Small vesicle endocytic hot-spots triggered by filopodial contact. (A) Time-lapse confocal images of FM 5-95 internalization show contact and apparent fusion between adjacent filopodia (red arrows). The boxed area is magnified in the panels at the right and the time after the initial membrane labeling (minutes:seconds) is indicated in each frame. The dashed arrows (white) are static and indicate the initial position of filopodia. Filopodial contact and fusion is accompanied by the formation of multiple small endocytic vesicles at the proximal region of the resulting filopodium (yellow arrowheads). See Additional file 6 for the corresponding time-lapse movie. (B) Time-lapse DIC images show similar filopodial-filopodial contacts (red arrows) as in (A). The dashed arrows (white) depict the initial filopodial position. The corresponding time-lapse movie is shown in Additional file 7. Scale bars, 5 μm (left), 1 μm (right).