Name: crispr/cas9-mediated targeted integration in vivo using a homology-mediated end joining-based strategy
Uploaded: 2018-03-12T14:00:00
Description: Watch this Scientific Journal Video about CRISPR/Cas9-mediated Targeted Integration In Vivo Using a Homology-mediated End Joining-based Strategy at JoVE.com

This work was supported by CAS Strategic Priority Research Program (XDB02050007, XDA01010409), the National Hightech R&#38;D Program (863 Program; 2015AA020307), the National Natural Science Foundation of China (NSFC grants 31522037, 31500825, 31571509, 31522038), China Youth Thousand Talents Program (to HY), Break through project of Chinese Academy of Sciences, Shanghai City Committee of science and technology project (16JC1420202 to HY), the Ministry of Science and Technology of China (MOST; 2016YFA0100500).

All procedures including animal subjects have been approved by the Biomedical Research Ethics Committee at the Shanghai Institutes for Biological Science (CAS).
1. Design of Donor Plasmids
<ol>
	<li>Selection of sgRNA
	<ol>
		<li>Use online CRISPR design tools to predict sgRNAs on the target region11,12,13,14,15. ...

<ol>
	<li>Yang, H., 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=Generation+of+Mice+Carrying+Reporter+and+Conditional+Alleles+by+CRISPR/Cas-Mediated+Genome+Engineering.">Generation of Mice Carrying Reporter and Conditional Alleles by CRISPR/Cas-Mediated Genome Engineering.</a> Cell. 154 (6), 1370-1379 (2013).</li><li>Hockemeyer, D., 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=Genetic+engineering+of+human+pluripotent+cells+using+TALE+nucleases.">Genetic engineering of human pluripotent cells using TALE nucleases.</a> Nature Biotechnology. 29 (8), 731-734 (2011).</li><li>Nakade, S., 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=Microhomology-mediated+end-joining-dependent+integration+of+donor+DNA+in+cells+and+animals+using+TALENs+and+CRISPR/Cas9.">Microhomology-mediated end-joining-dependent integration of donor DNA in cells and animals using TALENs and CRISPR/Cas9.</a> Nature Communications. 5, 5560 (2014).</li><li>Hisano, Y., 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=Precise+in-frame+integration+of+exogenous+DNA+mediated+by+CRISPR/Cas9+system+in+zebrafish.">Precise in-frame integration of exogenous DNA mediated by CRISPR/Cas9 system in zebrafish.</a> Scientific reports. 5, 8841 (2015).</li><li>Yao, X., 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=Cas9+-+Mediated+Precise+Targeted+Integration+In+Vivo+Using+a+Double+Cut+Donor+with+Short+Homology+Arms.">Cas9 - Mediated Precise Targeted Integration In Vivo Using a Double Cut Donor with Short Homology Arms.</a> EBioMedicine. , (2017).</li><li>Auer, T. O., Duroure, K., De Cian, A., Concordet, J. P., Del Bene, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+efficient+CRISPR/Cas9-mediated+knock-in+in+zebrafish+by+homology-independent+DNA+repair.">Highly efficient CRISPR/Cas9-mediated knock-in in zebrafish by homology-independent DNA repair.</a> Genome research. 24 (1), 142-153 (2014).</li><li>Maresca, M., Lin, V. G., Guo, N., Yang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Obligate+ligation-gated+recombination+(ObLiGaRe):+custom-designed+nuclease-mediated+targeted+integration+through+nonhomologous+end+joining.">Obligate ligation-gated recombination (ObLiGaRe): custom-designed nuclease-mediated targeted integration through nonhomologous end joining.</a> Genome Research. 23 (3), 539-546 (2013).</li><li>Suzuki, K., 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=In+vivo+genome+editing+via+CRISPR/Cas9+mediated+homology-independent+targeted+integration.">In vivo genome editing via CRISPR/Cas9 mediated homology-independent targeted integration.</a> Nature. 540 (7631), 144-149 (2016).</li><li>Cong, L., 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=Multiplex+genome+engineering+using+CRISPR/Cas+systems.">Multiplex genome engineering using CRISPR/Cas systems.</a> Science. 339 (6121), 819-823 (2013).</li><li>Yao, X., 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=Homology-mediated+end+joining-based+targeted+integration+using+CRISPR/Cas9.">Homology-mediated end joining-based targeted integration using CRISPR/Cas9.