Name: toxicological assays for testing effects of an epigenetic drug on development, fecundity and survivorship of malaria mosquitoes
Uploaded: 2015-01-16T13:00:00
Description: Watch this Scientific Journal Video about Toxicological Assays for Testing Effects of an Epigenetic Drug on Development, Fecundity and Survivorship of Malaria Mosquitoes at JoVE.com

We thank Victor Marquez for providing DZNep.HCl and Scotty Bolling for manufacturing the bloodfeeders. The Mopti and SUA2La strains of An. gambiae were obtained from the Malaria Research and Reference Reagent Resource Center (MR4). This work was supported by the Fralin Life Science Institute and the grant from National Institutes of Health 1R21AI094289 to Igor V. Sharakhov.

NOTE: The three parts of the protocol describe the aqueous exposure of the DZNep drug to larval mosquitoes, a blood-based exposure of DZNep to adult females to study its effect of fecundity, and SAH hydrolase inhibition by DZNep measured using a simple colorimetric technique. A schematic representation of these assays is shown in Figure 1.
1. Immature Mosquito Development and Survivorship Assays
NOTE: This section explains the use of a water-soluble d...

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There are several steps vital to the successful application of this protocol. For the larval assay, care should be taken to correctly label and replicate each test concentration. Randomizing test samples and adding the designated amount of drug to respective test wells is an important part of this experimental set up. Before adding 2nd instar mosquito larvae to a 96-well microplate, each larva can be put on a paper towel for 2-3 sec to remove excess water. To prevent desiccation, larvae must be immediately tra...

Malaria is responsible for the highest number of insect-related deaths in the world. An estimated 219 million cases occur annually worldwide, resulting in approximately 660,000 deaths, primarily in Africa 1. Despite concerted efforts, malaria programs face several challenges. While insecticidal treated bednets and indoor residual spraying form key components of the program, resistance to insecticides in local populations impede these efforts 2. The rapid increase in insecticide resistant mosquito populations is largely attributed to the ability of the malaria mosquitoes to adapt quickly to changes in their environment and exploit different niches 3,4,5. To overcome the existing mechanisms of insecticide resistance, the exploration of novel insecticide targets and next generation compounds is warranted. A simple, step-by-step protocol for determining the efficacy of experimental insecticides on the various life stages of malaria mosquitoes would significantly enhance these efforts.
Pharmacological studies of drug effects on cell lines and animal models have established the use of epigenetic drugs as a useful tool for modulating the genetics and physiology of cells and organisms. DNA methylation and histone modification are two epigenetic mechanisms that affect gene expression in multicellular organisms without changing the underlying DNA sequence 6. Post translational modifications such as methylation play a crucial role in maintaining cellular integrity and gene expression, and may affect several fundamental processes 7,8,9. Research in some insect species have highlighted the importance of epigenetics in processes involving oogenesis and stem cell maintenance 10, as well as dosage compensation 11 . However, such aspects in disease vectors are yet to be explored. Using a compound to modulate this system in mosquitoes may provide us with insights into the novel insecticide target pathways. 3-Deazaneplanocin A (DZNep) is a known histone methylation inhibitor, which impact on various types of cancers have been studied 12,13,14,15,16. DZNep is a stable water-soluble epigenetic drug that indirectly inhibits histone lysine N-methyltransferase (EZH2), a component of the polycomb repressive complex 2 (PRC2) in mammalian cells. PRC2 plays an important role in regulating the growth of stem cells in multicellular organisms, and histone methylation is a key aspect of the PRC2 mediated gene silencing. In immunocompromised mice, cells pre-treated with DZNep have been shown to be less tumorigenic 17. This drug is becoming used for studying other diseases, such as non-alcoholic fatty liver disease, in which EZH2 is implicated 18. DZNep is an established S-adenosylhomocysteine (SAH) hydrolase inhibitor 19,20. The inhibition of SAH hydrolase results in an accumulation of SAH and, in turn, leads to the inhibition of methyltransferase activity by limiting available methyl donor groups. SAH is an amino acid derivative utilized by many organisms, including insects, in their metabolic pathways. A recent study has shown that DZNep in low doses may affect diapause and delay development in insects 21.
Here, a robust protocol to investigate the effects of a water-soluble compound on various life stages of mosquitoes is developed. The three parts of this protocol include instructions for examining the effects of a water-soluble compound on immature mosquitoes, adult blood-feeding females, and enzyme activity of adult male and female mosquitoes. First, DZNep is dissolved in water to study immature mosquito development and survival. This is performed at two concentrations to compare any differences arising from 10-fold increase in drug exposure. To explore the effect of drug on adult female mosquitoes, DZNep is added to defibrillated sheep blood and fed the blood artificially to females. Subsequently, the outcome of the drug on fecundity is examined. Finally, an enzyme activity assay is performed using 5,5&#39;-dithiobis-(2-nitrobenzoic acid) (DTNB) as an indicator to determine the effect of DZNep on SAH hydrolase inhibition in adult male and female mosquitoes. While this protocol is developed with a malaria mosquito, Anopheles gambiae, it can be easily adapted to studying the effects of compounds of interest on any species of mosquito or other insects. The techniques detailed in this protocol may not be efficiently applied to a drug with limited or no solubility in water or aqueous media.

