scholarly journals ClusTrast: a short read de novo transcript isoform assembler guided by clustered contigs

2022 ◽  
Author(s):  
Karl Johan Westrin ◽  
Warren W Kretzschmar ◽  
Olof Emanuelsson
Keyword(s):  
Alternative Splicing ◽  
Reference Genome ◽  
De Novo ◽  
Transcriptome Assembly ◽  
Sequencing Data ◽  
Short Read ◽  
Transcript Isoforms ◽  
Short Reads ◽  
Moderate Reduction ◽  
Eukaryotic Species

Motivation: Transcriptome assembly from RNA sequencing data in species without a reliable reference genome has to be performed de novo, but studies have shown that de novo methods often have inadequate reconstruction ability of transcript isoforms. This impedes the study of alternative splicing, in particular for lowly expressed isoforms. Result: We present the de novo transcript isoform assembler ClusTrast, which clusters a set of guiding contigs by similarity, aligns short reads to the guiding contigs, and assembles each clustered set of short reads individually. We tested ClusTrast on datasets from six eukaryotic species, and showed that ClusTrast reconstructed more expressed known isoforms than any of the other tested de novo assemblers, at a moderate reduction in precision. An appreciable fraction were reconstructed to at least 95% of their length. We suggest that ClusTrast will be useful for studying alternative splicing in the absence of a reference genome. Availability and implementation: The code and usage instructions are available at https://github.com/karljohanw/clustrast.

scholarly journals DACCOR - Detection, charACterization, and reconstruction of Repetitive regions in bacterial genomes

2017 ◽  
Author(s):  
Alexander Seitz ◽  
Friederike Hanssen ◽  
Kay Nieselt
Keyword(s):  
Base Pair ◽  
Repetitive Sequence ◽  
Reference Genome ◽  
De Novo ◽  
Treponema Pallidum ◽  
Sequencing Data ◽  
Bacterial Genomes ◽  
Short Read ◽  
Short Reads ◽  
Short Read Sequencing

The reconstruction of genomes using mapping based approaches with short reads experiences difficulties when resolving repetitive regions. These repetitive regions in genomes result in low mapping qualities of the respective reads, which in turn lead to many unresolved bases of the genotypers. Currently, the reconstruction of these regions is often based on modified references in which the repetitive regions are masked. However, for many references such masked genomes are not available or are based on repetitive regions of other genomes. Our idea is to identify repetitive regions in the reference genome de novo. These regions can then be used to reconstruct them separately using short read sequencing data. Afterwards the reconstructed repetitive sequence can be inserted into the reconstructed genome. We present the program DACCOR, which performs these steps automatically. Our results show an increased base pair resolution of the repetitive regions in the reconstruction of Treponema pallidum samples, resulting in fewer unresolved bases.

scholarly journals DACCOR–Detection, characterization, and reconstruction of repetitive regions in bacterial genomes

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4742 ◽  
Author(s):  
Alexander Seitz ◽  
Friederike Hanssen ◽  
Kay Nieselt
Keyword(s):  
Base Pair ◽  
Repetitive Sequence ◽  
Reference Genome ◽  
De Novo ◽  
Treponema Pallidum ◽  
Sequencing Data ◽  
Bacterial Genomes ◽  
Short Read ◽  
Short Reads ◽  
Short Read Sequencing

The reconstruction of genomes using mapping-based approaches with short reads experiences difficulties when resolving repetitive regions. These repetitive regions in genomes result in low mapping qualities of the respective reads, which in turn lead to many unresolved bases. Currently, the reconstruction of these regions is often based on modified references in which the repetitive regions are masked. However, for many references, such masked genomes are not available or are based on repetitive regions of other genomes. Our idea is to identify repetitive regions in the reference genome de novo. These regions can then be used to reconstruct them separately using short read sequencing data. Afterward, the reconstructed repetitive sequence can be inserted into the reconstructed genome. We present the program detection, characterization, and reconstruction of repetitive regions, which performs these steps automatically. Our results show an increased base pair resolution of the repetitive regions in the reconstruction of Treponema pallidum samples, resulting in fewer unresolved bases.

scholarly journals DACCOR - Detection, charACterization, and reconstruction of Repetitive regions in bacterial genomes

2017 ◽  
Author(s):  
Alexander Seitz ◽  
Friederike Hanssen ◽  
Kay Nieselt
Keyword(s):  
Base Pair ◽  
Repetitive Sequence ◽  
Reference Genome ◽  
De Novo ◽  
Treponema Pallidum ◽  
Sequencing Data ◽  
Bacterial Genomes ◽  
Short Read ◽  
Short Reads ◽  
Short Read Sequencing

The reconstruction of genomes using mapping based approaches with short reads experiences difficulties when resolving repetitive regions. These repetitive regions in genomes result in low mapping qualities of the respective reads, which in turn lead to many unresolved bases of the genotypers. Currently, the reconstruction of these regions is often based on modified references in which the repetitive regions are masked. However, for many references such masked genomes are not available or are based on repetitive regions of other genomes. Our idea is to identify repetitive regions in the reference genome de novo. These regions can then be used to reconstruct them separately using short read sequencing data. Afterwards the reconstructed repetitive sequence can be inserted into the reconstructed genome. We present the program DACCOR, which performs these steps automatically. Our results show an increased base pair resolution of the repetitive regions in the reconstruction of Treponema pallidum samples, resulting in fewer unresolved bases.

