PiRNAs can trigger a multigenerational epigenetic memory in the germline of C. elegans
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ABSTRACT:
ORGANISM(S): Caenorhabditis elegans
PROVIDER: GSE38813 | GEO | 2012/06/25
SECONDARY ACCESSION(S): PRJNA168969
REPOSITORIES: GEO
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Project description:Transgenerational effects likely have wide-ranging implications for human health, biological adaptation and evolution, however their mechanism and biology remain poorly understood. Here we demonstrate that a germline nuclear small RNA/chromatin pathway can maintain epi-allelic inheritance for many generations when triggered by a piRNA-dependent foreign RNA response in C. elegans. Using forward genetic screens and candidate approaches we find that a core set of nuclear RNAi and chromatin factors are required for multigenerational inheritance of environmental RNAi and piRNA silencing. These include a germline-specific nuclear Argonaute HRDE1/WAGO-9, a HP1 otholog HPL-2 and two putative histone methyltransferases, SET-25 and SET-32. Most surprisingly, piRNAs can trigger highly stable long-term silencing lasting at least 20 generations. Once established, this long-term memory becomes independent of the piRNA trigger but remains dependent on the nuclear RNAi/chromatin pathway. Our data present the first report of multigenerational epigenetic inheritance induced by piRNAs in any organism. Seven C. elegans small RNA libraries from three distinct experiments (A, B, C) were sequenced using Illumina sequencing technology. Five small RNA libraries were prepared according to library construction protocol 1 and sequenced as part of 22 flow cell lanes on the Illumina GA IIx platform. Samples were labelled for multiplexing using 4-bp 5'-barcodes, a single flow cell lane included several multiplexed libraries. Two small RNA libraries were prepared according to library construction protocol 2 and sequenced on the Illumina MiSeq platform.
2012-06-25 | E-GEOD-38813 | biostudies-arrayexpress
Project description:In the nematode Caenorhabditis elegans, different small RNA-dependent gene silencing mechanisms act in the germline to initiate transgenerational gene silencing. Piwi-interacting RNAs (piRNAs) can initiate transposon and gene silencing by acting upstream of endogenous short interfering RNAs (siRNAs), which engage a nuclear RNA interference (RNAi) pathway to trigger transcriptional gene silencing. Once gene silencing has been established, it can be stably maintained over multiple generations without the requirement of the initial trigger and is also referred to as RNAe or paramutation. This heritable silencing depends on the integrity of the nuclear RNAi pathway. However, the exact mechanism by which silencing is maintained across generations is not understood.Here we demonstrate that silencing of piRNA targets involves the production of two distinct classes of small RNAs with different genetic requirements. The first class, secondary siRNAs, are localized close to the direct target site for piRNAs. Nuclear import of the secondary siRNAs by the Argonaute HRDE-1 leads to the production of a distinct class of small RNAs that map throughout the transcript, which we term tertiary siRNAs. Both classes of small RNAs are necessary for full repression of the target gene and can be maintained independently of the initial piRNA trigger. Consistently, we observed a form of paramutation associated with tertiary siRNAs. Once paramutated, a tertiary siRNA generating allele confers dominant silencing in the progeny regardless of its own transmission, suggesting germline-transmitted siRNAs are sufficient for multigenerational silencing. C. elegans strains containing transgenes silenced by piRNAs were crossed to strains with transgenes with similar sequences but without piRNA target sites, to investigate the spreading of silencing between transgenes mediated by small RNAs. Mutant backgrounds were used to investigate the genetic requirements for this process.
2015-04-01 | E-GEOD-66344 | biostudies-arrayexpress
Project description:In the nematode Caenorhabditis elegans, different small RNA-dependent gene silencing mechanisms act in the germline to initiate transgenerational gene silencing. Piwi-interacting RNAs (piRNAs) can initiate transposon and gene silencing by acting upstream of endogenous short interfering RNAs (siRNAs), which engage a nuclear RNA interference (RNAi) pathway to trigger transcriptional gene silencing. Once gene silencing has been established, it can be stably maintained over multiple generations without the requirement of the initial trigger and is also referred to as RNAe or paramutation. This heritable silencing depends on the integrity of the nuclear RNAi pathway. However, the exact mechanism by which silencing is maintained across generations is not understood.Here we demonstrate that silencing of piRNA targets involves the production of two distinct classes of small RNAs with different genetic requirements. The first class, secondary siRNAs, are localized close to the direct target site for piRNAs. Nuclear import of the secondary siRNAs by the Argonaute HRDE-1 leads to the production of a distinct class of small RNAs that map throughout the transcript, which we term tertiary siRNAs. Both classes of small RNAs are necessary for full repression of the target gene and can be maintained independently of the initial piRNA trigger. Consistently, we observed a form of paramutation associated with tertiary siRNAs. Once paramutated, a tertiary siRNA generating allele confers dominant silencing in the progeny regardless of its own transmission, suggesting germline-transmitted siRNAs are sufficient for multigenerational silencing.
