Abstract 6018: Sequencing of 5-hydroxymethylcytosine to single base resolution

DNA methylation is an epigenetic regulator of gene expression with important functions in development and diseases such as cancer. The modified cytosines, 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) are identified using Illumina sequencing. Libraries are generated using either NEBNext® EM-seq™, an enzyme-based workflow, or by using sodium bisulfite conversion. These methods, however, cannot differentiate between 5mC and 5hmC. Distinguishing these modifications is important as there is increased interest in 5hmCs role in regulating gene expression. Methods currently exist to enable discrimination of 5mC and 5hmC, for example, oxBS-seq and TAB-seq. These methods still rely upon sodium bisulfite conversion and have reduced data quality due to fragmentation and loss of DNA. Here we describe an enzymatic method that enables specific detection of 5hmC. 5hmC is detected using two enzymatic steps. Firstly, 5hmCs are glucosylated, which protects them from subsequent deamination by APOBEC. In contrast, cytosines and 5mCs are deaminated resulting in their conversion to uracil and thymine, respectively. During Illumina sequencing deaminated cytosine and 5mC are read as thymine and the glucosylated 5hmC are read as cytosine. Subtractive analysis of 5hmC data from EM-seq data, which detects both 5mC and 5hmC, permits the identification of individual 5mC and 5hmC sites. 5hmC data were generated for inputs of 0.1 ng to 200 ng DNA isolated from E14 mouse embryonic stem cells and human brain. The 5hmC libraries had similar characteristics to EM-seq libraries, including expected insert sizes due to intact DNA molecules, low duplication rates and minimal GC bias. T4147 phage DNA was used as an internal control, as all cytosines are 5-hydroxymethylated, with 98-99% of cytosines identified as 5hmC. 5mC and 5hmC levels were also profiled during E14 cell differentiation for 10 days. Interestingly, 5hmC levels decreased whereas 5mC levels increased particularly during the first five days of differentiation. LC-MS/MS quantification of this same DNA mirrored the changes observed by sequencing. The ability to discriminate between 5mC and 5hmC will provide key insights into the role of these cytosine modifications in development and disease.

Citation Format: Daniel J. Evanich, V. K. Chaithanya Ponnaluri, Vaishnavi Panchapakesa, Ariel Erijman, Matthew A. Campbell, Nan Dai, Bradley W. Langhorst, Romualdas Vaisvila, Louise Williams. Sequencing of 5-hydroxymethylcytosine to single base resolution [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6018.

Abstract 249: A novel suite of enzyme mixes enable robust hybrid capture sequencing from low quality FFPE DNA

In cancer genomics, a common source of DNA is formalin-fixed, paraffin-embedded (FFPE) tissue from patient surgical samples, where in most cases high-quality fresh or frozen tissue samples are not available. FFPE DNA poses many notable challenges for preparing NGS libraries, including low input amounts and highly variable damage from fixation, storage, and extraction methods. Due to the high cost of sequencing and variability of coverage, regions of interest are often specifically enriched using hybrid capture-based approaches, but these methods require a high input of diverse, uniform DNA library to achieve the coverage required for somatic mutation identification in tumor samples. We developed a new DNA repair enzyme mix, enzymatic fragmentation mix, and library amplification PCR master mix, optimizing the activities of these mixes using FFPE samples ranging from DIN 1.8 to 6.8 to maximize yield, WGS library quality, and target enrichment library performance. Combining DNA damage repair and a novel enzymatic fragmentation mix upstream of library preparation reduced the false positive rate in somatic variant detection by repairing damage-derived mutations, and also improved the library yield, quality metrics (including mapping, chimeras, and properly-paired reads), complexity, coverage uniformity, and hybrid capture library quality metrics. The new PCR master mix boosts the library yield without compromising library quality in FFPE-derived samples, allowing flexibility in the PCR cycles used to accommodate high-throughput processing of FFPE samples of highly varied quality. This library prep workflow was evaluated with multiple sequencing platforms including Illumina, MGI, and Element Biosciences. This new suite of enzyme mixes allows even highly damaged FFPE samples to achieve high-quality libraries with sufficient input for hybrid capture. Increasing the useable reads and coverage enables robust detection of somatic variants as demonstrated using both reference standard DNA and patient-derived FFPE samples. Finally, the use of enzymatic fragmentation and a flexible PCR master mix make this FFPE library prep workflow compatible with high-throughput and automation-based workflows.

