Somatic piRNA biogenesis

Piwi‐interacting RNAs (piRNAs) protect animal germ cells from transposons and other selfish genetic elements. Of the three types of animal small‐silencing RNAs—small‐interfering RNAs (siRNAs), microRNAs (miRNAs), and piRNAs—piRNAs are the least well understood, because we lack good tools for studying how they are made and how they function. Brennecke et al have now established a method for triggering RNA interference (RNAi) solely in Drosophila follicle cells, a specialized somatic cell that abuts the developing oocyte and which expresses a simplified version of the piRNA pathway present in animal germ cells. Their initial results already suggest a revision for our model of the piRNA pathway, and promise to accelerate the study of this enigmatic small RNA class.

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