Name: a fast silver staining protocol enabling simple and efficient detection of ssr markers using a non-denaturing polyacrylamide gel
Uploaded: 2018-04-20T13:30:00
Description: Watch this Scientific Journal Video about A Fast Silver Staining Protocol Enabling Simple and Efficient Detection of SSR Markers using a Non-denaturing Polyacrylamide Gel at JoVE.com

This work was funded by the Guangdong Natural Science Foundation of China (2015A030313500), the Provincial Key International Cooperative Research Platform and the Major Scientific Research Project of Guangdong Higher Education (2015KGJHZ015), the Science and Technology Plan of Guangdong Tobacco Monopoly Administration (201403, 201705), the Science and Technology Plan of Guangdong of China (2016B020201001), the National Innovation Training Project for Undergraduate Students (201711078001). Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. USDA is an equal opportunity provider and employer.

1. Preparation of PCR Products of SSR Markers
<ol>
	<li>Prepare all chemicals and reagents for PCR reactions including template DNA (30 ng/&#181;L), 2&#215; PCR master mix (containing 2&#215; PCR buffer, 0.4 mM of each dNTP, 3 mM of MgCl2, 0.1 U/&#181;L of Taq DNA polymerase and dyes), 10 &#181;M of each forward and reverse primers, and distilled or deionized water (dH2O). 
	NOTE: The SSR markers used in the present study were PT51333 (forward primer sequence: 5 &#39;-GCACCTTTGGTTATCCGACA-3 &...

<ol>
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Biochem. 196, 80-83 (1991).</li><li>Liang, Q., 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=A+rapid+and+effective+method+for+silver+staining+of+PCR+products+separated+in+polyacrylamide+gels.">A rapid and effective method for silver staining of PCR products separated in polyacrylamide gels.</a> Electrophoresis. 35, 2520-2523 (2014).</li><li>Switzer, R. C., Merril, C. R., Shifrin, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+highly+sensitive+silver+stain+for+detecting+proteins+and+peptides+in+polyacrylamide+gels.">A highly sensitive silver stain for detecting proteins and peptides in polyacrylamide gels.</a> Anal. Biochem. 98, 231-237 (1979).</li><li>Sanguinetti, C., Dias, N., Simpson, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+silver+staining+and+recovery+of+PCR+products+separated+on+polyacrylamide+gels.">Rapid silver staining and recovery of PCR products separated on polyacrylamide gels.</a> Biotechniques. 17, 915-919 (1994).</li><li>Ji, Y., Qu, C., Cao, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+optimal+method+of+DNA+silver+staining+in+polyacrylamide+gels.">An optimal method of DNA silver staining in polyacrylamide gels.</a> Electrophoresis. 28, 1173-1175 (2007).</li><li>Qu, L., Li, X., Wu, G., Yang, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+and+sensitive+method+of+DNA+silver+staining+in+polyacrylamide+gels.">Efficient and sensitive method of DNA silver staining in polyacrylamide gels.</a> Electrophoresis. 26, 99-101 (2005).</li><li>An, Z., 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=A+silver+staining+procedure+for+nucleic+acids+in+polyacrylamide+gels+without+fixation+and+pretreatment.">A silver staining procedure for nucleic acids in polyacrylamide gels without fixation and pretreatment.</a> Anal. Biochem. 391, 77-79 (2009).</li><li>Byun, S. O., Fang, Q., Zhou, H., Hickford, J. G. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+effective+method+for+silver-staining+DNA+in+large+numbers+of+polyacrylamide+gels.">An effective method for silver-staining DNA in large numbers of polyacrylamide gels.</a> Anal. Biochem. 385, 174-175 (2009).</li><li>Kumar, M., Kim, S. R., Sharma, P. C., Pareek, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simple+and+efficient+way+to+detect+small+polymorphic+bands+in+plants.">Simple and efficient way to detect small polymorphic bands in plants.</a> Genome Data. 5, 218-222 (2015).</li><li>Liu, 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=Development+of+a+simple+and+effective+silver+staining+protocol+for+detection+of+DNA+fragments.">Development of a simple and effective silver staining protocol for detection of DNA fragments.</a> Electrophoresis. 38, 1175-1178 (2017).</li><li>Wang, D., Shi, J., Carlson, S. R., Cregan, P. B., Ward, R. W., Diers, B. 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The washing of gel after impregnation is a critical step. Insufficient washing time and water volume may cause the incomplete removal of impregnation solution on the surface of the plate and the gel, and result in a dark background. The appropriate developing time is another key step, over-development can result in a dark-brown background with low contrast image of DNA fragments. In addition, the impregnation step significantly affects staining efficiency of DNA fragments. Although extending the impregnation time over 5 ...

