Name: an efficient strategy for generating tissue-specific binary transcription systems in drosophila by genome editing
Uploaded: 2018-09-19T15:00:00
Description: Watch this Scientific Journal Video about An Efficient Strategy for Generating Tissue-specific Binary Transcription Systems in Drosophila by Genome Editing at JoVE.com

We thank Dr. F. Port, Dr. K. O&#39;Connor-Giles, and Dr. S. Feng for discussions on CRISPR strategy; Dr. T.B. Kornberg, and the Bloomington Stock Center for reagents; UMD imaging core facility; and funding from NIH: R00HL114867 and R35GM124878 to SR.

1. Designing and Constructing the gRNA Expression Vector
<ol>
	<li>To precisely replace a long defined region of an exon, use a dual gRNA approach6, in which each gRNA can specifically target two ends of the selected region of interest. To obtain an accurate gene-specific spatiotemporal expression of the driver, select two gRNA target sites within the first coding exon of the gene.</li>
	<li>For Drosophila melanogaster, select the gRNA target sites using the flyCRISPR Optimal Ta...

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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimized+CRISPR/Cas+tools+for+efficient+germline+and+somatic+genome+engineering+in+Drosophila.">Optimized CRISPR/Cas tools for efficient germline and somatic genome engineering in Drosophila.</a> Proceedings of the National Academy of Sciences of the United States of America. 111 (29), E2967-E2976 (2014).</li><li>Gratz, S. J., Rubinstein, C. D., Harrison, M. M., Wildonger, J., O'Connor-Giles, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CRISPR-Cas9+Genome+Editing+in+Drosophila.">CRISPR-Cas9 Genome Editing in Drosophila.</a> Current Protocols in Molecular Biology. 111 (1), (2015).</li><li>Doench, J. G., Hartenian, E., 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=Rational+design+of+highly+active+sgRNAs+for+CRISPR-Cas9-mediated+gene+inactivation.">Rational design of highly active sgRNAs for CRISPR-Cas9-mediated gene inactivation.</a> Nature Biotechnology. 32 (12), 1262-1267 (2014).</li><li>Port, F., Bullock, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Augmenting+CRISPR+applications+in+Drosophila+with+tRNA-flanked+sgRNAs.">Augmenting CRISPR applications in Drosophila with tRNA-flanked sgRNAs.</a> Nature Methods. 13 (10), 852-854 (2016).</li><li>Beumer, K. J., Trautman, J. K., Mukherjee, K., Carroll, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Donor+DNA+Utilization+During+Gene+Targeting+with+Zinc-Finger+Nucleases.">Donor DNA Utilization During Gene Targeting with Zinc-Finger Nucleases.</a> G3. 3 (4), 657-664 (2013).</li><li>Pfeiffer, B. D., Ngo, T. -. T. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Refinement+of+tools+for+targeted+gene+expression+in+Drosophila.">Refinement of tools for targeted gene expression in Drosophila.</a> Genetics. 186 (2), 735-755 (2010).</li><li>Lin, C. -. C., Potter, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Editing+Transgenic+DNA+Components+by+Inducible+Gene+Replacement+in+Drosophila+melanogaster.">Editing Transgenic DNA Components by Inducible Gene Replacement in Drosophila melanogaster.</a> Genetics. 203 (4), 1613-1628 (2016).</li><li>Li, W., K&#246;ster, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quality+control,+modeling,+and+visualization+of+CRISPR+screens+with+MAGeCK-VISPR.">Quality control, modeling, and visualization of CRISPR screens with MAGeCK-VISPR.</a> Genome Biology. 16 (1), 281 (2015).</li></ol>

Traditionally, Drosophila enhancer traps were generated by two different methods. One of the ways includes random insertion of a driver (eg., Gal4) sequence in the genome by transposition (e.g., P-element transposition)1 . Alternatively, the driver sequences can be placed under the transcriptional control of a putative enhancer/promoter region in a plasmid construct, which would then be integrated into an ectopic site of the genome3,<su...

