1
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Garcia EL, Steiner RE, Raimer AC, Herring LE, Matera AG, Spring AM. Dysregulation of innate immune signaling in animal models of spinal muscular atrophy. BMC Biol 2024; 22:94. [PMID: 38664795 PMCID: PMC11044505 DOI: 10.1186/s12915-024-01888-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Accepted: 04/16/2024] [Indexed: 04/28/2024] Open
Abstract
BACKGROUND Spinal muscular atrophy (SMA) is a devastating neuromuscular disease caused by hypomorphic loss of function in the survival motor neuron (SMN) protein. SMA presents across a broad spectrum of disease severity. Unfortunately, genetic models of intermediate SMA have been difficult to generate in vertebrates and are thus unable to address key aspects of disease etiology. To address these issues, we developed a Drosophila model system that recapitulates the full range of SMA severity, allowing studies of pre-onset biology as well as late-stage disease processes. RESULTS Here, we carried out transcriptomic and proteomic profiling of mild and intermediate Drosophila models of SMA to elucidate molecules and pathways that contribute to the disease. Using this approach, we elaborated a role for the SMN complex in the regulation of innate immune signaling. We find that mutation or tissue-specific depletion of SMN induces hyperactivation of the immune deficiency (IMD) and Toll pathways, leading to overexpression of antimicrobial peptides (AMPs) and ectopic formation of melanotic masses in the absence of an external challenge. Furthermore, the knockdown of downstream targets of these signaling pathways reduced melanotic mass formation caused by SMN loss. Importantly, we identify SMN as a negative regulator of a ubiquitylation complex that includes Traf6, Bendless, and Diap2 and plays a pivotal role in several signaling networks. CONCLUSIONS In alignment with recent research on other neurodegenerative diseases, these findings suggest that hyperactivation of innate immunity contributes to SMA pathology. This work not only provides compelling evidence that hyperactive innate immune signaling is a primary effect of SMN depletion, but it also suggests that the SMN complex plays a regulatory role in this process in vivo. In summary, immune dysfunction in SMA is a consequence of reduced SMN levels and is driven by cellular and molecular mechanisms that are conserved between insects and mammals.
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Affiliation(s)
- Eric L Garcia
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
- Department of Biology, University of Kentucky, Lexington, KY, USA
| | - Rebecca E Steiner
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
- RNA Discovery and Lineberger Comprehensive Cancer Centers, University of North Carolina at Chapel Hill, Chapel Hill, 27599, USA
- Present Address: Lake, Erie College of Osteopathic Medicine, Bradenton, FL, USA
| | - Amanda C Raimer
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, 27599, USA
- Present Address, Radford University, Radford, VA, USA
| | - Laura E Herring
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, USA
| | - A Gregory Matera
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, 27599, USA.
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, 27599, USA.
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, 27599, USA.
- RNA Discovery and Lineberger Comprehensive Cancer Centers, University of North Carolina at Chapel Hill, Chapel Hill, 27599, USA.
| | - Ashlyn M Spring
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
- Department of Biology, University of North Carolina at Greensboro, Greensboro, NC, 27402, USA.
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2
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Wang J, Lu X, Zhang W, Liu GH. Endogenous retroviruses in development and health. Trends Microbiol 2024; 32:342-354. [PMID: 37802660 DOI: 10.1016/j.tim.2023.09.006] [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: 07/14/2023] [Revised: 09/12/2023] [Accepted: 09/13/2023] [Indexed: 10/08/2023]
Abstract
Endogenous retroviruses (ERVs) are evolutionary remnants of retroviral infections in which the viral genome became embedded as a dormant regulatory element within the host germline. When ERVs become activated, they comprehensively rewire genomic regulatory networks of the host and facilitate critical developmental events, such as preimplantation development and placentation, in a manner specific to species, developmental stage, and tissues. However, accumulating evidence suggests that aberrant ERV transcription compromises genome stability and has been implicated in cellular senescence and various pathogenic processes, underscoring the significance of host genomic surveillance mechanisms. Here, we revisit the prominent functions of ERVs in early development and highlight their emerging roles in mammalian post-implantation development and organogenesis. We also discuss their implications for aging and pathological processes such as microbial infection, immune response. Furthermore, we discuss recent advances in stem-cell-based models, single-cell omics, and genome editing technologies, which serve as beacons illuminating the versatile nature of ERVs in mammalian development and health.
