Figure 8.

Similar distributions of synaptic vesicles and release sites between animals overexpressing wild-type and Ca²⁺-binding defective Syt1. A, Electron micrographs are shown for larvae overexpressing the wild-type (C2A-C2B, top) or Ca²⁺-binding defective (C2A*-C2B*, bottom) Syt1 constructs. Detailed view near a single active zone is shown on the right panels. Scale bar, 100 nm. B, Mean number of synaptic vesicles at varying distances from active zones is shown for larvae overexpressing the wild-type or Ca²⁺-binding defective Syt1 constructs. Number of active zones analyzed (C2A-C2B and C2A*-C2B*): 13 and 25 at 50 nm; 19 and 32 at 100–200 nm; 15 and 16 for total number of synaptic vesicles. C, Representative confocal images depicting distributions of release sites (active zones) in muscle 6/7 NMJs are shown for larvae overexpressing wild-type or Ca²⁺-binding defective Syt1. Active zones are identified by immunoreactivity against Brp (top panels, green). The overall structure of NMJs is detected with HRP immunoreactivity (middle panels, red). The merged images of Brp and HRP channels are shown in the bottom panels. Scale bar, 20 μm. D, The mean number of active zones per NMJ is summarized for larvae containing each transgenic construct without a GAL4 driver (white, control) and those with transgenic constructs driven by elav^C155-GAL4 (gray). Number of NMJs examined (control and transgene expression): 12 and 11 for C2A-C2B; 11 and 10 for C2A*-C2B*. B, D, Data are mean ± SEM.