The Experts below are selected from a list of 2067 Experts worldwide ranked by ideXlab platform
Peter J Merriman - One of the best experts on this subject based on the ideXlab platform.
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cytotype regulation by telomeric p elements in drosophila melanogaster evidence for involvement of an rna interference gene
Genetics, 2007Co-Authors: Michael J. Simmons, Donfelix Ryzek, Cecile Lamour, Nicole E Kummer, Joseph W. Goodman, Peter J MerrimanAbstract:P elements inserted at the left telomere of the X chromosome evoke the P cytotype, a maternally inherited condition that regulates the P-element family in the Drosophila germline. This regulation is completely disrupted in stocks heterozygous for mutations in Aubergine, a gene whose protein product is involved in RNA interference. However, cytotype is not disrupted in stocks heterozygous for mutations in two other RNAi genes, piwi and homeless (spindle-E), or in a stock heterozygous for a mutation in the chromatin protein gene Enhancer of zeste. Aubergine mutations exert their effects in the female germline, where the P cytotype is normally established and through which it is maintained. These effects are transmitted maternally to offspring of both sexes independently of the mutations themselves. Lines derived from mutant Aubergine stocks reestablish the P cytotype quickly, unlike lines derived from stocks heterozygous for a mutation in Suppressor of variegation 205, the gene that encodes the telomere-capping protein HP1. Cytotype regulation by telomeric P elements may be tied to a system that uses RNAi to regulate the activities of telomeric retrotransposons in Drosophila.
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cytotype regulation by telomeric p elements in drosophila melanogaster evidence for involvement of an rna interference gene
Genetics, 2007Co-Authors: Michael J. Simmons, Donfelix Ryzek, Cecile Lamour, Nicole E Kummer, Joseph W. Goodman, Peter J MerrimanAbstract:P elements inserted at the left telomere of the X chromosome evoke the P cytotype, a maternally inherited condition that regulates the P-element family in the Drosophila germline. This regulation is completely disrupted in stocks heterozygous for mutations in Aubergine, a gene whose protein product is involved in RNA interference. However, cytotype is not disrupted in stocks heterozygous for mutations in two other RNAi genes, piwi and homeless (spindle-E), or in a stock heterozygous for a mutation in the chromatin protein gene Enhancer of zeste. Aubergine mutations exert their effects in the female germline, where the P cytotype is normally established and through which it is maintained. These effects are transmitted maternally to offspring of both sexes independently of the mutations themselves. Lines derived from mutant Aubergine stocks reestablish the P cytotype quickly, unlike lines derived from stocks heterozygous for a mutation in Suppressor of variegation 205, the gene that encodes the telomere-capping protein HP1. Cytotype regulation by telomeric P elements may be tied to a system that uses RNAi to regulate the activities of telomeric retrotransposons in Drosophila.
Stéphane Ronsseray - One of the best experts on this subject based on the ideXlab platform.
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Paramutation in Drosophila Requires Both Nuclear and Cytoplasmic Actors of the piRNA Pathway and Induces Cis-spreading of piRNA Production
Genetics, 2015Co-Authors: Catherine Hermant, Antoine Boivin, Laure Teysset, Valerie Delmarre, Christophe Antoniewski, Amna Asif-laidin, Marius Beek, Stéphane RonsserayAbstract: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.
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The Drosophila Su(var)3–7 Gene Is Required for Oogenesis and Female Fertility, Genetically Interacts with piwi and Aubergine, but Impacts Only Weakly Transposon Silencing
PLoS ONE, 2014Co-Authors: Denis Basquin, Anne Spierer, Flora Begeot, Dmitry E Koryakov, Anne-laure Todeschini, Stéphane Ronsseray, Cristina Vieira, Pierre Spierer, Marion DelattreAbstract:Heterochromatin is made of repetitive sequences, mainly transposable elements (TEs), the regulation of which is critical for genome stability. We have analyzed the role of the heterochromatin-associated Su(var)3–7 protein in Drosophila ovaries. We present evidences that Su(var)3–7 is required for correct oogenesis and female fertility. It accumulates in heterochromatic domains of ovarian germline and somatic cells nuclei, where it co-localizes with HP1. Homozygous mutant females display ovaries with frequent degenerating egg-chambers. Absence of Su(var)3–7 in embryos leads to defects in meiosis and first mitotic divisions due to chromatin fragmentation or chromosome loss, showing that Su(var)3–7 is required for genome integrity. Females homozygous for Su(var)3–7 mutations strongly impair repression of P-transposable element induced gonadal dysgenesis but have minor effects on other TEs. Su(var)3–7 mutations reduce piRNA cluster transcription and slightly impact ovarian piRNA production. However, this modest piRNA reduction does not correlate with transposon de-silencing, suggesting that the moderate effect of Su(var)3–7 on some TE repression is not linked to piRNA production. Strikingly, Su(var)3–7 genetically interacts with the piwi and Aubergine genes, key components of the piRNA pathway, by strongly impacting female fertility without impairing transposon silencing. These results lead us to propose that the interaction between Su(var)3–7 and piwi or Aubergine controls important developmental processes independently of transposon silencing.
