Name: generating crispr/cas9 mediated monoallelic deletions to study enhancer function in mouse embryonic stem cells
Uploaded: 2016-04-02T14:00:00
Description: Watch this Scientific Journal Video about Generating CRISPR/Cas9 Mediated Monoallelic Deletions to Study Enhancer Function in Mouse Embryonic Stem Cells at JoVE.com

We would like to thank all the members of the Mitchell lab for helpful discussions. This work was supported by the Canadian Institutes of Health Research, the Canada Foundation for Innovation and the Ontario Ministry of Research and Innovation (operating and infrastructure grants held by JAM).

1. Designing and Constructing the gRNA
<ol>
	<li>To delete transcriptional enhancer regions use two gRNAs, one 5&#39; and one 3&#39; of the region of interest. Use the mouse UCSC genome browser track generated by the Zhang laboratory to identify unique gRNA sequences (http://www.genome-engineering.org15). Next check these gRNAs and their adjacent PAM for SNPs and indels using online tools provided by the Sanger Institute (www.sanger.ac.uk/sanger/Mouse_SnpViewer/rel-1211)27-28. To target both allel...

<ol>
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CRISPR/Cas9 mediated genome editing technology provides a straightforward, fast and inexpensive method for genome modification. The method detailed here to generate and analyze monoallelic enhancer deletion for functional enhancer characterization takes advantage of SNPs in F1 mouse cells. The advantages of this type of approach are: 1) monoallelic enhancer deletions do not produce confounding effects that occur when a critical enhancer is deleted from both alleles, i.e., a great reduction in the protein levels ...

