Dataset Information

Dynamic LTR retrotransposon transcriptome landscape in septic shock patients.

ABSTRACT: BACKGROUND:Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. Numerous studies have explored the complex and dynamic transcriptome modulations observed in sepsis patients, but a large fraction of the transcriptome remains unexplored. This fraction could provide information to better understand sepsis pathophysiology. Multiple levels of interaction between human endogenous retroviruses (HERV) and the immune response have led us to hypothesize that sepsis is associated with HERV transcription and that HERVs may contribute to a signature among septic patients allowing stratification and personalized management. METHODS:We used a high-density microarray and RT-qPCR to evaluate the HERV and Mammalian Apparent Long Terminal Repeat retrotransposons (MaLR) transcriptome in a pilot study that included 20 selected septic shock patients, stratified on mHLA-DR expression, with samples collected on day 1 and day 3 after inclusion. We validated the results in an unselected, independent cohort that included 100 septic shock patients on day 3 after inclusion. We compared septic shock patients, according to their immune status, to describe the transcriptional HERV/MaLR and conventional gene expression. For differential expression analyses, moderated t tests were performed and Wilcoxon signed-rank tests were used to analyze RT-qPCR results. RESULTS:We showed that 6.9% of the HERV/MaLR repertoire was transcribed in the whole blood, and septic shock was associated with an early modulation of a few thousand of these loci, in comparison to healthy volunteers. We provided evidence that a subset of HERV/MaLR and conventional genes were differentially expressed in septic shock patients, according to their immune status, using monocyte HLA-DR (mHLA-DR) expression as a proxy. A group of 193 differentially expressed HERV/MaLR probesets, tested in an independent septic shock cohort, identified two groups of patients with different immune status and severity features. CONCLUSION:We demonstrated that a large, unexplored part of our genome, which codes for HERV/MaLR, may be linked to the host immune response. The identified set of HERV/MaLR probesets should be evaluated on a large scale to assess the relevance of these loci in the stratification of septic shock patients. This may help to address the heterogeneity of these patients.

SUBMITTER: Mommert M

PROVIDER: S-EPMC7081582 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Dynamic LTR retrotransposon transcriptome landscape in septic shock patients.

Mommert Marine M Tabone Olivier O Guichard Audrey A Oriol Guy G Cerrato Elisabeth E Denizot Mélanie M Cheynet Valérie V Pachot Alexandre A Lepape Alain A Monneret Guillaume G Venet Fabienne F Brengel-Pesce Karen K Textoris Julien J Mallet François F

Critical care (London, England) 20200318 1

<h4>Background</h4>Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. Numerous studies have explored the complex and dynamic transcriptome modulations observed in sepsis patients, but a large fraction of the transcriptome remains unexplored. This fraction could provide information to better understand sepsis pathophysiology. Multiple levels of interaction between human endogenous retroviruses (HERV) and the immune response have led us t ...[more]

PMID: 32188504

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Project description:Background: Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. To date, no biomarker has shown sufficient evidence and ease of application in clinical routine to monitor the complexity of the sepsis-related immune alterations. Multiple levels of interaction of human endogenous retroviruses (HERVs) with the immune response led us to hypothesize that they may be relevant candidates both to contribute to the physiopathology of sepsis and to be part of a molecular signature. In this study, we used a recently described high-density microarray which allows exploring HERVs/MaLRs transcriptome in septic shock patients. Results: About 6.9% of the HERVs/MalRs repertoire is transcribed in whole blood. Concerning the functionality of LTRs, the majority of LTRs are silent (62.9%), 7.5% of LTRs present a putative constitutive promoter or polyA functions, while 20.4% of them may shift from silent to active. Evidence was given that a subset of HERVs/MaLRs and genes were modulated in septic shock patients according to the monocyte HLA-DR (mHLA-DR) expression level measured by flow cytometry, as a proxy of immunosuppression. We then identified a large signature consisting of 193 differentially expressed HERVs/MaLRs probesets further reduced to a smaller 10 HERVs/MaLRs signature. Both signatures, validated in an independent septic shock cohort, identified two groups of patients with different severity features including clinical criteria and the CD74 and CX3CR1 sepsis severity molecular markers. Conclusion: This microarray-based approach unveiled the expression of about 87,912 distinct HERV probesets and identified 764 putative promoter LTRs and 642 putative polyA LTRs in whole blood. HERV/MaLR expression was shown to be tightly modulated in septic shock patients according to mHLA-DR expression. We identified a set of potential molecular biomarkers in septic shock patients partially overlapping immunosuppression (mHLA-DR), and the risk of Health Care associated Infections (HAI) (CD74 ratio), complementary to existing molecular markers of a sepsis patients stratification. We identified a HERV/MaLR signature discriminating patients based on their immunosuppression state and severity.

