Name: linear amplification mediated pcr &#8211; localization of genetic elements and characterization of unknown flanking dna
Uploaded: 2014-06-25T14:00:00
Description: Watch this Scientific Journal Video about Linear Amplification Mediated PCR â€“ Localization of Genetic Elements and Characterization of Unknown Flanking DNA at JoVE.com

Funding was provided by the Deutsche Forschungsgemeinschaft (SPP1230, grant of the Tumor Center Heidelberg/Mannheim), by the Bundesministerium f&#252;r Bildung und Forschung (iGene), by the VIth + VIIth Framework Programs of the European Commission (CONSERT, CLINIGENE and PERSIST). We thank Ina Kutschera for demonstrating the protocol technique in the video.

1. Preparation of Linker Cassettes (LC)
<ol>
	<li>Mix 40 &#181;l of LC1 oligonucleotide (Table 1), 40 &#181;l of LC2 oligonucleotide (Table 1, with proper restriction enzyme overhang), 110 &#181;l Tris-HCl&#160;(100 mM, pH 7.5), and 10 &#181;l 250 mM MgCl2.</li>
	<li>Incubate at 95 &#176;C for 5min and let the reaction cool down slowly to room temperature. Add 300 &#181;l H2O and concentrate dsLinker-DNA on a centrifugation filter. Add 80 &#181;l H2O to...

<ol>
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The LAM-PCR technique allows identifying unknown DNA sequences that flank a known DNA region. Because of the high sensitivity resulting from preamplification of the junctions with specific primers hybridizing in the known DNA sequence, it is possible to amplify and detect even rare junctions down to the single cell level. Contrary, in a polyclonal situation LAM-PCR is able to amplify thousands of different junctions in one single reaction.
However, due to the use of restriction enzymes only a ...

Linear-amplification mediated PCR (LAM-PCR) allows identifying and characterizing unknown flanking DNA adjacent to known DNA of any origin. More specifically, LAM-PCR has been developed to localize viral vector integration sites (IS) within the host genome1,2. Genetic elements like retroviruses or transposons integrate their genome into the host genome in a (semi-) random manner3-6. In many cases it is decisive to know exactly the position where these vectors integrated. LAM-PCR has been proven to be superior to alternative techniques like ligation-mediated PCR7 and its variants or inverse PCR8. The sensitivity and robustness of this method arises from the initial preamplification of the vector-genome junctions and magnetic selection of amplified PCR products. Like the alternative methods mentioned, LAM-PCR relies on the use of restriction enzymes, introducing a bias into retrieval capacity of IS9-11. Thus, only a subset of the IS repertoire (the integrome) can be detected in one reaction. This bias is minimized by the parallel analysis of a given sample using optimal combinations of restriction enzymes9. Recently, a variant of the technology termed non-restrictive LAM-PCR (nrLAM-PCR) has been developed that circumvents the use of restriction enzymes and allows unbiased genome-wide analysis of a sample in a single reaction9,12.
In the past, LAM-PCR has been used to identify the causative retroviral IS giving rise to leukemia in a few patients in clinical gene therapy trials13-15. Since then, LAM-PCR has been adapted to identify IS from other integrating vectors (lentiviral vectors, transposons) and also to identify integration patterns of passively integrating vectors like adeno-associated vectors (AAV) or integrase-defective lentiviral vectors (IDLV)16-21. Applications of LAM-PCR are wide spread: traditionally, the technique is widely used to study the clonal composition of gene modified cells in patients that have undergone gene therapy or to assess the biosafety of novel vector systems by unraveling their integration behavior15,16,22-24. Recently, LAM-PCR enabled determining specificity and off-target activity of designer nucleases by an IDLV trapping assay25.
Moreover, LAM-PCR allows to easily follow the fate of a transduced cell over time in an organism. This allows to identify proto-oncogenes as well as tumor suppressor genes and also to study hematopoiesis or cancer stem cell biology26-28. Last but not least, LAM-PCR was adapted to study T-cell receptor diversity in humans29 (and unpublished data).
The intrinsic power of the technology is reinforced by linking the method to deep sequencing technologies that allow characterizing millions of unknown flanking DNA with single nucleotide resolution in whole genomes. In the following protocol, we describe step-by step the amplification and identification of flanking unknown DNA exemplarily to identify lentiviral vector IS. Oligonucleotides used in the protocol are listed in Table 1. Extracted DNA or cDNA of any source can be used as DNA template for LAM-PCR and nrLAM-PCR.

