Name: a screening method for identification of heterochromatin-promoting drugs using drosophila
Uploaded: 2020-03-12T14:30:00
Description: Watch this Scientific Journal Video about A Screening Method for Identification of Heterochromatin-Promoting Drugs Using Drosophila at JoVE.com

We thank J. Birchler, E. Bach and the Bloomington Drosophila Stock Center for various Drosophila strains; the National Cancer Institute (NCI) Developmental Therapeutics Program for the Oncology Set small-molecule drug library; UCSD undergraduate students including Amy Chang, Taesik You, Jessica Singh-Banga, Rachel Meza, and Alex Chavez. Research reported in this publication was supported by a research grant from American Thoracic Society to J.L. and funding from NIH: R01GM131044 to W.X.L.

1. Drug library preparation
<ol>
	<li>Identify and prepare a drug library to be screened using appropriate solvent at a desired concentration (e.g., 10 mM in DMSO). 
	NOTE: A specific example for a drug library is the Oncology Set III from National Cancer Institute (NCI) Developmental Therapeutics Program (DTP). Compounds in this set are provided as 20 &#181;L at 10 mM in 100% DMSO in two 96-well PP U-bottom plates and stored at -20 &#176;C. The NCI Plate maps, and the basic chemical data of each drug could be fou...

     

<ol>
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Heterochromatin is a condensed form of DNA that plays a central role in regulating gene expression. It is becoming increasingly more recognized in cancer and may serve as a potential target for cancer therapy15,16,17,18. Small-molecule compounds are commonly used in drug development due to advantages in manufacture, preservation, and metabolism in human bodies. To identify heterochromatin-promo...

Heterochromatin is a condensed form of DNA that plays a central role in gene expression, in regulating chromosome segregation during cell division, and in protecting against genome instability1. Heterochromatin has been considered to be a gene repression regulator and to protect chromosome integrity during cell mitosis2,3. It is associated with the di- and tri-methylation of histone H3 lysine 9 (H3K9me) during lineage commitment4,5. Moreover, recruitment of Heterochromatin Protein 1 (HP1) chromodomain proteins is also considered to be associated with heterochromatin and epigenetic repression of gene expression6. These proteins are essential components and markers of heterochromatin formation.
Since genomic instability enables cells to acquire genetic alterations that promote carcinogenesis, heterochromatin is becoming more recognized in cancer development and may be targeted for cancer treatment7,8. Currently, there are no drugs that are well-established in assisting heterochromatin formation. Here, we present a simple and quick yet efficient method for screening small-molecule compounds that promote heterochromatin formation. The screening is done by treating Drosophila with a library of small-molecule drugs. This method takes advantage of a variegated eye color phenotype in the DX1Drosophila strain that is influenced by heterochromatin levels. DX1 flies contain a tandem array of seven P[lac-w] transgenes, which have the variegated expression/depression depending on heterochromatinization, therefore, the extent of variegation in the eye color reflect the heterochromatin level. Specifically, increasing heterochromatin could be detected by the rising proportion of variegated eye color (white eye). On the contrary, decreasing heterochromatin would be detected by the rising proportion of the P[lac-w] transgene expression (red eye)9,10,11,12.
Therefore, we take advantage of this Drosophila transgene system that produces a variegated eye color phenotype since its expression is directly correlated to the amount of heterochromatin present. Upon discovery of compounds that are suspected to promote heterochromatin formation, we may confirm this suspicion using other methods such as western blot. These heterochromatin-promoting substances may be further developed for clinical trials in patients in the future.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Drosophila</td>
			<td></td>
			<td>DX1 strain</td>
			<td>DX1 flies were kindly provided by James Birchler (University of Missouri)</td>
		</tr>
		<tr>
			<td>Drosophila food media</td>
			<td>UCSD fly kitchen</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Methotrexate</td>
			<td>NCI drug library</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide (DMSO)</td>
			<td>Sigma</td>
			<td>D2650</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethyl alcohol</td>
			<td>Sigma</td>
			<td>E7023-500ML</td>
			<td></td>
		</tr>
	</tbody>
</table>

a screening method for identification of heterochromatin-promoting drugs using drosophila

Drosophila is an excellent model organism that can be used to screen compounds that might be useful for cancer therapy. The method described here is a cost-effective in vivo method to identify heterochromatin-promoting compounds by using Drosophila. The Drosophila&#39;s DX1 strain, having a variegated eye color phenotype that reflects the extents of heterochromatin formation, thereby providing a tool for a heterochromatin-promoting drug screen. In this screening method, eye variegation is quantified based on the surface area of red pigmentation occupying parts of the eye and is scored on a scale from 1 to 5. The screening method is straightforward and sensitive and allows for testing compounds in vivo. Drug screening using this method provides a fast and inexpensive way for identifying heterochromatin-promoting drugs that could have beneficial effects in cancer therapeutics. Identifying compounds that promote the formation of heterochromatin could also lead to the discovery of epigenetic mechanisms of cancer development.

