Project description:Epigenetic modifications that arise during plant and animal development, such as DNA and histone modification, are mostly reset during gamete formation, but some are inherited from the germline including those marking imprinted genes. Small RNAs guide these epigenetic modifications, and some are also inherited by the next generation. In C. elegans, inherited small RNA precursors have poly (UG) tails, but how inherited small RNAs are distinguished in other animals and plants is unknown. Pseudouridine (Ψ) is the most abundant RNA modification but has not been explored in small RNAs. Here, we develop novel assays to detect Ψ in short RNA sequences, demonstrating its presence in mouse and Arabidopsis microRNAs and their precursors. We also detect substantial enrichment in germline small RNAs, namely epigenetically activated siRNAs (easiRNAs) in Arabidopsis pollen, and piwi-interacting piRNAs in mouse testis. In pollen, pseudouridylated easiRNAs are localized to sperm cells, and we found that PAUSED/HEN5 (PSD), the plant homolog of Exportin-t, interacts genetically with Ψ and is required for transport of easiRNAs into sperm cells from the vegetative nucleus. We further show that Exportin-t is required for the triploid block: chromosome dosage-dependent seed lethality that is epigenetically inherited from pollen. Thus, Ψ has a conserved role in marking inherited small RNAs in the germline.
Project description:Epigenetic modifications that arise during plant and animal development, such as DNA and histone modification, are mostly reset during gamete formation, but some are inherited from the germline including those marking imprinted genes. Small RNAs guide these epigenetic modifications, and some are also inherited by the next generation. In C. elegans, these inherited small RNAs have poly (UG) tails, but how inherited small RNAs are distinguished in other animals and plants is unknown. Pseudouridine (Ψ) is the most abundant RNA modification but has not been explored in small RNAs. Here, we developed novel assays to detect Ψ in short RNA sequences, demonstrating its presence in mouse and Arabidopsis microRNAs and their precursors. We also detected substantial enrichment in germline small RNAs, namely epigenetically activated siRNAs (easiRNAs) in Arabidopsis pollen, and PIWI-interacting piRNAs in mouse testis. In pollen, pseudouridylated easiRNAs are produced by RNA polymerase IV and localized to sperm cells. We found that PAUSED/HEN5 (PSD), the plant homolog of Exportin-t, interacts genetically with Ψ synthase and is required for transport of easiRNAs into sperm cells from the vegetative nucleus. We further show that PSD is required for the triploid block: chromosome dosage-dependent seed lethality that is epigenetically inherited from pollen. We propose that Ψ has a conserved role in marking inherited small RNAs in the germline.
Project description:Pseudouridine (Ψ) is an isomer of uridine found in ribosomal, transfer and other structural RNAs as well as in some mRNAs and non-coding RNAs, but is difficult to detect in short RNA sequences. Using modified techniques we found Ψ in microRNAs (miRNAs) and their precursors from mammalian and plant cells, primarily at the 5ʹ terminus of the mature miRNA. Small RNAs targeting transposons in reproductive cells (piRNA in testis and easiRNA in pollen) were highly enriched for Ψ, indicating a potential role in epigenetic inheritance. In pollen, pseudouridylated small RNAs were produced by RNA polymerase IV and were localized to sperm cells, as were miRNAs with terminal Ψ. We show that pseudouridylated easiRNAs from pollen contribute to imprinting and the triploid block (chromosome dosage-dependent epigenetic lethality) via the activity of PAUSED/HEN5, the plant homolog of Exportin-t. Exportin-t is required for nuclear export of pseudouridylated tRNA, and we found that PSD is required for cell-cell transport of small RNA in the germline.
