(A, C, E, G and I) Example transmission electron micrographs showing endocytic pits and ferritin-containing endocytic structures at the indicated time points in neurons expressing scramble RNA (A), Syndapin 1 shRNA (C), Syndapin 1 shRNA and wild-type Syndapin 1 overexpression (Syndapin 1 wt OEx) (E), Syndapin 1 shRNA and Syndapin 1 I122D/M123E (Syndapin 1 ID/ME OEx) (G), Syndapin 1 shRNA and Syndapin 1 P434L (Syndapin 1 P434L OEx) (I). In all cases, Syndapin 1 is rendered shRNA-resistant. Black arrowheads, endocytic invaginations; black arrows, ferritin-positive large endocytic vesicles (LEVs) or endosomes; white arrowheads, ferritin-positive synaptic vesicles. Scale bar: 100 nm. PSD, post-synaptic density.
(B, D, F, H and J) Plots showing the increase in the number of each endocytic structure per synaptic profile after a single stimulus in neurons with the indicated genotypes.
(K) Number of endocytic invaginations at 1s after stimulation. The numbers are re-plotted from the 1 s time point in (B, D, F, H, and J).
(L) Number of ferritin-positive LEVs and endosomes at 1s after stimulation. The mean and SEM are shown. The numbers of LEVs and endosomes are summed from the data in (B, D, F, H, and J) and averaged.
(M and N) Plots showing the width (M) and depth (N) of endocytic pits at the 1s time point. The median and 95% confidence interval are shown in each graph.
*p < 0.05. See Data S1 for the n values, statistical test, and detailed numbers.