Miniature Neurotransmission Regulates Drosophila Synaptic Structural Maturation

Summary

Miniature neurotransmission is the transsynaptic process where single synaptic vesicles spontaneously released from presynaptic neurons induce miniature postsynaptic potentials. Since their discovery over 60 years ago, miniature events have been found at every chemical synapse studied. However, the in vivo necessity for these small-amplitude events has remained enigmatic. Here, we show that miniature neurotransmission is required for the normal structural maturation of Drosophila glutamatergic synapses in a developmental role that is not shared by evoked neurotransmission. Conversely, we find that increasing miniature events is sufficient to induce synaptic terminal growth. We show that miniature neurotransmission acts locally at terminals to regulate synapse maturation via a Trio guanine nucleotide exchange factor (GEF) and Rac1 GTPase molecular signaling pathway. Our results establish that miniature neurotransmission, a universal but often-overlooked feature of synapses, has unique and essential functions in vivo.

Highlights

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  Miniature, but not evoked, neurotransmission is required for synapse development

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  Miniature neurotransmission bidirectionally regulates synaptic terminal maturation

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  Miniature events signal locally through the GEF Trio and the GTPase Rac1

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  Miniature neurotransmission has unique and essential functions in vivo

Abstract

Miniature events (or “minis”) are a universal feature of all chemical synapses, but their function in vivo has remained enigmatic. Here, Choi et al. show that miniature neurotransmission is essential for synaptic terminal maturation in a role not shared by evoked neurotransmission.