Project description:Epigenetic inheritance is more widespread in plants than in mammals, in part because mammals erase epigenetic information each generation by germline reprogramming. To assess the extent of germline reprogramming in plants, we sequenced the methylome of three haploid cell types from developing pollen: the sperm cell (SC), the vegetative cell, and their precursor the post-meiotic microspore. Whole genome bisulfite sequencing of FACS-purified sperm cells, vegetative nuclei and microspores
Project description:Epigenetic inheritance is more widespread in plants than in mammals, in part because mammals erase epigenetic information each generation by germline reprogramming. To assess the extent of germline reprogramming in plants, we sequenced the methylome of three haploid cell types from developing pollen: the sperm cell (SC), the vegetative cell, and their precursor the post-meiotic microspore.
Project description:dsRNA-mediated gene silencing (RNAi) can be inherited for multiple generations in C. elegans. To understand this process we conducted a genetic screen for animals defective for transmitting RNAi silencing signals to future generations. This screen identified the gene heritable RNAi defective (hrde)-1. hrde-1 encodes an Argonaute (Ago) that associates with siRNAs in germ cells of the progeny of animals exposed to dsRNA. In nuclei of these germ cells, HRDE-1 engages the Nrde nuclear RNAi pathway to promote RNAi inheritance, and directs H3K9me3 chromatin marks at RNAi targeted genomic loci. Under normal growth conditions, HRDE-1 associates with endogenously expressed small RNAs, which direct nuclear gene silencing in germ cells. In RNAi inheritance mutant animals, silencing is lost over generational time. Concurrently, RNAi inheritance mutant animals exhibit progressively worsening germline defects that ultimately lead to sterility. These results establish that the Ago HRDE-1 directs gene-silencing events in germ cell nuclei, which are required for multi-generational RNAi inheritance and immortality of the germ cell lineage. We propose that C. elegans use the RNAi inheritance machinery to transmit epigenetic information, accrued by past generations, into future generations to ensure immortality of the germ cell lineage. H3K9me3 Chip-IP for C. elegans strains nrde-3, nrde-4, glp-4. Small RNA-seq for small RNAs co-immunoprecipitated with HRDE-1
Project description:Background: Defining the mechanisms that establish and regulate the transmission of epigenetic information from parent to offspring is critical for understanding disease heredity. Currently, the molecular pathways that regulate epigenetic information in the germline and its transmission to offspring are poorly understood. Results: Here we provide evidence that Polycomb Repressive Complex 2 (PRC2) regulates paternal inheritance, both at the phenotypic and molecular levels. Reduced PRC2 function in mice resulted in male sub-fertility and altered epigenetic and transcriptional control of retrotransposed elements in fetal male germ cells. Males with reduced PRC2 function produced offspring that over-expressed retrotransposed pseudogenes and had altered preimplantation embryo cleavage rates and cell cycle control. Conclusion: This study reveals a novel role for the histone modifying complex, PRC2, in epigenetic inheritance, with important implications for understanding disease inheritance.
Project description:dsRNA-mediated gene silencing (RNAi) can be inherited for multiple generations in C. elegans. To understand this process we conducted a genetic screen for animals defective for transmitting RNAi silencing signals to future generations. This screen identified the gene heritable RNAi defective (hrde)-1. hrde-1 encodes an Argonaute (Ago) that associates with siRNAs in germ cells of the progeny of animals exposed to dsRNA. In nuclei of these germ cells, HRDE-1 engages the Nrde nuclear RNAi pathway to promote RNAi inheritance, and directs H3K9me3 chromatin marks at RNAi targeted genomic loci. Under normal growth conditions, HRDE-1 associates with endogenously expressed small RNAs, which direct nuclear gene silencing in germ cells. In RNAi inheritance mutant animals, silencing is lost over generational time. Concurrently, RNAi inheritance mutant animals exhibit progressively worsening germline defects that ultimately lead to sterility. These results establish that the Ago HRDE-1 directs gene-silencing events in germ cell nuclei, which are required for multi-generational RNAi inheritance and immortality of the germ cell lineage. We propose that C. elegans use the RNAi inheritance machinery to transmit epigenetic information, accrued by past generations, into future generations to ensure immortality of the germ cell lineage.