Figure 1.

CMT2A-associated MFN2 mutants alter the transport of axonal mitochondria. Mitochondria in cultured DRG neurons expressing wtMFN2 or R94Q were labeled with mito-RFP and imaged by time-lapse microscopy. A, Kymograph analysis of mitochondrial movements in R94Q-expressing cells reveal diminished numbers of moving mitochondria. B, Mitochondria from R94Q-expressing neurons spent more time paused between anterograde and retrograde movements than did mitochondria from controls. (*p < 0.005, t test; n = number of axons from which image stacks were created). Each condition contained a total of at least 500 observed mitochondria. C, Velocity distributions representing the amount of time that mitochondria from wtMFN2- or R94Q-expressing neurons spent moving at indicated velocities. Anterograde velocities are above the x-axis, and retrograde velocities are below the x-axis. There was a shift in both the anterograde and retrograde velocity distributions of mitochondria from R94Q-expressing neurons toward slower velocities. The differences were statistically significant as determined by rank-sum test analysis (p < 0.001). D, Size–frequency distributions of axonal mitochondria from wtMFN2-, R94Q-, and H361Y-expressing cells show that CMT2A disease mutants decrease mitochondrial lengths.