Citation Format: Margaret R. Heider, Jian Sun, Brittany S. Sexton, Bradley W. Langhorst, Andrew Gray, Lauren Higgins, Lixin Chen, Lynne Apone, Thomas C. Evans, Nicole M. Nichols, Pingfang Liu. A novel suite of enzyme mixes enable robust hybrid capture sequencing from low quality FFPE DNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 249.

Overcoming variant mutation-related impacts on viral sequencing and detection methodologies

Prompt and accurate pathogen identification, by diagnostics and sequencing, is an effective tool for tracking and potentially curbing pathogen spread. Targeted detection and amplification of viral genomes depends on annealing complementary oligonucleotides to genomic DNA or cDNA. However, genomic mutations that occur during viral evolution may perturb annealing, which can result in incomplete sequence coverage of the genome and/or false negative diagnostic test results. Herein, we demonstrate how to assess, test, and optimize sequencing and detection methodologies to attenuate the negative impact of mutations on genome targeting efficiency. This evaluation was conducted using in vitro-transcribed (IVT) RNA as well as RNA extracted from clinical SARS-CoV-2 variant samples, including the heavily mutated Omicron variant. Using SARS-CoV-2 as a current example, these results demonstrate how to maintain reliable targeted pathogen sequencing and how to evaluate detection methodologies as new variants emerge.

The Galaxy platform for accessible, reproducible and collaborative biomedical analyses: 2022 update

Galaxy is a mature, browser accessible workbench for scientific computing. It enables scientists to share, analyze and visualize their own data, with minimal technical impediments. A thriving global community continues to use, maintain and contribute to the project, with support from multiple national infrastructure providers that enable freely accessible analysis and training services. The Galaxy Training Network supports free, self-directed, virtual training with >230 integrated tutorials. Project engagement metrics have continued to grow over the last 2 years, including source code contributions, publications, software packages wrapped as tools, registered users and their daily analysis jobs, and new independent specialized servers. Key Galaxy technical developments include an improved user interface for launching large-scale analyses with many files, interactive tools for exploratory data analysis, and a complete suite of machine learning tools. Important scientific developments enabled by Galaxy include Vertebrate Genome Project (VGP) assembly workflows and global SARS-CoV-2 collaborations.

Abstract 5628: Immune repertoire sequencing facilitates gamma delta T cell clonal determination

Gamma-delta T cells are a small fraction of T lymphocytes with only 1-5% of the overall T cell population, but they are an important subset that have unique contributions to both innate and adaptive immunity. Gamma-delta T cells can recognize a broad range of antigens to provide rapid responses to pathogens, and can also interact with both immune cells and non-immune tissue cells triggering regulatory and cytotoxic responses. These unique features make them ideal candidates that could be targeted to induce durable immunity in the context of different pathologies. There has been growing interest in understanding the contributions of gamma-delta T cells to immunology and developing efficient gamma-delta T-cell-based therapies for cancer, infectious disease, and autoimmune disease. In this study, we have implemented T cell repertoire sequencing for high throughput characterization. Gamma-delta T cells were enriched from tissues and peripheral blood mononuclear cells (PBMCs). RNA was extracted and used to generate full length TCR libraries. Unique molecular identifiers (UMIs) were incorporated to discretely barcode each mRNA molecule, enabling absolute quantitative ranking of TCR clone abundance. Full length immune repertoire sequencing facilitates the detection of distinct and shared clones in tissue and blood samples, enabling the identification of disease specific clones to evaluate immunotherapy effects. In addition, RNA sequencing was performed for gene expression analysis of gamma-delta T cells to identify cell phenotypes.

Citation Format: Chen Song, Ariel Erijman, Bradley W. Langhorst, Pingfang Liu, Eileen T. Dimalanta, Theodore B. Davis. Immune repertoire sequencing facilitates gamma delta T cell clonal determination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5628.

