Axonal and presynaptic FMRP: Localization, signal, and functional implications

·Fragile X mental retardation protein (FMRP) binds a selected set of mRNAs and proteins to guide neural circuit assembly and regulate synaptic plasticity.·Loss of FMRP is responsible for Fragile X syndrome, a neuropsychiatric disorder characterized with auditory processing problems and social difficulty.·FMRP actions in synaptic formation, maturation, and plasticity are site-specific among the four compartments of a synapse: presynaptic and postsynaptic neurons, astrocytes, and extracellular matrix.·This review summarizes advancements in understanding FMRP localization, signals, and functional roles in axons and presynaptic terminals, and discussed the axonal FMRP in auditory function and disease.