AStrap: identification of alternative splicing from transcript sequences without a reference genome

2018 ◽  
Vol 35 (15) ◽  
pp. 2654-2656 ◽  
Author(s):  
Guoli Ji ◽  
Wenbin Ye ◽  
Yaru Su ◽  
Moliang Chen ◽  
Guangzao Huang ◽  
...  
Keyword(s):  
Machine Learning ◽  
Alternative Splicing ◽  
Single Molecule ◽  
Reference Genome ◽  
De Novo ◽  
Supplementary Information ◽  
Model Organisms ◽  
Sequencing Data ◽  
Extensive Evaluation ◽  
Reference Genomes

Abstract Summary Alternative splicing (AS) is a well-established mechanism for increasing transcriptome and proteome diversity, however, detecting AS events and distinguishing among AS types in organisms without available reference genomes remains challenging. We developed a de novo approach called AStrap for AS analysis without using a reference genome. AStrap identifies AS events by extensive pair-wise alignments of transcript sequences and predicts AS types by a machine-learning model integrating more than 500 assembled features. We evaluated AStrap using collected AS events from reference genomes of rice and human as well as single-molecule real-time sequencing data from Amborella trichopoda. Results show that AStrap can identify much more AS events with comparable or higher accuracy than the competing method. AStrap also possesses a unique feature of predicting AS types, which achieves an overall accuracy of ∼0.87 for different species. Extensive evaluation of AStrap using different parameters, sample sizes and machine-learning models on different species also demonstrates the robustness and flexibility of AStrap. AStrap could be a valuable addition to the community for the study of AS in non-model organisms with limited genetic resources. Availability and implementation AStrap is available for download at https://github.com/BMILAB/AStrap. Supplementary information Supplementary data are available at Bioinformatics online.

scholarly journals SuperTranscript: a data driven reference for analysis and visualisation of transcriptomes

2016 ◽  
Author(s):  
Nadia M Davidson ◽  
Anthony DK Hawkins ◽  
Alicia Oshlack
Keyword(s):  
Reference Genome ◽  
De Novo ◽  
Transcriptome Assembly ◽  
Model Organisms ◽  
Sequencing Data ◽  
Expressed Sequence ◽  
Model Sequencing ◽  
Reference Genomes ◽  
Exonic Sequence ◽  
Single Sequence

AbstractNumerous methods have been developed to analyse RNA sequencing data, but most rely on the availability of a reference genome, making them unsuitable for non-model organisms. De novo transcriptome assembly can build a reference transcriptome from the non-model sequencing data, but falls short of allowing most tools to be applied. Here we present superTranscripts, a simple but powerful solution to bridge that gap. SuperTranscripts are a substitute for a reference genome, consisting of all the unique exonic sequence, in transcriptional order, such that each gene is represented by a single sequence. We demonstrate how superTranscripts allow visualization, variant detection and differential isoform detection in non-model organisms, using widely applied methods that are designed to work with reference genomes. SuperTranscripts can also be applied to model organisms to enhance visualization and discover novel expressed sequence. We describe Lace, software to construct superTranscripts from any set of transcripts including de novo assembled transcriptomes. In addition we used Lace to combine reference and assembled transcriptomes for chicken and recovered the sequence of hundreds of gaps in the reference genome.

scholarly journals Genome Assembly of the Popular Korean Soybean Cultivar Hwangkeum

2021 ◽  
Author(s):  
Myung-Shin Kim ◽  
Taeyoung Lee ◽  
Jeonghun Baek ◽  
Ji Hong Kim ◽  
Changhoon Kim ◽  
...  
Keyword(s):  
Reference Genome ◽  
De Novo ◽  
Anthocyanin Biosynthesis ◽  
Genetic Maps ◽  
Soybean Cultivar ◽  
Gene Arrangement ◽  
Nucleotide Polymorphisms ◽  
Sequencing Data ◽  
Crop Species ◽  
Satellite Repeats

