Production of artificial piRNAs in flies and mice

Muerdter, Felix; Olovnikov, Ivan; Molaro, Antoine; Rozhkov, Nikolay V.; Czech, Benjamin; Gordon, Assaf; Hannon, Gregory J.; Aravin, Alexei A.

doi:10.1261/rna.029769.111

Cited by 101 publications

(123 citation statements)

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“…Targeted knockin of a DNA fragment homologous to the target gene (or RNA) into a piRNA cluster region in an opposite orientation should cause specific knockdown in vivo without a side effect in somatic tissues. When this manuscript was in preparation, Muerdter et al (2011) reported successful production of artificial piRNAs from BAC transgene in mouse testis, although they did not analyze their effect on target mRNA. Mouse BAC clones containing a piRNA precursor region with its promoter elements will be particularly useful, because recombination in host bacteria combined with pronuclear injection of the BAC transgene can lead to generation of the desired piRNAs in germ cells and quickly provide knockdown mice.…”

Section: Discussionmentioning

confidence: 99%

Targeted gene silencing in mouse germ cells by insertion of a homologous DNA into a piRNA generating locus

et al. 2012

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In germ cells, early embryos, and stem cells of animals, PIWI-interacting RNAs (piRNAs) have an important role in silencing retrotransposons, which are vicious genomic parasites, through transcriptional and post-transcriptional mechanisms. To examine whether the piRNA pathway can be used to silence genes of interest in germ cells, we have generated knock-in mice in which a foreign DNA fragment was inserted into a region generating pachytene piRNAs. The knock-in sequence was transcribed, and the resulting RNA was processed to yield piRNAs in postnatal testes. When reporter genes possessing a sequence complementary to portions of the knock-in sequence were introduced, they were greatly repressed after the time of pachytene piRNA generation. This repression mainly occurred at the post-transcriptional level, as degradation of the reporter RNAs was accelerated. Our results show that the piRNA pathway can be used as a tool for sequence-specific gene silencing in germ cells and support the idea that the piRNA generating regions serve as traps for retrotransposons, enabling the host cell to generate piRNAs against active retrotransposons.

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Section: Discussionmentioning

confidence: 99%

Targeted gene silencing in mouse germ cells by insertion of a homologous DNA into a piRNA generating locus

et al. 2012

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“…However, the majority of these mouse models used human L1-based transgenes or constitutively active non-L1 promoters. The current model suggests a sequence-specific interaction between a piRNA and its target for transcriptional (30,31) and posttranscriptional silencing (19,32,33). Thus, we reasoned that an L1 transgene with an endogenous mouse L1 promoter is the best way to model L1 regulation by the piRNA-DNA methylation pathway.…”

Section: Significancementioning

confidence: 97%

Intact piRNA pathway prevents L1 mobilization in male meiosis

Newkirk

Lee

Grandi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The PIWI-interacting RNA (piRNA) pathway is essential for retrotransposon silencing. In piRNA-deficient mice, L1-overexpressing male germ cells exhibit excessive DNA damage and meiotic defects. It remains unknown whether L1 expression simply highlights piRNA deficiency or actually drives the germ-cell demise. Specifically, the sheer abundance of genomic L1 copies prevents reliable quantification of new insertions. Here, we developed a codon-optimized L1 transgene that is controlled by an endogenous mouse L1 promoter. Importantly, DNA methylation dynamics of a single-copy transgene were indistinguishable from those of endogenous L1s. Analysis of Mov10l1 −/− testes established that de novo methylation of the L1 transgene required the intact piRNA pathway. Consistent with loss of DNA methylation and programmed reduction of H3K9me2 at meiotic onset, the transgene showed 1,400-fold increase in RNA expression and consequently 70-fold increase in retrotransposition in postnatal day 14 Mov10l1 −/− germ cells compared with the wildtype. Analysis of adult Mov10l1 −/− germ-cell fractions indicated a stage-specific increase of retrotransposition in the early meiotic prophase. However, extrapolation of the transgene data to endogenous L1s suggests that it is unlikely insertional mutagenesis alone accounts for the Mov10l1 −/− phenotype. Indeed, pharmacological inhibition of reverse transcription did not rescue the meiotic defect. Cumulatively, these results establish the occurrence of productive L1 mobilization in the absence of an intact piRNA pathway but leave open the possibility of processes preceding L1 integration in triggering meiotic checkpoints and germ-cell death. Additionally, our data suggest that many heritable L1 insertions originate from individuals with partially compromised piRNA defense.LINE-1 reporter transgene | meiotic arrest | PIWI-interacting RNA | retrotransposition | spermatogenesis T he bulk of mammalian genomes are made up of transposable elements, the majority of which are retrotransposons (1). Retrotransposons are classified into long-interspersed elements (LINEs), short-interspersed elements (SINEs), and LTR retrotransposons, which collectively account for 43% and 37% of the human and mouse genomes, respectively (2). Retrotransposons amplify in the genome through an RNA intermediate, a process termed retrotransposition. LINEs are autonomous elements. An intact, full-length LINE-1 (L1) encodes two ORFs (i.e., ORF1 and ORF2); both are required for L1 mobilization (3). SINEs are nonautonomous elements and rely on L1's proteins for propagation in the genome (4). LTR retrotransposons are autonomous but appear to be inactivated in the human genome (5). Retrotransposition endangers the integrity of both somatic and germline genomes through insertional mutagenesis. In somatic tissues, both elevated L1 expression and retrotransposition have been strongly associated with many types of human cancers (6, 7). In a few cases, specific retrotransposition events (i.e., insertions) have been determined to drive t...

