Rapid and reversible optogenetic silencing of synaptic transmission by clustering of synaptic vesicles

Acutely silencing specific neurons informs about their functional roles in circuits and behavior. Existing optogenetic silencers include ion pumps, channels, metabotropic receptors, and tools that damage the neurotransmitter release machinery. While the former hyperpolarize the cell, alter ionic gradients or cellular biochemistry, the latter allow only slow recovery, requiring de novo synthesis. Thus, tools combining fast activation and reversibility are needed. Here, we use light-evoked homo-oligomerization of cryptochrome CRY2 to silence synaptic transmission, by clustering synaptic vesicles (SVs). We benchmark this tool, optoSynC, in Caenorhabditis elegans, zebrafish, and murine hippocampal neurons. optoSynC clusters SVs, observable by electron microscopy. Locomotion silencing occurs with tau(on) similar to 7.2s and recovers with tau(off) similar to 6.5min after light-off. optoSynC can inhibit exocytosis for several hours, at very low light intensities, does not affect ion currents, biochemistry or synaptic proteins, and may further allow manipulating different SV pools and the transfer of SVs between them.

Automated summary

This study utilizes the light-evoked homo-oligomerization of CRY2 to silence synaptic transmission by clustering synaptic vesicles, providing a tool for acute silencing of specific neurons. The optoSynC tool demonstrates fast activation and reversibility, inhibiting exocytosis for hours at low light intensities without affecting ion currents or synaptic proteins. It has the potential for manipulating different synaptic vesicle pools and their transfer.