The formation of synaptic connections is a complex process involving the coordinated assembly of both pre- and post-synaptic compartments. Many evolutionarily conserved signaling pathways and gene networks have been shown to regulate synapse formation.  As recently described in Development, the Van Vactor Lab reported that the microRNA miR-8 modulates synapse structure by directly repressing the actin regulator Enabled (Ena) at the Drosophila neuromuscular junction (NMJ).  Localization to the area surrounding pre-synaptic boutons requires conserved motifs in the C-terminal actin-assembly domain of Ena-family proteins. Additional studies indicate that miR-8 controls NMJ architecture by inhibiting Ena expression in muscle and thus limiting post-synaptic actin assembly that would otherwise restrict the expansion of motor neuron terminals. This novel regulatory process coordinates the remodeling of pre- and post-synaptic compartments in NMJ morphogenesis.

Figure: Endogenous Ena (green) accumulates in the peribouton compartment with post-synaptic marker protein Discs large (red).