Project description:Alternative splicing contributes to transcriptomic complexity and plays a role in the regulation of cellular identity and function, but the correct assembly of transcripts of complex loci as well as their quantification based on short-read sequencing is non-trivial. Recent long-read sequencing methods such as those from ONT and PacBio overcome these problems by potentially sequencing full transcripts. The activation of brown adipose tissue e.g., by reduced ambient temperature (cold) exposure, positively affects metabolism by increasing energy expenditure and releasing endocrine factors and has been shown to involve specific alternative splicing events. Here we assessed important features of ONT long read sequencing protocols in relation to Illumina short read sequencing: (i) Alignment characteristics to the reference genome and transcriptome, (ii) Gene and transcript detection and quantification, (iii) Detection of differential gene and transcript expression events, (iv) Transcriptome reannotation and (v) Detection of differential transcript usage events. We find that ONT long-read sequencing is advantageous in terms of transcriptome reassembly, especially when the reads are enriched for full length reads. Illumina sequencing, due to the higher number of counts available, has a higher statistical power for calling differentiall expressed/used features, whereas long-read sequencing has a lower risk of calling false positive events due to the better ability to unambiguously map reads to transcripts. Finally we describe novel transcript isoforms in cold-activated murine iBAT reassembled from ONT long reads.
Project description:Alternative splicing contributes to transcriptomic complexity and plays a role in the regulation of cellular identity and function, but the correct assembly of transcripts of complex loci as well as their quantification based on short-read sequencing is non-trivial. Recent long-read sequencing methods such as those from ONT and PacBio overcome these problems by potentially sequencing full transcripts. The activation of brown adipose tissue e.g., by reduced ambient temperature (cold) exposure, positively affects metabolism by increasing energy expenditure and releasing endocrine factors and has been shown to involve specific alternative splicing events. Here we assessed important features of ONT long read sequencing protocols in relation to Illumina short read sequencing: (i) Alignment characteristics to the reference genome and transcriptome, (ii) Gene and transcript detection and quantification, (iii) Detection of differential gene and transcript expression events, (iv) Transcriptome reannotation and (v) Detection of differential transcript usage events. We find that ONT long-read sequencing is advantageous in terms of transcriptome reassembly, especially when the reads are enriched for full length reads. Illumina sequencing, due to the higher number of counts available, has a higher statistical power for calling differentiall expressed/used features, whereas long-read sequencing has a lower risk of calling false positive events due to the better ability to unambiguously map reads to transcripts. Finally we describe novel transcript isoforms in cold-activated murine iBAT reassembled from ONT long reads.
Project description:Sequencing was performed to assess the ability of Nanopore direct cDNA and native RNA sequencing to characterise human transcriptomes. Total RNA was extracted from either HAP1 or HEK293 cells, and the polyA+ fraction isolated using oligodT dynabeads. Libraries were prepared using Oxford Nanopore Technologies (ONT) kits according to manufacturers instructions. Samples were then sequenced on ONT R9.4 flow cells to generate fast5 raw reads in the ONT MinKNOW software. Fast5 reads were then base-called using the ONT Albacore software to generate Fastq reads.
Project description:Alternative splicing contributes to transcriptomic complexity and plays a role in the regulation of cellular identity and function, but the correct assembly of transcripts of complex loci as well as their quantification based on short-read sequencing is non-trivial. Recent long-read sequencing methods such as those from ONT and PacBio overcome these problems by potentially sequencing full transcripts. The activation of brown adipose tissue e.g., by reduced ambient temperature (cold) exposure, positively affects metabolism by increasing energy expenditure and releasing endocrine factors and has been shown to involve specific alternative splicing events. Here we assessed important features of ONT long read sequencing protocols in relation to Illumina short read sequencing: (i) Alignment characteristics to the reference genome and transcriptome, (ii) Gene and transcript detection and quantification, (iii) Detection of differential gene and transcript expression events, (iv) Transcriptome reannotation and (v) Detection of differential transcript usage events. We find that ONT long-read sequencing is advantageous in terms of transcriptome reassembly, especially when the reads are enriched for full length reads. Illumina sequencing, due to the higher number of counts available, has a higher statistical power for calling differentiall expressed/used features, whereas long-read sequencing has a lower risk of calling false positive events due to the better ability to unambiguously map reads to transcripts. Finally we describe novel transcript isoforms in cold-activated murine iBAT reassembled from ONT long reads.
