Activity-dependent spatially localized miRNA maturation in neuronal dendrites

Intraneuronal control of protein expression In cells and tissues, mRNA copy numbers far exceed the number of micro RNAs (miRNAs). How then can a miRNA effectively regulate translation of a particular target mRNA? Sambandan et al. used high-resolution in situ hybridization to detect precursor miRNA in rat neuronal dendrites. They introduced a fluorescent miRNA maturation reporter into hippocampal neurons and detected activity-dependent maturation of the probe in both the soma and dendrites. This local maturation of the miRNA was indeed associated with a local reduction in protein synthesis. Thus, localized miRNA maturation can modulate target gene expression with local and temporal precision. Science , this issue p. 634