Article (Scientific journals)
Widespread and tissue-specific expression of endogenous retroelements in human somatic tissues
Larouche, Jean-David; Trofimov, Assya; Hesnard, Leslie et al.
2020In Genome Medicine, 12 (1)
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Abstract :
[en] Background: Endogenous retroelements (EREs) constitute about 42% of the human genome and have been implicated in common human diseases such as autoimmunity and cancer. The dominant paradigm holds that EREs are expressed in embryonic stem cells (ESCs) and germline cells but are repressed in differentiated somatic cells. Despite evidence that some EREs can be expressed at the RNA and protein levels in specific contexts, a system-level evaluation of their expression in human tissues is lacking. Methods: Using RNA sequencing data, we analyzed ERE expression in 32 human tissues and cell types, including medullary thymic epithelial cells (mTECs). A tissue specificity index was computed to identify tissue-restricted ERE families. We also analyzed the transcriptome of mTECs in wild-type and autoimmune regulator (AIRE)-deficient mice. Finally, we developed a proteogenomic workflow combining RNA sequencing and mass spectrometry (MS) in order to evaluate whether EREs might be translated and generate MHC I-associated peptides (MAP) in B-lymphoblastoid cell lines (B-LCL) from 16 individuals. Results: We report that all human tissues express EREs, but the breadth and magnitude of ERE expression are very heterogeneous from one tissue to another. ERE expression was particularly high in two MHC I-deficient tissues (ESCs and testis) and one MHC I-expressing tissue, mTECs. In mutant mice, we report that the exceptional expression of EREs in mTECs was AIRE-independent. MS analyses identified 103 non-redundant ERE-derived MAPs (ereMAPs) in B-LCLs. These ereMAPs preferentially derived from sense translation of intronic EREs. Notably, detailed analyses of their amino acid composition revealed that ERE-derived MAPs presented homology to viral MAPs. Conclusions: This study shows that ERE expression in somatic tissues is more pervasive and heterogeneous than anticipated. The high and diversified expression of EREs in mTECs and their ability to generate MAPs suggest that EREs may play an important role in the establishment of self-tolerance. The viral-like properties of ERE-derived MAPs suggest that those not expressed in mTECs can be highly immunogenic.
Disciplines :
Genetics & genetic processes
Author, co-author :
Larouche, Jean-David
Trofimov, Assya
Hesnard, Leslie
Ehx, Grégory  ;  Université de Liège - ULiège > I3-Hematology
Zhao, Qingchuan
Vincent, Krystel
Durette, Chantal
Gendron, Patrick
Laverdure, Jean-Philippe
Bonneil, Eric
Coté, Caroline
Lemieux, Sébastien
Thibault, Pierre
Perreault, Claude
More authors (4 more) Less
Language :
English
Title :
Widespread and tissue-specific expression of endogenous retroelements in human somatic tissues
Publication date :
2020
Journal title :
Genome Medicine
eISSN :
1756-994X
Publisher :
BioMed Central, United Kingdom
Volume :
12
Issue :
1
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 20 January 2021

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