We would like to thank Hugo Bellen and the Bloomington Stock Center for reagents. We further thank Koen Venken, Hugo Bellen and all members of the Buszczak and Hiesinger labs for helpful discussions. This work was supported by grants from the National Institute of Health to ACR (T32GM083831), PRH (RO1EY018884) and to MB (RO1GM086647), a grant by the Cancer Prevention Research Institute of Texas to MB and PRH (RP100516), and the Welch Foundation (I-1657) to PRH. MB is an E.E. and Greer Garson Fogelson Scholar in Biomedical Research and PRH is a Eugene McDermott Scholar in Biomedical Research at UT Southwestern Medical Center.

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The authors do not have any competing interests in regards to the techniques outlined here.

The power of genetic model organisms in biomedical research is largely based on the tools available for genetic manipulation. The small models C. elegans and Drosophila in particular allow for inexpensive and fast molecular genetic analyses of complete pathways and gene families implicated in multicellular development or function. Recent years have seen significant advances in tool development for manipulating genes in Drosophila 14,15. For example, recombineering, which is widely us...

Clean molecularly-defined manipulations of single genes at their endogenous loci offer an invaluable tool to study a myriad of questions relevant to eukaryotic biology. Drosophila reverse genetic techniques for generating loss-of-function alleles had proven to be challenging until Golic and colleagues introduced in vivo gene targeting using homologous recombination to Drosophila 1-3. They demonstrated that specific genomic loci could be targeted using a linear fragment of DNA from an integrated transgenic construct. This linear "donor" DNA is generated in vivo through FRT-mediated recombination (to excise the DNA from the chromosome as a circular molecule) followed by linearization with the meganuclease I-SceI. Although this methodology has been successfully used to generate a variety of defined lesions, the technique has not been easily scalable for the manipulation of numerous genes in parallel because each individual knockout construct requires distinct and custom design. For example, difficulties in seamlessly manipulating large fragments of DNA (&gt;5 kb) in vitro using classical restriction enzyme/ligation cloning or PCR, as well as the size limitations of traditional in vivo transformation vectors often interfere with the rapid creation of homologous recombination targeting vectors. To overcome these limitations, we combined the recombineering/transgenesis P[acman] system, which allows the sub-cloning and transgenesis of up to 100 kb of DNA, with the ends-out gene targeting methodology to establish an efficient and relatively rapid platform that facilitates Drosophila gene targeting.
Recombination-mediated genetic engineering (recombineering) is a powerful homologous recombination-based cloning technology 4,5. In contrast to conventional restriction enzyme/ligase cloning, recombineering is not limited by the sequence or size of the manipulated DNA. Recombineering uses a special E. coli strain that harbors recombination machinery provided by a defective &lambda; prophage 4. This technique has recently been adopted for use in Drosophila 6,7. Recombineering in Drosophila relies on a modified conditionally amplifiable bacterial artificial chromosome (BAC) vector called P[acman] 6,7. This vector carries two origins of replication: OriV, which produces high-copy number upon chemical induction for the purification of large quantities of DNA required for sequencing and embryo injection and OriS, which maintains low-copy number under basal conditions. Additionally, the P[acman] vector is equipped with a bacterial attachment (attB) site. The attB site serves as a substrate for &Phi;C31 integrase-mediated transgenesis that allows incorporation of large DNA fragments into a predetermined landing site within the Drosophila genome 8,9.
We have generated a P[acman] vector (referred to as P[acman]-KO 1.0) that can be used as a targeting vector for ends-out homologous recombination 10,11. To incorporate ends-out gene targeting technology into the system, we added two FRT and two I-SceI sites. We have also included a Gateway cassette within this modified vector to streamline the process of incorporating the homology arms into P[acman]-KO 1.0. This provides a rapid and simple way to introduce virtually any genomic region of interest into the targeting vector. In this protocol we will describe how to engineer a targeting vector using P[acman]-KO 1.0, and how to mobilize this vector in vivo to target the endogenous locus. For the purpose of this protocol we will use the RFP/Kan cassette to replace a gene of interest, but a variety of cassettes that contain an antibiotic selection marker can be used with this protocol. We have designed and successfully used a set of cassettes for gene replacement and tagging 10,11.

