Biology subjects

Deveson, I. W.

Publications and source records attributed to Deveson, I. W..

34 records · Page 2Linked to original sources

bioRxiv2023

Extensive DNA methylome rearrangement during early lamprey embryogenesis

DNA methylation (5-methylcytosine, 5mC) is a repressive gene regulatory mark widespread in vertebrate genomes, yet the developmental dynamics in which 5mC patterns are established vary across species. While mammals undergo two rounds of global 5mC erasure, the zebrafish genome exhibits localized maternal-to-paternal 5mC remodeling, in which the sperm epigenome is inherited in the early embryo. To date, it is unclear how evolutionarily conserved such 5mC remodeling strategies are, and what their biological function is. Here, we studied 5mC dynamics during the embryonic development of sea lamprey (Petromyzon marinus), a jawless vertebrate which occupies a critical phylogenetic position as the sister group of the jawed vertebrates. We employed base-resolution 5mC quantification in the lamprey germline, embryonic and somatic tissues, and discovered large-scale maternal-to-paternal epigenome remodeling that affects >30% of the embryonic genome and is predominantly associated with partially methylated domains (PMDs). We further demonstrate that sequences eliminated during programmed genome rearrangement (PGR), a hallmark of lamprey embryogenesis, are hypermethylated in sperm prior to the onset of PGR. Our study thus unveils important insights into the evolutionary origins of vertebrate 5mC reprogramming, and how this process might participate in diverse developmental strategies.

developmental biology↗

bioRxiv2023

Squigulator: simulation of nanopore sequencing signal data with tunable noise parameters

In silico simulation of next-generation sequencing data is a technique used widely in the genomics field. However, there is currently a lack of optimal tools for creating simulated data from third-generation nanopore sequencing devices, which measure DNA or RNA molecules in the form of time-series current signal data. Here, we introduce Squigulator, a fast and simple tool for simulation of realistic nanopore signal data. Squigulator takes a reference genome, transcriptome or read sequences and generates corresponding raw nanopore signal data. This is compatible with basecalling software from Oxford Nanopore Technologies (ONT) and other third-party tools, thereby providing a useful substrate for testing, debugging, validation and optimisation of nanopore analysis methods. The user may generate noise-free ideal data, realistic data with noise profiles emulating specific ONT protocols, or they may deterministically modify noise parameters and other variables to shape the data to their needs. To highlight its utility, we use Squigulator to model the degree to which different types of noise impact the accuracy of ONT basecalling and downstream variant detection, revealing new insights into the properties of ONT data. We provide Squigulator as an open-source tool for the nanopore community: https://github.com/hasindu2008/squigulator

bioinformatics↗

bioRxiv2023

Accelerated nanopore basecalling with SLOW5 data format

Nanopore sequencing is emerging as a key pillar in the genomic technology landscape but computational constraints limiting its scalability remain to be overcome. The translation of raw current signal data into DNA or RNA sequence reads, known as basecalling, is a major friction in any nanopore sequencing workflow. Here, we exploit the advantages of the recently developed signal data format SLOW5 to streamline and accelerate nanopore basecalling on high-performance computer (HPC) and cloud environments. SLOW5 permits highly efficient sequential data access, eliminating a significant analysis bottleneck. To take advantage of this, we introduce Buttery-eel, an open-source wrapper for Oxford Nanopores Guppy basecaller that enables SLOW5 data access, resulting in performance improvements that are essential for scalable, affordable basecalling.

bioinformatics↗

bioRxiv2022

Laboratory evolution and polyploid SCRaMbLE reveal genomic plasticity to synthetic chromosome defects and rearrangements