The genetic toolbox for targeted gene expression has been well developed in Drosophila, making it one of the best model systems to investigate the function of genes involved in a wide variety of cellular processes. Binary expression systems, such as yeast Gal4/UAS (upstream activation sequence), was first adopted for tissue-specific enhancer trapping and gene misexpression in the Drosophila genetic model1 (Figure 1). This system facilitated the development of a large number of techniques such as spatiotemporal regulation of gene overexpression, misexpression, knockout in selected groups of cells as well as in cell ablation, cell marking, live tracing of cellular and molecular processes in embryo and tissues, lineage tracing and mosaic analyses during development. A number of binary transcription system, such as the bacterial LexA/LexAop system (Figure 1) and Neurospora Q-system, are powerful genetic tools that are now widely used in Drosophila, in addition to the original Gal4/UAS system for targeted gene expression1,2,3.
Here, we present a method to generate highly reliable tissue-specific binary expression system by employing a genome-editing technique. The recent advancements in CRISPR/Cas9 genome editing technology have allowed unprecedented opportunities to make directed genome changes in a broad range of organisms. Compared to the other available genome editing techniques, the CRISPR/Cas9 system is inexpensive, efficient, and reliable. This technology utilizes components of the bacterial adaptive immune system: a Cas9 endonuclease of Streptococcus pyogenes that creates a double-strand break (DSB), and a chimeric guide RNA (gRNA), which guides the Cas9 to a particular genome site for targeted DSB4. The cells contain the machinery to repair the DSB using different pathways. Non-homologous end joining (NHEJ) leads to small insertions or deletions to disrupt gene function, while homology-directed repair (HDR) introduces a defined directed/desirable genomic knock-in/knock-out by using an exogenous HDR donor as a template. The HDR-based replacement strategy can efficiently be utilized to generate a highly reliable tissue-specific binary expression system, which can overcome all the limitations of the traditional enhancer trap methods. We describe a step-by-step procedure for utilization of CRISPR/Cas9-based HDR repair in generating a binary transcription driver line that is expressed under the control of endogenous transcriptional and post-transcriptional regulation of a Drosophila gene. In this protocol, we demonstrate the generation of a driver line specific for branchless (bnl) gene encoding an FGF family protein that regulates branching morphogenesis of tracheal airway epithelium5. In this example, the first coding exon of the bnl gene was replaced by the sequence of a bacterial LexA transactivator sequence without altering any endogenous cis-regulatory sequences of the bnl gene. We show that the strategy generated a bnl-LexA driver line that spatiotemporally controls the expression of a reporter gene placed downstream of LexAoperator (LexAop or LexO) exclusively in bnl-expressing epithelial/mesenchymal/neuronal cells.

<table>
	<tbody>
		<tr>
			<td>X-Gal/IPTG</td>
			<td>Gentrox (Genesee Scientific)</td>
			<td>18-218</td>
			<td>cloning</td>
		</tr>
		<tr>
			<td>LB-Agar</td>
			<td>BD Difco</td>
			<td>BD&#160;244520</td>
			<td>cloning</td>
		</tr>
		<tr>
			<td>Tris-HCl</td>
			<td>Sigma Aldrich</td>
			<td>T3253</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Sigma Aldrich</td>
			<td>E1161</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma Aldrich</td>
			<td>S7653</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>UltraPure DNase/RNase-Free Water</td>
			<td>ThermoFisher Scientific</td>
			<td>10977-023</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>10%SDS</td>
			<td>Sigma Aldrich</td>
			<td>71736</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>KOAc</td>
			<td>Fisher-Scientific</td>
			<td>P1190</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>EtOH</td>
			<td>Fisher-Scientific</td>
			<td>04-355-451</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>GeneJET Miniprep</td>
			<td>ThermoFisher Scientific</td>
			<td>K0503</td>
			<td>Miniprep</td>
		</tr>
		<tr>
			<td>PureLink HiPure Plasmid Maxipep kits</td>
			<td>ThermoFisher Scientific</td>
			<td>K210006</td>
			<td>Maxiprep</td>
		</tr>
		<tr>
			<td>BbsI</td>
			<td>NEB</td>
			<td>R0539S</td>
			<td>Restriction enzyme</td>
		</tr>
		<tr>
			<td>Primers</td>
			<td>IDT-DNA</td>
			<td></td>
			<td>PCR</td>
		</tr>
		<tr>
			<td>pCFD4</td>
			<td>Kornberg Lab</td>
			<td></td>
			<td>DNA template and vector for gRNA</td>
		</tr>
		<tr>
			<td>KAPA HiFi Hot Start- (Kapa Biosystems)</td>
			<td>Kapa biosystems</td>
			<td>KK2601</td>
			<td>PCR</td>
		</tr>
		<tr>
			<td>Q5-high fidelity Taq</td>
			<td>NEB</td>
			<td>NEB #M0491</td>
			<td>PCR</td>
		</tr>
		<tr>
			<td>Gibson Assembly Master Mix</td>
			<td>NEB</td>
			<td>NEB #E2611</td>
			<td>DNA assembly</td>
		</tr>
		<tr>
			<td>pBPnlsLexA:p65Uw</td>
			<td>Addgene</td>
			<td></td>
			<td>DNA template for LexA amplification</td>
		</tr>
		<tr>
			<td>Proteinase K</td>
			<td>ThermoFisher Scientific</td>
			<td>25530049</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>2x PCR PreMix, with dye (red)</td>
			<td>Sydlab</td>
			<td>MB067-EQ2R</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>Gel elution kit</td>
			<td>Zymo Research (Genesee Scientific)</td>
			<td>11-300</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>TRI reagent</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>Direct-zol RNA purification kits</td>
			<td>Zymo Research (Genesee Scientific)</td>
			<td>11-330</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>OneTaq One-Step RT-PCR Kit</td>
			<td>NEB</td>
			<td>E5315S</td>
			<td>Molecular Biology</td>
		</tr>
		<tr>
			<td>lexO-CherryCAAX</td>
			<td>Kornberg Lab</td>
			<td></td>
			<td>Fly line</td>
		</tr>
		<tr>
			<td>UAS-CD8:GFP</td>
			<td>Kornberg lab</td>
			<td></td>
			<td>Fly line</td>
		</tr>
		<tr>
			<td>btl-Gal4</td>
			<td>Kornberg lab</td>
			<td></td>
			<td>Fly line</td>
		</tr>
		<tr>
			<td>MKRS/TB6B</td>
			<td>Kornberg lab</td>
			<td></td>
			<td>Fly line</td>
		</tr>
		<tr>
			<td>Confocal Microscope SP5X</td>
			<td>Leica</td>
			<td></td>
			<td>Imaging expression pattern</td>
		</tr>
		<tr>
			<td>CO2 station</td>
			<td>Genesee Scientific</td>
			<td>59-122WCU</td>
			<td>fly pushing</td>
		</tr>
		<tr>
			<td>Stereo microscope</td>
			<td>Olympus</td>
			<td>SZ-61</td>
			<td>fly pushing</td>
		</tr>
		<tr>
			<td>Microtube homogenizing pestles</td>
			<td>Fisher-Scientific</td>
			<td>03-421-217</td>
			<td>genomic DNA isolation</td>
		</tr>
		<tr>
			<td>NanoDrop spectrophotometer</td>
			<td>ThermoFisher Scientific</td>
			<td>ND-1000</td>
			<td>DNA quantification</td>
		</tr>
	</tbody>
</table>