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Aubergine mutations in drosophila melanogaster impair p cytotype determination by telomeric p elements inserted in heterochromatin
Molecular Genetics and Genomics, 2004Co-Authors: Daphne Reiss, Thibaut Josse, Dominique Anxolabehere, Stéphane RonsserayAbstract:Transposable P elements inserted in the heterochromatic Telomeric Associated Sequences on the X chromosome (1A site) of Drosophila melanogaster have a very strong capacity to elicit the P cytotype, a maternally transmitted condition which represses P element transposition and P-induced hybrid dysgenesis. This repressive capacity has previously been shown to be sensitive to mutant alleles of the gene Su(var)205, which encodes HP1 (Heterochromatin Protein 1), thus suggesting a role for chromatin structure in repression. Since an interaction between heterochromatin formation and RNA interference has been reported in various organisms, we tested the effect of mutant alleles of Aubergine, a gene that has been shown to play a role in RNA interference in Drosophila, on the repressive properties of telomeric P elements. Seven out of the eight mutant alleles tested clearly impaired the repressive capacities of the two independent telomeric P insertions at 1A analyzed. P repression by P strains whose repressive capacities are not linked to the presence of P copies at 1A were previously found to be insensitive to Su(var)205; here, we show that they are also insensitive to Aubergine mutations. These results strongly suggest that both RNA interference and heterochromatin structure are involved in the establishment of the P cytotype elicited by telomeric P elements, and reinforce the hypothesis that different mechanisms for repression of P elements exist which depend on the chromosomal location of the regulatory copies of P.
Michael J. Simmons - One of the best experts on this subject based on the ideXlab platform.
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maternal enhancement of cytotype regulation in drosophila melanogaster by genetic interactions between telomeric p elements and non telomeric transgenic p elements
Genetics Research, 2012Co-Authors: Michael J. Simmons, Lisa M Ragatz, Ian R Sinclair, Michael W Thorp, Jared T Buschette, Craig D GrimesAbstract:The X-linked telomeric P elements (TPs) TP5 and TP6 regulate the activity of the entire P element family because they are inserted in a major locus for the production of Piwi-interacting RNAs (piRNAs). The potential for this cytotype regulation is significantly strengthened when either TP5 or TP6 is combined with a non-telomeric X-linked or autosomal transgene that contains a P element. By themselves, none of the transgenic P elements have any regulatory ability. Synergism between the telomeric and transgenic P elements is much greater when the TP is derived from a female. Once an enhanced regulatory state is established in a female, it is transmitted to her offspring independently of either the telomeric or transgenic P elements - that is, it works through a strictly maternal effect. Synergistic regulation collapses when either the telomeric or the transgenic P element is removed from the maternal genotype, and it is significantly impaired when the TPs come from stocks heterozygous for mutations in the genes Aubergine, piwi or Su(var)205. The synergism between telomeric and transgenic P elements is consistent with a model in which P piRNAs are amplified by alternating, or ping-pong, targeting of primary piRNAs to sense and antisense P transcripts, with the sense transcripts being derived from the transgenic P element and the antisense transcripts being derived from the TP.
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cytotype regulation by telomeric p elements in drosophila melanogaster evidence for involvement of an rna interference gene
Genetics, 2007Co-Authors: Michael J. Simmons, Donfelix Ryzek, Cecile Lamour, Nicole E Kummer, Joseph W. Goodman, Peter J MerrimanAbstract:P elements inserted at the left telomere of the X chromosome evoke the P cytotype, a maternally inherited condition that regulates the P-element family in the Drosophila germline. This regulation is completely disrupted in stocks heterozygous for mutations in Aubergine, a gene whose protein product is involved in RNA interference. However, cytotype is not disrupted in stocks heterozygous for mutations in two other RNAi genes, piwi and homeless (spindle-E), or in a stock heterozygous for a mutation in the chromatin protein gene Enhancer of zeste. Aubergine mutations exert their effects in the female germline, where the P cytotype is normally established and through which it is maintained. These effects are transmitted maternally to offspring of both sexes independently of the mutations themselves. Lines derived from mutant Aubergine stocks reestablish the P cytotype quickly, unlike lines derived from stocks heterozygous for a mutation in Suppressor of variegation 205, the gene that encodes the telomere-capping protein HP1. Cytotype regulation by telomeric P elements may be tied to a system that uses RNAi to regulate the activities of telomeric retrotransposons in Drosophila.
