Project description:23-29 nt Piwi-interacting RNAs (piRNAs) are crucial components of the ribonucleoprotein complexes which silence the most abundant class of mobile genetic elements in human genome, retrotransposons, in germline (germ) cells. In these cells, antisense piRNAs serve as RNA guides for Piwi proteins, base pairing with transposon RNAs which are subsequently cleaved by Piwi proteins. Germ cells belong to special class of stem cells which ultimately give rise to eggs and sperm and therefore, to next generations. Therefore, piRNAs protect next-generation genomes from devastating mutations caused by transposon insertions. Although, role of piRNAs in germ cells has been studied, functions of piRNAs and their associated proteins in somatic cells are not well understood. Importantly, Piwi proteins are expressed in the fruit fly Drosophila brain and are required for the silencing of transposable elements there, clearly indicating that Piwi-associated piRNAs are involved in this process in the brain. Furthermore, piRNAs have been implicated in the memory formation mechanisms in Aplysia brain. In addition to Piwi proteins, their associated partner, molecular scaffold Tudor protein, participates in piRNA biogenesis in germ cells and it is absolutely required for germline development. However, although tudor gene is expressed in the fly brain, its role in the central nervous system is not understood. In this study, we look at the role of Tudor as an essential player in piRNA biogenesis in Drosophila brain.
Project description:In Drosophila, Tudor protein and its germline partners, Piwi proteins, are expressed in the brain. However, the potential significance of Tudor in neurobiology has not been explored. Here, we test a hypothesis that Tudor is an essential regulator of post-transcriptional gene expression in the brain where it controls levels of certain RNAs required for brain functions. Specifically, transcriptome of tudor mutant brains is compared with that of wild-type brains using next-generation sequencing (RNA-Seq). The hypothesis that Tudor regulates the same genes in both brain and germline is tested by comparing the transcriptomes from tudor mutant brains and ovaries. This research aims at providing innovative outcomes which may reveal exciting commonalities between the germline and brain and may contribute to our understanding of neurodegenerative disorders and the mechanisms of learning and memory.
Project description:PIWI proteins and their bound piRNAs form the core of a gonad specific small RNA silencing pathway in animals that protects the genome against the deleterious activity of transposable elements. Recent studies linked the piRNA pathway to TUDOR biology, where TUDOR domains of various proteins recognize and bind symmetrically methylated Arginine residues in PIWI proteins. We systematically analyzed the Drosophila TUDOR protein family and identified three previously not characterized TUDOR domain-containing genes (CG4771, CG14303 and CG11133) as essential piRNA pathway members. We characterized CG4771 (Avocado) in detail and demonstrate a critical role for this protein during primary piRNA biogenesis in somatic and germline cells of the ovary. Avocado physically and/or genetically interacts with the primary pathway components Piwi, Armitage, Yb and Zucchini. Avocado also interacts with the Tdrd12 orthologs CG11133 and CG31755, which are essential for primary piRNA biogenesis in the germline and probably functionally replace the related and soma specific factor Yb. small RNA libraries were prepared from total RNA isolation of 8 different genotypes
Project description:PIWI proteins and their bound piRNAs form the core of a gonad specific small RNA silencing pathway in animals that protects the genome against the deleterious activity of transposable elements. Recent studies linked the piRNA pathway to TUDOR biology, where TUDOR domains of various proteins recognize and bind symmetrically methylated Arginine residues in PIWI proteins. We systematically analyzed the Drosophila TUDOR protein family and identified three previously not characterized TUDOR domain-containing genes (CG4771, CG14303 and CG11133) as essential piRNA pathway members. We characterized CG4771 (Avocado) in detail and demonstrate a critical role for this protein during primary piRNA biogenesis in somatic and germline cells of the ovary. Avocado physically and/or genetically interacts with the primary pathway components Piwi, Armitage, Yb and Zucchini. Avocado also interacts with the Tdrd12 orthologs CG11133 and CG31755, which are essential for primary piRNA biogenesis in the germline and probably functionally replace the related and soma specific factor Yb.