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			<td height="21" style="height:21px;width:219px;">Name of the Reagent/Equipment&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
			<td style="width:192px;">Company</td>
			<td style="width:133px;">Catalgue Number</td>
			<td style="width:125px;">Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">96-well microplate</td>
			<td>Fisher Scientific</td>
			<td>12565561</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cell culture plate</td>
			<td>CytoOne</td>
			<td>CC7682-7506</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Centrifuge</td>
			<td>Sorvall Fresco</td>
			<td>76003758</td>
			<td>A different centrifuge can be used</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Colored tape rolls</td>
			<td>Fisher</td>
			<td>S68134</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dissection microscope</td>
			<td>Olympus</td>
			<td>SZ</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DTNB</td>
			<td>Sigma Aldrich</td>
			<td>D8130</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DZNep.HCl</td>
			<td>Sigma Aldrich</td>
			<td>SMLO305</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Egg dish cups</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Filter papers</td>
			<td>Fisher</td>
			<td>09-795E</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glass feeders</td>
			<td>Virginia Tech</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glass tissue homogenizer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Heating element</td>
			<td>Fisher Scientific</td>
			<td style="width:133px;">NC0520091</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Incubator</td>
			<td>Percival scientific</td>
			<td>I36VLC8</td>
			<td>A different incubator can be used</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microcentrifuge tube, &#160;2 ml</td>
			<td>Axygen</td>
			<td>22-283</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microcentrifuge tube, 1.5 ml</td>
			<td>Axygen</td>
			<td>MCT-150-C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micropipette</td>
			<td>Eppendorf</td>
			<td>4910 000.069</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Na2HPO4</td>
			<td>Fisher Scientific</td>
			<td>M-3154</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NaH2PO4</td>
			<td>Fisher Scientific</td>
			<td>M-8643</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">pH meter&#160;</td>
			<td>Mettler Toledo 7easy</td>
			<td>S20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plate reader</td>
			<td>Spectramax</td>
			<td>M2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SAH</td>
			<td>Sigma Aldrich</td>
			<td>A9384</td>
			<td>store at -20C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triton X-100</td>
			<td>Sigma Aldrich</td>
			<td>T8787</td>
			<td></td>
		</tr>
	</tbody>
</table>

toxicological assays for testing effects of an epigenetic drug on development, fecundity and survivorship of malaria mosquitoes

