1
|
Lau NC, Macias VM. Transposon and Transgene Tribulations in Mosquitoes: A Perspective of piRNA Proportions. DNA 2024; 4:104-128. [PMID: 39076684 PMCID: PMC11286205 DOI: 10.3390/dna4020006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/31/2024]
Abstract
Mosquitoes, like Drosophila, are dipterans, the order of "true flies" characterized by a single set of two wings. Drosophila are prime model organisms for biomedical research, while mosquito researchers struggle to establish robust molecular biology in these that are arguably the most dangerous vectors of human pathogens. Both insects utilize the RNA interference (RNAi) pathway to generate small RNAs to silence transposons and viruses, yet details are emerging that several RNAi features are unique to each insect family, such as how culicine mosquitoes have evolved extreme genomic feature differences connected to their unique RNAi features. A major technical difference in the molecular genetic studies of these insects is that generating stable transgenic animals are routine in Drosophila but still variable in stability in mosquitoes, despite genomic DNA-editing advances. By comparing and contrasting the differences in the RNAi pathways of Drosophila and mosquitoes, in this review we propose a hypothesis that transgene DNAs are possibly more intensely targeted by mosquito RNAi pathways and chromatin regulatory pathways than in Drosophila. We review the latest findings on mosquito RNAi pathways, which are still much less well understood than in Drosophila, and we speculate that deeper study into how mosquitoes modulate transposons and viruses with Piwi-interacting RNAs (piRNAs) will yield clues to improving transgene DNA expression stability in transgenic mosquitoes.
Collapse
Affiliation(s)
- Nelson C. Lau
- Department of Biochemistry and Cell Biology, Boston University Chobanian and Avedisian School of Medicine, Boston, MA 02118, USA
- Genome Science Institute and National Emerging Infectious Disease Laboratory, Boston University Chobanian and Avedisian School of Medicine, Boston, MA 02118, USA
| | - Vanessa M. Macias
- Department of Biology, University of North Texas, Denton, TX 76205, USA
- Advanced Environmental Research Institute, University of North Texas, Denton, TX 76205, USA
| |
Collapse
|
2
|
Asif-Laidin A, Casier K, Ziriat Z, Boivin A, Viodé E, Delmarre V, Ronsseray S, Carré C, Teysset L. Modeling early germline immunization after horizontal transfer of transposable elements reveals internal piRNA cluster heterogeneity. BMC Biol 2023; 21:117. [PMID: 37226160 DOI: 10.1186/s12915-023-01616-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 05/05/2023] [Indexed: 05/26/2023] Open
Abstract
BACKGROUND A fraction of all genomes is composed of transposable elements (TEs) whose mobility needs to be carefully controlled. In gonads, TE activity is repressed by PIWI-interacting RNAs (piRNAs), a class of small RNAs synthesized by heterochromatic loci enriched in TE fragments, called piRNA clusters. Maintenance of active piRNA clusters across generations is secured by maternal piRNA inheritance providing the memory for TE repression. On rare occasions, genomes encounter horizontal transfer (HT) of new TEs with no piRNA targeting them, threatening the host genome integrity. Naïve genomes can eventually start to produce new piRNAs against these genomic invaders, but the timing of their emergence remains elusive. RESULTS Using a set of TE-derived transgenes inserted in different germline piRNA clusters and functional assays, we have modeled a TE HT in Drosophila melanogaster. We have found that the complete co-option of these transgenes by a germline piRNA cluster can occur within four generations associated with the production of new piRNAs all along the transgenes and the germline silencing of piRNA sensors. Synthesis of new transgenic TE piRNAs is linked to piRNA cluster transcription dependent on Moonshiner and heterochromatin mark deposition that propagates more efficiently on short sequences. Moreover, we found that sequences located within piRNA clusters can have different piRNA profiles and can influence transcript accumulation of nearby sequences. CONCLUSIONS Our study reveals that genetic and epigenetic properties, such as transcription, piRNA profiles, heterochromatin, and conversion efficiency along piRNA clusters, could be heterogeneous depending on the sequences that compose them. These findings suggest that the capacity of transcriptional signal erasure induced by the chromatin complex specific of the piRNA cluster can be incomplete through the piRNA cluster loci. Finally, these results have revealed an unexpected level of complexity that highlights a new magnitude of piRNA cluster plasticity fundamental for the maintenance of genome integrity.