<table border="0" cellpadding="0" cellspacing="0" width="1209">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Name of Material/ Equipment</td>
			<td style="width:203px;">Company</td>
			<td style="width:120px;">Catalog Number</td>
			<td style="width:527px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Taq DNA Polymerase</td>
			<td style="width:203px;">Genaxxon Bioscience GmbH</td>
			<td style="width:120px;">M3001.5000</td>
			<td>Alternative Taq Polymerases may be used</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">PCR Buffer</td>
			<td style="width:203px;">Qiagen</td>
			<td style="width:120px;">201203</td>
			<td>Use of this buffer is recommended</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">dNTP-Mixture</td>
			<td style="width:203px;">Genaxxon Bioscience GmbH</td>
			<td style="width:120px;">M3015.4020</td>
			<td>or any other dNTPs</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Oligonucleotides (Primers)</td>
			<td style="width:203px;">MWG Biotech</td>
			<td style="width:120px;"></td>
			<td>HPLC purified</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Dynabeads M-280 Streptavidin&#160;</td>
			<td style="width:203px;">Invitrogen</td>
			<td style="width:120px;">11206D</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">PBS</td>
			<td style="width:203px;">Gibco</td>
			<td style="width:120px;">14190-086</td>
			<td>0.1 % wt/vol BSA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">6M LiCl</td>
			<td style="width:203px;">Roth</td>
			<td style="width:120px;">3739.1</td>
			<td>10 mM Tris-HCl&#160; (pH 7.5)/1 mM EDTA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Tris-HCl, pH 7.5</td>
			<td style="width:203px;">USB Corporation&#160;</td>
			<td style="width:120px;">22637</td>
			<td>or any other supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">EDTA</td>
			<td style="width:203px;">Applichem</td>
			<td style="width:120px;">A1103,0250</td>
			<td>or any other supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Klenow Polymerase</td>
			<td style="width:203px;">Roche Diagnostics</td>
			<td style="width:120px;">10104523001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Hexanucleotide mixture</td>
			<td style="width:203px;">Roche Diagnostics</td>
			<td style="width:120px;">11277081001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Restriction endonuclease</td>
			<td style="width:203px;">NEB</td>
			<td style="width:120px;"></td>
			<td>or any other supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Fast-Link DNA ligation kit</td>
			<td style="width:203px;">Epicentre Biotechnologies</td>
			<td style="width:120px;">LK11025</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">CircLigase ssDNA Ligase Kit</td>
			<td style="width:203px;">Epicentre Biotechnologies</td>
			<td style="width:120px;">CL4111K</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">NaOH</td>
			<td style="width:203px;">Sigma-Aldrich</td>
			<td style="width:120px;">72068</td>
			<td>or any other supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Agarose LE</td>
			<td style="width:203px;">Roche Diagnostics</td>
			<td style="width:120px;">11685660001</td>
			<td>or any other supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">TBE buffer</td>
