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Kitsou K, Katzourakis A, Magiorkinis G. Limitations of current high-throughput sequencing technologies lead to biased expression estimates of endogenous retroviral elements. NAR Genom Bioinform 2024; 6:lqae081. [PMID: 38984066 PMCID: PMC11231582 DOI: 10.1093/nargab/lqae081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Revised: 04/09/2024] [Accepted: 06/27/2024] [Indexed: 07/11/2024] Open
Abstract
Human endogenous retroviruses (HERVs), the remnants of ancient germline retroviral integrations, comprise almost 8% of the human genome. The elucidation of their biological roles is hampered by our inability to link HERV mRNA and protein production with specific HERV loci. To solve the riddle of the integration-specific RNA expression of HERVs, several bioinformatics approaches have been proposed; however, no single process seems to yield optimal results due to the repetitiveness of HERV integrations. The performance of existing data-bioinformatics pipelines has been evaluated against real world datasets whose true expression profile is unknown, thus the accuracy of widely-used approaches remains unclear. Here, we simulated mRNA production from specific HERV integrations to evaluate second and third generation sequencing technologies along with widely used bioinformatic approaches to estimate the accuracy in describing integration-specific expression. We demonstrate that, while a HERV-family approach offers accurate results, per-integration analyses of HERV expression suffer from substantial expression bias, which is only partially mitigated by algorithms developed for calculating the per-integration HERV expression, and is more pronounced in recent integrations. Hence, this bias could erroneously result into biologically meaningful inferences. Finally, we demonstrate the merits of accurate long-read high-throughput sequencing technologies in the resolution of per-locus HERV expression.
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Affiliation(s)
- Konstantina Kitsou
- Department of Hygiene, Epidemiology and Medical Statistics, National and Kapodistrian University of Athens, Athens 11527, Greece
| | | | - Gkikas Magiorkinis
- Department of Hygiene, Epidemiology and Medical Statistics, National and Kapodistrian University of Athens, Athens 11527, Greece
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Adler GL, Le K, Fu Y, Kim WS. Human Endogenous Retroviruses in Neurodegenerative Diseases. Genes (Basel) 2024; 15:745. [PMID: 38927681 PMCID: PMC11202925 DOI: 10.3390/genes15060745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2024] [Revised: 05/25/2024] [Accepted: 06/04/2024] [Indexed: 06/28/2024] Open
Abstract
Human endogenous retroviruses (HERVs) are DNA transposable elements that have integrated into the human genome via an ancestral germline infection. The potential importance of HERVs is underscored by the fact that they comprise approximately 8% of the human genome. HERVs have been implicated in the pathogenesis of neurodegenerative diseases, a group of CNS diseases characterized by a progressive loss of structure and function of neurons, resulting in cell death and multiple physiological dysfunctions. Much evidence indicates that HERVs are initiators or drivers of neurodegenerative processes in multiple sclerosis and amyotrophic lateral sclerosis, and clinical trials have been designed to target HERVs. In recent years, the role of HERVs has been explored in other major neurodegenerative diseases, including frontotemporal dementia, Alzheimer's disease and Parkinson's disease, with some interesting discoveries. This review summarizes and evaluates the past and current research on HERVs in neurodegenerative diseases. It discusses the potential role of HERVs in disease manifestation and neurodegeneration. It critically reviews antiretroviral strategies used in the therapeutic intervention of neurodegenerative diseases.
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Affiliation(s)
- Gabrielle L. Adler
- Brain and Mind Centre, The University of Sydney, Sydney, NSW 2050, Australia
- School of Medical Sciences, The University of Sydney, Sydney, NSW 2050, Australia
| | - Kelvin Le
- Brain and Mind Centre, The University of Sydney, Sydney, NSW 2050, Australia
- School of Medical Sciences, The University of Sydney, Sydney, NSW 2050, Australia
| | - YuHong Fu
- Brain and Mind Centre, The University of Sydney, Sydney, NSW 2050, Australia
- School of Medical Sciences, The University of Sydney, Sydney, NSW 2050, Australia
| | - Woojin Scott Kim
- Brain and Mind Centre, The University of Sydney, Sydney, NSW 2050, Australia
- School of Medical Sciences, The University of Sydney, Sydney, NSW 2050, Australia
- School of Biomedical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
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da Silva AL, Guedes BLM, Santos SN, Correa GF, Nardy A, Nali LHDS, Bachi ALL, Romano CM. Beyond pathogens: the intriguing genetic legacy of endogenous retroviruses in host physiology. Front Cell Infect Microbiol 2024; 14:1379962. [PMID: 38655281 PMCID: PMC11035796 DOI: 10.3389/fcimb.2024.1379962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 03/22/2024] [Indexed: 04/26/2024] Open
Abstract
The notion that viruses played a crucial role in the evolution of life is not a new concept. However, more recent insights suggest that this perception might be even more expansive, highlighting the ongoing impact of viruses on host evolution. Endogenous retroviruses (ERVs) are considered genomic remnants of ancient viral infections acquired throughout vertebrate evolution. Their exogenous counterparts once infected the host's germline cells, eventually leading to the permanent endogenization of their respective proviruses. The success of ERV colonization is evident so that it constitutes 8% of the human genome. Emerging genomic studies indicate that endogenous retroviruses are not merely remnants of past infections but rather play a corollary role, despite not fully understood, in host genetic regulation. This review presents some evidence supporting the crucial role of endogenous retroviruses in regulating host genetics. We explore the involvement of human ERVs (HERVs) in key physiological processes, from their precise and orchestrated activities during cellular differentiation and pluripotency to their contributions to aging and cellular senescence. Additionally, we discuss the costs associated with hosting a substantial amount of preserved viral genetic material.