We have designed, constructed, and debugged a synthetic 753,096 bp version of Saccharomyces cerevisiae chromosome XIV as part of the international Sc2.0 project. We showed that certain synthetic loxPsym recombination sites can interfere with mitochondrial protein localization, that the deletion of one intron (NOG2) reduced fitness, and that a reassigned stop codon can lead to a growth defect. In parallel to these rational debugging modifications, we used Adaptive Laboratory Evolution to generate a general growth defect suppressor rearrangement in the form of increased TAR1 copy number. We also extended the utility of the Synthetic Chromosome Recombination and Modification by LoxP-mediated Evolution (SCRaMbLE) system by engineering synthetic-wild-type tetraploid hybrid strains that buffer against essential gene loss. The presence of wild-type chromosomes in the hybrid tetraploids increased post-SCRaMbLE viability and heterologous DNA integration, highlighting the plasticity of the S. cerevisiae genome in the presence of rational and non-rational modifications.

synthetic biology↗

bioRxiv2022

Flexible and efficient handling of nanopore sequencing signal data with slow5tools

BackgroundNanopore sequencing is an emerging technology that is being rapidly adopted in research and clinical genomics. We recently developed SLOW5, a new file format for storage and analysis of raw data from nanopore sequencing experiments. SLOW5 is a community-centric, open source format that offers considerable performance benefits over the existing nanopore data format, known as FAST5. Here we introduce slow5tools, a simple, intuitive toolkit for handling nanopore raw signal data in SLOW5 format. ResultsSlow5tools enables lossless FAST5-to-SLOW5 and SLOW5-to-FAST5 data conversion, and a range of tools for structuring, indexing, viewing and querying SLOW5 files. Slow5tools uses multi-threading, multi-processing and other engineering strategies to achieve fast data conversion and manipulation, including live FAST5-to-SLOW5 conversion during sequencing. We outline a series of examples and benchmarking experiments to illustrate slow5tools usage, and describe the engineering principles underpinning its high performance. ConclusionSlow5tools is an essential toolkit for handling nanopore signal data, which was developed to support adoption of SLOW5 by the nanopore community. Slow5tools is written in C/C++ with minimal dependencies and is freely available as an open-source program under an MIT licence: https://github.com/hasindu2008/slow5tools.

bioinformatics↗

bioRxiv2021

Sex-specific transcriptomic and epitranscriptomic signatures of PTSD-like fear acquisition.

Our understanding of the molecular pathology of posttraumatic stress disorder (PTSD) is rapidly evolving and is being driven by advances in sequencing techniques. Conventional short-read RNA sequencing (RNA-seq) is a central tool in transcriptomics research that enables unbiased gene expression profiling. With the recent emergence of Oxford Nanopore direct RNA-seq (dRNA-seq), it is now also possible to interrogate diverse RNA modifications, collectively known as the epitranscriptome. Here, we present our analyses of the male and female mouse amygdala transcriptome and epitranscriptome, obtained using parallel Illumina RNA-seq and Oxford Nanopore dRNA-seq, associated with the acquisition of PTSD-like fear induced by Pavlovian cued-fear conditioning. We report significant sex-specific differences in the amygdala transcriptional response during fear acquisition, and a range of shared and dimorphic epitranscriptomic signatures. Differential RNA modifications are enriched among mRNA transcripts associated with neurotransmitter regulation and mitochondrial function, many of which have been previously implicated in PTSD. Very few differentially modified transcripts are also differentially expressed, suggesting an influential, expression-independent role for epitranscriptional regulation in PTSD-like fear-acquisition. Overall, our application of conventional and newly developed methods provides a platform for future work that will lead to new insights into and therapeutics for PTSD.

neuroscience↗

bioRxiv2021

SLOW5: a new file format enables massive acceleration of nanopore sequencing data analysis