Collapse
Affiliation(s)
- Amna Asif-Laidin
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, "Transgenerational Epigenetics & Small RNA Biology", Paris, F-75005, France
| | - Karine Casier
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, "Transgenerational Epigenetics & Small RNA Biology", Paris, F-75005, France
- Present Address: CNRS, Institut de Biologie Physico-Chimique, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, UMR8226, Telomere Biology, Paris, F-75005, France
| | - Zoheir Ziriat
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, "Transgenerational Epigenetics & Small RNA Biology", Paris, F-75005, France
| | - Antoine Boivin
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, "Transgenerational Epigenetics & Small RNA Biology", Paris, F-75005, France
| | - Elise Viodé
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, "Transgenerational Epigenetics & Small RNA Biology", Paris, F-75005, France
| | - Valérie Delmarre
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, "Transgenerational Epigenetics & Small RNA Biology", Paris, F-75005, France
| | - Stéphane Ronsseray
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, "Transgenerational Epigenetics & Small RNA Biology", Paris, F-75005, France
| | - Clément Carré
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, "Transgenerational Epigenetics & Small RNA Biology", Paris, F-75005, France
| | - Laure Teysset
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, "Transgenerational Epigenetics & Small RNA Biology", Paris, F-75005, France.
| |
Collapse
|
3
|
Casier K, Boivin A, Carré C, Teysset L. Environmentally-Induced Transgenerational Epigenetic Inheritance: Implication of PIWI Interacting RNAs. Cells 2019; 8:cells8091108. [PMID: 31546882 PMCID: PMC6770481 DOI: 10.3390/cells8091108] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 09/16/2019] [Accepted: 09/17/2019] [Indexed: 12/11/2022] Open
Abstract
Environmentally-induced transgenerational epigenetic inheritance is an emerging field. The understanding of associated epigenetic mechanisms is currently in progress with open questions still remaining. In this review, we present an overview of the knowledge of environmentally-induced transgenerational inheritance and associated epigenetic mechanisms, mainly in animals. The second part focuses on the role of PIWI-interacting RNAs (piRNAs), a class of small RNAs involved in the maintenance of the germline genome, in epigenetic memory to put into perspective cases of environmentally-induced transgenerational inheritance involving piRNA production. Finally, the last part addresses how genomes are facing production of new piRNAs, and from a broader perspective, how this process might have consequences on evolution and on sporadic disease development.
Collapse
Affiliation(s)
- Karine Casier
- Transgenerational Epigenetics & small RNA Biology, Sorbonne Université, CNRS, Laboratoire Biologie du Développement, Institut de Biologie Paris-Seine, UMR7622, 75005 Paris, France.
| | - Antoine Boivin
- Transgenerational Epigenetics & small RNA Biology, Sorbonne Université, CNRS, Laboratoire Biologie du Développement, Institut de Biologie Paris-Seine, UMR7622, 75005 Paris, France.
| | - Clément Carré
- Transgenerational Epigenetics & small RNA Biology, Sorbonne Université, CNRS, Laboratoire Biologie du Développement, Institut de Biologie Paris-Seine, UMR7622, 75005 Paris, France.
| | - Laure Teysset
- Transgenerational Epigenetics & small RNA Biology, Sorbonne Université, CNRS, Laboratoire Biologie du Développement, Institut de Biologie Paris-Seine, UMR7622, 75005 Paris, France.
