This work was supported by NIAMS (R01AR065523).

<ol>
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D., Hu, M., Ren, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome-wide+mapping+and+analysis+of+chromosome+architecture.">Genome-wide mapping and analysis of chromosome architecture.</a> Nature Reviews Molecular Cell Biology. 17 (12), 743-755 (2016).</li><li>Zhao, 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=Circular+chromosome+conformation+capture+(4C)+uncovers+extensive+networks+of+epigenetically+regulated+intra-+and+interchromosomal+interactions.">Circular chromosome conformation capture (4C) uncovers extensive networks of epigenetically regulated intra- and interchromosomal interactions.</a> Nature genetics. 38 (11), 1341-1347 (2006).</li><li>Splinter, E., de Wit, E., van de Werken, H. J. 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The authors declare that they have no competing financial interests.

4C results have the potential to reveal chromatin interactions that can identify previously unknown regulatory elements and/or target genes that are important in a specific biological context24,25,26. However, technical hurdles may limit the data obtained from these experiments. PCR bias stemming from over-amplification of template in 4C protocols is likely. This protocol addresses this issue by utilizing qPCR to determine the o...

The identification of regulatory elements for gene expression has been facilitated by the Encyclopedia of DNA Elements (ENCODE) Project that comprehensively annotated functional activity for 80% of the human genome1,2. The identification of the sites for in vivo transcription factor binding, DNaseI hypersensitivity, and epigenetic histone and DNA methylation modifications in individual cell types paved the way for the functional analyses of candidate regulatory elements for target gene expression. Armed with these findings, we are faced with the challenge of determining the functional interconnectivity between regulatory elements and genes. Specifically, what is the relationship between a given target gene and its enhancer(s)? The chromatin conformation capture (3C) method directly addresses this question by identifying physical, and likely functional, interactions between a region of interest and candidate interacting sequences through captured events in fixed chromatin3. As our understanding of chromatin interactions has increased, however, it is clear that the investigation of preselected candidate loci is insufficient to provide a complete understanding of gene-enhancer interactions. For example, ENCODE used the high-throughput chromosomal conformation capture carbon copy (5C) method to examine a small portion of the human genome (1%, pilot set of 44 loci) and reported complex interconnectivity of the loci. Genes and enhancers with identified interactions averaged 2&#8211;4 different interacting partners, many of which were hundreds of kilobases away in linear space4. Further, Li et al. used Chromatin Interaction Analysis by Paired-End Tag Sequencing (ChIA-PET) to analyze whole-genome promoter interactions and found that 65% of RNA polymerase II binding sites were involved in chromatin interactions. Some of these interactions resulted in large, multi-gene complexes spanning hundreds of kilobases of genomic distance and containing, on average, 8-9 genes each5. Together, these findings highlight the need for unbiased whole-genome methods for interrogating chromatin interactions. Some of these methods are reviewed in Schmitt et al.6.
More recent methods for chromatin conformation capture studies coupled with next-generation sequencing (Hi-C and 4C-seq) enable the discovery of unknown sequences interacting with a region of interest6. Specifically, circular chromosome conformation capture with next-generation sequencing (4C-seq) was developed to identify loci interacting with a sequence of interest in an unbiased manner7 by sequencing DNA from captured chromatin proximal to the region of interest in 3D space. Briefly, chromatin is fixed to preserve its native protein-DNA interactions, cleaved with a restriction enzyme, and subsequently ligated under dilute conditions to capture biologically relevant &#34;tangles&#34; of interacting loci (Figure 1). The cross links are reversed to remove the protein, thus leaving the DNA available for additional cleavage with a second restriction enzyme. A final ligation generates smaller circles of interacting loci. Primers to the sequence of interest are then used to generate an amplified library of unknown sequences from the circularized fragments, followed by downstream next generation sequencing.
The protocol presented here, which focuses on sample preparation, makes two major alterations to existing 4C-seq methods8,9,10,11,12. First, it uses a qPCR-based method to empirically determine the optimal number of amplification cycles for 4C-seq library preparation steps and thus mitigates the potential for PCR bias stemming from over-amplification of libraries. Second, it uses an additional restriction digest step in an effort to reduce the uniformity of known &#34;bait&#34; sequences that hinders accurate base-calling by the sequencing instrument and, hence, maximizes the unique, informative sequence in each read. Other protocols circumvent this issue by pooling many (12-15)8 4C-seq libraries with different bait sequences and/or restriction sites, a volume of experiments which may not be achievable by other laboratories. The modifications presented here allow a small number of experiments, samples, and/or replicates to be indexed and pooled into a single lane.

