Divergent composition and transposon-silencing activity of small RNAs in mammalian oocytes
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ABSTRACT:
SUBMITTER: Hou L
PROVIDER: S-EPMC10964541 | biostudies-literature | 2024 Jan
REPOSITORIES: biostudies-literature
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Project description:We found piRNAs with different lengths represented the predominant small RNA species in oocytes from the 12 explored species, except mouse. We found endo-siRNAs resulted from the truncated Dicer isoform were mouse-specific, and os-piRNAs associating with PIWIL3 in human oocytes are widespread in mammals and are typically with low levels of the 2’-3’-O-methylation. The sequences of many highly expressed piRNA clusters are fast-evolving compared with their syntenic genomic locations, and the TE families distributing in the conserved piRNA clusters are various between species.
2024-03-06 | GSE200470 | GEO
Project description:We found piRNAs with different lengths represented the predominant small RNA species in oocytes from the 12 explored species, except mouse. We found endo-siRNAs resulted from the truncated Dicer isoform were mouse-specific, and os-piRNAs associating with PIWIL3 in human oocytes are widespread in mammals and are typically with low levels of the 2’-3’-O-methylation. The sequences of many highly expressed piRNA clusters are fast-evolving compared with their syntenic genomic locations, and the TE families distributing in the conserved piRNA clusters are various between species.
2024-03-06 | GSE256514 | GEO
Project description:Divergent composition and transposon-silencing activity of small RNAs in mammalian oocytes
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Project description:Divergent composition and transposon-silencing activity of small RNAs in mammalian oocytes II
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Project description:Piwi-interacting RNAs (piRNAs), long thought to be restricted to germline, have recently been discovered in neurons of Aplysia, with a role in the epigenetic regulation of gene expression underlying long-term memory. We here ask whether piwi/piRNAs are also expressed and have functional roles in the mammalian brain. Large-scale RNA sequencing and subsequent analysis of protein expression revealed the presence in brain of several piRNA biogenesis factors including a mouse piwi (Mili), as well as small RNAs, albeit at low levels, resembling conserved piRNAs in mouse testes [primarily LINE1 (long interspersed nuclear element1) retrotransposon-derived]. Despite the seeming low expression of these putative piRNAs, single-base pair CpG methylation analyses across the genome of Mili/piRNA-deficient (Mili-/- ) mice demonstrate that brain genomic DNA is preferentially hypomethylated within intergenic areas and LINE1 promoter areas of the genome. Furthermore, Mili mutant mice exhibit behavioral deficits such as hyperactivity and reduced anxiety. These results suggest that putative piRNAs exist in mammalian brain, and similar to the role of piRNAs in testes, they may be involved in the silencing of retrotransposons, which in brain have critical roles in contributing to genomic heterogeneity underlying adaptation, stress response, and brain pathology. We also describe the presence of another class of small RNAs in the brain, with features of endogenous siRNAs, which may have taken over the role of invertebrate piRNAs in their capacity to target both transposons, as well as protein-coding genes. Thus, RNA interference through gene and retrotransposon silencing previously encountered in Aplysia may also have potential roles in the mammalian brain.
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Project description:It is currently thought that growing mammalian oocytes receive only small molecules via gap junctions from surrounding support cells, the granulosa cells. From the study of chimeric preantral oocyte and granulosa cell reaggregations, we provide evidence that growing mouse oocytes receive mRNAs from granulosa cells. Among the >1,000 granulosa-transcribed RNAs we identified in the oocyte, those that contribute to proper oocyte maturation and early embryo development were highly enriched. Predicted motifs for two RNA-binding proteins that function in RNA trafficking, FMRP and TDP43, were abundant in the UTRs of the granulosa-derived transcripts. Immunostaining demonstrated that both FMRP and TDP43 co-localize with the actin-rich granulosa cell protrusions that span the zone pellucida and connect to the oocyte, suggesting their role in importing mRNAs. Our results offer the possibility that oocyte failure may not always reflect an intrinsic oocyte deficiency but could arise from insufficient supply of maternal transcripts by granulosa cells during oocyte growth.