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
			<td>Comments (optional)</td>
		</tr>
		<tr>
			<td>SW102 Recombination competent bacteria</td>
			<td>NCI-Frederick</td>
			<td>Recombination Bacteria (SW102, SW105 and SW106)</td>
			<td><a href="http://ncifrederick.cancer.gov/research/brb/logon.aspx" target="_blank">http://ncifrederick.cancer.gov/research/brb/logon.aspx</a></td>
		</tr>
		<tr>
			<td>TransforMax EPI300 electrocopmpetent E. coli</td>
			<td>Epicentre</td>
			<td>EC300110</td>
			<td>Includes CopyControl induction solution</td>
		</tr>
		<tr>
			<td>PfuUltra II Fusion HS DNA Polymerase</td>
			<td>Aligent Technology Inc.</td>
			<td>600670</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>BamHI-HF</td>
			<td>New England Biolabs</td>
			<td>R3136S</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Zymoclean Gel DNA Recovery Kit</td>
			<td>Zymo Research</td>
			<td>D4001</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Use Gateway BP ClonaseII Enzyme kit</td>
			<td>Invitrogen</td>
			<td>11789-020</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>P[acman]KO1.010</td>
			<td>Buszczak and Hiesinger Labs</td>
			<td>Upon request</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>pENTR RFP-Kan11</td>
			<td>Buszczak and Hiesinger Labs</td>
			<td>Upon request</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Flystocks</td>
			<td>Bloomington stock center</td>
			<td>Stock numbers: 25680, 25679</td>
			<td>y1 w*/Dp(2;Y)G, P{hs-hid}Y; P{70FLP}11 P{70I-SceI}2B snaSco/CyO, P{hs-hid}4 
			y1 w*/Dp(2;Y)G, P{hs-hid}Y; P{70FLP}23 P{70I-SceI}4A/TM3, P{hs-hid}14, Sb1</td>
		</tr>
		<tr>
			<td>Electroporation machine</td>
			<td>Biorad GenePulser Xcell with PC module</td>
			<td>165-2662</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Cuvettes</td>
			<td>Fisher Brand</td>
			<td>#FB101</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

recombineering homologous recombination constructs in drosophila

The continued development of techniques for fast, large-scale manipulation of endogenous gene loci will broaden the use of Drosophila melanogaster as a genetic model organism for human-disease related research. Recent years have seen technical advancements like homologous recombination and recombineering. However, generating unequivocal null mutations or tagging endogenous proteins remains a substantial effort for most genes. Here, we describe and demonstrate techniques for using recombineering-based cloning methods to generate vectors that can be used to target and manipulate endogenous loci in vivo. Specifically, we have established a combination of three technologies: (1) BAC transgenesis/recombineering, (2) ends-out homologous recombination and (3) Gateway technology to provide a robust, efficient and flexible method for manipulating endogenous genomic loci. In this protocol, we provide step-by-step details about how to (1) design individual vectors, (2) how to clone large fragments of genomic DNA into the homologous recombination vector using gap repair, and (3) how to replace or tag genes of interest within these vectors using a second round of recombineering. Finally, we will also provide a protocol for how to mobilize these cassettes in vivo to generate a knockout, or a tagged gene via knock-in. These methods can easily be adopted for multiple targets in parallel and provide a means for manipulating the Drosophila genome in a timely and efficient manner.

Amplification of the LA and RA homology arms should produce 500 bp products and the PCR-SOE reaction should yield a 1.0 kb product (Sections 2.1-2.4; Figure 2). The BP reaction performed in section 2.5 is typically very efficient and bacterial transformation of the product yields 5-100 colonies on average. Nearly all the colonies tested with PCR check show the expected PCR product.
During the first round of recombineering (Section 3) expect to get 20-40 colonies after transfor...

Watch this Scientific Journal Video about Recombineering Homologous Recombination Constructs in Drosophila at JoVE.com

Recombineering Homologous Recombination Constructs in Drosophila

Homologous recombination techniques greatly advance Drosophila genetics by enabling the creation of molecularly precise mutations. The recent adoption of recombineering allows one to manipulate large pieces of DNA and transform them into Drosophila6. The methods presented here combine these techniques to rapidly generate large homologous recombination vectors.

Recombineering Homologous Recombination Constructs in Drosophila

The continued development of techniques for fast, large-scale manipulation of endogenous gene loci will broaden the use of Drosophila melanogaster as a ...

recombineering-homologous-recombination-constructs-in-drosophila

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19.1K Views.  University of Texas Southwestern Medical Center at Dallas. Homologous recombination techniques greatly advance Drosophila genetics by enabling the creation of molecularly precise mutations. The recent adoption of recombineering allows one to manipulate large pieces of DNA and transform them into Drosophila6. The methods presented here combine these techniques to rapidly generate large homologous recombination vectors.