The development of PCR-based markers has revolutionized the science of plant genetics and breeding1. Simple sequence repeat (SSR) markers are among the most commonly used and most versatile DNA markers. Their broad genome coverage, abundance, genome specificity, and repeatability are some of the merits of SSR markers in addition to their codominant inheritance for the detection of heterozygous genotypes2. Several studies have used SSR markers to investigate genetic diversity, track ancestry, construct genetic linkage maps, and map genes for economically important traits3,4.
PCR products of SSR markers are commonly separated using agarose or polyacrylamide gel electrophoresis and then visualized with silver staining or under UV light after staining with ethidium bromide. Silver staining of DNA fragments in polyacrylamide gels is more sensitive than the other staining methods5,6 and has been widely used to detect DNA fragments such as SSR markers7.
Like many biological laboratory techniques, silver staining of polyacrylamide gels has steadily improved since its first being reported as a fragment visualization technique in 19798. The technique was initially modified for detection of DNA fragments by Bassam et al.6 in 1991 and then improved by Sanguinetti and coworkers9 in 1994. The method has been further optimized in the last few decades6,7,9,10,11,12,13,14,15. However, most of these updated versions of the protocols still have some drawbacks such as high technical demand and long processing time for fixation and mounting6, that limit the application of these protocols7,11. An optimal protocol that combines low-cost with high efficiency of DNA fragment detection is urgently needed for routine application of silver staining in biological research.
In addition, polyacrylamide gel can be divided into denaturing and non-denaturing polyacrylamide gels, and both can be used for the detection of SSR markers using the silver staining method. The effect and resolution of which do not significantly differ, but non-denaturing polyacrylamide gels are easier to process and take less time16.
On the basis of the previous research15, the aim of the current study is to describe an optimized silver staining protocol in detail for quick, easy and low-cost detection of SSR markers in a non-denaturing polyacrylamide gel.

