The brain may be a particularly prominent organ within which miRNAs play an important role in controlling gene expression and neuronal activity. In a study by Miska et al. it was established that there was considerable abundance of miRNAs in rodent and primate brain (Miska et al., 2004). Further, they developed a microarray-based method to monitor the spatiotemporal expression of miRNAs during mouse brain development and found that there was a dynamic change in miRNA expression levels during development. As a result of these new methodologies there have been more than 300 miRNAs identified in adult mouse brain. Of these brain-enriched miRNAs some are present ubiquitously whereas others are expressed in a cell specific manner (Bak et al., 2008).