Development and implementation of a simple and rapid extraction-free saliva SARS-CoV-2 RT-LAMP workflow for workplace surveillance

Effective management of the COVID-19 pandemic requires widespread and frequent testing of the population for SARS-CoV-2 infection. Saliva has emerged as an attractive alternative to nasopharyngeal samples for surveillance testing as it does not require specialized personnel or materials for its collection and can be easily provided by the patient. We have developed a simple, fast, and sensitive saliva-based testing workflow that requires minimal sample treatment and equipment. After sample inactivation, RNA is quickly released and stabilized in an optimized buffer, followed by reverse transcription loop-mediated isothermal amplification (RT-LAMP) and detection of positive samples using a colorimetric and/or fluorescent readout. The workflow was optimized using 1,670 negative samples collected from 172 different individuals over the course of 6 months. Each sample was spiked with 50 copies/μL of inactivated SARS-CoV-2 virus to monitor the efficiency of viral detection. Using pre-defined clinical samples, the test was determined to be 100% specific and 97% sensitive, with a limit of detection of 39 copies/mL. The method was successfully implemented in a CLIA laboratory setting for workplace surveillance and reporting. From April 2021-February 2022, more than 30,000 self-collected samples from 755 individuals were tested and 85 employees tested positive mainly during December and January, consistent with high infection rates in Massachusetts and nationwide.

Expanding the Galaxy's reference data

Summary

Properly and effectively managing reference datasets is an important task for many bioinformatics analyses. Refgenie is a reference asset management system that allows users to easily organize, retrieve and share such datasets. Here, we describe the integration of refgenie into the Galaxy platform. Server administrators are able to configure Galaxy to make use of reference datasets made available on a refgenie instance. In addition, a Galaxy Data Manager tool has been developed to provide a graphical interface to refgenie's remote reference retrieval functionality. A large collection of reference datasets has also been made available using the CVMFS (CernVM File System) repository from GalaxyProject.org, with mirrors across the USA, Canada, Europe and Australia, enabling easy use outside of Galaxy.

Availability and implementation

The ability of Galaxy to use refgenie assets was added to the core Galaxy framework in version 22.01, which is available from https://github.com/galaxyproject/galaxy under the Academic Free License version 3.0. The refgenie Data Manager tool can be installed via the Galaxy ToolShed, with source code managed at https://github.com/BlankenbergLab/galaxy-tools-blankenberg/tree/main/data_managers/data_manager_refgenie_pull and released using an MIT license. Access to existing data is also available through CVMFS, with instructions at https://galaxyproject.org/admin/reference-data-repo/. No new data were generated or analyzed in support of this research.

The SEQC2 epigenomics quality control (EpiQC) study

BACKGROUND

Cytosine modifications in DNA such as 5-methylcytosine (5mC) underlie a broad range of developmental processes, maintain cellular lineage specification, and can define or stratify types of cancer and other diseases. However, the wide variety of approaches available to interrogate these modifications has created a need for harmonized materials, methods, and rigorous benchmarking to improve genome-wide methylome sequencing applications in clinical and basic research. Here, we present a multi-platform assessment and cross-validated resource for epigenetics research from the FDA's Epigenomics Quality Control Group.

RESULTS

Each sample is processed in multiple replicates by three whole-genome bisulfite sequencing (WGBS) protocols (TruSeq DNA methylation, Accel-NGS MethylSeq, and SPLAT), oxidative bisulfite sequencing (TrueMethyl), enzymatic deamination method (EMSeq), targeted methylation sequencing (Illumina Methyl Capture EPIC), single-molecule long-read nanopore sequencing from Oxford Nanopore Technologies, and 850k Illumina methylation arrays. After rigorous quality assessment and comparison to Illumina EPIC methylation microarrays and testing on a range of algorithms (Bismark, BitmapperBS, bwa-meth, and BitMapperBS), we find overall high concordance between assays, but also differences in efficiency of read mapping, CpG capture, coverage, and platform performance, and variable performance across 26 microarray normalization algorithms.

