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Feng Z, Ye W, Feng L. Bioactives and metabolites of Tetrastigma hemsleyanum root extract alleviate DSS-induced ulcerative colitis by targeting the SYK protein in the B cell receptor signaling pathway. JOURNAL OF ETHNOPHARMACOLOGY 2024; 322:117563. [PMID: 38104876 DOI: 10.1016/j.jep.2023.117563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 11/27/2023] [Accepted: 12/05/2023] [Indexed: 12/19/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Tetrastigma hemsleyanum is an endemic Chinese herb with a wide range of pharmacological activities, including anti-inflammatory, antiviral, antioxidant, antitumor, and immunomodulatory activities. However, the effect and mechanisms of the anti-inflammatory activity of T. hemsleyanum root extract against dextran sodium sulfate (DSS)-induced ulcerative colitis (UC) have not yet been fully investigated. AIM OF THE STUDY This study aimed to explore the therapeutic effect and molecular mechanisms of T. hemsleyanum root extract in DSS-induced UC mice and knockdown cells. MATERIALS AND METHODS T. hemsleyanum root extract was obtained and analyzed by high-performance liquid chromatography (HPLC). The therapeutic effects of T. hemsleyanum root extract on DSS-induced UC mice were evaluated by the disease activity index (DAI) score, colon length, serum inflammatory cytokines and oxidant/antioxidant levels, and histopathological features of the ileum and colon. Genome-wide gene expression profiles of ileal and colonic tissues were collected by transcriptomics, and signaling pathways were analyzed by the KEGG database. UC-related pathways were uploaded to the STRING database, then the protein-protein interactions (PPIs) were determined by Cytoscape, and the enriched genes were evaluated by real-time quantitative PCR (qPCR). The protein-ligand complexes were docked by AutoDock, and the genes were knocked down in Caco-2 cells by shRNA. The non-targeted metabolomic profiling of ileal contents was analyzed by ultra-high-performance liquid chromatography (UHPLC), and gut microflora were sequenced by an Illumina MiSeq System. RESULTS Ten components that alleviated UC symptoms in mice by decreasing the DAI and serum inflammatory cytokines and oxidant levels, promoting intestinal development, and increasing serum antioxidant levels were identified in T. hemsleyanum root extract. T. hemsleyanum root extract activated the B cell receptor signaling pathway in the colon tissue of UC mice, in which two components, rutin and astragaline, bound to the spleen tyrosine kinase (SYK) protein but also restored gut microflora diversity and increased the proportion of probiotics. Furthermore, metabolites of T. hemsleyanum root extract were involved in vitamin metabolism, fatty acid metabolism, and ferroptosis. CONCLUSIONS The rutin and astragaline components of T. hemsleyanum root extract, by binding to SYK protein, activated the B cell receptor signaling pathway and restored gut microflora diversity to alleviate UC symptoms in mice.
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Affiliation(s)
- Zhengquan Feng
- Department of Oncology, Tongde Hospital of Zhejiang Province, Hangzhou, 310012, China
| | - Wei Ye
- Food Safety Key Laboratory of Zhejiang Province, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, 310018, China
| | - Lifang Feng
- Food Safety Key Laboratory of Zhejiang Province, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, 310018, China.
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Bétermier M, Klobutcher LA, Orias E. Programmed chromosome fragmentation in ciliated protozoa: multiple means to chromosome ends. Microbiol Mol Biol Rev 2023; 87:e0018422. [PMID: 38009915 PMCID: PMC10732028 DOI: 10.1128/mmbr.00184-22] [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] [Indexed: 11/29/2023] Open
Abstract
SUMMARYCiliated protozoa undergo large-scale developmental rearrangement of their somatic genomes when forming a new transcriptionally active macronucleus during conjugation. This process includes the fragmentation of chromosomes derived from the germline, coupled with the efficient healing of the broken ends by de novo telomere addition. Here, we review what is known of developmental chromosome fragmentation in ciliates that have been well-studied at the molecular level (Tetrahymena, Paramecium, Euplotes, Stylonychia, and Oxytricha). These organisms differ substantially in the fidelity and precision of their fragmentation systems, as well as in the presence or absence of well-defined sequence elements that direct excision, suggesting that chromosome fragmentation systems have evolved multiple times and/or have been significantly altered during ciliate evolution. We propose a two-stage model for the evolution of the current ciliate systems, with both stages involving repetitive or transposable elements in the genome. The ancestral form of chromosome fragmentation is proposed to have been derived from the ciliate small RNA/chromatin modification process that removes transposons and other repetitive elements from the macronuclear genome during development. The evolution of this ancestral system is suggested to have potentiated its replacement in some ciliate lineages by subsequent fragmentation systems derived from mobile genetic elements.
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Affiliation(s)
- Mireille Bétermier
- Department of Genome Biology, Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell, Gif-sur-Yvette, France
| | - Lawrence A. Klobutcher
- Department of Molecular Biology and Biophysics, UCONN Health (University of Connecticut), Farmington, Connecticut, USA
| | - Eduardo Orias
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, California, USA
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Meng X, Dang HQ, Kapler GM. Developmentally Programmed Switches in DNA Replication: Gene Amplification and Genome-Wide Endoreplication in Tetrahymena. Microorganisms 2023; 11:microorganisms11020491. [PMID: 36838456 PMCID: PMC9967165 DOI: 10.3390/microorganisms11020491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 12/29/2022] [Accepted: 02/09/2023] [Indexed: 02/18/2023] Open
Abstract
Locus-specific gene amplification and genome-wide endoreplication generate the elevated copy number of ribosomal DNA (rDNA, 9000 C) and non-rDNA (90 C) chromosomes in the developing macronucleus of Tetrahymena thermophila. Subsequently, all macronuclear chromosomes replicate once per cell cycle during vegetative growth. Here, we describe an unanticipated, programmed switch in the regulation of replication initiation in the rDNA minichromosome. Early in development, the 21 kb rDNA minichromosome is preferentially amplified from 2 C to ~800 C from well-defined origins, concurrent with genome-wide endoreplication (2 C to 8-16 C) in starved mating Tetrahymena (endoreplication (ER) Phase 1). Upon refeeding, rDNA and non-rDNA chromosomes achieve their final copy number through resumption of just the endoreplication program (ER Phase 2). Unconventional rDNA replication intermediates are generated primarily during ER phase 2, consistent with delocalized replication initiation and possible formation of persistent RNA-DNA hybrids. Origin usage and replication fork elongation are affected in non-rDNA chromosomes as well. Despite the developmentally programmed 10-fold reduction in the ubiquitous eukaryotic initiator, the Origin Recognition Complex (ORC), active initiation sites are more closely spaced in ER phases 1 and 2 compared to vegetative growing cells. We propose that initiation site selection is relaxed in endoreplicating macronuclear chromosomes and may be less dependent on ORC.
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Affiliation(s)
- Xiangzhou Meng
- Department of Cell Biology and Genetics, Texas A&M University Health Science Center, Bryan, TX 77807, USA
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hung Quang Dang
- Department of Cell Biology and Genetics, Texas A&M University Health Science Center, Bryan, TX 77807, USA
- Alstem Bioscience, Richmond, CA 94806, USA
| | - Geoffrey M. Kapler
- Department of Cell Biology and Genetics, Texas A&M University Health Science Center, Bryan, TX 77807, USA
- Correspondence: ; Tel.: +1-979-574-3901
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Origins of genome-editing excisases as illuminated by the somatic genome of the ciliate Blepharisma. Proc Natl Acad Sci U S A 2023; 120:e2213887120. [PMID: 36669098 PMCID: PMC9942806 DOI: 10.1073/pnas.2213887120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Massive DNA excision occurs regularly in ciliates, ubiquitous microbial eukaryotes with somatic and germline nuclei in the same cell. Tens of thousands of internally eliminated sequences (IESs) scattered throughout the ciliate germline genome are deleted during the development of the streamlined somatic genome. The genus Blepharisma represents one of the two high-level ciliate clades (subphylum Postciliodesmatophora) and, unusually, has dual pathways of somatic nuclear and genome development. This makes it ideal for investigating the functioning and evolution of these processes. Here we report the somatic genome assembly of Blepharisma stoltei strain ATCC 30299 (41 Mbp), arranged as numerous telomere-capped minichromosomal isoforms. This genome encodes eight PiggyBac transposase homologs no longer harbored by transposons. All appear subject to purifying selection, but just one, the putative IES excisase, has a complete catalytic triad. We hypothesize that PiggyBac homologs were ancestral excisases that enabled the evolution of extensive natural genome editing.
