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Figure 1 | Neural Development

Figure 1

From: Dynamic mechanisms of neuroligin-dependent presynaptic terminal assembly in living cortical neurons

Figure 1

Levels of synaptic vesicle protein enrichment at individual trans-synaptic adhesion sites are modulated throughout recruitment. (A) Images from live, long-term, time-lapse confocal imaging of an axon expressing synaptophysin-GFP (green) and contacting an HEK293 cell (magenta and white outline) that expresses neuroligin-1 + HcRed. The top panel shows an axon and HEK293 cell at one hour after contact. In this panel, synaptophysin-GFP at the contact site appears white in the overlay. The remaining panels show only synaptophysin fluorescence for clarity. Images were collected 1 hour, 12.5 hours and 20 hours after contact was induced (scale bar = 5 μm). (B) Time course of STV enrichment in axonal regions that contact neuroligin-1-expressing cells. Enrichment corresponds to the difference between the total STV integrated density within the contact region and outside of the contact, normalized to the total STV integrated density throughout the axon and expressed as a percentage. Positive values indicate enrichment inside the contact area. Individual points (cyan) represent mean values from 45 images collected at 10 second intervals, beginning at the time indicated on the x-axis. Dashed line, overall mean at each time point (n = 12 contacts). Overall, enrichment increased gradually over the first ten hours then remained elevated. Error bars = SEM. (C) Over the same time course, STVs were not enriched at sites of contact between axons and HEK293 cells expressing HcRed but no neuroligin. (D) Integrated density of synaptophysin-GFP inside (solid line) and outside (dashed line) of contacts over time. Red bar, rising phase of enrichment (2 to 7.5 hours after contact). Synaptophysin increased at contacts while remaining stable outside contacts. (E) Enrichment for two axons. At individual contacts, enrichment was highly dynamic throughout the imaging period. Therefore, although STV enrichment increases at trans-synaptic adhesion sites overall, enrichment levels for individual axons vary throughout the first 24 hours of development.

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