<table>
	<tbody>
		<tr>
			<td>PCR master mix (Green Taq Mix)</td>
			<td>Vazyme Biotech Co. Ltd, China</td>
			<td>#P131-03</td>
			<td></td>
		</tr>
		<tr>
			<td>50-2000 bp DNA Ladder</td>
			<td>Bio-Rad, USA</td>
			<td>#170-8200</td>
			<td></td>
		</tr>
		<tr>
			<td>DL500 DNA marker</td>
			<td>Takara Bio Inc., Japan</td>
			<td>#3590A</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris base</td>
			<td>Sangon Biotech Shanghai, China</td>
			<td>#77-86-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Boric acid</td>
			<td>Sangon Biotech Shanghai, China</td>
			<td>#10043-35-3</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA-Na2</td>
			<td>Guangzhou Chemical Reagent Factory, China</td>
			<td>#6381-92-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Acrylamide</td>
			<td>Sangon Biotech Shanghai, China</td>
			<td>#79-06-1</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N&#39;-methylene-bis-acrylamide</td>
			<td>Sangon Biotech Shanghai, China</td>
			<td>#110-26-9</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N,N&#39;,N&#39;-Tetramethylethylenediamine</td>
			<td>Sangon Biotech Shanghai, China</td>
			<td>#110-18-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium persulfate</td>
			<td>Guangzhou Chemical Reagent Factory, China</td>
			<td>#7727-54-0</td>
			<td></td>
		</tr>
		<tr>
			<td>Bind-silane</td>
			<td>Solarbio Beijing, China</td>
			<td>#B8150</td>
			<td></td>
		</tr>
		<tr>
			<td>AgNO3</td>
			<td>Sinopharm Chemical Reagent Beijing Co.,Ltd, China</td>
			<td>#7761-88-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde</td>
			<td>Tianjin DaMao Chemical Reagent Factory, China</td>
			<td>#50-00-0</td>
			<td></td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>Guangzhou Chemical Reagent Factory, China</td>
			<td>#1310-73-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>Guangzhou Chemical Reagent Factory, China</td>
			<td>#64-19-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Na2CO3</td>
			<td>Tianjin DaMao Chemical Reagent Factory, China</td>
			<td>#497-19-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Guangzhou Chemical Reagent Factory, China</td>
			<td>#64-17-5</td>
			<td></td>
		</tr>
		<tr>
			<td>HNO3</td>
			<td>Guangzhou Chemical Reagent Factory, China</td>
			<td>#7697-37-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Na2S2O3.5H2O</td>
			<td>Sinopharm Chemical Reagent Beijing Co.,Ltd, China</td>
			<td>#10102-17-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Eriochrome black T(EBT)</td>
			<td>Tianjin DaMao Chemical Reagent Factory, China</td>
			<td>#1787-61-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic tray</td>
			<td>Shanghai Yi Chen Plastic Co., Ltd, China</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>TS-1 Shaker</td>
			<td>Qilinbeter JiangSu, China</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>BenQ M800 Scanner</td>
			<td>BenQ, China</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>DYY-6C Power supply</td>
			<td>Beijing Liuyi Instrument Factory, China</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>High throughout vertical gel systems, JY-SCZF</td>
			<td>Beijing Tunyi Electrophoresis Co., Ltd, China</td>
			<td>-</td>
			<td></td>
		</tr>
	</tbody>
</table>

a fast silver staining protocol enabling simple and efficient detection of ssr markers using a non-denaturing polyacrylamide gel

Simple Sequence Repeat (SSR) is one of the most effective markers used in plant and animal genetic research and molecular breeding programs. Silver staining is a widely used method for the detection of SSR markers in a polyacrylamide gel. However, conventional protocols for silver staining are technically demanding and time-consuming. Like many other biological laboratory techniques, silver staining protocols have been steadily optimized to improve detection efficiency. Here, we report a simplified silver staining method that significantly reduces reagent costs and enhances the detection resolution and picture clarity. The new method requires two major steps (impregnation and development) and three reagents (silver nitrate, sodium hydroxide, and formaldehyde), and only 7 min of processing for a non-denaturing polyacrylamide gel. Compared to previously reported protocols, this new method is easier, quicker and uses fewer chemical reagents for SSR detection. Therefore, this simple, low-cost, and effective silver staining protocol will benefit genetic mapping and marker-assisted breeding by a quick generation of SSR marker data.

The PCR amplicons were produced using the corresponding SSR primer pairs in flowering Chinese cabbage and tobacco. After electrophoresis, the polyacrylamide gels were stained using the above silver staining protocol, which unambiguously detected the banding patterns of SSR markers (Figure 1).
To compare the detection efficiency of different silver staining protocols, PCR products of SSR markers in t...

Watch this Scientific Journal Video about A Fast Silver Staining Protocol Enabling Simple and Efficient Detection of SSR Markers using a Non-denaturing Polyacrylamide Gel at JoVE.com

A Fast Silver Staining Protocol Enabling Simple and Efficient Detection of SSR Markers using a Non-denaturing Polyacrylamide Gel

Here, we report a simple and low-cost silver staining protocol which requires only three reagents and 7 min of processing, and is suitable for fast generation of high-quality SSR data in the genetic analysis.

