Name: identification of homologous recombination events in mouse embryonic stem cells using southern blotting and polymerase chain reaction
Uploaded: 2018-11-20T13:30:00
Description: Watch this Scientific Journal Video about Identification of Homologous Recombination Events in Mouse Embryonic Stem Cells Using Southern Blotting and Polymerase Chain Reaction at JoVE.com

This work received support from the General Program of National Natural Science Foundation of China (Grants No. 31571432), the Human Provincial Natural Science Foundation of China (Grant No. 2015JC3097), and the Research Foundation of Education Bureau of Hunan Province, China (Grant No. 15K054).

1. Design of Targeting Construct(s), Probes for Southern Blot, and Primers for PCR
<ol>
	<li>Select the first coding exon (exon 2) of the Myh9 gene for disruption or insertion in the application of knockout/knock-in reported here.</li>
	<li>Retrieve the 5-kb upstream and 5-kb downstream DNA sequences surrounding the Myh9 exon 2 from the genome.ucsc.edu website.</li>
	<li>Analyze restriction digestion patterns of enzymes (REs) with 1&#8211;2 cuts in this 10-kb region by using pDRAW software to determine...

<ol>
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Currently, designer nucleases for genome editing still cannot replace ES cell-based gene-targeting technology due to its issues of off-target effects, and difficulty in inserting a long DNA fragment30,31. As the golden methods for identifying HR events that occurred in mouse ES cells, this report provides a detailed protocol of Southern blotting and PCR for the field. We validated the reliability of these methods by analyzing individual clones from mouse ES cells...

The technology of gene targeting by HR in murine ES cells provides a powerful tool for dissecting the cellular consequences of specific genetic mutations1,2. The importance and significance of this technology are reflected in its recognition by the 2007 Nobel Prize in Physiology or Medicine3,4; meanwhile, it represents the advent of the modern era of gene engineering5. Gene targeting through HR can be utilized to engineer virtually any alteration ranging from point mutations to large chromosomal rearrangements in the genome of mouse ES cells6,7. It is well known that, before the emergence of so-called genome editing tools, the generation of a gene knockout mouse required the application of gene-targeting technology in ES cells8,9,10. During the past two decades, more than 5,000 gene-targeted mice were produced by this approach for modeling human diseases or studying gene functions11. A genome-wide knockout effort has been established for distributing gene-targeting vectors, targeted ES cell clones, and live mice to the scientific community2,12,13,14,15. Undoubtedly, ES cell-based HR-mediated gene-targeting technology has greatly advanced our understanding of the functions of genes played in physiological or pathological context.
Because HR is a relatively infrequent event in mammalian cells16,17, the important and next step following gene targeting in murine ES cells is to analyze numerous ES colonies for identifying a few clones with mutations resulting from HR with the targeting vector18. The gold methods for identifying HR events include Southern blotting and PCR19,20. The advantages of the approaches include that Southern blotting can identify correctly targeted ES clones and allows researchers to analyze the structure of the gene-targeted event, such as a verification of a single copy insertion of the construct, while a PCR-based strategy permits more rapid screening for HR events21,22. Though these methods have drawbacks, such as that they are time-consuming and can have false positives, the combinational usage of them is widely accepted and applied by most labs in identifying HR events, particular in ES cells, for generating genetically modified animals.
Three isoforms of nonmuscle myosin II (NM II) in mammals, each consisting of two identical NMHC IIs which are encoded by three different genes (named Myh9, Myh10, and Myh14) and two pairs of light chains, are referred to as NM II-A, II-B, and II-C23. Previous studies have indicated that at least the isoforms of NM II-A and II-B are essential for mouse development because the in vivo ablation of these isoforms results in embryonic lethality24,25,26. To circumvent this problem and obtain novel insights into the isoform-specific functions of NM II-A and II-B in the later stages of mouse development, a genetic replacement strategy using ES cell-based HR-mediated gene-targeting technology was adopted to generate a series of mouse models27. In the course of identifying the desired ES clones, both Southern blotting and PCR methods were utilized, and these proved to be efficient and reliable27,28.
This paper intends to provide a detailed description of Southern blotting and PCR, including the design of targeting vector(s), probe(s), and primers, and the execution of experiments, as well as the analysis of results exemplified by identifying HR event occurrence in ES cells for creating genetic replacement NM II mouse models and representative data. The protocols of these two methods presented here can also be adopted for identifying the genotypes of genetically modified cells or animals.