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MITE infestation accommodated by genome editing in the germline genome of the ciliate Blepharisma. Proc Natl Acad Sci U S A 2023; 120:e2213985120. [PMID: 36669106 PMCID: PMC9942856 DOI: 10.1073/pnas.2213985120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
During their development following sexual conjugation, ciliates excise numerous internal eliminated sequences (IESs) from a copy of the germline genome to produce the functional somatic genome. Most IESs are thought to have originated from transposons, but the presumed homology is often obscured by sequence decay. To obtain more representative perspectives on the nature of IESs and ciliate genome editing, we assembled 40,000 IESs of Blepharisma stoltei, a species belonging to a lineage (Heterotrichea) that diverged early from those of the intensively studied model ciliate species. About a quarter of IESs were short (<115 bp), largely nonrepetitive, and with a pronounced ~10 bp periodicity in length; the remainder were longer (up to 7 kbp) and nonperiodic and contained abundant interspersed repeats. Contrary to the expectation from current models, the assembled Blepharisma germline genome encodes few transposases. Instead, its most abundant repeat (8,000 copies) is a Miniature Inverted-repeat Transposable Element (MITE), apparently a deletion derivative of a germline-limited Pogo-family transposon. We hypothesize that MITEs are an important source of IESs whose proliferation is eventually self-limiting and that rather than defending the germline genomes against mobile elements, transposase domestication actually facilitates the accumulation of junk DNA.
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Structural insights into the evolution of the RAG recombinase. Nat Rev Immunol 2022; 22:353-370. [PMID: 34675378 DOI: 10.1038/s41577-021-00628-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/09/2021] [Indexed: 11/09/2022]
Abstract
Adaptive immunity in jawed vertebrates relies on the assembly of antigen receptor genes by the recombination activating gene 1 (RAG1)-RAG2 (collectively RAG) recombinase in a reaction known as V(D)J recombination. Extensive biochemical and structural evidence indicates that RAG and V(D)J recombination evolved from the components of a RAG-like (RAGL) transposable element through a process known as transposon molecular domestication. This Review describes recent advances in our understanding of the functional and structural transitions that occurred during RAG evolution. We use the structures of RAG and RAGL enzymes to trace the evolutionary adaptations that yielded a RAG recombinase with exquisitely regulated cleavage activity and a multilayered array of mechanisms to suppress transposition. We describe how changes in modes of DNA binding, alterations in the dynamics of protein-DNA complexes, single amino acid mutations and a modular design likely enabled RAG family enzymes to survive and spread in the genomes of eukaryotes. These advances highlight the insight that can be gained from viewing evolution of vertebrate immunity through the lens of comparative genome analyses coupled with structural biology and biochemistry.
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Zangarelli C, Arnaiz O, Bourge M, Gorrichon K, Jaszczyszyn Y, Mathy N, Escoriza L, Bétermier M, Régnier V. Developmental timing of programmed DNA elimination in Paramecium tetraurelia recapitulates germline transposon evolutionary dynamics. Genome Res 2022; 32:2028-2042. [PMID: 36418061 PMCID: PMC9808624 DOI: 10.1101/gr.277027.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 11/11/2022] [Indexed: 11/24/2022]
Abstract
With its nuclear dualism, the ciliate Paramecium constitutes a unique model to study how host genomes cope with transposable elements (TEs). P. tetraurelia harbors two germline micronuclei (MICs) and a polyploid somatic macronucleus (MAC) that develops from one MIC at each sexual cycle. Throughout evolution, the MIC genome has been continuously colonized by TEs and related sequences that are removed from the somatic genome during MAC development. Whereas TE elimination is generally imprecise, excision of approximately 45,000 TE-derived internal eliminated sequences (IESs) is precise, allowing for functional gene assembly. Programmed DNA elimination is concomitant with genome amplification. It is guided by noncoding RNAs and repressive chromatin marks. A subset of IESs is excised independently of this epigenetic control, raising the question of how IESs are targeted for elimination. To gain insight into the determinants of IES excision, we established the developmental timing of DNA elimination genome-wide by combining fluorescence-assisted nuclear sorting with high-throughput sequencing. Essentially all IESs are excised within only one endoreplication round (32C to 64C), whereas TEs are eliminated at a later stage. We show that DNA elimination proceeds independently of replication. We defined four IES classes according to excision timing. The earliest excised IESs tend to be independent of epigenetic factors, display strong sequence signals at their ends, and originate from the most ancient integration events. We conclude that old IESs have been optimized during evolution for early and accurate excision by acquiring stronger sequence determinants and escaping epigenetic control.
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Affiliation(s)
- Coralie Zangarelli
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Olivier Arnaiz
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Mickaël Bourge
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Kevin Gorrichon
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Yan Jaszczyszyn
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Nathalie Mathy
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Loïc Escoriza
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Mireille Bétermier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Vinciane Régnier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France;,Université Paris Cité, UFR Sciences du Vivant, 75205 Paris Cedex 13, France
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8
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Programmed DNA elimination: silencing genes and repetitive sequences in somatic cells. Biochem Soc Trans 2021; 49:1891-1903. [PMID: 34665225 DOI: 10.1042/bst20190951] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/25/2021] [Accepted: 09/28/2021] [Indexed: 12/30/2022]
Abstract
In a multicellular organism, the genomes of all cells are in general the same. Programmed DNA elimination is a notable exception to this genome constancy rule. DNA elimination removes genes and repetitive elements in the germline genome to form a reduced somatic genome in various organisms. The process of DNA elimination within an organism is highly accurate and reproducible; it typically occurs during early embryogenesis, coincident with germline-soma differentiation. DNA elimination provides a mechanism to silence selected genes and repeats in somatic cells. Recent studies in nematodes suggest that DNA elimination removes all chromosome ends, resolves sex chromosome fusions, and may also promote the birth of novel genes. Programmed DNA elimination processes are diverse among species, suggesting DNA elimination likely has evolved multiple times in different taxa. The growing list of organisms that undergo DNA elimination indicates that DNA elimination may be more widespread than previously appreciated. These various organisms will serve as complementary and comparative models to study the function, mechanism, and evolution of programmed DNA elimination in metazoans.
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Sellis D, Guérin F, Arnaiz O, Pett W, Lerat E, Boggetto N, Krenek S, Berendonk T, Couloux A, Aury JM, Labadie K, Malinsky S, Bhullar S, Meyer E, Sperling L, Duret L, Duharcourt S. Massive colonization of protein-coding exons by selfish genetic elements in Paramecium germline genomes. PLoS Biol 2021; 19:e3001309. [PMID: 34324490 PMCID: PMC8354472 DOI: 10.1371/journal.pbio.3001309] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 08/10/2021] [Accepted: 06/04/2021] [Indexed: 11/18/2022] Open
Abstract
Ciliates are unicellular eukaryotes with both a germline genome and a somatic genome in the same cytoplasm. The somatic macronucleus (MAC), responsible for gene expression, is not sexually transmitted but develops from a copy of the germline micronucleus (MIC) at each sexual generation. In the MIC genome of Paramecium tetraurelia, genes are interrupted by tens of thousands of unique intervening sequences called internal eliminated sequences (IESs), which have to be precisely excised during the development of the new MAC to restore functional genes. To understand the evolutionary origin of this peculiar genomic architecture, we sequenced the MIC genomes of 9 Paramecium species (from approximately 100 Mb in Paramecium aurelia species to >1.5 Gb in Paramecium caudatum). We detected several waves of IES gains, both in ancestral and in more recent lineages. While the vast majority of IESs are single copy in present-day genomes, we identified several families of mobile IESs, including nonautonomous elements acquired via horizontal transfer, which generated tens to thousands of new copies. These observations provide the first direct evidence that transposable elements can account for the massive proliferation of IESs in Paramecium. The comparison of IESs of different evolutionary ages indicates that, over time, IESs shorten and diverge rapidly in sequence while they acquire features that allow them to be more efficiently excised. We nevertheless identified rare cases of IESs that are under strong purifying selection across the aurelia clade. The cases examined contain or overlap cellular genes that are inactivated by excision during development, suggesting conserved regulatory mechanisms. Similar to the evolution of introns in eukaryotes, the evolution of Paramecium IESs highlights the major role played by selfish genetic elements in shaping the complexity of genome architecture and gene expression. A comparative genomics study of nine Paramecium species reveals successful invasion of genes by transposable elements in their germline genomes, showing that the internal eliminated sequences (IESs) followed an evolutionary trajectory remarkably similar to that of spliceosomal introns.
