Ontology highlight
ABSTRACT:
PROVIDER: PRJNA380045 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR5381740.fastq.gz | Fastqsanger.gz | |||
| SRR5381740_1.fastq.gz | Fastqsanger.gz | |||
| SRR5381740_2.fastq.gz | Fastqsanger.gz | |||
| SRR5381741.fastq.gz | Fastqsanger.gz | |||
| SRR5381742.fastq.gz | Fastqsanger.gz |
Items per page: 5 1 - 5 of 11 |
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Project description:We present GCparagon, a two-stage algorithm for computing and correcting GC biases in cell-free DNA (cfDNA) samples. The length of the highly fragmented cfDNAs and the number of GC bases are essential parameters in the calculations. Regions of low mappability, known reference genome assembly errors and regions surrounding assembly gaps are excluded from the bias computation. GCparagon outputs a bias matrix and an optional tagged BAM file with GC bias balance weights as alignment tags. Parallelization allows calculation of a GC bias estimate in less than 2 minutes per sample with between 99.0% and 99.9% of fragments already corrected. We propose that GCparagon can help standardize cfDNA applications and evaluate the impact of GC bias on algorithms used in the analysis of liquid biopsy data.
| EGAS00001006963 | EGA
Project description:Follicular T-helper (TFH) cells are essential for germinal center (GC) responses. TFH localization in GCs is controlled by chemo-guidance cues and antigen-specific adhesion. Here we define an antigen-independent, contact-dependent, adhesive guidance system for TFH cells. Unusual for amoeboid cell migration, the system is composed of transmembrane plexin B2 (PlxnB2) molecule that is highly expressed by GC B cells and its transmembrane binding partner semaphorin 4C (Sema4C) that is upregulated on TFH cells. Instead of effectuating repulsion as a ligand, Sema4C serves as the receptor to sense PlxnB2 and bias TFH migration inward at the GC edge to penetrate the GC territory. The absence of PlxnB2 from the GC or Sema4C from TFH cells causes TFH accumulation along the GC border, impairs TFH -B cell interactions and is associated with defective plasma cell production and affinity maturation. Therefore, Sema4C and PlxnB2 regulate GC TFH recruitment and function and optimal antibody responses.
2017-06-12 | GSE96819 | GEO
Project description:The genomes of many vertebrates show a characteristic variation in GC content. To explain its origin and evolution mainly three mechanisms have been proposed, selection for GC content, mutation bias and GC-biased gene conversion. At present the mechanism of GC-biased gene conversion, i.e. short-scale, unidirectional exchanges between homologous chromosomes in the neighborhood of recombination-initiating double-strand breaks in favor for GC nucleotides, is the most widely accepted hypothesis. We here suggest that DNA methylation also plays an important role in the evolution of GC content in vertebrate genomes. To test this hypothesis we investigated one mammalian (human; GSE30340) and one avian (chicken) genome. We used bisulfite sequencing to generate a whole-genome methylation map of chicken sperm. Human processed data files (spermdonor1, #reads>=1) were downloaded from the NGSmethDB database (http://bioinfo2.ugr.es/NGSmethDB/database.php). Inclusion of these methylation maps into a model of GC content evolution provided significant support for the impact of DNA methylation on the local equilibrium GC content. Moreover, two different estimates of equilibrium GC content, one which neglects and one which incorporates the impact of DNA methylation and the concomitant CpG hypermutability, give estimates that differ about 15% in both genomes, arguing for a strong impact of DNA methylation on the evolution of GC content. Thus, our results put forward that previous estimates of equilibrium GC content, which neglect the hypermutability of CpG dinucleotides, need to be reevaluated. Genomic DNA from chicken mature sperm was isolated, bisulfite converted and sequenced on a Illumina HiSeq instrument
2015-01-23 | E-GEOD-56639 | biostudies-arrayexpress
Project description:To characterize the rules governing exon recognition during splicing, we analyzed RNA-seq datasets and identified ~4,000 GC-rich and ~5,000 AT-rich exons, labelled GC-exons and AT-exons, respectively whose inclusion depends on different sets of splicing factors. We show that a high GC-load is associated with predicted RNA secondary structures at 5'ss and that GC-exons are dependent on U1 snRNP-associated proteins. Meanwhile, a high AT-load is associated with a large number of decoy splicing-related signals upstream exons such as the number of branchpoints and SF1- or U2AF65-binding sites and AT-exons are dependent on U2 snRNP-associated proteins. Nucleotide composition bias also influences local chromatin organization. Since the GC content of exons correlates with that of their hosting-genes, -isochores and – topologically-associated domains, we propose that regional nucleotide composition bias leaves a footprint locally, at the exon level, inducing, during splicing, constraints that are alleviated by the local chromatin organization and specific splicing factors.
