Next-generation Sequencing Library Preparation Research Articles

Microfluidic Platform for Next-Generation Sequencing Library Preparation with Low-Input Samples.

Advances in next-generation sequencing (NGS) have made available a wealth of information that had previously been inaccessible to researchers and clinicians. NGS has been applied to understand genomic, transcriptomic, and epigenomic changes and gained traction as a significant tool capable of accelerating diagnosis, prognosis, and biomarker discovery. However, these NGS assays have yet to be practical methods for patient stratification or diagnosis because of the gap between the tiny quantities of biomaterials provided by a clinical sample and the large DNA input required by most of these assays. Current library preparation methodologies typically require large input amounts of DNA and a long and complicated manual process. Here, we present a microfluidic droplet-based system for NGS library preparation, capable of reducing the number of pipetting steps significantly, reducing reagent consumption by 10×, andautomating much of the process, while supporting an extremely low DNA input requirement (10 pg per library). This semiautomated technology will allow for low-input preparations of 8 libraries simultaneously while reducing batch-to-batch variation and operator hands-on time.

Development and Analytical Validation of an Expanded Mutation Detection Panel for Next-Generation Sequencing of Thyroid Nodule Aspirates

Molecular analysis is used to evaluate the risk of malignancy for thyroid fine-needle aspirates, identified as indeterminate by microscopic cytology, on the basis of the detection of various oncogenic DNA mutations and fusion transcripts or on the use of various mRNAs or miRNA-based classifier algorithms. Our approach has been to use a combination test using the detection of oncogenic mutations/fusion transcripts and an miRNA expression-based classifier algorithm. To improve the performance of the combination test, the next-generation sequencing (NGS)-based mutational panel was expanded from the detection of 5 oncogenes to 10 oncogenes and tumor suppressor genes and the detection of fusion transcripts was increased from 6 to 38. Herein, we describe the assay development of the expanded panel NGS test and optimization of various steps for the library preparation of multiplexed target genes to maintain quality parameters for sequencing and to improve the robustness of the test for use in clinical testing in a College of American Pathologists/Clinical Laboratory Improvements Amendments-certified laboratory. Technical hurdles in NGS library preparation for the sequencing of both normal and high guanine-cytosine-rich regions, and balanced amplification of various amplicons in highly multiplexed PCRs, were successfully overcome. Analytical validation as a laboratory-developed test (ThyGeNEXT) included the demonstration of assay reproducibility, lower limit of detection, as well as other fundamental quality parameters.

Technical advance in targeted NGS analysis enables identification of lung cancer risk-associated low frequency TP53, PIK3CA, and BRAF mutations in airway epithelial cells

BackgroundStandardized Nucleic Acid Quantification for SEQuencing (SNAQ-SEQ) is a novel method that utilizes synthetic DNA internal standards spiked into each sample prior to next generation sequencing (NGS) library preparation. This method was applied to analysis of normal appearing airway epithelial cells (AEC) obtained by bronchoscopy in an effort to define a somatic mutation field effect associated with lung cancer risk. There is a need for biomarkers that reliably detect those at highest lung cancer risk, thereby enabling more effective screening by annual low dose CT. The purpose of this study was to test the hypothesis that lung cancer risk is characterized by increased prevalence of low variant allele frequency (VAF) somatic mutations in lung cancer driver genes in AEC.MethodsSynthetic DNA internal standards (IS) were prepared for 11 lung cancer driver genes and mixed with each AEC genomic (g) DNA specimen prior to competitive multiplex PCR amplicon NGS library preparation. A custom Perl script was developed to separate IS reads and respective specimen gDNA reads from each target into separate files for parallel variant frequency analysis. This approach identified nucleotide-specific sequencing error and enabled reliable detection of specimen mutations with VAF as low as 5 × 10− 4 (0.05%). This method was applied in a retrospective case-control study of AEC specimens collected by bronchoscopic brush biopsy from the normal airways of 19 subjects, including eleven lung cancer cases and eight non-cancer controls, and the association of lung cancer risk with AEC driver gene mutations was tested.ResultsTP53 mutations with 0.05–1.0% VAF were more prevalent (p < 0.05) and also enriched for tobacco smoke and age-associated mutation signatures in normal AEC from lung cancer cases compared to non-cancer controls matched for smoking and age. Further, PIK3CA and BRAF mutations in this VAF range were identified in AEC from cases but not controls.ConclusionsApplication of SNAQ-SEQ to measure mutations in the 0.05–1.0% VAF range enabled identification of an AEC somatic mutation field of injury associated with lung cancer risk. A biomarker comprising TP53, PIK3CA, and BRAF somatic mutations may better stratify individuals for optimal lung cancer screening and prevention outcomes.

