Mutant dynamin proteins induce abnormal comet movements. Rat
fibroblasts coexpressing Myc-PIP5KIα and wild-type or mutant forms of
Dyn2-GFP were imaged for 100 frames, and the movement of comet
structures was followed. (a) Cells expressing wild-type
Dyn2-GFP formed numerous comets (arrows and Inset) that
actively incorporated the tagged Dyn2 (see Movie 3).
(a′) One hundred frames from the time-lapse images were
stacked to show the movement characteristics of individual comets. Each
color represents a distinct comet path. Note the linear quality of
comet movement. Arrows, multiple comets appeared to form from a single
domain. (b) A K44A-GFP-expressing cell with comets
(arrows). The comets are fewer and much smaller than those of wild type
(see Movie 4). (b′) One hundred stacked frames from the
K44A-GFP time-lapse. These comets often had curved and wandering paths
(arrows) and were less efficient in their translocation. See the
Dyn2K44a-GFP video (Movie 4, arrow on right) for an example of
defective movement. (c) Comets in cells expressing the
truncated Dyn2ΔPRD-GFP are dark and do not incorporate the mutant
protein (see Movie 5). (c′) One hundred frames from the
ΔPRD-GFP video revealed that these comets moved in a similar manner
to those of wild-type Dyn2, with smooth curvilinear paths. (Bars, 10
μm.)