| |
Collapse
|
4
|
Casier K, Delmarre V, Gueguen N, Hermant C, Viodé E, Vaury C, Ronsseray S, Brasset E, Teysset L, Boivin A. Environmentally-induced epigenetic conversion of a piRNA cluster. eLife 2019; 8:e39842. [PMID: 30875295 PMCID: PMC6420265 DOI: 10.7554/elife.39842] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 03/06/2019] [Indexed: 01/02/2023] Open
Abstract
Transposable element (TE) activity is repressed in animal gonads by PIWI-interacting RNAs (piRNAs) produced by piRNA clusters. Current models in flies propose that germinal piRNA clusters are functionally defined by the maternal inheritance of piRNAs produced during the previous generation. Taking advantage of an inactive, but ready to go, cluster of P-element derived transgene insertions in Drosophila melanogaster, we show here that raising flies at high temperature (29°C) instead of 25°C triggers the stable conversion of this locus from inactive into actively producing functional piRNAs. The increase of antisense transcripts from the cluster at 29°C combined with the requirement of transcription of euchromatic homologous sequences, suggests a role of double stranded RNA in the production of de novo piRNAs. This report describes the first case of the establishment of an active piRNA cluster by environmental changes in the absence of maternal inheritance of homologous piRNAs. Editorial note This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
Collapse
Affiliation(s)
- Karine Casier
- Laboratoire Biologie du Développement, UMR7622Sorbonne Université, CNRS, Institut de Biologie Paris-SeineParisFrance
| | - Valérie Delmarre
- Laboratoire Biologie du Développement, UMR7622Sorbonne Université, CNRS, Institut de Biologie Paris-SeineParisFrance
| | - Nathalie Gueguen
- GReDUniversité Clermont Auvergne, CNRS, INSERM, BP 10448Clermont-FerrandFrance
| | - Catherine Hermant
- Laboratoire Biologie du Développement, UMR7622Sorbonne Université, CNRS, Institut de Biologie Paris-SeineParisFrance
| | - Elise Viodé
- Laboratoire Biologie du Développement, UMR7622Sorbonne Université, CNRS, Institut de Biologie Paris-SeineParisFrance
| | - Chantal Vaury
- GReDUniversité Clermont Auvergne, CNRS, INSERM, BP 10448Clermont-FerrandFrance
| | - Stéphane Ronsseray
- Laboratoire Biologie du Développement, UMR7622Sorbonne Université, CNRS, Institut de Biologie Paris-SeineParisFrance
| | - Emilie Brasset
- GReDUniversité Clermont Auvergne, CNRS, INSERM, BP 10448Clermont-FerrandFrance
| | - Laure Teysset
- Laboratoire Biologie du Développement, UMR7622Sorbonne Université, CNRS, Institut de Biologie Paris-SeineParisFrance
| | - Antoine Boivin
- Laboratoire Biologie du Développement, UMR7622Sorbonne Université, CNRS, Institut de Biologie Paris-SeineParisFrance
| |
Collapse
|
5
|
Qiu GH, Huang C, Zheng X, Yang X. The protective function of noncoding DNA in genome defense of eukaryotic male germ cells. Epigenomics 2018; 10:499-517. [PMID: 29616594 DOI: 10.2217/epi-2017-0103] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Peripheral and abundant noncoding DNA has been hypothesized to protect the genome and the central protein-coding sequences against DNA damage in somatic genome. In the cytosol, invading exogenous nucleic acids may first be deactivated by small RNAs encoded by noncoding DNA via mechanisms similar to the prokaryotic CRISPR-Cas system. In the nucleus, the radicals generated by radiation in the cytosol, radiation energy and invading exogenous nucleic acids are absorbed, blocked and/or reduced by peripheral heterochromatin, and damaged DNA in heterochromatin is removed and excluded from the nucleus to the cytoplasm through nuclear pore complexes. To further strengthen the hypothesis, this review summarizes the experimental evidence supporting the protective function of noncoding DNA in the genome of male germ cells. Based on these data, this review provides evidence supporting the protective role of noncoding DNA in the genome defense of sperm genome through similar mechanisms to those of the somatic genome.