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Affiliation(s)
- Diamantis Sellis
- Université de Lyon, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Villeurbanne, France
| | - Frédéric Guérin
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France
| | - Olivier Arnaiz
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Walker Pett
- Université de Lyon, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Villeurbanne, France
| | - Emmanuelle Lerat
- Université de Lyon, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Villeurbanne, France
| | - Nicole Boggetto
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France
| | - Sascha Krenek
- TU Dresden, Institute of Hydrobiology, Dresden, Germany
| | | | - Arnaud Couloux
- Génomique Métabolique, Genoscope, Institut de biologie François Jacob, CEA, CNRS, Université d’Évry, Université Paris-Saclay, Evry, France
| | - Jean-Marc Aury
- Génomique Métabolique, Genoscope, Institut de biologie François Jacob, CEA, CNRS, Université d’Évry, Université Paris-Saclay, Evry, France
| | - Karine Labadie
- Genoscope, Institut de biologie François-Jacob, Commissariat à l’Energie Atomique (CEA), Université Paris-Saclay, Evry, France
| | - Sophie Malinsky
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France
- Université de Paris, Paris, France
| | - Simran Bhullar
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France
| | - Eric Meyer
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France
| | - Linda Sperling
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Laurent Duret
- Université de Lyon, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Villeurbanne, France
- * E-mail: (LD); (SD)
| | - Sandra Duharcourt
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France
- * E-mail: (LD); (SD)
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Bergero R, Ellis P, Haerty W, Larcombe L, Macaulay I, Mehta T, Mogensen M, Murray D, Nash W, Neale MJ, O'Connor R, Ottolini C, Peel N, Ramsey L, Skinner B, Suh A, Summers M, Sun Y, Tidy A, Rahbari R, Rathje C, Immler S. Meiosis and beyond - understanding the mechanistic and evolutionary processes shaping the germline genome. Biol Rev Camb Philos Soc 2021; 96:822-841. [PMID: 33615674 PMCID: PMC8246768 DOI: 10.1111/brv.12680] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 12/15/2020] [Accepted: 12/15/2020] [Indexed: 12/11/2022]
Abstract
The separation of germ cell populations from the soma is part of the evolutionary transition to multicellularity. Only genetic information present in the germ cells will be inherited by future generations, and any molecular processes affecting the germline genome are therefore likely to be passed on. Despite its prevalence across taxonomic kingdoms, we are only starting to understand details of the underlying micro-evolutionary processes occurring at the germline genome level. These include segregation, recombination, mutation and selection and can occur at any stage during germline differentiation and mitotic germline proliferation to meiosis and post-meiotic gamete maturation. Selection acting on germ cells at any stage from the diploid germ cell to the haploid gametes may cause significant deviations from Mendelian inheritance and may be more widespread than previously assumed. The mechanisms that affect and potentially alter the genomic sequence and allele frequencies in the germline are pivotal to our understanding of heritability. With the rise of new sequencing technologies, we are now able to address some of these unanswered questions. In this review, we comment on the most recent developments in this field and identify current gaps in our knowledge.
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Affiliation(s)
- Roberta Bergero
- Institute of Evolutionary BiologyUniversity of EdinburghEdinburghEH9 3JTU.K.
| | - Peter Ellis
- School of BiosciencesUniversity of KentCanterburyCT2 7NJU.K.
| | | | - Lee Larcombe
- Applied Exomics LtdStevenage Bioscience CatalystStevenageSG1 2FXU.K.
| | - Iain Macaulay
- Earlham InstituteNorwich Research ParkNorwichNR4 7UZU.K.
| | - Tarang Mehta
- Earlham InstituteNorwich Research ParkNorwichNR4 7UZU.K.
| | - Mette Mogensen
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJU.K.
| | - David Murray
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJU.K.
| | - Will Nash
- Earlham InstituteNorwich Research ParkNorwichNR4 7UZU.K.
| | - Matthew J. Neale
- Genome Damage and Stability Centre, School of Life SciencesUniversity of SussexBrightonBN1 9RHU.K.
| | | | | | - Ned Peel
- Earlham InstituteNorwich Research ParkNorwichNR4 7UZU.K.
| | - Luke Ramsey
- The James Hutton InstituteInvergowrieDundeeDD2 5DAU.K.
| | - Ben Skinner
- School of Life SciencesUniversity of EssexColchesterCO4 3SQU.K.
| | - Alexander Suh
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJU.K.
- Department of Organismal BiologyUppsala UniversityNorbyvägen 18DUppsala752 36Sweden
| | - Michael Summers
- School of BiosciencesUniversity of KentCanterburyCT2 7NJU.K.
- The Bridge Centre1 St Thomas Street, London BridgeLondonSE1 9RYU.K.
| | - Yu Sun
- Norwich Medical SchoolUniversity of East AngliaNorwich Research Park, Colney LnNorwichNR4 7UGU.K.
| | - Alison Tidy
- School of BiosciencesUniversity of Nottingham, Plant Science, Sutton Bonington CampusSutton BoningtonLE12 5RDU.K.
| | | | - Claudia Rathje
- School of BiosciencesUniversity of KentCanterburyCT2 7NJU.K.
| | - Simone Immler
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJU.K.
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11
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Guérineau M, Bessa L, Moriau S, Lescop E, Bontems F, Mathy N, Guittet E, Bischerour J, Bétermier M, Morellet N. The unusual structure of the PiggyMac cysteine-rich domain reveals zinc finger diversity in PiggyBac-related transposases. Mob DNA 2021; 12:12. [PMID: 33926516 PMCID: PMC8086355 DOI: 10.1186/s13100-021-00240-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 03/09/2021] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Transposons are mobile genetic elements that colonize genomes and drive their plasticity in all organisms. DNA transposon-encoded transposases bind to the ends of their cognate transposons and catalyze their movement. In some cases, exaptation of transposon genes has allowed novel cellular functions to emerge. The PiggyMac (Pgm) endonuclease of the ciliate Paramecium tetraurelia is a domesticated transposase from the PiggyBac family. It carries a core catalytic domain typical of PiggyBac-related transposases and a short cysteine-rich domain (CRD), flanked by N- and C-terminal extensions. During sexual processes Pgm catalyzes programmed genome rearrangements (PGR) that eliminate ~ 30% of germline DNA from the somatic genome at each generation. How Pgm recognizes its DNA cleavage sites in chromatin is unclear and the structure-function relationships of its different domains have remained elusive. RESULTS We provide insight into Pgm structure by determining the fold adopted by its CRD, an essential domain required for PGR. Using Nuclear Magnetic Resonance, we show that the Pgm CRD binds two Zn2+ ions and forms an unusual binuclear cross-brace zinc finger, with a circularly permutated treble-clef fold flanked by two flexible arms. The Pgm CRD structure clearly differs from that of several other PiggyBac-related transposases, among which is the well-studied PB transposase from Trichoplusia ni. Instead, the arrangement of cysteines and histidines in the primary sequence of the Pgm CRD resembles that of active transposases from piggyBac-like elements found in other species and of human PiggyBac-derived domesticated transposases. We show that, unlike the PB CRD, the Pgm CRD does not bind DNA. Instead, it interacts weakly with the N-terminus of histone H3, whatever its lysine methylation state. CONCLUSIONS The present study points to the structural diversity of the CRD among transposases from the PiggyBac family and their domesticated derivatives, and highlights the diverse interactions this domain may establish with chromatin, from sequence-specific DNA binding to contacts with histone tails. Our data suggest that the Pgm CRD fold, whose unusual arrangement of cysteines and histidines is found in all PiggyBac-related domesticated transposases from Paramecium and Tetrahymena, was already present in the ancestral active transposase that gave rise to ciliate domesticated proteins.
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Affiliation(s)
- Marc Guérineau
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Luiza Bessa
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
- Present addresses: Université Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), 71 Avenue des Martyrs, 38000, Grenoble, France
| | - Séverine Moriau
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Ewen Lescop
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - François Bontems
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Nathalie Mathy
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
- Reproduction et Développement des Plantes UMR 5667, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364, Lyon Cedex 07, France
| | - Eric Guittet
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Julien Bischerour
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Mireille Bétermier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France.
| | - Nelly Morellet
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France.