			<td style="width:203px;">Amresco</td>
			<td style="width:120px;">0658</td>
			<td>or any other supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Ethidium bromide</td>
			<td style="width:203px;">Applichem</td>
			<td style="width:120px;">A2273,0005</td>
			<td>Ethidium bromide is mutagenic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">100 bp DNA Ladder</td>
			<td style="width:203px;">Invitrogen</td>
			<td style="width:120px;">15628-050</td>
			<td>or any other DNA ladder</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">20 mM NaCl</td>
			<td style="width:203px;">Sigma-Aldrich</td>
			<td style="width:120px;">71393-1L</td>
			<td>or any other supplier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Magna-Sep Magnetic Particle Separator&#160;</td>
			<td style="width:203px;">Life Technologies</td>
			<td style="width:120px;">K158501</td>
			<td>for use with 1.5 ml Tubes</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Magna-Sep Magnetic Particle Separator&#160;</td>
			<td style="width:203px;">Life Technologies</td>
			<td style="width:120px;">K158696</td>
			<td>for use with 96 well plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Amicon Ultra-0.5, Ultracel-30 membrane</td>
			<td style="width:203px;">Millipore</td>
			<td>UFC503096</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">PerfectBlue Gelsystem Midi S</td>
			<td style="width:203px;">PeqLab</td>
			<td style="width:120px;">40-1515</td>
			<td>or other electrophoresis system&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">TProfessional 96</td>
			<td style="width:203px;">Biometra</td>
			<td style="width:120px;">050-551</td>
			<td>or other Thermocycler for 96-well plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Orbital shaker KS 260 basic</td>
			<td style="width:203px;">IKA</td>
			<td style="width:120px;">2980200</td>
			<td>or other horizontal shaker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">PCR softtubes 0.2 ml</td>
			<td style="width:203px;">Biozym Scientific GmbH</td>
			<td style="width:120px;">711082</td>
			<td>or other 0.2 ml PCR tubes</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">1.5 ml tubes</td>
			<td style="width:203px;">Eppendorf</td>
			<td style="width:120px;">12682</td>
			<td>or other 1.5 ml tubes</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Gel documentation system</td>
			<td style="width:203px;">PeqLab</td>
			<td style="width:120px;"></td>
			<td>or any other gel documentation system</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Nanodrop ND-1000 spectrophotometer</td>
			<td style="width:203px;">Thermo Scientific</td>
			<td style="width:120px;">ND-1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">Spreadex EL1200 precast gel</td>
			<td style="width:203px;">Elchrom Scientific</td>
			<td style="width:120px;">3497</td>
			<td></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:360px;">Submerged gel electrophoresis apparatus SEA 2000&#160;</td>
			<td style="width:203px;">Elchrom Scientific</td>
			<td style="width:120px;">2001E</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:360px;">2100 Electrophoresis Bioanalyzer</td>
			<td style="width:203px;">Agilent Technologies</td>
			<td>G2939AA</td>
			<td></td>
		</tr>
	</tbody>
</table>