</a> Cell Research. 27 (6), 801-814 (2017).</li><li>Han, D. W., 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=Direct+reprogramming+of+fibroblasts+into+epiblast+stem+cells.">Direct reprogramming of fibroblasts into epiblast stem cells.</a> Nature Cell Biology. 13 (1), 66-71 (2011).</li><li>Han, D. W., 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=Direct+Reprogramming+of+Fibroblasts+into+Neural+Stem+Cells+by+Defined+Factors.">Direct Reprogramming of Fibroblasts into Neural Stem Cells by Defined Factors.</a> Cell Stem Cell. , (2012).</li><li>Ambasudhan, R., 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=Direct+reprogramming+of+adult+human+fibroblasts+to+functional+neurons+under+defined+conditions.">Direct reprogramming of adult human fibroblasts to functional neurons under defined conditions.</a> Cell Stem Cell. 9 (2), 113-118 (2011).</li><li>Sparman, M., 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=Epigenetic+reprogramming+by+somatic+cell+nuclear+transfer+in+primates.">Epigenetic reprogramming by somatic cell nuclear transfer in primates.</a> Stem Cells. 27 (6), 1255-1264 (2009).</li><li>Schatten, G., Mitalipov, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developmental+biology:+Transgenic+primate+offspring.">Developmental biology: Transgenic primate offspring.</a> Nature. 459 (7246), 515-516 (2009).</li><li>Hsu, P. D., 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=DNA+targeting+specificity+of+RNA-guided+Cas9+nucleases.">DNA targeting specificity of RNA-guided Cas9 nucleases.</a> Nature Biotechnology. 31 (9), 827-832 (2013).</li><li>Cong, L., 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=Multiplex+Genome+Engineering+Using+CRISPR/Cas+Systems.">Multiplex Genome Engineering Using CRISPR/Cas Systems.</a> Science. 339 (6121), 819-823 (2013).</li><li>Quadros, R. M., 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=Easi-CRISPR:+a+robust+method+for+one-step+generation+of+mice+carrying+conditional+and+insertion+alleles+using+long+ssDNA+donors+and+CRISPR+ribonucleoproteins.">Easi-CRISPR: a robust method for one-step generation of mice carrying conditional and insertion alleles using long ssDNA donors and CRISPR ribonucleoproteins.</a> Genome Biology. 18 (1), 92 (2017).</li><li>Park, K. 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=Targeted+Gene+Knockin+in+Porcine+Somatic+Cells+Using+CRISPR/Cas+Ribonucleoproteins.">Targeted Gene Knockin in Porcine Somatic Cells Using CRISPR/Cas Ribonucleoproteins.</a> International journal of molecular sciences. 217 (6), (2016).</li><li>Woo, J. W., 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=DNA-free+genome+editing+in+plants+with+preassembled+CRISPR-Cas9+ribonucleoproteins.">DNA-free genome editing in plants with preassembled CRISPR-Cas9 ribonucleoproteins.</a> Nature biotechnology. 33 (11), 1162-1164 (2015).</li><li>Harms, D. W., 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=Mouse+Genome+Editing+Using+the+CRISPR/Cas+System.">Mouse Genome Editing Using the CRISPR/Cas System.</a> Current protocols in human genetics. 83, 11-27 (2014).</li><li>Yang, H., Wang, H., Jaenisch, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generating+genetically+modified+mice+using+CRISPR/Cas-mediated+genome+engineering.">Generating genetically modified mice using CRISPR/Cas-mediated genome engineering.</a> Nature protocols. 9 (8), 1956-1968 (2014).</li><li>Grompe, M., 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=Loss+of+Fumarylacetoacetate+Hydrolase+Is+Responsible+for+the+Neonatal+Hepatic-Dysfunction+Phenotype+of+Lethal+Albino+Mice.">Loss of Fumarylacetoacetate Hydrolase Is Responsible for the Neonatal Hepatic-Dysfunction Phenotype of Lethal Albino Mice.</a> Genes &amp; development. 7 (12), 2298-2307 (1993).</li><li>Paulk, N. K., 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=Adeno-associated+virus+gene+repair+corrects+a+mouse+model+of+hereditary+tyrosinemia+in+vivo.">Adeno-associated virus gene repair corrects a mouse model of hereditary tyrosinemia in vivo.</a> Hepatology. 51 (4), 1200-1208 (2010).</li></ol>

