scholarly journals Swan: a library for the analysis and visualization of long-read transcriptomes

2020 ◽  
Author(s):  
Fairlie Reese ◽  
Ali Mortazavi
Keyword(s):  
Rna Sequencing ◽  
Cell Lines ◽  
Intron Retention ◽  
Exon Skipping ◽  
Differentially Expressed ◽  
Transcript Isoforms ◽  
Sequencing Technologies ◽  
Oxford Nanopore ◽  
Long Read

Abstract Motivation Long-read RNA-sequencing technologies such as PacBio and Oxford Nanopore have discovered an explosion of new transcript isoforms that are difficult to visually analyze using currently available tools. We introduce the Swan Python library, which is designed to analyze and visualize transcript models. Results Swan finds 4909 differentially expressed transcripts between cell lines HepG2 and HFFc6, including 279 that are differentially expressed even though the parent gene is not. Additionally, Swan discovers 285 reproducible exon skipping and 47 intron retention events not recorded in the GENCODE v29 annotation. Availability and implementation The Swan library for Python 3 is available on PyPi at https://pypi.org/project/swan-vis/ and on GitHub at https://github.com/mortazavilab/swan_vis.

scholarly journals Swan: a library for the analysis and visualization of long-read transcriptomes

2020 ◽  
Author(s):  
Fairlie Reese ◽  
Ali Mortazavi
Keyword(s):  
Rna Sequencing ◽  
Cell Lines ◽  
Intron Retention ◽  
Exon Skipping ◽  
Differentially Expressed ◽  
Transcript Isoforms ◽  
Link Type ◽  
Sequencing Technologies ◽  
Oxford Nanopore ◽  
Long Read

AbstractMotivationLong-read RNA-sequencing technologies such as PacBio and Oxford Nanopore have discovered an explosion of new transcript isoforms that are difficult to visually analyze using currently available tools. We introduce the Swan Python library, which is designed to analyze and visualize transcript models.ResultsSwan finds 4,909 differentially expressed transcripts between cell lines HepG2 and HFFc6, including 279 that are differentially expressed even though the parent gene is not. Additionally, Swan discovers 1,021 reproducible exon skipping and 73 intron retention events not recorded in the GENCODE v29 annotation.AvailabilityThe Swan library for Python 3 is available on PyPi and on GitHub at https://pypi.org/project/swan-vis/1.0/ and https://github.com/mortazavilab/swan_paper.

scholarly journals Targeted Long-Read RNA Sequencing Demonstrates Transcriptional Diversity Driven by Splice-Site Variation in MYBPC3

2019 ◽  
Author(s):  
Alexandra Dainis ◽  
Elizabeth Tseng ◽  
Tyson A. Clark ◽  
Ting Hon ◽  
Matthew Wheeler ◽  
...  
Keyword(s):  
Rna Sequencing ◽  
Splice Site ◽  
De Novo ◽  
Exon Skipping ◽  
Molecular Evidence ◽  
Additional Tool ◽  
Oxford Nanopore ◽  
Site Variation ◽  
Long Read ◽  
Alternatively Spliced

ABSTRACTBackgroundClinical sequencing has traditionally focused on genomic DNA through the use of targeted panels and exome sequencing, rather than investigating the potential transcriptomic consequences of disease-associated variants. RNA sequencing has recently been shown to be an effective additional tool for identifying disease-causing variants. We here use targeted long-read genome and transcriptome sequencing to efficiently and economically identify molecular consequences of a rare, disease-associated variant in hypertrophic cardiomyopathy (HCM).Methods and ResultsOur study, which employed both Pacific Biosciences SMRT sequencing and Oxford Nanopore Technologies MinION sequencing, as well as two RNA targeting strategies, identified alternatively-spliced isoforms that resulted from a splice-site variant containing allele in HCM. These included a predicted in-frame exon-skipping event, as well as an abundance of additional isoforms with unexpected intron-inclusion, exon-extension, and pseudo-exon events. The use of long-read RNA sequencing allowed us to not only investigate full length alternatively-spliced transcripts but also to phase them back to the variant-containing allele.ConclusionsWe suggest that targeted, long-read RNA sequencing in conjunction with genome sequencing may provide additional molecular evidence of disease for rare or de novo variants in cardiovascular disease, as well as providing new information about the consequence of these variants on downstream RNA and protein expression.