2015-04-01 | GSE66344 | GEO
Project description:The notion that genes are the sole units of heredity and that a barrier exists between soma and germline has been a major hurdle in elucidating the heritability of traits that were observed to follow a non-Mendelian inheritance pattern. It was only after the conception of “epigenetics” by C. H. Waddington that the effect of parental environment on subsequent generations via non-DNA sequence-based mechanisms, such as DNA methylation, chromatin modifications, non-coding RNAs and proteins, could be established in various organisms, now referred to as multigenerational epigenetic inheritance. Despite the growing body of evidence, the male gamete-derived epigenetic factors that mediate the transmission of such phenotypes are seldom explored, particularly in the model organism Drosophila melanogaster. Using the heat stress-induced multigenerational epigenetic inheritance paradigm in a widely used position-effect variegation line of Drosophila, named white-mottled, we have dissected the effect of heat stress on the sperm proteome in the current study. We demonstrate that multiple successive generations of heat stress at the early embryonic stage results in a significant downregulation of proteins associated with translation, chromatin organization, microtubule-based processes, and generation of metabolites and energy in the Drosophila sperms. Based on our findings, we propose chromatin-based epigenetic mechanisms, a well-established mechanism for environmentally induced multigenerational effects, as a plausible way of transmitting heat stress memory via the male germ line in subsequent generations. Moreover, we demonstrate the effect of multiple generations of heat stress on the reproductive fitness of Drosophila, shedding light on the adaptive or maladaptive potential of heat stress-induced multigenerational phenotypes.
2024-05-10 | PXD037488 | Pride
Project description:PIWI-interacting RNAs (piRNAs) promote fertility in many animals. Yet, whether this is due to their conserved role in repressing repetitive elements (REs) or other functions remains unclear. Here, we show that the progressive loss of fertility in Caenorhabditis elegans lacking piRNAs is not caused by derepression of REs or other piRNA targets, but rather mediated by the epigenetic silencing of all the replicative histone genes. In the absence of piRNAs, downstream components of the piRNA pathway relocalize from germ granules and piRNA targets to histone mRNAs to synthesize antisense small RNAs (sRNAs) and induce transgenerational silencing. Removal of the downstream components of the piRNA pathway is sufficient to restore histone mRNA expression and fertility in piRNA mutants, and the inheritance of histone sRNAs in wild-type worms adversely affects their fertility for multiple generations. We conclude that the transgenerational silencing of histone genes contributes to the progressive loss of fertility in piRNA mutants and that coupling piRNAs and histone silencing may serve to maintain piRNAs production across evolution.
2019-12-11 | PXD012557 | Pride
Project description:dsRNA-mediated gene silencing (RNAi) can be inherited for multiple generations in C. elegans. To understand this process we conducted a genetic screen for animals defective for transmitting RNAi silencing signals to future generations. This screen identified the gene heritable RNAi defective (hrde)-1. hrde-1 encodes an Argonaute (Ago) that associates with siRNAs in germ cells of the progeny of animals exposed to dsRNA. In nuclei of these germ cells, HRDE-1 engages the Nrde nuclear RNAi pathway to promote RNAi inheritance, and directs H3K9me3 chromatin marks at RNAi targeted genomic loci. Under normal growth conditions, HRDE-1 associates with endogenously expressed small RNAs, which direct nuclear gene silencing in germ cells. In RNAi inheritance mutant animals, silencing is lost over generational time. Concurrently, RNAi inheritance mutant animals exhibit progressively worsening germline defects that ultimately lead to sterility. These results establish that the Ago HRDE-1 directs gene-silencing events in germ cell nuclei, which are required for multi-generational RNAi inheritance and immortality of the germ cell lineage. We propose that C. elegans use the RNAi inheritance machinery to transmit epigenetic information, accrued by past generations, into future generations to ensure immortality of the germ cell lineage.