Co-occurring genetic alterations and primary EGFR T790M mutations detected by NGS in pre-TKI-treated NSCLCs.

Next-generation sequencing (NGS)-based assays to understand various mutations and co-occurrence of genomic alterations in non-small cell lung cancer (NSCLC) have enabled understanding of treatment impact on clinical outcomes. This retrospective study was conducted in 1353 formalin-fixed paraffin-embedded (FFPE) tissues from surgically resected, pre-TKI-treated NSCLC patients with identified gene alterations. Genomic DNA and RNA extraction was followed by NGS library preparation and sequencing using the Ion Ampliseq Colon and Lung Cancer Gene Panel V2 and the AmpliSeq RNA Lung Cancer Research Fusion Panel. A total of 2328 alterations in 25 genes were detected from the 1293 patients. DNA mutations and RNA fusions co-occurred in 27 patients with TP53 being the most common co-occurring DNA mutation (43.8%) with concurrent ALK fusions. Analysis of the 975 patients with EGFR mutations revealed that the incidence of dual EGFR L858R/T790M mutations was higher compared to EGFR 19del/T790M, and the mean allele fraction (MAF) of T790M was lower compared to 19del in dual EGFR 19del/T790M patients. NSCLC patients represented genetically heterogeneous subgroup with a high frequency of co-occurring mutations in cancer-associated pathways. This diverse mutational profile may have key clinical and research implications for understanding the variability of treatment outcome in pre-TKI-treated NSCLC population. The differences in the MAF of EGFR T790M may determine different responses to TKI therapy in patients harboring dual mutations.

A Practical Guide to the Measurement and Analysis of DNA Methylation.

DNA methylation represents a fundamental epigenetic mark that is associated with transcriptional repression during development, maintenance of homeostasis, and disease. In addition to methylation-sensitive PCR and targeted deep-amplicon bisulfite sequencing to measure DNA methylation at defined genomic loci, numerous unsupervised techniques exist to quantify DNA methylation on a genome-wide scale, including affinity enrichment strategies and methods involving bisulfite conversion. Both affinity-enriched and bisulfite-converted DNA can serve as input material for array hybridization or sequencing using next-generation technologies. In this practical guide to the measurement and analysis of DNA methylation, the goal is to convey basic concepts in DNA methylation biology and explore genome-scale bisulfite sequencing as the current gold standard for assessment of DNA methylation. Bisulfite conversion chemistry and library preparation are discussed in addition to a bioinformatics approach to quality assessment, trimming, alignment, and methylation calling of individual cytosine residues. Bisulfite-converted DNA presents challenges for standard next-generation sequencing library preparation protocols and data-processing pipelines, but these challenges can be met with elegant solutions that leverage the power of high-performance computing systems. Quantification of DNA methylation, data visualization, statistical approaches to compare DNA methylation between sample groups, and examples of integrating DNA methylation data with other -omics data sets are also discussed. The reader is encouraged to use this article as a foundation to pursue advanced topics in DNA methylation measurement and data analysis, particularly the application of bioinformatics and computational biology principles to generate a deeper understanding of mechanisms linking DNA methylation to cellular function.

