Somatic variant analysis of linked-reads sequencing data with Lancet

10.1101/2020.07.04.158063 ◽

2020 ◽

Author(s):

Rajeeva Musunuri ◽

Kanika Arora ◽

André Corvelo ◽

Minita Shah ◽

Jennifer Shelton ◽

...

Keyword(s):

Open Source ◽

De Bruijn Graph ◽

Haplotype Structure ◽

Sequencing Data ◽

Somatic Variant ◽

Local Assembly ◽

De Bruijn ◽

Variant Analysis ◽

Colored De Bruijn Graph ◽

Commercial Research

AbstractSummaryWe present a new version of the popular somatic variant caller, Lancet, that supports the analysis of linked-reads sequencing data. By seamlessly integrating barcodes and haplotype read assignments within the colored De Bruijn graph local-assembly framework, Lancet computes a barcode-aware coverage and identifies variants that disagree with the local haplotype structure.Availability and ImplementationLancet is implemented in C++ and is available for academic and non-commercial research purposes as an open-source package at https://github.com/nygenome/[email protected]

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Inference of viral quasispecies with a paired de Bruijn graph

Bioinformatics ◽

10.1093/bioinformatics/btaa782 ◽

2020 ◽

Author(s):

Borja Freire ◽

Susana Ladra ◽

Jose R Paramá ◽

Leena Salmela

Keyword(s):

High Throughput Sequencing ◽

De Novo ◽

Supplementary Information ◽

De Bruijn Graph ◽

Viral Quasispecies ◽

Sequencing Data ◽

De Bruijn Graphs ◽

Sequencing Errors ◽

High Throughput Sequencing Data ◽

De Bruijn

Abstract Motivation RNA viruses exhibit a high mutation rate and thus they exist in infected cells as a population of closely related strains called viral quasispecies. The viral quasispecies assembly problem asks to characterize the quasispecies present in a sample from high-throughput sequencing data. We study the de novo version of the problem, where reference sequences of the quasispecies are not available. Current methods for assembling viral quasispecies are either based on overlap graphs or on de Bruijn graphs. Overlap graph-based methods tend to be accurate but slow, whereas de Bruijn graph-based methods are fast but less accurate. Results We present viaDBG, which is a fast and accurate de Bruijn graph-based tool for de novo assembly of viral quasispecies. We first iteratively correct sequencing errors in the reads, which allows us to use large k-mers in the de Bruijn graph. To incorporate the paired-end information in the graph, we also adapt the paired de Bruijn graph for viral quasispecies assembly. These features enable the use of long-range information in contig construction without compromising the speed of de Bruijn graph-based approaches. Our experimental results show that viaDBG is both accurate and fast, whereas previous methods are either fast or accurate but not both. In particular, viaDBG has comparable or better accuracy than SAVAGE, while being at least nine times faster. Furthermore, the speed of viaDBG is comparable to PEHaplo but viaDBG is able to retrieve also low abundance quasispecies, which are often missed by PEHaplo. Availability and implementation viaDBG is implemented in C++ and it is publicly available at https://bitbucket.org/bfreirec1/viadbg. All datasets used in this article are publicly available at https://bitbucket.org/bfreirec1/data-viadbg/. Supplementary information Supplementary data are available at Bioinformatics online.

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An Incrementally Updatable and Scalable System for Large-Scale Sequence Search using LSM Trees

10.1101/2021.02.05.429839 ◽

2021 ◽

Author(s):

Fatemeh Almodaresi ◽

Jamshed Khan ◽

Sergey Madaminov ◽

Prashant Pandey ◽

Michael Ferdman ◽

...