Transcriptional regulatory elements are critical for spatio-temporal fine tuning of gene expression during development1 and modification of these elements can result in disease due to aberrant gene expression2. Many disease-associated regions identified by genome wide association studies are in non-coding regions and have features of transcriptional enhancers3-4. Identifying enhancers and matching them with the genes they regulate is complicated as they are often located several kilobases away from the genes they regulate and may be activated in a tissue-specific manner5-6. Enhancer predictions are commonly based on histone modification marks, mediator-cohesin complexes and binding of cell type-specific transcription factors7-10. Validation of predicted enhancers is most often done through a vector based assay in which the enhancer activates expression of a reporter gene11-12. These data provide valuable information about the regulatory potential of putative enhancer sequences but do not reveal their function in their endogenous genomic context or identify the genes they regulate. Genome editing serves as a powerful tool to study the function of transcriptional regulatory elements in their endogenous context by loss-of-function analysis.
Recent advances in genome editing, namely the CRISPR/Cas9 genome editing system, facilitate the investigation of genome function. The CRISPR/Cas9 system is easy to use and adaptable for many biological systems. The Cas9 protein is targeted to a specific site in the genome by a guide RNA (gRNA)13. The SpCas9/gRNA complex scans the genome for its target genomic sequence which must be 5&#39; to a protospacer adjacent motif (PAM) sequence, NGG14-15. Base pairing of the gRNA to its target, a 20 nucleotide (nt) sequence complementary to the gRNA, activates SpCas9 nuclease activity resulting in a double strand break (DSB) 3 bp upstream of the PAM sequence. Specificity is achieved through complete base pairing in the gRNA seed region, the 6-12 nt adjacent to the PAM; conversely, mismatches 5&#39; of the seed are usually tolerated16-17. The introduced DSB can be repaired either by the non-homologous end joining (NHEJ) DNA repair or homology directed repair (HDR) mechanisms.NHEJ DNA repair often creates insertion/deletion (indels) of a few bp at the target site that can disrupt the open reading frame (ORF) of a gene. To generate larger deletions in the genome two gRNAs, which flank the region of interest, can be used18-19. This approach is particularly useful for the study of transcriptional enhancers clustered into locus control regions or super-enhancers which are larger than conventional enhancers9,18,20-22.
Monoallelic deletions are a valuable model for studying cis-regulation of transcription. The observed change in transcript level after monoallelic deletion of an enhancer correlates to the role of that enhancer in gene regulation without the confounding effects that can occur when transcription of both alleles is affected potentially influencing cellular fitness. Evaluating reduced expression is difficult however without the ability to distinguish the deleted from the wild type allele. Furthermore, genotyping deletions at each allele without the ability to distinguish the two alleles is challenging, especially for large deletions of &#62;10 kb to 1 Mb23 in which it is difficult to amplify the entire wild type region by PCR. The use of F1 ES cells generated by crossing Mus musculus129 with Mus castaneus allows the two alleles to be differentiated by allele-specific PCR18,24. The hybrid genome in these cells facilitates allele specific deletion screening and expression analysis. On average there is a SNP every 125 bp between these two genomes, providing flexibility in primer design for expression and genotyping analyses. The presence of one SNP can influence the primer melting temperature (Tm) and target specificity in real-time quantitative PCR (qPCR) amplification allowing for discrimination of the two alleles25. Furthermore a mismatch within the 3&#39; end of the primer greatly influences the ability of DNA polymerase to extend from the primer preventing amplification of the undesired allele target26. Described in the following protocol is the use of F1 ES cells for allele specific enhancer deletions of greater than 1 kb and subsequent expression analysis using the CRISPR/Cas9 genome editing system (Figure 1).
<img alt="Figure 1" src="/files/ftp_upload/53552/53552fig1.jpg" /> 
Figure 1. Enhancer deletion using CRISPR/Cas9 to study cis-regulation of gene expression. (A) F1 ES cells generated by a cross between Mus musculus129 and Mus castaneus are used to allow for allele specific deletion. (B) Two guide RNAs (gRNA) are used to induce a large Cas9-mediated deletion of the enhancer region. (C) Primer sets are used to identify large mono- and bi-allelic deletions. The orange primers are the inside primers, the purple primers are the outside primers and the green primers are the gRNA flanking primers. (D) Changes in gene expression are monitored using allele-specific qPCR. RFU denotes relative fluorescence units. <a href="https://www.jove.com/files/ftp_upload/53552/53552fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table border="0" cellpadding="0" cellspacing="0" width="966">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:253px;">Phusion High-Fidelity DNA Polymerase</td>
			<td style="width:200px;">NEB</td>
			<td style="width:119px;">M0530S</td>
			<td style="width:395px;">high fidelity DNA polymerase used in gRNA assembly</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Gibson Assembly Master Mix</td>
