The neuronal microRNA system.

A class of small, non-coding transcripts called microRNAs (miRNAs) that provide a crucial and pervasive layer of post-transcriptional gene regulation has recently emerged and become the focus of intense research. miRNAs are abundant in the nervous system, where they have key roles in development and are likely to be important mediators of plasticity. A highly conserved pathway of miRNA biogenesis is closely linked to the transport and translatability of mRNAs in neurons. Although there are nearly 500 known human miRNA sequences, each of only approximately 21 nucleotides, which bind to multiple mRNA targets, the accurate prediction of miRNA targets seems to lie just beyond our grasp. Nevertheless, the identification of such targets promises to provide new insights into many facets of neuronal function.