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Affiliation(s)
- Jichang Wang
- Advanced Medical Technology Center, The First Affiliated Hospital, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China; Key Laboratory for Stem Cells and Tissue Engineering (Sun Yat-sen University), Ministry of Education, Guangzhou, 510080, China.
| | - Xinyi Lu
- State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300350, China.
| | - Weiqi Zhang
- CAS Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics and China National Center for Bioinformation, Chinese Academy of Sciences, Beijing 100101, China.
| | - Guang-Hui Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China; Beijing Institute for Stem Cell and Regenerative Medicine, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Advanced Innovation Center for Human Brain Protection, and National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital Capital Medical University, Beijing 100053, China.
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3
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Crawford BI, Talley MJ, Russman J, Riddle J, Torres S, Williams T, Longworth MS. Condensin-mediated restriction of retrotransposable elements facilitates brain development in Drosophila melanogaster. Nat Commun 2024; 15:2716. [PMID: 38548759 PMCID: PMC10978865 DOI: 10.1038/s41467-024-47042-9] [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: 12/22/2022] [Accepted: 03/18/2024] [Indexed: 04/01/2024] Open
Abstract
Neural stem and progenitor cell (NSPC) maintenance is essential for ensuring that organisms are born with proper brain volumes and head sizes. Microcephaly is a disorder in which babies are born with significantly smaller head sizes and cortical volumes. Mutations in subunits of the DNA organizing complex condensin have been identified in microcephaly patients. However, the molecular mechanisms by which condensin insufficiency causes microcephaly remain elusive. We previously identified conserved roles for condensins in repression of retrotransposable elements (RTEs). Here, we show that condensin subunit knockdown in NSPCs of the Drosophila larval central brain increases RTE expression and mobility which causes cell death, and significantly decreases adult head sizes and brain volumes. These findings suggest that unrestricted RTE expression and activity may lead to improper brain development in condensin insufficient organisms, and lay the foundation for future exploration of causative roles for RTEs in other microcephaly models.
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Affiliation(s)
- Bert I Crawford
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA
| | - Mary Jo Talley
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA
| | - Joshua Russman
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA
| | - James Riddle
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA
| | - Sabrina Torres
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA
| | - Troy Williams
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA
| | - Michelle S Longworth
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44195, USA.
- Cleveland Clinic Lerner College of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, 44195, USA.
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4
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Garcia EL, Steiner RE, Raimer AC, Herring LE, Matera AG, Spring AM. Dysregulation of innate immune signaling in animal models of Spinal Muscular Atrophy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.14.571739. [PMID: 38168196 PMCID: PMC10760185 DOI: 10.1101/2023.12.14.571739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Background Spinal Muscular Atrophy (SMA) is a devastating neuromuscular disease caused by hypomorphic loss of function in the Survival Motor Neuron (SMN) protein. SMA presents across broad spectrum of disease severity. Unfortunately, vertebrate models of intermediate SMA have been difficult to generate and are thus unable to address key aspects of disease etiology. To address these issues, we developed a Drosophila model system that recapitulates the full range of SMA severity, allowing studies of pre-onset biology as well as late-stage disease processes. Results Here, we carried out transcriptomic and proteomic profiling of mild and intermediate Drosophila models of SMA to elucidate molecules and pathways that contribute to the disease. Using this approach, we elaborated a role for the SMN complex in the regulation of innate immune signaling. We find that mutation or tissue-specific depletion of SMN induces hyperactivation of the Immune Deficiency (IMD) and Toll pathways, leading to overexpression of antimicrobial peptides (AMPs) and ectopic formation of melanotic masses in the absence of an external challenge. Furthermore, knockdown of downstream targets of these signaling pathways reduced melanotic mass formation caused by SMN loss. Importantly, we identify SMN as a negative regulator of an ubiquitylation complex that includes Traf6, Bendless and Diap2, and plays a pivotal role in several signaling networks. Conclusions In alignment with recent research on other neurodegenerative diseases, these findings suggest that hyperactivation of innate immunity contributes to SMA pathology. This work not only provides compelling evidence that hyperactive innate immune signaling is a primary effect of SMN depletion, but it also suggests that the SMN complex plays a regulatory role in this process in vivo. In summary, immune dysfunction in SMA is a consequence of reduced SMN levels and is driven by cellular and molecular mechanisms that are conserved between insects and mammals.
