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Transcriptomic profiling of peripheral blood mononuclear cells from healthy individuals

ABSTRACT: Substantial effort is currently devoted to identifying cancer-associated alterations using genomics. Here, we show that standard blood collection procedures rapidly change the transcriptional and post-transcriptional landscapes of hematopoietic cells, resulting in biased activation of specific biological pathways, up-regulation of pseudogenes, antisense RNAs, and unannotated coding isoforms, and RNA surveillance inhibition. Affected genes include common mutational targets and thousands of other genes participating in processes such as chromatin modification, RNA splicing, T and B cell activation, and NF-κB signaling. The majority of published leukemic transcriptomes exhibit signals of this incubation-induced dysregulation, explaining up to 40% of differences in gene expression and alternative splicing between leukemias and reference normal transcriptomes. The effects of sample processing are particularly evident in pan-cancer analyses. We provide biomarkers that detect prolonged incubation of individual samples, and show that keeping blood on ice markedly reduces changes to the transcriptome. In addition to highlighting the potentially confounding effects of technical artifacts in cancer genomics data, our study emphasizes the need to survey the diversity of normal as well as neoplastic cells when characterizing tumors. This study is complemented by GSE61410: transcriptomic profiling of bone marrow cells from healthy individuals.

ORGANISM(S): Homo sapiens

PROVIDER: GSE58335 | GEO | 2014/10/27

SECONDARY ACCESSION(S): PRJNA252189

REPOSITORIES: GEO

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Transcriptomic profiling of peripheral blood mononuclear cells from healthy individuals

Project description:Substantial effort is currently devoted to identifying cancer-associated alterations using genomics. Here, we show that standard blood collection procedures rapidly change the transcriptional and post-transcriptional landscapes of hematopoietic cells, resulting in biased activation of specific biological pathways, up-regulation of pseudogenes, antisense RNAs, and unannotated coding isoforms, and RNA surveillance inhibition. Affected genes include common mutational targets and thousands of other genes participating in processes such as chromatin modification, RNA splicing, T and B cell activation, and NF-κB signaling. The majority of published leukemic transcriptomes exhibit signals of this incubation-induced dysregulation, explaining up to 40% of differences in gene expression and alternative splicing between leukemias and reference normal transcriptomes. The effects of sample processing are particularly evident in pan-cancer analyses. We provide biomarkers that detect prolonged incubation of individual samples, and show that keeping blood on ice markedly reduces changes to the transcriptome. In addition to highlighting the potentially confounding effects of technical artifacts in cancer genomics data, our study emphasizes the need to survey the diversity of normal as well as neoplastic cells when characterizing tumors. This study is complemented by GSE61410: transcriptomic profiling of bone marrow cells from healthy individuals. Peripheral blood mononuclear cells (PBMCs) were isolated from four healthy individuals, following an ex vivo incubation of variable length at either room temperature or on ice. RNA transcriptomes were measured using the Illumina HiSeq.

2014-10-27 | E-GEOD-58335 | biostudies-arrayexpress

Long-read cDNA sequencing identifies functional pseudogenes in the human transcriptome

Project description:Pseudogenes are gene copies presumed to mainly be functionless relics of evolution due to acquired deleterious mutations or transcriptional silencing. When transcribed, pseudogenes may encode proteins or enact RNA-intrinsic regulatory mechanisms. However, the extent, characteristics and functional relevance of the human pseudogene transcriptome are unclear. Short-read sequencing platforms have limited power to resolve and accurately quantify pseudogene transcripts owing to the high sequence similarity of pseudogenes and their parent genes. Using deep full-length PacBio cDNA sequencing of normal human tissues and cancer cell lines, we identify here hundreds of novel transcribed pseudogenes. Pseudogene transcripts are expressed in tissue-specific patterns, exhibit complex splicing patterns and contribute to the coding sequences of known genes. We survey pseudogene transcripts encoding intact open reading frames (ORFs), representing potential unannotated protein-coding genes, and demonstrate their efficient translation in cultured cells. To assess the impact of noncoding pseudogenes on the cellular transcriptome, we delete the nucleus-enriched pseudogene PDCL3P4 transcript from HAP1 cells and observe hundreds of perturbed genes. This study highlights pseudogenes as a complex and dynamic component of the transcriptional landscape underpinning human biology and disease.

