Activity-dependent nucleation of dynamic microtubules at presynaptic boutons is required for neurotransmission

Control of microtubule (MT) dynamics is critical for neuronal function. Whether MT nucleation is regulated at presynaptic boutons and influences overall presynaptic activity remains unknown. By visualizing MT dynamics at individual excitatory en passant boutons in axons of hippocampal neurons we found that MTs preferentially grow from presynaptic boutons as a result of g-tubulin and augmin-dependent nucleation. MT nucleation at boutons is promoted by neuronal activity, functionally coupled to synaptic vesicle (SV) transport, and required for neurotransmission. Hence, en passant boutons act as hotspots for activity- dependent MT nucleation, which is required for neurotransmission by providing the tracks for a rate-limiting supply of SVs to sites of neurotransmitter release.