The dramatic growth in the literature on the functions of small, non-coding RNA transcripts, termed microRNAs, has touched on every division of the biological sciences, with neuroscience being no exception. It is now widely recognized that microRNAs provide an extra level of gene regulation by binding to specific mRNA transcripts and preventing protein translation.

Recent years have seen the publication of a host of studies investigating the expression and function of microRNAs in the nervous system. Extensive research has concentrated on the role of microRNAs in development, where they have been shown to influence neuronal induction, patterning and cell specification; however, it is becoming apparent that these molecules might also contribute to the regulation of processes such as synaptic plasticity in the adult. The diverse range of microRNA functions in the adult brain is illustrated in a Research Highlight on page 908, which describes a study demonstrating the role of a hypothalamic microRNA, miR-7b, in osmoregulation.

In a review on page 911 of this issue, Kenneth Kosik explores our current knowledge of the roles of microRNAs in neuronal development, their functions in the mature nervous system and the links between microRNAs and neurological diseases. However, as Kosik points out, we still have many unanswered questions regarding the targets, mechanisms of action and functional effects of microRNAs in the nervous system. Kosik discusses these future challenges and the potential of advances in our understanding of the actions of microRNAs to cast light on a range of developmental events and neuronal functions.