			<td style="width:200px;">NEB</td>
			<td>E2611L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">gRNA_Cloning Vector</td>
			<td style="width:200px;">Addgene</td>
			<td style="width:119px;">41824</td>
			<td>A target sequence is cloned into this vector to create the gRNA plasmid</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">pCas9_GFP</td>
			<td style="width:200px;">Addgene</td>
			<td style="width:119px;">44719</td>
			<td>Codon-optimized SpCas9 and EGFP co-expression plasmid</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">AflII</td>
			<td style="width:200px;">NEB</td>
			<td style="width:119px;">R0520S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">EcoRI</td>
			<td style="width:200px;">NEB</td>
			<td style="width:119px;">R3101S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Neon Transfection System 100 &#181;L Kit</td>
			<td style="width:200px;">Life Technologies</td>
			<td style="width:119px;">MPK10096</td>
			<td>Microporator transfection technology</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">prepGEM</td>
			<td style="width:200px;">ZyGEM</td>
			<td style="width:119px;">PT10500</td>
			<td>genomic DNA extraction reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Nucleo Spin Gel &#38; PCR Clean-up</td>
			<td style="width:200px;">Macherey-Nagel</td>
			<td style="width:119px;">740609.5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">High-Speed Plasmid Mini Kit</td>
			<td style="width:200px;">Geneaid</td>
			<td style="width:119px;">PD300</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Maxi Plasmid Kit Endotoxin Free&#160;</td>
			<td style="width:200px;">Geneaid</td>
			<td style="width:119px;">PME25</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">SYBR select mix for CFX</td>
			<td style="width:200px;">Life Technologies</td>
			<td style="width:119px;">4472942</td>
			<td>qPCR reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">iScript cDNA synthesis kit</td>
			<td style="width:200px;">Bio-rad</td>
			<td style="width:119px;">170-8891</td>
			<td>Reverse transcription reagent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">0.25% Trypsin with EDTA</td>
			<td style="width:200px;">Life Technologies</td>
			<td style="width:119px;">25200072</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:253px;">PBS without Ca/Mg2+</td>
			<td style="width:200px;">Sigma</td>
			<td style="width:119px;">D8537</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">0.5M EDTA</td>
			<td style="width:200px;">Bioshop</td>
			<td style="width:119px;">EDT111.500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">HBSS</td>
			<td style="width:200px;">Life Technologies</td>
			<td style="width:119px;">14175095</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">1M HEPES</td>
			<td style="width:200px;">Life Technologies</td>
			<td style="width:119px;">13630080</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">BSA fraction V (7.5%)</td>
			<td style="width:200px;">Life Technologies</td>
			<td style="width:119px;">15260037</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Max Efficiency DH5&#945; competent cells</td>
			<td style="width:200px;">Invitrogen</td>
			<td style="width:119px;">18258012</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">FBS</td>
			<td style="width:200px;">ES cell qualified</td>
			<td style="width:119px;"></td>
			<td>FBS is subjected to a prior testing in mouse ES cells for pluripotency</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">DMSO</td>
			<td style="width:200px;">Sigma</td>
			<td style="width:119px;">D2650</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Glutamax</td>
			<td style="width:200px;">Invitrogen</td>
			<td style="width:119px;">35050</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">DMEM</td>
			<td style="width:200px;">Life Technologies</td>
			<td style="width:119px;">11960069</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Pencillin/Streptomycin</td>
			<td style="width:200px;">Invitrogen</td>
			<td style="width:119px;">15140</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Sodium pyruvate</td>
			<td style="width:200px;">Invitrogen</td>
			<td style="width:119px;">11360</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Non-essential aminoacid</td>
			<td style="width:200px;">Invitrogen</td>
			<td style="width:119px;">11140</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">&#946;-mercaptoethanol</td>
			<td style="width:200px;">Sigma</td>
			<td style="width:119px;">M7522</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">96-well plate</td>
			<td style="width:200px;">Sarstedt</td>
			<td style="width:119px;">83.3924</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">Sealing tape</td>
			<td style="width:200px;">Sarstedt</td>
			<td style="width:119px;">95.1994</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">CoolCell LX</td>
			<td style="width:200px;">Biocision</td>
			<td style="width:119px;">BCS-405</td>
			<td>alcohol-free cell freezing container</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">CHIR99021</td>
			<td style="width:200px;">Biovision</td>
			<td style="width:119px;">1748-5</td>
			<td>Inhibitor for F1 ES cell culture</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">PD0325901</td>
			<td style="width:200px;">Invivogen</td>
			<td style="width:119px;">inh-pd32</td>
			<td>Inhibitor for F1 ES cell culture</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:253px;">LIF</td>
			<td style="width:200px;">Chemicon</td>
			<td style="width:119px;">ESG1107</td>
			<td>Inhibitor for F1 ES cell culture</td>
		</tr>
	</tbody>
</table>

