FMR1 and fragile X syndrome: Finally, the malleable NMJ provides a large and genetically tractable glutamatergic synapse model, which continues to be instrumental in the discovery and elucidation of FMRP synaptic requirements, including intracellular signaling, intercellular interactions, and trans-synaptic pathways that strongly contribute to the FXS disease state (Dear et al., 2017).