Nanopore sequencing is an emerging genomic technology with great potential. However, the storage and analysis of nanopore sequencing data have become major bottlenecks preventing more widespread adoption in research and clinical genomics. Here, we elucidate an inherent limitation in the file format used to store raw nanopore data - known as FAST5 - that prevents efficient analysis on high-performance computing (HPC) systems. To overcome this, we have developed SLOW5, an alternative file format that permits efficient parallelisation and, thereby, acceleration of nanopore data analysis. For example, we show that using SLOW5 format, instead of FAST5, reduces the time and cost of genome-wide DNA methylation profiling by an order of magnitude on common HPC systems, and delivers consistent improvements on a wide range of different architectures. With a simple, accessible file structure and a ~25% reduction in size compared to FAST5, SLOW5 format will deliver substantial benefits to all areas of the nanopore community.

genomics↗

bioRxiv2021

Human genome integration of SARS-CoV-2 contradicted by long-read sequencing

A recent study proposed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) hijacks the LINE-1 (L1) retrotransposition machinery to integrate into the DNA of infected cells. If confirmed, this finding could have significant clinical implications. Here, we applied deep (>50x) long-read Oxford Nanopore Technologies (ONT) sequencing to HEK293T cells infected with SARS-CoV-2, and did not find the virus integrated into the genome. By examining ONT data from separate HEK293T cultivars, we completely resolved 78 L1 insertions arising in vitro in the absence of L1 overexpression systems. ONT sequencing applied to hepatitis B virus (HBV) positive liver cancer tissues located a single HBV insertion. These experiments demonstrate reliable resolution of retrotransposon and exogenous virus insertions via ONT sequencing. That we found no evidence of SARS-CoV-2 integration suggests such events are, at most, extremely rare in vivo, and therefore are unlikely to drive oncogenesis or explain post-recovery detection of the virus.

genomics↗

bioRxiv2021

InterARTIC: an interactive web application for whole-genome nanopore sequencing analysis of SARS-CoV-2 and other viruses

MotivationInterARTIC is an interactive web application for the analysis of viral whole-genome sequencing (WGS) data generated on Oxford Nanopore Technologies (ONT) devices. A graphical interface enables users with no bioinformatics expertise to analyse WGS experiments and reconstruct consensus genome sequences from individual isolates of viruses, such as SARS-CoV-2. InterARTIC is intended to facilitate widespread adoption and standardisation of ONT sequencing for viral surveillance and molecular epidemiology. Worked exampleWe demonstrate the use of InterARTIC for the analysis of ONT viral WGS data from SARS-CoV-2 and Ebola virus, using a laptop computer or the internal computer on an ONT GridION sequencing device. We showcase the intuitive graphical interface, workflow customisation capabilities and job-scheduling system that facilitate execution of small- and large-scale WGS projects on any common virus. ImplementationInterARTIC is a free, open-source web application implemented in Python. The application can be downloaded as a set of pre-compiled binaries that are compatible with all common Ubuntu distributions, or built from source. For further details please visit: https://github.com/Psy-Fer/interARTIC/.

bioinformatics↗

bioRxiv2021

Advancing quality-control for NGS measurement of actionable mutations in circulating tumor DNA

The primary objective of the FDA-led Sequencing and Quality Control Phase 2 (SEQC2) project is to develop standard analysis protocols and quality control metrics for use in DNA testing to enhance scientific research and precision medicine. This study reports a targeted next generation sequencing (NGS) method that enables more accurate detection of actionable mutations in circulating tumor DNA (ctDNA) clinical specimens. This advancement was enabled by designing a synthetic internal standard spike-in for each actionable mutation target, suitable for use in NGS following hybrid-capture enrichment and unique molecular index (UMI) or non-UMI library preparation. When mixed with contrived ctDNA reference samples, internal standards enabled calculation of technical error rate, limit of blank, and limit of detection for each variant at each nucleotide position, in each sample. True positive mutations with variant allele fraction too low for detection by current practice were detected with this method, thereby increasing sensitivity.

genomics↗

bioRxiv2021

Two transcriptionally distinct pathways drive female development in a reptile with both genetic and temperature dependent sex determination

