Pachytene piRNAs as beneficial regulators or a defense system gone rogue

Pachytene Piwi-interacting RNAs (piRNAs) are abundant small non-coding RNAs expressed in mammalian germ lines. A new study indicates that, among the diverse pool of piRNA sequences, a small number act as highly selective guides that induce cleavage of coding and non-coding transcripts, thus promoting piRNA generation and regulating gene expression.