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12
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Miller RV, Neme R, Clay DM, Pathmanathan JS, Lu MW, Yerlici VT, Khurana JS, Landweber LF. Transcribed germline-limited coding sequences in Oxytricha trifallax. G3-GENES GENOMES GENETICS 2021; 11:6192809. [PMID: 33772542 PMCID: PMC8495736 DOI: 10.1093/g3journal/jkab092] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 02/26/2021] [Indexed: 01/13/2023]
Abstract
The germline-soma divide is a fundamental distinction in developmental biology, and different genes are expressed in germline and somatic cells throughout metazoan life cycles. Ciliates, a group of microbial eukaryotes, exhibit germline-somatic nuclear dimorphism within a single cell with two different genomes. The ciliate Oxytricha trifallax undergoes massive RNA-guided DNA elimination and genome rearrangement to produce a new somatic macronucleus (MAC) from a copy of the germline micronucleus (MIC). This process eliminates noncoding DNA sequences that interrupt genes and also deletes hundreds of germline-limited open reading frames (ORFs) that are transcribed during genome rearrangement. Here, we update the set of transcribed germline-limited ORFs (TGLOs) in O. trifallax. We show that TGLOs tend to be expressed during nuclear development and then are absent from the somatic MAC. We also demonstrate that exposure to synthetic RNA can reprogram TGLO retention in the somatic MAC and that TGLO retention leads to transcription outside the normal developmental program. These data suggest that TGLOs represent a group of developmentally regulated protein-coding sequences whose gene expression is terminated by DNA elimination.
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Affiliation(s)
- Richard V Miller
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.,Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Rafik Neme
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Derek M Clay
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.,Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Jananan S Pathmanathan
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Michael W Lu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.,Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - V Talya Yerlici
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Jaspreet S Khurana
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Laura F Landweber
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.,Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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13
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Xu J, Zhao X, Mao F, Basrur V, Ueberheide B, Chait BT, Allis CD, Taverna SD, Gao S, Wang W, Liu Y. A Polycomb repressive complex is required for RNAi-mediated heterochromatin formation and dynamic distribution of nuclear bodies. Nucleic Acids Res 2021; 49:5407-5425. [PMID: 33412588 PMCID: PMC8191774 DOI: 10.1093/nar/gkaa1262] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 12/02/2020] [Accepted: 01/04/2021] [Indexed: 01/17/2023] Open
Abstract
Polycomb group (PcG) proteins are widely utilized for transcriptional repression in eukaryotes. Here, we characterize, in the protist Tetrahymena thermophila, the EZL1 (E(z)-like 1) complex, with components conserved in metazoan Polycomb Repressive Complexes 1 and 2 (PRC1 and PRC2). The EZL1 complex is required for histone H3 K27 and K9 methylation, heterochromatin formation, transposable element control, and programmed genome rearrangement. The EZL1 complex interacts with EMA1, a helicase required for RNA interference (RNAi). This interaction is implicated in co-transcriptional recruitment of the EZL1 complex. Binding of H3K27 and H3K9 methylation by PDD1-another PcG protein interacting with the EZL1 complex-reinforces its chromatin association. The EZL1 complex is an integral part of Polycomb bodies, which exhibit dynamic distribution in Tetrahymena development: Their dispersion is driven by chromatin association, while their coalescence by PDD1, likely via phase separation. Our results provide a molecular mechanism connecting RNAi and Polycomb repression, which coordinately regulate nuclear bodies and reorganize the genome.
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Affiliation(s)
| | | | - Fengbiao Mao
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Venkatesha Basrur
- Proteomics Resource Facility, Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Beatrix Ueberheide
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, the Rockefeller University, New York, NY 10065, USA
| | - Brian T Chait
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, the Rockefeller University, New York, NY 10065, USA
| | - C David Allis
- Laboratory of Chromatin Biology and Epigenetics, the Rockefeller University, New York, NY 10065, USA
| | - Sean D Taverna
- Department of Pharmacology and Molecular Sciences and the Center for Epigenetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Shan Gao
- Correspondence may also be addressed to Shan Gao.
| | - Wei Wang
- Correspondence may also be addressed to Wei Wang.
| | - Yifan Liu
- To whom correspondence should be addressed. Tel: +1 323 865 3852;
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14
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Rzeszutek I, Maurer-Alcalá XX, Nowacki M. Programmed genome rearrangements in ciliates. Cell Mol Life Sci 2020; 77:4615-4629. [PMID: 32462406 PMCID: PMC7599177 DOI: 10.1007/s00018-020-03555-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 05/11/2020] [Accepted: 05/15/2020] [Indexed: 12/14/2022]
Abstract
Ciliates are a highly divergent group of unicellular eukaryotes with separate somatic and germline genomes found in distinct dimorphic nuclei. This characteristic feature is tightly linked to extremely laborious developmentally regulated genome rearrangements in the development of a new somatic genome/nuclei following sex. The transformation from germline to soma genome involves massive DNA elimination mediated by non-coding RNAs, chromosome fragmentation, as well as DNA amplification. In this review, we discuss the similarities and differences in the genome reorganization processes of the model ciliates Paramecium and Tetrahymena (class Oligohymenophorea), and the distantly related Euplotes, Stylonychia, and Oxytricha (class Spirotrichea).
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Affiliation(s)
- Iwona Rzeszutek
- Institute of Biology and Biotechnology, Department of Biotechnology, University of Rzeszow, Pigonia 1, 35-310, Rzeszow, Poland.
| | - Xyrus X Maurer-Alcalá
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland.
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15
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Allen SE, Nowacki M. Roles of Noncoding RNAs in Ciliate Genome Architecture. J Mol Biol 2020; 432:4186-4198. [PMID: 31926952 PMCID: PMC7374600 DOI: 10.1016/j.jmb.2019.12.042] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 12/19/2019] [Accepted: 12/20/2019] [Indexed: 11/29/2022]
Abstract
Ciliates are an interesting model system for investigating diverse functions of noncoding RNAs, especially in genome defence pathways. During sexual development, the ciliate somatic genome undergoes massive rearrangement and reduction through removal of transposable elements and other repetitive DNA. This is guided by a multitude of noncoding RNAs of different sizes and functions, the extent of which is only recently becoming clear. The genome rearrangement pathways evolved as a defence against parasitic DNA, but interestingly also use the transposable elements and transposases to execute their own removal. Thus, ciliates are also a good model for the coevolution of host and transposable element, and the mutual dependence between the two. In this review, we summarise the genome rearrangement pathways in three diverse species of ciliate, with focus on recent discoveries and the roles of noncoding RNAs. Ciliate genomes undergo massive rearrangement and reduction during development. Transposon elimination is guided by small RNAs and carried out by transposases. New pathways for noncoding RNA production have recently been discovered in ciliates. Diverse ciliate species have different mechanisms for RNA-guided genome remodeling.
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Affiliation(s)
- Sarah E Allen
- Institute of Cell Biology, University of Bern, Switzerland
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16
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Wang Y, Sheng Y, Liu Y, Zhang W, Cheng T, Duan L, Pan B, Qiao Y, Liu Y, Gao S. A distinct class of eukaryotic MT-A70 methyltransferases maintain symmetric DNA N6-adenine methylation at the ApT dinucleotides as an epigenetic mark associated with transcription. Nucleic Acids Res 2020; 47:11771-11789. [PMID: 31722409 PMCID: PMC7145601 DOI: 10.1093/nar/gkz1053] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Revised: 10/21/2019] [Accepted: 10/24/2019] [Indexed: 12/18/2022] Open
Abstract
Rediscovered as a potential eukaryotic epigenetic mark, DNA N6-adenine methylation (6mA) varies across species in abundance and its relationships with transcription. Here we characterize AMT1—representing a distinct MT-A70 family methyltransferase—in the ciliate Tetrahymena thermophila. AMT1 loss-of-function leads to severe defects in growth and development. Single Molecule, Real-Time (SMRT) sequencing reveals that AMT1 is required for the bulk of 6mA and all symmetric methylation at the ApT dinucleotides. The detection of hemi-methylated ApT sites suggests a semi-conservative mechanism for maintaining symmetric methylation. AMT1 affects expression of many genes; in particular, RAB46, encoding a Rab family GTPase involved in contractile vacuole function, is likely a direct target. The distribution of 6mA resembles H3K4 methylation and H2A.Z, two conserved epigenetic marks associated with RNA polymerase II transcription. Furthermore, strong 6mA and nucleosome positioning in wild-type cells is attenuated in ΔAMT1 cells. Our results support that AMT1-catalyzed 6mA is an integral part of the transcription-associated epigenetic landscape. AMT1 homologues are generally found in protists and basal fungi featuring ApT hyper-methylation associated with transcription, which are missing in animals, plants, and true fungi. This dichotomy of 6mA functions and the underlying molecular mechanisms may have implications in eukaryotic diversification.