scholarly journals Direct nanopore sequencing of mRNA reveals landscape of transcript isoforms in apicomplexan parasites

2020 ◽  
Author(s):  
V Vern Lee ◽  
Louise M. Judd ◽  
Aaron R. Jex ◽  
Kathryn E. Holt ◽  
Christopher J. Tonkin ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Rna Sequencing ◽  
Intron Retention ◽  
Transcript Level ◽  
Full Length ◽  
Sequencing Platform ◽  
Apicomplexan Parasites ◽  
Oxford Nanopore ◽  
Long Read ◽  
Widespread Phenomenon

AbstractAlternative splicing is a widespread phenomenon in metazoans by which single genes are able to produce multiple isoforms of the gene product. However, this has been poorly characterised in apicomplexans, a major phylum of some of the most important global parasites. Efforts have been hampered by atypical transcriptomic features, such as the high AT content of Plasmodium RNA, but also the limitations of short read sequencing in deciphering complex splicing events. In this study, we utilised the long read direct RNA sequencing platform developed by Oxford Nanopore Technologies (ONT) to survey the alternative splicing landscape of Toxoplasma gondii and Plasmodium falciparum. We find that while native RNA sequencing has a reduced throughput, it allows us to obtain full-length or near full-length transcripts with comparable quantification to Illumina sequencing. By comparing this data with available gene models, we find widespread alternative splicing, particular intron retention, in these parasites. Most of these transcripts contain premature stop codons, suggesting that in these parasites, alternative splicing represents a pathway to transcriptomic diversity, rather than expanding proteomic diversity. Moreover, alternative splicing rates are comparable between parasites, suggesting a shared splicing machinery, despite notable transcriptomic differences between the parasites. This work highlights a strategy in using long read sequencing to understand splicing events at the whole transcript level, and has implications in future interpretation of RNA-seq studies.

scholarly journals Hapo-G, haplotype-aware polishing of genome assemblies with accurate reads

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Jean-Marc Aury ◽  
Benjamin Istace
Keyword(s):  
Single Molecule ◽  
Direct Consequence ◽  
High Quality ◽  
Sequencing Errors ◽  
Coding Regions ◽  
Sequencing Technologies ◽  
Long Reads ◽  
Oxford Nanopore ◽  
Long Read ◽  
Genome Assemblies

Abstract Single-molecule sequencing technologies have recently been commercialized by Pacific Biosciences and Oxford Nanopore with the promise of sequencing long DNA fragments (kilobases to megabases order) and then, using efficient algorithms, provide high quality assemblies in terms of contiguity and completeness of repetitive regions. However, the error rate of long-read technologies is higher than that of short-read technologies. This has a direct consequence on the base quality of genome assemblies, particularly in coding regions where sequencing errors can disrupt the coding frame of genes. In the case of diploid genomes, the consensus of a given gene can be a mixture between the two haplotypes and can lead to premature stop codons. Several methods have been developed to polish genome assemblies using short reads and generally, they inspect the nucleotide one by one, and provide a correction for each nucleotide of the input assembly. As a result, these algorithms are not able to properly process diploid genomes and they typically switch from one haplotype to another. Herein we proposed Hapo-G (Haplotype-Aware Polishing Of Genomes), a new algorithm capable of incorporating phasing information from high-quality reads (short or long-reads) to polish genome assemblies and in particular assemblies of diploid and heterozygous genomes.

scholarly journals TagSeqTools: a flexible and comprehensive analysis pipeline for NAD tagSeq data

2020 ◽  
Author(s):  
Huan Zhong ◽  
Zongwei Cai ◽  
Zhu Yang ◽  
Yiji Xia
Keyword(s):  
Rna Sequencing ◽  
Comprehensive Analysis ◽  
Enzymatic Reactions ◽  
Computational Tool ◽  
Sequencing Data ◽  
Analysis Pipeline ◽  
Oxford Nanopore ◽  
Long Read ◽  
Identification And Characterization