an efficient strategy for generating tissue-specific binary transcription systems in drosophila by genome editing

Binary transcription systems are powerful genetic tools widely used for visualizing and manipulating cell fate and gene expression in specific groups of cells or tissues in model organisms. These systems contain two components as separate transgenic lines. A driver line expresses a transcriptional activator under the control of tissue-specific promoters/enhancers, and a reporter/effector line harbors a target gene placed downstream to the binding site of the transcription activator. Animals harboring both components induce tissue-specific transactivation of a target gene expression. Precise spatiotemporal expression of the gene in targeted tissues is critical for unbiased interpretation of cell/gene activity. Therefore, developing a method for generating exclusive cell/tissue-specific driver lines is essential. Here we present a method to generate highly tissue-specific targeted expression system by employing a &#34;Clustered Regularly Interspaced Short Palindromic Repeat/CRISPR-associated&#34; (CRISPR/Cas)-based genome editing technique. In this method, the endonuclease Cas9 is targeted by two chimeric guide RNAs (gRNA) to specific sites in the first coding exon of a gene in the Drosophila genome to create double-strand breaks (DSB). Subsequently, using an exogenous donor plasmid containing the transactivator sequence, the cell-autonomous repair machinery enables homology-directed repair (HDR) of the DSB, resulting in precise deletion and replacement of the exon with the transactivator sequence. The knocked-in transactivator is expressed exclusively in cells where the cis-regulatory elements of the replaced gene are functional. The detailed step-by-step protocol presented here for generating a binary transcriptional driver expressed in Drosophila fgf/branchless-producing epithelial/neuronal cells can be adopted for any gene- or tissue-specific expression.

This protocol was successfully used to generate a targeted binary expression reporter system specific for bnl expressing cells5. The cis-regulatory elements (CREs) that control complex spatiotemporal bnl expression are not characterized. Therefore, to achieve spatiotemporal expression under the control of the endogenous bnl regulatory sequence, only the first coding exon of bnl was designed to be replaced with the sequen...

Watch this Scientific Journal Video about An Efficient Strategy for Generating Tissue-specific Binary Transcription Systems in Drosophila by Genome Editing at JoVE.com

An Efficient Strategy for Generating Tissue-specific Binary Transcription Systems in Drosophila by Genome Editing

Here, we present a method for generating tissue-specific binary transcription systems in Drosophila by replacing the first coding exon of genes with transcription drivers. The CRISPR/Cas9-based method places a transactivator sequence under the endogenous regulation of a replaced gene, and consequently facilitates transctivator expression exclusively in gene-specific spatiotemporal patterns.

An Efficient Strategy for Generating Tissue-specific Binary Transcription Systems in Drosophila by Genome Editing

Binary transcription systems are powerful genetic tools widely used for visualizing and manipulating cell fate and gene expression in specific groups of ...

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