<table border="0" cellpadding="0" cellspacing="0" style="width:903px;" width="903">
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		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:391px;">BAC CLONE</td>
			<td style="width:232px;">BACPAC Resources Center (BPRC)</td>
			<td style="width:113px;">bMQ-330E21</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">QIAGEN Large-Construct Kit</td>
			<td style="width:232px;">QIAGEN</td>
			<td align="right">12462</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">QIAquick Gel Extraction Kit</td>
			<td style="width:232px;">QIAGEN</td>
			<td align="right" style="width:113px;">28704</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">QIAquick PCR Purification Kit</td>
			<td style="width:232px;">QIAGEN</td>
			<td align="right" style="width:113px;">28104</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">QIAprep Spin Miniprep Kit</td>
			<td style="width:232px;">QIAGEN</td>
			<td align="right" style="width:113px;">27104</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">QIAGEN Plasmid Plus Maxi Kit</td>
			<td style="width:232px;">QIAGEN</td>
			<td align="right" style="width:113px;">12963</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">PfuUltra High-Fidelity DNA Polymerase</td>
			<td style="width:232px;">Agilent</td>
			<td align="right" style="width:113px;">600382</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:391px;">T-easy vector</td>
			<td style="width:232px;">Promega</td>
			<td style="width:113px;">A1360</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:391px;">Nuclei Lysis Solution</td>
			<td style="width:232px;">Promega</td>
			<td style="width:113px;">A7941</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Protein Precipitation Solution</td>
			<td style="width:232px;">Promega</td>
			<td>A7951</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNA Denaturing Solution</td>
			<td style="width:232px;">VWR</td>
			<td>351-013-131</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNA Neutralizing Solution</td>
			<td style="width:232px;">VWR</td>
			<td>351-014-131</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ready-To-Go DNA Labeling Beads (-dCTP)</td>
			<td style="width:232px;">VWR</td>
			<td>27-9240-01</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">UltraPure SSC, 20X</td>
			<td style="width:232px;">Thermo Fisher</td>
			<td align="right">15557036</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">UltraPur Phenol:Chloroform:Isoamyl Alcohol (25:24:1, v/v)</td>
			<td style="width:232px;">Thermo Fisher</td>
			<td align="right">15593031</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">G418</td>
			<td style="width:232px;">Thermo Fisher</td>
			<td align="right">10131035</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Salmon Sperm DNA Solution</td>
			<td style="width:232px;">Thermo Fisher</td>
			<td align="right">15632011</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Platinu Taq DNA Polymerase High Fidelity</td>
			<td style="width:232px;">Thermo Fisher</td>
			<td align="right">11304029</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:391px;">Not I</td>
			<td>Thermo Scientific</td>
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identification of homologous recombination events in mouse embryonic stem cells using southern blotting and polymerase chain reaction

