Real-time visualization of structural dynamics of synapses in live cells in vivo

Abstract

The structural plasticity of synapses is a fundamental mechanism regulating brain functions. However, currently available methods, based on split fluorescent proteins (FPs), have been limited in assessing synaptic dynamics in vivo due to the irreversible binding of split FPs. Here, we develop ‘SynapShot’—a method for visualizing the structural dynamics of intact synapses by combining dimerization-dependent fluorescent proteins (ddFPs) with engineered synaptic adhesion molecules. SynapShot allows real-time monitoring of reversible and bi-directional changes of synaptic contacts under physiological stimulation. The application of green and red ddFPs in SynapShot enables the simultaneous visualization of two distinct populations of synapses. Notably, the red-shifted SynapShot is highly compatible with blue light-based optogenetic techniques, allowing for the visualization of synaptic dynamics while precisely controlling specific signaling pathways. Furthermore, we demonstrate that SynapShot enables real-time monitoring of structural changes in synaptic contacts in the mouse brain during both primitive and higher-order behaviors.