<table>
	<tbody>
		<tr>
			<td>HindIII</td>
			<td>NEB</td>
			<td>R0104S</td>
			<td></td>
		</tr>
		<tr>
			<td>CviQI</td>
			<td>NEB</td>
			<td>R0639S</td>
			<td></td>
		</tr>
		<tr>
			<td>DNA oligonucleotide primers</td>
			<td>IDT</td>
			<td></td>
			<td>To be designed by the reader</td>
		</tr>
		<tr>
			<td>50 mL conical centrifuge tubes</td>
			<td>Fisher Scientific</td>
			<td>06-443-19</td>
			<td></td>
		</tr>
		<tr>
			<td>1.7 mL microcentrifuge tubes</td>
			<td>MidSci</td>
			<td>AVSS1700</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline</td>
			<td>Thermo Fisher</td>
			<td>14190-136</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde, methanol free</td>
			<td>Electron Microscopy Sciences</td>
			<td>15710</td>
			<td></td>
		</tr>
		<tr>
			<td>Nutator</td>
			<td>VWR</td>
			<td>15172-203</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>JT Baker</td>
			<td>4059-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Benchtop centrifuge</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Refrigerated microcentrifuge</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylenediaminetetraacetic acid (EDTA)</td>
			<td>Sigma-Aldrich</td>
			<td>ED2SS</td>
			<td></td>
		</tr>
		<tr>
			<td>20% SDS solution</td>
			<td>Sigma-Aldrich</td>
			<td>05030</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan Blue</td>
			<td>Thermo Fisher</td>
			<td>15250061</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass slides</td>
			<td>Fisher Scientific</td>
			<td>12-550-143</td>
			<td></td>
		</tr>
		<tr>
			<td>Cover slips</td>
			<td>VWR</td>
			<td>16004-094</td>
			<td></td>
		</tr>
		<tr>
			<td>Light microscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Alfa Aesar</td>
			<td>A16046</td>
			<td></td>
		</tr>
		<tr>
			<td>Shaking heat block</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2M Tris-HCl</td>
			<td>Quality Biological</td>
			<td>351-048-101</td>
			<td></td>
		</tr>
		<tr>
			<td>Proteinase K</td>
			<td>NEB</td>
			<td>P8107S</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenol:chloroform:isoamyl alcohol (25:24:1)</td>
			<td>Sigma-Aldrich</td>
			<td>P2069</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium acetate</td>
			<td>Sigma-Aldrich</td>
			<td>M5661</td>
			<td></td>
		</tr>
		<tr>
			<td>20 mg/mL glycogen</td>
			<td>Thermo Fisher</td>
			<td>R0561</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Fisher Scientific</td>
			<td>04-355-223</td>
			<td></td>
		</tr>
		<tr>
			<td>Nuclease-free water</td>
			<td>Fisher Scientific</td>
			<td>MT-46-000-CM</td>
			<td></td>
		</tr>
		<tr>
			<td>qPCR cycler</td>
			<td>Thermo Fisher</td>
			<td>4453536</td>
			<td></td>
		</tr>
		<tr>
			<td>qPCR plates</td>
			<td>Thermo Fisher</td>
			<td>4309849</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermocycler</td>
			<td>Thermo Fisher</td>
			<td>4375786</td>
			<td></td>
		</tr>
		<tr>
			<td>PCR strip tubes</td>
			<td>MidSci</td>
			<td>AVSST-FL</td>
			<td></td>
		</tr>
		<tr>
			<td>1M Magnesium chloride</td>
			<td>Quality Biological</td>
			<td>351-033-721</td>
			<td></td>
		</tr>
		<tr>
			<td>Dithiothreotol</td>
			<td>Sigma-Aldrich</td>
			<td>43815</td>
			<td></td>
		</tr>
		<tr>
			<td>Adenosine triphosphate</td>
			<td>Sigma-Aldrich</td>
			<td>A2383</td>
			<td></td>
		</tr>
		<tr>
			<td>T4 DNA Ligase</td>
			<td>NEB</td>
			<td>M0202S</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Sigma-Aldrich</td>
			<td>A6013</td>
			<td></td>
		</tr>
		<tr>
			<td>RNase A</td>
			<td>Thermo Fisher</td>
			<td>EN0531</td>
			<td></td>
		</tr>
		<tr>
			<td>Qiaquick PCR purification kit</td>
			<td>Qiagen</td>
			<td>28104</td>
			<td></td>
		</tr>
		<tr>
			<td>MinElute PCR Purification kit</td>
			<td>Qiagen</td>
			<td>28004</td>
			<td></td>
		</tr>
		<tr>
			<td>Spectrophotometer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Expand Long Template PCR System</td>
			<td>Sigma-Aldrich</td>
			<td>11681834001</td>
			<td></td>
		</tr>
		<tr>
			<td>dNTP mix</td>
			<td>Thermo Fisher</td>
			<td>R0191</td>
			<td></td>
		</tr>
		<tr>
			<td>SYBR Green I</td>
			<td>Sigma-Aldrich</td>
			<td>S9430</td>
			<td></td>
		</tr>
		<tr>
			<td>ROX</td>
			<td>BioRad</td>
			<td>172-5858</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Sigma-Aldrich</td>
			<td>S5886</td>
			<td></td>
		</tr>
		<tr>
			<td>End-It DNA End-Repair Kit</td>
			<td>Lucigen</td>
			<td>ER0720</td>
			<td></td>
		</tr>
		<tr>
			<td>LigaFast Rapid DNA Ligation System</td>
			<td>Promega</td>
			<td>M8221</td>
			<td></td>
		</tr>
		<tr>
			<td>SYBR Safe</td>
			<td>Thermo Fisher</td>
			<td>S33102</td>
			<td></td>
		</tr>
		<tr>
			<td>Taq Polymerase</td>
			<td>NEB</td>
			<td>M0267S</td>
			<td></td>
		</tr>
		<tr>
			<td>UltraSieve Agarose</td>
			<td>IBI Scientific</td>
			<td>IB70054</td>
			<td></td>
		</tr>
		<tr>
			<td>Qiaquick Gel Extraction Kit</td>
			<td>Qiagen</td>
			<td>28704</td>
			<td></td>
		</tr>
	</tbody>
</table>

