I elements in &lt;i&gt;Drosophila:&lt;/i&gt; in vivo retrotransposition and regulation

Chambeyron, Séverine; Bucheton, Alain

doi:10.1159/000084955

Cited by 23 publications

(16 citation statements)

References 103 publications

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“…Indeed, after crossing with standard I males, females from strains known as ''strong R'' strains produce SF females in which I elements transpose at very high frequency, while females of other R strains, known as ''weak R'' strains, produce SF females in which they transpose at a lower level. Reactivity displays an idiosyncratic maternal transmission (11)(12)(13). We showed that, although we could not detect I element piRNAs in R strains, whatever the reactivity level (Fig.…”

Section: Euchromatic I Elements Trigger the Production Of Pirnas Whosementioning

confidence: 80%

piRNA-mediated nuclear accumulation of retrotransposon transcripts in the Drosophila female germline

Chambeyron

Popkova

Payen-Groschêne

et al. 2008

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

124

117

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Germline silencing of transposable elements is essential for the maintenance of genome integrity. Recent results indicate that this repression is largely achieved through a RNA silencing pathway that involves Piwi-interacting RNAs (piRNAs). However the repressive mechanisms are not well understood. To address this question, we used the possibility to disrupt the repression of the Drosophila I element retrotransposon by hybrid dysgenesis. We show here that the repression of the functional I elements that are located in euchromatin requires proteins of the piRNA pathway, and that the amount of ovarian I element piRNAs correlates with the strength of the repression in the female germline. Antisense RNAs, which are likely used to produce antisense piRNAs, are transcribed by heterochromatic defective I elements, but efficient production of these antisense small RNAs requires the presence in the genome of euchromatic functional I elements. Finally, we demonstrate that the piRNA-induced silencing of the functional I elements is at least partially posttranscriptional. In a repressive background, these elements are still transcribed, but some of their sense transcripts are kept in nurse cell nuclear foci together with those of the Doc retrotransposon. In the absence of I element piRNAs, either in dysgenic females or in mutants of the piRNA silencing pathway, sense I element transcripts are transported toward the oocyte where retrotransposition occurs. Our results indicate that piRNAs are involved in a posttranscriptional gene-silencing mechanism resulting in RNA nuclear accumulation.hybrid dysgenesis ͉ I element ͉ RNA silencing

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Section: Euchromatic I Elements Trigger the Production Of Pirnas Whosementioning

confidence: 80%

piRNA-mediated nuclear accumulation of retrotransposon transcripts in the Drosophila female germline

Chambeyron

Popkova

Payen-Groschêne

et al. 2008

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

124

117

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“…I factors of Drosophila melanogaster are LINE-like elements that actively transpose in the germline of the female progeny (called SF) from crosses between females of reactive (R) strains and males of inducer (I) strains [1]; for a recent review see [2]. This phenomenon, called I-R hybrid dysgenesis, gives rise to reduced fertility, X chromosome loss and increased frequency of euchromatic and heterochromatic mutations.…”

Section: Introductionmentioning

confidence: 99%

Genomic Instability of I Elements of Drosophila melanogaster in Absence of Dysgenic Crosses