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Section: Other Components Of Micro and Sirna Biogenesismentioning

confidence: 99%

“…piRNA precursors are produced in the nucleus as long, single-stranded transcripts, each of which contains many individual elements that can be processed into mature small RNAs. The loci that give rise to these transcripts are termed piRNA clusters, and they serve as a catalog for what will ultimately become piRNA guide strands [41,42].Much of what we know about piRNA biogenesis mechanisms has been derived using the Drosophila melanogaster model system and only some of which has clear parallels in mammals. After transcription, primary (presumably intact) transcripts are exported from the nucleus, then localized to the nuage -a perinuclear/perimitochondrial cytoplasmic region enriched in many piRNA-related molecules [43].…”

mentioning

confidence: 99%

From guide to target: molecular insights into eukaryotic RNA-interference machinery

Ipsaro

Joshua‐Tor

2015

Nat Struct Mol Biol

218

144

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Since its relatively recent discovery, RNA interference (RNAi) has emerged as a potent, specific, and ubiquitous means of gene regulation. Through a number of pathways that are conserved from yeast to humans, small non-coding RNAs direct molecular machinery to silence gene expression. In this review, we focus on mechanisms and structures that govern RNA silencing in higher organisms. In addition to highlighting recent advances, parallels and differences between RNAi pathways are discussed. Together, the studies reviewed herein reveal the versatility and programmability of RNA-induced Silencing Complexes (RISCs) and emphasize the importance of both upstream biogenesis and downstream silencing factors. Discovery and Biological Perspectives of RNA interferenceRNAi was first described by Fire and Mello in the 1990s when, in an attempt to use antisense RNA to down-regulate gene expression, they observed that double-stranded RNA (dsRNA) was more potent than sense or anti-sense RNA alone [1]. This seminal work boasted robust and specific gene knock down in addition to coining the term "RNA interference" (RNAi). Shortly beforehand, the discovery of individual regulatory RNAs in C. elegans hinted that small, non-coding RNAs might be a pervasive means of gene regulation in higher organisms [2,3]. In the following decade, with the mechanistic insight of Fire and Mello's work in hand, this idea was confirmed and it is now accepted that wellover 1,000 small RNAs are encoded in the human genome that may regulate over 60% of our genes [4,5]. It also became apparent that several seemingly disconnected phenomena are variations of RNAi-type pathways including co-suppression in plants, DNA elimination in Tetrahymena, and quelling in Neurospora [6]. The prevalence of RNAi is impressive and its importance is underscored by the fact that RNAi dysfunction is associated with numerous diseases and disorders including neurological maladies, cancers, and infertility.Shortly after the initial description of RNAi phenomenology, a burst of genetic, biochemical, biophysical, and bioinformatic efforts laid a strong foundation for identifying the molecular pathways, players, and parameters that govern silencing via RNAi. Work from Reprints and permissions information is available online at http://www.nature.com/reprints/index.html. HHMI Author ManuscriptHHMI Author Manuscript HHMI Author Manuscript numerous groups defined the molecular apparatus of RNAi as RISC (RNA-induced Silencing Complex), a ribonucleoprotein complex minimally comprised of a small singlestranded RNA (~20-31 nucleotides) and an Argonaute protein which serves as the effector molecule (reviewed in [7]). In this configuration, the loaded "guide" RNA acts as a specificity determinant that directs Argonaute and any other associated machinery to the target. The guide-loaded Argonaute platform underlies every example in the expansive array of known RNAi pathways in eukaryotes regardless of the source of the guide (structured loci, transposons, viral, etc.), the machinery ...

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Production of artificial piRNAs in flies and mice

Cited by 101 publications

References 60 publications

Targeted gene silencing in mouse germ cells by insertion of a homologous DNA into a piRNA generating locus

Targeted gene silencing in mouse germ cells by insertion of a homologous DNA into a piRNA generating locus

Intact piRNA pathway prevents L1 mobilization in male meiosis

From guide to target: molecular insights into eukaryotic RNA-interference machinery

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