2021-04-26 | GSE160383 | GEO

Transcriptome sequencing to systematically detect trans-splicing in human embryonic stem cells

Project description:Trans-splicing occurs post-transcriptionally and generates transcripts that are orderly inconsistent with their corresponding DNA templates. Until recently only exceedingly rare trans-splicing events have been experimentally characterized in the mammalian transcriptomes. Although hundreds to thousands of trans-spliced RNA candidates have been nominated by bioinformatics- or NGS (next-generation sequencing)-based approaches, these candidates unavoidably suffered from potential false positives arising from genetic rearrangement events or in vitro artifacts. Here we develop a pipeline (TSscan) based on NGS transcriptome data to identify trans-splicing in human embryonic stem cells (ESCs). TSscan integrates RNA sequencing data derived from different NGS platforms (i.e., Roche 454, SOLiD, and Illumina) and different human ESC lines (i.e., H1 and H9) as well as several in silico filters to minimize these two types of potential false positives. Our result shows that a tremendous amount of apparent experimental artifacts are indeed present in NGS data, which may be the most major false positives of trans-splicing detection. TSscan totally identified 10 trans-spliced RNA candidates in human ESCs, four of which are experimentally validated to be true. Further experiments reveal that these four events represent differential expression during the transition of pluripotent status to differentiate statuses. Especially, we observe that one event (the trans-spliced isoform of NCRMS), which is also a large intergenic non-coding RNA, tends to be specifically transcribed in ESCs and induced pluripotent stem cells and can conspicuously affect the pluripotency maintenance of ESCs. As far as we know, TSscan is the first pipeline for systematic identification of trans-splicing that utilizes NGS data in the human transcriptome, opening up an important class of post-transcriptional events for comprehensive characterization. human embryonic stem cell H9

2014-02-03 | E-GEOD-30557 | biostudies-arrayexpress

Single cell RNA-seq data of human hESCs comparing experiments with cDNA library equalization

Project description:Considerable effort has been devoted to refining experimental protocols having reduced levels of technical variability and artifacts in single-cell RNA-sequencing data (scRNA-seq). We here present evidence that equalizing the concentration of cDNA libraries prior to pooling, a step not consistently performed in single-cell experiments, improves gene detection rates, enhances biological signals, and reduces technical artifacts in scRNA-seq data. In this submission the original single-cell cDNA is from GSE75748 cells labelled EC2 and TB2 in which the cDNA was not equalized prior to library preparation. We performed a set of experiments with the equalization step and provide three count matrices - 1) EQ (equalized cDNA prior to pooling in equal amounts); 2) EQ Vary (same as EQ but pooled at unequal amounts); 3) EQ-75% (equalized cDNA and pooled equally, sequeced to lower total depth).

2021-11-03 | GSE156494 | GEO

Large scale and significant expression from pseudogenes in Sodalis glossinidius - a facultative endosymbiont C4PR_LIV

Project description:The majority of bacterial genomes have high coding efficiencies, but there are an few genomes of the intracellular bacteria that have low gene density. The genome of the endosymbiont Sodalis glossinidius contains almost 50% pseudogenes containing mutations that putatively silence them at the genomic level. We have applied multiple omic strategies: combining single molecule DNA-sequencing and annotation; stranded RNA-sequencing and proteome analysis to better understand the transcriptional and translational landscape of Sodalis pseudogenes, and potential mechanisms for their control. Between 53% and 74% of the Sodalis transcriptome remains active in cell-free culture. Mean sense transcription from Coding Domain Sequences (CDS) is four-times greater than that from pseudogenes. Core-genome analysis of six Illumina sequenced Sodalis isolates from different host Glossina species shows pseudogenes make up ~40% of the 2,729 genes in the core genome, suggesting are stable and/or Sodalis is a recent introduction across the Glossina genus as a facultative symbiont. These data further shed light on the importance of transcriptional and translational control in deciphering host-microbe interactions, and demonstrate that pseudogenes are more complex than a simple degrading DNA sequence. For this reason, we show that combining genomics, transcriptomics and proteomics represents an important resource for studying prokaryotic genomes with a view to elucidating evolutionary adaptation to novel environmental niches.