CONCLUSIONS

The data provided herein can guide the use of these DNA reference materials in epigenomics research, as well as provide best practices for experimental design in future studies. By leveraging seven human cell lines that are designated as publicly available reference materials, these data can be used as a baseline to advance epigenomics research.

Loop-Mediated Isothermal Amplification Detection of SARS-CoV-2 and Myriad Other Applications

As the second year of the COVID-19 pandemic begins, it remains clear that a massive increase in the ability to test for SARS-CoV-2 infections in a myriad of settings is critical to controlling the pandemic and to preparing for future outbreaks. The current gold standard for molecular diagnostics is the polymerase chain reaction (PCR), but the extraordinary and unmet demand for testing in a variety of environments means that both complementary and supplementary testing solutions are still needed. This review highlights the role that loop-mediated isothermal amplification (LAMP) has had in filling this global testing need, providing a faster and easier means of testing, and what it can do for future applications, pathogens, and the preparation for future outbreaks. This review describes the current state of the art for research of LAMP-based SARS-CoV-2 testing, as well as its implications for other pathogens and testing. The authors represent the global LAMP (gLAMP) Consortium, an international research collective, which has regularly met to share their experiences on LAMP deployment and best practices; sections are devoted to all aspects of LAMP testing, including preanalytic sample processing, target amplification, and amplicon detection, then the hardware and software required for deployment are discussed, and finally, a summary of the current regulatory landscape is provided. Included as well are a series of first-person accounts of LAMP method development and deployment. The final discussion section provides the reader with a distillation of the most validated testing methods and their paths to implementation. This review also aims to provide practical information and insight for a range of audiences: for a research audience, to help accelerate research through sharing of best practices; for an implementation audience, to help get testing up and running quickly; and for a public health, clinical, and policy audience, to help convey the breadth of the effect that LAMP methods have to offer.

Enzymatic methyl sequencing detects DNA methylation at single-base resolution from picograms of DNA

Bisulfite sequencing detects 5mC and 5hmC at single-base resolution. However, bisulfite treatment damages DNA, which results in fragmentation, DNA loss, and biased sequencing data. To overcome these problems, enzymatic methyl-seq (EM-seq) was developed. This method detects 5mC and 5hmC using two sets of enzymatic reactions. In the first reaction, TET2 and T4-BGT convert 5mC and 5hmC into products that cannot be deaminated by APOBEC3A. In the second reaction, APOBEC3A deaminates unmodified cytosines by converting them to uracils. Therefore, these three enzymes enable the identification of 5mC and 5hmC. EM-seq libraries were compared with bisulfite-converted DNA, and each library type was ligated to Illumina adaptors before conversion. Libraries were made using NA12878 genomic DNA, cell-free DNA, and FFPE DNA over a range of DNA inputs. The 5mC and 5hmC detected in EM-seq libraries were similar to those of bisulfite libraries. However, libraries made using EM-seq outperformed bisulfite-converted libraries in all specific measures examined (coverage, duplication, sensitivity, etc.). EM-seq libraries displayed even GC distribution, better correlations across DNA inputs, increased numbers of CpGs within genomic features, and accuracy of cytosine methylation calls. EM-seq was effective using as little as 100 pg of DNA, and these libraries maintained the described advantages over bisulfite sequencing. EM-seq library construction, using challenging samples and lower DNA inputs, opens new avenues for research and clinical applications.

Shotgun transcriptome, spatial omics, and isothermal profiling of SARS-CoV-2 infection reveals unique host responses, viral diversification, and drug interactions

In less than nine months, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) killed over a million people, including >25,000 in New York City (NYC) alone. The COVID-19 pandemic caused by SARS-CoV-2 highlights clinical needs to detect infection, track strain evolution, and identify biomarkers of disease course. To address these challenges, we designed a fast (30-minute) colorimetric test (LAMP) for SARS-CoV-2 infection from naso/oropharyngeal swabs and a large-scale shotgun metatranscriptomics platform (total-RNA-seq) for host, viral, and microbial profiling. We applied these methods to clinical specimens gathered from 669 patients in New York City during the first two months of the outbreak, yielding a broad molecular portrait of the emerging COVID-19 disease. We find significant enrichment of a NYC-distinctive clade of the virus (20C), as well as host responses in interferon, ACE, hematological, and olfaction pathways. In addition, we use 50,821 patient records to find that renin-angiotensin-aldosterone system inhibitors have a protective effect for severe COVID-19 outcomes, unlike similar drugs. Finally, spatial transcriptomic data from COVID-19 patient autopsy tissues reveal distinct ACE2 expression loci, with macrophage and neutrophil infiltration in the lungs. These findings can inform public health and may help develop and drive SARS-CoV-2 diagnostic, prevention, and treatment strategies.