How temperature determines sex remains unknown. A recent hypothesis proposes that conserved cellular mechanisms (calcium and redox; CaRe status) sense temperature and identify genes and regulatory pathways likely to be involved in driving sexual development. We take advantage of the unique sex determining system of the model organism, Pogona vitticeps, to assess predictions of this hypothesis. P. vitticeps has ZZ male: ZW female sex chromosomes whose influence can be overridden in genetic males by high temperatures, causing male-to-female sex reversal. We compare a developmental transcriptome series of ZWf females and temperature sex reversed ZZf females. We demonstrate that early developmental cascades differ dramatically between genetically driven and thermally driven females, later converging to produce a common outcome (ovaries). We show that genes proposed as regulators of thermosensitive sex determination play a role in temperature sex reversal. Our study greatly advances the search for the mechanisms by which temperature determines sex. Author SummaryIn many reptiles and fish, environment can determine, or influence, the sex of developing embryos. How this happens at a molecular level that has eluded resolution for half a century of intensive research. We studied the bearded dragon, a lizard that has sex chromosomes (ZZ male and ZW female), but in which that temperature can override ZZ sex chromosomes to cause male to female sex reversal. This provides an unparalleled opportunity to disentangle, in the same species, the biochemical pathways required to make a female by these two different routes. We sequenced the transcriptomes of gonads from developing ZZ reversed and normal ZW dragon embryos and discovered that different sets of genes are active in ovary development driven by genotype or temperature. Females whose sex was initiated by temperature showed a transcriptional profile consistent with the recently-proposed Calcium-Redox hypotheses of cellular temperature sensing. These findings are an important for understanding how the environment influences the development of sex, and more generally how the environment can epigenetically modify the action of genes.

genetics↗

bioRxiv2020

DNA methylation is required to maintain DNA replication timing precision and 3D genome integrity

DNA replication timing and three-dimensional (3D) genome organisation occur across large domains associated with distinct epigenome patterns to functionally compartmentalise genome regulation. However, it is still unclear if alternations in the epigenome, in particular cancer-related DNA hypomethylation, can directly result in alterations to cancer higher order genome architecture. Here, we use Hi-C and single cell Repli-Seq, in the colorectal cancer DNMT1 and DNMT3B DNA methyltransferases double knockout model, to determine the impact of DNA hypomethylation on replication timing and 3D genome organisation. First, we find that the hypomethylated cells show a striking loss of replication timing precision with gain of cell-to-cell replication timing heterogeneity and loss of 3D genome compartmentalisation. Second, hypomethylated regions that undergo a large change in replication timing also show loss of allelic replication timing, including at cancer-related genes. Finally, we observe the formation of broad ectopic H3K4me3-H3K9me3 domains across hypomethylated regions where late replication is maintained, that potentially prevent aberrant transcription and loss of genome organisation after DNA demethylation. Together, our results highlight a previously underappreciated role for DNA methylation in maintenance of 3D genome architecture.

molecular biology↗

bioRxiv2020

Analytical validity of nanopore sequencing for rapid SARS-CoV-2 genome analysis

Viral whole-genome sequencing (WGS) provides critical insight into the transmission and evolution of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Long-read sequencing devices from Oxford Nanopore Technologies (ONT) promise significant improvements in turnaround time, portability and cost, compared to established short-read sequencing platforms for viral WGS (e.g., Illumina). However, adoption of ONT sequencing for SARS-CoV-2 surveillance has been limited due to common concerns around sequencing accuracy. To address this, we performed viral WGS with ONT and Illumina platforms on 157 matched SARS-CoV-2-positive patient specimens and synthetic RNA controls, enabling rigorous evaluation of analytical performance. Despite the elevated error rates observed in ONT sequencing reads, highly accurate consensus-level sequence determination was achieved, with single nucleotide variants (SNVs) detected at >99% sensitivity and >99% precision above a minimum ~60-fold coverage depth, thereby ensuring suitability for SARS-CoV-2 genome analysis. ONT sequencing also identified a surprising diversity of structural variation within SARS-CoV-2 specimens that were supported by evidence from short-read sequencing on matched samples. However, ONT sequencing failed to accurately detect short indels and variants at low read-count frequencies. This systematic evaluation of analytical performance for SARS-CoV-2 WGS will facilitate widespread adoption of ONT sequencing within local, national and international COVID-19 public health initiatives.

genomics↗

bioRxiv2020

Chimeric synthetic reference standards enable cross-validation of positive and negative controls in SARS-CoV-2 molecular tests.

