Figure 4. PINK1 deficient cells have fewer mitochondrial fusion events.

(A) Control shRNA (upper panels) or PINK1 shRNA (lower panels) cells were transfected with a mitochondrially directed, photoactivatable GFP which was then photoactivated within a small region of interest (see Materials and Methods). Sequential images of the single cells (0, 15, 30, 45 and 60 minutes as indicated above the images) after photoactivation are shown. When cells are fusion-competent, decreases in fluorescence are seen over time in the region of photoactivation. Note that the fluorescence intensity is equal across the cell in the control line in the upper panel by 30 minutes, whereas the PINK1 deficient cell retains areas of higher intensity, indicating decreased fusion. Each scale bar is 5 µm and applies to all fluorescence micrograph in that series. (B) Quantification of experiments as in A (N = 3 experiments, with n = 9–10 cells measured per time point per experiment) shows the loss of fluorescence over time for parental M17 cells (black triangles), control shRNA (blue circles) or PINK1 shRNA (pink squares) cell lines. The difference between cell lines was significant by two-way ANOVA (P<0.001), as was the effect of time (P<0.001). Bonferonni post-hoc tests were used to compared PINK1shRNA lines to the control shRNA lines *P<0.05; ** P<0.01; ***P<0.001. Error bars indicate the SEM between experiments.