Keyword(s):

Large Scale ◽

Supplementary Information ◽

De Bruijn Graph ◽

Sequencing Data ◽

Construction Time ◽

Graph Representations ◽

Sequence Search ◽

General Search ◽

Colored De Bruijn Graph ◽

Search Index

AbstractMotivationIn the past few years, researchers have proposed numerous indexing schemes for searching large databases of raw sequencing experiments. Most of these proposed indexes are approximate (i.e. with one-sided errors) in order to save space. Recently, researchers have published exact indexes—Mantis, VariMerge, and Bifrost—that can serve as colored de Bruijn graph representations in addition to serving as k-mer indexes. This new type of index is promising because it has the potential to support more complex analyses than simple searches. However, in order to be useful as indexes for large and growing repositories of raw sequencing data, they must scale to thousands of experiments and support efficient insertion of new data.ResultsIn this paper, we show how to build a scalable and updatable exact sequence-search index. Specifically, we extend Mantis using the Bentley-Saxe transformation to support efficient updates. We demonstrate Mantis’s scalability by constructing an index of ≈ 40K samples from SRA by adding samples one at a time to an initial index of 10K samples.Compared to VariMerge and Bifrost, Mantis is more efficient in terms of index-construction time and memory, query time and memory, and index size. In our benchmarks, VariMerge and Bifrost scaled to only 5K and 80 samples, respectively, while Mantis scaled to more than 39K samples. Queries were over 24× faster in Mantis than in Bifrost (VariMerge does not immediately support general search queries we require). Mantis indexes were about 2.5× smaller than Bifrost’s indexes and about half as big as VariMerge’s indexes.AvailabilityThe updatable Mantis implementation is available at https://github.com/splatlab/mantis/tree/[email protected] informationSupplementary data are available online.

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Metagenome SNP calling via read-colored de Bruijn graphs

Bioinformatics ◽

10.1093/bioinformatics/btaa081 ◽

2020 ◽

Cited By ~ 1

Author(s):

Bahar Alipanahi ◽

Martin D Muggli ◽

Musa Jundi ◽

Noelle R Noyes ◽

Christina Boucher

Keyword(s):

Pathogenic Bacteria ◽

Read Length ◽

Supplementary Information ◽

De Bruijn Graph ◽

Nucleotide Polymorphisms ◽

Chromosomal Dna ◽

Shotgun Metagenomics ◽

De Bruijn Graphs ◽

De Bruijn ◽

Colored De Bruijn Graph

Abstract Motivation Metagenomics refers to the study of complex samples containing of genetic contents of multiple individual organisms and, thus, has been used to elucidate the microbiome and resistome of a complex sample. The microbiome refers to all microbial organisms in a sample, and the resistome refers to all of the antimicrobial resistance (AMR) genes in pathogenic and non-pathogenic bacteria. Single-nucleotide polymorphisms (SNPs) can be effectively used to ‘fingerprint’ specific organisms and genes within the microbiome and resistome and trace their movement across various samples. However, to effectively use these SNPs for this traceability, a scalable and accurate metagenomics SNP caller is needed. Moreover, such an SNP caller should not be reliant on reference genomes since 95% of microbial species is unculturable, making the determination of a reference genome extremely challenging. In this article, we address this need. Results We present LueVari, a reference-free SNP caller based on the read-colored de Bruijn graph, an extension of the traditional de Bruijn graph that allows repeated regions longer than the k-mer length and shorter than the read length to be identified unambiguously. LueVari is able to identify SNPs in both AMR genes and chromosomal DNA from shotgun metagenomics data with reliable sensitivity (between 91% and 99%) and precision (between 71% and 99%) as the performance of competing methods varies widely. Furthermore, we show that LueVari constructs sequences containing the variation, which span up to 97.8% of genes in datasets, which can be helpful in detecting distinct AMR genes in large metagenomic datasets. Availability and implementation Code and datasets are publicly available at https://github.com/baharpan/cosmo/tree/LueVari. Supplementary information Supplementary data are available at Bioinformatics online.