DNA synthesis in vitro has enabled the rapid production of reference standards. These are used as controls, and allow measurement and improvement of the accuracy and quality of diagnostic tests. Current reference standards typically represent target genetic material, and act only as positive controls to assess test sensitivity. However, negative controls are also required to evaluate test specificity. Using a pair of chimeric A/B RNA standards, this allowed incorporation of positive and negative controls into diagnostic testing for the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). The chimeric standards constituted target regions for RT-PCR primer/probe sets that are joined in tandem across two separate synthetic molecules. Accordingly, a target region that is present in standard A provides a positive control, whilst being absent in standard B, thereby providing a negative control. This design enables cross-validation of positive and negative controls between the paired standards in the same reaction, with identical conditions. This enables control and test failures to be distinguished, increasing confidence in the accuracy of results. The chimeric A/B standards were assessed using the US Centers for Disease Control real-time RT-PCR protocol, and showed results congruent with other commercial controls in detecting SARS CoV-2 in patient samples. This chimeric reference standard design approach offers extensive flexibility, allowing representation of diverse genetic features and distantly related sequences, even from different organisms.

molecular biology↗

bioRxiv2018

Chiral DNA sequences as commutable reference standards for clinical genomics

Chirality is a geometric property describing any object that is inequivalent to a mirror image of itself. Due to its 5-3 directionality, a DNA sequence is distinct from a mirrored sequence arranged in reverse nucleotide order, and is therefore chiral. A given sequence and its opposing chiral partner sequence share many properties, such as nucleotide composition and sequence entropy. Here we demonstrate that chiral DNA sequence pairs also perform equivalently during molecular and bioinformatic techniques that underpin modern genetic analysis, including PCR amplification, hybridization, whole-genome, target-enriched and nanopore sequencing, sequence alignment and variant detection. Given these shared properties, synthetic DNA sequences that directly mirror clinically relevant and/or analytically challenging regions of the human genome are ideal reference standards for clinical genomics. We show how the addition of chiral DNA standards to patient tumor samples can prevent false-positive and false-negative mutation detection and, thereby, improve diagnosis. Accordingly, we propose that chiral DNA standards can fulfill the unmet need for commutable internal reference standards in precision medicine.

genomics↗

bioRxiv2017

Universal Alternative Splicing Of Noncoding Exons

The human transcriptome is so large, diverse and dynamic that, even after a decade of investigation by RNA sequencing (RNA-Seq), we are yet to resolve its true dimensions. RNA-Seq suffers from an expression-dependent bias that impedes characterization of low-abundance transcripts. We performed targeted single-molecule and short-read RNA-Seq to survey the transcriptional landscape of a single human chromosome (Hsa21) at unprecedented resolution. Our analysis reaches the lower limits of the transcriptome, identifying a fundamental distinction between protein-coding and noncoding gene content: almost every noncoding exon undergoes alternative splicing, producing a seemingly limitless variety of isoforms. Analysis of syntenic regions of the mouse genome shows that few noncoding exons are shared between human and mouse, yet human splicing profiles are recapitulated on Hsa21 in mouse cells, indicative of regulation by a deeply conserved splicing code. We propose that noncoding exons are functionally modular, with alternative splicing generating an enormous repertoire of potential regulatory RNAs and a rich transcriptional reservoir for gene evolution.

genomics↗