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Affiliation(s)
- Yuanyuan Wang
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Yalan Sheng
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Yongqiang Liu
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Wenxin Zhang
- School of Life Science, Anhui Agricultural University, Hefei 230036, China
| | - Ting Cheng
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Lili Duan
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Bo Pan
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Yu Qiao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Yifan Liu
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Shan Gao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
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17
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Martin EC, Vicari C, Tsakou-Ngouafo L, Pontarotti P, Petrescu AJ, Schatz DG. Identification of RAG-like transposons in protostomes suggests their ancient bilaterian origin. Mob DNA 2020; 11:17. [PMID: 32399063 PMCID: PMC7204232 DOI: 10.1186/s13100-020-00214-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 04/14/2020] [Indexed: 12/27/2022] Open
Abstract
Background V(D) J recombination is essential for adaptive immunity in jawed vertebrates and is initiated by the RAG1-RAG2 endonuclease. The RAG1 and RAG2 genes are thought to have evolved from a RAGL (RAG-like) transposon containing convergently-oriented RAG1-like (RAG1L) and RAG2-like (RAG2L) genes. Elements resembling this presumptive evolutionary precursor have thus far only been detected convincingly in deuterostomes, leading to the model that the RAGL transposon first appeared in an early deuterostome. Results We have identified numerous RAGL transposons in the genomes of protostomes, including oysters and mussels (phylum Mollusca) and a ribbon worm (phylum Nemertea), and in the genomes of several cnidarians. Phylogenetic analyses are consistent with vertical evolution of RAGL transposons within the Bilateria clade and with its presence in the bilaterian ancestor. Many of the RAGL transposons identified in protostomes are intact elements containing convergently oriented RAG1L and RAG2L genes flanked by terminal inverted repeats (TIRs) and target site duplications with striking similarities with the corresponding elements in deuterostomes. In addition, protostome genomes contain numerous intact RAG1L-RAG2L adjacent gene pairs that lack detectable flanking TIRs. Domains and critical active site and structural amino acids needed for endonuclease and transposase activity are present and conserved in many of the predicted RAG1L and RAG2L proteins encoded in protostome genomes. Conclusions Active RAGL transposons were present in multiple protostome lineages and many were likely transmitted vertically during protostome evolution. It appears that RAGL transposons were broadly active during bilaterian evolution, undergoing multiple duplication and loss/fossilization events, with the RAGL genes that persist in present day protostomes perhaps constituting both active RAGL transposons and domesticated RAGL genes. Our findings raise the possibility that the RAGL transposon arose earlier in evolution than previously thought, either in an early bilaterian or prior to the divergence of bilaterians and non-bilaterians, and alter our understanding of the evolutionary history of this important group of transposons.
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Affiliation(s)
- Eliza C Martin
- 1Department of Bioinformatics and Structural Biochemistry, Institute of Biochemistry of the Romanian Academy, Splaiul Independentei 296, 060031 Bucharest, Romania
| | - Célia Vicari
- 2Evolutionary biology team, Aix Marseille Université IRD, APHM, MEPHI, IHU Méditerranée Infection, Marseille, France
| | - Louis Tsakou-Ngouafo
- 2Evolutionary biology team, Aix Marseille Université IRD, APHM, MEPHI, IHU Méditerranée Infection, Marseille, France
| | - Pierre Pontarotti
- 2Evolutionary biology team, Aix Marseille Université IRD, APHM, MEPHI, IHU Méditerranée Infection, Marseille, France.,SNC5039 CNRS, 19-21 Boulevard Jean Moulin, 13005 Marseille, France
| | - Andrei J Petrescu
- 1Department of Bioinformatics and Structural Biochemistry, Institute of Biochemistry of the Romanian Academy, Splaiul Independentei 296, 060031 Bucharest, Romania
| | - David G Schatz
- 4Department of Immunobiology, Yale School of Medicine, 300 Cedar Street, Box 208011, New Haven, CT 06520-8011 USA
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18
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Functional diversification of Paramecium Ku80 paralogs safeguards genome integrity during precise programmed DNA elimination. PLoS Genet 2020; 16:e1008723. [PMID: 32298257 PMCID: PMC7161955 DOI: 10.1371/journal.pgen.1008723] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 03/18/2020] [Indexed: 11/19/2022] Open
Abstract
Gene duplication and diversification drive the emergence of novel functions during evolution. Because of whole genome duplications, ciliates from the Paramecium aurelia group constitute a remarkable system to study the evolutionary fate of duplicated genes. Paramecium species harbor two types of nuclei: a germline micronucleus (MIC) and a somatic macronucleus (MAC) that forms from the MIC at each sexual cycle. During MAC development, ~45,000 germline Internal Eliminated Sequences (IES) are excised precisely from the genome through a 'cut-and-close' mechanism. Here, we have studied the P. tetraurelia paralogs of KU80, which encode a key DNA double-strand break repair factor involved in non-homologous end joining. The three KU80 genes have different transcription patterns, KU80a and KU80b being constitutively expressed, while KU80c is specifically induced during MAC development. Immunofluorescence microscopy and high-throughput DNA sequencing revealed that Ku80c stably anchors the PiggyMac (Pgm) endonuclease in the developing MAC and is essential for IES excision genome-wide, providing a molecular explanation for the previously reported Ku-dependent licensing of DNA cleavage at IES ends. Expressing Ku80a under KU80c transcription signals failed to complement a depletion of endogenous Ku80c, indicating that the two paralogous proteins have distinct properties. Domain-swap experiments identified the α/β domain of Ku80c as the major determinant for its specialized function, while its C-terminal part is required for excision of only a small subset of IESs located in IES-dense regions. We conclude that Ku80c has acquired the ability to license Pgm-dependent DNA cleavage, securing precise DNA elimination during programmed rearrangements. The present study thus provides novel evidence for functional diversification of genes issued from a whole-genome duplication.
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19
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The completed macronuclear genome of a model ciliate Tetrahymena thermophila and its application in genome scrambling and copy number analyses. SCIENCE CHINA-LIFE SCIENCES 2020; 63:1534-1542. [PMID: 32297047 DOI: 10.1007/s11427-020-1689-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 03/26/2020] [Indexed: 01/03/2023]
Abstract
The ciliate Tetrahymena thermophila has been a powerful model system for molecular and cellular biology. However, some investigations have been limited due to the incomplete closure and sequencing of the macronuclear genome assembly, which for many years has been stalled at 1,158 scaffolds, with large sections of unknown sequences (available in Tetrahymena Genome Database, TGD, http://ciliate.org/ ). Here we completed the first chromosome-level Tetrahymena macronuclear genome assembly, with approximately 300× long Single Molecule, Real-Time reads of the wild-type SB210 cells-the reference strain for the initial macronuclear genome sequencing project. All 181 chromosomes were capped with two telomeres and gaps were entirely closed. The completed genome shows significant improvements over the current assembly (TGD 2014) in both chromosome structure and sequence integrity. The majority of previously identified gene models shown in TGD were retained, with the addition of 36 new genes and 883 genes with modified gene models. The new genome and annotation were incorporated into TGD. This new genome allows for pursuit in some underexplored areas that were far more challenging previously; two of them, genome scrambling and chromosomal copy number, were investigated in this study. We expect that the completed macronuclear genome will facilitate many studies in Tetrahymena biology, as well as multiple lines of research in other eukaryotes.
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20
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Jaspan VN, Taye ME, Carle CM, Chung JJ, Chalker DL. Boundaries of eliminated heterochromatin of Tetrahymena are positioned by the DNA-binding protein Ltl1. Nucleic Acids Res 2019; 47:7348-7362. [PMID: 31194876 PMCID: PMC6698652 DOI: 10.1093/nar/gkz504] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 05/16/2019] [Accepted: 06/10/2019] [Indexed: 12/19/2022] Open
Abstract
During differentiation of the Tetrahymena thermophila somatic nucleus, its germline-derived DNA undergoes extensive reorganization including the removal of ∼50 Mb from thousands of loci called internal eliminated sequences (IESs). IES-associated chromatin is methylated on lysines 9 and 27 of histone H3, marking newly formed heterochromatin for elimination. To ensure that this reorganized genome maintains essential coding and regulatory sequences, the boundaries of IESs must be accurately defined. In this study, we show that the developmentally expressed protein encoded by Lia3-Like 1 (LTL1) (Ttherm_00499370) is necessary to direct the excision boundaries of particular IESs. In ΔLTL1 cells, boundaries of eliminated loci are aberrant and heterogeneous. The IESs regulated by Ltl1 are distinct from those regulated by the guanine-quadruplex binding Lia3 protein. Ltl1 has a general affinity for double stranded DNA (Kd ∼ 350 nM) and binds specifically to a 50 bp A+T rich sequence flanking each side of the D IES (Kd ∼ 43 nM). Together these data reveal that Ltl1 and Lia3 control different subsets of IESs and that their mechanisms for flanking sequence recognition are distinct.
