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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The authors have nothing to disclose.

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.

<table border="0" cellpadding="0" cellspacing="0" width="668">
	<tbody>
		<tr height="21">
			<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...

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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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8.4K vistas.  Virginia Tech. 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. 