high-throughput identification of gene regulatory sequences using next-generation sequencing of circular chromosome conformation capture (4c-seq)

The identification of regulatory elements for a given target gene poses a significant technical challenge owing to the variability in the positioning and effect sizes of regulatory elements to a target gene. Some progress has been made with the bioinformatic prediction of the existence and function of proximal epigenetic modifications associated with activated gene expression using conserved transcription factor binding sites. Chromatin conformation capture studies have revolutionized our ability to discover physical chromatin contacts between sequences and even within an entire genome. Circular chromatin conformation capture coupled with next-generation sequencing (4C-seq), in particular, is designed to discover all possible physical chromatin interactions for a given sequence of interest (viewpoint), such as a target gene or a regulatory enhancer. Current 4C-seq strategies directly sequence from within the viewpoint but require numerous and diverse viewpoints to be simultaneously sequenced to avoid the technical challenges of uniform base calling (imaging) with next generation sequencing platforms. This volume of experiments may not be practical for many laboratories. Here, we report a modified approach to the 4C-seq protocol that incorporates both an additional restriction enzyme digest and qPCR-based amplification steps that are designed to facilitate a greater capture of diverse sequence reads and mitigate the potential for PCR bias, respectively. Our modified 4C method is amenable to the standard molecular biology lab for assessing chromatin architecture.

Primary human keratinocytes were isolated from 2&#8211;3 discarded neonatal foreskins, pooled, and cultured in KSFM supplemented with 30 &#181;g/mL bovine pituitary extract, 0.26 ng/mL recombinant human epidermal growth factor, and 0.09 mM calcium chloride (CaCl2) at 37 &#176;C, 5% carbon dioxide. The cells were split into two flasks, and one flask was differentiated by the addition of CaCl2 to a final concentration of 1.2 mM for 72 h. 107 cells each from ...