Relative to the issues of off-target effects and the difficulty of inserting a long DNA fragment in the application of designer nucleases for genome editing, embryonic stem (ES) cell-based gene-targeting technology does not have these shortcomings and is widely used to modify animal/mouse genome ranging from large deletions/insertions to single nucleotide substitutions. Notably, identifying the relatively few homologous recombination (HR) events necessary to obtain desired ES clones is a key step, which demands accurate and reliable methods. Southern blotting and/or conventional PCR are often utilized for this purpose. Here, we describe the detailed procedures of using those two methods to identify HR events that occurred in mouse ES cells in which the endogenous Myh9 gene is intended to be disrupted and replaced by cDNAs encoding other nonmuscle myosin heavy chain IIs (NMHC IIs). The whole procedure of Southern blotting includes the construction of targeting vector(s), electroporation, drug selection, the expansion and storage of ES cells/clones, the preparation, digestion, and blotting of genomic DNA (gDNA), the hybridization and washing of probe(s), and a final step of autoradiography on the X-ray films. PCR can be performed directly with prepared and diluted gDNA. To obtain ideal results, the probes and restriction enzyme (RE) cutting sites for Southern blotting and the primers for PCR should be carefully planned. Though the execution of Southern blotting is time-consuming and labor-intensive and PCR results have false positives, the correct identification by Southern blotting and the rapid screening by PCR allow the sole or combined application of these methods described in this paper to be widely used and consulted by most labs in the identification of genotypes of ES cells and genetically modified animals.

In this paper, a detailed protocol of Southern blotting and PCR is described, which is utilized to identify HR events that occurred in mouse ES cells for the generation of NM II genetic replacement mouse models, using ES cells-based HR-mediated targeting technology. Though Southern blotting and PCR, as well as traditional gene-targeting technology, have been widely used for several decades, the successful application of them needs to be planned carefully. At least these aspects are requir...

Watch this Scientific Journal Video about Identification of Homologous Recombination Events in Mouse Embryonic Stem Cells Using Southern Blotting and Polymerase Chain Reaction at JoVE.com

Identification of Homologous Recombination Events in Mouse Embryonic Stem Cells Using Southern Blotting and Polymerase Chain Reaction

Here, we present a detailed protocol for identifying homologous recombination events that occurred in mouse embryonic stem cells using Southern blotting and/or PCR. This method is exemplified by the generation of nonmuscle myosin II genetic replacement mouse models using traditional embryonic stem cell-based homologous recombination-mediated targeting technology.

Relative to the issues of off-target effects and the difficulty of inserting a long DNA fragment in the application of designer nucleases for genome ...