This protocol was successfully used to screen compounds that promote heterochromatin formation in Drosophila, which is an efficient and low-cost in vivo system for drug development (Figure 1). We screened a small-molecule drug library, Oncology Set III, which is composed of 97 FDA authorized oncology drugs, using the DX1 strain of Drosophila melanogaster (Figure 1B). The results for a significant drug were represented ...

Watch this Scientific Journal Video about A Screening Method for Identification of Heterochromatin-Promoting Drugs Using Drosophila at JoVE.com

A Screening Method for Identification of Heterochromatin-Promoting Drugs Using Drosophila

Drosophila is a widely used experimental model suitable for screening drugs with potential applications for cancer therapy. Here, we describe the use of Drosophila variegated eye color phenotypes as a method for screening small-molecule compounds that promote heterochromatin formation.

A Screening Method for Identification of Heterochromatin-Promoting Drugs Using Drosophila

Drosophila is an excellent model organism that can be used to screen compounds that might be useful for cancer therapy. The method described here is a ...

Currently there are no drugs that are well-established in promoting heterochromatin formation. Here we present a simple and efficient method for identifying small molecule compounds that promote this process. Our screening protocol provides a simple, inexpensive, easy to follow in vivo system for heterochromatin-promoting drug identification.Identifying compounds that promote heterochromatin formation may lead to the discovery of mechanisms of cancer that mend and cancer therapy. This cost effective has been measured for identifying heterochromatin-promoting compounds in Drosophila could also be used to count form hits as it is a preventative measure to a highest cell pool of cell screening. Our screening protocol could also be useful for quick pilot screens as this Drosophila TranSheet system produces a variegated eye color phenotype that is inversely correlated to the amount of heterochromatin present in the fly.Helping to demonstrate the procedure will be Kenny Dao, an undergrad student from our laboratory. After identifying and preparing a drug library for a screening using an appropriate solvent, and the desired concentration, cross three male flies with three or more virgin female flies in a 25 by 95 millimeter food vial. With nine millimeters of standard Drosophila food medium.Set up three replica vials for each drug. Add one control vial for the screen. And allow the flies to lay eggs for two days at room temperature.On day two of the cross, anesthetize the flies with a short burst of carbon dioxide. And discard the parent flies in a bottle containing 70%ethanol. Next, dilute each drug compound from the initial stock to attend micro molar final concentration in 33%DMSO in water.And add 60 microliters of the drug, or the control 33%DMSO alone, on top of the fly food. Then confirm that no parent flies are present within the vials. And add the drug solution to the appropriate vials.Two days after the F1 flies emerge, transfer anesthetized flies from one vial at a time onto a porous dissecting pad with carbon dioxide filtering through from underneath the filter paper. Under a dissecting microscope, examine each whole fly, identifying all of the heterozygous males by their lack of the curly o-dominant curly wing phenotype. Score the eye color of each heterozygous male on a scale of one to five.With a one score being assigned to a less than 5%red scattered eye total surface area. Add a two score to flies with a 6 to 25%red spot eye total surface area. A three to flies with a 26 to 50%red spot eye total surface area.A four to flies with a 51 to 75%red spot eye total surface area. And a five flies with a greater than 75%red spot eye total surface area. Then calculate the mean color index of all of the males from each vial scored in triplicate.To confirm that the compounds indeed promote heterochromatin formation, a different validation technique, such as western blotting, can be performed. In this representative experiment, a small molecule drug library, oncology set 3, which is composed of 97 FDA authorized oncology drugs, was screened using the DX1 strain of Drosophila Melanogaster. According the screening assay, methotrexate, coded as E7 in the library, caused the most variation within the Dx1 strain.Suggesting that methotrexate could be the most promising heterochromatin-promoting drug for future cancer targeted therapy. To further confirm that this compound promotes heterochromatin transformation, western blot data was performed. Demonstrating the up regulation of heterochromatin formatin associated protein, H3K9 trimethylation, and validating the screening results.The critical step is scoring the eye color of each of the white 11-18 DX1 heterozygous male flies on a scale of one to five according to a predetermined study route. We can use western blots or immunostaining to confirm the hits. The discovery of compounds that are suspected to promote heterochromatin formation may also lead to the discovery of IV genetic mechanism of cancer development and clinical trials in human patients.

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