Watch this Scientific Journal Video about High-throughput Identification of Gene Regulatory Sequences Using Next-generation Sequencing of Circular Chromosome Conformation Capture 4C-seq at JoVE.com

High-throughput Identification of Gene Regulatory Sequences Using Next-generation Sequencing of Circular Chromosome Conformation Capture 4C-seq

The identification of physical interactions between genes and regulatory elements is challenging but has been facilitated by chromosome conformation capture methods. This modification to the 4C-seq protocol mitigates PCR bias by minimizing over-amplification of PCR templates and maximizes the mappability of reads by incorporating an addition restriction enzyme digest step.

High-throughput Identification of Gene Regulatory Sequences Using Next-generation Sequencing of Circular Chromosome Conformation Capture (4C-seq)

The identification of regulatory elements for a given target gene poses a significant technical challenge owing to the variability in the positioning and ...

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Research

JoVE Journal

Genetics

10.1K Views.  Washington University School of Medicine. The identification of physical interactions between genes and regulatory elements is challenging but has been facilitated by chromosome conformation capture methods. This modification to the 4C-seq protocol mitigates PCR bias by minimizing over-amplification of PCR templates and maximizes the mappability of reads by incorporating an addition restriction enzyme digest step.

Video: High-throughput Identification of Gene Regulatory Sequences Using Next-generation Sequencing of Circular Chromosome Conformation Capture 4C-seq

Optimization and Comparative Analysis of Plant Organellar DNA Enrichment Methods Suitable for Next-generation Sequencing

Plant organellar genomes contain large, repetitive elements that may undergo pairing or recombination to form complex structures and/or sub-genomic fragments. Organellar genomes also exist in admixtures within a given cell or tissue type (heteroplasmy), and an abundance of subtypes may change throughout development or when under stress (sub-stoichiometric shifting). Next-generation sequencing (NGS) technologies are required to obtain deeper understanding of organellar genome structure and function. Traditional sequencing studies use several methods to obtain organellar DNA: (1) If a large amount of starting tissue is used, it is homogenized and subjected to differential centrifugation and/or gradient purification. (2) If a smaller amount of tissue is used (i.e., if seeds, material, or space is limited), the same process is performed as in (1), followed by whole-genome amplification to obtain sufficient DNA. (3) Bioinformatics analysis can be used to sequence the total genomic DNA and to parse out organellar reads. All these methods have inherent challenges and tradeoffs. In (1), it may be difficult to obtain such a large amount of starting tissue; in (2), whole-genome amplification could introduce a sequencing bias; and in (3), homology between nuclear and organellar genomes could interfere with assembly and analysis. In plants with large nuclear genomes, it is advantageous to enrich for organellar DNA to reduce sequencing costs and sequence complexity for bioinformatics analyses. Here, we compare a traditional differential centrifugation method with a fourth method, an adapted CpG-methyl pulldown approach, to separate the total genomic DNA into nuclear and organellar fractions. Both methods yield sufficient DNA for NGS, DNA that is highly enriched for organellar sequences, albeit at different ratios in mitochondria and chloroplasts. We present the optimization of these methods for wheat leaf tissue and discuss major advantages and disadvantages of each approach in the context of sample input, protocol ease, and downstream application.

The comparison and optimization of two plant organellar DNA enrichment methods are presented: traditional differential centrifugation and fractionation of the total gDNA based on methylation status. We assess the resulting DNA quantity and quality, demonstrate performance in short-read next-generation sequencing, and discuss the potential for use in long-read single-molecule sequencing.

Plant organellar genomes contain large, repetitive elements that may undergo pairing or recombination to form complex structures and/or sub-genomic ...

Generation of Native Chromatin Immunoprecipitation Sequencing Libraries for Nucleosome Density Analysis

We present a modified native chromatin immunoprecipitation sequencing (ChIP-seq) experimental protocol compatible with a Gaussian mixture distribution based analysis methodology (nucleosome density ChIP-seq; ndChIP-seq) that enables the generation of combined measurements of micrococcal nuclease (MNase) accessibility with histone modification genome-wide. Nucleosome position and local density, and the posttranslational modification of their histone subunits, act in concert to regulate local transcription states. Combinatorial measurements of nucleosome accessibility with histone modification generated by ndChIP-seq allows for the simultaneous interrogation of these features. The ndChIP-seq methodology is applicable to small numbers of primary cells inaccessible to cross-linking based ChIP-seq protocols. Taken together, ndChIP-seq enables the measurement of histone modification in combination with local nucleosome density to obtain new insights into shared mechanisms that regulate RNA transcription within rare primary cell populations.