P.295Linked-read whole genome sequencing in patients with congenital myopathy

Over the past decade, Next Generation Sequencing (NGS) methods have revolutionised the field of genetics. Currently, the usage of Whole Genome Sequencing (WGS) in addition to Whole Exome Sequencing (WES) and panel sequencing is increasing in research and in clinical diagnostics. In this study, we wanted to test whether a new NGS application — the Linked-Read (LR) library preparation — can improve the identification of disease-causing variants in patients with congenital myopathy. For LR library preparation, gDNA molecules are encapsulated inside emulsion droplets. Every microreaction provides a unique barcode to each of the DNA fragments inside the droplet. In the data analysis step, the barcoded short-read sequences are linked up to each other, providing long-range information. In addition to regular WGS information, this enables the identification of structural variants such as insertions or translocations. It also resolves the haplotypes of the patient. Moreover, LRs have the potential to improve the short-read alignment of repetitive regions in genes such as nebulin and titin. We selected three patients with a congenital myopathy for this pilot study. The prior analysis using targeted Sanger sequencing of candidate genes, a custom neuromuscular gene panel or WES had failed to identify the genetic cause of their disorder. Furthermore, all patient samples had previously been analysed for Copy Number Variation (CNV) using a Comparative Genomic Hybridisation array (CGH-array) for neuromuscular disorders designed by our group, but the molecular diagnosis had remained unresolved. Our preliminary results indicate that LR NGS library preparation method adds valuable information, especially of structural variation, and is likely to improve the diagnostics of neuromuscular disorders.

Comparison of seven methods for DNA extraction from prosomata of the acorn barnacle, Amphibalanus amphitrite

Next generation sequencing (NGS) technologies can provide an understanding of the molecular processes involved in marine fouling by Amphibalanus spp. barnacles. Here, seven methods for extracting DNA from A. amphitrite prosomata were assessed with respect to recovery, purity and size distribution. Methods incorporating organic extractions generally resulted in low recovery of fragmented DNA. The most promising method was the commercial E.Z.N.A. Blood DNA Mini kit, which provided tens of micrograms of DNA of sufficient molecular weight for use in long-read NGS library preparation. Other kits resulted in DNA preps suitable for short read length NGS platforms.

Short DNA Probes Developed for Sample Tracking and Quality Assurance in Gene Panel Testing

Both multiplexing and target-enrichment technologies are key to reducing the cost of genetic testing using next-generation sequencing (NGS). Many diagnostic laboratories routinely handle thousands of targeted resequencing samples, leading to an increased risk of accidental sample mix-ups and cross contamination. Herein, we present a short DNA fragment that can be spiked into the original genomic DNA (gDNA) or whole blood sample and tracked through to the final targeted resequencing data. This DNA fragment comprises a 15-bp unique index sequence assembled with a 120-bp fixed sequence designed for recovery in a hybridization capture reaction. In a pilot study, the yield of the recovered probe was examined in a step-by-step genetic testing procedure, involving gDNA isolation from whole blood, library preparation for NGS, and capture hybridization. On the basis of the results, 10 fmol (6×109 molecules) and 10 amol (6×106 molecules) of the spike-in probe were estimated to be suitable for DNA and RNA probe-based library preparation and target enrichment from 200 ng (6.5×104 copies) gDNA, respectively. In fact, the number of NGS reads corresponding to the spike-in probe was almost equal to that corresponding to the genomic target regions and was sufficient for evaluating sample identification and cross-contamination events. Hence, this method may be useful for enhancing quality assurance in clinical genetic testing.