Project description:BackgroundLong terminal repeat retrotransposons (LTR elements) are ubiquitous Eukaryotic TEs that transpose through RNA intermediates. Accounting for significant proportion of many plant genomes, LTR elements have been well established as one of the major forces underlying the evolution of plant genome size, structure and function. The accessibility of more than 40% of genomic sequences of the model legume Medicago truncatula (Mt) has made the comprehensive study of its LTR elements possible.ResultsWe use a newly developed tool LTR_FINDER to identify LTR retrotransposons in the Mt genome and detect 526 full-length elements as well as a great number of copies related to them. These elements constitute about 9.6% of currently available genomic sequences. They are classified into 85 families of which 64 are reported for the first time. The majority of the LTR retrotransposons belong to either Copia or Gypsy superfamily and the others are categorized as TRIMs or LARDs by their length. We find that the copy-number of Copia-like families is 3 times more than that of Gypsy-like ones but the latter contribute more to the genome. The analysis of PBS and protein-coding domain structure of the LTR families reveals that they tend to use only 4-5 types of tRNAs and many families have quite conservative ORFs besides known TE domains. For several important families, we describe in detail their abundance, conservation, insertion time and structure. We investigate the amplification-deletion pattern of the elements and find that the detectable full-length elements are relatively young and most of them were inserted within the last 0.52 MY. We also estimate that more than ten million bp of the Mt genomic sequences have been removed by the deletion of LTR elements and the removal of the full-length structures in Mt has been more rapid than in rice.ConclusionThis report is the first comprehensive description and analysis of LTR retrotransposons in the Mt genome. Many important novel LTR families were discovered and their evolution is elucidated. Our results may outline the LTR retrotransposon landscape of the model legume.

Project description:BackgroundHuman Endogenous Retroviruses (HERVs) and Mammalian apparent LTR-retrotransposons (MaLRs) represent the 8% of our genome and are distributed among our 46 chromosomes. These LTR-retrotransposons are thought to be essentially silent except in cancer, autoimmunity and placental development. Their Long Terminal Repeats (LTRs) constitute putative promoter or polyA regulatory sequences. In this study, we used a recently described high-density microarray which can be used to study HERV/MaLR transcriptome including 353,994 HERV/MaLR loci and 1559 immunity-related genes.ResultsWe described, for the first time, the HERV transcriptome in peripheral blood mononuclear cells (PBMCs) using a cellular model mimicking inflammatory response and monocyte anergy observed after septic shock. About 5.6% of the HERV/MaLR repertoire is transcribed in PBMCs. Roughly one-tenth [5.7-13.1%] of LTRs exhibit a putative constitutive promoter or polyA function while one-quarter [19.5-27.6%] may shift from silent to active. Evidence was given that some HERVs/MaLRs and genes may share similar regulation control under lipopolysaccharide (LPS) stimulation conditions. Stimulus-dependent response confirms that HERV expression is tightly regulated in PBMCs. Altogether, these observations make it possible to integrate 62 HERVs/MaLRs and 26 genes in 11 canonical pathways and suggest a link between HERV expression and immune response. The transcriptional modulation of HERVs located close to genes such as OAS2/3 and IFI44/IFI44L or at a great distance from genes was discussed.ConclusionThis microarray-based approach revealed the expression of about 47,466 distinct HERV loci and identified 951 putative promoter LTRs and 744 putative polyA LTRs in PBMCs. HERV/MaLR expression was shown to be tightly modulated under several stimuli including high-dose and low-dose LPS and Interferon-γ (IFN-γ). HERV incorporation at the crossroads of immune response pathways paves the way for further functional studies and analyses of the HERV transcriptome in altered immune responses in vivo such as in sepsis.

Project description:BACKGROUND:As early and appropriate care of severe septic patients is associated with better outcome, understanding of the very first events in the disease process is needed. Pan-genomic analyses offer an interesting opportunity to study global genomic response within the very first hours after sepsis. The objective of this study was to investigate the systemic genomic response in severe intensive care unit (ICU) patients and determine whether patterns of gene expression could be associated with clinical severity evaluated by the severity score. METHODS:Twenty-eight ICU patients were enrolled at the onset of septic shock. Blood samples were collected within 30 min and 24 and 48 h after shock and genomic response was evaluated using microarrays. The genome-wide expression pattern of blood leukocytes was sequentially compared to healthy volunteers and after stratification based on Simplified Acute Physiology Score II (SAPSII) score to identify potential mechanisms of dysregulation. RESULTS:Septic shock induces a global reprogramming of the whole leukocyte transcriptome affecting multiple functions and pathways (>71% of the whole genome was modified). Most altered pathways were not significantly different between SAPSII-high and SAPSII-low groups of patients. However, the magnitude and the duration of these alterations were different between these two groups. Importantly, we observed that the more severe patients did not exhibit the strongest modulation. This indicates that some regulation mechanisms leading to recovery seem to take place at the early stage. CONCLUSIONS:In conclusion, both pro- and anti-inflammatory processes, measured at the transcriptomic level, are induced within the very first hours after septic shock. Interestingly, the more severe patients did not exhibit the strongest modulation. This highlights that not only the responses mechanisms by themselves but mainly their early and appropriate regulation are crucial for patient recovery. This reinforces the idea that an immediate and tailored aggressive care of patients, aimed at restoring an appropriately regulated immune response, may have a beneficial impact on the outcome.

Dataset Information

Dynamic LTR retrotransposon transcriptome landscape in septic shock patients.

Publications

Dynamic LTR retrotransposon transcriptome landscape in septic shock patients.

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