linear amplification mediated pcr &#8211; localization of genetic elements and characterization of unknown flanking dna

Linear-amplification mediated PCR (LAM-PCR) has been developed to study hematopoiesis in gene corrected cells of patients treated by gene therapy with integrating vector systems. Due to the stable integration of retroviral vectors, integration sites can be used to study the clonal fate of individual cells and their progeny. LAM- PCR for the first time provided evidence that leukemia in gene therapy treated patients originated from provirus induced overexpression of a neighboring proto-oncogene. The high sensitivity and specificity of LAM-PCR compared to existing methods like inverse PCR and ligation mediated (LM)-PCR is achieved by an initial preamplification step (linear PCR of 100 cycles) using biotinylated vector specific primers which allow subsequent reaction steps to be carried out on solid phase (magnetic beads). LAM-PCR is currently the most sensitive method available to identify&#160;unknown DNA which is located in the proximity of known DNA. Recently, a variant of LAM-PCR has been developed that circumvents restriction digest thus abrogating retrieval bias of integration sites and enables a comprehensive analysis of provirus locations in host genomes. The following protocol explains step-by-step the amplification of both 3&#8217;- and 5&#8217;- sequences adjacent to the integrated lentiviral vector.

LAM-PCR results in amplification of vector genome junctions with a defined fragment size for each junction. The size of individual PCR fragments depends on the distance between the location of the known DNA in the genome and the closest restriction enzyme recognition site. This allows visualizing the diversity of amplified junctions in analyzed samples by gel electrophoresis, e.g., if only single (monoclonal), several (oligoclonal), or multiple (polyclonal) bands are present on the gel. The results of LAM-PCR ar...

Watch this Scientific Journal Video about Linear Amplification Mediated PCR â€“ Localization of Genetic Elements and Characterization of Unknown Flanking DNA at JoVE.com

Linear Amplification Mediated PCR &amp;#8211; Localization of Genetic Elements and Characterization of Unknown Flanking DNA

Linear-amplification mediated (LAM)-PCR is a method developed to identify the exact positions of integrating viral vectors in the genome. The technique has evolved to be the superior method to study clonal dynamics in gene therapy patients, biosafety of novel vector technologies, T-cell diversity, cancer stem cell models, etc.

Linear Amplification Mediated PCR &#8211; Localization of Genetic Elements and Characterization of Unknown Flanking DNA

Linear-amplification mediated PCR (LAM-PCR) has been developed to study hematopoiesis in gene corrected cells of patients treated by gene therapy with ...

linear-amplification-mediated-pcr-localization-genetic-elements

Research

JoVE Journal

Biology

Genetic Studies of Human DNA Repair Proteins Using Yeast as a Model System 

Understanding the roles of human DNA repair proteins in genetic pathways is a formidable challenge to many researchers. Genetic studies in mammalian systems have been limited due to the lack of readily available tools including defined mutant genetic cell lines, regulatory expression systems, and appropriate selectable markers. To circumvent these difficulties, model genetic systems in lower eukaryotes have become an attractive choice for the study of functionally conserved DNA repair proteins and pathways. We have developed a model yeast system to study the poorly defined genetic functions of the Werner syndrome helicase-nuclease (WRN) in nucleic acid metabolism. Cellular phenotypes associated with defined genetic mutant backgrounds can be investigated to clarify the cellular and molecular functions of WRN through its catalytic activities and protein interactions. The human WRN gene and associated variants, cloned into DNA plasmids for expression in yeast, can be placed under the control of a regulatory plasmid element. The expression construct can then be transformed into the appropriate yeast mutant background, and genetic function assayed by a variety of methodologies. Using this approach, we determined that WRN, like its related RecQ family members BLM and Sgs1, operates in a Top3-dependent pathway that is likely to be important for genomic stability. This is described in our recent publication [1] at <a href="http://www.impactaging.com">www.impactaging.com</a>. Detailed methods of specific assays for genetic complementation studies in yeast are provided in this paper.

Genetic Studies of Human DNA Repair Proteins Using Yeast as a Model System

Genetic studies in yeast can be employed to investigate the molecular and cellular functions of human genes in cellular DNA metabolism. Methods are described for the genetic characterization of the human WRN gene product defective in the premature aging disorder Werner syndrome in functionally conserved pathways using yeast as a tractable model system.

Understanding the roles of human DNA repair proteins in genetic pathways is a formidable challenge to many researchers.  Genetic studies in mammalian ...

Adenovirus-mediated Genetic Removal of Signaling Molecules in Cultured Primary Mouse Embryonic Fibroblasts