2019-10-25 | GSE138397 | GEO
Project description:These are aligned paired-end reads from Illumina NovaSeq 6000 whole-genome sequencing of 4 cfDNA samples extracted from blood plasma (plasma-Seq). Three samples from patients with breast cancer, prostate cancer, or colorectal cancer and one sample from a healthy individual were aligned to GRCh38 (GCA_000001405.15_GRCh38_no_alt_plus_hs38d1_analysis_set). The observed GC bias is different in each of these cfDNA samples which leads to different average GC content per sample. This bias is corrected using the GCparagon commandline tool.
| EGAD00001010100 | EGA
Project description:The mechanisms involved in the maintenance of memory IgE responses are poorly understood, and the role played by germinal center (GC) IgE cells in these memory responses is particularly unclear. IgE B-cell differentiation is characterized by a transient GC phase, a bias towards the plasma cell (PC) fate, and dependence on sequential switching for the production of high-affinity IgE. We show here that IgE GC B cells are unfit to undergo the conventional GC differentiation program due to impaired B-cell receptor function and increased apoptosis. IgE GC cells fail to populate the GC light zone and are unable to contribute to the memory and long-lived PC compartments. Furthermore, we demonstrate that direct and sequential switching are linked to distinct B-cell differentiation fates: direct switching generates IgE GC cells, whereas sequential switching gives rise to IgE plasma cells. We propose a comprehensive model for the generation and memory of IgE responses.
2013-10-31 | GSE49033 | GEO
Project description:CRISPR-MIP replaces PCR and reveals GC and oversampling bias in pooled CRISPR screens
| PRJEB79143 | ENA
Project description:One clear hallmark of mammalian promoters is the presence of CpG islands (CGIs) at more than two thirds of genes whereas TATA boxes are only present at a minority of promoters. Using genome-wide approaches, we show that GC content and CGIs are major promoter elements in mammalian cells, able to govern open chromatin conformation and support paused transcription. First, we define three classes of promoters with distinct transcriptional directionality and pausing properties which correlate with their GC content. We further analyze the direct influence of GC content on nucleosome positioning and depletion, and show that CGIs correlate with nucleosome depletion both in vivo and in vitro. We also show that transcription is not essential for nucleosome exclusion but influences both a weak +1 and a well-positioned nucleosome at CGI borders. Altogether our data support the idea that CGIs have become an essential feature of promoter structure defining novel regulatory properties in mammals. Nucleosome density and positioning were studied by high-throughput sequencing of DNA previously treated with Mnase. In parallel, chIPseq for PolII and H3K27ac were performed in mouse and human with different conditions to assess a potential effect of transcription on nucleosomes properties. Sonicated genomic DNA has been sequenced to quantify and exclude sequencing bias in the largest CGIs regions studied in this article.
2012-06-11 | E-GEOD-38562 | biostudies-arrayexpress
Project description:One clear hallmark of mammalian promoters is the presence of CpG islands (CGIs) at more than two thirds of genes whereas TATA boxes are only present at a minority of promoters. Using genome-wide approaches, we show that GC content and CGIs are major promoter elements in mammalian cells, able to govern open chromatin conformation and support paused transcription. First, we define three classes of promoters with distinct transcriptional directionality and pausing properties which correlate with their GC content. We further analyze the direct influence of GC content on nucleosome positioning and depletion, and show that CGIs correlate with nucleosome depletion both in vivo and in vitro. We also show that transcription is not essential for nucleosome exclusion but influences both a weak +1 and a well-positioned nucleosome at CGI borders. Altogether our data support the idea that CGIs have become an essential feature of promoter structure defining novel regulatory properties in mammals. Nucleosome density and positioning were studied by high-throughput sequencing of DNA previously treated with Mnase. In parallel, ChIP-seq for PolII and H3K27ac were performed in mouse and human with different conditions to assess a potential effect of transcription on nucleosomes properties. To exclude a possible MNase digestion bias or sequencing artefact within CGIs, we performed additional controls such as nucleosome mapping using an alternative method based on DNA digestion by a chemical agent (phenanthroline) in human Raji B-cells.
2012-06-12 | E-GEOD-38564 | biostudies-arrayexpress