Figure 3

Synaptic vesicle protein recruitment to axo-dendritic contacts is similar that at induced trans-synaptic signaling sites. (A) Image of an axon transfected with synaptophysin-GFP (green) contacting somato-dendritic region from an adjacent cell transfected with RFP (magenta). White box corresponds to contact region represented by kymograph in (B). (B, C) Kymographs of STVs (green) in axons that contact RFP-expressing dendrites from different neurons (red). Boxes, as seen in induced axo-dendritic contacts, synaptophysin-GFP levels are variable at individual stable sites in neuron-neuron contacts over the course of hours and minutes (asterisks). t = time after imaging begins; scale bars (A) = 10 μm, (B, C) = 5 μm. (D) Histogram of net changes in the densities of individual stable recruitment sites from one short imaging sequence to the next for neuron-neuron contacts. The number of stable sites of recruitment fluctuated between the majority of imaging sequences (corresponds to all non-zero bins), with a small bias toward addition of stable sites of recruitment.