Project description:In Drosophila, Piwi proteins associate with Piwi-interacting RNAs (piRNAs) and protect the germline genome by silencing mobile genetic elements. This defense system acts in germline and gonadal somatic tissue to preserve germline development. Genetic control for these silencing pathways varies greatly between tissues of the gonad. Here, we identified Vreteno (Vret), a novel gonad-specific protein essential for germline development. Vret is required for piRNA-based transposon regulation in both germline and somatic gonadal tissues. We show that Vret, which contains Tudor domains, associates physically with Piwi and Aubergine (Aub), stabilizing these proteins via a gonad-specific mechanism, absent in other fly tissues. In the absence of vret, Piwi-bound piRNAs are lost without changes in piRNA precursor transcript production, supporting a role for Vret in primary piRNA biogenesis. In the germline, piRNAs can engage in an Aub/Argonaute 3 (AGO3)-dependent amplification in the absence of Vret, suggesting that Vret function can distinguish between primary piRNAs loaded into Piwi/Aub complexes and piRNAs engaged in the amplification cycle. We propose that Vret acts at an early step in primary piRNA processing where it plays an essential role in transposon regulation. These studies show that vreteno (vret) has a role in germline development and primary piRNA regulation in Drosophila. Transposable element expression profiles from Drosophila ovaries mutant for vreteno, piwi and aubergine were compared using genome-wide mRNA expression profiling by Affymetrix GeneChip arrays (Drosophila 2.0). Key targets were validated by qPCR experiments.
Project description:In Drosophila, Piwi proteins associate with Piwi-interacting RNAs (piRNAs) and protect the germline genome by silencing mobile genetic elements. This defense system acts in germline and gonadal somatic tissue to preserve germline development. Genetic control for these silencing pathways varies greatly between tissues of the gonad. Here, we identified Vreteno (Vret), a novel gonad-specific protein essential for germline development. Vret is required for piRNA-based transposon regulation in both germline and somatic gonadal tissues. We show that Vret, which contains Tudor domains, associates physically with Piwi and Aubergine (Aub), stabilizing these proteins via a gonad-specific mechanism, absent in other fly tissues. In the absence of vret, Piwi-bound piRNAs are lost without changes in piRNA precursor transcript production, supporting a role for Vret in primary piRNA biogenesis. In the germline, piRNAs can engage in an Aub/Argonaute 3 (AGO3)-dependent amplification in the absence of Vret, suggesting that Vret function can distinguish between primary piRNAs loaded into Piwi/Aub complexes and piRNAs engaged in the amplification cycle. We propose that Vret acts at an early step in primary piRNA processing where it plays an essential role in transposon regulation. These studies show that vreteno (vret) has a role in germline development and primary piRNA regulation in Drosophila.
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:The piRNA pathway is studied in great detail in Drosophila female germline. In this study we show that unlike the female germline where all Piwi proteins are expressed throughout oogenesis, Ago3 - a Piwi family protein shows a spatial expression male germline. To understand dynamics of piRNA pathway during spermatogonia and primary spermatocyte stages of male germline development, we used arrest mutants. The bag of marbles (bam) and benign gonial cell neoplasm (bgcn) mutants have only early mitotic dividing germline cells in the testes due to failure to progress to primary spermatocyte stage, the cannonball (can) and spermatocyte arrest (sa) mutant germline cells cannot progress beyond primary spermatocyte stage. To investigate the dynamics of the piRNA pathway during spermatogenesis in spermatogonia and primary spermatocyte stages, we used testicular tissues from these stage-specific arrested mutants. While we used entire bam and bgcn mutant testes for spermatogonia purification, we while we manually removed the apical regions of can and sa mutant testes to exclude mitotically dividing undifferentiated germline cells for primary spermatocytes purification. Our results show that piRNAs mapping to transposons are more abundant in spermatogonia, whereas those mapping to Suppressor of Stellate [Su(Ste)] and AT-chX are mostly expressed in primary spermatocytes. Furthermore we observed that transposon-mapping piRNAs with ping-pong signature are more abundant in spermatogonia albeit still detectable in primary spermatocytes where Ago3 is not expressed. These results suggest that robust piRNA production via ping-pong cycle takes place in spermatogonia, and to a lesser extent in primary spermatocytes even in the absence of Ago3. Consistently, piRNAs from ago3 mutant testes also exhibit the ping-pong signature, confirming that a non-canonical ping-pong cycle is acting during spermatogenesis. Our study provides a developmental dimension to the piRNA pathway and uncovers a new mechanism used in the male germline to silence transposons.