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Succinct Dynamic de Bruijn Graphs

Bioinformatics ◽

10.1093/bioinformatics/btaa546 ◽

2020 ◽

Author(s):

Bahar Alipanahi ◽

Alan Kuhnle ◽

Simon J Puglisi ◽

Leena Salmela ◽

Christina Boucher

Keyword(s):

Data Structures ◽

Large Scale ◽

High Throughput Sequencing ◽

Supplementary Information ◽

De Bruijn Graph ◽

Sequencing Data ◽

Efficient Manner ◽

De Bruijn Graphs ◽

High Throughput Sequencing Data ◽

De Bruijn

Abstract Motivation The de Bruijn graph is one of the fundamental data structures for analysis of high throughput sequencing data. In order to be applicable to population-scale studies, it is essential to build and store the graph in a space- and time- efficient manner. In addition, due to the ever-changing nature of population studies, it has become essential to update the graph after construction e.g. add and remove nodes and edges. Although there has been substantial effort on making the construction and storage of the graph efficient, there is a limited amount of work in building the graph in an efficient and mutable manner. Hence, most space efficient data structures require complete reconstruction of the graph in order to add or remove edges or nodes. Results In this paper we present DynamicBOSS, a succinct representation of the de Bruijn graph that allows for an unlimited number of additions and deletions of nodes and edges. We compare our method with other competing methods and demonstrate that DynamicBOSS is the only method that supports both addition and deletion and is applicable to very large samples (e.g. greater than 15 billion k-mers). Competing dynamic methods e.g., FDBG (Crawford et al., 2018) cannot be constructed on large scale datasets, or cannot support both addition and deletion e.g., BiFrost (Holley and Melsted, 2019). Availability DynamicBOSS is publicly available at https://github.com/baharpan/dynboss. Supplementary information Supplementary data are available at Bioinformatics online.

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Building large updatable colored de Bruijn graphs via merging

Bioinformatics ◽

10.1093/bioinformatics/btz350 ◽

2019 ◽

Vol 35 (14) ◽

pp. i51-i60 ◽

Cited By ~ 11

Author(s):

Martin D Muggli ◽

Bahar Alipanahi ◽

Christina Boucher

Keyword(s):

Bloom Filter ◽

Supplementary Information ◽

Metagenomic Data ◽

De Bruijn Graph ◽

De Bruijn Graphs ◽

Working Space ◽

Fold Reduction ◽

De Bruijn ◽

Colored De Bruijn Graph ◽

Public Datasets

Abstract Motivation There exist several large genomic and metagenomic data collection efforts, including GenomeTrakr and MetaSub, which are routinely updated with new data. To analyze such datasets, memory-efficient methods to construct and store the colored de Bruijn graph were developed. Yet, a problem that has not been considered is constructing the colored de Bruijn graph in a scalable manner that allows new data to be added without reconstruction. This problem is important for large public datasets as scalability is needed but also the ability to update the construction is also needed. Results We create a method for constructing the colored de Bruijn graph for large datasets that is based on partitioning the data into smaller datasets, building the colored de Bruijn graph using a FM-index based representation, and succinctly merging these representations to build a single graph. The last step, merging succinctly, is the algorithmic challenge which we solve in this article. We refer to the resulting method as VariMerge. This construction method also allows the graph to be updated with new data. We validate our approach and show it produces a three-fold reduction in working space when constructing a colored de Bruijn graph for 8000 strains. Lastly, we compare VariMerge to other competing methods—including Vari, Rainbowfish, Mantis, Bloom Filter Trie, the method of Almodaresi et al. and Multi-BRWT—and illustrate that VariMerge is the only method that is capable of building the colored de Bruijn graph for 16 000 strains in a manner that allows it to be updated. Competing methods either did not scale to this large of a dataset or do not allow for additions without reconstruction. Availability and implementation VariMerge is available at https://github.com/cosmo-team/cosmo/tree/VARI-merge under GPLv3 license. Supplementary information Supplementary data are available at Bioinformatics online.

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neoepiscope improves neoepitope prediction with multivariant phasing

Bioinformatics ◽

10.1093/bioinformatics/btz653 ◽

2019 ◽

Vol 36 (3) ◽

pp. 713-720 ◽

Cited By ~ 5

Author(s):

Mary A Wood ◽

Austin Nguyen ◽

Adam J Struck ◽

Kyle Ellrott ◽

Abhinav Nellore ◽

...

