A piRNA to Remember

In this issue of Cell, Rajasethupathy et al. report a surprising role for piRNAs, previously thought to act mainly in the animal germline to silence transposons, in transcriptional regulation of plasticity-related genes in the central nervous system of the sea slug Aplysia californica. The findings expand the functions of small RNAs and have important implications for our understanding of how transient signals can give rise to long-term memories.