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Project description:In Drosophila, small interfering RNAs (siRNAs), which direct RNA interference through the Argonaute protein Ago2, are produced by a biogenesis pathway distinct from microRNAs (miRNAs), which regulate endogenous mRNA expression as guides for Ago1. Here, we report that siRNAs and miRNAs are sorted into Ago1 and Ago2 by pathways independent from the processes that produce these two classes of small RNAs. Such small-RNA sorting reflects the structure of the double-stranded assembly intermediates--the miRNA/miRNA( *) and siRNA duplexes--from which Argonaute proteins are loaded. We find that the Dcr-2/R2D2 heterodimer acts as a gatekeeper for the assembly of Ago2 complexes, promoting the incorporation of siRNAs and disfavoring miRNAs as loading substrates for Drosophila Ago2. A separate mechanism acts in parallel to favor miRNA/miRNA( *) duplexes and exclude siRNAs from assembly into Ago1 complexes. Thus, in flies small-RNA duplexes are actively sorted into Argonaute-containing complexes according to their intrinsic structures.
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Project description:In Drosophila, small interfering RNAs (siRNAs), which direct RNA interference through the Argonaute protein Ago2, are produced by a biogenesis pathway distinct from microRNAs (miRNAs), which regulate endogenous mRNA expression as guides for Ago1. Here, we report that siRNAs and miRNAs are sorted into Ago1 and Ago2 by pathways independent from the processes that produce these two classes of small RNAs. Such small-RNA sorting reflects the structure of the double-stranded assembly intermediates--the miRNA/miRNA( *) and siRNA duplexes--from which Argonaute proteins are loaded. We find that the Dcr-2/R2D2 heterodimer acts as a gatekeeper for the assembly of Ago2 complexes, promoting the incorporation of siRNAs and disfavoring miRNAs as loading substrates for Drosophila Ago2. A separate mechanism acts in parallel to favor miRNA/miRNA( *) duplexes and exclude siRNAs from assembly into Ago1 complexes. Thus, in flies small-RNA duplexes are actively sorted into Argonaute-containing complexes according to their intrinsic structures.
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Project description:Aedes aegypti and Ae. albopictus are the main vectors of mosquito-borne viruses of medical and veterinary significance. Many of these viruses have RNA genomes. Exogenously provided, e.g. transgene encoded, small RNAs could be used to inhibit virus replication, breaking the transmission cycle. We tested, in Ae. aegypti and Ae. albopictus cell lines, reporter-based strategies for assessing the ability of two types of small RNAs to inhibit a chikungunya virus (CHIKV) derived target. Both types of small RNAs use a Drosophila melanogaster pre-miRNA-1 based hairpin for their expression, either with perfect base-pairing in the stem region (shRNA-like) or containing two mismatches (miRNA-like). The pre-miRNA-1 stem loop structure was encoded within an intron; this allows co-expression of one or more proteins, e.g. a fluorescent protein marker tracking the temporal and spatial expression of the small RNAs in vivo. Three reporter-based systems were used to assess the relative silencing efficiency of ten shRNA-like siRNAs and corresponding miRNA-like designs. Two systems used a luciferase reporter RNA with CHIKV RNA inserted either in the coding sequence or within the 3' UTR. A third reporter used a CHIKV derived split replication system. All three reporters demonstrated that while silencing could be achieved with both miRNA-like and shRNA-like designs, the latter were substantially more effective. Dcr-2 was required for the shRNA-like siRNAs as demonstrated by loss of inhibition of the reporters in Dcr-2 deficient cell lines. These positive results in cell culture are encouraging for the potential use of this pre-miRNA-1-based system in transgenic mosquitoes.
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Project description:RNA interference (RNAi) is an evolutionarily conserved mechanism in plant and animal cells that directs the degradation of messenger RNAs homologous to short double-stranded RNAs termed small interfering RNA (siRNA). The ability of siRNA to direct gene silencing in mammalian cells has raised the possibility that siRNA might be used to investigate gene function in a high throughput fashion or to modulate gene expression in human diseases. The specificity of siRNA-mediated silencing, a critical consideration in these applications, has not been addressed on a genomewide scale. Here we show that siRNA-induced gene silencing of transient or stably expressed mRNA is highly gene-specific and does not produce secondary effects detectable by genomewide expression profiling. A test for transitive RNAi, extension of the RNAi effect to sequences 5' of the target region that has been observed in Caenorhabditis elegans, was unable to detect this phenomenon in human cells.
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