The most critical steps in the construction of HMEJ donor plasmids are: (1) selection of the sgRNA with high DNA cleavage efficiency and low distance between sgRNA cutting site and stop codon, and (2) proper construction of HMEJ donor. CRISPR/Cas9-mediated cleavage on both transgene donor vector (containing sgRNA target sites and ~800 bp homology arms) and targeted genome is necessary for efficient and precise targeted integration in vivo. The most critical steps of generation of knock-in mice using the HMEJ-bas...

An erratum was issued for: <a href="https://www.jove.com/t/56844/crisprcas9-mediated-targeted-integration-vivo-using-homology-mediated">Studying TGF-&#946; Signaling and TGF-&#946;-induced Epithelial-to-mesenchymal Transition in Breast Cancer and Normal Cells</a>. The phrases&#160;&#34;surveyor assay&#34;&#160;and&#160;&#34;Surveyor&#160;Nuclease&#34; have&#160;been updated to &#34;T7E1 assay&#34;&#160; to &#34; T7&#160;endonuclease I&#34; respectively.&#160;
Step 1.2 in&#160;the Protocol has been updated from:
<ol class="jove_content" start="2">
	<li>Surveyor nuclease&#160;assay of sgRNA 
	NOTE: The targeting efficiency of the sgRNA used for the knock-in experiment is evaluated by surveyor nuclease assay (also known as T7 endonuclease I (T7EI) assay)17. Select the sgRNA with high DNA cleavage efficiency and a low distance between the sgRNA cutting site and the stop codon.</li>
</ol>
to:
<ol class="jove_content" start="2">
	<li>T7 endonuclease assay of sgRNA 
	NOTE: The targeting efficiency of the sgRNA used for the knock-in experiment is evaluated by T7 endonuclease (T7EI)&#160;assay17. Select the sgRNA with high DNA cleavage efficiency and a low distance between the sgRNA cutting site and the stop codon.</li>
</ol>
Figure 1 in the Representative Results has been updated&#160;from:
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56844/56844fig1.jpg" /> 
Figure 1: HMEJ-mediated targeted integration in vitro. 
(A) Experimental scheme for selection of sgRNAs: Six different sgRNAs (Cdx2-sgRNA1~Cdx2-sgRNA6) around the stop codon of the Cdx2 locus with a higher rank and off-target potential were chosen based on online CRISPR design tool. The protospacer adjacent motif (PAM) sequence is in red. (B) Experimental design: The Cas9-CMV-GFP expression plasmids expressing sgRNA, Cas9, and GFP were introduced into N2a&#160;cells. GFP+ cells were sorted at day 3 for surveyor assay. (C) Surveyor assay for Cdx2 targeting: 6 different sgRNAs were designed for surveyor assay. Normal N2a cell genomic DNA serves as control. *, the sgRNA used for Cdx2-2A-mCherry knock-in experiment. (D) Schematic overview of construction of HMEJ donors using Gibson assembly. (E) Schematic overview of HMEJ-mediated gene targeting strategy at Cdx2 locus. HAL/HAR, left/right homology arm; triangles, sgRNA target sites; OF/OR, outer forward/reverse primer; IF/IR, inner forward/reverse primer. Figure modified from previous report10.&#160;<a href="https://cloudfront.jove.com/files/ftp_upload/56844/56844fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
to:
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56844/56844fig1v3.jpg" /> 
Figure 1: HMEJ-mediated targeted integration in vitro. 
(A) Experimental scheme for selection of sgRNAs: Six different sgRNAs (Cdx2-sgRNA1~Cdx2-sgRNA6) around the stop codon of the Cdx2 locus with a higher rank and off-target potential were chosen based on online CRISPR design tool. The protospacer adjacent motif (PAM) sequence is in red. (B) Experimental design: The Cas9-CMV-GFP expression plasmids expressing sgRNA, Cas9, and GFP were introduced into N2a&#160;cells. GFP+ cells were sorted at day 3 for T7EI&#160;assay. (C) T7EI assay for Cdx2 targeting: 6 different sgRNAs were designed for T7EI assay. Normal N2a cell genomic DNA serves as control. *, the sgRNA used for Cdx2-2A-mCherry knock-in experiment. (D) Schematic overview of construction of HMEJ donors using Gibson assembly. (E) Schematic overview of HMEJ-mediated gene targeting strategy at Cdx2 locus. HAL/HAR, left/right homology arm; triangles, sgRNA target sites; OF/OR, outer forward/reverse primer; IF/IR, inner forward/reverse primer. Figure modified from previous report10.&#160;<a href="https://cloudfront.jove.com/files/ftp_upload/56844/56844fig1v3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

An erratum was issued for: <a href="https://www.jove.com/t/56844/crisprcas9-mediated-targeted-integration-vivo-using-homology-mediated">Studying TGF-&#946; Signaling and TGF-&#946;-induced Epithelial-to-mesenchymal Transition in Breast Cancer and Normal Cells</a>. The phrases&#160;&#34;surveyor assay&#34;&#160;and&#160;&#34;Surveyor&#160;Nuclease&#34; have&#160;been updated to &#34;T7E1 assay&#34;&#160; to &#34; T7&#160;endonuclease I&#34; respectively.&#160;

Erratum: CRISPR/Cas9-mediated Targeted Integration In Vivo Using a Homology-mediated End Joining-based Strategy

Precise, targeted genome editing is often required for producing genetically modified animal models and clinical therapies. Much effort has been made to develop various strategies for efficient targeted genome editing, such as zinc finger nuclease (ZFN), transcription activator-like effector nucleases (TALENs), and CRISPR/Cas9 systems. These strategies create targeted DNA double-strand breaks (DSB) in the genome, and take advantage of intrinsic DNA repair systems, such as homologous recombination (HR)1,2, microhomology-mediated end joining (MMEJ)3,4,5, and non-homologous end joining (NHEJ)6,7,8 to induce targeted integration of transgenes1,9. The HR-based strategy is currently the most commonly used genome editing approach, which is very efficient in cell lines, but not readily accessible to non-dividing cells due to its restricted occurrence in the late S/G2 phase. Thus, the HR-based strategy is not applicable for in vivo genome editing. Recently, the NHEJ-based strategy was developed for efficient gene knock-in in mouse tissues8. Nevertheless, the NHEJ-based method usually introduces indels at the junctions, making it difficult to generate precise genome editing, especially when trying to construct in-frame fusion genes8. MMEJ-based targeted integration is capable of precise genome editing. However, it only modestly increases the targeted integration efficiency in previous reports5. Therefore, improving the efficiency of precise targeted integration in vivo is urgently needed for broad therapeutic applications3.
In a recently published work, we demonstrated a homology-mediated end joining (HMEJ)-based strategy, which showed the highest targeted integration efficiency in all reported strategies both in vitro and in vivo10. Here, we describe a protocol for the establishment of the HMEJ system, and also the construction of the single-guide RNA (sgRNA) vectors targeting the gene of interest and the donor vectors harboring sgRNA target sites and ~800 bp of homology arms (Figure 1). In this protocol, we also describe the detailed steps for generation of DNA knock-in mice and brief steps for targeted integration in tissues in vivo. Moreover, a proof-of-concept study of the HMEJ-based strategy demonstrated its ability to correct Fah mutation and rescue Fah-/- liver failure mice, which further revealed its therapeutic potential.