AbstractNAD tagSeq has recently been developed for the identification and characterization of NAD+-capped RNAs (NAD-RNAs). This method adopts a strategy of chemo-enzymatic reactions to label the NAD-RNAs with a synthetic RNA tag before subjecting to the Oxford Nanopore direct RNA sequencing. A computational tool designed for analyzing the sequencing data of tagged RNA will facilitate the broader application of this method. Hence, we introduce TagSeqTools as a flexible, general pipeline for the identification and quantification of tagged RNAs (i.e., NAD+-capped RNAs) using long-read transcriptome sequencing data generated by NAD tagSeq method. TagSeqTools comprises two major modules, TagSeek for differentiating tagged and untagged reads, and TagSeqQuant for the quantitative and further characterization analysis of genes and isoforms. Besides, the pipeline also integrates some advanced functions to identify antisense or splicing, and supports the data reformation for visualization. Therefore, TagSeqTools provides a convenient and comprehensive workflow for researchers to analyze the data produced by the NAD tagSeq method or other tagging-based experiments using Oxford nanopore direct RNA sequencing. The pipeline is available at https://github.com/dorothyzh/TagSeqTools, under Apache License 2.0.

scholarly journals Improving the Chromosome-Level Genome Assembly of the Siamese Fighting Fish (Betta splendens) in a University Master’s Course

2020 ◽  
Vol 10 (7) ◽  
pp. 2179-2183 ◽  
Author(s):  
Stefan Prost ◽  
Malte Petersen ◽  
Martin Grethlein ◽  
Sarah Joy Hahn ◽  
Nina Kuschik-Maczollek ◽  
...  
Keyword(s):  
Genome Assembly ◽  
High Throughput Sequencing ◽  
Siamese Fighting Fish ◽  
Betta Splendens ◽  
High Quality ◽  
Sequencing Platform ◽  
Sequencing Technologies ◽  
Oxford Nanopore ◽  
Long Read ◽  
Chromosome Level

Ever decreasing costs along with advances in sequencing and library preparation technologies enable even small research groups to generate chromosome-level assemblies today. Here we report the generation of an improved chromosome-level assembly for the Siamese fighting fish (Betta splendens) that was carried out during a practical university master’s course. The Siamese fighting fish is a popular aquarium fish and an emerging model species for research on aggressive behavior. We updated the current genome assembly by generating a new long-read nanopore-based assembly with subsequent scaffolding to chromosome-level using previously published Hi-C data. The use of ∼35x nanopore-based long-read data sequenced on a MinION platform (Oxford Nanopore Technologies) allowed us to generate a baseline assembly of only 1,276 contigs with a contig N50 of 2.1 Mbp, and a total length of 441 Mbp. Scaffolding using the Hi-C data resulted in 109 scaffolds with a scaffold N50 of 20.7 Mbp. More than 99% of the assembly is comprised in 21 scaffolds. The assembly showed the presence of 96.1% complete BUSCO genes from the Actinopterygii dataset indicating a high quality of the assembly. We present an improved full chromosome-level assembly of the Siamese fighting fish generated during a university master’s course. The use of ∼35× long-read nanopore data drastically improved the baseline assembly in terms of continuity. We show that relatively in-expensive high-throughput sequencing technologies such as the long-read MinION sequencing platform can be used in educational settings allowing the students to gain practical skills in modern genomics and generate high quality results that benefit downstream research projects.

scholarly journals Evaluation of Germline Structural Variant Calling Methods for Nanopore Sequencing Data

2021 ◽  
Vol 12 ◽  
Author(s):  
Davide Bolognini ◽  
Alberto Magi
Keyword(s):  
Variant Calling ◽  
Research Report ◽  
Nanopore Sequencing ◽  
Sequencing Data ◽  
Factors Affecting ◽  
Sequencing Technologies ◽  
Long Reads ◽  
Oxford Nanopore ◽  
Sequencing Studies ◽  
Long Read

Structural variants (SVs) are genomic rearrangements that involve at least 50 nucleotides and are known to have a serious impact on human health. While prior short-read sequencing technologies have often proved inadequate for a comprehensive assessment of structural variation, more recent long reads from Oxford Nanopore Technologies have already been proven invaluable for the discovery of large SVs and hold the potential to facilitate the resolution of the full SV spectrum. With many long-read sequencing studies to follow, it is crucial to assess factors affecting current SV calling pipelines for nanopore sequencing data. In this brief research report, we evaluate and compare the performances of five long-read SV callers across four long-read aligners using both real and synthetic nanopore datasets. In particular, we focus on the effects of read alignment, sequencing coverage, and variant allele depth on the detection and genotyping of SVs of different types and size ranges and provide insights into precision and recall of SV callsets generated by integrating the various long-read aligners and SV callers. The computational pipeline we propose is publicly available at https://github.com/davidebolo1993/EViNCe and can be adjusted to further evaluate future nanopore sequencing datasets.

