Figure 5.

Syntabulin loss of function impairs the assembly of functional presynaptic boutons. A, Representative presynaptic terminals loaded with FM4-64 were unloaded in the presence of 50 mm KCl for 2 min. The subtracted image, the FM4-64-labeled puncta subtracted by the signal left after unloading, represents an activity-dependent uptake of FM dye at presynaptic boutons. B, Reduced FM4-64 uptake in neurons after syntabulin loss of function. Axon terminals at DIV9–DIV11 were loaded with FM4-64 (red) 4–6 d after transfection with con-siRNA or STB-siRNA (green), or 2 d after transfection with GFP, or GFP-KBD (green). C, Quantitative measurement of FM4-64 puncta. The fluorescent images were collected from 17–18 neurons from three separate coverslips for each DNA construct. Total axon length measured was 3379.85 μm (con-siRNA), 3350.12 μm (STB-siRNA), 3444.71 μm (GFP), 3679.06 μm (GFP-KBD), or 3946.01 μm (GFP-SBD). Error bars indicate SEM (**p < 0.001, relative to control siRNA or GFP by Student's t test, respectively). Scale bars, 10 μm.