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Affiliation(s)
- Vita N Jaspan
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Marta E Taye
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Christine M Carle
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Joyce J Chung
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Douglas L Chalker
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
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21
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Bétermier M, Borde V, de Villartay JP. Coupling DNA Damage and Repair: an Essential Safeguard during Programmed DNA Double-Strand Breaks? Trends Cell Biol 2019; 30:87-96. [PMID: 31818700 DOI: 10.1016/j.tcb.2019.11.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/15/2019] [Accepted: 11/18/2019] [Indexed: 12/31/2022]
Abstract
DNA double-strand breaks (DSBs) are the most toxic DNA lesions given their oncogenic potential. Nevertheless, programmed DSBs (prDSBs) contribute to several biological processes. Formation of prDSBs is the 'price to pay' to achieve these essential biological functions. Generated by domesticated PiggyBac transposases, prDSBs have been integrated in the life cycle of ciliates. Created by Spo11 during meiotic recombination, they constitute a driving force of evolution and ensure balanced chromosome content for successful reproduction. Produced by the RAG1/2 recombinase, they are required for the development of the adaptive immune system in many species. The coevolution of processes that couple introduction of prDSBs to their accurate repair may constitute an effective safeguard against genomic instability.
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Affiliation(s)
- Mireille Bétermier
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France.
| | - Valérie Borde
- Institut Curie, CNRS UMR3244, Sorbonne Université, Paris, France.
| | - Jean-Pierre de Villartay
- Laboratory of Genome Dynamics in the Immune System, INSERM UMR1163, Université Paris Descartes Sorbonne Paris Cité, Institut Imagine, Paris, France.
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22
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Zhu J, Zhang Y, Deng J, Jiang H, Zhuang L, Ye W, Ma J, Jiang J, Feng L. Diketopiperazines Synthesis Gene in Shewanella baltica and Roles of Diketopiperazines and Resveratrol in Quorum Sensing. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:12013-12025. [PMID: 31589428 DOI: 10.1021/acs.jafc.9b04620] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The synthesis pathways of quorum sensing (QS) signal molecules and the mechanism of action of quorum sensing inhibitors (QSIs) have gained considerable attention as research topics in the field of food preservation. Here, Shewanella baltica was detected as the specific spoilage organism in large yellow croaker during 4 °C storage, and it produced the QS signal molecules autoinducer-2 (AI-2) and diketopiperazines (DKPs). Then, a cyclodipeptide synthase (CDPS) homologous gene, sb1370, was screened, and knockout and rescue results revealed that this gene was involved in DKP synthesis but not in AI-2 synthesis, and it also played an important role in QS. Furthermore, fish fillets and mutant strains were treated with resveratrol, and the results suggested that resveratrol was an ideal QSI for inhibition of DKPs production via the sb1370 gene and reduced QS in S. baltica, thus delaying the process of fish spoilage during chilling storage.
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Affiliation(s)
- Junli Zhu
- College of Food Science and Biotechnology , Zhejiang Gongshang University , Hangzhou 310018 , PR China
| | - Yuwei Zhang
- College of Food Science and Biotechnology , Zhejiang Gongshang University , Hangzhou 310018 , PR China
| | - Jingmin Deng
- College of Food Science and Biotechnology , Zhejiang Gongshang University , Hangzhou 310018 , PR China
| | - Hanyun Jiang
- College of Food Science and Biotechnology , Zhejiang Gongshang University , Hangzhou 310018 , PR China
| | - Liumin Zhuang
- College of Food Science and Biotechnology , Zhejiang Gongshang University , Hangzhou 310018 , PR China
| | - Wei Ye
- College of Food Science and Biotechnology , Zhejiang Gongshang University , Hangzhou 310018 , PR China
| | - Jiayu Ma
- College of Food Science and Biotechnology , Zhejiang Gongshang University , Hangzhou 310018 , PR China
| | - Jingyang Jiang
- College of Food Science and Biotechnology , Zhejiang Gongshang University , Hangzhou 310018 , PR China
| | - Lifang Feng
- College of Food Science and Biotechnology , Zhejiang Gongshang University , Hangzhou 310018 , PR China
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23
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Clay DM, Yerlici VT, Villano DJ, Landweber LF. Programmed Chromosome Deletion in the Ciliate Oxytricha trifallax. G3 (BETHESDA, MD.) 2019; 9:3105-3118. [PMID: 31506317 PMCID: PMC6778801 DOI: 10.1534/g3.118.200930] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 05/28/2019] [Indexed: 01/18/2023]
Abstract
The ciliate Oxytricha trifallax contains two nuclei: a germline micronucleus and a somatic macronucleus. These two nuclei diverge significantly in genomic structure. The micronucleus contains approximately 100 chromosomes of megabase scale, while the macronucleus contains 16,000 gene-sized, high ploidy "nanochromosomes." During its sexual cycle, a copy of the zygotic germline micronucleus develops into a somatic macronucleus via DNA excision and rearrangement. The rearrangement process is guided by multiple RNA-based pathways that program the epigenetic inheritance of sequences in the parental macronucleus of the subsequent generation. Here, we show that the introduction of synthetic DNA molecules homologous to a complete native nanochromosome during the rearrangement process results in either loss or heavy copy number reduction of the targeted nanochromosome in the macronucleus of the subsequent generation. This phenomenon was tested on a variety of nanochromosomes with different micronuclear structures, with deletions resulting in all cases. Deletion of the targeted nanochromosome results in the loss of expression of the targeted genes, including gene knockout phenotypes that were phenocopied using alternative knockdown approaches. Further investigation of the chromosome deletion showed that, although the full length nanochromosome was lost, remnants of the targeted chromosome remain. We were also able to detect the presence of telomeres on these remnants. The chromosome deletions and remnants are epigenetically inherited when backcrossed to wild type strains, suggesting that an undiscovered mechanism programs DNA elimination and cytoplasmically transfers to both daughter cells during conjugation. Programmed deletion of targeted chromosomes provides a novel approach to investigate genome rearrangement and expands the available strategies for gene knockout in Oxytricha trifallax.
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Affiliation(s)
- Derek M Clay
- Departments of Biochemistry and Molecular Biophysics and Biological Sciences, Columbia University, New York, NY and
- Department of Molecular Biology, Princeton University, Princeton, NJ
| | - V Talya Yerlici
- Departments of Biochemistry and Molecular Biophysics and Biological Sciences, Columbia University, New York, NY and
- Department of Molecular Biology, Princeton University, Princeton, NJ
| | - Danylo J Villano
- Departments of Biochemistry and Molecular Biophysics and Biological Sciences, Columbia University, New York, NY and
| | - Laura F Landweber
- Departments of Biochemistry and Molecular Biophysics and Biological Sciences, Columbia University, New York, NY and
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24
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Abstract
Transposable elements (TEs) are mobile DNA sequences that colonize genomes and threaten genome integrity. As a result, several mechanisms appear to have emerged during eukaryotic evolution to suppress TE activity. However, TEs are ubiquitous and account for a prominent fraction of most eukaryotic genomes. We argue that the evolutionary success of TEs cannot be explained solely by evasion from host control mechanisms. Rather, some TEs have evolved commensal and even mutualistic strategies that mitigate the cost of their propagation. These coevolutionary processes promote the emergence of complex cellular activities, which in turn pave the way for cooption of TE sequences for organismal function.
