Watanabe, T. et al. Identification and characterization of two novel classes of small RNAs in the mouse germline: retrotransposon-derived siRNAs in oocytes and germline small RNAs in testes. Genes Dev. 20, 1732-1743

Laboratory of Reproductive Biology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Genes & Development (Impact Factor: 10.8). 08/2006; 20(13):1732-43. DOI: 10.1101/gad.1425706
Source: PubMed


Small RNAs ranging in size between 18 and 30 nucleotides (nt) are found in many organisms including yeasts, plants, and animals. Small RNAs are involved in the regulation of gene expression through translational repression, mRNA degradation, and chromatin modification. In mammals, microRNAs (miRNAs) are the only small RNAs that have been well characterized. Here, we have identified two novel classes of small RNAs in the mouse germline. One class consists of approximately 20- to 24-nt small interfering RNAs (siRNAs) from mouse oocytes, which are derived from retroelements including LINE, SINE, and LTR retrotransposons. Addition of retrotransposon-derived sequences to the 3' untranslated region (UTR) of a reporter mRNA destabilizes the mRNA significantly when injected into full-grown oocytes. These results suggest that retrotransposons are suppressed through the RNAi pathway in mouse oocytes. The other novel class of small RNAs is 26- to 30-nt germline small RNAs (gsRNAs) from testes. gsRNAs are expressed during spermatogenesis in a developmentally regulated manner, are mapped to the genome in clusters, and have strong strand bias. These features are reminiscent of Tetrahymena approximately 23- to 24-nt small RNAs and Caenorhabditis elegans X-cluster small RNAs. A conserved novel small RNA pathway may be present in diverse animals.

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Available from: Toshiaki Watanabe, May 13, 2014
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    • "These small RNAs are derived from long, perfectly complementary double-stranded RNAs that are formed through sense-antisense transcript pairs, long stem-loop structures and transposon transcripts (Golden et al. 2008). Their processing is Drosha/DGCR8 independent but requires multiple Dicer cleavages along the precursor RNA (Watanabe et al. 2006, Tam et al. 2008). For quite some time it was believed that endo-siRNAs do not exist in vertebrates, because Dicer was believed to act exclusively in the cytoplasm, and cytoplasmic long dsRNAs trigger a strong immune response though protein kinase R. "
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    • "Oocytes contain large amounts of RNA of all classes (Watanabe et al., 2006, 2008; Tam et al., 2008). Previous studies have demonstrated that maternal non-coding RNAs can be stable for several cell divisions and contribute to gene regulation in early development (Suh and Blelloch, 2011). "
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    • "These observations suggest that retrotransposons are suppressed by piRNA pathway posttranscriptionally in vertebrate oocytes. In mouse oocytes, insertion of transposon sequences confers instability to reporter mRNAs (Watanabe et al., 2006). A recent study revealed that some transposon-driven mRNAs harboring transposon sequences in their 5 0 UTRs are upregulated in Mvh, "
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