Keyword(s):

False Negative ◽

Supplementary Information ◽

Supplementary File ◽

Sequencing Data ◽

Single Nucleotide Variants ◽

Single Nucleotide ◽

Somatic Variant ◽

Negative Results ◽

Multiple Datasets ◽

False Negative Results

Abstract Motivation The vast majority of tools for neoepitope prediction from DNA sequencing of complementary tumor and normal patient samples do not consider germline context or the potential for the co-occurrence of two or more somatic variants on the same mRNA transcript. Without consideration of these phenomena, existing approaches are likely to produce both false-positive and false-negative results, resulting in an inaccurate and incomplete picture of the cancer neoepitope landscape. We developed neoepiscope chiefly to address this issue for single nucleotide variants (SNVs) and insertions/deletions (indels). Results Herein, we illustrate how germline and somatic variant phasing affects neoepitope prediction across multiple datasets. We estimate that up to ∼5% of neoepitopes arising from SNVs and indels may require variant phasing for their accurate assessment. neoepiscope is performant, flexible and supports several major histocompatibility complex binding affinity prediction tools. Availability and implementation neoepiscope is available on GitHub at https://github.com/pdxgx/neoepiscope under the MIT license. Scripts for reproducing results described in the text are available at https://github.com/pdxgx/neoepiscope-paper under the MIT license. Additional data from this study, including summaries of variant phasing incidence and benchmarking wallclock times, are available in Supplementary Files 1, 2 and 3. Supplementary File 1 contains Supplementary Table 1, Supplementary Figures 1 and 2, and descriptions of Supplementary Tables 2–8. Supplementary File 2 contains Supplementary Tables 2–6 and 8. Supplementary File 3 contains Supplementary Table 7. Raw sequencing data used for the analyses in this manuscript are available from the Sequence Read Archive under accessions PRJNA278450, PRJNA312948, PRJNA307199, PRJNA343789, PRJNA357321, PRJNA293912, PRJNA369259, PRJNA305077, PRJNA306070, PRJNA82745 and PRJNA324705; from the European Genome-phenome Archive under accessions EGAD00001004352 and EGAD00001002731; and by direct request to the authors. Supplementary information Supplementary data are available at Bioinformatics online.

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Accurate determination of node and arc multiplicities in de bruijn graphs using conditional random fields

BMC Bioinformatics ◽

10.1186/s12859-020-03740-x ◽

2020 ◽

Vol 21 (1) ◽

Author(s):

Aranka Steyaert ◽

Pieter Audenaert ◽

Jan Fostier

Keyword(s):

Genomic Sequence ◽

Conditional Random Field ◽

Accurate Determination ◽

Next Generation Sequencing Data ◽

De Bruijn Graph ◽

Sequencing Data ◽

De Bruijn Graphs ◽

Sequencing Errors ◽

Expectation Maximisation ◽

De Bruijn

Abstract Background De Bruijn graphs are key data structures for the analysis of next-generation sequencing data. They efficiently represent the overlap between reads and hence, also the underlying genome sequence. However, sequencing errors and repeated subsequences render the identification of the true underlying sequence difficult. A key step in this process is the inference of the multiplicities of nodes and arcs in the graph. These multiplicities correspond to the number of times each k-mer (resp. k+1-mer) implied by a node (resp. arc) is present in the genomic sequence. Determining multiplicities thus reveals the repeat structure and presence of sequencing errors. Multiplicities of nodes/arcs in the de Bruijn graph are reflected in their coverage, however, coverage variability and coverage biases render their determination ambiguous. Current methods to determine node/arc multiplicities base their decisions solely on the information in nodes and arcs individually, under-utilising the information present in the sequencing data. Results To improve the accuracy with which node and arc multiplicities in a de Bruijn graph are inferred, we developed a conditional random field (CRF) model to efficiently combine the coverage information within each node/arc individually with the information of surrounding nodes and arcs. Multiplicities are thus collectively assigned in a more consistent manner. Conclusions We demonstrate that the CRF model yields significant improvements in accuracy and a more robust expectation-maximisation parameter estimation. True k-mers can be distinguished from erroneous k-mers with a higher F1 score than existing methods. A C++11 implementation is available at https://github.com/biointec/detoxunder the GNU AGPL v3.0 license.

