(C and D) Endogenous kaptin immunostained together with the presynaptic marker bassoon at DIV14 (C) and with the postsynaptic marker Shank2 at DIV24 (D). Puncta enriched with anti-kaptin immunoreactivity (marked by arrow heads) were rich in F-actin, as shown by fluorescently labeled phalloidin. (C) Furthermore, they were usually contacted by presynapses. The scale bar represents 5 μm. (D) Postsynapses marked by Shank2 were largely positive for both F-actin and anti-kaptin immunolabeling (arrow heads). For clarity, the anti-F-actin staining was omitted from the merged image in (D). High-magnification images are shown. The scale bar represents 2.5 μm.