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			<td style="width:131px;">P-97</td>
			<td style="width:524px;">&#160;Micropipette Puller (parameters: heat, 74; pull, 60; velocity, 80; time/delay, 200; pressure, 300)</td>
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		<tr height="40">
			<td height="40" style="height:40px;width:359px;">Borosilicate glass</td>
			<td style="width:192px;">Sutter Instrument</td>
			<td style="width:131px;">B100-78-10</td>
			<td style="width:524px;">type of capillaries (outer diameter 1.0 mm, inner diameter 0.78 mm with filament)&#160;</td>
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			<td height="27" style="height:27px;width:359px;">FBS</td>
			<td style="width:192px;">Gibco</td>
			<td style="width:131px;">10099141</td>
			<td style="width:524px;"></td>
		</tr>
		<tr height="31">
			<td height="31" style="height:31px;width:359px;">NEAA</td>
			<td style="width:192px;">Gibco</td>
			<td style="width:131px;">11140050</td>
			<td style="width:524px;"></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:359px;">Pen,Strep,Glutamine</td>
			<td style="width:192px;">Gibco</td>
			<td style="width:131px;">10378016</td>
			<td style="width:524px;"></td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:359px;">Gel Extraction Kit</td>
			<td style="width:192px;">Omega</td>
			<td style="width:131px;">D2500-02</td>
			<td style="width:524px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;">FACS</td>
			<td>BD AriaII</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PMSG</td>
			<td>Ningbo Sansheng Medicine</td>
			<td>S141004</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HCG</td>
			<td>Ningbo Sansheng Medicine</td>
			<td>B141002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cytochalasin B</td>
			<td>Sigma</td>
			<td>CAT#C6762</td>
			<td style="width:524px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">KSOM+AA with D-Glucose and Phenol Red</td>
			<td>Millipore</td>
			<td>CAT#MR-106-D</td>
			<td style="width:524px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">M2 Medium with Phenol Red</td>
			<td>Millipore</td>
			<td>CAT#MR-015-D</td>
			<td style="width:524px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mineral oil</td>
			<td>Sigma</td>
			<td style="width:131px;"></td>
			<td style="width:524px;"></td>
		</tr>
	</tbody>
</table>

crispr/cas9-mediated targeted integration in vivo using a homology-mediated end joining-based strategy

As a promising genome editing platform, the CRISPR/Cas9 system has great potential for efficient genetic manipulation, especially for targeted integration of transgenes. However, due to the low efficiency of homologous recombination (HR) and various indel mutations of non-homologous end joining (NHEJ)-based strategies in non-dividing cells, in vivo genome editing remains a great challenge. Here, we describe a homology-mediated end joining (HMEJ)-based CRISPR/Cas9 system for efficient in vivo precise targeted integration. In this system, the targeted genome and the donor vector containing homology arms (~800 bp) flanked by single guide RNA (sgRNA) target sequences are cleaved by CRISPR/Cas9. This HMEJ-based strategy achieves efficient transgene integration in mouse zygotes, as well as in hepatocytes in vivo. Moreover, a HMEJ-based strategy offers an efficient approach for correction of fumarylacetoacetate hydrolase (Fah) mutation in the hepatocytes and rescues Fah-deficiency induced liver failure mice. Taken together, focusing on targeted integration, this HMEJ-based strategy provides a promising tool for a variety of applications, including generation of genetically modified animal models and targeted gene therapies.

HMEJ-based genome editing in mouse embryos: To define the knock-in efficiency of the HMEJ-based method in mouse zygotes, we delivered Cas9 mRNA, sgRNA targeting the Cdx2 gene and the HMEJ donor into mouse zygotes, which was designed to fuse a p2A-mCherry reporter gene to the last codon of the Cdx2 gene (Figure 2A). The injected zygotes developed into blastocysts in the culture. To evaluate the knock-in effic...

Watch this Scientific Journal Video about CRISPR/Cas9-mediated Targeted Integration In Vivo Using a Homology-mediated End Joining-based Strategy at JoVE.com

CRISPR/Cas9-mediated Targeted Integration In Vivo Using a Homology-mediated End Joining-based Strategy

The clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (CRISPR/Cas9) system provides a promising tool for genetic engineering, and opens up the possibility of targeted integration of transgenes. We describe a homology-mediated end joining (HMEJ)-based strategy for efficient DNA targeted integration in vivo and targeted gene therapies using CRISPR/Cas9.

CRISPR/Cas9-mediated Targeted Integration In Vivo Using a Homology-mediated End Joining-based Strategy

As a promising genome editing platform, the CRISPR/Cas9 system has great potential for efficient genetic manipulation, especially for targeted integration ...