2012-07-30 | GSE38041 | GEO
Project description:Argonaute proteins of the PIWI-clade, complexed with PIWI-interacting RNAs (piRNAs), protect the animal germline genome by silencing transposable elements. One of the leading experimental systems for studying piRNA biology is the Drosophila melanogaster ovary. In addition to classical mutagenesis, transgenic RNA interference (RNAi), which enables tissue-specific silencing of gene expression, plays a central role in piRNA research. Here, we establish a versatile toolkit focused on piRNA biology that integrates transgenic RNAi in the germline, GFP-marker lines for key proteins of the piRNA pathway, and reporter transgenes to establish genetic hierarchies. We compare constitutive, pan-germline RNAi with an equally potent transgenic RNAi system that is activated only upon germ cell cyst formation. Stage specific RNAi allows investigating the role of genes essential for cell survival (e.g. nuclear RNA export or the SUMOylation pathways) in piRNA-dependent and independent transposon silencing. Our work forms the basis for an expandable genetic toolkit available from the Vienna Drosophila Resource Center.
2021-05-19 | GSE174611 | GEO
Project description:Gene silencing mediated by dsRNA (RNAi) can persist for multiple generations in C. elegans (termed RNAi inheritance). Here we describe the results of a forward genetic screen in C. elegans that has identified six factors required for RNAi inheritance: GLH-1/VASA, PUP-1/CDE-1, MORC-1, SET-32, and two novel nematode-specific factors that we term here (heritable RNAi defective) HRDE-2 and HRDE-4. The new RNAi inheritance factors exhibit mortal germline (Mrt) phenotypes, which we show is likely caused by epigenetic deregulation in germ cells. We also show that HRDE-2 contributes to RNAi inheritance by facilitating the binding of small RNAs to the inheritance Argonaute (Ago) HRDE-1. Together, our results identify additional components of the RNAi inheritance machinery whose sequence conservation provides insights into the molecular mechanism of RNAi inheritance, further our understanding of how the RNAi inheritance machinery promotes germline immortality, and show that HRDE-2 couples the inheritance Ago HRDE-1 with the small RNAs it needs to direct RNAi inheritance and germline immortality.
2017-06-20 | GSE92840 | GEO
Project description:Nuclear RNAi provides a highly tractable system to study RNA-mediated chromatin changes and epigenetic inheritance. Recent studies indicate that nuclear RNAi-mediated heterochromatin is highly complex in its regulation and function. The knowledge of histone modifications that are involved in nuclear RNAi and the corresponding histone modifying enzymes remains limited. In this study, we show that the heterochromatin mark H3K23me3 is induced by nuclear RNAi at both exogenous and endogenous targets in C. elegans. In addition, RNAi-induced H3K23me3 can be inherited for at least four generations. We also demonstrate that the histone methyltransferase SET-32, methylates H3K23 in vitro. Both set-32 and the germline nuclear RNAi Argonaute, hrde-1, are required for nuclear RNAi-induced H3K23me3 in vivo. Our data poise H3K23me3 as a chromatin modification involved in the nuclear RNAi pathway and provides the field with a new target for uncovering the role of heterochromatin in transgenerational epigenetic silencing.
2020-05-01 | GSE141347 | GEO
Project description:PIWI-interacting RNAs (piRNAs) are animal gonad-specific small RNAs that control the activity of transposable elements. Long single stranded RNAs from a variety of sources are substrates for the nebulous primary processing pathway that converts these into thousands of 24-30 nucleotide (nt) piRNAs. How these transcripts are selected as precursors is not known. Here we show that targeting a transcript with PIWI slicer activity of cysosolic Ago3 is sufficient to trigger ~30-nt waves of non-overlapping primary piRNAs in the fly ovarian germline. The generated primary piRNAs are almost exclusively loaded into the nuclear PIWI protein, Piwi. In the fly ovarian somatic environment we find that an RNA fragment from the 5? end of a piRNA cluster is able to direct a heterologous sequence into primary processing. This piRNA trigger sequence (PTS) element drives generation of overlapping piRNAs from the transcript. Both mechanisms proceed with general 5?-3? directionality. We propose that the former pathway serves to link cytoplasmic silencing of a target to nuclear transcriptional repression, while the latter extracts silencing information from a wide variety of genomic sources including piRNA clusters, select protein coding and transposon transcripts. Total or immunoprecipitated small RNAs were purified from transfected BmN4 cells, Drosophila ovarian somatic cells (OSC) and from fly ovaries and high-throughput sequencing libraries were prepared. The mouse testicular RNAs were purified after ribozero treatment.
2015-07-09 | E-GEOD-69102 | biostudies-arrayexpress