Simple Sequence Repeat (SSR) is one of the most effective markers used in plant and animal genetic research and molecular breeding programs. Silver ...

The overall goal of this protocol is to introduce an optimized silver staining method for quick, easy, and low cost detection of SSR markers in non-denaturing polyacrylamide gels. The rapid genotyping of SSR markers can help answer key questions in the genetic research and application field such as genetic diversity analysis and marker assisted selection in molecular breeding programs. The main advantages of this technique is that it's easy to carry out, takes less time and using fewer chemical reagents than other protocols for the detection of SSR markers.This method avoids the fixing, stopping, and several washing steps found in conventional protocols. And only requires the two main steps of impregnation and development. Clear images can be produced using this protocol as no background noise for the unambiguous detection of SSR banding patterns.One can screen approximately 800 DNA samples per day using this technique and it has been used successfully in tobacco and flowering Chinese cabbage research. After preparing PCR products and gel solutions according to the text protocol, use detergent in tap water to wash one set of glass plates and spacers followed by a complete rinsing with distilled water. Set the plates in a plate drying rack to air dry.Disperse one milliliter of Bind-silane solution onto the inner surface of a rectangular glass plate and dry it for five minutes. Then disperse one milliliter of Repel-silane onto the inner surface of a notched glass plate with a swab, and use a tissue paper to wipe off excess solution before allowing the plate to air dry for five minutes. Assemble the glass plates with spacers with the notched plate on top.And use casting clamps to clamp both sides of the assembly. Next, pour an appropriate amount of 6%non-denaturing polyacrylamide gel solution into a beaker for the plate set. Add 20 microliters of TEMED and 200 microliters of fresh 20%APS and gently mix.Immediately and carefully pour the solution into the assembled glass plates along the edge of the notched plate, filling the space almost to the top. And insert the comb. Then add a small volume of gel solution over the comb and allow the gel to set at room temperature for 30 minutes.When the gel is fully polymerized, remove the casting clamps and position the plate set in the electrophoresis tank unit with the notched plate facing toward the upper buffer reservoir. Use large clamps to attach the plate set to the tank unit. Pour one liter of 0.5 X TBE buffer into each of the upper and the lower chambers.Then remove the comb and use a pipette or syringe filled with buffer to thoroughly flush all the wells. To run the polyacrylamide gel, load about one microliter of PCR product into each well. Also, load a DNA ladder on either end.Then fix the safety cover to the upper buffer chamber. Connect the leads to the power supply, matching the color coded red to red, and black to black. Run the gel at a constant voltage of 110 volts until the dye reaches a defined position.Normally, for a approximately 70 minutes. Following electrophoresis, open the valve and drain the buffer from the upper chamber into a large beaker. Detach the side clamps and remove the plate from the apparatus.Then use a spatula to carefully separate the notched glass plate along one side and make sure that the gel remains attached to the other glass plate coated with Bind-silane. Next, prepare one liter of fresh impregnation solution by dissolving 1.5 grams of silver nitrate in one liter of distilled water. Then prepare one liter of fresh development solution by dissolving 10 grams of sodium hydroxide in 900 milliliters of distilled water.Add one milliliter of 37%formaldehyde and use distilled water to adjust to a final volume of one liter. With ample distilled water, carefully rinse the gel and glass plate to remove the electrophoresis buffer. Then place the plate with the gel facing up into a plastic tray and submerge the gel in one liter of impregnation solution.Gently shake the tray on a shaker at 60 RPM for three to four minutes. Transfer the plate out of the impregnation solution into another tray. Then use ample distilled water to rinse the residual impregnation solution off of the surface of the plate and the gel two times for three to five seconds each.The gel wash step after impregnation is critical. Insufficient washing my cause incomplete removal of impregnation solution. And result in dark background.Place the place with the gel facing up into another tray. Submerge the plate in one liter of development solution then gently shake the tray at 50 RPM for approximately three minutes. Monitor the appearance of DNA fragments and stop development when the highest ratio of the signal of DNA fragments to the noise of background is observed.The appropriate developing time is another key step. Overdevelopment can result in a dark brown background with a low contrast image of DNA fragments. Rinse the plate and the gel with ample distilled water twice and use tissue paper to dry the gel plate.Then use a scanner and the appropriate software to scan the gel at 300 DPI and adjust the brightness and contrast to get a clear visualization of the DNA bands. Finally, score the banding pattern of the SSR markers based on the DNA fragment sizes in the image. The PCR amplicons presented here were produced using the corresponding SSR primer pairs in flowering Chinese cabbage and tobacco.After electrophoresis, the polyacrylamide gels were stained using the silver staining protocol demonstrated in this video. Which unambiguously detected the banding patterns of SSR markers. To compare the detection efficiency of different silver staining protocols, PCR products of SSR markers were separated using PAGE, and visualized using five published silver staining protocols and a sixth method demonstrated in this video.The protocol demonstrated here had the lowest background noise and highest contrast of DNA fragments such that it produced the highest picture clarity. Of the six protocols tested, the method demonstrated here takes the least amount of time and requires the fewest number of chemical reagents and process steps. Finally, this figure shows the sensitivity of the protocol as measured using a serial dilution of a 50 to 2000 bp DNA marker on a non-denaturing polyacrylamide gel from 10 nanograms per band in lane one to 9.8 picograms per band of DNA in lane 11.Once mastered, this technique can be done in seven minutes if it is performed properly. While attempting this procedure, it's important to remember to prevent cross-contamination of impregnation and development solutions. After it's development, this technique paved the way for researchers to quickly genotype SSR markers.After watching this video, you should have a good understanding of how to simply and efficient detect SSR markers in a non-denaturing polyacrylamide gel using silver staining. Don't forget that working with chemical reagents can be extremely hazardous and precautions such as gloves, should always be worn while performing this procedure.