The ability to genetically remove specific components of various cell signalling cascades has been an integral tool in modern signal transduction analysis. One particular method to achieve this conditional deletion is via the use of the Cre-loxP system. This method involves flanking the gene of interest with loxP sites, which are specific recognition sequences for the Cre recombinase protein. Exposure of the so-called floxed (flanked by loxP site) DNA to this enzyme results in a Cre-mediated recombination event at the loxP sites, and subsequent excision of the intervening gene3. Several different methods exist to administer Cre recombinase to the site of interest. In this video, we demonstrate the use of an adenovirus containing the Cre recombinase gene to infect primary mouse embryonic fibroblasts (MEFs) obtained from embryos containing a floxed Rac1 allele1. Our rationale for selecting Rac1 MEFs for our experiments is that clear morphological changes can be seen upon deletion of Rac1, due to alterations in the actin cytoskeleton2,5. 72 hours following viral transduction and Cre expression, cells were stained using the actin dye phalloidin and imaged using confocal laser scanning microscopy. It was observed that MEFs which had been exposed to the adeno-Cre virus appeared contracted and elongated in morphology compared to uninfected cells, consistent with previous reports2,5. The adenovirus method of Cre recombinase delivery is advantageous as the adeno-Cre virus is easily available, and gene deletion via Cre in nearly 100% of the cells can be achieved with optimized adenoviral infection.

In this video we use an adenovirus carrying the Cre recombinase gene to infect primary mouse embryonic fibroblasts carrying a floxed Rac1 allele.

The ability to genetically remove specific components of various cell signalling cascades has been an integral tool in modern signal transduction ...

DNA Extraction from Paraffin Embedded Material for Genetic and Epigenetic Analyses

Disease development and progression are characterized by frequent genetic and epigenetic aberrations including chromosomal rearrangements, copy number gains and losses and DNA methylation. Advances in high-throughput, genome-wide profiling technologies, such as microarrays, have significantly improved our ability to identify and detect these specific alterations. However as technology continues to improve, a limiting factor remains sample quality and availability. Furthermore, follow-up clinical information and disease outcome are often collected years after the initial specimen collection. Specimens, typically formalin-fixed and paraffin embedded (FFPE), are stored in hospital archives for years to decades. DNA can be efficiently and effectively recovered from paraffin-embedded specimens if the appropriate method of extraction is applied. High quality DNA extracted from properly preserved and stored specimens can support quantitative assays for comparisons of normal and diseased tissues and generation of genetic and epigenetic signatures 1. To extract DNA from paraffin-embedded samples, tissue cores or microdissected tissue are subjected to xylene treatment, which dissolves the paraffin from the tissue, and then rehydrated using a series of ethanol washes. Proteins and harmful enzymes such as nucleases are subsequently digested by proteinase K. The addition of lysis buffer, which contains denaturing agents such as sodium dodecyl sulfate (SDS), facilitates digestion 2. Nucleic acids are purified from the tissue lysate using buffer-saturated phenol and high speed centrifugation which generates a biphasic solution. DNA and RNA remain in the upper aqueous phase, while proteins, lipids and polysaccharides are sequestered in the inter- and organic-phases respectively. Retention of the aqueous phase and repeated phenol extractions generates a clean sample. Following phenol extractions, RNase A is added to eliminate contaminating RNA. Additional phenol extractions following incubation with RNase A are used to remove any remaining enzyme. The addition of sodium acetate and isopropanol precipitates DNA, and high speed centrifugation is used to pellet the DNA and facilitate isopropanol removal. Excess salts carried over from precipitation can interfere with subsequent enzymatic assays, but can be removed from the DNA by washing with 70% ethanol, followed by centrifugation to re-pellet the DNA 3. DNA is re-suspended in distilled water or the buffer of choice, quantified and stored at -20&deg;C. Purified DNA can subsequently be used in downstream applications which include, but are not limited to, PCR, array comparative genomic hybridization 4 (array CGH), methylated DNA Immunoprecipitation (MeDIP) and sequencing, allowing for an integrative analysis of tissue/tumor samples.

This video demonstrates the protocol for DNA extraction from formalin-fixed paraffin-embedded material. This is a multi-day procedure in which tissue sections are deparaffinized with xylene, rehydrated with ethanol and treated with proteinase K to purify and isolate DNA for subsequent gene-specific or genome-wide analysis.

Disease development and progression are characterized by frequent genetic and epigenetic aberrations including chromosomal rearrangements, copy number ...

