Unmasking the messenger.

Synaptic plasticity, learning, and memory require high temporal and spatial control of gene expression. These processes are thought to rely mainly on asymmetric mRNA transport to synapses. Already in the early days of studying mRNA transport, Wilhelm and Vale proposed a multi-step process in 1993. Since then, we have gained important novel insights into how these individual steps are controlled by research performed in various cell types and organisms. Here, we present the latest view on how dendritic mRNA localization is achieved and how local translation at the synapse is regulated. In particular, we propose that the recently observed heterogeneity of RNA-protein particle assembly in neurons might be the key for how precise gene expression in the brain is achieved. In addition, we focus on latest data dealing with translational activation of translationally repressed mRNPs at a synapse that experiences learning-induced changes in its morphology and function. Together, these new findings shed new light on how precise regulatory mechanisms can lead to synaptic plasticity and memory formation.