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Genetics

Detection of Copy Number Alterations Using Single Cell Sequencing

Detection of genomic changes at single cell resolution is important for characterizing genetic heterogeneity and evolution in normal tissues, cancers, and microbial populations. Traditional methods for assessing genetic heterogeneity have been limited by low resolution, low sensitivity, and/or low specificity. Single cell sequencing has emerged as a powerful tool for detecting genetic heterogeneity with high resolution, high sensitivity and, when appropriately analyzed, high specificity. Here we provide a protocol for the isolation, whole genome amplification, sequencing, and analysis of single cells. Our approach allows for the reliable identification of megabase-scale copy number variants in single cells. However, aspects of this protocol can also be applied to investigate other types of genetic alterations in single cells.

Single cell sequencing is an increasingly popular and accessible tool for addressing genomic changes at high resolution. We provide a protocol that uses single cell sequencing to identify copy number alterations in single cells.

Detection of genomic changes at single cell resolution is important for characterizing genetic heterogeneity and evolution in normal tissues, cancers, and ...

Mapping RNA-RNA Interactions Globally Using Biotinylated Psoralen

Knowing how RNAs interact with themselves and with others is key to understanding RNA based gene regulation in the cell. While examples of RNA-RNA interactions such as microRNA-mRNA interactions have been shown to regulate gene expression, the full extent to which RNA interactions occur in the cell is still unknown. Previous methods to study RNA interactions have primarily focused on subsets of RNAs that are interacting with a particular protein or RNA species. Here, we detail a method named Sequencing of Psoralen crosslinked, Ligated, and Selected Hybrids (SPLASH) that allows genome-wide capture of RNA interactions in vivo in an unbiased manner. SPLASH utilizes in vivo crosslinking, proximity ligation, and high throughput sequencing to identify intramolecular and intermolecular RNA base-pairing partners globally. SPLASH can be applied to different organisms including bacteria, yeast and human cells, as well as diverse cellular conditions to facilitate the understanding of the dynamics of RNA organization under diverse cellular contexts. The entire experimental SPLASH protocol takes about 5 days to complete and the computational workflow takes about 7 days to complete.