Insecticidal resistance poses a major problem for malaria control programs. Mosquitoes adapt to a wide range of changes in the environment quickly, making malaria control an omnipresent problem in tropical countries. The emergence of insecticide resistant populations warrants the exploration of novel drug target pathways and compounds for vector mosquito control. Epigenetic drugs are well established in cancer research, however not much is known about their effects on insects. This study provides a simple protocol for examining the toxicological effects of 3-Deazaneplanocin A (DZNep), an experimental epigenetic drug for cancer therapy, on the malaria vector, Anopheles gambiae. A concentration-dependent increase in mortality and decrease in size was observed in immature mosquitoes exposed to DZNep, whereas the compound reduced the fecundity of adult mosquitoes relative to control treatments. In addition, there was a drug-dependent decrease in S-adenosylhomocysteine (SAH) hydrolase activity in mosquitoes following exposure to DZNep relative to control treatments. These protocols provide the researcher with a simple, step-by-step procedure to assess multiple toxicological endpoints for an experimental drug and, in turn, demonstrate a unique multi-prong approach for exploring the toxicological effects of water-soluble epigenetic drugs or compounds of interest against vector mosquitoes and other insects.

Figure 1 is a schematic representation of the assays; it describes the various steps of the procedure listed in this article. As the protocol is based on different life stages of mosquitoes, there is no particular sequence to be followed for the experiments detailed here. The user may choose to conduct one or more assays at the same time, depending upon sample availability.

Figure 2 demonstrates the plate set up for the immature mosquito development an...

Watch this Scientific Journal Video about Toxicological Assays for Testing Effects of an Epigenetic Drug on Development, Fecundity and Survivorship of Malaria Mosquitoes at JoVE.com

Toxicological Assays for Testing Effects of an Epigenetic Drug on Development, Fecundity and Survivorship of Malaria Mosquitoes

A protocol is developed to examine the effects of an epigenetic drug DZNep on the development, fecundity and survivorship of mosquitoes. Here we describe procedures for the aqueous exposure of DZNep to immature mosquitoes and a blood-based exposure of DZNep to adult mosquitoes in addition to measuring SAH hydrolase inhibition.

Insecticidal resistance poses a major problem for malaria control programs. Mosquitoes adapt to a wide range of changes in the environment quickly, making ...

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Biology

Injection of An. stephensi Embryos to Generate Malaria-resistant Mosquitoes

The introduction of exogenous genes into the genomes of mosquitoes requires microinjection techniques tailored to the specific species of interest. This video protocol demonstrates a method used by the James laboratory to microinject DNA constructs into Anopheles stephensi embryos for the generation of transformed mosquitoes. Techniques for preparing microinjection needles, collecting and preparing embryos and performing the microinjection are illustrated.

Anopheles stephensi mosquitoes are vectors for malaria inhabiting India and throughout Asia. This video demonstrates the technique for performing microinjections of this species with transgenes that will confer resistance to the malaria to the mosquito. Much of the methodology demonstrated in this video is applicable to microinjection techniques of other mosquito species.

The introduction of exogenous genes into the genomes of mosquitoes requires microinjection techniques tailored to the specific species of interest. This ...

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 ...

Protocol for Plasmodium falciparum Infections in Mosquitoes and Infection Phenotype Determination

Once a gene is identified as potentially refractory for malaria, it must be evaluated for its role in preventing Plasmodium infections within the mosquito.    This protocol illustrates how the extent of plasmodium infections of mosquitoes can be assayed.  The techniques for preparing the gametocyte culture, membrane feeding mosquitoes human blood, and assaying viral titers in the mosquito midgut are demonstrated.

Once a gene is identified as potentially refractory for malaria, it must be evaluated for its role in preventing Plasmodium infections within the mosquito. This protocol illustrates how the extent of plasmodium infections of mosquitoes can be assayed. The techniques for preparing the gametocyte culture, membrane feeding mosquitoes human blood, and assaying viral titers in the mosquito midgut are demonstrated.

Once a gene is identified as potentially refractory for malaria, it must be evaluated for its role in preventing Plasmodium infections within the ...

Protocol for RNAi Assays in Adult Mosquitoes (A. gambiae)

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 Dimopoulos lab to inject dsRNA into Anopheles gambiae mosquitoes, which harbor the malaria parasite.  The technique manipulating the injection setup and injecting dsRNA into the thorax is illustrated.

Protocol for RNAi Assays in Adult Mosquitoes A. gambiae

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 Dimopoulos lab to inject dsRNA into Anopheles gambiae mosquitoes, which harbor the malaria parasite. The technique 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 ...