Determining Genetic Expression Profiles in C. elegans Using Microarray and Real-time PCR

Synapses are composed of a presynaptic active zone in the signaling cell and a postsynaptic terminal in the target cell. In the case of chemical synapses, messages are carried by neurotransmitters released from presynaptic terminals and received by receptors on postsynaptic cells. Our previous research in Caenorhabditis elegans has shown that VSM-1 negatively regulates exocytosis. Additionally, analysis of synapses in vsm-1 mutants showed that animals lacking a fully functional VSM-1 have increased synaptic connectivity. Based on these preliminary findings, we hypothesized that C. elegans VSM-1 may play a crucial role in synaptogenesis. To test this hypothesis, double-labeled microarray analysis was performed, and gene expression profiles were determined. First, total RNA was isolated, reversely transcribed to cDNA, and hybridized to the DNA microarrays. Then, in-silico analysis of fluorescent probe hybridization revealed significant induction of many genes coding for members of the major sperm protein family (MSP) in mutants with enhanced synaptogenesis. MSPs are the major component of sperm in C. elegans and appear to signal nematode oocyte maturation and ovulation . In fruit flies, Chai and colleagues 1 demonstrated that MSP-like molecules regulate presynaptic bouton number and size at the neuromuscular junction. Moreover, analysis performed by Tsuda and coworkers 2 suggested that MSPs may act as ligands for Eph receptors and trigger receptor tyrosine kinase signaling cascades. Lastly, real time PCR analysis corroborated that the gene coding for MSP-32 is induced in vsm-1(ok1468) mutants. Taken together, research performed by our laboratory has shown that vsm-1 mutants have a significant increase in synaptic density, which could be mediated by MSP-32 signaling.

Determining Genetic Expression Profiles in C. elegans Using Microarray and Real-time PCR

Microarray analysis was conducted to determine genetic expression profiles in C. elegans, and real-time PCR was used to validate and quantify microarray data.

Synapses are composed of a presynaptic active zone in the signaling cell and a postsynaptic terminal in the target cell. In the case of chemical synapses, ...

Combining Single-molecule Manipulation and Imaging for the Study of Protein-DNA Interactions

The paper describes the combination of optical tweezers and single molecule fluorescence detection for the study of protein-DNA interaction. The method offers the opportunity of investigating interactions occurring in solution (thus avoiding problems due to closeby surfaces as in other single molecule methods), controlling the DNA extension and tracking interaction dynamics as a function of both mechanical parameters and DNA sequence. The methods for establishing successful optical trapping and nanometer localization of single molecules are illustrated. We illustrate the experimental conditions allowing the study of interaction of lactose repressor (lacI), labeled with Atto532, with a DNA molecule containing specific target sequences (operators) for LacI binding. The method allows the observation of specific interactions at the operators, as well as one-dimensional diffusion of the protein during the process of target search. The method is broadly applicable to the study of protein-DNA interactions but also to molecular motors, where control of the tension applied to the partner track polymer (for example actin or microtubules) is desirable.

Here we describe the instrumentation and methods for detecting single fluorescently-labeled protein molecules interacting with a single DNA molecule suspended between two optically trapped microspheres.

The paper describes the combination of optical tweezers and single molecule fluorescence detection for the study of protein-DNA interaction. The method ...

DNA Electroporation, Isolation and Imaging of Myofibers

Mature muscle has a unique structure that is amenable to live cell imaging. Herein, we describe the experimental protocol for expressing fluorescently labeled proteins in the flexor digitorum brevis (FDB) muscle. Conditions have been optimized to provide a large number of high quality myofibers expressing the electroporated plasmid while minimizing muscle damage. The method employs fluorescent tags on various proteins. Combining this expression method with high resolution confocal microscopy permits live cell imaging, including imaging after laser-induced damage. Fluorescent dyes combined with imaging of fluorescently-tagged proteins provides information regarding the basic structure of muscle and its response to stimuli.

