Small RNA-mediated transgenerational silencing of histone genes impairs fertility in piRNA mutants (sRNA-Seq IP)
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ABSTRACT: 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: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) 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:The ability to distinguish non-self from self is the key characteristic for any defense system. piRNAs function as guardians of the genome by silencing non-self nucleic acids and transposable elements in animals. Many piRNA factors are enriched in perinuclear germ granules, but whether their localization is required for piRNA biogenesis or function is not known. Here we show that GLH/VASA helicase mutants exhibit defects in forming perinuclear condensates containing PIWI and other small RNA cofactors. These mutant animals produce largely normal levels of piRNA but are defective in triggering piRNA silencing. Strikingly, while many piRNA targets are activated in GLH mutants, we observed that hundreds of endogenous genes are aberrantly silenced by piRNAs. This defect in self versus non-self recognition was also observed in other mutants where perinuclear P granules are disrupted. Together, our results argue that perinuclear germ granules function critically to promote the fidelity of piRNA-based transcriptome surveillance in C. elegans and preserve self versus non-self distinction.
Project description:piRNAs are required to maintain germline integrity and fertility but their mechanism of action is poorly understood. Here we demonstrate that C. elegans piRNAs silence transcripts in trans through imperfectly complementary sites. We find that target silencing is independent of Piwi endonuclease activity or “slicing”. Instead, we show that piRNAs initiate a localized secondary endogenous small interfering RNA (endo-siRNA) response. Endogenous protein-coding gene, pseudogene and transposon transcripts exhibit Piwi-dependent endo-siRNAs at sites complementary to piRNAs and are derepressed in Piwi mutants. Genomic loci of piRNA biogenesis are depleted of protein-coding genes but not pseudogenes or transposons. Our data suggest that nematode piRNA clusters are evolving to generate piRNAs against active mobile elements. Thus, piRNAs provide heritable, sequence-specific triggers for RNAi in C. elegans. Affymetrix mRNA expression data from wild-type and two independent prg-1;prg-2 double mutant C. elegans strains (mRNA)
Project description:piRNAs are required to maintain germline integrity and fertility but their mechanism of action is poorly understood. Here we demonstrate that C. elegans piRNAs silence transcripts in trans through imperfectly complementary sites. We find that target silencing is independent of Piwi endonuclease activity or “slicing”. Instead, we show that piRNAs initiate a localized secondary endogenous small interfering RNA (endo-siRNA) response. Endogenous protein-coding gene, pseudogene and transposon transcripts exhibit Piwi-dependent endo-siRNAs at sites complementary to piRNAs and are derepressed in Piwi mutants. Genomic loci of piRNA biogenesis are depleted of protein-coding genes but not pseudogenes or transposons. Our data suggest that nematode piRNA clusters are evolving to generate piRNAs against active mobile elements. Thus, piRNAs provide heritable, sequence-specific triggers for RNAi in C. elegans.
Project description:piRNAs are required to maintain germline integrity and fertility but their mechanism of action is poorly understood. Here we demonstrate that C. elegans piRNAs silence transcripts in trans through imperfectly complementary sites. We find that target silencing is independent of Piwi endonuclease activity or “slicing”. Instead, we show that piRNAs initiate a localized secondary endogenous small interfering RNA (endo-siRNA) response. Endogenous protein-coding gene, pseudogene and transposon transcripts exhibit Piwi-dependent endo-siRNAs at sites complementary to piRNAs and are derepressed in Piwi mutants. Genomic loci of piRNA biogenesis are depleted of protein-coding genes but not pseudogenes or transposons. Our data suggest that nematode piRNA clusters are evolving to generate piRNAs against active mobile elements. Thus, piRNAs provide heritable, sequence-specific triggers for RNAi in C. elegans.
Project description:Piwi-interacting RNAs (piRNAs) play essential roles in silencing repetitive elements to promote fertility in metazoans. Nearly one-third of the ~15,000 piRNA loci in the C. elegans hermaphrodite are enriched during spermatogenesis, whereas >2,000 piRNAs are enriched during oogenesis. However, the mechanism underlying this sex-specific regulation is unknown. Here we identify SNPC-1.3, a variant of a conserved subunit of the snRNA activating protein complex, as a male-specific piRNA transcription factor. Binding of SNPC-1.3 at male piRNA loci drives spermatogenic piRNA transcription and requires the core piRNA transcription factor SNPC-4. Loss of snpc-1.3 leads to depletion of spermatogenic piRNAs and defects in male-dependent fertility. Furthermore, TRA-1, a master regulator of sex determination, binds to the snpc-1.3 promoter and represses its expression during oogenesis. Loss of TRA-1 targeting causes ectopic expression of snpc-1.3 and male piRNAs during oogenesis. Thus, sexual dimorphic regulation of snpc-1.3 coordinates male and female piRNA expression during germline development.