Moschetti

Dimitri²,

Caizzi

et al. 2010

PLoS ONE

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Retrotranspostion of I factors in the female germline of Drosophila melanogaster is responsible for the so called I-R hybrid dysgenesis, a phenomenon that produces a broad spectrum of genetic abnormalities including reduced fertility, increased frequency of mutations and chromosome loss. Transposition of I factor depends on cellular conditions that are established in the oocytes of the reactive females and transmitted to their daughters. The so-called reactivity is a cellular state that may exhibit variable levels of expression and represents a permissive condition for I transposition at high levels. Defective I elements have been proposed to be the genetic determinants of reactivity and, through their differential expression, to modulate transposition of active copies in somatic and/or germ line cells. Recently, control of transposable element activity in the germ line has been found to depend on pi-RNAs, small repressive RNAs interacting with Piwi-family proteins and derived from larger transposable elements (TE)-derived primary transcripts. In particular, maternally transmitted I-element piRNAs originating from the 42AB region of polytene chromosomes were found to be involved in control of I element mobility. In the present work, we use a combination of cytological and molecular approaches to study the activity of I elements in three sublines of the inducer y; cn bw; sp isogenic strain and in dysgenic and non-dysgenic genetic backgrounds. Overall, the results of FISH and Southern blotting experiments clearly show that I elements are highly unstable in the Montpellier subline in the absence of classical dysgenic conditions. Such instability appears to be correlated to the amount of 5′ and 3′ I element transcripts detected by quantitative and real-time RT-PCR. The results of this study indicate that I elements can be highly active in the absence of a dysgenic crosses. Moreover, in the light of our results caution should be taken to assimilate the genomic annotation data on transposable elements to all y; cn bw sp sublines.

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“…This phenomenon, known as hybrid dysgenesis, was attributed to the mobilization in dysgenic progeny of P -element or I -element transposons, which were present in wild-caught flies but absent from laboratory strains (4–9). The disparity in outcomes, depending on the parent of transposon origin, indicated the existence of cytoplasmically inherited determinants of the phenotype, which must be transmitted through the maternal germ line (8, 9). …”

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confidence: 99%

An Epigenetic Role for Maternally Inherited piRNAs in Transposon Silencing

Brennecke

Malone

Aravin

et al. 2008

Science

707

806

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In plants and mammals, small RNAs indirectly mediate epigenetic inheritance by specifying cytosine methylation. We found that small RNAs themselves serve as vectors for epigenetic information. Crosses between Drosophila strains that differ in the presence of a particular transposon can produce sterile progeny, a phenomenon called hybrid dysgenesis. This phenotype manifests itself only if the transposon is paternally inherited, suggesting maternal transmission of a factor that maintains fertility. In both P-and I-element-mediated hybrid dysgenesis models, daughters show a markedly different content of Piwi-interacting RNAs (piRNAs) targeting each element, depending on their parents of origin. Such differences persist from fertilization through adulthood. This indicates that maternally deposited piRNAs are important for mounting an effective silencing response and that a lack of maternal piRNA inheritance underlies hybrid dysgenesis.In Drosophila melanogaster, the progeny of intercrosses between wild-caught males and laboratory-strain females are sterile because of defects in gametogenesis, whereas the genetically identical progeny of wild-caught females and laboratory-strain males remain fertile (1-3). This phenomenon, known as hybrid dysgenesis, was attributed to the mobilization in dysgenic progeny of P-element or I-element transposons, which were present in wild-caught flies but absent from laboratory strains (4-9). The disparity in outcomes, depending on the parent of transposon origin, indicated the existence of cytoplasmically inherited determinants of the phenotype, which must be transmitted through the maternal germ line (8,9).The control of mobile elements in germ cells depends heavily on a small RNA-based immune system, composed of Piwi-family proteins (Piwi, Aubergine, and AGO3) and piRNAs (10,11). Both Piwi and Aubergine (Aub) are deposited into developing oocytes and accumulate in the pole plasm (12,13), implying possible transfer of maternal piRNAs into the germ lines of their progeny. We therefore asked whether maternally deposited small RNAs might affect transposon suppression in a heritable fashion and whether piRNAs might be the maternal suppressor of hybrid dysgenesis.

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I elements in <i>Drosophila:</i> in vivo retrotransposition and regulation

Cited by 23 publications

References 103 publications

piRNA-mediated nuclear accumulation of retrotransposon transcripts in the Drosophila female germline

piRNA-mediated nuclear accumulation of retrotransposon transcripts in the Drosophila female germline

Genomic Instability of I Elements of Drosophila melanogaster in Absence of Dysgenic Crosses

An Epigenetic Role for Maternally Inherited piRNAs in Transposon Silencing

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