AbstractMassive resequencing efforts have been undertaken to catalog allelic variants in major crop species including soybean, but the scope of the information for genetic variation often depends on short sequence reads mapped to the extant reference genome. Additional de novo assembled genome sequences provide a unique opportunity to explore a dispensable genome fraction in the pan-genome of a species. Here, we report the de novo assembly and annotation of Hwangkeum, a popular soybean cultivar in Korea. The assembly was constructed using PromethION nanopore sequencing data and two genetic maps, and was then error-corrected using Illumina short-reads and PacBio SMRT reads. The 933.12 Mb assembly was annotated 79,870 transcripts for 58,550 genes using RNA-Seq data and the public soybean annotation set. Comparison of the Hwangkeum assembly with the Williams 82 soybean reference genome sequence revealed 1.8 million single-nucleotide polymorphisms, 0.5 million indels, and 25 thousand putative structural variants. However, there was no natural megabase-scale chromosomal rearrangement. Incidentally, by adding two novel groups, we found that soybean contains four clearly separated groups of centromeric satellite repeats. Analyses of satellite repeats and gene content suggested that the Hwangkeum assembly is a high-quality assembly. This was further supported by comparison of the marker arrangement of anthocyanin biosynthesis genes and of gene arrangement at the Rsv3 locus. Therefore, the results indicate that the de novo assembly of Hwangkeum is a valuable additional reference genome resource for characterizing traits for the improvement of this important crop species.

PERHAPS: Paired-End short Reads-based HAPlotyping from next-generation Sequencing data

2020 ◽  
Author(s):  
Jie Huang ◽  
Stefano Pallotti ◽  
Qianling Zhou ◽  
Marcus Kleber ◽  
Xiaomeng Xin ◽  
...  
Keyword(s):  
Next Generation Sequencing ◽  
Snp Array ◽  
Simple Approach ◽  
Next Generation Sequencing Data ◽  
Next Generation ◽  
Sequencing Data ◽  
Short Read ◽  
Array Data ◽  
Short Reads ◽  
Generation Sequencing

Abstract The identification of rare haplotypes may greatly expand our knowledge in the genetic architecture of both complex and monogenic traits. To this aim, we developed PERHAPS (Paired-End short Reads-based HAPlotyping from next-generation Sequencing data), a new and simple approach to directly call haplotypes from short-read, paired-end Next Generation Sequencing (NGS) data. To benchmark this method, we considered the APOE classic polymorphism (*1/*2/*3/*4), since it represents one of the best examples of functional polymorphism arising from the haplotype combination of two Single Nucleotide Polymorphisms (SNPs). We leveraged the big Whole Exome Sequencing (WES) and SNP-array data obtained from the multi-ethnic UK BioBank (UKBB, N=48,855). By applying PERHAPS, based on piecing together the paired-end reads according to their FASTQ-labels, we extracted the haplotype data, along with their frequencies and the individual diplotype. Concordance rates between WES directly called diplotypes and the ones generated through statistical pre-phasing and imputation of SNP-array data are extremely high (>99%), either when stratifying the sample by SNP-array genotyping batch or self-reported ethnic group. Hardy-Weinberg Equilibrium tests and the comparison of obtained haplotype frequencies with the ones available from the 1000 Genome Project further supported the reliability of PERHAPS. Notably, we were able to determine the existence of the rare APOE*1 haplotype in two unrelated African subjects from UKBB, supporting its presence at appreciable frequency (approximatively 0.5%) in the African Yoruba population. Despite acknowledging some technical shortcomings, PERHAPS represents a novel and simple approach that will partly overcome the limitations in direct haplotype calling from short read-based sequencing.

scholarly journals Closing Human Reference Genome Gaps: Identifying and Characterizing Gap-Closing Sequences

2020 ◽  
Vol 10 (8) ◽  
pp. 2801-2809 ◽  
Author(s):  
Tingting Zhao ◽  
Zhongqu Duan ◽  
Georgi Z. Genchev ◽  
Hui Lu
Keyword(s):  
Reference Genome ◽  
De Novo ◽  
Sequence Length ◽  
Sequencing Data ◽  
Human Reference Genome ◽  
Satellite Sequences ◽  
Long Read ◽  
Data Gap ◽  
Simple Repeats ◽  
Gap Closing

Despite continuous updates of the human reference genome, there are still hundreds of unresolved gaps which account for about 5% of the total sequence length. Given the availability of whole genome de novo assemblies, especially those derived from long-read sequencing data, gap-closing sequences can be determined. By comparing 17 de novo long-read sequencing assemblies with the human reference genome, we identified a total of 1,125 gap-closing sequences for 132 (16.9% of 783) gaps and added up to 2.2 Mb novel sequences to the human reference genome. More than 90% of the non-redundant sequences could be verified by unmapped reads from the Simons Genome Diversity Project dataset. In addition, 15.6% of the non-reference sequences were found in at least one of four non-human primate genomes. We further demonstrated that the non-redundant sequences had high content of simple repeats and satellite sequences. Moreover, 43 (32.6%) of the 132 closed gaps were shown to be polymorphic; such sequences may play an important biological role and can be useful in the investigation of human genetic diversity.

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