miRNAs: from neurogeneration to neurodegeneration.

miRNAs are reported to sequence-specifically control the translation of target mRNAs by binding to 3 UTRs. The abundant expression of miRNAs in the brain highlights their biological significance in neurodevelopment. Many studies have shown that miRNAs are involved in a variety of functions, including developmental transitions and neuronal patterning, apoptosis, fat metabolism and regulation of hematopoietic lineage differentiation in different organisms. miRNAs act as regulatory switches in the determination of developmental fate through their distinct patterns of expression. The tissue-specific expression of miRNAs during brain development could possibly direct the development of cells in different subtypes. Several miRNAs are localized to neuronal subtypes and exhibit a more diverse or specific expression pattern within various neuronal cell types such as glial cells and neuronal progenitor cells. Perturbations in the expression pattern of miRNAs could lead to defects in human brain development and neurological disorders. The bioinformatic prediction tools suggest that some genes involved in synaptic formations and mental retardation are putative targets for miRNAs. miRNAs have been shown to specify cell fates in the nervous system of worms and brain morphogenesis in fish, and their distinct expression patterns during mammalian brain development. This suggests a potential role of miRNAs in neurodevelopment of mammals and other organisms. In this review, I have focused on the role of miRNAs in brain development and possible neurological disorders.