Preventing the Spread of Malaria and Dengue Fever Using Genetically Modified Mosquitoes

In this candid interview, Anthony A. James explains how mosquito genetics can be exploited to control malaria and dengue transmission.   Population replacement strategy, the idea that transgenic mosquitoes can be released into the wild to control disease transmission, is introduced, as well as the concept of genetic drive and the design criterion for an effective genetic drive system. The ethical considerations of releasing genetically-modified organisms into the wild are also discussed.

In this candid interview, Anthony A. James explains how mosquito genetics can be exploited to control malaria and dengue transmission. Population replacement strategy, the idea that transgenic mosquitoes can be released into the wild to control disease transmission, is introduced as well as the concept of genetic drive and the design criterion for an effective genetic drive system. The ethical considerations of releasing genetically-modified organisms into the wild are also discussed.

In this candid interview, Anthony A. James explains how mosquito genetics can be exploited to control malaria and dengue transmission.   Population ...

Building a Better Mosquito: Identifying the Genes Enabling Malaria and Dengue Fever Resistance in A. gambiae and A. aegypti Mosquitoes

In this interview, George Dimopoulos focuses on the physiological mechanisms used by mosquitoes to combat Plasmodium falciparum and dengue virus infections.   Explanation is given for how key refractory genes, those genes conferring resistance to vector pathogens, are identified in the mosquito and how this knowledge can be used to generate transgenic mosquitoes that are unable to carry the malaria parasite or dengue virus.

In this interview, George Dimopoulos focuses on the physiological mechanisms used by mosquitoes to combat Plasmodium falciparum and dengue virus infections. Explanation is given for how key refractory genes, those genes conferring resistance to vector pathogens, are identified in the mosquito and how this knowledge can be used to generate transgenic mosquitoes that are unable to carry the malaria parasite or dengue virus.

In this interview, George Dimopoulos focuses on the physiological mechanisms used by mosquitoes to combat Plasmodium falciparum and dengue virus ...

Generation of Myospheres From hESCs by Epigenetic Reprogramming

Generation of a homogeneous and abundant population of skeletal muscle cells from human embryonic stem cells (hESCs) is a requirement for cell-based therapies and for a "disease in a dish" model of human neuromuscular diseases. Major hurdles, such as low abundance and heterogeneity of the population of interest, as well as a lack of protocols for the formation of three-dimensional contractile structures, have limited the applications of stem cells for neuromuscular disorders. We have designed a protocol that overcomes these limits by ectopic introduction of defined factors in hESCs - the muscle determination factor MyoD and SWI/SNF chromatin remodeling complex component BAF60C - that are able to reprogram hESCs into skeletal muscle cells. Here we describe the protocol established to generate hESC-derived myoblasts and promote their clustering into tridimensional miniaturized structures (myospheres) that functionally mimic miniaturized skeletal muscles7.

Here, we describe a protocol based on epigenetic reprogramming of human embryonic stem cells (hESCs) toward generating a homogeneous population of skeletal muscle progenitors that under permissive culture conditions form three-dimensional clusters of contractile myofibers (myospheres), which recapitulate biological features of human skeletal muscles.

Generation of a homogeneous and abundant population of skeletal muscle cells from human embryonic stem cells (hESCs) is a requirement for cell-based ...