This method can help answer key questions in molecular and cellular biology field, such as identifying homologous recombination events in mouse embryonic stem cells. The main advantage of this technique is that it is accurate, reliable, and widely used. So, this method can provide insight into identifying homologous recombination events in mouse embryonic stem cell.It can also be applied to other systems, such as genetically modified cell or animals. Generally, individual new to this method will struggle because it take long time and involves multiple steps. For each gDNA, mix 30 microliters of 10 x buffer for DRA one, three microliters of DRA one and 10 micrograms of gDNAs per sample.Add water until the final volume is 30 microliters, and incubate at 37 degrees celsius overnight to digest the gDNAs. Prepare a 1%agarose electrophoresis gel with ethidium bromide. Load the previously acquired samples along with a one KB ladder onto the gel, and run it at 30 to 40 volts overnight.The next day, soak the gel in a tray containing a 0.2 newton hydrochloric acid solution. Use a shaker to shake the tray gently for 20 minutes at room temperature. Transfer the gel to a tray containing a DNA denaturing solution.Shake it gently for 20 minutes at room temperature. Then transfer the gel into a tray containing a DNA neutralizing solution. And shake it gently for 20 minutes at room temperature.Using a rapid downward transfer system, transfer the DNAs from the gel to the membrane. Next, assemble the turble blotter and blotting stack as outlined in the instructions provided by the manufacturer. After this, take out the membrane and wash it with two X saline sodium citrate for one minute.Absorb the liquid with tissues, and then use a UV crosslinker to cross link the DNA with the membrane. To begin labeling the DNA probes with radioactivity, add the heat denatured probe DNAs to the tube containing the ready to go DNA labeling beads. Pipette up and down to mix.And add five microliters of radioactively labeled deoxycytodine triphosphate. Incubate at 37 degrees celsius for 15 minutes. Purify the labeled probes by using G 50 micro columns according to the instructions provided by the manufacturer.Use a scintillation counter to measure the radioactivity. To begin hybridizing the membranes with the labeled probes, place the membrane into the hybridization tube. Add the mixed pre hybridization solution.Place the tube into hybridization oven and let the pre hybridization proceed at 42 degrees celsius for 30 minutes. Then, remove the tube from the oven and pour the pre hybridization solution into a 50 milliliter tube. Add the denatured probe, and mix gently.To remove the non hybridized probes, place the membrane into a tray containing one X saline sodium citrate with 0.1%SDS and shake gently at 55 to 60 degrees celsius for 10 minutes. After this, wrap the membrane with plastic wrap and fix it in the exposure cassette. In a dark room, expose the membrane to two sheets of X ray film.Develop the film to visualize the results. Determine if a corresponding ES clone is the desired one with the target of recombination or not, according to the sizes of the DNA bands detected by the probes. In this study, southern blotting and PCR is utilized to identify HR events that occur in mouse ES cells for the generation of NM two genetic replacement mouse models using ES cells based HR mediated targeting technology.Because the genomic DNAs are cut into many fragments with different lengths, they display a smear like status on the DNA gel. This suggests a complete digestion of the genomic DNAs. As a final step of southern blotting, the signals of a radioactivity labeled probe hybridizing with a target DNA fragment are shown on the film.The appearance of expected bands reflects the occurrence of HR events in the ES clones. According to the predesign in the study, ES clones with mutated allele have two distinct size bands. While wild type ES clones only have one band, suggesting the desired ES clones are heterozygous.Following the PCR reaction, the PCR products can be analyzed on the DNA gel. If a specific NPCR band of the correct size is observed, this suggests the occurrence of HR events which can be further confirmed by sequencing that PCR band. The implication of this technique extended to the therapy of identifying point mutation because the foundation is identical.While attempting this procedure is important to remember to be patient and careful. Following this procedure, other method like microinjection of ES cell into blastocysts can be performed in order to answer additional question like there formation of chimeric animals. Aft its development, this technique paved the way for the researcher in their field of molecular and cellular biology to explore the function of a specific gene or the consequence of a mutated gene in mice or beyond.Don't forget that working with radioactivity labeler P32 DCTB can be extremely hazardous and precautions such as shielding with protection board should be always be taking while performing this procedure.

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Improved Polymerase Chain Reaction-restriction Fragment Length Polymorphism Genotyping of Toxic Pufferfish by Liquid Chromatography/Mass Spectrometry

An improved version of a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method for genotyping toxic pufferfish species by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) is described. DNA extraction is carried out using a silica membrane-based DNA extraction kit. After the PCR amplification using a detergent-free PCR buffer, restriction enzymes are added to the solution without purifying the reaction solution. A reverse-phase silica monolith column and a Fourier transform high resolution mass spectrometer having a modified Kingdon trap analyzer are employed for separation and detection, respectively. The mobile phase, consisting of 400 mM 1,1,1,3,3,3-hexafluoro-2-propanol, 15 mM triethylamine (pH 7.9) and methanol, is delivered at a flow rate of 0.4 ml/min. The cycle time for LC/ESI-MS analysis is 8 min including equilibration of the column. Deconvolution software having an isotope distribution model of the oligonucleotide is used to calculate the corresponding monoisotopic mass from the mass spectrum. For analysis of oligonucleotides (range 26-79 nucleotides), mass accuracy was 0.62 &#177; 0.74 ppm (n = 280) and excellent accuracy and precision were sustained for 180 hr without use of a lock mass standard.

An improved polymerase chain reaction-restriction fragment length polymorphism method for genotyping pufferfish species by liquid chromatography/mass spectrometry is described. A reverse-phase silica monolith column is employed for separating digested amplicons. This method can elucidate the monoisotopic masses of oligonucleotides, which is useful for identifying base composition.