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Affiliation(s)
- Amanda Lopes da Silva
- Instituto de Medicina Tropical de São Paulo, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Bruno Luiz Miranda Guedes
- Instituto de Medicina Tropical de São Paulo, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Samuel Nascimento Santos
- UNISA Research Center, Universidade Santo Amaro, Post-Graduation in Health Sciences, São Paulo, Brazil
| | - Giovanna Francisco Correa
- Instituto de Medicina Tropical de São Paulo, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Ariane Nardy
- UNISA Research Center, Universidade Santo Amaro, Post-Graduation in Health Sciences, São Paulo, Brazil
| | | | - Andre Luis Lacerda Bachi
- UNISA Research Center, Universidade Santo Amaro, Post-Graduation in Health Sciences, São Paulo, Brazil
| | - Camila Malta Romano
- Instituto de Medicina Tropical de São Paulo, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
- Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, Brazil
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Dopkins N, Nixon DF. Activation of human endogenous retroviruses and its physiological consequences. Nat Rev Mol Cell Biol 2024; 25:212-222. [PMID: 37872387 DOI: 10.1038/s41580-023-00674-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2023] [Indexed: 10/25/2023]
Abstract
Human endogenous retroviruses (HERVs) are abundant sequences that persist within the human genome as remnants of ancient retroviral infections. These sequences became fixed and accumulate mutations or deletions over time. HERVs have affected human evolution and physiology by providing a unique repertoire of coding and non-coding sequences to the genome. In healthy individuals, HERVs participate in immune responses, formation of syncytiotrophoblasts and cell-fate specification. In this Review, we discuss how endogenized retroviral motifs and regulatory sequences have been co-opted into human physiology and how they are tightly regulated. Infections and mutations can derail this regulation, leading to differential HERV expression, which may contribute to pathologies including neurodegeneration, pathological inflammation and oncogenesis. Emerging evidence demonstrates that HERVs are crucial to human health and represent an understudied facet of many diseases, and we therefore argue that investigating their fundamental properties could improve existing therapies and help develop novel therapeutic strategies.
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Affiliation(s)
- Nicholas Dopkins
- Division of Infectious Diseases, Department of Medicine, Weill Cornell Medicine, New York, NY, USA.
| | - Douglas F Nixon
- Division of Infectious Diseases, Department of Medicine, Weill Cornell Medicine, New York, NY, USA.
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Ramirez P, Sun W, Kazempour Dehkordi S, Zare H, Fongang B, Bieniek KF, Frost B. Nanopore-based DNA long-read sequencing analysis of the aged human brain. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.01.578450. [PMID: 38370753 PMCID: PMC10871260 DOI: 10.1101/2024.02.01.578450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Aging disrupts cellular processes such as DNA repair and epigenetic control, leading to a gradual buildup of genomic alterations that can have detrimental effects in post-mitotic cells. Genomic alterations in regions of the genome that are rich in repetitive sequences, often termed "dark loci," are difficult to resolve using traditional sequencing approaches. New long-read technologies offer promising avenues for exploration of previously inaccessible regions of the genome. Using nanopore-based long-read whole-genome sequencing of DNA extracted from aged 18 human brains, we identify previously unreported structural variants and methylation patterns within repetitive DNA, focusing on transposable elements ("jumping genes") as crucial sources of variation, particularly in dark loci. Our analyses reveal potential somatic insertion variants and provides DNA methylation frequencies for many retrotransposon families. We further demonstrate the utility of this technology for the study of these challenging genomic regions in brains affected by Alzheimer's disease and identify significant differences in DNA methylation in pathologically normal brains versus those affected by Alzheimer's disease. Highlighting the power of this approach, we discover specific polymorphic retrotransposons with altered DNA methylation patterns. These retrotransposon loci have the potential to contribute to pathology, warranting further investigation in Alzheimer's disease research. Taken together, our study provides the first long-read DNA sequencing-based analysis of retrotransposon sequences, structural variants, and DNA methylation in the aging brain affected with Alzheimer's disease neuropathology.
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Affiliation(s)
- Paulino Ramirez
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas
- Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas
- Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
| | - Wenyan Sun
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas
- Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas
- Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
- School of Pharmacy, University of Missouri-Kansas City, Kansas City, Missouri
| | - Shiva Kazempour Dehkordi
- Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas
- Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
| | - Habil Zare
- Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas
- Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
| | - Bernard Fongang
- Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas
- Department of Biochemistry & Structural Biology, University of Texas Health San Antonio, San Antonio, Texas
| | - Kevin F. Bieniek
- Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas
- Department of Pathology, University of Texas Health San Antonio, San Antonio, Texas
| | - Bess Frost
- Barshop Institute for Longevity and Aging Studies, University of Texas Health San Antonio, San Antonio, Texas
- Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases, University of Texas Health San Antonio, San Antonio, Texas
- Department of Cell Systems and Anatomy, University of Texas Health San Antonio, San Antonio, Texas
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