scholarly journals Picopore: A tool for reducing the storage size of Oxford Nanopore Technologies datasets without loss of functionality

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 227 ◽  
Author(s):  
Scott Gigante
Keyword(s):  
Data Storage ◽  
Data Generation ◽  
Biologically Relevant ◽  
Sequencing Technologies ◽  
Long Term Storage ◽  
Oxford Nanopore ◽  
Long Read ◽  
Oxford Nanopore Technologies ◽  
Term Storage

Oxford Nanopore Technologies' (ONT's) MinION and PromethION long-read sequencing technologies are emerging as genuine alternatives to established Next-Generation Sequencing technologies. A combination of the highly redundant file format and a rapid increase in data generation have created a significant problem both for immediate data storage on MinION-capable laptops, and for long-term storage on lab data servers. We developed Picopore, a software suite offering three methods of compression. Picopore's lossless and deep lossless methods provide a 25% and 44% average reduction in size, respectively, without removing any data from the files. Picopore's raw method provides an 88% average reduction in size, while retaining biologically relevant data for the end-user. All methods have the capacity to run in real-time in parallel to a sequencing run, reducing demand for both immediate and long-term storage space.

scholarly journals A chromosome-scale assembly of the sorghum genome using nanopore sequencing and optical mapping

2018 ◽  
Author(s):  
Stáphane Deschamps ◽  
Yun Zhang ◽  
Victor Llaca ◽  
Liang Ye ◽  
Gregory May ◽  
...  
Keyword(s):  
Sorghum Bicolor ◽  
De Novo ◽  
Hybrid Assembly ◽  
The Public ◽  
Sequencing Technologies ◽  
Oxford Nanopore ◽  
Long Read ◽  
Optical Maps ◽  
Eukaryotic Genomes ◽  
Direct Label

The advent of long-read sequencing technologies has greatly facilitated assemblies of large eukaryotic genomes. In this paper, Oxford Nanopore sequences generated on a MinION sequencer were combined with BioNano Genomics Direct Label and Stain (DLS) optical maps to generate a chromosome-scale de novo assembly of the repeat-rich Sorghum bicolor Tx430 genome. The final hybrid assembly consists of 29 scaffolds, encompassing in most cases entire chromosome arms. It has a scaffold N50 value of 33.28Mbps and covers >90% of Sorghum bicolor expected genome length. A sequence accuracy of 99.67% was obtained in unique regions after aligning contigs against Illumina Tx430 data. Alignments showed that 99.4% of the 34,211 public gene models are present in the assembly, including 94.2% mapping end-to-end. Comparisons of the DLS optical maps against the public Sorghum Bicolor v3.0.1 BTx623 genome assembly suggest the presence of substantial genomic rearrangements whose origin remains to be determined.

scholarly journals Chasing perfection: validation and polishing strategies for telomere-to-telomere genome assemblies

2021 ◽  
Author(s):  
Arang Rhie ◽  
Ann Mc Cartney ◽  
Kishwar Shafin ◽  
Michael Alonge ◽  
Andrey Bzikadze ◽  
...  
Keyword(s):  
Genome Assembly ◽  
Tandem Repeats ◽  
Hydatidiform Mole ◽  
Segmental Duplications ◽  
Sequencing Technologies ◽  
Oxford Nanopore ◽  
Human Genome Assembly ◽  
Long Read ◽  
Genome Assemblies ◽  
Oxford Nanopore Technologies

Abstract Advances in long-read sequencing technologies and genome assembly methods have enabled the recent completion of the first Telomere-to-Telomere (T2T) human genome assembly, which resolves complex segmental duplications and large tandem repeats, including centromeric satellite arrays in a complete hydatidiform mole (CHM13). Though derived from highly accurate sequencing, evaluation revealed that the initial T2T draft assembly had evidence of small errors and structural misassemblies. To correct these errors, we designed a novel repeat-aware polishing strategy that made accurate assembly corrections in large repeats without overcorrection, ultimately fixing 51% of the existing errors and improving the assembly QV to 73.9. By comparing our results to standard automated polishing tools, we outline common polishing errors and offer practical suggestions for genome projects with limited resources. We also show how sequencing biases in both PacBio HiFi and Oxford Nanopore Technologies reads cause signature assembly errors that can be corrected with a diverse panel of sequencing technologies

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