An improved version of a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method for genotyping toxic pufferfish species by ...

Semi-quantitative Detection of RNA-dependent RNA Polymerase Activity of Human Telomerase Reverse Transcriptase Protein

Human telomerase reverse transcriptase (TERT) is the catalytic subunit of telomerase, and it elongates telomere through RNA-dependent DNA polymerase activity. Although TERT is named as a reverse transcriptase, structural and phylogenetic analyses of TERT demonstrate that TERT is a member of right-handed polymerases, and relates to viral RNA-dependent RNA polymerases (RdRPs) as well as viral reverse transcriptase. We firstly identified RdRP activity of human TERT that generates complementary RNA stand to a template non-coding RNA and contributes to RNA silencing in cancer cells. To analyze this non-canonical enzymatic activity, we developed RdRP assay with recombinant TERT in 2009, thereafter established in vitro RdRP assay for endogenous TERT. In this manuscript, we describe the latter method. Briefly, TERT immune complexes are isolated from cells, and incubated with template RNA and rNTPs including radioactive rNTP for RdRP reaction. To eliminate single-stranded RNA, reaction products are treated with RNase I, and the final products are analyzed with polyacrylamide gel electrophoresis. Radiolabeled RdRP products can be detected by autoradiography after overnight exposure.

Human telomerase reverse transcriptase (TERT) synthesizes not only telomeric DNA but also double-stranded RNA through RNA-dependent RNA polymerase activity. Here, we describe a newly established assay to detect RNA-dependent RNA polymerase activity of endogenous TERT.

Human telomerase reverse transcriptase (TERT) is the catalytic subunit of telomerase, and it elongates telomere through RNA-dependent DNA polymerase ...

Highly Efficient Gene Disruption of Murine and Human Hematopoietic Progenitor Cells by CRISPR/Cas9

Advances in the hematopoietic stem cell (HSCs) field have been aided by methods to genetically engineer primary progenitor cells as well as animal models. Complete gene ablation in HSCs required the generation of knockout mice from which HSCs could be isolated, and gene ablation in primary human HSCs was not possible. Viral transduction could be used for knock-down approaches, but these suffered from variable efficacy. In general, genetic manipulation of human and mouse hematopoietic cells was hampered by low efficiencies and extensive time and cost commitments. Recently, CRISPR/Cas9 has dramatically expanded the ability to engineer the DNA of mammalian cells. However, the application of CRISPR/Cas9 to hematopoietic cells has been challenging, mainly due to their low transfection efficiencies, the toxicity of plasmid-based approaches and the slow turnaround time of virus-based protocols.
A rapid method to perform CRISPR/Cas9-mediated gene editing in murine and human hematopoietic stem and progenitor cells with knockout efficiencies of up to 90% is provided in this article. This approach utilizes a ribonucleoprotein (RNP) delivery strategy with a streamlined three-day workflow. The use of Cas9-sgRNA RNP allows for a hit-and-run approach, introducing no exogenous DNA sequences in the genome of edited cells and reducing off-target effects. The RNP-based method is fast and straightforward: it does not require cloning of sgRNAs, virus preparation or specific sgRNA chemical modification. With this protocol, scientists should be able to successfully generate knockouts of a gene of interest in primary hematopoietic cells within a week, including downtimes for oligonucleotide synthesis. This approach will allow a much broader group of users to adapt this protocol for their needs.

A protocol for fast CRISPR/Cas9-mediated gene disruption in mouse and human primary hematopoietic cells is described in this article. Cas9-sgRNA ribonucleoproteins are introduced via electroporation with sgRNAs generated through in vitro transcription and commercial Cas9. High editing efficiencies are achieved with limited time and financial cost.

Advances in the hematopoietic stem cell (HSCs) field have been aided by methods to genetically engineer primary progenitor cells as well as animal models. ...