This protocol utilizes electroporation to introduce and express fluorescently labeled proteins in mouse muscle fibers. Following recovery after electroporation, fibers are isolated. Individual fibers are then imaged using high resolution confocal microscopy to visualize muscle structure.

Mature muscle has a unique structure that is amenable to live cell imaging. Herein, we describe the experimental protocol for expressing fluorescently ...

In Vivo Alkaline Comet Assay and Enzyme-modified Alkaline Comet Assay for Measuring DNA Strand Breaks and Oxidative DNA Damage in Rat Liver

Unrepaired DNA damage can lead to genetic instability, which in turn may enhance cancer development. Therefore, identifying potential DNA damaging agents is important for protecting public health. The in vivo alkaline comet assay, which detects DNA damage as strand breaks, is especially relevant for assessing the genotoxic hazards of xenobiotics, as its responses reflect the in vivo absorption, tissue distribution, metabolism and excretion (ADME) of chemicals, as well as DNA repair process. Compared to other in vivo DNA damage assays, the assay is rapid, sensitive, visual and inexpensive, and, by converting oxidative DNA damage into strand breaks using specific repair enzymes, the assay can measure oxidative DNA damage in an efficient and relatively artifact-free manner. Measurement of DNA damage with the comet assay can be performed using both acute and subchronic toxicology study designs, and by integrating the comet assay with other toxicological assessments, the assay addresses animal welfare requirements by making maximum use of animal resources. Another major advantage of the assays is that they only require a small amount of cells, and the cells do not have to be derived from proliferating cell populations. The assays also can be performed with a variety of human samples obtained from clinically or occupationally exposed individuals.

In Vivo Alkaline Comet Assay and Enzyme-modified Alkaline Comet Assay for Measuring DNA Strand Breaks and Oxidative DNA Damage in Rat Liver

The alkaline comet assay measures DNA strand breaks in eukaryotic cells. By adding an Endonuclease III or human 8-oxoguanine-DNA-N-glycosylase digestion step, the assay can efficiently detect oxidative DNA damage. We describe methods for using these assays to detect DNA damage in rat liver.

Unrepaired DNA damage can lead to genetic instability, which in turn may enhance cancer development. Therefore, identifying potential DNA damaging agents ...

Amplification, Next-generation Sequencing, and Genomic DNA Mapping of Retroviral Integration Sites

Retroviruses exhibit signature integration preferences on both the local and global scales. Here, we present a detailed protocol for (1) generation of diverse libraries of retroviral integration sites using ligation-mediated PCR (LM-PCR) amplification and next-generation sequencing (NGS), (2) mapping the genomic location of each virus-host junction using BEDTools, and (3) analyzing the data for statistical relevance. Genomic DNA extracted from infected cells is fragmented by digestion with restriction enzymes or by sonication. After suitable DNA end-repair, double-stranded linkers are ligated onto the DNA ends, and semi-nested PCR is conducted using primers complementary to both the long terminal repeat (LTR) end of the virus and the ligated linker DNA. The PCR primers carry sequences required for DNA clustering during NGS, negating the requirement for separate adapter ligation. Quality control (QC) is conducted to assess DNA fragment size distribution and adapter DNA incorporation prior to NGS. Sequence output files are filtered for LTR-containing reads, and the sequences defining the LTR and the linker are cropped away. Trimmed host cell sequences are mapped to a reference genome using BLAT and are filtered for minimally 97% identity to a unique point in the reference genome. Unique integration sites are scrutinized for adjacent nucleotide (nt) sequence and distribution relative to various genomic features. Using this protocol, integration site libraries of high complexity can be constructed from genomic DNA in three days. The entire protocol that encompasses exogenous viral infection of susceptible tissue culture cells to integration site analysis can therefore be conducted in approximately one to two weeks. Recent applications of this technology pertain to longitudinal analysis of integration sites from HIV-infected patients.