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cytotype regulation by telomeric p elements in drosophila melanogaster evidence for involvement of an rna interference gene
Genetics, 2007Co-Authors: Michael J. Simmons, Donfelix Ryzek, Cecile Lamour, Nicole E Kummer, Joseph W. Goodman, Peter J MerrimanAbstract:P elements inserted at the left telomere of the X chromosome evoke the P cytotype, a maternally inherited condition that regulates the P-element family in the Drosophila germline. This regulation is completely disrupted in stocks heterozygous for mutations in Aubergine, a gene whose protein product is involved in RNA interference. However, cytotype is not disrupted in stocks heterozygous for mutations in two other RNAi genes, piwi and homeless (spindle-E), or in a stock heterozygous for a mutation in the chromatin protein gene Enhancer of zeste. Aubergine mutations exert their effects in the female germline, where the P cytotype is normally established and through which it is maintained. These effects are transmitted maternally to offspring of both sexes independently of the mutations themselves. Lines derived from mutant Aubergine stocks reestablish the P cytotype quickly, unlike lines derived from stocks heterozygous for a mutation in Suppressor of variegation 205, the gene that encodes the telomere-capping protein HP1. Cytotype regulation by telomeric P elements may be tied to a system that uses RNAi to regulate the activities of telomeric retrotransposons in Drosophila.
Mikiko C. Siomi - One of the best experts on this subject based on the ideXlab platform.
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Gender-Specific Hierarchy in Nuage Localization of PIWI-Interacting RNA Factors in Drosophila.
Frontiers in genetics, 2011Co-Authors: Akihiro Nagao, Kazumichi M. Nishida, Haruhiko Siomi, Kaoru Sato, Mikiko C. SiomiAbstract:PIWI-interacting RNAs (piRNAs) are germline-specific small non-coding RNAs that form piRNA-induced silencing complexes (piRISCs) by associating with PIWI proteins, a subclade of the Argonaute proteins predominantly expressed in the germline. piRISCs protect the integrity of the germline genome from invasive transposable DNA elements by silencing them. Multiple piRNA biogenesis factors have been identified in Drosophila. The majority of piRNA factors are localized in the nuage, electron-dense non-membranous cytoplasmic structures located in the perinuclear regions of germ cells. Thus, piRNA biogenesis is thought to occur in the nuage in germ cells. Immunofluorescence analyses of ovaries from piRNA factor mutants have revealed a localization hierarchy of piRNA factors in female nuage. However, whether this hierarchy is female-specific or can also be applied in male gonads remains undetermined. Here, we show by immunostaining of both ovaries and testes from piRNA factor mutants that the molecular hierarchy of piRNA factors shows gender-specificity, especially for Krimper (Krimp), a Tudor-domain containing protein of unknown function(s): Krimp is dispensable for PIWI protein Aubergine (Aub) nuage localization in ovaries but Krimp and Aub require each other for their proper nuage localization in testes. This suggests that the functional requirement of Krimp in piRNA biogenesis may be different in male and female gonads.
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gene silencing mechanisms mediated by Aubergine pirna complexes in drosophila male gonad
RNA, 2007Co-Authors: Kazumichi M. Nishida, Haruhiko Siomi, Kuniaki Saito, Sachi Inagaki, Yoshinori Kawamura, Tomoko Mori, Tomoko Nagamiokada, Mikiko C. SiomiAbstract:Genetic studies have shown that Aubergine (Aub), one of the Piwi subfamily of Argonautes in Drosophila, is essential for germ cell formation and maintaining fertility. aub mutations lead to the accumulation of retrotransposons in ovaries and testes, and Stellate transcripts in testes. Aub in ovaries associates with a variety of Piwi-interacting RNAs (piRNAs) derived from repetitive intergenic elements including retrotransposons. Here we found that Aub in testes also associates with various kinds of piRNAs. Although in ovaries Aub-associated piRNA populations are quite diverse, piRNAs with Aub in testes show a strong bias. The most abundant piRNAs were those corresponding to antisense transcripts of Suppressor of Stellate [Su(Ste)] genes known to be involved in Stellate gene silencing. The second most abundant class was made up of those from chromosome X and showed strong complementarity to vasa transcripts. Immunopurified Aub–piRNA complexes from testes displayed activity in cleaving target RNA containing sequences complementary to Stellate and vasa transcripts. These results provide the first biochemical insights into gene silencing mechanisms mediated by Aub and piRNAs in fly testes.
