In addition to their role in brain development, miRNAs also play a key role in adult brain function. By combining laser capture with multiplex real-time PCR, hundreds of miRNAs have been shown to demonstrate somatodendritic localization within mature neurons.85 Based on this spatial pattern of expression, it is likely that miRNAs also play a role in the later stages of neuronal maturation and synapse formation.77,78 Indeed, miRNAs can be transported away from their site of formation in the cell body of neurons to points of synaptic contact, implying a role for such miRNAs in synaptic development and plasticity.86 Memory formation in Drosophila can drive degradation of the RISC-associated protein Armitage that is localized to the synapse.87 This action results in the release of mRNAs (eg, CaMKII mRNA) that had been targeted for degradation in a RISC-dependent manner87 and induction of memory-dependent protein synthesis.87 In addition to Armitage, and its mammalian equivalent, Moloney leukemia virus 10 MOV10, several other important components of the miRNA biosynthesis cascade, such as Fragile X mental retardation protein (FMRP),88-90 are also localized to sites of synaptic