The overall goal of this HMEJ strategy is to provide a promising genetic tool for a variety of applications, including generation of genetically modified animal models and targeted gene therapies. This HMEJ passed the measure. Can have also key questions in the genetic and in neuro field.Such as how to improve the efficiency of precise targeted integration of transgenes in vivo. The main advantage of this HMEJ based strategy is ability to correct gene mutations with high efficiency in vivo. Which followed is therapeutic in potential.Demonstrating the procedure will be Xing Wang, a graduate student from my laboratory. To begin the protocol, collect 5000 N2a cells, previously transfected with Cas9 sgRNA EGFP expression vectors by fluorescence activated cell sorting or FACS, using non-transfected cells as a control. Digest the collected cells in 2 to 5 microliters of lysis buffer at 56 degrees Celsius for 30 minutes.Then heat and activate the proteinase K at 95 degrees Celsius for 10 minutes. Amplify the sample by nested PCR using the manufacturer's protocol. Mix one microliter of the lysis product with DNA polymerase and a pair of outer primers recognizing the sequence around the sgRNA target site and perform the primary PCR in a total volume of 20 microliters.Next, activate DNA polymerase at 95 degrees Celsius for 5 minutes, then perform the primary PCR with a final extension at 72 degrees Celsius for 5 minutes. Perform the secondary PCR using one microliter of primary PCR product and a pair of nested inner primers. Denature and re-anneal 300-600 nanograms of purified PCR product in 20 microliters of 1x TC7EI reaction buffer.Add one microliter of T7EI enzyme to the annealed PCR products and digest them at 37 degrees Celsius for two hours. Then run the digestion product on 2%agarose gel and 1x TAE buffer at 120 volts for 40 minutes, until the fragments are separated. Use ImageJ to determine the band intensities of cut and uncut DNA and calculate the indel frequency.For Cas9 mRNA preparation, add the T7 promoter sequence to the Cas9 coding region by PCR amplification. Next, add the primer Cas9 FR at a final concentration of 0.1 micromolar and 20 nanograms of Cas9 expressing vector to the 1x high fidelity DNA polymerase mix. Adjust the final volume to 50 microliters with nuclease free water.Activate DNA polymerase at 95 degrees Celsius for 5 minutes and perform the PCR. Purify the T7 Cas9 and PCR product for in vitro transcription, or IVT. Then transcribe 0.5 to 1 microgram of DNA, using an mRNA transcription kit at 37 degrees Celsius for 8 hours in a total volume of 20 microliters.Add 1 microliter of DNase to the mixture to remove the DNA template at 37 degrees Celsius for 15 minutes. After adding a poly(A)tail for 45 minutes at 37 degrees Celsius, recover the Cas9 mRNA with an RNA purification kit. Generate the sgRNA template driven by a T7 promoter with high fidelity DNA polymerase as performed in the previous section and choose an sgRNA scaffold containing vector as the template.After purifying the T7 sgRNA PCR product, use 0.5 to 1 microgram of DNA as the template for in vitro transcription of sgRNA using a short RNA transcription kit at 37 degrees Celsius for 6 hours, in a total volume of 20 microliters. After 6 hours of incubation, add 1 microliter of DNase to the mixture and continue the incubation at 37 degrees Celsius for 15 minutes to remove the DNA template. Purify sgRNAs again using the RNA purification kit.Dilute the sgRNA to 500 nanograms per microliter in RNase free water and store the samples at minus 80 degrees Celsius for up to three months. High quality of Cas9 mRNA and sgRNA with no degeneration and the correct line of HMEJ donor parameters are the most critical steps in the generation of knock-in mice. Place the fertilized embryos into KSOM medium at 37 degrees Celsius in an incubator with 5%carbon dioxide.Mix 100 nanograms per microliter of Cas9 mRNA, 50 nanograms per microliter of sgRNA, and 100 nanograms per microliter of HMEJ donor vector and add water to adjust the final volume to 10 microliters. Pipette the mixture up and down and place it on ice. Next, pull capillary needles using a micropipette puller.Inject a probable volume of the mixture into the cytoplasm of zygotes with well defined pronuclei in a droplet of HEPES-CZB medium containing 5 micrograms per milliliter Cytochalasin B using a microinjector with constant flow settings. Finally, culture the injected zygotes in KSOM medium at 37 degrees Celsius under 5%carbon dioxide until the blastocyst stage after 3 1/2 days for fluorescence observation. After 3 days of injections, 12.9%of the blastocysts receiving HMEJ donors were positive for mCherry, which was strictly expressed in the trophectoderm.By sequencing the PCR positive mice, all examined integration events were precise in-frame integrations at both 5 prime and 3 prime junctions. After 7 days of injections, immunofluorescent images revealed that nearly half of the transfected hepatocytes expressed mCherry as stained on the liver sections. After the withdrawal of NTBC, immunohistochemistry liver staining of Fah corrected hepatocytes of Fah negative mice receiving Fah HMEJ and Cas9 constructs showed more effective proliferation than MMEJ based method.The HMEJ based strategy could be an ideal platform for replacing mutated sequence such as part of mutation with the correct one. Which is not applicable for an HHEJ based method. After this experiment, this therapy paves the way for researchers into field where precise target integration to explore broad therapy applications.