generating crispr/cas9 mediated monoallelic deletions to study enhancer function in mouse embryonic stem cells

Enhancers control cell identity by regulating tissue-specific gene expression in a position and orientation independent manner. These enhancers are often located distally from the regulated gene in intergenic regions or even within the body of another gene. The position independent nature of enhancer activity makes it difficult to match enhancers with the genes they regulate. Deletion of an enhancer region provides direct evidence for enhancer activity and is the gold standard to reveal an enhancer's role in endogenous gene transcription. Conventional homologous recombination based deletion methods have been surpassed by recent advances in genome editing technology which enable rapid and precisely located changes to the genomes of numerous model organisms. CRISPR/Cas9 mediated genome editing can be used to manipulate the genome in many cell types and organisms rapidly and cost effectively, due to the ease with which Cas9 can be targeted to the genome by a guide RNA from a bespoke expression plasmid. Homozygous deletion of essential gene regulatory elements might lead to lethality or alter cellular phenotype whereas monoallelic deletion of transcriptional enhancers allows for the study of cis-regulation of gene expression without this confounding issue. Presented here is a protocol for CRISPR/Cas9 mediated deletion in F1 mouse embryonic stem (ES) cells (Mus musculus129 x Mus castaneus). Monoallelic deletion, screening and expression analysis is facilitated by single nucleotide polymorphisms (SNP) between the two alleles which occur on average every 125 bp in these cells.

The protocol described here uses F1 ES cells to study cis-regulation of gene expression in monoallelic enhancer deleted cells generated using CRISPR/Cas9 genome editing (Figure 1). The gRNA and allele-specific primer design for genotyping and gene expression are the key factors in this approach. Each allele-specific primer set must be validated by qPCR to confirm allele specificity. Allele-specific primers that amplify only their respective genomic DNA target are...

Watch this Scientific Journal Video about Generating CRISPR/Cas9 Mediated Monoallelic Deletions to Study Enhancer Function in Mouse Embryonic Stem Cells at JoVE.com

Generating CRISPR/Cas9 Mediated Monoallelic Deletions to Study Enhancer Function in Mouse Embryonic Stem Cells (Video) | JoVE

Experimental validation of enhancer activity is best approached by loss-of-function analysis. Presented here is an efficient protocol that uses CRISPR/Cas9 mediated deletion to study allele-specific regulation of gene transcription in F1 ES cells which contain a hybrid genome (Mus musculus129 x Mus castaneus).

Generating CRISPR/Cas9 Mediated Monoallelic Deletions to Study Enhancer Function in Mouse Embryonic Stem Cells

Enhancers control cell identity by regulating tissue-specific gene expression in a position and orientation independent manner. These enhancers are often ...

Research

JoVE Journal

Developmental Biology

Neural Differentiation of Mouse Embryonic Stem Cells in Serum-free Monolayer Culture

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Structure-function Studies in Mouse Embryonic Stem Cells Using Recombinase-mediated Cassette Exchange

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Gene engineering in mouse embryos or embryonic stem cells (mESCs) allows for the study of the function of a given protein. Proteins are the workhorses of ...

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The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and ...

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Duchenne muscular dystrophy (DMD) is a severe progressive muscle disease caused by mutations in the dystrophin gene, which ultimately leads to the ...

Assessment of Oxidative Damage in the Primary Mouse Ocular Surface Cells/Stem Cells in Response to Ultraviolet-C (UV-C) Damage

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The ocular surface is subjected to regular wear and tear due to various environmental factors. Exposure to UV-C radiation constitutes an occupational ...

A Static Self-Directed Method for Generating Brain Organoids from Human Embryonic Stem Cells

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Human brain organoids differentiated from embryonic stem cells offer the unique opportunity to study complicated interactions of multiple cell types in a ...

Accurate Follicle Enumeration in Adult Mouse Ovaries

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Sexually reproducing female mammals are born with their entire lifetime supply of oocytes. Immature, quiescent oocytes are found within primordial ...

Application of Mouse Parthenogenetic Haploid Embryonic Stem Cells as a Substitute of Sperm

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In organisms with sexual reproduction, germ cells are the source of totipotent cells that develop into new individuals. In mice, fertilization of an ...