Abstract 3522: Enzymatic DNA repair enables high quality library preparation and accurate sequencing from highly damaged DNA inputs

Abstract High-throughput sequencing is key for clinical diagnostic applications such as disease mutation profiling and identifying pathogens with high taxonomic specificity. Preparation of high quality next-generation sequencing (NGS) libraries is critical for obtaining accurate patient data, but clinical scientists are often limited by input DNA quality. In cancer genomics, formalin-fixed, paraffin-embedded (FFPE) tissue from patient biopsy is a common source of DNA, but the extracted DNA is often poor in both yield and quality due to fixation- and storage-induced damage. Additionally, these damage-induced sequencing artifacts raise the background level of mutations, making it difficult to discern true, low frequency, disease-related variants from noise. Even relatively high-quality DNA inputs contain nicks and gaps limiting library yields and read lengths for long read sequencing platforms including Oxford Nanopore Technologies (ONT) and Pacific Biosciences (PacBio). We developed a second-generation DNA repair enzyme mix (V2) that efficiently repairs the most prevalent damage types found in FFPE DNA and further improves the quality and yield of NGS libraries through efficient nick and gap repair. Illumina library yield and quality were improved when DNA samples were treated with FFPE DNA Repair V2 before library preparation. Target enrichment and whole exome enrichment experiments showed that the V2 repair mix did not alter the overall frequency of variants identified, thus it did not introduce bias, but significantly improved the sequencing accuracy by reducing the number of false variant calls due to damage-induced sequence artifacts. True mutation frequencies were validated using droplet digital PCR (ddPCR). Repaired ONT libraries using DNA inputs of varying quality also showed improved library quality as well as greater read lengths. Therefore, enzymatic DNA repair prior to NGS library preparation is a critical first step for improving the quality and accuracy of short- and long-read sequencing libraries. Citation Format: Margaret R. Heider, Lixin Chen, Chen Song, Luo Sun, Pingfang Liu, Laurence Ettwiller, Lauren Higgins, Eileen Dimalanta, Theodore Davis, Thomas Evans. Enzymatic DNA repair enables high quality library preparation and accurate sequencing from highly damaged DNA inputs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3522.

Abstract 3007: Validation of an NGS panel assay for detection of hotspot cancer somatic mutations

Abstract Background The gene tests to predict whether cancers respond to specific targeted therapies or prediction of prognosis has quickly increased over the last decade. Next-generation sequencing (NGS) has become a powerful tool for high-throughput and sensitive gene mutation testing, which is required for development of targeted therapies, clinical trials, and further research. The aim of this study was to validate the AmpliSeq for Illumina Cancer Hotspot Panel v2 on the Illumina MiSeq platform and simultaneously analyze 2800 somatic mutations across the hotspot regions of 50 genes, including SNP and small INDEL, with known associations to cancer, as identified in the Catalogue of Somatic Mutations in Cancer (COSMIC) database. This panel enables the study of the genes associated with different cancer types, including the cancers of the lung, colon, breast, thyroid, oral, bladder, prostate, liver, kidney, ovarian and cervix, etc. Methods and findings We validated this assay using the genomic DNA extracted from human paraffin-embedded (FFPE) samples and peripheral blood with negative control DNA (NA12878), positive control DNA (HD701), blank control as well as the global proficiency testing samples. Following two lab scientists parallel NGS library preparation, sequenced on Miseq platform (2x150 PE) and analyzed using a pipeline centered on Illumina Basespace, the somatic mutations were called at an average number of reads coverage &amp;gt;2500X, variant frequency cutoff 1%. An integrated test report can be generated within five working days. Panel sequencing analysis showed that the mutations are 100% concordance with known mutations and consistent in four runs, between lab personal performances, different input DNA concentrations (1ng-100ng), etc. Briefly, 25 mutations were detected in the FFPE samples and 20 mutations detected in proficiency testing samples. The variant types, HGVS ID and frequency are 100% match with its standard results which are a prove of precision and sensitivity. Conclusions A sensitive, high-throughput, pan-cancer mutation panel for NGS analysis of cancer hot-spot mutations in 50 genes was highly repeatable and reproducible and validated for routine application in a gene testing lab. Note: This abstract was not presented at the meeting. Citation Format: Wenzhi Li, Henry She, Xiaohua Tian, Margaret Neja, Adrian Harris, Yuhua Li. Validation of an NGS panel assay for detection of hotspot cancer somatic mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3007.