Shotgun Transcriptome and Isothermal Profiling of SARS-CoV-2 Infection Reveals Unique Host Responses, Viral Diversification, and Drug Interactions

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has caused thousands of deaths worldwide, including >18,000 in New York City (NYC) alone. The sudden emergence of this pandemic has highlighted a pressing clinical need for rapid, scalable diagnostics that can detect infection, interrogate strain evolution, and identify novel patient biomarkers. To address these challenges, we designed a fast (30-minute) colorimetric test (LAMP) for SARS-CoV-2 infection from naso/oropharyngeal swabs, plus a large-scale shotgun metatranscriptomics platform (total-RNA-seq) for host, bacterial, and viral profiling. We applied both technologies across 857 SARS-CoV-2 clinical specimens and 86 NYC subway samples, providing a broad molecular portrait of the COVID-19 NYC outbreak. Our results define new features of SARS-CoV-2 evolution, nominate a novel, NYC-enriched viral subclade, reveal specific host responses in interferon, ACE, hematological, and olfaction pathways, and examine risks associated with use of ACE inhibitors and angiotensin receptor blockers. Together, these findings have immediate applications to SARS-CoV-2 diagnostics, public health, and new therapeutic targets.

A single-molecule sequencing assay for the comprehensive profiling of T4 DNA ligase fidelity and bias during DNA end-joining

DNA ligases are key enzymes in molecular and synthetic biology that catalyze the joining of breaks in duplex DNA and the end-joining of DNA fragments. Ligation fidelity (discrimination against the ligation of substrates containing mismatched base pairs) and bias (preferential ligation of particular sequences over others) have been well-studied in the context of nick ligation. However, almost no data exist for fidelity and bias in end-joining ligation contexts. In this study, we applied Pacific Biosciences Single-Molecule Real-Time sequencing technology to directly sequence the products of a highly multiplexed ligation reaction. This method has been used to profile the ligation of all three-base 5′-overhangs by T4 DNA ligase under typical ligation conditions in a single experiment. We report the relative frequency of all ligation products with or without mismatches, the position-dependent frequency of each mismatch, and the surprising observation that 5′-TNA overhangs ligate extremely inefficiently compared to all other Watson–Crick pairings. The method can easily be extended to profile other ligases, end-types (e.g. blunt ends and overhangs of different lengths), and the effect of adjacent sequence on the ligation results. Further, the method has the potential to provide new insights into the thermodynamics of annealing and the kinetics of end-joining reactions.

Abstract 3526: Incorporation of unique molecular identifiers (UMIs) into unique dual sample indexing (UDI) improves the accuracy of quantitative next generation sequencing

Accurate analysis of quantitative NGS data is critical for low frequency variant detection, identification of differentially expressed transcripts, and correct diagnosis and patient care in a clinical NGS setting. Two major factors affecting sequencing accuracy are 1) PCR duplication arising from amplification of library molecules; and 2) errors introduced during library preparation and actual sequencing on the flow cell. Standard practice for identification and removal of PCR duplicates relies on aligning reads to the same genomic coordinates. However, this approach can not differentiate between PCR duplicates and reads originating from unique molecules with identical ends. The most effective method for error correction is Duplex Sequencing, which utilizes UMIs to tag both strands of each individual DNA duplex followed by building consensus sequences. Unfortunately, this approach is labor intensive and cost-prohibitive for complex genomes and large target panels. Therefore, a simple and reliable approach for duplicate removal and error correction would greatly facilitate the wider adoption of NGS technology for diagnostics and clinical applications.