Here, we detail the method of Sequencing of Psoralen crosslinked, Ligated, and Selected Hybrids (SPLASH), which enables genome-wide mapping of intramolecular and intermolecular RNA-RNA interactions in vivo. SPLASH can be applied to study RNA interactomes of organisms including yeast, bacteria and humans.

Knowing how RNAs interact with themselves and with others is key to understanding RNA based gene regulation in the cell. While examples of RNA-RNA ...

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 ...

Laser Microirradiation to Study In Vivo Cellular Responses to Simple and Complex DNA Damage

DNA damage induces specific signaling and repair responses in the cell, which is critical for protection of genome integrity. Laser microirradiation became a valuable experimental tool to investigate the DNA damage response (DDR) in vivo. It allows real-time high-resolution single-cell analysis of macromolecular dynamics in response to laser-induced damage confined to a submicrometer region in the cell nucleus. However, various laser conditions have been used without appreciation of differences in the types of damage induced. As a result, the nature of the damage is often not well characterized or controlled, causing apparent inconsistencies in the recruitment or modification profiles. We demonstrated that different irradiation conditions (i.e., different wavelengths as well as different input powers (irradiances) of a femtosecond (fs) near-infrared (NIR) laser) induced distinct DDR and repair protein assemblies. This reflects the type of DNA damage produced. This protocol describes how titration of laser input power allows induction of different amounts and complexities of DNA damage, which can easily be monitored by detection of base and crosslinking damages, differential poly (ADP-ribose) (PAR) signaling, and pathway-specific repair factor assemblies at damage sites. Once the damage conditions are determined, it is possible to investigate the effects of different damage complexity and differential damage signaling as well as depletion of upstream factor(s) on any factor of interest.

Laser Microirradiation to Study In Vivo Cellular Responses to Simple and Complex DNA Damage

The goal of this protocol is to describe how to use laser microirradiation to induce different types of DNA damage, including relatively simple strand breaks and complex damage, to study DNA damage signaling and repair factor assembly at damage sites in vivo.

DNA damage induces specific signaling and repair responses in the cell, which is critical for protection of genome integrity. Laser microirradiation ...

An Array-based Comparative Genomic Hybridization Platform for Efficient Detection of Copy Number Variations in Fast Neutron-induced Medicago truncatula Mutants

Mutants are invaluable genetic resources for gene function studies. To generate mutant collections, three types of mutagens can be utilized, including biological such as T-DNA or transposon, chemical such as ethyl methanesulfonate (EMS), or physical such as ionization radiation. The type of mutation observed varies depending on the mutagen used. For ionization radiation induced mutants, mutations include deletion, duplication, or rearrangement. While T-DNA or transposon-based mutagenesis is limited to species that are susceptible to transformation, chemical or physical mutagenesis can be applied to a broad range of species. However, the characterization of mutations derived from chemical or physical mutagenesis traditionally relies on a map-based cloning approach, which is labor intensive and time consuming. Here, we show that a high-density genome array-based comparative genomic hybridization (aCGH) platform can be applied to efficiently detect and characterize copy number variations (CNVs) in mutants derived from fast neutron bombardment (FNB) mutagenesis in Medicago truncatula, a legume species. Whole genome sequence analysis shows that there are more than 50,000 genes or gene models in M. truncatula. At present, FNB-induced mutants in M. truncatula are derived from more than 150,000 M1 lines, representing invaluable genetic resources for functional studies of genes in the genome. The aCGH platform described here is an efficient tool for characterizing FNB-induced mutants in M. truncatula.

An Array-based Comparative Genomic Hybridization Platform for Efficient Detection of Copy Number Variations in Fast Neutron-induced Medicago truncatula Mutants

This protocol provides experimental steps and information about reagents, equipment, and analysis tools for researchers who are interested in carrying out whole genome array-based comparative genomic hybridization (CGH) analysis of copy number variations in plants.