Collapse
Affiliation(s)
- Guo-Hua Qiu
- Fujian Provincial Key Laboratory for the Prevention & Control of Animal Infectious Diseases & Biotechnology; Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province University; College of Life Sciences, Longyan University, Longyan 364012, Fujian, PR China
| | - Cuiqin Huang
- Fujian Provincial Key Laboratory for the Prevention & Control of Animal Infectious Diseases & Biotechnology; Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province University; College of Life Sciences, Longyan University, Longyan 364012, Fujian, PR China
| | - Xintian Zheng
- Fujian Provincial Key Laboratory for the Prevention & Control of Animal Infectious Diseases & Biotechnology; Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province University; College of Life Sciences, Longyan University, Longyan 364012, Fujian, PR China
| | - Xiaoyan Yang
- Fujian Provincial Key Laboratory for the Prevention & Control of Animal Infectious Diseases & Biotechnology; Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province University; College of Life Sciences, Longyan University, Longyan 364012, Fujian, PR China
| |
Collapse
|
6
|
Hermant C, Boivin A, Teysset L, Delmarre V, Asif-Laidin A, van den Beek M, Antoniewski C, Ronsseray S. Paramutation in Drosophila Requires Both Nuclear and Cytoplasmic Actors of the piRNA Pathway and Induces Cis-spreading of piRNA Production. Genetics 2015; 201:1381-96. [PMID: 26482790 PMCID: PMC4676525 DOI: 10.1534/genetics.115.180307] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 10/05/2015] [Indexed: 01/24/2023] Open
Abstract
Transposable element activity is repressed in the germline in animals by PIWI-interacting RNAs (piRNAs), a class of small RNAs produced by genomic loci mostly composed of TE sequences. The mechanism of induction of piRNA production by these loci is still enigmatic. We have shown that, in Drosophila melanogaster, a cluster of tandemly repeated P-lacZ-white transgenes can be activated for piRNA production by maternal inheritance of a cytoplasm containing homologous piRNAs. This activated state is stably transmitted over generations and allows trans-silencing of a homologous transgenic target in the female germline. Such an epigenetic conversion displays the functional characteristics of a paramutation, i.e., a heritable epigenetic modification of one allele by the other. We report here that piRNA production and trans-silencing capacities of the paramutated cluster depend on the function of the rhino, cutoff, and zucchini genes involved in primary piRNA biogenesis in the germline, as well as on that of the aubergine gene implicated in the ping-pong piRNA amplification step. The 21-nt RNAs, which are produced by the paramutated cluster, in addition to 23- to 28-nt piRNAs are not necessary for paramutation to occur. Production of these 21-nt RNAs requires Dicer-2 but also all the piRNA genes tested. Moreover, cytoplasmic transmission of piRNAs homologous to only a subregion of the transgenic locus can generate a strong paramutated locus that produces piRNAs along the whole length of the transgenes. Finally, we observed that maternally inherited transgenic small RNAs can also impact transgene expression in the soma. In conclusion, paramutation involves both nuclear (Rhino, Cutoff) and cytoplasmic (Aubergine, Zucchini) actors of the piRNA pathway. In addition, since it is observed between nonfully homologous loci located on different chromosomes, paramutation may play a crucial role in epigenome shaping in Drosophila natural populations.