We present a modified native chromatin immunoprecipitation sequencing (ChIP-seq) methodology for the generation of sequence datasets suitable for a nucleosome density ChIP-seq analytical framework integrating micrococcal nuclease (MNase) accessibility with histone modification measurements.

We present a modified native chromatin immunoprecipitation sequencing (ChIP-seq) experimental protocol compatible with a Gaussian mixture distribution ...

Robust DNA Isolation and High-throughput Sequencing Library Construction for Herbarium Specimens

Herbaria are an invaluable source of plant material that can be used in a variety of biological studies. The use of herbarium specimens is associated with a number of challenges including sample preservation quality, degraded DNA, and destructive sampling of rare specimens. In order to more effectively use herbarium material in large sequencing projects, a dependable and scalable method of DNA isolation and library preparation is needed. This paper demonstrates a robust, beginning-to-end protocol for DNA isolation and high-throughput library construction from herbarium specimens that does not require modification for individual samples. This protocol is tailored for low quality dried plant material and takes advantage of existing methods by optimizing tissue grinding, modifying library size selection, and introducing an optional reamplification step for low yield libraries. Reamplification of low yield DNA libraries can rescue samples derived from irreplaceable and potentially valuable herbarium specimens, negating the need for additional destructive sampling and without introducing discernible sequencing bias for common phylogenetic applications. The protocol has been tested on hundreds of grass species, but is expected to be adaptable for use in other plant lineages after verification. This protocol can be limited by extremely degraded DNA, where fragments do not exist in the desired size range, and by secondary metabolites present in some plant material that inhibit clean DNA isolation. Overall, this protocol introduces a fast and comprehensive method that allows for DNA isolation and library preparation of 24 samples in less than 13 h, with only 8 h of active hands-on time with minimal modifications.

This article demonstrates a detailed protocol for DNA isolation and high-throughput sequencing library construction from herbarium material including rescue of exceptionally poor-quality DNA.

Herbaria are an invaluable source of plant material that can be used in a variety of biological studies. The use of herbarium specimens is associated with ...

Generation of Genome-wide Chromatin Conformation Capture Libraries from Tightly Staged Early Drosophila Embryos

Investigating the three-dimensional architecture of chromatin offers invaluable insight into the mechanisms of gene regulation. Here, we describe a protocol for performing the chromatin conformation capture technique in situ Hi-C on staged Drosophila melanogaster embryo populations. The result is a sequencing library that allows the mapping of all chromatin interactions that occur in the nucleus in a single experiment. Embryo sorting is done manually using a fluorescent stereo microscope and a transgenic fly line containing a nuclear marker. Using this technique, embryo populations from each nuclear division cycle, and with defined cell cycle status, can be obtained with very high purity. The protocol may also be adapted to sort older embryos beyond gastrulation. Sorted embryos are used as inputs for in situ Hi-C. All experiments, including sequencing library preparation, can be completed in five days. The protocol has low input requirements and works reliably using 20 blastoderm stage embryos as input material. The end result is a sequencing library for next generation sequencing. After sequencing, the data can be processed into genome-wide chromatin interaction maps that can be analyzed using a wide range of available tools to gain information about topologically associating domain (TAD) structure, chromatin loops, and chromatin compartments during Drosophila development.

Generation of Genome-wide Chromatin Conformation Capture Libraries from Tightly Staged Early Drosophila Embryos

This work describes a protocol for the generation of high resolution in situ Hi-C libraries from tightly staged pre-gastrulation Drosophila melanogaster embryos.

Investigating the three-dimensional architecture of chromatin offers invaluable insight into the mechanisms of gene regulation. Here, we describe a ...