Mutants are invaluable genetic resources for gene function studies. To generate mutant collections, three types of mutagens can be utilized, including ...

Efficient Production and Identification of CRISPR/Cas9-generated Gene Knockouts in the Model System Danio rerio

Characterization of the clustered, regularly interspaced, short, palindromic repeat (CRISPR) system of Streptococcus pyogenes has enabled the development of a customizable platform to rapidly generate gene modifications in a wide variety of organisms, including zebrafish. CRISPR-based genome editing uses a single guide RNA (sgRNA) to target a CRISPR-associated (Cas) endonuclease to a genomic DNA (gDNA) target of interest, where the Cas endonuclease generates a double-strand break (DSB). Repair of DSBs by error-prone mechanisms lead to insertions and/or deletions (indels). This can cause frameshift mutations that often introduce a premature stop codon within the coding sequence, thus creating a protein-null allele. CRISPR-based genome engineering requires only a few molecular components and is easily introduced into zebrafish embryos by microinjection. This protocol describes the methods used to generate CRISPR reagents for zebrafish microinjection and to identify fish exhibiting germline transmission of CRISPR-modified genes. These methods include in vitro transcription of sgRNAs, microinjection of CRISPR reagents, identification of indels induced at the target site using a PCR-based method called a heteroduplex mobility assay (HMA), and characterization of the indels using both a low throughput and a powerful next-generation sequencing (NGS)-based approach that can analyze multiple PCR products collected from heterozygous fish. This protocol is streamlined to minimize both the number of fish required and the types of equipment needed to perform the analyses. Furthermore, this protocol is designed to be amenable for use by laboratory personal of all levels of experience including undergraduates, enabling this powerful tool to be economically employed by any research group interested in performing CRISPR-based genomic modification in zebrafish.

Efficient Production and Identification of CRISPR/Cas9-generated Gene Knockouts in the Model System Danio rerio

Targeted genome editing in the model system Danio rerio (zebrafish) has been greatly facilitated by the emergence of CRISPR-based approaches. Herein, we describe a streamlined, robust protocol for generation and identification of CRISPR-derived nonsense alleles that incorporates the heteroduplex mobility assay and identification of mutations using next-generation sequencing.

Characterization of the clustered, regularly interspaced, short, palindromic repeat (CRISPR) system of Streptococcus pyogenes has enabled the development ...

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. ...

A Simple, Rapid, and Quantitative Assay to Measure Repair of DNA-protein Crosslinks on Plasmids Transfected into Mammalian Cells

The purpose of this method is to provide a flexible, rapid, and quantitative technique to examine the kinetics of DNA-protein crosslink (DPC) repair in mammalian cell lines. Rather than globally assaying removal of xenobiotic-induced or spontaneous chromosomal DPC removal, this assay examines the repair of a homogeneous, chemically defined lesion specifically introduced at one site within a plasmid DNA substrate. Importantly, this approach avoids the use of radioactive materials and is not dependent on expensive or highly-specialized technology. Instead, it relies on standard recombinant DNA procedures and widely available real-time, quantitative polymerase chain reaction (qPCR) instrumentation. Given the inherent flexibility of the strategy utilized, the size of the crosslinked protein, as well as the nature of the chemical linkage and the precise DNA sequence context of the attachment site can be varied to address the respective contributions of these parameters to the overall efficiency of DPC repair. Using this method, plasmids containing a site-specific DPC were transfected into cells and low molecular weight DNA recovered at various times post-transfection. Recovered DNA is then subjected to strand-specific primer extension (SSPE) using a primer complementary to the damaged strand of the plasmid. Since the DPC lesion blocks Taq DNA polymerase, the ratio of repaired to un-repaired DNA can be quantitatively assessed using qPCR. Cycle threshold (CT) values are used to calculate percent repair at various time points in the respective cell lines. This SSPE-qPCR method can also be used to quantitatively assess the repair kinetics of any DNA adduct that blocks Taq polymerase.