A Multi-detection Assay for Malaria Transmitting Mosquitoes

The Anopheles gambiae species complex includes the major malaria transmitting mosquitoes in Africa. Because these species are of such medical importance, several traits are typically characterized using molecular assays to aid in epidemiological studies. These traits include species identification, insecticide resistance, parasite infection status, and host preference. Since populations of the Anopheles gambiae complex are morphologically indistinguishable, a polymerase chain reaction (PCR) is traditionally used to identify species. Once the species is known, several downstream assays are routinely performed to elucidate further characteristics. For instance, mutations known as KDR in a para gene confer resistance against DDT and pyrethroid insecticides. Additionally, enzyme-linked immunosorbent assays (ELISAs) or Plasmodium parasite DNA detection PCR assays are used to detect parasites present in mosquito tissues. Lastly, a combination of PCR and restriction enzyme digests can be used to elucidate host preference (e.g., human vs. animal blood) by screening the mosquito bloodmeal for host-specific DNA. We have developed a multi-detection assay (MDA) that combines all of the aforementioned assays into a single multiplex reaction genotyping 33SNPs for 96 or 384 samples at a time. Because the MDA includes multiple markers for species, Plasmodium detection, and host blood identification, the likelihood of generating false positives or negatives is greatly reduced from previous assays that include only one marker per trait. This robust and simple assay can detect these key mosquito traits cost-effectively and in a fraction of the time of existing assays.

Malaria transmitting mosquitoes have a number of epidemiologically important characteristics that can only be detected using molecular techniques. Utilizing a MALDI-TOF based SNP genotyping platform, we developed an assay for simultaneously detecting multiple key traits (species, insecticide resistance, parasite infection and host choice) of malaria vectors.

The Anopheles gambiae species complex includes the major malaria transmitting mosquitoes in Africa. Because these species are of such medical importance, ...

Protocols for Testing the Toxicity of Novel Insecticidal Chemistries to Mosquitoes

New classes of insecticides with novel modes of action are needed to control insecticide resistant populations of mosquitoes that transmit diseases such as Zika, dengue and malaria. Assays for rapid, high-throughput analyses of unformulated novel chemistries against mosquito larvae and adults are presented. We describe protocols for single point-dose and dose response assays to evaluate the toxicity of small molecule chemistries to the Aedes aegypti vector of Zika, dengue and yellow fever,&#160;the malaria vector, Anopheles gambiae and the northern house mosquito, Culex quinquefasciatus, on contact and via ingestion. As an example, we evaluated the toxicity of amitriptyline, a small molecule antagonist of G protein-coupled receptors, via larval, adult topical and adult blood-feeding assay. The protocols provide a starting point to investigate insecticide potential. Results are discussed in the context of additional experiments to explore product applications and mechanisms for delivery.

Protocols are described for assessing the toxicity of chemistries to immature and adult mosquitoes for development as new classes of larvicides, adulticides and endectocides. The protocols enable high-throughput testing of multiple chemistries at single-point dose and subsequent evaluation via dose response assay to determine toxicity on contact or via ingestion.

New classes of insecticides with novel modes of action are needed to control insecticide resistant populations of mosquitoes that transmit diseases such ...

Medium-throughput Screening Assays for Assessment of Effects on Ca2+-Signaling and Acrosome Reaction in Human Sperm

Ca2+-signaling is essential to normal sperm cell function and male fertility. Similarly, the acrosome reaction is vital for the ability of a human sperm cell to penetrate the zona pellucida and fertilize the egg. It is therefore of great interest to test compounds (e.g., environmental chemicals or drug candidates) for their effect on Ca2+-signaling and acrosome reaction in human sperm either to examine the potential adverse effects on human sperm cell function or to investigate a possible role as a contraceptive. Here, two medium-throughput assays are described: 1) a fluorescence-based assay for assessment of effects on Ca2+-signaling in human sperm, and 2) an image cytometric assay for assessment of acrosome reaction in human sperm. These assays can be used to screen a large number of compounds for effects on Ca2+-signaling and acrosome reaction in human sperm. Furthermore, the assays can be used to generate highly specific dose-response curves of individual compounds, determine potential additivity/synergism for two or more compounds, and to study the pharmacological mode of action through competitive inhibition experiments with CatSper inhibitors.

Medium-throughput Screening Assays for Assessment of Effects on Ca2+-Signaling and Acrosome Reaction in Human Sperm

Here, two medium-throughput assays for assessment of effects on Ca2+-signaling and acrosome reaction in human sperm are described. These assays can be used to quickly and easily screen large amounts of compounds for effects on Ca2+-signaling and acrosome reaction in human sperm.

Ca2+-signaling is essential to normal sperm cell function and male fertility. Similarly, the acrosome reaction is vital for the ability of a human sperm ...