Project description:Epitranscriptomics modifications constitute a gene expression checkpoint in all living organism including plants. Considering the relevance of nitrogen nutrition and metabolism for the correct plant growth and development, it can be hypothesized that epitranscriptome changes must regulate every biological process in plants including nitrogen nutrition. In the present work, the epritranscriptomics changes in maritime pine roots caused by ammonium nutrition have been monitored through direct RNA sequencing using Oxford Nanopore Technology. The main transcriptome responses to ammonium nutrition affected to transcripts involved in nitrogen and carbon metabolisms, defense response, hormone synthesis and signaling, and translation. Additionally to a global detection of epitranscriptomics marks, the m6A deposition and its dynamics have been identified, which seems to be important regulators of translation when compared with the proteomic profiles of the same samples. In this sense, the obtained results suggest that protein translation is finely regulated through the epitranscriptomics marks maybe through changes in mRNA polyA length, transcript amount and ribosome protein composition. The multiomics results in the present study suggest that the epitranscriptome must modulate the responses to development and environmental changes, including ammonium nutrition, through buffering, filtering and focusing the final products of the gene expression.
Project description:Transcriptional profiling of breast cell lines comparing breast cell line mixed reference with individual breast cell lines. Goal was to characterize breast cell line subtypes.
Project description:The transcriptome profiles of the model plant Arabidopsis thaliana have been extensively studied and charcaterised under different developmental and physiological conditions. However, most of these “RNA-sequencing” datasets have been generated using the sequencing of reverse-transcribed cDNAs from mRNAs that have a relatively short read length. Here, we performed direct RNA sequencing using the latest Oxford Nanopore Technology (ONT) with unusual read length. We demonstrate that the complexity of the A. thaliana transcriptomes has been under-estimated. The ONT direct RNA sequencing technology identified transcript isoforms at a vegetative (14 day old seedlings, stage 1.04) and a reproductive stage (stage 6.00-6) when 10% of the flowers had opened. In-house software called TrackCluster was used to determine alternative transcription initiation (ATI), possible alternative polyadenylation (APA), poly(A) length, alternative splicing (AS), and fusion transcripts. Tombo software was used to detect RNA base modifications. More than 38,500 novel transcript isoforms were identified, including six categories of fusion-transcripts which may result from differential RNA processing mechanisms. Fusion-transcripts are prone to mis-assembly by sequencing with short reads using next-generation-sequencing (NGS). These new transcript isoforms provide important additions to the annotated Arabidopsis genome. The power of ONT in detecting RNA modifications was demonstrated by characterisation of the modifications between mobile mRNAs and total mRNAs. The mobile mRNAs were enriched in m5C modifications, which is consistent with a recent finding that m5C modification in mRNAs is crucial for their long-distance movement. In summary, ONT direct RNA sequencing greatly enhances the identification of novel RNA transcript isoforms and RNA base modifications.
Project description:Rapidly increased studies by third-generation sequencing [Pacific Biosciences (Pacbio) and Oxford Nanopore Technologies (ONT)] have been used in all kinds of research areas. Among them, the plant full-length single-molecule transcriptome studies were most used by Pacbio while ONT was rarely used. Therefore, in this study, we developed ONT RNA-sequencing methods in plants. We performed a detailed evaluation of reads from Pacbio and Nanopore PCR cDNA (ONT Pc) sequencing in plants (Arabidopsis), including the characteristics of raw data and identification of transcripts. We aimed to provide a valuable reference for applications of ONT in plant transcriptome analysis.