The goal of this protocol is to quantify the repair of defined DNA-protein crosslinks on plasmid DNA. Lesioned plasmids are transfected into recipient mammalian cell lines and low-molecular weight harvested at multiple time points post-transfection. DNA repair kinetics are quantified using strand-specific primer extension followed by qPCR.

The purpose of this method is to provide a flexible, rapid, and quantitative technique to examine the kinetics of DNA-protein crosslink (DPC) repair in ...

Lentiviral Mediated Production of Transgenic Mice: A Simple and Highly Efficient Method for Direct Study of Founders

For almost 40 years, pronuclear DNA injection represents the standard method to generate transgenic mice with random integration of transgenes. Such a routine procedure is widely utilized throughout the world and its main limitation resides in the poor efficacy of transgene integration, resulting in a low yield of founder animals. Only few percent of animals born after implantation of injected fertilized oocytes have integrated the transgene. In contrast, lentiviral vectors are powerful tools for integrative gene transfer and their use to transduce fertilized oocytes allows highly efficient production of founder transgenic mice with an average yield above 70%. Furthermore, any mouse strain can be used to produce transgenic animal and the penetrance of transgene expression is extremely high, above 80% with lentiviral mediated transgenesis compared to DNA microinjection. The size of the DNA fragment that can be cargo by the lentiviral vector is restricted to 10 kb and represents the major limitation of this method. Using a simple and easy to perform injection procedure beneath the zona pellucida of fertilized oocytes, more than 50 founder animals can be produced in a single session of microinjection. Such a method is highly adapted to perform, directly in founder animals, rapid gain and loss of function studies or to screen genomic DNA regions for their ability to control and regulate gene expression in vivo.

Here, we present a protocol to promote transgene integration and production of founder transgenic mice with high efficacy by a simple injection of a lentiviral vector in the perivitelline space of a fertilized oocyte.

For almost 40 years, pronuclear DNA injection represents the standard method to generate transgenic mice with random integration of transgenes. Such a ...

A Fast and Quantitative Method for Post-translational Modification and Variant Enabled Mapping of Peptides to Genomes

Cross-talk between genes, transcripts, and proteins is the key to cellular responses; hence, analysis of molecular levels as distinct entities is slowly being extended to integrative studies to enhance the understanding of molecular dynamics within cells. Current tools for the visualization and integration of proteomics with other omics datasets are inadequate for large-scale studies. Furthermore, they only capture basic sequence identify, discarding post-translational modifications and quantitation. To address these issues, we developed PoGo to map peptides with associated post-translational modifications and quantification to reference genome annotation. In addition, the tool was developed to enable the mapping of peptides identified from customized sequence databases incorporating single amino acid variants. While PoGo is a command line tool, the graphical interface PoGoGUI enables non-bioinformatics researchers to easily map peptides to 25 species supported by Ensembl genome annotation. The generated output borrows file formats from the genomics field and, therefore, visualization is supported in most genome browsers. For large-scale studies, PoGo is supported by TrackHubGenerator to create web-accessible repositories of data mapped to genomes that also enable an easy sharing of proteogenomics data. With little effort, this tool can map millions of peptides to reference genomes within only a few minutes, outperforming other available sequence-identity based tools. This protocol demonstrates the best approaches for proteogenomics mapping through PoGo with publicly available datasets of quantitative and phosphoproteomics, as well as large-scale studies.

Here we present the proteogenomic tool PoGo and protocols for fast, quantitative, post-translational modification and variant enabled mapping of peptides identified through mass spectrometry onto reference genomes. This tool is of use to integrate and visualize proteogenomic and personal proteomic studies interfacing with orthogonal genomics data.

Cross-talk between genes, transcripts, and proteins is the key to cellular responses; hence, analysis of molecular levels as distinct entities is slowly ...