Secreted miRNAs in the tripartite neuromuscular junction

microRNAs are small, non-coding, single-stranded RNAs that can suppress mRNA translation at the posttranscriptional level by binding to imperfect complementary sequences on mRNA targets and then cause their degradation or hinder protein translation. Recently, bunch of evidence showed that microRNAs (miRNAs) existed in presynaptic and postsynaptic parts and implicated in the synapses formation and pruning during development and the modulation of synaptic plasticity in the adult stage. Besides working intracellularly, we previous reported that miRNAs also could be secreted and became extracellular miRNAs, these extracellular miRNAs could be uptake by postsynaptic-density enriched fragment and play important roles in synapse. As a special type of synapse, the neuromuscular junction (NMJ) has three different parts: the muscle fiber, the motor neuron axon terminal and the perisynaptic Schwann cells. There are microRNA targeting mRNAs in NMJ and the local translation of the mRNA which contribute to the NMJ formation, maintenance or re-innervation. Interestingly, we noted that a myo specific miRNA, miR-206 has the potential binding sites on neuronal expressing genes’ 3′-untranslated region (3′-UTR). In this perspective review, we assayed the miR-206 and its targeting mRNA expression in muscles and neurons and analyzed the possibility of secreted miRNAs and their potential roles in NMJ.