2020-05-26 | PXD007068 | Pride

Preserving biological heterogeneity with personalized genomics batch correction

Project description:Motivation: Sample source, procurement process, and other technical variations introduce batch effects into genomics data. Algorithms to remove these artifacts enhance differences between known biological covariates, but also carry potential concern of removing intra-group biological heterogeneity and thus any personalized genomic signatures. As a result, accurate identification of novel subtypes from batch corrected genomics data is challenging using standard algorithms designed to remove batch effects for class comparison analyses. Nor can batch effects be corrected reliably in future applications of genomics-based clinical tests, in which the biological groups are by definition unknown a priori. Results: Therefore, we introduce new algorithm, personalized-SVA (pSVA), blind to biological covariates corrected technical artifacts while retaining biological heterogeneity in genomic data. This algorithm facilitated accurate subtype identification in head and neck cancer from gene expression data in both formalin fixed and frozen samples. When applied to predict HPV status, pSVA improved cross- study validation even if the sample batches were highly confounded with HPV status in the training set. Availability: All analyses were performed using R version 2.15.0. The code and data used to generate the results of this manuscript is available from https://sourceforge.net/projects/psva.

2016-12-12 | GSE53355 | GEO

Positive natural selection of N6-methyladenosine on the RNAs of processed pseudogenes

Project description:Background: Canonical Nonsense Mediated Decay (NMD) is an important splicing-dependent process for mRNA surveillance in mammals. However, processed pseudogenes are not able to trigger NMD due to their lack of introns. It is largely unknown whether they have evolved other surveillance mechanisms. Results: Here, we find that the RNAs of pseudogenes, especially processed pseudogenes, have dramatically higher m6A levels than their cognate protein-coding genes, associated with de novo m6A peaks and motifs in human cells. Furthermore, pseudogenes have rapidly accumulated m6A motifs during evolution. The m6A sites of pseudogenes are evolutionarily younger than neutral sites and their m6A levels are increasing, supporting the idea that m6A on the RNAs of pseudogenes is under positive selection. We then find that the m6A RNA modification of processed, rather than unprocessed, pseudogenes promotes cytosolic RNA degradation and attenuates interference with the RNAs of their cognate protein-coding genes. We experimentally validate the m6A RNA modification of two processed pseudogenes, DSTNP2 and NAP1L4P1, which promotes the RNA degradation of both pseudogenes and their cognate protein-coding genes DSTN and NAP1L4. In addition, the m6A of DSTNP2 regulation of DSTN is partially dependent on the miRNA miR-362-5p. Conclusions: Our discovery reveals a novel evolutionary role of m6A RNA modification in cleaning up the unnecessary processed pseudogene transcripts to attenuate their interfering with the regulatory network of proteincoding genes.

2021-05-27 | GSE172219 | GEO

Differentially regulated splice variants and systems biology analysis of Kaposi's Sarcoma-associated Herpesvirus-infected lymphatic endothelial cells

Project description:Alternative RNA splicing greatly increases proteome diversity, and the possibility of studying genome-wide alternative splicing (AS) events becomes available with the advent of high-throughput genomics tools devoted to this issue. Kaposi’s sarcoma associated herpesvirus (KSHV) is the etiological agent of KS, a tumor of lymphatic endothelial cell (LEC) lineage, but little is known about the AS variations induced by KSHV. We analyzed KSHV-controlled AS using high-density microarrays capable of detecting all exons in the human genome. Splicing variants and altered exon-intron usage in infected LEC were found, and these correlated with protein domain modification. The different 3’ UTR used in new transcripts also help isoforms to escape microRNA-mediated surveillance. Exome-level analysis further revealed information that cannot be disclosed using classical gene-level profiling: a significant exon usage difference existed between LEC and CD34+ precursor cells, and KSHV infection resulted in LEC-to-precursor, dedifferentiation-like exon level reprogramming. Our results demonstrate the application of exon arrays in systems biology research, and suggest the regulatory effects of AS in endothelial cells are far more complex than previously observed. This extra layer of molecular diversity helps to account for various aspects of endothelial biology, KSHV life cycle and disease pathogenesis that until now have been unexplored. 5 samples were analyzed. 3 were KSHV infected lymphatic endothelial cells (LECs), and 2 were non-infected control samples.

2011-05-05 | E-GEOD-26341 | biostudies-arrayexpress