In this study, we incorporate UMIs into UDI systems and assess the effect on the accuracy of quantitative sequencing assays. We first study the effectiveness of various computational methods to account for UMIs and remove base-calling errors introduced during sequencing. We then analyze the utility of UMIs for 1) unique and low abundance transcript identification and accurate transcript quantification; and 2) error correction in low frequency variant detection in genomic sequencing from both high quality cell line DNA and low quality FFPE DNA. In addition, we demonstrate that combining unique dual sample indexing with UMI molecular barcoding further improves data analysis accuracy, especially on patterned flow cells. Our approach involves a simple new UMI-containing UDI adaptor design that can also be applied to other sequencing methods and platforms.

Citation Format: Pingfang Liu, Keerthana Krishnan, Camille X. Devoe, Bradley W. Langhorst, Eileen Dimalanta, Theodore B. Davis. Incorporation of unique molecular identifiers (UMIs) into unique dual sample indexing (UDI) improves the accuracy of quantitative next generation sequencing [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 3526.

Abstract 4046: Immune repertoire sequencing reveals tumor microenvironment and tracks clonally expanded B cell and T cell in blood

The study of complex immunological diseases and tumor microenvironments has progressed through recent developments on sequencing of the immune repertoire. Using this approach, the interrogation of disease progression is facilitated through analysis of millions of V(D)J combinations from B cell antibodies (Igs) and T cell receptors (TCRs). One major challenge of immune repertoire sequencing is to accurately capture the structural and sequence complexities of antibodies and TCR genes. We have developed a method for accurate sequencing of full length immune gene repertoires of B cells and T cells. RNA extracted from tumor tissues containing tumor infiltrating lymphocytes, as well as matched peripheral blood mononuclear cells (PBMCs) were used to generate full length Ig and TCR libraries. Unique molecule index (UMI) was used to discretely barcode each mRNA molecule, enabling absolute quantitative ranking of antibody/TCR clone abundance. Full length immune repertoire sequencing facilitates detection of distinct and shared clones in tissue and blood samples, enabling identification of disease specific clones to evaluate immunotherapy effects. Highly expanded clones in tumor samples are also found in blood samples. RNA-seq libraries were also constructed from the same RNA for Ig and TCR libraries. The expression level of IGH/IGL/IGK and TRA/TRB in the immune sequencing libraries highly correlates with the RNA-seq data. In addition, both Ig and TCR libraries can be constructed in one tube to obtain a whole immune repertoire profile.Our immune repertoire sequencing approach allows accurate clonal determination for both Ig and TCR. This technique is applicable for investigation of lymphocytes infiltration of tumor microenvironments, tracing expanded B cell and T cells in blood samples, and monitoring of minimal residual disease.

Citation Format: Chen Song, Pingfang Liu, Andrew Barry, Bradley W. Langhorst, Fiona J. Stewart, Salvatore Russello, Theodore B. Davis, Eileen T. Dimalanta. Immune repertoire sequencing reveals tumor microenvironment and tracks clonally expanded B cell and T cell in blood [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 4046.

Comprehensive Profiling of Four Base Overhang Ligation Fidelity by T4 DNA Ligase and Application to DNA Assembly

Synthetic biology relies on the manufacture of large and complex DNA constructs from libraries of genetic parts. Golden Gate and other Type IIS restriction enzyme-dependent DNA assembly methods enable rapid construction of genes and operons through one-pot, multifragment assembly, with the ordering of parts determined by the ligation of Watson-Crick base-paired overhangs. However, ligation of mismatched overhangs leads to erroneous assembly, and low-efficiency Watson Crick pairings can lead to truncated assemblies. Using sets of empirically vetted, high-accuracy junction pairs avoids this issue but limits the number of parts that can be joined in a single reaction. Here, we report the use of comprehensive end-joining ligation fidelity and bias data to predict high accuracy junction sets for Golden Gate assembly. The ligation profile accurately predicted junction fidelity in ten-fragment Golden Gate assembly reactions and enabled accurate and efficient assembly of a lac cassette from up to 24-fragments in a single reaction.

