Identification of de novo LINE-1 (L1) retrotransposon integration sites in HeLa S3 cells by ATLAS-seq-neo
ABSTRACT: We used ATLAS-seq-neo to map the sites of integration of an engineered LINE-1 (L1) retrotransposon into the genome of HeLa S3 cells. In brief, we transfected cells with a plasmid-borne L1.3 element carrying a NeoR-based retrotransposition cassette. Cells were selected by G418 and used to prepare ATLAS-seq-neo libraries. Each sample corresponds to an independent transfection and pool of G418-resistant cells. ATLAS-seq-neo relies on the random mechanical fragmentation of the genomic DNA to ensure high-coverage, ligation of adapter sequences, suppression PCR-amplification of the 3' end L1 junction with its flanking genomic sequence, and Ion Torrent sequencing using single-end 400 bp read chemistry. The primer used for suppression PCR specifically targets the engineered element and not endogenous copies as in the original ATLAS-seq protocol (Philippe et al. eLife 2016).
Project description:We used ATLAS-seq-neo to map the sites of integration of an engineered LINE-1 (L1) retrotransposon into the genome of HeLa S3 cells. In brief, we transfected cells with a plasmid-borne L1.3 element carrying a neomycin-resistance-based retrotransposition cassette, as well as a hygromycin-resistance cassette on the plasmid backbone. For this set of experiments, cells were only selected for transfection (hygromycin) but not for retrotransposition (neomycin). Then we prepared ATLAS-seq-neo libraries. Each sample corresponds to an independent transfection and pool of hygromycin-resistant cells. ATLAS-seq-neo relies on the random mechanical fragmentation of the genomic DNA to ensure high-coverage, ligation of adapter sequences, suppression PCR-amplification of the 3' end L1 junction with its flanking genomic sequence, and Ion Torrent sequencing using single-end 400 bp read chemistry. The primer used for suppression PCR specifically targets the engineered element and not endogenous copies as in the original ATLAS-seq protocol (Philippe et al. eLife 2016). For some libraries, the linker-ligated genomic DNA was digested with BamHI, which cuts downstream of L1 polyA site in the plasmid backbone, to limit amplification from the plasmid and enrich for retrotransposition-mediated insertion events into the genomic DNA.
Project description:We used ATLAS-seq to comprehensively map the genomic location of LINE-1 elements belonging to the youngest and potentially polymorphic subfamily (L1HS-Ta). This was performed in a panel of 12 human primary or transformed cell lines (BJ, IMR90, MRC5, H1, K562, HCT116, HeLa S3, HepG2, MCF7, HEK-293, HEK-293T, 2102Ep). In brief, ATLAS-seq relies on the random mechanical fragmentation of the genomic DNA to ensure high-coverage, ligation of adapter sequences, suppression PCR-amplification of L1HS-Ta element junctions, and Ion Torrent sequencing using single-end 400 bp read chemistry. A notable aspect of ATLAS-seq is that we can obtain both L1 downstream and upstream junctions (3'- and 5'-ATLAS-seq libraries, respectively), for full-length L1 elements. Note that a 10-nt sample-specific barcode has been removed at the 5' end of the reads in the .fastq files upon demultiplexing. This was achieved using cutadapt v1.9.2.dev0 (with the following parameters: -e 0.1 -q 10 -m 25 -g <barcode_name>=^<barcode_sequence>)
Project description:We performed whole-exome sequencing of tumour bulks from opposite side of the neoplasm (A/B). From each we selected a panel of sub-clonal mutations and profiled multiple single tumour glands from the same neoplasm using high depth targeted re-sequencing. The aim was to infer tumour evolutionary dynamics and reconstruct the timeline of progression
Project description:Identifying miRNA-regulated genes is key to understanding miRNA function. However, many miRNA recognition elements (MREs) do not follow canonical seed base-pairing rules, making identification of bona fide targets challenging. Here, we apply an unbiased sequencing-based systems approach to characterize miR-522, a member of the oncogenic primate-specific chromosome 19 miRNA cluster, highly expressed in poorly differentiated cancers. To identify miRNA targets, we sequenced full-length transcripts captured by a biotinylated miRNA mimic (this dataset). Within these targets, mostly non-canonical MREs were identified by sequencing RNase-resistant fragments.