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Faucet: streaming de novo assembly graph construction

10.1101/125658 ◽

2017 ◽

Author(s):

Roye Rozov ◽

Gil Goldshlager ◽

Eran Halperin ◽

Ron Shamir

Keyword(s):

Resource Use ◽

De Novo ◽

State Of The Art ◽

Supplementary Information ◽

De Bruijn Graph ◽

Assembly Quality ◽

Metagenome Assembly ◽

Streaming Algorithm ◽

Supplementary Material ◽

De Bruijn

AbstractMotivationWe present Faucet, a 2-pass streaming algorithm for assembly graph construction. Faucet builds an assembly graph incrementally as each read is processed. Thus, reads need not be stored locally, as they can be processed while downloading data and then discarded. We demonstrate this functionality by performing streaming graph assembly of publicly available data, and observe that the ratio of disk use to raw data size decreases as coverage is increased.ResultsFaucet pairs the de Bruijn graph obtained from the reads with additional meta-data derived from them. We show these metadata - coverage counts collected at junction k-mers and connections bridging between junction pairs - contain most salient information needed for assembly, and demonstrate they enable cleaning of metagenome assembly graphs, greatly improving contiguity while maintaining accuracy. We compared Faucet’s resource use and assembly quality to state of the art metagenome assemblers, as well as leading resource-efficient genome assemblers. Faucet used orders of magnitude less time and disk space than the specialized metagenome assemblers MetaSPAdes and Megahit, while also improving on their memory use; this broadly matched performance of other assemblers optimizing resource efficiency - namely, Minia and LightAssembler. However, on metagenomes tested, Faucet’s outputs had 14-110% higher mean NGA50 lengths compared to Minia, and 2-11-fold higher mean NGA50 lengths compared to LightAssembler, the only other streaming assembler available.AvailabilityFaucet is available at https://github.com/Shamir-Lab/[email protected],[email protected] information:Supplementary data are available at Bioinformatics online.

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A space and time-efficient index for the compacted colored de Bruijn graph

10.1101/191874 ◽

2017 ◽

Cited By ~ 3

Author(s):

Fatemeh Almodaresi ◽

Hirak Sarkar ◽

Rob Patro

Keyword(s):

Data Structure ◽

Pattern Search ◽

De Bruijn Graph ◽

Existing Structures ◽

Link Type ◽

Reference Information ◽

De Bruijn ◽

Colored De Bruijn Graph ◽

Asymptotically Efficient ◽

Fast Access

AbstractWe present a novel data structure for representing and indexing the compacted colored de Bruijn graph, which allows for efficient pattern matching and retrieval of the reference information associated with each k-mer. As the popularity of the de Bruijn graph as an index has increased over the past few years, so have the number of proposed representations of this structure. Existing structures typically fall into two categories; those that are hashing-based and provide very fast access to the underlying k-mer information, and those that are space-frugal and provide asymptotically efficient but practically slower pattern search.Our representation achieves a compromise between these two extremes. By building upon minimum perfect hashing, carefully organizing our data structure, and making use of succinct representations where applicable, our data structure provides practically fast k-mer lookup while greatly reducing the space compared to traditional hashing-based implementations. Further, we describe a sampling scheme built on the same underlying representation, which provides the ability to trade off k-mer query speed for a reduction in the de Bruijn graph index size. We believe this representation strikes a desirable balance between speed and space usage, and it will allow for fast search on large reference sequences.Pufferfish is developed in C++11, is open source (GPL v3), and is available at https://github.com/COMBINE-lab/Pufferfish. The scripts used to generate the results in this manuscript are available at https://github.com/COMBINE-lab/pufferfish_experiments.

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