Optimized Nuclear Pellet Method for Extracting Next-Generation Sequencing Quality Genomic DNA from Fresh Leaf Tissue.

Next-generation sequencing (NGS) is a revolutionary advancement allowing large-scale discovery of functional molecular markers that has many applications, including plant breeding. High-quality genomic DNA (gDNA) is a prerequisite for successful NGS library preparation and sequencing; however, few reliable protocols to obtain such plant gDNA exist. A previously reported nuclear pellet (NP) method enables extraction of high-yielding gDNA from fresh leaf tissue of maize (Zea mays L.), but the quality does not meet the stringent requirements of NGS. In this study, we optimized the NP method for whole-genome sequencing of rice (Oryza sativa L.) through the integration of simple purification steps. The optimized NP method relied on initial nucleus enrichment, cell lysis, extraction, and subsequent gDNA purification buffers. The purification steps used proteinase K, RNase A, phenol/chloroform/isoamyl alcohol (25:24:1), and chloroform/isoamyl alcohol (24:1) treatments for protein digestion and RNA, protein, and phenol removal, respectively. Our data suggest that this optimized NP method allowed extraction of consistently high-yielding and high-quality undegraded gDNA without contamination by protein and RNA. Moreover, the extracted gDNA fulfilled the quality metrics of NGS library preparation for the Illumina HiSeq X Ten platform by the TruSeq DNA PCR-Free Library Prep Kit (Illumina). We provide a reliable step-by-step guide to the extraction of high-quality gDNA from fresh leaf tissues of rice for molecular biologists with limited resources.

A novel CRISPR/Cas9 associated technology for sequence-specific nucleic acid enrichment.

Massively parallel sequencing technologies have made it possible to generate large quantities of sequence data. However, as research-associated information is transferred into clinical practice, cost and throughput constraints generally require sequence-specific targeted analyses. Therefore, sample enrichment methods have been developed to meet the needs of clinical sequencing applications. However, current amplification and hybrid capture enrichment methods are limited in the contiguous length of sequences for which they are able to enrich. PCR based amplification also loses methylation data and other native DNA features. We have developed a novel technology (Negative Enrichment) where we demonstrate targeting long (>10 kb) genomic regions of interest. We use the specificity of CRISPR-Cas9 single guide RNA (Cas9/sgRNA) complexes to define 5′ and 3′ termini of sequence-specific loci in genomic DNA, targeting 10 to 36 kb regions. The complexes were found to provide protection from exonucleases, by protecting the targeted sequences from degradation, resulting in enriched, double-strand, non-amplified target sequences suitable for next-generation sequencing library preparation or other downstream analyses.

NGS-Based High-Throughput Screen to Identify MicroRNAs Regulating Growth of B-Cell Lymphoma.

MicroRNAs (miRNAs) play important roles in development, differentiation, and homeostasis by regulating protein translation. In B-cell lymphoma, many miRNAs have altered expression levels, and for a limited subset of them, experimental data supports their functional relevance in lymphoma pathogenesis. This chapter describes an unbiased next-generation sequencing (NGS)-based high-throughput screening approach to identify miRNAs that are involved in the control of cell growth. First, we provide a protocol for performing high-throughput screening for miRNA inhibition and overexpression. Second, we describe the procedure for next-generation sequencing library preparation. Third, we provide a workflow for data analysis.

