Pseudogene-derived small interfering RNAs regulate gene expression in mouse oocytes.

Fritz Eckstein

Fritz Eckstein

Fritz Eckstein

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This is a most interesting publication as it identifies endogenous-siRNAs in mammals, specifically in mouse oocytes. Endo-siRNAs silence retrotransposons in plants and are derived from exogenous dsRNA (for example, after viral infection). However, in mammals, siRNAs have remained essentially unknown. Now, analysis of mouse oocytes for small RNAs identified siRNAs, in addition to piRNAs which had previously been detected in spermatocytes. Uo to now, endogenous siRNAs had been observed only in organisms possessing RNA-dependent RNA polymerase, which is absent in mammals. The endo-siRNAs in the mouse oocytes are apparently processed from dsRNAs formed by hybridisation of spliced transcripts of protein-coding genes to the antisense transcripts of homologous pseudogenes. Transposon-rich loci in oocytes give rise to both pi- and si-RNAs. These 2 RNA types might act redundantly to repress transposons. This publication is published back to back with one by Watanabe et al. {1}, which reports very similar findings (both papers cite each other). These publications add a new aspect to the regulation of development. Reference: {1} Watanabe et al. Nature 2008, Apr 10 [PMID:18404146].