High-throughput Identification of Synergistic Drug Combinations by the Overlap2 Method

Although antimicrobial drugs have dramatically increased the lifespan and quality of life in the 20th century, antimicrobial resistance threatens our entire society's ability to treat systemic infections. In the United States alone, antibiotic-resistant infections kill approximately 23,000 people a year and cost around 20 billion USD in additional healthcare. One approach to combat antimicrobial resistance is combination therapy, which is particularly useful in the critical early stage of infection, before the infecting organism and its drug resistance profile have been identified. Many antimicrobial treatments use combination therapies. However, most of these combinations are additive, meaning that the combined efficacy is the same as the sum of the individual antibiotic efficacy. Some combination therapies are synergistic: the combined efficacy is much greater than additive. Synergistic combinations are particularly useful because they can inhibit the growth of antimicrobial drug resistant strains. However, these combinations are rare and difficult to identify. This is due to the sheer number of molecules needed to be tested in a pairwise manner: a library of 1,000 molecules has 1 million potential combinations. Thus, efforts have been made to predict molecules for synergy. This article describes our high-throughput method for predicting synergistic small molecule pairs known as the Overlap2 Method (O2M). O2M uses patterns from chemical-genetic datasets to identify mutants that are hypersensitive to each molecule in a synergistic pair but not to other molecules. The Brown lab exploits this growth difference by performing a high-throughput screen for molecules that inhibit the growth of mutant but not wild-type cells. The lab's work previously identified molecules that synergize with the antibiotic trimethoprim and the antifungal drug fluconazole using this strategy. Here, the authors present a method to screen for novel synergistic combinations, which can be altered for multiple microorganisms.

High-throughput Identification of Synergistic Drug Combinations by the Overlap2 Method

Synergistic drug combinations are difficult and time-consuming to identify empirically. Here, we describe a method for identifying and validating synergistic small molecules.

Although antimicrobial drugs have dramatically increased the lifespan and quality of life in the 20th century, antimicrobial resistance threatens our ...

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

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

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

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

Amplification of Near Full-length HIV-1 Proviruses for Next-Generation Sequencing

The Full-Length Individual Proviral Sequencing (FLIPS) assay is an efficient and high-throughput method designed to amplify and sequence single, near full-length (intact and defective), HIV-1 proviruses. FLIPS allows determination of the genetic composition of integrated HIV-1 within a cell population. Through identifying defects within HIV-1 proviral sequences that arise during reverse transcription, such as large internal deletions, deleterious stop codons/hypermutation, frameshift mutations, and mutations/deletions in cis acting elements required for virion maturation, FLIPS can identify integrated proviruses incapable of replication. The FLIPS assay can be utilized to identify HIV-1 proviruses that lack these defects and are&#160;therefore potentially replication-competent. The FLIPS protocol involves: lysis of HIV-1 infected cells, nested PCR of near full-length HIV-1 proviruses (using primers targeted to the HIV-1 5&#39; and 3&#39; LTR), DNA purification and quantification, library preparation for Next-generation Sequencing (NGS), NGS, de novo assembly of proviral contigs, and a simple process of elimination for identifying replication-competent proviruses. FLIPS provides advantages over traditional methods designed to sequence integrated HIV-1 proviruses, such as single-proviral sequencing. FLIPS amplifies and sequences near full-length proviruses enabling replication competency to be determined, and also uses fewer amplification primers, preventing the consequences of primer mismatches. FLIPS is a useful tool for understanding the genetic landscape of integrated HIV-1 proviruses, especially within the latent reservoir, however, its utilization can extend to any application in which the genetic composition of integrated HIV-1 is required.

Full-length individual proviral sequencing (FLIPS) provides an efficient and high-throughput method for the amplification and sequencing of single, near full-length (intact and defective) HIV-1 proviruses and allows for determination of their potential replication-competency. FLIPS overcomes limitations of previous assays designed to sequence the latent HIV-1 reservoir.

The Full-Length Individual Proviral Sequencing (FLIPS) assay is an efficient and high-throughput method designed to amplify and sequence single, near ...

RNA Next-Generation Sequencing and a Bioinformatics Pipeline to Identify Expressed LINE-1s at the Locus-Specific Level

Long INterspersed Elements-1 (LINEs/L1s) are repetitive elements that can copy and randomly insert in the genome resulting in genomic instability and mutagenesis. Understanding the expression patterns of L1 loci at the individual level will lend to the understanding of the biology of this mutagenic element. This autonomous element makes up a significant portion of the human genome with over 500,000 copies, though 99% are truncated and defective. However, their abundance and dominant number of defective copies make it challenging to identify authentically expressed L1s from L1-related sequences expressed as part of other genes. It is also challenging to identify which specific L1 locus is expressed due to the repetitive nature of the elements. Overcoming these challenges, we present an RNA-Seq bioinformatic approach to identify L1 expression at the locus specific level. In summary, we collect cytoplasmic RNA, select for polyadenylated transcripts, and utilize strand-specific RNA-Seq analyses to uniquely map reads to L1 loci in the human reference genome. We visually curate each L1 locus with uniquely mapped reads to confirm transcription from its own promoter and adjust mapped transcript reads to account for mappability of each individual L1 locus. This approach was applied to a prostate tumor cell line, DU145, to demonstrate the ability of this protocol to detect expression from a small number of the full-length L1 elements.