SMARTcleaner: identify and clean off-target signals in SMART ChIP-seq analysis

BackgroundNoises and artifacts may arise in several steps of the next-generation sequencing (NGS) process. Recently, an NGS library preparation method called SMART, or Switching Mechanism At the 5′ end of the RNA Transcript, is introduced to prepare ChIP-seq (chromatin immunoprecipitation and deep sequencing) libraries from small amount of DNA material, using the DNA SMART ChIP-seq Kit. The protocol adds Ts to the 3′ end of DNA templates, which is subsequently recognized and used by SMART poly(dA) primers for reverse transcription and then addition of PCR primers and sequencing adapters. The poly(dA) primers, however, can anneal to poly(T) sequences in a genome and amplify DNA fragments that are not enriched in the immunoprecipitated DNA templates. This off-target amplification results in false signals in the ChIP-seq data.ResultsHere, we show that the off-target ChIP-seq reads derived from false amplification of poly(T/A) genomic sequences have unique and strand-specific features. Accordingly, we develop a tool (called “SMARTcleaner”) that can exploit these features to remove SMART ChIP-seq artifacts. Application of SMARTcleaner to several SMART ChIP-seq datasets demonstrates that it can remove reads from off-target amplification effectively, leading to significantly improved ChIP-seq peaks and results.ConclusionsSMARTcleaner could identify and clean the false signals in SMART-based ChIP-seq libraries, leading to improvement in peak calling, and downstream data analysis and interpretation.

An Improved NGS Library Construction Approach Using DNA Isolated from Human Cancer Formalin-Fixed Paraffin-Embedded Samples.

Identification of genomic alterations from formalin-fixed paraffin-embedded (FFPE) samples using next-generation sequencing (NGS) is very important for cancer-targeted therapy today. To achieve a higher efficiency and shorter turn-around time for NGS library preparation, here, we compared NGS library preparation processes and outcomes with three commercial library construction methods and two hybridization capture methods thus, developed an improved NGS library construction approach. This improved approach took advantage of both methods and resulted in a higher output from the same input DNA, including higher library construction success rate, higher probe capture rate, and shorter turn-around time. Using this approach, targeted region libraries could be constructed within only 1 day for FFPE samples; therefore, this approach has potential applications of NGS in routine clinical tests. Anat Rec, 302:941-946, 2019. © 2018 Wiley Periodicals, Inc.

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 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' and 3' 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.

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 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' and 3' 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.

Development of High-Throughput Clinical Testing ofRPGRORF15 Using a Large Inherited Retinal Dystrophy Cohort

Mutations in the ORF15 region of RPGR account for approximately half of all X-linked retinitis pigmentosa cases. However, a robust high-throughput method for the detection of ORF15 mutations has yet to be validated. We set out to develop the first clinically validated next-generation sequencing (NGS) method for the detection of mutations in this difficult-to-sequence region, including test accuracy and coverage data. As part of a blind-test, 145 research samples, previously tested by Sanger sequencing, and 81 clinical samples were evaluated using NGS of long-range PCR products fragmented with Illumina's Nextera library preparation kit (method 1), or with Centrillion's OneTube technology, supplemented with duplication analysis using an ORF15-specific in-silico array (method 2). DNA fragments were analyzed using Agilent's DNA 1000 assay, and sequencing was done on Illumina's MiSeq 2×150 or HiSeq2500 2×100. NextGENe by SoftGenetics was used for data analysis and variant calling. The Nextera library preparation method produced 24 cases of discordance due to (in order of decreasing occurrence) false-negatives, incorrectly called variants, and a false-positive. Subsequent use of a new, OneTube NGS library preparation method, supplemented with duplication analyses, resolved discordance between Sanger and NGS data in all cases. This improvement in variant detection accuracy was largely attributed to improvement in random fragmentation offered by the enzymatic OneTube method, resulting in more complete coverage of the highly repetitive ORF15 region. Minimum coverage was roughly 320 reads for Nextera and 6800 reads for OneTube (normalized for total read counts). This paper documents the first clinically validated NGS method for reliable, high-throughput sequencing of RPGR ORF15. Sensitivity and specificity of the new method were 100%, with the caveat of unclear zygosity calling for one large duplication case. These findings demonstrate a reliable and practical implementation for NGS-based diagnosis of RPGR ORF15 mutations. They also provide the foundation for targeted, high-coverage sequencing of any other repetitive regions within the genome.