crisprcas9-mediated-targeted-integration-vivo-using-homology-mediated

Research

JoVE Journal

Genetics

Targeted in Situ Mutagenesis of Histone Genes in Budding Yeast

We describe a PCR- and homologous recombination-based system for generating targeted mutations in histone genes in budding yeast cells. The resulting mutant alleles reside at their endogenous genomic sites and no exogenous DNA sequences are left in the genome following the procedure. Since in haploid yeast cells each of the four core histone proteins is encoded by two non-allelic genes with highly homologous open reading frames (ORFs), targeting mutagenesis specifically to one of two genes encoding a particular histone protein can be problematic. The strategy we describe here bypasses this problem by utilizing sequences outside, rather than within, the ORF of the target genes for the homologous recombination step. Another feature of this system is that the regions of DNA driving the homologous recombination steps can be made to be very extensive, thus increasing the likelihood of successful integration events. These features make this strategy particularly well-suited for histone gene mutagenesis, but can also be adapted for mutagenesis of other genes in the yeast genome.

Targeted in Situ Mutagenesis of Histone Genes in Budding Yeast

A strategy for generating mutations in histone genes at their endogenous location in Saccharomyces cerevisiae is presented.

We describe a PCR- and homologous recombination-based system for generating targeted mutations in histone genes in budding yeast cells. The resulting ...

Using a Fluorescent PCR-capillary Gel Electrophoresis Technique to Genotype CRISPR/Cas9-mediated Knockout Mutants in a High-throughput Format

The development of programmable genome-editing tools has facilitated the use of reverse genetics to understand the roles specific genomic sequences play in the functioning of cells and whole organisms. This cause has been tremendously aided by the recent introduction of the CRISPR/Cas9 system-a versatile tool that allows researchers to manipulate the genome and transcriptome in order to, among other things, knock out, knock down, or knock in genes in a targeted manner. For the purpose of knocking out a gene, CRISPR/Cas9-mediated double-strand breaks recruit the non-homologous end-joining DNA repair pathway to introduce the frameshift-causing insertion or deletion of nucleotides at the break site. However, an individual guide RNA may cause undesirable off-target effects, and to rule these out, the use of multiple guide RNAs is necessary. This multiplicity of targets also means that a high-volume screening of clones is required, which in turn begs the use of an efficient high-throughput technique to genotype the knockout clones. Current genotyping techniques either suffer from inherent limitations or incur high cost, hence rendering them unsuitable for high-throughput purposes. Here, we detail the protocol for using fluorescent PCR, which uses genomic DNA from crude cell lysate as a template, and then resolving the PCR fragments via capillary gel electrophoresis. This technique is accurate enough to differentiate one base-pair difference between fragments and hence is adequate in indicating the presence or absence of a frameshift in the coding sequence of the targeted gene. This precise knowledge effectively precludes the need for a confirmatory sequencing step and allows users to save time and cost in the process. Moreover, this technique has proven to be versatile in genotyping various mammalian cells of various tissue origins targeted by guide RNAs against numerous genes, as shown here and elsewhere.

The genotyping technique described here, which couples fluorescent polymerase chain reaction (PCR) to capillary gel electrophoresis, allows for high-throughput genotyping of nuclease-mediated knockout clones. It circumvents limitations faced by other genotyping techniques and is more cost effective than sequencing methods.

The development of programmable genome-editing tools has facilitated the use of reverse genetics to understand the roles specific genomic sequences play ...

Selection-dependent and Independent Generation of CRISPR/Cas9-mediated Gene Knockouts in Mammalian Cells

The CRISPR/Cas9 genome engineering system has revolutionized biology by allowing for precise genome editing with little effort. Guided by a single guide RNA (sgRNA) that confers specificity, the Cas9 protein cleaves both DNA strands at the targeted locus. The DNA break can trigger either non-homologous end joining (NHEJ) or homology directed repair (HDR). NHEJ can introduce small deletions or insertions which lead to frame-shift mutations, while HDR allows for larger and more precise perturbations. Here, we present protocols for generating knockout cell lines by coupling established CRISPR/Cas9 methods with two options for downstream selection/screening. The NHEJ approach uses a single sgRNA cut site and selection-independent screening, where protein production is assessed by dot immunoblot in a high-throughput manner. The HDR approach uses two sgRNA cut sites that span the gene of interest. Together with a provided HDR template, this method can achieve deletion of tens of kb, aided by the inserted selectable resistance marker. The appropriate applications and advantages of each method are discussed.

Recent advances in the ability to genetically manipulate somatic cell lines hold great potential for basic and applied research. Here, we present two approaches for CRISPR/Cas9 generated knockout production and screening in mammalian cell lines, with and without the use of selectable markers.

The CRISPR/Cas9 genome engineering system has revolutionized biology by allowing for precise genome editing with little effort. Guided by a single guide ...

