microRNAs: tiny regulators of synapse function in development and disease

•  Introduction •  miRNA biogenesis and mode of action •  Regulation of miRNA expression •  miRNAs as regulators in the developing nervous system •  Synapse development and plasticity in vertebrates •  miRNAs as regulators in post‐mitotic neurons •  miRNA transport to the dendrite •  miRNAs in diseases of the nervous system ‐  Tourette's syndrome ‐  Spinal muscular atrophy ‐  Williams syndrome ‐  Rett syndrome ‐  Schizophrenia ‐  Neurodegenerative diseases ‐  Parkinson's disease ‐  Alzheimer's disease ‐  Triplet repeat expansion disorders ‐  Fragile X mental retardation syndrome ‐  Spinocerebellar ataxia type 3‐  Cancer in the CNS ‐  Genomic imprinting•  Diagnostic and therapeutic persDiagnostic and therapeutic perspectives •  ConclusionAbstract The development and function of neuronal circuits within the brain are orchestrated by sophisticated gene regulatory mechanisms. Recently, microRNAs have emerged as a novel class of small RNAs that fine‐tune protein synthesis. microRNAs are abundantly expressed in the vertebrate nervous system, where they contribute to the specification of neuronal cell identity. Moreover, microRNAs also play an important role in mature neurons. This review summarizes the current knowledge about the function of microRNAs in the nervous system with special emphasis on synapse formation and plasticity. The second part of this work will discuss the potential involvement of microRNAs in neurologic diseases. The study of brain microRNAs promises to expand our understanding of the mechanisms underlying higher cognitive functions and neurologic diseases.