CRISPR-Mediated Reorganization of Chromatin Loop Structure

Recent studies have clearly shown that long-range, three-dimensional chromatin looping interactions play a significant role in the regulation of gene expression, but whether looping is responsible for or a result of alterations in gene expression is still unknown. Until recently, how chromatin looping affects the regulation of gene activity and cellular function has been relatively ambiguous, and limitations in existing methods to manipulate these structures prevented in-depth exploration of these interactions. To resolve this uncertainty, we engineered a method for selective and reversible chromatin loop re-organization using CRISPR-dCas9 (CLOuD9). The dynamism of the CLOuD9 system has been demonstrated by successful localization of CLOuD9 constructs to target genomic loci to modulate local chromatin conformation. Importantly, the ability to reverse the induced contact and restore the endogenous chromatin conformation has also been confirmed. Modulation of gene expression with this method establishes the capacity to regulate cellular gene expression and underscores the great potential for applications of this technology in creating stable de novo chromatin loops that markedly affect gene expression in the contexts of cancer and development.

Chromatin looping plays a significant role in gene regulation; however, there have been no technological advances that allow for selective and reversible modification of chromatin loops. Here we describe a powerful system for chromatin loop re-organization using CRISPR-dCas9 (CLOuD9), demonstrated to selectively and reversibly modulate gene expression at targeted loci.

Recent studies have clearly shown that long-range, three-dimensional chromatin looping interactions play a significant role in the regulation of gene ...

Single Droplet Digital Polymerase Chain Reaction for Comprehensive and Simultaneous Detection of Mutations in Hotspot Regions

Droplet digital polymerase chain reaction (ddPCR) is a highly sensitive quantitative polymerase chain reaction (PCR) method based on sample fractionation into thousands of nano-sized water-in-oil individual reactions. Recently, ddPCR has become one of the most accurate and sensitive tools for circulating tumor DNA (ctDNA) detection. One of the major limitations of the standard ddPCR technique is the restricted number of mutations that can be screened per reaction, as specific hydrolysis probes recognizing each possible allelic version are required. An alternative methodology, the drop-off ddPCR, increases throughput, since it requires only a single pair of probes to detect and quantify potentially all genetic alterations in the targeted region. Drop-off ddPCR displays comparable sensitivity to conventional ddPCR assays with the advantage of detecting a greater number of mutations in a single reaction. It is cost-effective, conserves precious sample material, and can also be used as a discovery tool when mutations are not known a priori.

Here, we present a protocol to accurately quantify multiple genetic alterations of a target region in a single reaction using drop-off ddPCR and a unique pair of hydrolysis probes.

Droplet digital polymerase chain reaction (ddPCR) is a highly sensitive quantitative polymerase chain reaction (PCR) method based on sample fractionation ...

Endogenous Protein Tagging in Human Induced Pluripotent Stem Cells Using CRISPR/Cas9

A protocol is presented for generating human induced pluripotent stem cells (hiPSCs) that express endogenous proteins fused to in-frame&#160;N- or C-terminal fluorescent tags. The prokaryotic CRISPR/Cas9 system (clustered regularly interspaced short palindromic repeats/CRISPR-associated 9) may be used to introduce large exogenous sequences into genomic loci via homology directed repair (HDR). To achieve the desired knock-in, this protocol employs the ribonucleoprotein (RNP)-based approach where wild type Streptococcus pyogenes Cas9 protein, synthetic 2-part guide RNA (gRNA), and a donor template plasmid are delivered to the cells via electroporation. Putatively edited cells expressing the fluorescently tagged proteins are enriched by fluorescence activated cell sorting (FACS). Clonal lines are then generated and can be analyzed for precise editing outcomes. By introducing the fluorescent tag at the genomic locus of the gene of interest, the resulting subcellular localization and dynamics of the fusion protein can be studied under endogenous regulatory control, a key improvement over conventional overexpression systems. The use of hiPSCs as a model system for gene tagging provides the opportunity to study the tagged proteins in diploid, nontransformed cells. Since hiPSCs can be differentiated into multiple cell types, this approach provides the opportunity to create and study tagged proteins in a variety of isogenic cellular contexts.