We describe a protocol for amplifying retroviral integration sites from the genomic DNA of infected cells, sequencing the amplified virus-host junctions, and then mapping these sequences to a reference genome. We also describe techniques to quantify the distribution of integration sites relative to various genomic annotations using BEDTools.

Retroviruses exhibit signature integration preferences on both the local and global scales. Here, we present a detailed protocol for (1) generation of ...

Characterization of MLKL-mediated Plasma Membrane Rupture in Necroptosis

Necroptosis is a programmed cell death pathway triggered by activation of receptor interacting protein kinase 3 (RIPK3), which phosphorylates and activates the mixed lineage kinase-like domain pseudokinase, MLKL, to rupture or permeabilize the plasma membrane. Necroptosis is an inflammatory pathway associated with multiple pathologies including autoimmunity, infectious and cardiovascular diseases, stroke, neurodegeneration, and cancer. Here, we describe protocols that can be used to characterize MLKL as the executioner of plasma membrane rupture in necroptosis. We visualize the process of necroptosis in cells using live-cell imaging with conventional and confocal fluorescence&#160;microscopy, and in fixed cells using electron microscopy, which together revealed the redistribution of MLKL from the cytosol to the plasma membrane prior to induction of large holes in the plasma membrane. We present in vitro nuclear magnetic resonance (NMR) analysis using lipids to identify putative modulators of MLKL-mediated necroptosis. Based on this method, we identified quantitative lipid-binding preferences and phosphatidyl-inositol phosphates (PIPs) as critical binders of MLKL that are required for plasma membrane targeting and permeabilization in necroptosis.

We report methods for characterization of MLKL-mediated plasma membrane rupture in necroptosis including conventional and confocal live-cell microscopy imaging, scanning electron microscopy, and NMR-based lipid binding.

Necroptosis is a programmed cell death pathway triggered by activation of receptor interacting protein kinase 3 (RIPK3), which phosphorylates and ...

Loop-Mediated Isothermal Amplification for Screening Salmonella in Animal Food and Confirming Salmonella from Culture Isolation

Loop-mediated isothermal amplification (LAMP) has emerged as a powerful nucleic acid amplification test for the rapid detection of numerous bacterial, fungal, parasitic, and viral agents. Salmonella is a bacterial pathogen of worldwide food safety concern, including food for animals. Presented here is a multi-laboratory-validated Salmonella LAMP protocol that can be used to rapidly screen animal food for the presence of Salmonella contamination and can also be used to confirm presumptive Salmonella isolates recovered from all food categories. The LAMP assay specifically targets the Salmonella invasion gene (invA) and is rapid, sensitive, and highly specific. Template DNAs are prepared from enrichment broths of animal food or pure cultures of presumptive Salmonella isolates. The LAMP reagent mixture is prepared by combining an isothermal master mix, primers, DNA template, and water. The LAMP assay runs at a constant temperature of 65 &#176;C for 30 min. Positive results are monitored via real-time fluorescence and can be detected as early as 5 min. The LAMP assay exhibits high tolerance to inhibitors in animal food or culture medium, serving as a rapid, reliable, robust, cost-effective, and user-friendly method for screening and confirming Salmonella. The LAMP method has recently been incorporated into the U.S. Food and Drug Administration&#8217;s Bacteriological Analytical Manual (BAM) Chapter 5.

Loop-Mediated Isothermal Amplification for Screening Salmonella in Animal Food and Confirming Salmonella from Culture Isolation

Loop-mediated isothermal amplification (LAMP) is an isothermal nucleic acid amplification test (iNAAT) that has attracted broad interest in the pathogen detection field. Here, we present a multi-laboratory-validated Salmonella LAMP protocol as a rapid, reliable, and robust method for screening Salmonella in animal food and confirming presumptive Salmonella from culture isolation.

Loop-mediated isothermal amplification (LAMP) has emerged as a powerful nucleic acid amplification test for the rapid detection of numerous bacterial, ...