Collapse
Affiliation(s)
- Catherine Hermant
- Sorbonne Universités, UPMC University of Paris 06, Institut de Biologie Paris-Seine, UMR7622, Laboratoire Biologie du Développement, F-75005, Paris, France CNRS, UMR7622, "Epigenetic Repression and Mobile DNA," F-75005, Paris, France
| | - Antoine Boivin
- Sorbonne Universités, UPMC University of Paris 06, Institut de Biologie Paris-Seine, UMR7622, Laboratoire Biologie du Développement, F-75005, Paris, France CNRS, UMR7622, "Epigenetic Repression and Mobile DNA," F-75005, Paris, France
| | - Laure Teysset
- Sorbonne Universités, UPMC University of Paris 06, Institut de Biologie Paris-Seine, UMR7622, Laboratoire Biologie du Développement, F-75005, Paris, France CNRS, UMR7622, "Epigenetic Repression and Mobile DNA," F-75005, Paris, France
| | - Valérie Delmarre
- Sorbonne Universités, UPMC University of Paris 06, Institut de Biologie Paris-Seine, UMR7622, Laboratoire Biologie du Développement, F-75005, Paris, France CNRS, UMR7622, "Epigenetic Repression and Mobile DNA," F-75005, Paris, France
| | - Amna Asif-Laidin
- Sorbonne Universités, UPMC University of Paris 06, Institut de Biologie Paris-Seine, UMR7622, Laboratoire Biologie du Développement, F-75005, Paris, France CNRS, UMR7622, "Epigenetic Repression and Mobile DNA," F-75005, Paris, France
| | - Marius van den Beek
- Sorbonne Universités, UPMC University of Paris 06, Institut de Biologie Paris-Seine, UMR7622, Laboratoire Biologie du Développement, F-75005, Paris, France CNRS, UMR7622, "Drosophila Genetics and Epigenetics," F-75005, Paris, France CNRS, FR3631, Institut de Biologie Paris-Seine, ARTbio Bioinformatics Analysis Facility, F-75005, Paris, France
| | - Christophe Antoniewski
- Sorbonne Universités, UPMC University of Paris 06, Institut de Biologie Paris-Seine, UMR7622, Laboratoire Biologie du Développement, F-75005, Paris, France CNRS, UMR7622, "Drosophila Genetics and Epigenetics," F-75005, Paris, France CNRS, FR3631, Institut de Biologie Paris-Seine, ARTbio Bioinformatics Analysis Facility, F-75005, Paris, France
| | - Stéphane Ronsseray
- Sorbonne Universités, UPMC University of Paris 06, Institut de Biologie Paris-Seine, UMR7622, Laboratoire Biologie du Développement, F-75005, Paris, France CNRS, UMR7622, "Epigenetic Repression and Mobile DNA," F-75005, Paris, France
| |
Collapse
|
7
|
Molla-Herman A, Matias NR, Huynh JR. Chromatin modifications regulate germ cell development and transgenerational information relay. CURRENT OPINION IN INSECT SCIENCE 2014; 1:10-18. [PMID: 32846502 DOI: 10.1016/j.cois.2014.04.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 04/23/2014] [Accepted: 04/23/2014] [Indexed: 06/11/2023]
Abstract
Germ cells transmit genetic, cytoplasmic and epigenetic information to the next generation. Recent reports describe the importance of chromatin modifiers and small RNAs for germ cells development in Drosophila. We also review exciting progress in our understanding of piRNAs functions, which demonstrate that this class of small RNAs is both an adaptive and inheritable epigenetic memory.
Collapse
Affiliation(s)
- Anahi Molla-Herman
- Department of Genetics and Developmental Biology, Institut Curie, Paris, France; CNRS UMR3215, Inserm U934, F-75248 Paris, France
| | - Neuza R Matias
- Department of Genetics and Developmental Biology, Institut Curie, Paris, France; CNRS UMR3215, Inserm U934, F-75248 Paris, France
| | - Jean-René Huynh
- Department of Genetics and Developmental Biology, Institut Curie, Paris, France; CNRS UMR3215, Inserm U934, F-75248 Paris, France.