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Affiliation(s)
- Rachel L Cosby
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
| | - Ni-Chen Chang
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
| | - Cédric Feschotte
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
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25
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Tian M, Mochizuki K, Loidl J. Non-coding RNA Transcription in Tetrahymena Meiotic Nuclei Requires Dedicated Mediator Complex-Associated Proteins. Curr Biol 2019; 29:2359-2370.e5. [PMID: 31280995 DOI: 10.1016/j.cub.2019.05.038] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 04/24/2019] [Accepted: 05/15/2019] [Indexed: 12/22/2022]
Abstract
To preserve genome integrity, eukaryotic cells use small RNA-directed mechanisms to repress transposable elements (TEs). Paradoxically, in order to silence TEs, precursors of the small RNAs must be transcribed from TEs. However, it is still poorly understood how these precursors are transcribed from TEs under silenced conditions. In the otherwise transcriptionally silent germline micronucleus (MIC) of Tetrahymena, a burst of non-coding RNA (ncRNA) transcription occurs during meiosis. The transcripts are processed into small RNAs that serve to identify TE-related sequences for elimination. The Mediator complex (Med) has an evolutionarily conserved role for transcription by bridging gene-specific transcription factors and RNA polymerase II. Here, we report that three Med-associated factors, Emit1, Emit2, and Rib1, are required for the biogenesis of small ncRNAs. Med localizes to the MIC only during meiosis, and both Med localization and MIC ncRNA transcription require Emit1 and Emit2. In the MIC, Med occupies TE-rich pericentromeric and telomeric regions in a Rib1-dependent manner. Rib1 is dispensable for ncRNA transcription but is required for the accumulation of double-stranded ncRNAs. Nuclear and sub-nuclear localization of the three Med-associated proteins is interdependent. Hence, Emit1 and Emit2 act coordinately to import Med into the MIC, and Rib1 recruits Med to specific chromosomal locations to quantitatively or qualitatively promote the biogenesis of functional ncRNA. Our results underscore that the transcription machinery can be regulated by a set of specialized Med-associated proteins to temporally transcribe TE-related sequences from a silent genome for small RNA biogenesis and genome defense.
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Affiliation(s)
- Miao Tian
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria.
| | - Kazufumi Mochizuki
- Institute of Human Genetics (IGH), CNRS, University of Montpellier, 34090 Montpellier, France
| | - Josef Loidl
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
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26
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Diversification of small RNA amplification mechanisms for targeting transposon-related sequences in ciliates. Proc Natl Acad Sci U S A 2019; 116:14639-14644. [PMID: 31262823 DOI: 10.1073/pnas.1903491116] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The silencing of repetitive transposable elements (TEs) is ensured by signal amplification of the initial small RNA trigger, which occurs at distinct steps of TE silencing in different eukaryotes. How such a variety of secondary small RNA biogenesis mechanisms has evolved has not been thoroughly elucidated. Ciliated protozoa perform small RNA-directed programmed DNA elimination of thousands of TE-related internal eliminated sequences (IESs) in the newly developed somatic nucleus. In the ciliate Paramecium, secondary small RNAs are produced after the excision of IESs. In this study, we show that in another ciliate, Tetrahymena, secondary small RNAs accumulate at least a few hours before their derived IESs are excised. We also demonstrate that DNA excision is dispensable for their biogenesis in this ciliate. Therefore, unlike in Paramecium, small RNA amplification occurs before IES excision in Tetrahymena This study reveals the remarkable diversity of secondary small RNA biogenesis mechanisms, even among ciliates with similar DNA elimination processes, and thus raises the possibility that the evolution of TE-targeting small RNA amplification can be traced by investigating the DNA elimination mechanisms of ciliates.
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27
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Chen K, Wang G, Xiong J, Jiang C, Miao W. Exploration of Genetic Variations through Single-cell Whole-genome Sequencing in the Model Ciliate Tetrahymena thermophila. J Eukaryot Microbiol 2019; 66:954-965. [PMID: 31188517 DOI: 10.1111/jeu.12746] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 05/05/2019] [Accepted: 05/30/2019] [Indexed: 01/05/2023]
Abstract
Ciliates are unicellular eukaryotes with separate germline and somatic genomes and diverse life cycles, which make them a unique model to improve our understanding of population genetics through the detection of genetic variations. However, traditional sequencing methods cannot be directly applied to ciliates because the majority are uncultivated. Single-cell whole-genome sequencing (WGS) is a powerful tool for studying genetic variation in microbes, but no studies have been performed in ciliates. We compared the use of single-cell WGS and bulk DNA WGS to detect genetic variation, specifically single nucleotide polymorphisms (SNPs), in the model ciliate Tetrahymena thermophila. Our analyses showed that (i) single-cell WGS has excellent performance regarding mapping rate and genome coverage but lower sequencing uniformity compared with bulk DNA WGS due to amplification bias (which was reproducible); (ii) false-positive SNP sites detected by single-cell WGS tend to occur in genomic regions with particularly high sequencing depth and high rate of C:G to T:A base changes; (iii) SNPs detected in three or more cells should be reliable (an detection efficiency of 83.4-97.4% was obtained for combined data from three cells). This analytical method could be adapted to measure genetic variation in other ciliates and broaden research into ciliate population genetics.
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Affiliation(s)
- Kai Chen
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Guangying Wang
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Jie Xiong
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Chuanqi Jiang
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Wei Miao
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.,University of Chinese Academy of Sciences, Beijing, 100049, China.,State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.,CAS Center for Excellence in Animal Evolution and Genetics, Kunming, 650223, China
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28
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Chen X, Jiang Y, Gao F, Zheng W, Krock TJ, Stover NA, Lu C, Katz LA, Song W. Genome analyses of the new model protist Euplotes vannus focusing on genome rearrangement and resistance to environmental stressors. Mol Ecol Resour 2019; 19:1292-1308. [PMID: 30985983 DOI: 10.1111/1755-0998.13023] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 04/05/2019] [Accepted: 04/08/2019] [Indexed: 12/11/2022]
Abstract
As a model organism for studies of cell and environmental biology, the free-living and cosmopolitan ciliate Euplotes vannus shows intriguing features like dual genome architecture (i.e., separate germline and somatic nuclei in each cell/organism), "gene-sized" chromosomes, stop codon reassignment, programmed ribosomal frameshifting (PRF) and strong resistance to environmental stressors. However, the molecular mechanisms that account for these remarkable traits remain largely unknown. Here we report a combined analysis of de novo assembled high-quality macronuclear (MAC; i.e., somatic) and partial micronuclear (MIC; i.e., germline) genome sequences for E. vannus, and transcriptome profiling data under varying conditions. The results demonstrate that: (a) the MAC genome contains more than 25,000 complete "gene-sized" nanochromosomes (~85 Mb haploid genome size) with the N50 ~2.7 kb; (b) although there is a high frequency of frameshifting at stop codons UAA and UAG, we did not observe impaired transcript abundance as a result of PRF in this species as has been reported for other euplotids; (c) the sequence motif 5'-TA-3' is conserved at nearly all internally-eliminated sequence (IES) boundaries in the MIC genome, and chromosome breakage sites (CBSs) are duplicated and retained in the MAC genome; (d) by profiling the weighted correlation network of genes in the MAC under different environmental stressors, including nutrient scarcity, extreme temperature, salinity and the presence of ammonia, we identified gene clusters that respond to these external physical or chemical stimulations, and (e) we observed a dramatic increase in HSP70 gene transcription under salinity and chemical stresses but surprisingly, not under temperature changes; we link this temperature-resistance to the evolved loss of temperature stress-sensitive elements in regulatory regions. Together with the genome resources generated in this study, which are available online at Euplotes vannus Genome Database (http://evan.ciliate.org), these data provide molecular evidence for understanding the unique biology of highly adaptable microorganisms.
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Affiliation(s)
- Xiao Chen
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China.,Department of Genetics and Development, Columbia University Medical Center, New York, New York
| | - Yaohan Jiang
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China
| | - Feng Gao
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China.,Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, China
| | - Weibo Zheng
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China
| | - Timothy J Krock
- Department of Computer Science and Information Systems, Bradley University, Peoria, Illinois
| | - Naomi A Stover
- Department of Biology, Bradley University, Peoria, Illinois
| | - Chao Lu
- Department of Genetics and Development, Columbia University Medical Center, New York, New York
| | - Laura A Katz
- Department of Biological Sciences, Smith College, Northampton, Massachusetts
| | - Weibo Song
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
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29
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Lin CYG, Chao JL, Tsai HK, Chalker D, Yao MC. Setting boundaries for genome-wide heterochromatic DNA deletions through flanking inverted repeats in Tetrahymena thermophila. Nucleic Acids Res 2019; 47:5181-5192. [PMID: 30918956 PMCID: PMC6547420 DOI: 10.1093/nar/gkz209] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 03/03/2019] [Accepted: 03/26/2019] [Indexed: 12/13/2022] Open
Abstract
Eukaryotic cells pack their genomic DNA into euchromatin and heterochromatin. Boundaries between these domains have been shown to be set by boundary elements. In Tetrahymena, heterochromatin domains are targeted for deletion from the somatic nuclei through a sophisticated programmed DNA rearrangement mechanism, resulting in the elimination of 34% of the germline genome in ∼10,000 dispersed segments. Here we showed that most of these deletions occur consistently with very limited variations in their boundaries among inbred lines. We identified several potential flanking regulatory sequences, each associated with a subset of deletions, using a genome-wide motif finding approach. These flanking sequences are inverted repeats with the copies located at nearly identical distances from the opposite ends of the deleted regions, suggesting potential roles in boundary determination. By removing and testing two such inverted repeats in vivo, we found that the ability for boundary maintenance of the associated deletion were lost. Furthermore, we analyzed the deletion boundaries in mutants of a known boundary-determining protein, Lia3p and found that the subset of deletions that are affected by LIA3 knockout contained common features of flanking regulatory sequences. This study suggests a common mechanism for setting deletion boundaries by flanking inverted repeats in Tetrahymena thermophila.