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Affiliation(s)
- Eric L. Garcia
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill NC, USA
- Department of Biology, University of Kentucky, Lexington KY, USA
| | - Rebecca E. Steiner
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill NC, USA
- Department of Biology, University of North Carolina at Chapel Hill
| | - Amanda C. Raimer
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill NC, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill
| | - Laura E. Herring
- Department of Pharmacology, University of North Carolina at Chapel Hill
| | - A. Gregory Matera
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill NC, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill
- Department of Biology, University of North Carolina at Chapel Hill
- Department of Genetics, University of North Carolina at Chapel Hill
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill
| | - Ashlyn M. Spring
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill NC, USA
- Department of Biology, University of North Carolina at Greensboro, Greensboro NC, USA
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5
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Yang F, Su W, Chung OW, Tracy L, Wang L, Ramsden DA, Zhang ZZZ. Retrotransposons hijack alt-EJ for DNA replication and eccDNA biogenesis. Nature 2023; 620:218-225. [PMID: 37438532 PMCID: PMC10691919 DOI: 10.1038/s41586-023-06327-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 06/14/2023] [Indexed: 07/14/2023]
Abstract
Retrotransposons are highly enriched in the animal genome1-3. The activation of retrotransposons can rewrite host DNA information and fundamentally impact host biology1-3. Although developmental activation of retrotransposons can offer benefits for the host, such as against virus infection, uncontrolled activation promotes disease or potentially drives ageing1-5. After activation, retrotransposons use their mRNA as templates to synthesize double-stranded DNA for making new insertions in the host genome1-3,6. Although the reverse transcriptase that they encode can synthesize the first-strand DNA1-3,6, how the second-strand DNA is generated remains largely unclear. Here we report that retrotransposons hijack the alternative end-joining (alt-EJ) DNA repair process of the host for a circularization step to synthesize their second-strand DNA. We used Nanopore sequencing to examine the fates of replicated retrotransposon DNA, and found that 10% of them achieve new insertions, whereas 90% exist as extrachromosomal circular DNA (eccDNA). Using eccDNA production as a readout, further genetic screens identified factors from alt-EJ as essential for retrotransposon replication. alt-EJ drives the second-strand synthesis of the long terminal repeat retrotransposon DNA through a circularization process and is therefore necessary for eccDNA production and new insertions. Together, our study reveals that alt-EJ is essential in driving the propagation of parasitic genomic retroelements. Our study uncovers a conserved function of this understudied DNA repair process, and provides a new perspective to understand-and potentially control-the retrotransposon life cycle.
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Affiliation(s)
- Fu Yang
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, USA
| | - Weijia Su
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, USA
| | - Oliver W Chung
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, USA
| | - Lauren Tracy
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, USA
| | - Lu Wang
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, USA
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Dale A Ramsden
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Z Z Zhao Zhang
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, USA.
- Duke Regeneration Center, Duke University School of Medicine, Durham, NC, USA.
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6
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Ferreiro ME, Faulkner GJ. Endogenous retroviruses can propagate TDP-43 proteinopathy. Trends Neurosci 2023; 46:413-414. [PMID: 37061454 DOI: 10.1016/j.tins.2023.03.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 03/31/2023] [Indexed: 04/17/2023]
Abstract
How does neurodegeneration spread in the brain? Leveraging TDP-43 fly models of amyotrophic lateral sclerosis (ALS), Chang and Dubnau recently reported that the endogenous retrovirus (ERV) mdg4 can trigger and transmit TDP-43 proteinopathy in vivo. Their results suggest that human ERVs could be targeted to develop future ALS therapies.
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Affiliation(s)
- Maria E Ferreiro
- Queensland Brain Institute, University of Queensland, St Lucia, QLD, 4067, Australia
| | - Geoffrey J Faulkner
- Queensland Brain Institute, University of Queensland, St Lucia, QLD, 4067, Australia; Mater Research Institute - University of Queensland, Woolloongabba, QLD, 4102, Australia.
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7
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Botto JM, Faulkner GJ. Endogenous retrovirus expression during fruitfly metamorphosis enhances adult viral immunity. Nat Genet 2022; 54:1765-1767. [PMID: 36396708 DOI: 10.1038/s41588-022-01209-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Juan M Botto
- Queensland Brain Institute, University of Queensland, St. Lucia, Queensland, Australia
| | - Geoffrey J Faulkner
- Queensland Brain Institute, University of Queensland, St. Lucia, Queensland, Australia. .,Mater Research Institute, University of Queensland, Woolloongabba, Queensland, Australia.
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