A Protocol for the Production of Integrase-deficient Lentiviral Vectors for CRISPR/Cas9-mediated Gene Knockout in Dividing Cells

Lentiviral vectors are an ideal choice for delivering gene-editing components to cells due to their capacity for stably transducing a broad range of cells and mediating high levels of gene expression. However, their ability to integrate into the host cell genome enhances the risk of insertional mutagenicity and thus raises safety concerns and limits their usage in clinical settings. Further, the persistent expression of gene-editing components delivered by these integration-competent lentiviral vectors (ICLVs) increases the probability of promiscuous gene targeting. As an alternative, a new generation of integrase-deficient lentiviral vectors (IDLVs) has been developed that addresses many of these concerns. Here the production protocol of a new and improved IDLV platform for CRISPR-mediated gene editing and list the steps involved in the purification and concentration of such vectors is described and their transduction and gene-editing efficiency using HEK-293T cells was demonstrated. This protocol is easily scalable and can be used to generate high titer IDLVs that are capable of transducing cells in vitro and in vivo. Moreover, this protocol can be easily adapted for the production of ICLVs.

We describe the production strategy of integrase-deficient lentiviral vectors (IDLVs) as vehicles for delivering CRISPR/Cas9 to cells. With an ability to mediate quick and robust gene editing in cells, IDLVs present a safer and equally effective vector platform for gene delivery compared to integrase-competent vectors.

Lentiviral vectors are an ideal choice for delivering gene-editing components to cells due to their capacity for stably transducing a broad range of cells ...

Profiling DNA Replication Timing Using Zebrafish as an In Vivo Model System

DNA replication timing is an important cellular characteristic, exhibiting significant relationships with chromatin structure, transcription, and DNA mutation rates. Changes in replication timing occur during development and in cancer, but the role replication timing plays in development and disease is not known. Zebrafish were recently established as an in vivo model system to study replication timing. Here is detailed the protocols for using the zebrafish to determine DNA replication timing. After sorting cells from embryos and adult zebrafish, high-resolution genome-wide DNA replication timing patterns can be constructed by determining changes in DNA copy number through analysis of next generation sequencing data. The zebrafish model system allows for evaluation of the replication timing changes that occur in vivo throughout development, and can also be used to assess changes in individual cell types, disease models, or mutant lines. These methods will enable studies investigating the mechanisms and determinants of replication timing establishment and maintenance during development, the role replication timing plays in mutations and tumorigenesis, and the effects of perturbing replication timing on development and disease.

Profiling DNA Replication Timing Using Zebrafish as an In Vivo Model System

Zebrafish were recently used as an in vivo model system to study DNA replication timing during development. Here is detailed the protocols for using zebrafish embryos to profile replication timing. This protocol can be easily adapted to study replication timing in mutants, individual cell types, disease models, and other species.

DNA replication timing is an important cellular characteristic, exhibiting significant relationships with chromatin structure, transcription, and DNA ...

Targeted Next-generation Sequencing and Bioinformatics Pipeline to Evaluate Genetic Determinants of Constitutional Disease

Next-generation sequencing (NGS) is quickly revolutionizing how research into the genetic determinants of constitutional disease is performed. The technique is highly efficient with millions of sequencing reads being produced in a short time span and at relatively low cost. Specifically, targeted NGS is able to focus investigations to genomic regions of particular interest based on the disease of study. Not only does this further reduce costs and increase the speed of the process, but it lessens the computational burden that often accompanies NGS. Although targeted NGS is restricted to certain regions of the genome, preventing identification of potential novel loci of interest, it can be an excellent technique when faced with a phenotypically and genetically heterogeneous disease, for which there are previously known genetic associations. Because of the complex nature of the sequencing technique, it is important to closely adhere to protocols and methodologies in order to achieve sequencing reads of high coverage and quality. Further, once sequencing reads are obtained, a sophisticated bioinformatics workflow is utilized to accurately map reads to a reference genome, to call variants, and to ensure the variants pass quality metrics. Variants must also be annotated and curated based on their clinical significance, which can be standardized by applying the American College of Medical Genetics and Genomics Pathogenicity Guidelines. The methods presented herein will display the steps involved in generating and analyzing NGS data from a targeted sequencing panel, using the ONDRISeq neurodegenerative disease panel as a model, to identify variants that may be of clinical significance.

Targeted next-generation sequencing is a time- and cost-efficient approach that is becoming increasingly popular in both disease research and clinical diagnostics. The protocol described here presents the complex workflow required for sequencing and the bioinformatics process used to identify genetic variants that contribute to disease.

Next-generation sequencing (NGS) is quickly revolutionizing how research into the genetic determinants of constitutional disease is performed. The ...

Gene-targeted Random Mutagenesis to Select Heterochromatin-destabilizing Proteasome Mutants in Fission Yeast

Random mutagenesis of a target gene is commonly used to identify mutations that yield the desired phenotype. Of the methods that may be used to achieve random mutagenesis, error-prone PCR is a convenient and efficient strategy for generating a diverse pool of mutants (i.e., a mutant library). Error-prone PCR is the method of choice when a researcher seeks to mutate a pre-defined region, such as the coding region of a gene while leaving other genomic regions unaffected. After the mutant library is amplified by error-prone PCR, it must be cloned into a suitable plasmid. The size of the library generated by error-prone PCR is constrained by the efficiency of the cloning step. However, in the fission yeast, Schizosaccharomyces pombe, the cloning step can be replaced by the use of a highly efficient one-step fusion PCR to generate constructs for transformation. Mutants of desired phenotypes may then be selected using appropriate reporters. Here, we describe this strategy in detail, taking as an example, a reporter inserted at centromeric heterochromatin.

