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:Collection of 2 biological replicates of SMF-ONT performed in S2 and OSC cell lines. The footprinting protocol was adapted from Kleinendorst and Barzaghi et al., 2021 and optimised for long-read sequencing and high weight DNA extraction. In summary, 2.5 million intact nuclei per SMF reaction have been treated with successive incubation with GpC (M.CviPI) and CpG (M.SssI) methyltransferase enzymes. Footprinted DNA was extracted using the Quick-DNA HMW MagBead kit following the manufacturer protocol and using wide-bore tips. Nanopore ligation library (LSK109 or LSK114) preparation has been performed using 1µg of purified footprinted HWM DNA. Sequencing has been performed using GridION flow cells for the R9 chemistry (LSK109) and promethION flow cells for the R10 chemistry (LSK114). The data have been analysed using the SMF-ONT nextflow pipeline (https://git.embl.de/grp-krebs/nf-smfont) using custom methylation call models.
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:One ONT-ULK sequencing run from the kidney of a single male CDMR (Bathyergus suillus) sample used to make the mBatSui1.1.primary genome assembly as an evolutionary comparator to our telomere-to-telomere naked mole-rat genome assembly. Specifically, we assembled a CDMR from a wild-derived sample in South African cape and sequenced in Toronto, Canada, using PacBio HiFi (89 Gb, read N50 = 18 Kb) and ONT-ULK (55 Gb, read N50 = 43 Kb) reads (contig N50 = 33 Mb, Compleasm S = 99%, QV = 71.0). This accession stores the ONT-ULK data for this assembly.
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.