Transcriptional analysis of viral mRNAs reveals common transcription patterns in cells infected by five different filoviruses.

Filoviruses are notorious viral pathogens responsible for high-consequence diseases in humans and non-human primates. Transcription of filovirus mRNA shares several common features with transcription in other non-segmented negative-strand viruses, including differential expression of genes located across the viral genome. Transcriptional patterns of Ebola virus (EBOV) and Marburg virus (MARV) have been previously described using traditional, laborious methods, such as northern blots and in vivo labeling of viral mRNAs. More recently, however, the availability of the next generation sequencing (NGS) technology has offered a more straightforward approach to assess transcriptional patterns. In this report, we analyzed the transcription patterns of four ebolaviruses—EBOV, Sudan (SUDV), Bundibugyo (BDBV), and Reston (RESTV) viruses—in two different cell lines using standard NGS library preparation and sequencing protocols. In agreement with previous reports mainly focused on EBOV and MARV, the remaining filoviruses used in this study also showed a consistent transcription pattern, with only minor variations between the different viruses. We have also analyzed the proportions of the three mRNAs transcribed from the GP gene, which are characteristic of the genus Ebolavirus and encode the glycoprotein (GP), the soluble GP (sGP), and the small soluble GP (ssGP). In addition, we used NGS methodology to analyze the transcription pattern of two previously described recombinant MARV. This analysis allowed us to correct our construction design, and to make an improved version of the original MARV expressing reporter genes.

PO-336 ThruPLEX® and PicoPLEX® technologies for rare alleles and copy number variation detection from cell-free DNA and single human cancer cells

IntroductionLiquid biopsies provide a non-invasive method to acquire the genetic information provided in cell-free DNA (cfDNA) as well as in single circulating tumour cells. Access to this genetic information through next-generation sequencing (NGS) identifies mutations and alterations such as Copy Number Variation (CNV) that play a role in cancer and other diseases.Material and methodsThe key to identifying rare mutations is improved sequencing accuracy and the ability to distinguish between biological and PCR duplicates. ThruPLEX Tag-seq was developed with the addition of unique molecular tags (UMTs) to improve sequencing accuracy by accounting for polymerase and sequencing errors and to increase confidence in rare allele identification. Whole Genome Amplification (WGA) for CNV detection was achieved by the thermal cycling quasi-random primed library chemistry of the PicoPLEX DNA-seq single-cell NGS library prep kit.Results and discussionsThruPLEX Tag-seq libraries were prepared using 10–30 ng of Horizon Discovery’s Multiplex I cfDNA Reference Standard Set containing six single nucleotide variants (SNV) for 4 different genes (EGFR, KRAS, NRAS, PIK3CA) present at 0.5%–5% allele frequency. The libraries were enriched with either a 110 kb or 240 kb custom panel or the Agilent ClearSeq Comprehensive Cancer Panel. Enriched libraries were sequenced witan average total read coverage of approximately 5,000X and analysed with and without the UMTs.For CNV analysis in single cells, a bar-coded PicoPLEX DNA-seq library was synthesised and amplified from 6 single cells from either PBMCs and clonally-expanded PC3 prostate cancer cells. Sequencing was performed on a MiSeq v2 and reads were mapped using BWA-MEM, processed in Picard_Mark_Duplicates, and further characterised in DNA nexus.classic. All PC3 cells showed reproducible CNV calling, however none of the lymphocyte samples showed any CNVs. Accurate CNV calls for PC3 cells were achieved even at when fastq files were randomly downsampled to 1 50 000 read pairs.ConclusionTherefore, use of UMTs in the preparation of NGS libraries from cfDNA enhances sequencing accuracy: by distinguishing between biological duplicates and PCR duplicates, increasing read coverage and decreasing background noise, reducing false positives, and in more confident mutation calls. PicoPLEX DNA-seq NGS libraries have a very simple and fast workflow that is suitable reproducible CNV detection in single cells even at low 0.002X average coverage.