Project description:Drosophila Piwi-family proteins have been implicated in transposon control. Here, we examine piwi-interacting RNAs (piRNAs) associated with each Drosophila Piwi protein and find that Piwi and Aubergine bind RNAs that are predominantly antisense to transposons, whereas Ago3 complexes contain predominantly sense piRNAs. As in mammals, the majority of Drosophila piRNAs are derived from discrete genomic loci. These loci comprise mainly defective transposon sequences, and some have previously been identified as master regulators of transposon activity. Our data suggest that heterochromatic piRNA loci interact with potentially active, euchromatic transposons to form an adaptive system for transposon control. Complementary relationships between sense and antisense piRNA populations suggest an amplification loop wherein each piRNA-directed cleavage event generates the 5’ end of a new piRNA. Thus, sense piRNAs, formed following cleavage of transposon mRNAs, may enhance production of antisense piRNAs, complementary to active elements, by directing cleavage of transcripts from master control loci. Keywords: small RNA libraries from Drosophila ovaries
Project description:Drosophila Piwi-family proteins have been implicated in transposon control. Here, we examine piwi-interacting RNAs (piRNAs) associated with each Drosophila Piwi protein and find that Piwi and Aubergine bind RNAs that are predominantly antisense to transposons, whereas Ago3 complexes contain predominantly sense piRNAs. As in mammals, the majority of Drosophila piRNAs are derived from discrete genomic loci. These loci comprise mainly defective transposon sequences, and some have previously been identified as master regulators of transposon activity. Our data suggest that heterochromatic piRNA loci interact with potentially active, euchromatic transposons to form an adaptive system for transposon control. Complementary relationships between sense and antisense piRNA populations suggest an amplification loop wherein each piRNA-directed cleavage event generates the 5’ end of a new piRNA. Thus, sense piRNAs, formed following cleavage of transposon mRNAs, may enhance production of antisense piRNAs, complementary to active elements, by directing cleavage of transcripts from master control loci. Keywords: small RNA libraries from Drosophila ovaries small RNAs (23-29nt) were isolated from total ovarian RNA or from immunopreciptated Piwi/Aubergine/Ago3 complexes. cDNA libraries were constructed after Pfeffer et al. 2005 (Nat. Methods) and sequenced at 454 Life Sciences. The used strain is OregonR. Only sequences matching the Release5 genome assembly (www.fruitfly.org) are considered.
Project description:Piwi-interacting RNAs (piRNAs) suppress transposon activity in animal germ cells. In the Drosophila ovary, primary Aubergine (Aub)-bound antisense piRNAs initiate the ping-pong cycle to produce secondary AGO3-bound sense piRNAs. This increases the number of secondary Aub-bound antisense piRNAs that can act to destroy transposon mRNAs. Here we show that Krimper (Krimp), a Tudor-domain protein, directly interacts with piRNA-free AGO3 to promote symmetrical dimethylarginine (sDMA) modification, ensuring sense piRNA-loading onto sDMA-modified AGO3. In aub mutant ovaries, AGO3 associates with ping-pong signature piRNAs, suggesting AGO3’s compatibility with primary piRNA loading. Krimp sequesters ectopically expressed AGO3 within Krimp bodies in cultured ovarian somatic cells (OSCs), in which only the primary piRNA pathway operates. Upon krimp-RNAi in OSCs, AGO3 loads with piRNAs, further showing the capacity of AGO3 for primary piRNA loading. We propose that Krimp enforces an antisense bias on piRNA pools by binding AGO3 and blocking its access to primary piRNAs. In order to investigate function of Krimp in piRNA pathway, sequencing of Piwi subfamily protein associated small RNAs was performed using adult Drosophila ovaries and Ovarian Somatic Cells (OSCs) depleted for Krimp or Aub.
Project description:Belle has been known to be co-localized with piRNA-related proteins at the nuage of germline cells during Drosophila oogenesis. However, its role in piRNA biogenesis remains unclear. To reveal whether Belle is involved in regulating piRNA expression, we performed next-generation sequencing analysis of small non-coding RNAs on ovaries harvested from the wild type (W1118) and trans-heterozygous bel[74407/neo30] mutant. Small RNA-seq experiments were performed on three individual ovary samples with the same genotype. For piRNA expression analysis, we performed mapping of three sets of small RNA sequencing reads for each genotype to previously identified eight distinct piRNA clusters located in four different Drosophila chromosomes (from X to 4). Analysis of the piRNA expression profiling from these piRNA cluster loci indicates that some specific piRNA populations were either upregulated or downregulated in bel mutant ovaries compared with wild-type ovaries. Furthermore, we performed systematic analysis by mapping piRNA sequencing reads to sequences of all identified Drosophila transposable elements (TEs) to classify and measure piRNA reads based on their TE targets. Among 124 TE-classified piRNA populations, 9 and 20 of them were upregulated and downregulated (≥2 folds), respectively, in bel74407/neo30 mutant ovaries compared with those from wild-type ovaries. To examine the effect of the bel[74407/neo30] mutation on the ping-pong cycle for secondary piRNA biogenesis, analysis of the ping-pong signature of piRNAs specifically mapped to the retro-element Burdock was performed. The ping-pong signature for the generation of secondary piRNAs was not significantly altered in bel mutants compared with the wild type. These results, taken together, indicate that Bel is not required for primary and secondary piRNA biogenesis, but it is involved in regulating expression of specific subsets of piRNA populations.