Described here is a protocol for tagging endogenously expressed proteins with fluorescent tags in human induced pluripotent stem cells using CRISPR/Cas9. Putatively edited cells are enriched by fluorescence activated cell sorting and clonal cell lines are generated.

A protocol is presented for generating human induced pluripotent stem cells (hiPSCs) that express endogenous proteins fused to in-frame&#160;N- or ...

Culturing and Manipulation of O9-1 Neural Crest Cells

Neural crest cells (NCCs) are migrating multipotent stem cells that can differentiate into different cell types and give rise to multiple tissues and organs. The O9-1 cell line is derived from the endogenous mouse embryonic NCCs and maintains its multipotency. However, under specific culture conditions, O9-1 cells can differentiate into different cell types and be utilized in a wide range of research applications. Recently, with the combination of mouse studies and O9-1 cell studies, we have shown that the Hippo signaling pathway effectors Yap and Taz play important roles in neural crest-derived craniofacial development. Although the culturing process for O9-1 cells is more complicated than that used for other cell lines, the O9-1 cell line is a powerful model for investigating NCCs in vitro. Here, we present a protocol for culturing the O9-1 cell line to maintain its stemness, as well as protocols for differentiating O9-1 cells into different cell types, such as smooth muscle cells and osteoblasts. In addition, protocols are described for performing gene loss-of-function studies in O9-1 cells by using CRISPR-Cas9 deletion and small interfering RNA-mediated knockdown.

O9-1 is a multipotent mouse neural crest cell line. Here we describe detailed step-by-step protocols for culturing O9-1 cells, differentiating O9-1 cells into specific cell types, and genetically manipulating O9-1 cells by using siRNA-mediated knockdown or CRISPR-Cas9 genome editing.

Neural crest cells (NCCs) are migrating multipotent stem cells that can differentiate into different cell types and give rise to multiple tissues and ...

Evaluation of a Universal Nested Reverse Transcription Polymerase Chain Reaction for the Detection of Lyssaviruses

To detect rabies virus and other member species of the genus Lyssavirus within the family Rhabdoviridae, the pan-lyssavirus nested reverse transcription polymerase chain reaction (nested RT-PCR) was developed to detect the conserved region of the nucleoprotein (N) gene of lyssaviruses. The method applies reverse transcription (RT) using viral RNA as template and oligo (dT)15 and random hexamers as primers to synthesize the viral complementary DNA (cDNA). Then, the viral cDNA is used as a template to amplify an 845 bp N gene fragment in first-round PCR using outer primers, followed by second-round nested PCR to amplify the final 371 bp fragment using inner primers. This method can detect different genetic clades of rabies viruses (RABV). The validation, using 9,624 brain specimens from eight domestic animal species in 10 years of clinical rabies diagnoses and surveillance in China, showed that the method has 100% sensitivity and 99.97% specificity in comparison with the direct fluorescent antibody test (FAT), the gold standard method recommended by the World Health Organization (WHO) and the World Organization for Animal Health (OIE). In addition, the method could also specifically amplify the targeted N gene fragment of 15 other approved and two novel lyssavirus species in the 10th Report of the International Committee on Taxonomy of Viruses (ICTV) as evaluated by a mimic detection of synthesized N gene plasmids of all lyssaviruses. The method provides a convenient alternative to FAT for rabies diagnosis and has been approved as a National Standard (GB/T36789-2018) of China.

A pan-lyssavirus nested reverse transcription polymerase chain reaction has been developed to detect specifically all known lyssaviruses. Validation using rabies brain samples of different animal species showed that this method has a sensitivity and specificity equivalent to the gold standard fluorescent antibody test and could be used for routine rabies diagnosis.