Project description:The piRNA pathway is studied in great detail in Drosophila female germline. In this study we show that unlike the female germline where all Piwi proteins are expressed throughout oogenesis, Ago3 - a Piwi family protein shows a spatial expression male germline. To understand dynamics of piRNA pathway during spermatogonia and primary spermatocyte stages of male germline development, we used arrest mutants. The bag of marbles (bam) and benign gonial cell neoplasm (bgcn) mutants have only early mitotic dividing germline cells in the testes due to failure to progress to primary spermatocyte stage, the cannonball (can) and spermatocyte arrest (sa) mutant germline cells cannot progress beyond primary spermatocyte stage. To investigate the dynamics of the piRNA pathway during spermatogenesis in spermatogonia and primary spermatocyte stages, we used testicular tissues from these stage-specific arrested mutants. While we used entire bam and bgcn mutant testes for spermatogonia purification, we while we manually removed the apical regions of can and sa mutant testes to exclude mitotically dividing undifferentiated germline cells for primary spermatocytes purification. Our results show that piRNAs mapping to transposons are more abundant in spermatogonia, whereas those mapping to Suppressor of Stellate [Su(Ste)] and AT-chX are mostly expressed in primary spermatocytes. Furthermore we observed that transposon-mapping piRNAs with ping-pong signature are more abundant in spermatogonia albeit still detectable in primary spermatocytes where Ago3 is not expressed. These results suggest that robust piRNA production via ping-pong cycle takes place in spermatogonia, and to a lesser extent in primary spermatocytes even in the absence of Ago3. Consistently, piRNAs from ago3 mutant testes also exhibit the ping-pong signature, confirming that a non-canonical ping-pong cycle is acting during spermatogenesis. Our study provides a developmental dimension to the piRNA pathway and uncovers a new mechanism used in the male germline to silence transposons. The difference in piRNA from spermatogonia and primary spermatocyte stages was studied by comparing small RNAs from bam and bgcn mutant testis, which represent spermatogonia stages with the small RNAs from apex removed can and sa testis, representing primary spermatocyte stages. In the study we also studied effect of loss of Piwi family proteins Aub and Ago3, which have different spatial expression during male germline development.
Project description:The Drosophila piRNA pathway provides an RNA-based immune system that defends the germline genome against selfish genetic elements. Two inter-related branches of the piRNA system exist: somatic cells that support oogenesis only employ Piwi, whereas germ cells utilize a more elaborated pathway centered on the three gonad-specific Argonaute proteins Piwi, Aubergine, and Argonaute3. While several key factors of each branch have been identified, our current knowledge is insufficient to explain the complex workings of the piRNA machinery. Here, we report a reverse genetic screen spanning the ovarian transcriptome in an attempt to uncover the full repertoire of genes required for piRNA-mediated transposon silencing in the female germline. Our screen reveals new key factors of piRNA-mediated transposon silencing, including the novel piRNA biogenesis factors, CG2183 (GASZ) and Deadlock. Last, our data uncovers a previously unanticipated set of factors preferentially required for repression of different transposons types. Examination of small RNA levels from nos-GAL4 or tj-GAL4 driven UAS-dsRNA knockdowns of control genes and piRNA pathway components in ovaries of Drosophila melanogaster by deep sequencing (using Illumina HiSeq2000).
Project description:The Drosophila piRNA pathway provides an RNA-based immune system that defends the germline genome against selfish genetic elements. Two inter-related branches of the piRNA system exist: somatic cells that support oogenesis only employ Piwi, whereas germ cells utilize a more elaborated pathway centered on the three gonad-specific Argonaute proteins Piwi, Aubergine, and Argonaute3. While several key factors of each branch have been identified, our current knowledge is insufficient to explain the complex workings of the piRNA machinery. Here, we report a reverse genetic screen spanning the ovarian transcriptome in an attempt to uncover the full repertoire of genes required for piRNA-mediated transposon silencing in the female germline. Our screen reveals new key factors of piRNA-mediated transposon silencing, including the novel piRNA biogenesis factors, CG2183 (GASZ) and Deadlock. Last, our data uncovers a previously unanticipated set of factors preferentially required for repression of different transposons types. Examination of total RNA levels from nos-GAL4 or tj-GAL4 driven UAS-dsRNA knockdowns of control genes and piRNA pathway components in ovaries of Drosophila melanogaster by deep sequencing (using Illumina HiSeq2000).