| |
Collapse
|
8
|
de Vanssay A, Bougé AL, Boivin A, Hermant C, Teysset L, Delmarre V, Antoniewski C, Ronsseray S. Conversions épigénétiques transmises de façon stable au cours des générations. Med Sci (Paris) 2013; 29:136-8. [DOI: 10.1051/medsci/2013292007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
9
|
Le Thomas A, Rogers AK, Webster A, Marinov GK, Liao SE, Perkins EM, Hur JK, Aravin AA, Tóth KF. Piwi induces piRNA-guided transcriptional silencing and establishment of a repressive chromatin state. Genes Dev 2013; 27:390-9. [PMID: 23392610 DOI: 10.1101/gad.209841.112] [Citation(s) in RCA: 349] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In the metazoan germline, piwi proteins and associated piwi-interacting RNAs (piRNAs) provide a defense system against the expression of transposable elements. In the cytoplasm, piRNA sequences guide piwi complexes to destroy complementary transposon transcripts by endonucleolytic cleavage. However, some piwi family members are nuclear, raising the possibility of alternative pathways for piRNA-mediated regulation of gene expression. We found that Drosophila Piwi is recruited to chromatin, colocalizing with RNA polymerase II (Pol II) on polytene chromosomes. Knockdown of Piwi in the germline increases expression of transposable elements that are targeted by piRNAs, whereas protein-coding genes remain largely unaffected. Derepression of transposons upon Piwi depletion correlates with increased occupancy of Pol II on their promoters. Expression of piRNAs that target a reporter construct results in a decrease in Pol II occupancy and an increase in repressive H3K9me3 marks and heterochromatin protein 1 (HP1) on the reporter locus. Our results indicate that Piwi identifies targets complementary to the associated piRNA and induces transcriptional repression by establishing a repressive chromatin state when correct targets are found.
Collapse
Affiliation(s)
- Adrien Le Thomas
- California Institute of Technology, Pasadena, California 91125, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
10
|
de Vanssay A, Bougé AL, Boivin A, Hermant C, Teysset L, Delmarre V, Antoniewski C, Ronsseray S. Paramutation in Drosophila linked to emergence of a piRNA-producing locus. Nature 2012; 490:112-5. [PMID: 22922650 DOI: 10.1038/nature11416] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 07/16/2012] [Indexed: 11/10/2022]
Abstract
A paramutation is an epigenetic interaction between two alleles of a locus, through which one allele induces a heritable modification in the other allele without modifying the DNA sequence. The paramutated allele itself becomes paramutagenic, that is, capable of epigenetically converting a new paramutable allele. Here we describe a case of paramutation in animals showing long-term transmission over generations. We previously characterized a homology-dependent silencing mechanism referred to as the trans-silencing effect (TSE), involved in P-transposable-element repression in the germ line. We now show that clusters of P-element-derived transgenes that induce strong TSE can convert other homologous transgene clusters incapable of TSE into strong silencers, which transmit the acquired silencing capacity through 50 generations. The paramutation occurs without any need for chromosome pairing between the paramutagenic and the paramutated loci, and is mediated by maternal inheritance of cytoplasm carrying Piwi-interacting RNAs (piRNAs) homologous to the transgenes. The repression capacity of the paramutated locus is abolished by a loss-of-function mutation of the aubergine gene involved in piRNA biogenesis, but not by a loss-of-function mutation of the Dicer-2 gene involved in siRNA production. The paramutated cluster, previously producing barely detectable levels of piRNAs, is converted into a stable, strong piRNA-producing locus by the paramutation and becomes fully paramutagenic itself. Our work provides a genetic model for the emergence of piRNA loci, as well as for RNA-mediated trans-generational repression of transposable elements.
Collapse
Affiliation(s)
- Augustin de Vanssay
- Laboratoire Biologie du Développement, UMR7622, CNRS-Université Pierre et Marie Curie, 9 quai Saint Bernard, 75005 Paris, France
| | | | | | | | | | | | | | | |
Collapse
|