To detect rabies virus and other member species of the genus Lyssavirus within the family Rhabdoviridae, the pan-lyssavirus nested reverse transcription ...

Artificial RNA Polymerase II Elongation Complexes for Dissecting Co-transcriptional RNA Processing Events

Eukaryotic mRNA synthesis is a complex biochemical process requiring transcription of a DNA template into a precursor RNA by the multi-subunit enzyme RNA polymerase II and co-transcriptional capping and splicing of the precursor RNA to form the mature mRNA. During mRNA synthesis, the RNA polymerase II elongation complex is a target for regulation by a large collection of transcription factors that control its catalytic activity, as well as the capping, splicing, and 3&#8217;-processing enzymes that create the mature mRNA. Because of the inherent complexity of mRNA synthesis, simpler experimental systems enabling isolation and investigation of its various co-transcriptional stages have great utility.
In this article, we describe one such simple experimental system suitable for investigating co-transcriptional RNA capping. This system relies on defined RNA polymerase II elongation complexes assembled from purified polymerase and artificial transcription bubbles. When immobilized via biotinylated DNA, these RNA polymerase II elongation complexes provide an easily manipulable tool for dissecting co-transcriptional RNA capping and mechanisms by which the elongation complex recruits and regulates capping enzyme during co-transcriptional RNA capping. We anticipate this system could be adapted for studying recruitment and/or assembly of proteins or protein complexes with roles in other stages of mRNA maturation coupled to the RNA polymerase II elongation complex.

Here, we describe the assembly of RNA polymerase II (Pol II) elongation complexes requiring only short synthetic DNA and RNA oligonucleotides and purified Pol II. These complexes are useful for studying mechanisms underlying co-transcriptional processing of transcripts associated with the Pol II elongation complex.

Eukaryotic mRNA synthesis is a complex biochemical process requiring transcription of a DNA template into a precursor RNA by the multi-subunit enzyme RNA ...

A Robust Polymerase Chain Reaction-based Assay for Quantifying Cytosine-guanine-guanine Trinucleotide Repeats in Fragile X Mental Retardation-1 Gene

Fragile X syndrome (FXS) and associated disorders are caused by expansion of the cytosine-guanine-guanine (CGG) trinucleotide repeat in the 5&#8217; untranslated region (UTR) of the Fragile X mental retardation-1 (FMR1) gene promoter. Conventionally, capillary electrophoresis fragment analysis on a genetic analyzer is used for the sizing of the CGG repeats of FMR1, but additional Southern blot analysis is required for exact measurement when the repeat number is higher than 200. Here, we present an accurate and robust polymerase chain reaction (PCR)-based method for quantification of the CGG repeats of FMR1. The first step of this test is PCR amplification of the repeat sequences in the 5&#8217;UTR of the FMR1 promoter using a Fragile X PCR kit, followed by purification of the PCR products and fragment sizing on a microfluidic capillary electrophoresis instrument, and subsequent interpretation of the number of CGG repeats by referencing standards with known repeats using the analysis software. This PCR-based assay is reproducible and capable of identifying the full range of CGG repeats of FMR1 promoters, including those with a repeat number of more than 200 (classified as full mutation), 55 to 200 (premutation), 46 to 54 (intermediate), and 10 to 45 (normal). It is a cost-effective method that facilitates classification of the FXS and Fragile X-associated disorders with robustness and rapid reporting time.

An accurate and robust polymerase chain reaction-based assay for quantifying cytosine-guanine-guanine trinucleotide repeats in the Fragile X mental retardation-1 gene facilitates molecular diagnosis and screening of Fragile X syndrome and Fragile X-related disorders with shorter turn-around time and investment in equipment.

Fragile X syndrome (FXS) and associated disorders are caused by expansion of the cytosine-guanine-guanine (CGG) trinucleotide repeat in the 5&#8217; ...