Here, we present a bioinformatic approach and analyses to identify LINE-1 expression at the locus specific level.

Long INterspersed Elements-1 (LINEs/L1s) are repetitive elements that can copy and randomly insert in the genome resulting in genomic instability and ...

Identification of Circular RNAs using RNA Sequencing

Circular RNAs (circRNAs) are a class of non-coding RNAs involved in functions including micro-RNA (miRNA) regulation, mediation of protein-protein interactions, and regulation of parental gene transcription. In classical next generation RNA sequencing (RNA-seq), circRNAs are typically overlooked as a result of poly-A selection during construction of mRNA libraries, or are found at very low abundance, and are therefore difficult to isolate and detect. Here, a circRNA library construction protocol was optimized by comparing library preparation kits, pre-treatment options and various total RNA input amounts. Two commercially available whole transcriptome library preparation kits, with and without RNase R pre-treatment, and using variable amounts of total RNA input (1 to 4 &#181;g), were tested. Lastly, multiple tissue types; including liver, lung, lymph node, and pancreas; as well as multiple brain regions; including the cerebellum, inferior parietal lobe, middle temporal gyrus, occipital cortex, and superior frontal gyrus; were compared to evaluate circRNA abundance across tissue types. Analysis of the generated RNA-seq data using six different circRNA detection tools (find_circ, CIRI, Mapsplice, KNIFE, DCC, and CIRCexplorer) revealed that a stranded total RNA library preparation kit with RNase R pre-treatment and 4 &#181;g RNA input is the optimal method for identifying the highest relative number of circRNAs. Consistent with previous findings, the highest enrichment of circRNAs was observed in brain tissues compared to other tissue types.

Circular RNAs (circRNAs) are non-coding RNAs that may have roles in transcriptional regulation and mediating interactions between proteins. Following assessment of different parameters for construction of circRNA sequencing libraries, a protocol was compiled utilizing stranded total RNA library preparation with RNase R pre-treatment and is presented here.

Circular RNAs (circRNAs) are a class of non-coding RNAs involved in functions including micro-RNA (miRNA) regulation, mediation of protein-protein ...

Discovering CsgD Regulatory Targets in Salmonella Biofilm Using Chromatin Immunoprecipitation and High-Throughput Sequencing (ChIP-seq)

Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is a technique that can be used to discover the regulatory targets of transcription factors, histone modifications, and other DNA-associated proteins. ChIP-seq data can also be used to find differential binding of transcription factors in different environmental conditions or cell types. Initially, ChIP was performed through hybridization on a microarray (ChIP-chip); however, ChIP-seq has become the preferred method through technological advancements, decreasing financial barriers to sequencing, and massive amounts of high-quality data output. Techniques of performing ChIP-seq with bacterial biofilms, a major source of persistent and chronic infections, are described in this protocol. ChIP-seq is performed on Salmonella enterica serovar Typhimurium biofilm and planktonic cells, targeting the master biofilm regulator, CsgD, to determine differential binding in the two cell types. Here, we demonstrate the appropriate amount of biofilm to harvest, normalizing to a planktonic control sample, homogenizing biofilm for cross-linker access, and performing routine ChIP-seq steps to obtain high quality sequencing results.

Discovering CsgD Regulatory Targets in Salmonella Biofilm Using Chromatin Immunoprecipitation and High-Throughput Sequencing ChIP-seq

Chromatin immunoprecipitation coupled with next-generation sequencing (ChIP-seq) is a method used to establish interactions between transcription factors and the genomic sequences they control. This protocol outlines techniques for performing ChIP-seq with bacterial biofilms, using Salmonella enterica serovar Typhimurium bacterial biofilm as an example.

Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is a technique that can be used to discover the regulatory targets of transcription ...