Regulation of neuronal differentiation through miRNAs. The neural factor NF, such as a neurotrophin (BDNF, NGF) or a neurotransmitter (glutamate, serotonin), interacts with its receptor, activating a signalling cascade that switches on transcription of selected neural genes, including specific miRNA genes as well. miRNAs, in turn, can inhibit translation of proteins regulating neuronal development, for instance a neural repressor protein. Such a regulated circuit of gene expression has been recently demonstrated for neuronal morphogenesis triggered by the cAMP-response element binding protein CREB . This transcriptional activator has a central role in neural specific gene expression, being implicated in many neuronal processes like differentiation, plasticity, LPT, and memory formation. miR 132, whose transcription is activated by neurotrophins and is under direct CREB control, interacts with 3'UTR of the mRNA coding for the GTPase-activating protein p250GAP. This protein is a repressor of neuronal differentiation: its inhibition promotes neurite outgrowth.