This article describes a detailed methodology for random mutagenesis of a target gene in fission yeast. As an example, we target rpt4+, which encodes a subunit of the 19S proteasome, and screen for mutations that destabilize heterochromatin.

Random mutagenesis of a target gene is commonly used to identify mutations that yield the desired phenotype. Of the methods that may be used to achieve ...

Determining the Egg Fertilization Rate of Bemisia tabaci Using a Cytogenetic Technique

A few species of sap-sucking whiteflies are some of the most damaging terrestrial pests worldwide because of the crop damage they inflict and plant viruses they vector. Despite numerous studies of the biology of these species in different environments, a key life history parameter, offspring sex ratios, has received little attention, yet is important for predicting population dynamics. The primary sex ratio (sex ratio at oviposition) of Bemisia tabaci has never been reported but can be found by determining the egg fertilization rate of this haplodiploid insect. The technique involves the dechorionation of eggs with bleach, a series of fixation steps, and the application of the general DNA fluorescent stain, DAPI (4&#8242;,6-diamidino-2-phenylindole, a DNA-binding fluorescent dye), to bind to female and male pronuclei. Here, we present the technique, and an example of its application, to test whether an endosymbiotic bacterium, Rickettsia sp. nr. bellii, influenced the primary sex ratio of B. tabaci. This method may assist in population studies of whiteflies, or in determining if sex allocation exists with certain environmental stimuli.

Determining the Egg Fertilization Rate of Bemisia tabaci Using a Cytogenetic Technique

We present a simple cytogenetic technique using 4&#8242;,6-diamidino-2-phenylindole (DAPI) to determine the fertilization rate and primary sex ratio of the haplodiploid invasive pest Bemisia tabaci.

A few species of sap-sucking whiteflies are some of the most damaging terrestrial pests worldwide because of the crop damage they inflict and plant ...

In vivo Application of the REMOTE-control System for the Manipulation of Endogenous Gene Expression

Here we describe a protocol for implementing the REMOTE-control system (Reversible Manipulation of Transcription at Endogenous loci), which allows for reversible and tunable expression control of an endogenous gene of interest in living model systems. The REMOTE-control system employs enhanced lac repression and tet activation systems to achieve down- or upregulation of a target gene within a single biological system. Tight repression can be achieved from repressor binding sites flexibly located far downstream of a transcription start site by inhibiting transcription elongation. Robust upregulation can be attained by enhancing the transcription of an endogenous gene by targeting tet transcriptional activators to the cognate promoter. This reversible and tunable expression control can be applied and withdrawn repeatedly in organisms. The potency and versatility of the system, as demonstrated for endogenous Dnmt1 here, will allow more precise in vivo functional analyses by enabling investigation of gene function at various expression levels and by testing the reversibility of a phenotype.

This protocol outlines the steps needed to generate a model system in which the transcription of an endogenous gene of interest can be conditionally controlled in live animals or cells using enhanced lac repressor and/or tet activator systems.

Here we describe a protocol for implementing the REMOTE-control system (Reversible Manipulation of Transcription at Endogenous loci), which allows for ...

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila

Advances in sequencing technology have made whole-genome and whole-exome datasets more accessible for both clinical diagnosis and cutting-edge human genetics research. Although a number of in silico algorithms have been developed to predict the pathogenicity of variants identified in these datasets, functional studies are critical to determining how specific genomic variants affect protein function, especially for missense variants. In the Undiagnosed Diseases Network (UDN) and other rare disease research consortia, model organisms (MO) including Drosophila, C. elegans, zebrafish, and mice are actively used to assess the function of putative human disease-causing variants. This protocol describes a method for the functional assessment of rare human variants used in the Model Organisms Screening Center Drosophila Core of the UDN. The workflow begins with gathering human and MO information from multiple public databases, using the MARRVEL web resource to assess whether the variant is likely to contribute to a patient&#39;s condition as well as design effective experiments based on available knowledge and resources. Next, genetic tools (e.g., T2A-GAL4 and UAS-human cDNA lines) are generated to assess the functions of variants of interest in Drosophila. Upon development of these reagents, two-pronged functional assays based on rescue and overexpression experiments can be performed to assess variant function. In the rescue branch, the endogenous fly genes are &#34;humanized&#34;&#160;by replacing the orthologous Drosophila gene with reference or variant human transgenes. In the overexpression branch, the reference and variant human proteins are exogenously driven in a variety of tissues. In both cases, any scorable phenotype (e.g., lethality, eye morphology, electrophysiology) can be used as a read-out, irrespective of the disease of interest. Differences observed between reference and variant alleles suggest a variant-specific effect, and thus likely pathogenicity. This protocol allows rapid, in vivo assessments of putative human disease-causing variants of genes with known and unknown functions.

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila

The goal of this protocol is to outline the design and performance of in vivo experiments in Drosophila melanogaster to assess the functional consequences of rare gene variants associated with human diseases.

Advances in sequencing technology have made whole-genome and whole-exome datasets more accessible for both clinical diagnosis and cutting-edge human ...