection of the major pause sites. Additionally, this protocol can be adapted to study factors and conditions that can alter ribosome movement and thus potentially can also alter the function/conformation of the protein.

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

A technique to identify translational pause sites on mRNA is described. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA, followed by the size analysis of the nascent chains using a denaturing gel electrophoresis.

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the ...

Using SecM Arrest Sequence as a Tool to Isolate Ribosome Bound Polypeptides

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway that polypeptide chain follows during co-translational folding to achieve its functional form is still an enigma. In order to understand this process and to determine the exact conformation of the co-translational folding intermediates, it is essential to develop techniques that allow the isolation of RNCs carrying nascent chains of predetermined sizes to allow their further structural analysis.
SecM (secretion monitor) is a 170 amino acid E. coli protein that regulates expression of the downstream SecA (secretion driving) ATPase in the secM-secA operon6. Nakatogawa and Ito originally found that a 17 amino acid long sequence (150-FSTPVWISQAQGIRAGP-166) in the C-terminal region of the SecM protein is sufficient and necessary to cause stalling of SecM elongation at Gly165, thereby producing peptidyl-glycyl-tRNA stably bound to the ribosomal P-site7-9. More importantly, it was found that this 17 amino acid long sequence can be fused to the C-terminus of virtually any full-length and/or truncated protein thus allowing the production of RNCs carrying nascent chains of predetermined sizes7. Thus, when fused or inserted into the target protein, SecM stalling sequence produces arrest of the polypeptide chain elongation and generates stable RNCs both in vivo in E. coli cells and in vitro in a cell-free system. Sucrose gradient centrifugation is further utilized to isolate RNCs.
The isolated RNCs can be used to analyze structural and functional features of the co-translational folding intermediates. Recently, this technique has been successfully used to gain insights into the structure of several ribosome bound nascent chains10,11. Here we describe the isolation of bovine Gamma-B Crystallin RNCs fused to SecM and generated in an in vitro translation system.

We describe here a technique that is now routinely used to isolate stably bound ribosome nascent chain complexes (RNCs). This technique takes advantage of the discovery that a 17 amino acid long SecM "arrest sequence" can halt translation elongation in a prokaryotic (E. coli) system, when inserted into (or fused to the C-terminus) of virtually any protein.

Extensive research has provided ample evidences suggesting that protein folding in the cell is a co-translational process1-5. However, the exact pathway ...

In Vivo SiRNA Transfection and Gene Knockdown in Spinal Cord via Rapid Noninvasive Lumbar Intrathecal Injections in Mice

This report describes a step-by-step guide to the technique of acute intrathecal needle injections in a noninvasive manner, i.e. independent of catheter implantation. The technical limitation of this surgical technique lies in the finesse of the hands. The injection is rapid, especially for a trained experimenter, and since tissue disruption with this technique is minimal, repeated injections are possible; moreover immune reaction to foreign tools (e.g. catheter) does not occur, thereby giving a better and more specific read out of spinal cord modulation. Since the application of the substance is largely limited to the target region of the spinal cord, drugs do not need to be applied in large dosages, and more importantly unwanted effects on other tissue, as observed with a systemic delivery, could be circumvented1,2. Moreover, we combine this technique with in vivo transfection of nucleic acid with the help of polyethylenimine (PEI) reagent3, which provides tremendous versatility for studying spinal functions via delivery of pharmacological agents as well as gene, RNA, and protein modulators.

In Vivo SiRNA Transfection and Gene Knockdown in Spinal Cord via Rapid Noninvasive Lumbar Intrathecal Injections in Mice

This report describes a simple and rapid technique of intrathecal needle puncture for a localized transfection of siRNA in the lumbar spinal cord in mouse under short lasting light anesthesia.

This report describes a step-by-step guide to the technique of acute intrathecal needle injections in a noninvasive manner, i.e. independent of catheter ...

Fat Body Organ Culture System in Aedes Aegypti, a Vector of Zika Virus

The insect fat body plays a central role in insect metabolism and nutrient storage, mirroring functions of the liver and fat tissue in vertebrates. Insect fat body tissue is usually distributed throughout the insect body. However, it is often concentrated in the abdomen and attached to the abdominal body wall.
The mosquito fat body is the sole source of yolk proteins, which are critical for egg production. Therefore, the in vitro culture of mosquito fat body tissues represents an important system for the study of mosquito physiology, metabolism, and, ultimately, egg production. The fat body culture process begins with the preparation of solutions and reagents, including amino acid stock solutions, Aedes physiological saline salt stock solution (APS), calcium stock solution, and fat body culture medium. The process continues with fat body dissection, followed by an experimental treatment. After treatment, a variety of different analyses can be performed, including RNA sequencing (RNA-Seq), qPCR, Western blots, proteomics, and metabolomics.
In our example experiment, we demonstrate the protocol through the excision and culture of fat bodies from the yellow fever mosquito, Aedes aegypti, a principal vector of arboviruses including dengue, chikungunya, and Zika. RNA from fat bodies cultured under a physiological condition known to upregulate yolk proteins versus the control were subject to RNA-Seq analysis to demonstrate the potential utility of this procedure for investigations of gene expression.

Fat Body Organ Culture System in Aedes Aegypti, a Vector of Zika Virus

The fat body is the central metabolic organ in insects. We present a live organ culture system that enables the user to study the responses of isolated fat body tissue to various stimuli.

The insect fat body plays a central role in insect metabolism and nutrient storage, mirroring functions of the liver and fat tissue in vertebrates. Insect ...

Maintaining Aedes aegypti Mosquitoes Infected with Wolbachia

Aedes aegypti mosquitoes experimentally infected with Wolbachia are being utilized in programs to control the spread of arboviruses such as dengue, chikungunya and Zika. Wolbachia-infected mosquitoes can be released into the field to either reduce population sizes through incompatible matings or to transform populations with mosquitoes that are refractory to virus transmission. For these strategies to succeed, the mosquitoes released into the field from the laboratory must be competitive with native mosquitoes. However, maintaining mosquitoes in the laboratory can result in inbreeding, genetic drift and laboratory adaptation which can reduce their fitness in the field and may confound the results of experiments. To test the suitability of different Wolbachia infections for deployment in the field, it is necessary to maintain mosquitoes in a controlled laboratory environment across multiple generations. We describe a simple protocol for maintaining Ae. aegypti mosquitoes in the laboratory, which is suitable for both Wolbachia-infected and wild-type mosquitoes. The methods minimize laboratory adaptation and implement outcrossing to increase the relevance of experiments to field mosquitoes. Additionally, colonies are maintained under optimal conditions to maximize their fitness for open field releases.

Maintaining Aedes aegypti Mosquitoes Infected with Wolbachia

Aedes aegypti mosquitoes infected with Wolbachia are being released into natural populations to suppress the transmission of arboviruses. We describe methods to rear Ae. aegypti with Wolbachia infections in the laboratory for experiments and field release, taking precautions to minimize laboratory adaptation and selection.

Aedes aegypti mosquitoes experimentally infected with Wolbachia are being utilized in programs to control the spread of arboviruses such as dengue, ...