Solid-phase enzyme catalysis of DNA end repair and 3' A-tailing reduces GC-bias in next-generation sequencing of human genomic DNA

The use of next-generation sequencing (NGS) has been instrumental in advancing biological research and clinical diagnostics. To fully utilize the power of NGS, complete, uniform coverage of the entire genome is required. In this study, we identified the primary sources of bias observed in sequence coverage across AT-rich regions of the human genome with existing amplification-free DNA library preparation methods. We have found evidence that a major source of bias is the inefficient processing of AT-rich DNA in end repair and 3' A-tailing, causing under-representation of extremely AT-rich regions. We have employed immobilized DNA modifying enzymes to catalyze end repair and 3' A-tailing reactions, to notably reduce the GC bias observed with existing library construction methods.

PacBio-Based Mitochondrial Genome Assembly of Leucaena trichandra (Leguminosae) and an Intrageneric Assessment of Mitochondrial RNA Editing

Reconstructions of vascular plant mitochondrial genomes (mt-genomes) are notoriously complicated by rampant recombination that has resulted in comparatively few plant mt-genomes being available. The dearth of plant mitochondrial resources has limited our understanding of mt-genome structural diversity, complex patterns of RNA editing, and the origins of novel mt-genome elements. Here, we use an efficient long read (PacBio) iterative assembly pipeline to generate mt-genome assemblies for Leucaena trichandra (Leguminosae: Caesalpinioideae: mimosoid clade), providing the first assessment of non-papilionoid legume mt-genome content and structure to date. The efficiency of the assembly approach facilitated the exploration of alternative structures that are common place among plant mitochondrial genomes. A compact version (729 kbp) of the recovered assemblies was used to investigate sources of mt-genome size variation among legumes and mt-genome sequence similarity to the legume associated root holoparasite Lophophytum. The genome and an associated suite of transcriptome data from select species of Leucaena permitted an in-depth exploration of RNA editing in a diverse clade of closely related species that includes hybrid lineages. RNA editing in the allotetraploid, Leucaena leucocephala, is consistent with co-option of nearly equal maternal and paternal C-to-U edit components, generating novel combinations of RNA edited sites. A preliminary investigation of L. leucocephala C-to-U edit frequencies identified the potential for a hybrid to generate unique pools of alleles from parental variation through edit frequencies shared with one parental lineage, those intermediate between parents, and transgressive patterns.

A Microbiome DNA Enrichment Method for Next-Generation Sequencing Sample Preparation

"Microbiome" is used to describe the communities of microorganisms and their genes in a particular environment, including communities in association with a eukaryotic host or part of a host. One challenge in microbiome analysis concerns the presence of host DNA in samples. Removal of host DNA before sequencing results in greater sequence depth of the intended microbiome target population. This unit describes a novel method of microbial DNA enrichment in which methylated host DNA such as human genomic DNA is selectively bound and separated from microbial DNA before next-generation sequencing (NGS) library construction. This microbiome enrichment technique yields a higher fraction of microbial sequencing reads and improved read quality resulting in a reduced cost of downstream data generation and analysis. © 2016 by John Wiley & Sons, Inc.

Selective Depletion of Abundant RNAs to Enable Transcriptome Analysis of Low-Input and Highly Degraded Human RNA

Ribosomal RNAs (rRNAs) are extremely abundant, often constituting 80% to 90% of total RNA. Since rRNA sequences are often not of interest in genomic RNA sequencing experiments, rRNAs can be removed from the sample before the library preparation step, in order to prevent the majority of the library and the majority of sequencing reads from being rRNA. Removal of rRNA can be especially challenging for low quality and formalin-fixed paraffin-embedded (FFPE) RNA samples due to the fragmented nature of these RNA molecules. The NEBNext rRNA Depletion Kit (Human/Mouse/Rat) depletes both cytoplasmic (5 S rRNA, 5.8 S rRNA, 18 S rRNA, and 28 S rRNA) and mitochondrial rRNA (12 S rRNA and 16 S rRNA) from total RNA preparations from human, mouse, and rat samples. Due to the high similarity among mammalian rRNA sequences, it is likely that rRNA depletion can also be achieved for other mammals but has not been empirically tested. This product is compatible with both intact and degraded RNA (e.g., FFPE RNA). The resulting rRNA-depleted RNA is suitable for RNA-seq, random-primed cDNA synthesis, or other downstream RNA analysis applications. Regardless of the quality or amount of input RNA, this method efficiently removes rRNA, while retaining non-coding and other non-poly(A) RNAs. The NEBNext rRNA Depletion Kit thus provides a more complete picture of the transcript repertoire than oligo d(T) poly(A) mRNA enrichment methods. © 2016 by John Wiley & Sons, Inc.

