Project description:Transposable elements are genomic parasites that expand within and spread between genomes. Piwi proteins control transposon activity, notably in the germline. These proteins recognize their targets through small RNA co-factors named piRNAs, making piRNA biogenesis a key specificity-determining step in this important genome immunity system. While the processing of piRNA precursors is an essential step in this process, many molecular details of this process remain unknown. We identify a novel endoribonuclease, PUCH, that initiates piRNA processing in the nematode Caenorhabditis elegans. Genetic and biochemical studies show that PUCH, a trimer of Schlafen-like-domain (SLFNL) proteins, executes 5ï‚¢-end piRNA precursor cleavage. PUCH-mediated processing strictly requires an m7G-Cap and a Uracil at position three. We also demonstrate how PUCH interacts with PETISCO, a complex that binds piRNA precursors, and that this interaction enhances piRNA production in vivo. The identification of PUCH completes the C. elegans piRNA biogenesis repertoire and uncovers a novel type of RNA endonuclease formed by three SLFL proteins. Mammalian Slfn genes have been associated with immunity responses, exposing a novel molecular link between immune responses in mammals and deeply conserved RNA-based mechanisms that control transposable elements.
Project description:Parkinson’s disease (PD), Parkinson’s disease with dementia (PDD) and dementia with Lewy bodies (DLB) are three clinically, genetically and neuropathologically overlapping neurodegenerative diseases collectively known as the Lewy body diseases (LBDs). A variety of molecular mechanisms have been implicated in PD pathogenesis, but the mechanisms underlying PDD and DLB remain largely unknown, a knowledge gap that presents an impediment to the discovery of diseasemodifying therapies. Transcriptomic profiling can contribute to addressing this gap, but remains limited in the LBDs. Here, we applied paired bulk-tissue and single-nucleus RNA-sequencing to anterior cingulate cortex samples derived from 28 individuals, including healthy controls, PD, PDD and DLB cases (n = 7 per group), to transcriptomically profile the LBDs. Using this approach, we (i) found transcriptional alterations in multiple cell types across the LBDs; (ii) discovered evidence for widespread dysregulation of RNA splicing, particularly in PDD and DLB; (iii) identified potential splicing factors, with links to other dementia-related neurodegenerative diseases, coordinating this dysregulation; and (iv) identified transcriptomic commonalities and distinctions between the LBDs that inform understanding of the relationships between these three clinical disorders. Together, these findings have important implications for the design of RNA-targeted therapies for these diseases and highlight a potential molecular “window” of therapeutic opportunity between the initial onset of PD and subsequent development of Lewy body dementia.
Project description:PIWI-interacting RNAs (piRNAs) promote fertility in many animals. Yet, whether this is due to their conserved role in repressing repetitive elements (REs) remains unclear. Here, we show that the progressive loss of fertility in Caenorhabditis elegans lacking piRNAs is not caused by derepression of REs or other piRNA targets, but rather mediated by the epigenetic silencing of all the replicative histone genes. In the absence of piRNAs, downstream components of the piRNA pathway relocalize from germ granules and piRNA targets to histone mRNAs to synthesize antisense small RNAs (sRNAs) and induce transgenerational silencing. Removal of the downstream components of the piRNA pathway restores histone mRNA expression and fertility in piRNA mutants, and the inheritance of histone sRNAs in wild-type worms adversely affects their fertility for multiple generations. We conclude that the sRNA-mediated silencing of histone genes impairs fertility of piRNA mutants and may serve to maintain piRNAs across evolution.
Project description:PIWI-interacting RNAs (piRNAs) promote fertility in many animals. Yet, whether this is due to their conserved role in repressing repetitive elements (REs) remains unclear. Here, we show that the progressive loss of fertility in Caenorhabditis elegans lacking piRNAs is not caused by derepression of REs or other piRNA targets, but rather mediated by the epigenetic silencing of all the replicative histone genes. In the absence of piRNAs, downstream components of the piRNA pathway relocalize from germ granules and piRNA targets to histone mRNAs to synthesize antisense small RNAs (sRNAs) and induce transgenerational silencing. Removal of the downstream components of the piRNA pathway restores histone mRNA expression and fertility in piRNA mutants, and the inheritance of histone sRNAs in wild-type worms adversely affects their fertility for multiple generations. We conclude that the sRNA-mediated silencing of histone genes impairs fertility of piRNA mutants and may serve to maintain piRNAs across evolution.
Project description:PIWI-interacting RNAs (piRNAs) promote fertility in many animals. Yet, whether this is due to their conserved role in repressing repetitive elements (REs) or other functions remains unclear. Here, we show that the progressive loss of fertility in Caenorhabditis elegans lacking piRNAs is not caused by derepression of REs or other piRNA targets, but rather mediated by the epigenetic silencing of all the replicative histone genes. In the absence of piRNAs, downstream components of the piRNA pathway relocalize from germ granules and piRNA targets to histone mRNAs to synthesize antisense small RNAs (sRNAs) and induce transgenerational silencing. Removal of the downstream components of the piRNA pathway is sufficient to restore histone mRNA expression and fertility in piRNA mutants, and the inheritance of histone sRNAs in wild-type worms adversely affects their fertility for multiple generations. We conclude that the transgenerational silencing of histone genes contributes to the progressive loss of fertility in piRNA mutants and that coupling piRNAs and histone silencing may serve to maintain piRNAs production across evolution.
Project description:piRNAs direct Piwi to repress transposons to maintain genome integrity in Drosophila ovarian somatic cells. piRNA maturation and association with Piwi occur at perinuclear Yb bodies, the centers of piRNA biogenesis. Here, we show that piRNA intermediates arising from the piRNA cluster flamenco (flam) concentrate into perinuclear foci adjacent to Yb bodies, termed Flam bodies. Although flam expression is not required for Yb body formation, Yb, the core component of Yb bodies, is required for Flam body formation. Abolishment of the RNA-binding activity of Yb disrupts both Yb bodies and Flam bodies. Loss of Zucchini, an endoribonuclease necessary for piRNA maturation, enlarges Flam bodies, which now superimpose with Yb bodies. Yb directly binds flam, but not neighboring protein-coding gene, transcripts. Thus, Yb integrates piRNA processing factors and piRNA intermediates into Yb bodies and Flam bodies, respectively, through direct binding to enhance piRNA biogenesis and formation of piRNA-inducing silencing complexes.
Project description:piRNAs direct Piwi to repress transposons to maintain genome integrity in Drosophila ovarian somatic cells. piRNA maturation and association with Piwi occur at perinuclear Yb bodies, the centers of piRNA biogenesis. Here, we show that piRNA intermediates arising from the piRNA cluster flamenco (flam) concentrate into perinuclear foci adjacent to Yb bodies, termed Flam bodies. Although flam expression is not required for Yb body formation, Yb, the core component of Yb bodies, is required for Flam body formation. Abolishment of the RNA-binding activity of Yb disrupts both Yb bodies and Flam bodies. Loss of Zucchini, an endoribonuclease necessary for piRNA maturation, enlarges Flam bodies, which now superimpose with Yb bodies. Yb directly binds flam, but not neighboring protein-coding gene, transcripts. Thus, Yb integrates piRNA processing factors and piRNA intermediates into Yb bodies and Flam bodies, respectively, through direct binding to enhance piRNA biogenesis and formation of piRNA-inducing silencing complexes. HITS-CLIP was performed using OSC (Ovarian Somatic Cells). The antibody for Drosophila Yb, which was generated in this study, was used. Obtained CLIP tags were analyzed using illumina HiSeq200.