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a slicer mediated mechanism for repeat associated sirna 5 end formation in drosophila
Science, 2007Co-Authors: Lalith S Gunawardane, Kazumichi M. Nishida, Haruhiko Siomi, Kuniaki Saito, Yoshinori Kawamura, Keita Miyoshi, Tomoko Nagami, Mikiko C. SiomiAbstract:In Drosophila, repeat-associated small interfering RNAs (rasiRNAs) are produced in the germ line by a Dicer-independent pathway and function through the PIWI subfamily of Argonautes to ensure silencing of retrotransposons. We sequenced small RNAs associated with the PIWI subfamily member AGO3. Although other members of PIWI, Aubergine (Aub) and Piwi, associated with rasiRNAs derived mainly from the antisense strand of retrotransposons, AGO3-associated rasiRNAs arose mainly from the sense strand. Aub- and Piwi-associated rasiRNAs showed a strong preference for uracil at their 5′ ends, and AGO3-associated rasiRNAs showed a strong preference for adenine at nucleotide 10. Comparisons between AGO3- and Aub-associated rasiRNAs revealed pairs of rasiRNAs showing complementarities in their first 10 nucleotides. Aub and AGO3 exhibited Slicer activity in vitro. These data support a model in which formation of a 5′ terminus within rasiRNA precursors is guided by rasiRNAs originating from transcripts of the other strand in concert with the Slicer activity of PIWI.
Haifan Lin - One of the best experts on this subject based on the ideXlab platform.
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a critical role for nucleoporin 358 nup358 in transposon silencing and pirna biogenesis in drosophila
Journal of Biological Chemistry, 2018Co-Authors: Rasesh Y Parikh, Haifan Lin, Vamsi K. GangarajuAbstract:Piwi-interacting RNAs (piRNAs) are a class of small noncoding RNAs that bind Piwi proteins to silence transposons and to regulate gene expression. In Drosophila germ cells, the Aubergine (Aub)-Argonaute 3 (Ago3)–dependent ping-pong cycle generates most germline piRNAs. Loading of antisense piRNAs amplified by this cycle enables Piwi to enter the nucleus and silence transposons. Nuclear localization is crucial for Piwi function in transposon silencing, but how this process is regulated remains unknown. It is also not known whether any of the components of the nuclear pore complex (NPC) directly function in the piRNA pathway. Here, we show that nucleoporin 358 (Nup358) and Piwi interact with each other and that a germline knockdown (GLKD) of Nup358 with short hairpin RNA prevents Piwi entry into the nucleus. The Nup358 GLKD also activated transposons, increased genomic instability, and derailed piRNA biogenesis because of a combination of decreased piRNA precursor transcription and a collapse of the ping-pong cycle. Our results point to a critical role for Nup358 in the piRNA pathway, laying the foundation for future studies to fully elucidate the mechanisms by which Nup358 contributes to piRNA biogenesis and transposon silencing.
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function of piwi a nuclear piwi argonaute protein is independent of its slicer activity
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Nicole Darricarrère, Toshiaki Watanabe, Na Liu, Haifan LinAbstract:The Piwi protein subfamily is essential for Piwi-interacting RNA (piRNA) biogenesis, transposon silencing, and germ-line development, all of which have been proposed to require Piwi endonuclease activity, as validated for two cytoplasmic Piwi proteins in mice. However, recent evidence has led to questioning of the generality of this mechanism for the Piwi members that reside in the nucleus. Drosophila offers a distinct opportunity to study the function of nuclear Piwi proteins because, among three Drosophila Piwi proteins—called Piwi, Aubergine, and Argonaute 3—Piwi is the only member of this subfamily that is localized in the nucleus and expressed in both germ-line and somatic cells in the gonad, where it is responsible for piRNA biogenesis and regulatory functions essential for fertility. In this study, we demonstrate beyond doubt that the slicer activity of Piwi is not required for any known functions in vivo. We show that, in transgenic flies with the DDX catalytic triad of PIWI mutated, neither primary nor secondary piRNA biogenesis is detectably affected, transposons remain repressed, and fertility is normal. Our observations demonstrate that the mechanism of Piwi is independent of its in vitro endonuclease activity. Instead, it is consistent with the alternative mode of Piwi function as a molecule involved in the piRNA-directed guidance of epigenetic factors to chromatin.