A method for selectively enriching microbial DNA from contaminating vertebrate host DNA

DNA samples derived from vertebrate skin, bodily cavities and body fluids contain both host and microbial DNA; the latter often present as a minor component. Consequently, DNA sequencing of a microbiome sample frequently yields reads originating from the microbe(s) of interest, but with a vast excess of host genome-derived reads. In this study, we used a methyl-CpG binding domain (MBD) to separate methylated host DNA from microbial DNA based on differences in CpG methylation density. MBD fused to the Fc region of a human antibody (MBD-Fc) binds strongly to protein A paramagnetic beads, forming an effective one-step enrichment complex that was used to remove human or fish host DNA from bacterial and protistan DNA for subsequent sequencing and analysis. We report enrichment of DNA samples from human saliva, human blood, a mock malaria-infected blood sample and a black molly fish. When reads were mapped to reference genomes, sequence reads aligning to host genomes decreased 50-fold, while bacterial and Plasmodium DNA sequences reads increased 8-11.5-fold. The Shannon-Wiener diversity index was calculated for 149 bacterial species in saliva before and after enrichment. Unenriched saliva had an index of 4.72, while the enriched sample had an index of 4.80. The similarity of these indices demonstrates that bacterial species diversity and relative phylotype abundance remain conserved in enriched samples. Enrichment using the MBD-Fc method holds promise for targeted microbiome sequence analysis across a broad range of sample types.

Database of DNA polymerases

The DNA Polymerase Database (Polbase) is intended to compile the wealth of existing DNA polymerase information from public and private records into an open, searchable database.

Polbase: a repository of biochemical, genetic and structural information about DNA polymerases

Polbase (http://polbase.neb.com) is a freely accessible database of DNA polymerases and related references. It has been developed in a collaborative model with experts whose contributions reflect their varied backgrounds in genetics, structural biology and biochemistry. Polbase is designed to compile detailed results of polymerase experimentation, presenting them in a dynamic view to inform further research. After validation, results from references are displayed in context with relevant experimental details and are always traceable to their source publication. Polbase is connected to other resources, including PubMed, UniProt and the RCSB Protein Data Bank, to provide multi-faceted views of polymerase knowledge. In addition to a simple web interface, Polbase data is exposed for custom analysis by external software. With the contributions of many polymerase investigators, Polbase has become a powerful research tool covering most important aspects of polymerases, from sequence and structure to biochemistry.

The Open AUC Project

Progress in analytical ultracentrifugation (AUC) has been hindered by obstructions to hardware innovation and by software incompatibility. In this paper, we announce and outline the Open AUC Project. The goals of the Open AUC Project are to stimulate AUC innovation by improving instrumentation, detectors, acquisition and analysis software, and collaborative tools. These improvements are needed for the next generation of AUC-based research. The Open AUC Project combines on-going work from several different groups. A new base instrument is described, one that is designed from the ground up to be an analytical ultracentrifuge. This machine offers an open architecture, hardware standards, and application programming interfaces for detector developers. All software will use the GNU Public License to assure that intellectual property is available in open source format. The Open AUC strategy facilitates collaborations, encourages sharing, and eliminates the chronic impediments that have plagued AUC innovation for the last 20 years. This ultracentrifuge will be equipped with multiple and interchangeable optical tracks so that state-of-the-art electronics and improved detectors will be available for a variety of optical systems. The instrument will be complemented by a new rotor, enhanced data acquisition and analysis software, as well as collaboration software. Described here are the instrument, the modular software components, and a standardized database that will encourage and ease integration of data analysis and interpretation software.