Project description:We investigated a panel of 21 genes by parallel sequencing on the Ion Torrent Personal Genome Machine platform. We sequenced 65 CRCs that were treated with cetuximab or panitumumab ( 37 samples were responsive and 28 were resistant).
Project description:To test whether the addition of a peptide nucleic acid (PNA) clamp, which binds WT KRAS at codon 12, can increase the efficacy of mutation detection for KRASG12D within a targeted NGS setting. We tested the effect of clamping the wild-type KRAS sequence in a reference standard (Tru-Q 7, 1.3% Tier from Horizon Diagnostics, Cambridge, UK) with a KRAS c.35G>A mutation (KRASG12D) at an allelic frequency (AF) of 1.3% assessed by digital droplet PCR (ddPCR). We then re-tested the PNA on circulating-free DNA from a patient harbouring a KRASG12D mutation (at an AF of 3.2%, determined by ddPCR). Multiple runs were conducted using 10, 5, 2.5 and 1ng of DNA input.
Project description:Murine Adult Stomach Small RNA Stomach samples were collected from adult mice. Small RNA was isolated from samples and cDNA libraries were generated for PGM sequencing. Sequences were aligned with Torrent Server tMap.
Project description:In vertebrates, DNA methylation-mediated repression of retrotransposons is essential for the maintenance of genomic integrity. In the current study, we developed a technique termed HT-TREBS (High-Throughput Targeted Repeat Element Bisulfite Sequencing). This technique is designed to measure the DNA methylation levels of individual loci of any repeat families with next-generation sequencing approaches. To test the feasibility of HT-TREBS, we analyzed the DNA methylation levels of the IAPLTR family using a set of 12 different genomic DNA isolated from the brain, liver and kidney of 4 one-week-old littermates of the mouse strain C57BL/6N. This technique has successfully generated the CpG methylation data of 5,233 loci common in all the samples, representing more than 80% of the individual loci of the five targeted subtypes of the IAPLTR family. According to the results, approximately 5% of the IAPLTR loci have less than 80% average CpG methylation levels with no genomic position preference. Further analyses of the IAPLTR loci also revealed the presence of extensive DNA methylation variations between different tissues and individuals. Overall, these data demonstrate the efficiency and robustness of the new technique, HT-TREBS, and also provide new insights regarding the genome-wide DNA methylation patterns of the IAPLTR repeat elements. High-throughput, single-base resolution, singlicate DNA methylation profiles of IAPLTR retrotransposons in the brain, liver , and kidney of four 1-week-old mouse littemates using the developed technique, HT-TREBS.
Project description:We evaluated whether targeted next-generation sequencing (NGS) using the Ion Torrent Personal Genome Sequencer of cfDNA could identify prognostic or predictive factors for overall survival (OS) or progression free survival (PFS) within a large cohort of patients with advanced lung adenocarcinoma enrolled in the GALAXY-1 trial.
Project description:The ligation step in RNA sequencing library generation is a known source of bias. We present the first comparison of the standard duplex adaptor protocol supplied by Life Technologies for use on the Ion Torrent PGM with an alternate single adaptor approach involving CircLigase (CircLig). We also investigate whether using the thermostable ligase Methanobacterium thermoautotrophicum RNA ligase K97A (Mth K97A) for the initial ligation step in the CircLigase protocol reduces bias. A pool of small RNA fragments of known composition was converted into a sequencing library using one of three protocols and sequenced on an Ion Torrent PGM. The single adaptor CircLigase-based approach significantly reduces, but does not eliminate, bias in Ion Torrent data. Using Mth K97A as part of the CircLig method does not further reduce bias.