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Affiliation(s)
- Chih-Yi Gabriela Lin
- Institute of Molecular Biology, Academia Sinica, 11529 Taipei, Taiwan
- Genome and Systems Biology Degree Program, National Taiwan University, 10617 Taipei, Taiwan
| | - Ju-Lan Chao
- Institute of Molecular Biology, Academia Sinica, 11529 Taipei, Taiwan
| | - Huai-Kuang Tsai
- Genome and Systems Biology Degree Program, National Taiwan University, 10617 Taipei, Taiwan
- Institute of Information Science, Academia Sinica, 11529 Taipei, Taiwan
| | - Douglas Chalker
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Meng-Chao Yao
- Institute of Molecular Biology, Academia Sinica, 11529 Taipei, Taiwan
- Genome and Systems Biology Degree Program, National Taiwan University, 10617 Taipei, Taiwan
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30
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Maurer-Alcalá XX, Nowacki M. Evolutionary origins and impacts of genome architecture in ciliates. Ann N Y Acad Sci 2019; 1447:110-118. [PMID: 31074010 PMCID: PMC6767857 DOI: 10.1111/nyas.14108] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 03/18/2019] [Accepted: 04/03/2019] [Indexed: 01/24/2023]
Abstract
Genome architecture is well diversified among eukaryotes in terms of size and content, with many being radically shaped by ancient and ongoing genome conflicts with transposable elements (e.g., the large transposon‐rich genomes common among plants). In ciliates, a group of microbial eukaryotes with distinct somatic and germ‐line genomes present in a single cell, the consequences of these genome conflicts are most apparent in their developmentally programmed genome rearrangements. This complicated developmental phenomenon has largely overshadowed and outpaced our understanding of how germ‐line and somatic genome architectures have influenced the evolutionary dynamism and potential in these taxa. In our review, we highlight three central concepts: how the evolution of atypical ciliate germ‐line genome architectures is linked to ancient genome conflicts; how the complex, epigenetically guided transformation of germline to soma during development can generate widespread genetic variation; and how these features, coupled with their unusual life cycle, have increased the rate of molecular evolution linked to genome architecture in these taxa.
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Affiliation(s)
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Bern, Switzerland
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31
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Zhao X, Xiong J, Mao F, Sheng Y, Chen X, Feng L, Dui W, Yang W, Kapusta A, Feschotte C, Coyne RS, Miao W, Gao S, Liu Y. RNAi-dependent Polycomb repression controls transposable elements in Tetrahymena. Genes Dev 2019; 33:348-364. [PMID: 30808657 PMCID: PMC6411011 DOI: 10.1101/gad.320796.118] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 01/02/2019] [Indexed: 12/30/2022]
Abstract
In this study, Zhao et al. show that in the protozoan Tetrahymena thermophila, germline-specific internally eliminated sequences (IESs) become transcriptionally activated in mutants deficient in the RNAi-dependent Polycomb repression pathway. Their findings suggest that the interplay between RNAi and Polycomb repression is a widely conserved phenomenon whose ancestral role is epigenetic silencing of TEs. RNAi and Polycomb repression play evolutionarily conserved and often coordinated roles in transcriptional silencing. Here, we show that, in the protozoan Tetrahymena thermophila, germline-specific internally eliminated sequences (IESs)—many related to transposable elements (TEs)—become transcriptionally activated in mutants deficient in the RNAi-dependent Polycomb repression pathway. Germline TE mobilization also dramatically increases in these mutants. The transition from noncoding RNA (ncRNA) to mRNA production accompanies transcriptional activation of TE-related sequences and vice versa for transcriptional silencing. The balance between ncRNA and mRNA production is potentially affected by cotranscriptional processing as well as RNAi and Polycomb repression. We posit that interplay between RNAi and Polycomb repression is a widely conserved phenomenon, whose ancestral role is epigenetic silencing of TEs.
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Affiliation(s)
- Xiaolu Zhao
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA.,Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China
| | - Jie Xiong
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Fengbiao Mao
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Yalan Sheng
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China
| | - Xiao Chen
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA.,Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China
| | - Lifang Feng
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Wen Dui
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Wentao Yang
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Aurélie Kapusta
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah 84112, USA
| | - Cédric Feschotte
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14850, USA
| | - Robert S Coyne
- J. Craig Venter Institute, Rockville, Maryland 20850, USA
| | - Wei Miao
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Shan Gao
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China
| | - Yifan Liu
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA
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32
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Bischerour J, Bhullar S, Denby Wilkes C, Régnier V, Mathy N, Dubois E, Singh A, Swart E, Arnaiz O, Sperling L, Nowacki M, Bétermier M. Six domesticated PiggyBac transposases together carry out programmed DNA elimination in Paramecium. eLife 2018; 7:37927. [PMID: 30223944 PMCID: PMC6143343 DOI: 10.7554/elife.37927] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 08/29/2018] [Indexed: 02/06/2023] Open
Abstract
The domestication of transposable elements has repeatedly occurred during evolution and domesticated transposases have often been implicated in programmed genome rearrangements, as remarkably illustrated in ciliates. In Paramecium, PiggyMac (Pgm), a domesticated PiggyBac transposase, carries out developmentally programmed DNA elimination, including the precise excision of tens of thousands of gene-interrupting germline Internal Eliminated Sequences (IESs). Here, we report the discovery of five groups of distant Pgm-like proteins (PgmLs), all able to interact with Pgm and essential for its nuclear localization and IES excision genome-wide. Unlike Pgm, PgmLs lack a conserved catalytic site, suggesting that they rather have an architectural function within a multi-component excision complex embedding Pgm. PgmL depletion can increase erroneous targeting of residual Pgm-mediated DNA cleavage, indicating that PgmLs contribute to accurately position the complex on IES ends. DNA rearrangements in Paramecium constitute a rare example of a biological process jointly managed by six distinct domesticated transposases.
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Affiliation(s)
- Julien Bischerour
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Simran Bhullar
- Institute of Cell Biology, University of Bern, Bern, Switzerland.,Institut de Biologie de l'Ecole Normale Supérieure, Paris, France
| | - Cyril Denby Wilkes
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Vinciane Régnier
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France.,Univ Paris Diderot, Paris, France
| | - Nathalie Mathy
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Emeline Dubois
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Aditi Singh
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Estienne Swart
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Olivier Arnaiz
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Linda Sperling
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Mireille Bétermier
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
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Noto T, Mochizuki K. Whats, hows and whys of programmed DNA elimination in Tetrahymena. Open Biol 2018; 7:rsob.170172. [PMID: 29021213 PMCID: PMC5666084 DOI: 10.1098/rsob.170172] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 09/12/2017] [Indexed: 12/20/2022] Open
Abstract
Programmed genome rearrangements in ciliates provide fascinating examples of flexible epigenetic genome regulations and important insights into the interaction between transposable elements (TEs) and host genomes. DNA elimination in Tetrahymena thermophila removes approximately 12 000 internal eliminated sequences (IESs), which correspond to one-third of the genome, when the somatic macronucleus (MAC) differentiates from the germline micronucleus (MIC). More than half of the IESs, many of which show high similarity to TEs, are targeted for elimination in cis by the small RNA-mediated genome comparison of the MIC to the MAC. Other IESs are targeted for elimination in trans by the same small RNAs through repetitive sequences. Furthermore, the small RNA–heterochromatin feedback loop ensures robust DNA elimination. Here, we review an updated picture of the DNA elimination mechanism, discuss the physiological and evolutionary roles of DNA elimination, and outline the key questions that remain unanswered.
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Affiliation(s)
- Tomoko Noto
- Institute of Human Genetics, UMR 9002, CNRS and University of Montpellier, Montpellier, France
| | - Kazufumi Mochizuki
- Institute of Human Genetics, UMR 9002, CNRS and University of Montpellier, Montpellier, France
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